Method and system for treating lime to form vaterites

Abstract

To provide a method and system for forming calcium carbonate containing vaterite. [Solution] This method comprises the step of dissolving lime in an aqueous solution of a base under one or more precipitation conditions to produce a precipitate containing vaterite and calcium carbonate and a supernatant solution. In some embodiments of the above-described aspects, calcination is carried out in a shaft kiln, rotary furnace, or electric furnace. In some embodiments of the above-described aspects and embodiments, the lime is incompletely combusted lime, lightly calcined quicklime, dead lime, or a combination thereof.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims the interests of U.S. Provisional Application No. 62 / 981,266, filed on 25 February 2020, which is incorporated herein by reference in its entirety. [Background technology]

[0002] background Carbon dioxide (CO2) emissions have been identified as a major contributor to global warming. CO2 is a byproduct of combustion and causes operational, economic, and environmental problems. Increased concentrations of CO2 and other greenhouse gases in the atmosphere are predicted to further promote heat storage in the atmosphere, potentially leading to rising surface temperatures and rapid climate change. Furthermore, rising atmospheric CO2 levels may further acidify the world's oceans due to the dissolution of CO2 and the formation of carbonic acid. The effects of climate change and ocean acidification, if not addressed in a timely manner, are likely to become more economically costly and environmentally harmful. Reducing the potential risks of climate change requires the sequestration and avoidance of CO2 from various anthropogenic processes. [Overview of the Initiative] [Means for solving the problem]

[0003] overview In one embodiment, a method for forming calcium carbonate containing vaterite, (i) A step of calcining limestone to form a gas stream containing lime and carbon dioxide, (ii) Dissolving lime in an aqueous solution of an N-containing inorganic salt under one or more dissolution conditions to produce a first aqueous solution containing a calcium salt and a gas stream containing ammonia, (iii) Recovering a gas stream containing carbon dioxide and a gas stream containing ammonia, subjecting the gas streams to a cooling process under one or more cooling conditions to condense a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, or a combination thereof; (iv) Treating a first aqueous solution containing a calcium salt with a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, or a combination thereof under one or more precipitation conditions to form a precipitate material containing calcium carbonate and including baterlite and a supernatant solution; A method is provided that includes the above.

[0004] In some embodiments of the foregoing aspects, the firing is performed in a shaft kiln, a rotary furnace, or an electric furnace.

[0005] In some embodiments of the foregoing aspects and embodiments, the lime is unslaked lime, lightly burned quicklime, dead burned lime, or a combination thereof.

[0006] In some embodiments of the foregoing aspects and embodiments, the N-containing inorganic salt is selected from the group consisting of ammonium halides, ammonium sulfate, ammonium sulfite, ammonium nitrate, ammonium nitrite, and combinations thereof. In some embodiments of the foregoing aspects and embodiments, the ammonium halide is ammonium chloride.

[0007] In some embodiments of the foregoing aspects and embodiments, the first aqueous solution further includes ammonia and / or an N-containing inorganic salt.

[0008] In some embodiments of the foregoing aspects and embodiments, the molar ratio of N-containing inorganic salt:lime is between about 0.5:1 and 2:1.

[0009] In the embodiments described above and in some embodiments of the embodiments, one or more dissolution conditions are selected from the group consisting of a temperature between about 30 and 200°C, a pressure between about 0.1 and 10 atm, a wt% of N-containing salt in water between about 0.5 and 50%, and combinations thereof.

[0010] In the aforementioned embodiments and some of the embodiments, no external sources of carbon dioxide and / or ammonia are used, and the process is a closed-loop process.

[0011] In the aforementioned embodiments and some embodiments of the model, the gas stream containing ammonia further contains water vapor.

[0012] In the aforementioned embodiments and some embodiments of the model, the gas stream further contains water vapor between approximately 20% and 90%.

[0013] In the aforementioned embodiments and some of the embodiments, no external water is added to the cooling process.

[0014] In the embodiments described above and in some embodiments of the embodiments, one or more cooling conditions include a temperature between about 0 and 100°C, a pressure between about 0.5 and 50 atm, a pH of the aqueous solution between about 8 and 12, a CO2 flow rate between about 0.1:1 and 20:1, or a combination thereof.

[0015] In the aforementioned embodiments and some embodiments of the model, the second aqueous solution further comprises ammonium carbamate.

[0016] In the aforementioned embodiments and some embodiments of the model, the second aqueous solution is formed by gas condensation.

[0017] In the embodiments described above and in some embodiments of the embodiments, one or more precipitation conditions are selected from the group consisting of a pH of the first aqueous solution between 7 and 9, a temperature of the solution between 20 and 60°C, a residence time between 5 and 60 minutes, or a combination thereof.

[0018] In the embodiments described above and in some embodiments of the embodiments, the first aqueous solution further comprises a solid.

[0019] In some embodiments of the aforementioned aspects and embodiments, the method further includes a step of separating a solid from the first aqueous solution by filtration and / or centrifugation prior to the processing step.

[0020] In the aforementioned embodiments and some embodiments of the model, the separated solid is added to the precipitate as a filler.

[0021] In the embodiments described above and in some embodiments of the embodiments, if the N-containing inorganic salt is ammonium halide, the separated solid further contains residual ammonium halide.

[0022] In some embodiments of the aforementioned aspects and embodiments, the method further includes a step of recovering residual ammonium halide from a solid using a recovery process selected from the group consisting of rinsing, pyrolysis, pH adjustment, and combinations thereof.

[0023] In some embodiments of the aforementioned aspects and embodiments, the solid is not separated from the first aqueous solution, and the first aqueous solution is subjected to a processing step to produce a precipitate further containing the solid. In some embodiments of the aforementioned aspects and embodiments, the solid includes silicates, iron oxides, alumina, or a combination thereof. In some embodiments of the aforementioned aspects and embodiments, the solid is present in the aqueous solution, the precipitate, or a combination thereof in an amount between 1 and 40 wt%.

[0024] In some embodiments of the aforementioned aspects and embodiments, the method further includes the step of dehydrating the precipitate to separate it from the supernatant solution.

[0025] In the aforementioned embodiments and some embodiments of the model, the precipitate and supernatant solution contain residual nitrogen-containing inorganic salts.

[0026] In the embodiments described above and in some embodiments of the embodiments, the residual N-containing inorganic salt includes ammonium halides, ammonium sulfate, ammonium sulfite, ammonium hydrogen sulfide, ammonium thiosulfate, ammonium nitrate, ammonium nitrite, or a combination thereof.

[0027] In the embodiments described above and in some embodiments of the model, the method further includes the steps of removing ammonia and / or N-containing inorganic salts from residual N-containing inorganic salts and recovering them if necessary, removing residual N-containing inorganic salts from the supernatant aqueous solution and recovering them if necessary, and / or removing residual N-containing inorganic salts from the precipitate and recovering them if necessary.

[0028] In some embodiments of the aforementioned aspects and embodiments, the method further includes the step of recovering residual nitrogen-containing inorganic salts from the supernatant aqueous solution using a recovery process selected from the group consisting of pyrolysis, pH adjustment, reverse osmosis, multi-stage flash, multiple-effect distillation, vapor recompression, distillation, and combinations thereof.

[0029] In the aforementioned embodiments and some embodiments of the model, the step of removing residual nitrogen-containing inorganic salts from the precipitate and recovering them if necessary includes heating the precipitate between approximately 300 and 360°C to evaporate the nitrogen-containing inorganic salts from the precipitate and recovering the nitrogen-containing inorganic salts by condensation if necessary.

[0030] In the aforementioned embodiments and some embodiments of the model, the N-containing inorganic salt is ammonium chloride that evaporates from the precipitate, in a form including ammonia gas, hydrogen chloride gas, chlorine gas, or a combination thereof.

[0031] In some embodiments of the aforementioned aspects and embodiments, the method further includes the step of recirculating the recovered residual ammonia and / or N-containing inorganic salts to the dissolution step and / or processing step of the process.

[0032] In the embodiments described above and in some embodiments of the embodiments, the vaterite is either a stable vaterite or a reactive vaterite.

[0033] In the aforementioned embodiments and some embodiments of the model, the method further includes the step of adding water to a precipitate containing reactive vaterite to convert the vaterite into aragonite, which then sets and hardens to form cement or a cement product.

[0034] In the aforementioned embodiments and some embodiments of the set, the cement product is a formed building material selected from masonry units, building panels, conduits, basins, beams, columns, slabs, sound barriers, thermal insulation materials, and combinations thereof.

[0035] In the aforementioned embodiments and some embodiments of the model, the method further includes the step of adding water to a precipitate containing reactive vaterite to convert the vaterite into aragonite, which then sets and hardens to form a non-cement product.

[0036] In one embodiment, a product formed by the method according to the above-described embodiment is provided.

[0037] In one embodiment, a system for forming calcium carbonate containing vaterite, (i) A calcination reactor configured to calcine limestone to form a gas stream containing lime and carbon dioxide, (ii) A dissolution reactor configured to dissolve lime in an aqueous solution of an N-containing inorganic salt under one or more dissolution conditions to produce a first aqueous solution containing a calcium salt and a gas stream containing ammonia, (iii) A cooling reactor configured to recover a gas stream containing carbon dioxide and a gas stream containing ammonia, and to subject the gas streams to a cooling process under one or more cooling conditions to condense a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, or a combination thereof, and (iv) A processing reactor configured to treat a first aqueous solution containing a calcium salt with a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, or a combination thereof, under one or more precipitation conditions, to form a precipitate containing calcium carbonate and vaterite and a supernatant solution. A system including this is provided.

[0038] In some embodiments of the aforementioned features, the dissolution reactor is integrated with the cooling reactor. In embodiments of the present invention, for example, the following items are provided. (Item 1) A method for forming calcium carbonate containing vaterite, (i) A step of calcining limestone to form a gas stream containing lime and carbon dioxide, (ii) Dissolving the lime in an aqueous solution of an inorganic salt containing N under one or more dissolution conditions to produce a first aqueous solution containing a calcium salt and a gas stream containing ammonia, (iii) recovering the gas stream containing carbon dioxide and the gas stream containing ammonia, and subjecting the gas stream to a cooling process under one or more cooling conditions to condense a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, or a combination thereof; (iv) The first aqueous solution containing the calcium salt is treated with a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, or a combination thereof under one or more precipitation conditions to form a precipitate containing calcium carbonate containing vaterite and a supernatant solution. Methods that include... (Item 2) The method according to item 1, wherein the firing is carried out in a shaft kiln, rotary furnace, or electric furnace. (Item 3) The method according to item 1 or 2, wherein the lime is incompletely combusted lime, lightly calcined quicklime, dead lime, or a combination thereof. (Item 4) The method according to any one of the above items, wherein the N-containing inorganic salt is selected from the group consisting of ammonium halides, ammonium sulfate, ammonium sulfite, ammonium nitrate, ammonium nitrite, and combinations thereof. (Item 5) The method according to item 4, wherein the ammonium halide is ammonium chloride. (Item 6) The method according to any one of the above items, wherein the first aqueous solution further comprises ammonia and / or an N-containing inorganic salt. (Item 7) The method according to any one of the above items, wherein the molar ratio of the N-containing inorganic salt to lime is between approximately 0.5:1 and 2:1. (Item 8) The method according to any one of the above items, wherein the one or more dissolution conditions are selected from the group consisting of a temperature between about 30 and 200°C, a pressure between about 0.1 and 10 atm, a wt% of N-containing salt in water between about 0.5 and 50%, and combinations thereof. (Item 9) The method according to any one of the above items, wherein no external source of carbon dioxide and / or ammonia is used, and the process is a closed-loop process. (Item 10) The method according to any one of the above items, wherein the gas stream containing ammonia further contains water vapor. (Item 11) The method according to item 10, wherein the gas stream further contains water vapor between approximately 20% and 90%. (Item 12) The method according to any one of the above items, wherein no water is added to the cooling process from an external source. (Item 13) The method according to any one of the above items, wherein the one or more cooling conditions include a temperature between about 0 and 100°C, a pressure between about 0.5 and 50 atm, a pH of the aqueous solution between about 8 and 12, a flow rate of CO2, a CO2:NH3 ratio between about 0.1:1 and 20:1, or a combination thereof. (Item 14) The method according to any one of the above items, wherein the second aqueous solution further comprises ammonium carbamate. (Item 15) The method according to any one of the above items, wherein the second aqueous solution is formed by the condensation of the gas. (Item 16) The method according to any one of the above items, wherein the one or more precipitation conditions are selected from the group consisting of the pH of the first aqueous solution between 7 and 9, the temperature of the solution between 20 and 60°C, the residence time between 5 and 60 minutes, or a combination thereof. (Item 17) The method according to any one of the above items, wherein the first aqueous solution further comprises a solid. (Item 18) The method according to item 17, further comprising the step of separating the solid from the first aqueous solution by filtration and / or centrifugation prior to the processing step. (Item 19) The method according to item 18, wherein the separated solid is added to the precipitate as a filler. (Item 20) The method according to item 18 or 19, wherein the N-containing inorganic salt is the ammonium halide, and the separated solid further comprises residual ammonium halide. (Item 21) The method according to item 20, further comprising the step of recovering the residual ammonium halide from the solid using a recovery process selected from the group consisting of rinsing, thermal decomposition, pH adjustment, and combinations thereof. (Item 22) The method according to item 17, wherein the solid is not separated from the first aqueous solution, and the first aqueous solution is subjected to the processing step to produce a precipitate further containing the solid. (Item 23) The method according to any one of items 17 to 22, wherein the solid comprises a silicate, iron oxide, alumina, or a combination thereof. (Item 24) The method according to any one of items 17 to 23, wherein the solid is present in the aqueous solution, the precipitate, or a combination thereof in an amount between 1 and 40 wt%. (Item 25) The method according to any one of the above items, further comprising the step of dehydrating the precipitate to separate the precipitate from the supernatant solution. (Item 26) The method according to any one of the above items, wherein the precipitate and the supernatant solution contain a residual nitrogen-containing inorganic salt. (Item 27) The method according to item 26, wherein the residual N-containing inorganic salt includes ammonium halide, ammonium sulfate, ammonium sulfite, ammonium hydrogen sulfide, ammonium thiosulfate, ammonium nitrate, ammonium nitrite, or a combination thereof. (Item 28) The method according to item 26 or 27, further comprising the steps of removing ammonia and / or N-containing inorganic salts from the residual N-containing inorganic salt and recovering them if necessary, removing the residual N-containing inorganic salts from the supernatant aqueous solution and recovering them if necessary, and / or removing the residual N-containing inorganic salts from the precipitate and recovering them if necessary. (Item 29) The method according to item 28, further comprising the step of recovering the residual nitrogen-containing inorganic salt from the supernatant aqueous solution using a recovery process selected from the group consisting of pyrolysis, pH adjustment, reverse osmosis, multi-stage flash, multiple-effect distillation, vapor recompression, distillation, and combinations thereof. (Item 30) The method according to item 28, wherein the step of removing the residual N-containing inorganic salt from the precipitate and recovering it if necessary includes heating the precipitate between approximately 300 and 360°C to evaporate the N-containing inorganic salt from the precipitate and recovering the N-containing inorganic salt by condensation if necessary. (Item 31) The N-containing inorganic salt is ammonia gas, hydrogen chloride gas, chlorine gas, or a combination thereof. The method according to item 30, wherein ammonium chloride evaporates from the precipitate in a form containing se. (Item 32) The method according to any one of items 28 to 31, further comprising the step of recirculating the recovered residual ammonia and / or N-containing inorganic salt to the dissolution step and / or processing step of the process. (Item 33) The method according to any one of the above items, wherein the vaterite is a stable vaterite or a reactive vaterite. (Item 34) The method according to item 33, further comprising the step of adding water to the precipitate containing reactive vaterite to convert the vaterite into aragonite, the aragonite setting and hardening to form cement or a cement product. (Item 35) The method according to item 34, wherein the cement product is a formed building material selected from masonry units, building panels, conduits, water basins, beams, columns, slabs, sound barriers, thermal insulation materials, and combinations thereof. (Item 36) The method according to item 33, further comprising the step of adding water to the precipitate containing reactive vaterite to convert the vaterite into aragonite, the aragonite setting and hardening to form a non-cement product. (Item 37) A product formed by the method described in any one of the above items. (Item 38) A system for forming calcium carbonate containing vaterite, (i) A calcination reactor configured to calcine limestone to form a gas stream containing lime and carbon dioxide, (ii) A dissolution reactor configured to dissolve the lime in an aqueous solution of an N-containing inorganic salt under one or more dissolution conditions to produce a first aqueous solution containing a calcium salt and a gas stream containing ammonia, (iii) A cooling reactor configured to recover the gas stream containing carbon dioxide and the gas stream containing ammonia, and to subject the gas stream to a cooling process under one or more cooling conditions to condense a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, or a combination thereof, and (iv) A processing reactor configured to treat a first aqueous solution containing the calcium salt with a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, or a combination thereof, under one or more precipitation conditions, to form a precipitate containing calcium carbonate containing vaterite and a supernatant solution. A system that includes this. (Item 39) The system according to item 38, wherein the dissolution reactor is integrated with the cooling reactor.

[0039] The features of the present invention are specifically described using the appended claims. The features and advantages of the present invention will be better understood by referring to the following detailed description, which describes exemplary embodiments in which the principles of the present invention are utilized, and to the following appended figures. [Brief explanation of the drawing]

[0040] [Figure 1] Figure 1 shows some embodiments of the methods and systems provided herein.

[0041] [Figure 2] Figure 2 shows some embodiments of the methods and systems provided herein.

[0042] [Figure 3] Figure 3 shows some embodiments of the methods and systems provided herein.

[0043] [Figure 4] Figure 4 shows some embodiments of methods and systems including an integrated reactor provided herein.

[0044] [Figure 5] Figure 5 shows some embodiments of methods and systems including an integrated reactor provided herein.

[0045] [Figure 6] Figure 6 shows some embodiments of methods and systems including an integrated reactor provided herein.

[0046] [Figure 7] Figure 7 shows some embodiments of methods and systems including an integrated reactor provided herein.

[0047] [Figure 8] Figure 8 shows the Gibbs free energy diagram for the transition from vaterite to aragonite.

[0048] [Figure 9] Figure 9 shows the effect of the CO2:NH3 ratio and the ratio of condensed products during formation in a cooling reactor, as described in Example 4 of this specification. [Modes for carrying out the invention]

[0049] explanation This specification provides a unique method and system for using lime to form vaterite polymorphs of calcium carbonate, which can be used to form various products described herein. Lime is obtained from the calcination of limestone. The applicants have invented a unique method and system for using lime to form useful cement products. In some embodiments of the method and system provided herein, lime is treated directly with an aqueous solution of a base, for example, an ammonium salt, for example, an aqueous solution of ammonium chloride, to solubilize or dissolve the calcium of the lime in an aqueous solution. The dissolved calcium in the form of a calcium salt is then treated with carbon dioxide gas (generated during the calcination of limestone) to form a precipitate or precipitate containing calcium carbonate, which is partially or completely in vaterite polymorph form.

[0050] In some embodiments, calcium carbonate is formed in vaterite polymorphs, or in some embodiments, calcium carbonate is light calcium carbonate (PCC). PCC may be in the form of vaterite, aragonite, calcite, or a combination thereof. In some embodiments, the vaterite formed by the methods and systems herein is in the form of stable vaterite or reactive vaterite, both of which are described herein. In some embodiments, the precipitate containing reactive vaterite has unique properties, including cementitious properties, by being converted to aragonite which sets and cementifies with high compressive strength, though not limited to these. In some embodiments, the conversion from vaterite to aragonite yields cement that can be used to form building materials and / or cement products, such as formed building materials, such as building panels, which are described herein further, though not limited to these. In some embodiments, the vaterite in the product is stable (does not convert to aragonite) and can be used as a filler or auxiliary cement material (SCM) when mixed with other cements, such as ordinary Portland cement (OPC). Vaterite-containing precipitates can also be used as aggregates in which reactive vaterite-containing precipitates are converted to aragonite after contact with water, which then solidify and cementify, and are subsequently crushed to form aggregates after cementification. In some embodiments in which calcium carbonate is formed as PCC, the PCC material is cementitious or can be used as a filler in products such as paper products, polymer products, lubricants, adhesives, rubber products, chalk, asphalt products, paints, abrasives for paint removal, personal care products, cosmetics, cleaning products, personal hygiene products, edible products, agricultural products, soil conditioners, biocides, environmental remediation products, and combinations thereof. Such uses of calcium carbonate precipitates as fillers in non-cement products are described in U.S. Patent No. 7,829,053 issued November 9, 2010, which is incorporated herein by reference in its entirety.

[0051] The base used to solubilize calcium ions derived from lime, such as, but not limited to, nitrogen-containing inorganic or nitrogen-containing organic salts, such as ammonium salts, may leave residual nitrogen-containing inorganic or nitrogen-containing organic salts in the supernatant and the precipitate itself after the precipitate has formed. In some embodiments, the content of nitrogen-containing inorganic or nitrogen-containing organic salts in the precipitate, such as, but not limited to, ammonium chloride, ammonium sulfate, ammonium sulfite, ammonium hydrogen sulfide, ammonium thiosulfate, ammonium nitrate, ammonium nitrite, or combinations thereof, may be detrimental to the cement product thus formed from the precipitate, and therefore the presence of nitrogen-containing inorganic or nitrogen-containing organic salts in the precipitate may be undesirable. For example, chlorides in the cement product can be corrosive to metal structures used with the cement product. Furthermore, residual ammonia may add an unpleasant odor to the product. Moreover, the wasteful, unrecovered residual nitrogen-containing inorganic or nitrogen-containing organic salts in the precipitate and supernatant may not be economically or environmentally viable. Various methods for removing nitrogen-containing inorganic salts or nitrogen-containing organic salts from supernatants and precipitates, and recovering them as needed, are provided herein.

[0052] Before describing the present invention in detail, it should be understood that the present invention is not limited to the specific embodiments described and is therefore naturally subject to change. It should also be understood that the terms used herein are intended solely to describe specific embodiments and not to limit them.

[0053] Where a range of values ​​is provided, unless otherwise explicitly stated by the circumstances, each value up to one-tenth of the lower limit that lies between the upper and lower limits of that range, and any other described or intervening values ​​within that described range, are understood to be included in the present invention. The upper and lower limits of these smaller ranges may independently be included within those smaller ranges, and these are also included in the present invention, provided that any boundaries in the described range are specifically excluded. Where the described range includes one or both of the boundaries, the range excluding one or both of those included boundaries is also included in the present invention.

[0054] Certain ranges are presented herein with the term “approximately” preceding the numerical value. The term “approximately” is used herein to provide letteric backing for the exact number that follows, and for numbers that are close to or approximate the number that follows. When determining whether a number is close to or approximates a specifically stated number, an unrequited number that is close or approximates may be a number that, in the context in which it is presented, provides a number that is substantially equivalent to the specifically stated number.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention pertains. Any methods and materials similar to or equivalent to those described herein may be used in the practice or testing of the present invention, but representative exemplary methods and materials are described herein.

[0056] All publications, patents, and patent applications referenced herein are incorporated by reference as if each individual publication, patent, or patent application were specifically indicated to be incorporated by reference. Furthermore, each cited publication, patent, or patent application is incorporated by reference to disclose and describe the subject matter of which the publication is cited. Any citation of a publication is intended to disclose them prior to the filing date and should not be construed as an acknowledgment that the invention described herein does not have prior rights to such publication with respect to prior patents. Furthermore, the publication dates provided may differ from the actual publication dates and may need to be independently verified.

[0057] Where used herein and in the appended claims, the singular forms "a," "an," and "the" should be noted to include multiple references unless otherwise indicated by the context. Furthermore, it should be noted that claims may be written to exclude any element as necessary. Thus, this singular form is intended to function as an antecedent for the use of exclusive terms such as "solely" and "only," or for the use of "negative" limitation, relating to the enumeration of elements of the claims.

[0058] As will become apparent to those skilled in the art as they read this disclosure, each of the individual embodiments described and illustrated herein has distinct components and features, which can be readily separated or combined with features of any of several other embodiments without departing from the scope or spirit of the invention. Any method described may be carried out in the order of the events described, or in any other logically possible order. I. Methods and Systems

[0059] Methods and systems are provided for utilizing lime to form a precipitate having a specific polymorph of calcium carbonate, such as vaterite, which has properties useful as a component of certain building materials. The vaterite formed in the methods and systems provided herein may be stable vaterite or reactive vaterite. Reactive vaterite dissolves in water and, upon reprecipitation, forms aragonite having cementitious properties. The vaterite-containing precipitates provided herein, but are not limited to, can be used to replace ordinary Portland cement (OPC) completely or partially as an auxiliary cement material (SCM) in applications such as cement fiber board. When used herein, "lime" refers to calcium oxide and / or calcium hydroxide. The presence and amount of calcium oxide and / or calcium hydroxide in lime should vary depending on the conditions for lime formation.

[0060] The methods and systems provided herein, though not limited to them, have several advantages, including reducing carbon dioxide emissions by reintroducing carbon dioxide into the process to form a calcium carbonate-containing precipitate. The generation of vaterite-containing precipitates in the methods and systems provided herein offers advantages including reduced operating costs due to lower fuel consumption and a reduced carbon footprint.

[0061] Cement contributes significantly to global carbon dioxide emissions, with over 1.5 billion metric tons released annually, representing approximately 5% of total emissions. Over 50% of cement emissions can originate from the release of carbon dioxide from the decomposition of lime raw materials (CaCO3 → CaO + CO2). In the methods and systems provided herein, the release of CO2 resulting from the calcination of limestone to lime can be avoided by recovering it and returning it to the cement vaterite material. By recovering carbon dioxide, the vaterite product has the potential to eliminate the significant amount of carbon dioxide emissions from cement and from any source to the entire global emissions.

[0062] Accordingly, in one embodiment, a method is provided for forming vaterite-containing calcium carbonate, comprising the step of dissolving lime in an aqueous solution of a base under one or more precipitation conditions to produce a precipitate and a supernatant solution containing vaterite-containing calcium carbonate.

[0063] In one embodiment, a method for forming vaterite-containing calcium carbonate is provided, comprising the steps of (i) dissolving lime in a basic aqueous solution under one or more dissolution conditions to produce a first aqueous solution containing a calcium salt, and (ii) treating the first aqueous solution containing the calcium salt with a gas stream containing carbon dioxide under one or more precipitation conditions to form a precipitate containing vaterite-containing calcium carbonate and a supernatant solution. In some embodiments of the above-described embodiment, the gas stream containing carbon dioxide is obtained by calcining limestone to form lime.

[0064] Some aspects and embodiments of the methods and systems provided herein are shown in Figures 1-7. It should be understood that the steps shown in Figures 1-7 can be modified, the order of the steps can be changed, or additional steps can be added or removed depending on the desired results. As shown in Figures 1-7, lime is subjected to the methods and systems provided herein to produce a precipitate containing calcium carbonate and vaterite.

[0065] Calcination or firing is a heat treatment process that results in the thermal decomposition of limestone. “Limestone,” as used herein, means CaCO3 and may further include other impurities typically present in limestone. Limestone is a naturally occurring mineral. The chemical composition of this mineral varies from region to region and can even vary between different deposits within the same region. Therefore, limestone containing calcium oxide and / or calcium hydroxide obtained by calcining limestone from each natural deposit may also vary. Typically, limestone may consist of calcium carbonate (CaCO3), magnesium carbonate (MgCO3), silica (SiO2), alumina (Al2O3), iron (Fe), sulfur (S), or other trace elements.

[0066] Limestone deposits are widely distributed. Limestone from various deposits may have different physicochemical properties and can be classified according to their chemical composition, texture, and geological formation. Limestone can be classified into high-calcium types, where the carbonate content is mainly composed of calcium carbonate and magnesium carbonate content is 5% or less; magnesium types, where magnesium carbonate is present in approximately 5-20% of limestone; or dolomite types, where MgCO3 is present between 20-45% and the remainder is calcium carbonate. Limestone from different sources may differ significantly in chemical composition and physical structure. It should be understood that the methods and systems provided herein apply to all cement plants that calcine limestone from any of the sources listed above or commercially available sources. Quarries include, but are not limited to, quarries associated with cement furnaces, quarries for limestone for aggregates to be used in concrete, quarries for limestone for other purposes (road basements), and / or quarries associated with lime furnaces.

[0067] The calcination of limestone involves a chemical reaction that decomposes the limestone. CaCO3 → CaO + CO2 (gas) This is the decomposition process.

[0068] This step is shown in Figures 1-3 as the first step of calcining limestone to form lime. Depending on the conditions, lime can exist in a dry form, i.e., calcium oxide, and / or a wet form, such as calcium hydroxide. The production of lime can vary depending on the type of furnace, calcination conditions, and the properties of the raw materials, i.e., limestone. At relatively low calcination temperatures, the product formed in the furnace may contain both unburned carbonates and lime, and is sometimes called incompletely combusted lime. As the temperature rises, lightly calcined quicklime or highly reactive lime may be produced. At even higher temperatures, dead calcined lime or low reactive lime may be produced. Lightly calcined quicklime is produced when the reaction front reaches the core of the packed limestone and converts all present carbonates into lime. Highly productive products may be relatively soft, contain small lime microcrystals, and have an open porous structure with an easily valuable interior. Such lime can have optimal properties of high reactivity, high surface area, and low bulk density. Beyond this stage, increasing the degree of calcination can cause the lime microcrystals to grow into larger aggregates and sintered materials. This can reduce surface area, porosity, and reactivity, and increase bulk density. This product may be known as dead-calcined lime or low-reactivity lime. Without adhering to any particular theory, the methods and systems provided herein utilize one or a combination of the aforementioned limes. Thus, in some embodiments, the lime is dead-calcined, scorched, incompletely combusted, or a combination thereof.

[0069] The production of lime by calcining limestone can be carried out using various types of furnaces, such as, but not limited to, shaft kilns, rotary furnaces, or electric furnaces. The use of electric furnaces for calcination and the associated advantages are described in U.S. Provisional Application No. 63 / 046,239, filed June 30, 2020, which is incorporated herein by reference in its entirety.

[0070] These calcination apparatuses are suitable for calcining limestone in the form of lumps having a diameter of several millimeters to tens of millimeters. The waste streams of cement plants include waste streams from both wet process plants and dry process plants, which may use shaft kilns, rotary furnaces, electric furnaces, or a combination thereof, and may include pre-calcination furnaces. Each of these industrial plants may burn a single fuel, or two or more fuels, sequentially or simultaneously.

[0071] As shown in Figures 1-3, limestone obtained from a limestone quarry is calcined in a cement plant, resulting in the formation of lime and CO2 gas. The lime may be calcium oxide in solid form derived from the dry furnace / cementation process, or / or a combination of calcium oxide and calcium hydroxide in slurry form within the wet furnace / cementation process. In the wet process, calcium oxide (also known as a basic anhydride that converts to its hydroxide form in water) may exist in its hydrated form, for example, calcium hydroxide, but is not limited to these. Calcium hydroxide (also called slaked lime) is the common hydrated form of calcium oxide, but other intermediate hydrated complexes and / or water complexes may also be present in the slurry, and all of these are within the scope of the methods and systems provided herein. It should be understood that although lime is shown as CaO in some of the figures herein, it may exist as Ca(OH)2 or a combination of CaO and Ca(OH)2.

[0072] Lime can be poorly soluble in water. In the methods and systems provided herein, the solubility of lime is increased by treating it with a solubilizing agent.

[0073] In the methods and systems provided herein, lime is solvated or dissolved or solubilized with a solubilizing agent, such as an aqueous solution of a base, under one or more dissolution conditions (step A in Figures 1-3) to produce a first aqueous solution containing a calcium salt. For illustrative purposes only, in the figures, the aqueous solution of the base, such as a nitrogen-containing inorganic salt solution, is shown as an ammonium chloride (NH4Cl) solution, and the subsequent calcium salt is shown as calcium chloride (CaCl2). Various examples of bases are provided herein and are all within the scope of the present invention.

[0074] As used herein, "base" includes any base or conjugate base of an acid. In some embodiments, the base is a solubilizing base that solubilizes or dissolves calcium derived from lime, leaving solid impurities. The base includes, but is not limited to, nitrogen-containing inorganic salts, nitrogen-containing organic salts, or combinations thereof.

[0075] As used herein, "N-containing inorganic salt" includes any inorganic salt containing nitrogen. Examples of N-containing inorganic salts, but are not limited to, ammonium halides (where the halide is any halogen), ammonium sulfate, ammonium sulfite, ammonium nitrate, and ammonium nitrite. In some embodiments, the ammonium halide is ammonium chloride or ammonium bromide. In some embodiments, the ammonium halide is ammonium chloride.

[0076] As used herein, "N-containing organic salt" includes any salt of an organic compound containing nitrogen. Examples of N-containing organic compounds include, but are not limited to, aliphatic amines, alicyclic amines, heterocyclic amines, and combinations thereof.

[0077] When used herein, "aliphatic amine" refers to formula (R) n -NH 3-n The formula (R) contains any alkylamine (where n is an integer from 1 to 3, and R is independently a linear or branched substituted or unsubstituted alkyl between C1 and C8).n -NH 3-n An example of the corresponding halide salt (chloride salt, bromide salt, fluoride salt, or iodide salt) of the alkylamine is (R) n -NH 4-n + Cl - is. In some embodiments, when R is a substituted alkyl, this substituted alkyl is independently substituted with halogen, hydroxyl, acid and / or ester.

[0078] For example, when R is alkyl in (R) n -NH 3-n this alkylamine may be, by way of example only, a primary alkylamine such as methylamine, ethylamine, butylamine, pentylamine, etc., and this alkylamine may be, by way of example only, a secondary amine such as dimethylamine, diethylamine, methylethylamine, etc., and / or this alkylamine may be, by way of example only, a tertiary amine such as trimethylamine, triethylamine, etc.

[0079] For example, when R is a substituted alkyl substituted with hydroxyl in (R) n -NH 3-n this substituted alkylamine includes, but is not limited to, alkanolamines such as monoalkanolamine, dialkanolamine, or trialkanolamine, for example monoethanolamine, diethanolamine, or triethanolamine, etc.

[0080] For example, when R is a substituted alkyl substituted with halogen in (R) n -NH 3-n this substituted alkylamine is, for example, chloromethylamine, bromomethylamine, chloroethylamine, bromoethylamine, etc.

[0081] For example, when R is (R) n -NH 3-nIn the case where the substituted alkyl is an acid-substituted alkyl, the substituted alkylamine is, for example, an amino acid. In some embodiments, the aforementioned amino acid has a polar uncharged alkyl chain, and examples include, but are not limited to, serine, threonine, asparagine, glutamine, or combinations thereof. In some embodiments, the aforementioned amino acid has a charged alkyl chain, and examples include, but are not limited to, arginine, histidine, lysine, aspartic acid, glutamic acid, or combinations thereof. In some embodiments, the aforementioned amino acid is glycine, proline, or combinations thereof.

[0082] When used herein, "alicyclic amine" refers to formula (R) n -NH 3-n The formula (R) contains any alicyclic amine (where n is an integer from 1 to 3, and R is independently one or more all-carbon rings, which may be saturated or unsaturated but not aromatic). The alicyclic compound may have one or more aliphatic side chains attached. n -NH 3-n An example of the corresponding salt of the alicyclic amine is (R) n -NH 4-n + Cl - Examples of alicyclic amines, though not limited to them, include cycloalkylamines, namely cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine, cycloheptylamine, and cyclooctylamine.

[0083] When used herein, a "heterocyclic amine" comprises at least one heterocyclic aromatic ring bonded to at least one amine. Examples of heterocyclic rings, but not limited to, include pyrroles, pyrrolidines, pyridines, and pyrimidines. Such chemicals are well known in the art and are commercially available.

[0084] In the methods and systems provided herein, lime is dissolved or solubilized under one or more dissolution conditions in a solubilizing agent, such as an aqueous solution of a base (step A in Figures 1-3), to produce a first aqueous solution containing a calcium salt and a gas stream containing ammonia.

[0085] As shown in step A of Figures 1-3, the base is shown as ammonium chloride (NH4Cl). The possible reactions of lime are... CaO+2NH4Cl(aqueous solution) → CaCl2(aqueous solution)+2NH3+H2O Ca(OH)2+2NH4Cl(aqueous solution) → 2NH3+CaCl2+2H2O If so, it can be solubilized by treatment with NH4Cl (fresh and recycled as described below).

[0086] Similarly, if the base is an N-containing organic salt, the reaction may be shown as follows: CaO+2NH3RCl → CaCl2(aqueous solution)+2NH2R+H2O

[0087] In some embodiments, a base or nitrogen-containing inorganic salt, such as an ammonium salt, for example, an ammonium chloride solution, may be supplemented with anhydrous ammonia or an aqueous ammonia solution to maintain an optimal level of ammonium chloride in the solution.

[0088] In some embodiments, the first aqueous solution containing the calcium salt obtained after the dissolution of lime may contain sulfur, depending on the source of the lime. Sulfur can be introduced into the first aqueous solution after solubilizing the lime with one of the bases described herein. In alkaline solutions, but not limited to, sulfite ions (SO3) may be present. 2- ), sulfate ions (SO4 2- ), water sulfide ions (HS - ), thiosulfate ion (S2O3 2- ), polysulfide (S n 2-Various sulfur compounds containing various sulfur ion species, including thiols (RSH), may be present in the solution. "Sulfur compound" as used herein includes any sulfur ion-containing compound.

[0089] In some embodiments, the first aqueous solution further comprises a base, such as ammonia, and / or an N-containing inorganic salt or an N-containing organic salt.

[0090] In some embodiments, the amount of base, such as a nitrogen-containing inorganic salt, a nitrogen-containing organic salt, or a combination thereof, is in excess of more than 20% or more than 30% relative to lime. In some embodiments, the molar ratio of base:lime (or nitrogen-containing inorganic salt:lime or nitrogen-containing organic salt:lime or ammonium chloride:lime) is between 0.5:1 and 2:1, or between 0.5:1 and 1.5:1, or between 1:1 and 1.5:1, or 1.5:1, or 2:1, or 2.5:1, or 1:1.

[0091] In some embodiments of the methods described herein, polyhydroxy compounds are not used to form the precipitate and / or product provided herein.

[0092] In some embodiments of the methods and systems described herein, one or more dissolution conditions are between approximately 30 and 200°C, or between approximately 30 and 150°C, or between approximately 30 and 100°C, or between approximately 30 and 75°C, or between approximately 30 and 50°C, or between approximately 40 and 200°C, or between approximately 40 and 150°C, or between approximately 40 and 100°C, or between approximately 40 and 75°C, or between approximately 40 and 50°C, or between approximately 50 and 200°C, or between approximately 50 and 150°C, or approximately The following are selected from the group consisting of a temperature between 50 and 100°C, a pressure between approximately 0.1 and 50 atm, or between approximately 0.1 and 40 atm, or between approximately 0.1 and 30 atm, or between approximately 0.1 and 20 atm, or between approximately 0.1 and 10 atm, or between approximately 0.5 and 20 atm, and a wt% of N-containing inorganic or organic salt in water between approximately 0.5 and 50%, or between approximately 0.5 and 25%, or between approximately 0.5 and 10%, or between approximately 3 and 30%, or between approximately 5 and 20%, or combinations thereof.

[0093] For example, stirring can be used to dissolve lime using a base solution in a dissolution reactor by eliminating hot and cold spots. In some embodiments, the concentration of lime in water may be between 1 and 10 g / L, between 10 and 20 g / L, between 20 and 30 g / L, between 30 and 40 g / L, between 40 and 80 g / L, between 80 and 160 g / L, between 160 and 320 g / L, between 320 and 640 g / L, or between 640 and 1280 g / L. To optimize the dissolution / solvation of lime, high-shear mixing, wet mill grinding, and / or sonication can be used to break up the lime. During or after high-shear mixing and / or wet mill grinding, the lime suspension may be treated with a base.

[0094] In some embodiments, the dissolution of lime using a base (e.g., shown as ammonium chloride) forms a first aqueous solution and a solid containing the calcium salt. In some embodiments, solid insoluble impurities can be removed from the first aqueous solution of the calcium salt (step B in Figures 1-3), and the aqueous solution is then treated with carbon dioxide in the process. The solid can be removed from the aqueous solution by filtration and / or centrifugation techniques, if necessary.

[0095] Step B in Figures 1-3 is optional, and in some embodiments, the solid may not be removed from the aqueous solution (not shown in Figures 1-3). The aqueous solution containing the calcium salt and the solid are brought into contact with carbon dioxide (step C in Figures 1-3) to form a precipitate. In such embodiments, the precipitate further includes solids.

[0096] In some embodiments, the solid obtained from the dissolution of lime (shown as insoluble impurities in Figures 1-3) is a calcium-depleted solid and can be used as a cement substitute (e.g., a substitute for Portland cement). In some embodiments, the solid includes silicates, iron oxides, alumina, or combinations thereof. Silicates include, but are not limited to, clay (phyllosilicates) and aluminosilicates.

[0097] In some embodiments, the solid is present in aqueous solutions, precipitates, or combinations thereof in amounts between 1 and 40 wt%, or between 1 and 30 wt%, or between 1 and 20 wt%, or between 1 and 10 wt%, or between 1 and 5 wt%, or between 1 and 2 wt%.

[0098] As shown in step C of Figure 1, the first aqueous solution (and optionally a solid) containing the calcium salt, along with the dissolved ammonia and / or ammonium salt, is brought into contact with a gas stream containing carbon dioxide recycled from the calcination step of each process under one or more precipitation conditions to form a precipitate and supernatant containing calcium carbonate and vaterite, as shown in the following reaction. CaCl2 (aqueous solution) + 2NH3 (aqueous solution) + CO2 (gas) + H2O → CaCO3 (solid) + 2NH4Cl (aqueous solution)

[0099] The absorption of CO2 into the first aqueous solution produces CO2-filled water containing carbonic acid, which is in equilibrium with both bicarbonate and carbonate species. The precipitate is prepared under one or more precipitation conditions (as described herein) suitable for forming a vaterite-containing material or PCC material.

[0100] In one embodiment, a method is provided for forming vaterite-containing calcium carbonate, comprising: (i) calcining limestone to form a gas stream containing lime and carbon dioxide; (ii) dissolving the lime in an aqueous base solution under one or more dissolution conditions to produce a first aqueous solution containing a calcium salt and a gas stream containing ammonia; and (iii) treating the first aqueous solution containing the calcium salt with a gas stream containing carbon dioxide and a gas stream containing ammonia under one or more precipitation conditions to form a precipitate containing vaterite-containing calcium carbonate and a supernatant solution. This embodiment is shown in Figure 2, where the gas stream containing CO2 from the calcination step and the gas stream containing NH3 from step A of the process are recycled to a precipitation reactor for the formation of a precipitate (step C). The remaining steps in Figure 2 are identical to those in Figure 1. It should be understood that both processes in Figure 1 and Figure 2 can also be carried out simultaneously so that a base, e.g., an N-containing inorganic salt or an N-containing organic salt, and optionally ammonia, may be partially present in the first aqueous solution and partially present in the gas stream.

[0101] The reaction carried out in the aforementioned embodiment may be shown as follows. CaCl2 (aqueous solution) + 2NH3 (gas) + CO2 (gas) + H2O → CaCO3 (solid) + 2NH4Cl (aqueous solution)

[0102] In some embodiments of the aspects and embodiments provided herein, the gas stream containing ammonia may have ammonia from an external source and / or be recovered from step A of the process and recycled.

[0103] In some embodiments and examples of the representations provided herein, where the gas stream contains ammonia and / or carbon dioxide, no external source of carbon dioxide and / or ammonia is used, and the process is a closed-loop process. Such a closed-loop process is illustrated in the figures provided herein.

[0104] In some embodiments, the dissolution of lime using a portion of the N-containing organic salt may not result in the formation of ammonia gas, or the amount of ammonia gas formed may be substantial. In embodiments where ammonia gas is not formed, or is formed in substantial amounts, the method and system shown in Figure 1 are applicable, in which a first aqueous solution containing the calcium salt is treated with carbon dioxide gas. In such embodiments, the organic amine salt may remain completely or partially dissolved in the aqueous solution, or it may separate as an organic amine layer, as shown in the reactions below. CaO+2NH3R + Cl - → CaCl2(aqueous solution)+2NH2R+H2O

[0105] The nitrogen-containing organic salt or nitrogen-containing organic compound remaining in the supernatant after precipitation may be called a residual nitrogen-containing organic salt or residual nitrogen-containing organic compound. This method and system are described herein for the recovery of residual compounds from the precipitate and supernatant.

[0106] In one embodiment, a method is provided for forming vaterite-containing calcium carbonate, comprising: (i) calcining limestone to form a gas stream containing lime and carbon dioxide; (ii) dissolving the lime in an aqueous solution of an inorganic salt containing nitrogen or an organic salt solution containing nitrogen under one or more dissolution conditions to produce a first aqueous solution containing a calcium salt and a gas stream containing ammonia; (iii) recovering the gas stream containing carbon dioxide and the gas stream containing ammonia, subjecting the gas stream to a cooling process under one or more cooling conditions to condense a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, or a combination thereof; and (iv) treating the first aqueous solution containing the calcium salt with a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, or a combination thereof under one or more precipitation conditions to form a precipitate containing vaterite-containing calcium carbonate and a supernatant solution. This embodiment is shown in Figure 3, where the gas stream containing CO2 from the calcination step and the gas stream containing NH3 from step A of the process are recycled to a cooling reactor / reaction for the formation of carbonate and bicarbonate solutions, as further shown in the following reactions herein (step F). The remaining steps in Figure 3 are identical to the steps in Figures 1 and 2.

[0107] The embodiments described above shown in Figure 3 can be combined with the embodiments shown in Figures 1 and / or 2, and it should be understood that precipitation step C includes treating a first aqueous solution containing a calcium salt with a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, or a combination thereof (as shown in Figure 3), treating the first aqueous solution containing a calcium salt with a gas stream containing carbon dioxide (as shown in Figure 1), and / or treating the first aqueous solution containing a calcium salt with a gas stream containing carbon dioxide and a gas stream containing ammonia (as shown in Figure 2). In such embodiments, the gas stream containing carbon dioxide is divided into a stream toward the cooling process and a stream toward the precipitation process. Similarly, in such embodiments, the gas stream containing ammonia is divided into a stream toward the cooling process and a stream toward the precipitation process. Any combination of processes illustrated in Figures 1-3 is possible and all are within the scope of this disclosure.

[0108] In some embodiments of the aforementioned model, the second aqueous solution further comprises ammonium carbamate. Ammonium carbamate is composed of ammonium ions NH4 + , and carbamate ion H2NCO2 - It has the formula NH4[H2NCO2] consisting of the above. In the embodiments described above and some embodiments of the embodiments, the second aqueous solution includes ammonium bicarbonate, ammonium carbonate, ammonia, ammonium carbamate, or a combination thereof.

[0109] The combination of these condensation products in the second aqueous solution may depend on one or more of the cooling conditions. Table 1, presented below, shows various combinations of condensation products in the second aqueous solution. [Table 1]

[0110] In some embodiments of the aforementioned aspects and embodiments, the gas stream (e.g., the gas stream directed toward the cooling reaction / reactor (step F in Figures 1-3)) further includes steam. In some embodiments of the aforementioned aspects and embodiments, the gas stream is between approximately 20-90%, or between approximately 20-80%, or between approximately 20-70%, or between approximately 20-60%, or between approximately 20-55%, or between approximately 20-50%, or between approximately 20-40%, or between approximately 20-30%, or between approximately 20-25%, or between approximately 30-90%, or between approximately 30-80%, or between approximately 30-70%, or between approximately 30-60%, or between approximately 30-50%, or Further containing water vapor between approximately 30-40%, or between approximately 40-90%, or between approximately 40-80%, or between approximately 40-70%, or between approximately 40-60%, or between approximately 40-50%, or between approximately 50-90%, or between approximately 50-80%, or between approximately 50-70%, or between approximately 50-60%, or between approximately 60-90%, or between approximately 60-80%, or between approximately 60-70%, or between approximately 70-90%, or between approximately 70-80%, or between approximately 80-90%.

[0111] In the aforementioned embodiments and some of the embodiments, no external water is added to the cooling process. The cooling process is similar to the condensation of gas in existing water vapor (but not to gas absorption), and therefore, it should be understood that the gas is not absorbed by the water but is cooled itself along with the water vapor. Condensing the gas into a liquid stream can offer advantages in process control compared to vapor absorption. As just one example, condensing the gas into a liquid stream may allow the liquid stream to be pumped into the sedimentation step. Pumping a liquid stream can be less costly than compressing a vapor stream into the absorption process.

[0112] The cooling reaction / reactor intermediate step may include the formation of ammonium carbonate and / or ammonium bicarbonate and / or ammonium carbamate by the following reactions: 2NH3 + CO2 + H2O → (NH4)2CO3 NH3 + CO2 + H2O → (NH4)HCO3 2NH3 + CO2 → (NH4)NH2CO2

[0113] Similar reactions may also be observed with N-containing organic salts. 2NH2R + CO2 + H2O → (NH3R)2CO3 NH2R + CO2 + H2O → (NH3R)HCO3

[0114] The advantage of cooling ammonia in a cooling reaction / reactor is that ammonia can have a limited vapor pressure in the gas phase of the dissolution reaction. By reacting ammonia with CO2, as shown in the reaction above, some of the ammonia can be removed from the vapor space, leaving more ammonia in the dissolution solution.

[0115] Next, a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, (and optionally ammonium carbamate) or a combination thereof (exiting the cooling reaction / reactor in Figure 3) is treated in the precipitation reaction / reactor with the first aqueous solution containing calcium salts from the dissolution reaction / reactor (step C) to form a precipitate containing vaterite. (NH4)2CO3 + CaCl2 → CaCO3 (vaterite) + 2NH4Cl (NH4)HCO3 + NH3 + CaCl2 → CaCO3 (vaterite) + 2NH4Cl + H2O 2(NH4)HCO3 + CaCl2 → CaCO3 (vaterite) + 2NH4Cl + H2O + CO2 (NH4)NH2CO2 + H2O + CaCl2 → CaCO3 (vaterite) + 2NH4Cl

[0116] Independent of any intermediate steps, the combination of reactions leads to the following overall process chemistry. CaO (lime) → CaCO3 (vaterite)

[0117] In some embodiments of the aspects and embodiments provided herein, one or more cooling conditions are between approximately 0 and 200°C, or between approximately 0 and 150°C, or between approximately 0 and 75°C, or between approximately 0 and 100°C, or between approximately 0 and 80°C, or between approximately 0 and 60°C, or between approximately 0 and 50°C, or between approximately 0 and 40°C, or between approximately 0 and 30°C, or between approximately 0 and 20°C, or between approximately 0 and 10°C, or between approximately 10 and 100°C, or between approximately 10 and 80°C, or between approximately 10 and 60°C, or between approximately 10 and 50°C, or between approximately 10 and 40°C, or between approximately 10 and 30°C, or between approximately 20 and 1 This includes temperatures between 0°C, or between approximately 20 and 80°C, or between approximately 20 and 60°C, or between approximately 20 and 50°C, or between approximately 20 and 40°C, or between approximately 20 and 30°C, or between approximately 30 and 100°C, or between approximately 30 and 80°C, or between approximately 30 and 60°C, or between approximately 30 and 50°C, or between approximately 30 and 40°C, or between approximately 40 and 100°C, or between approximately 40 and 80°C, or between approximately 40 and 60°C, or between approximately 50 and 100°C, or between approximately 50 and 80°C, or between approximately 60 and 100°C, or between approximately 60 and 80°C, or between approximately 70 and 100°C, or between approximately 70 and 80°C.

[0118] In some embodiments of the aspects and embodiments provided herein, one or more cooling conditions include pressures between about 0.5 and 50 atm, or between about 0.5 and 25 atm, or between about 0.5 and 10 atm, or between about 0.1 and 10 atm, or between about 0.5 and 1.5 atm, or between about 0.3 and 3 atm.

[0119] In some embodiments, the formation and quality of reactive vaterites formed in the methods and systems provided herein depend on the amount and / or ratio of condensation products in a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, ammonium carbamate, or a combination thereof.

[0120] In some embodiments, the presence or absence or distribution of condensation products in a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, ammonium carbamate, or a combination thereof can be optimized to maximize the formation of reactive vaterites and / or obtain a desired particle size distribution. This optimization can be based on one or more cooling conditions, such as the pH of the aqueous solution in the cooling reactor, the flow rates of CO2 and NH3 gases, and / or the CO2:NH3 gas ratio. The inflow into the cooling reactor (F in Figure 3) may be exhaust gas from the dissolution reactor containing carbon dioxide (CO2(gas)), ammonia (NH3(gas)), steam, and, if necessary, new makeup water (or some other dilution water stream). The outflow may be a slipstream of the reactor's recirculating fluid (second aqueous solution), which is directed towards the precipitation reactor to contact the first aqueous solution and, if necessary, additional carbon dioxide and / or ammonia. The pH of the system can be controlled by adjusting the flow rates of CO2 and NH3 into the cooling reactor. The conductivity of the system can be controlled by adding dilution makeup water to the cooling reactor. The volume can be kept constant by using a level detector in the cooling reactor or its reservoir.

[0121] In some embodiments, a higher pH of the aqueous solution in the cooling reactor (which can be achieved by a higher flow rate of ammonia) may be favorable for the formation of carbamates, while a lower pH of the aqueous solution in the cooling reactor (which can be achieved by a lower flow rate of ammonia) may be favorable for the formation of carbonates and / or bicarbonates. In some embodiments, one or more cooling conditions include the pH of the aqueous solution formed in the cooling reactor being between about 8 and 12, or between about 8 and 11, or between about 8 and 10, or between about 8 and 9.

[0122] In some embodiments, the carbon dioxide flow rate can be modified to achieve a desired pH of the second aqueous solution exiting the cooling reactor. For example, if the pH of the second aqueous solution is high, the carbon dioxide flow rate can be increased to lower the pH, or if the pH of the second aqueous solution is low, the carbon dioxide flow rate can be decreased to raise the pH. The effect of the CO2 flow rate on the pH of the second aqueous solution and the ratio of carbamate:carbonate:bicarbonate formation can be shown in Example 3 provided herein. Similarly, the effect of the CO2:NH3 ratio on the pH of the second aqueous solution and the ratio of carbamate:carbonate:bicarbonate formation can be shown in Example 4 provided herein. In some embodiments, one or more cooling conditions include a CO2:NH3 ratio in the cooling reactor between approximately 0.1:1 and 20:1, or between approximately 0.1:1 and 1:1, or between approximately 0.1:1 and 2:1, or between approximately 5:1 and 10:1, or between approximately 1:1 and 5:1, or between approximately 2:1 and 5:1.

[0123] Although Figure 3 shows a separate cooling reaction / reactor, it should be understood that in some embodiments, the dissolution reaction / reactor can be integrated with the cooling reaction / reactor, as shown in Figures 4-7. For example, the dissolution reactor can be integrated with a condenser that acts as a cooling reactor. A lime and base aqueous solution (shown as NH4Cl in Figures 4-7) is supplied together to the dissolution reaction / reactor so that a first aqueous solution containing a calcium salt (shown as CaCl2) is formed. This solution may contain solid impurities as needed, which remain at the bottom of the dissolution reactor. The first aqueous solution containing the calcium salt (shown as CaCl2) is withdrawn from the dissolution reaction / reactor for further treatment for precipitation. A gas stream containing ammonia and water vapor passes through the upper section of the dissolution reactor (i.e., the cooling reactor shown in Figures 4-7), where it is cooled with carbon dioxide and condensed into a second aqueous solution. Carbon dioxide can be obtained from a plant where limestone is calcined into lime and carbon dioxide. Next, carbon dioxide is supplied to the gas phase of the cooling reactor. A second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, ammonium carbamate, or a combination thereof is collected from the cooling reactor using various means, such as one or more trays (as shown, for example, in Figure 4).

[0124] In one embodiment, an integrated reactor is provided, and the reactor is, It includes a dissolution reactor integrated into the cooling reactor, and this dissolution reactor is located below the cooling reactor. This dissolution reactor is configured to dissolve lime in an aqueous solution of an inorganic salt or an organic salt solution containing nitrogen under one or more dissolution conditions to produce a first aqueous solution containing calcium salt, as well as a gas stream containing ammonia and water vapor, and This cooling reactor is operationally connected to the dissolution reactor and is configured to receive, under one or more cooling conditions, a gas stream containing ammonia and water vapor from the dissolution reactor, as well as a gas stream containing carbon dioxide from the calcination of limestone to lime, and to condense to form a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, ammonium carbamate, or a combination thereof.

[0125] Other various stereochemical configurations of the integrated reactor described above are shown in Figures 5–7. Figure 5 is another example of Figure 4. Figure 6 further illustrates the introduction of CO2 into the vapor space of a cooling reactor filled with packing material. The packing material may be any inert material used to facilitate the mass transfer of NH3 and CO2 from the vapor to the liquid phase. The packing may be random or ordered. Random packing material may be any material having individual parts packed into the vessel or reactor. Ordered packing material may be any material having individual monoliths that are shaped to provide surface area and enhance mass transfer. Examples of loose, irregular, or random packing materials, but not limited to, include Raschig rings (e.g., of ceramic material), Paul rings (e.g., of metal and plastic), Lessing rings, Michael Bialecki rings (e.g., of metal), Berl saddles, Interox saddles (e.g., of ceramic), Super Interox saddles, Tellerette® rings (e.g., helical shapes of polymer materials), and the like.

[0126] Examples of ordered packing materials include, but are not limited to, thin corrugated metal plates or gauze (honeycomb structure) of various shapes with specific surface area. The ordered packing material may be used as rings or layers, or stacks of rings or layers, having a diameter that can fit the diameter of the reactor. The rings may be individual rings or stacks of rings that completely fill the reactor. In some embodiments, any gaps left in the reactor by ordered packing are filled with irregular or random packing material.

[0127] Examples of ordered packing materials include, but are not limited to, Flexipac®, Intalox®, and Flexipac® ​​HC®. In ordered packing materials, corrugated sheets can be arranged in a cross pattern to create channels for the gas phase. Intersections of the corrugated sheets can create mixing points for the liquid and gas phases. Ordered packing materials can be rotated around the column (reactor) axis to cross-mix the vapor and liquid streams and allow them to diverge in all directions. Ordered packing materials can be used with various corrugation sizes, and the packing arrangement can be optimized to obtain the highest efficiency, capacity, and pressure drop requirements of the reactor. Ordered packing materials can be made from building materials, but are not limited to, titanium, stainless steel alloys, carbon steel, aluminum, nickel alloys, copper alloys, zirconium, thermoplastics, etc. The corrugated wrinkles in ordered packing materials may be of any size, but are not limited to, including packing designated Y with a 45° inclination angle from the horizontal or packing designated X with a 60° inclination angle from the horizontal. X-filling can theoretically provide a lower pressure drop for each stage over the same surface area. The specific surface area of ​​ruled filling is 50-800 m². 2 / m 3 Between 75 and 350 meters 2 / m 3 Between, or 200-800m 2 / m 3 Between, or 150-800m 2 / m 3 Between, or 500-800m 2 / m 3 It could be between these two points.

[0128] In some embodiments, the cooling reactor further includes an inlet for introducing a scrubbing fluid, such as an ammonium chloride solution (Figure 6) or water (Figure 7), to the top of the packing material in the cooling reactor. The scrubbing fluid, such as an ammonium chloride solution, or an ammonia solution, or water, promotes the formation of condensation products, such as ammonium bicarbonate, ammonium carbonate, ammonia, ammonium carbamate, or combinations thereof. The scrubbing fluid can provide more liquid volume for gas condensation. In some embodiments, the scrubbing fluid can further assist the condensation process if it is pre-cooled. If the scrubbing fluid is an ammonium chloride solution (Figure 6), the ammonium chloride solution may be part of the ammonium chloride solution supplied to the dissolution reactor. In some embodiments, a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, ammonium carbamate, ammonium chloride, or combinations thereof, collected from the condensate originating from the cooling reactor, can be recycled to the cooling reactor as a scrubbing fluid to further promote the condensation process. In some embodiments, the second aqueous solution can be cooled in a heat exchanger before being recycled to the cooling reactor.

[0129] Other gases, such as flue gas in the carbon dioxide-containing gas stream (obtained from the calcination process), can be released from the cooling reactor (shown in Figures 4-7).

[0130] In the embodiments described above, both the dissolution reactor and the cooling reactor are equipped with inlets and outlets to receive the required gas and collect the aqueous stream. In some embodiments of the embodiments described above, the dissolution reactor includes a stirrer for mixing lime with the aqueous base solution. The stirrer can also facilitate the upward movement of the gas. In some embodiments of the embodiments described above, the dissolution reactor is configured to collect the solid that has settled at the bottom of the reactor after the removal of the first aqueous solution containing the calcium salt. In some embodiments of the embodiments described above, the cooling tower includes one or more trays configured to capture and collect the condensed second aqueous solution and prevent the second aqueous solution from falling back into the dissolution reactor. Thus, cooling / condensation can be achieved by using injectors, bubblers, fluid venturi reactors, spaggers, gas filters, sprays, trays, or packed column reactors, etc.

[0131] In some embodiments, the cooling reactor includes a heat exchanger or heat exchange surface within the reactor. The heat exchanger may include one or more tubes through which a cold fluid circulates, and thus the cold fluid is isolated from the gas phase in the cooling reactor but promotes a temperature drop in the cooling reactor for gas condensation. The cold fluid may be cooling water, the aforementioned scrubbing solution, and the like. In some embodiments, a second aqueous solution exiting the cooling reactor is cooled by the heat exchanger before being used as a scrubbing solution.

[0132] As shown in step C of Figures 1-2, a first aqueous solution containing a calcium salt, obtained from the treatment of lime with a base described herein, such as an ammonium salt or ammonium halide, is brought into contact with CO2 and optionally NH3 from step A at any time before, during, or after the first aqueous solution containing the calcium salt is subjected to one or more precipitation conditions (i.e., conditions that allow the precipitation of a precipitate). Similarly, as shown in step C of Figure 3, a first aqueous solution containing a calcium salt, obtained from the treatment of lime with a base described herein for step A, such as an ammonium salt or ammonium halide, is brought into contact with a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, ammonium carbamate, or a combination thereof, from the cooling reaction / reactor at any time before, during, or after the first aqueous solution containing the calcium salt is subjected to one or more precipitation conditions (i.e., conditions that allow the precipitation of a precipitate).

[0133] Therefore, in some embodiments, a first aqueous solution containing a calcium salt is brought into contact with CO2 (and NH3 in the case of Figure 2 or a second aqueous solution in the case of Figure 3) before the aqueous solution is subjected to one or more precipitation conditions favorable for the formation of a precipitate containing a stable or reactive vaterite or PCC. In some embodiments, a first aqueous solution containing a calcium salt is brought into contact with CO2 (and NH3 in the case of Figure 2 or a second aqueous solution in the case of Figure 3) while the aqueous solution is subjected to one or more precipitation conditions favorable for the formation of a precipitate containing a stable or reactive vaterite or PCC. In some embodiments, a first aqueous solution containing a calcium salt is brought into contact with CO2 (and NH3 in the case of Figure 2 or a second aqueous solution in the case of Figure 3) before and while the aqueous solution is subjected to one or more precipitation conditions favorable for the formation of a precipitate containing a stable or reactive vaterite or PCC. In some embodiments, a first aqueous solution containing a calcium salt is subjected to one or more precipitation conditions favorable for the formation of a stable or reactive vaterite or PCC precipitate, and then brought into contact with CO2 (and NH3 in the case of Figure 2 or a second aqueous solution in the case of Figure 3).

[0134] In some embodiments, the step of contacting a first aqueous solution containing a calcium salt with carbon dioxide and optionally ammonia or a second aqueous solution is achieved by contacting the first aqueous solution to achieve and maintain a desired pH range, a desired temperature range, and / or a desired divalent cation concentration using a convenient protocol (precipitation conditions) described herein. In some embodiments, the system includes a precipitation reactor configured to contact a first aqueous solution containing a calcium salt with carbon dioxide and optionally ammonia derived from step A of the process, or the system includes a precipitation reactor configured to contact a first aqueous solution containing a calcium salt with a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, (optionally ammonium carbamate), or a combination thereof.

[0135] In some embodiments, a first aqueous solution containing a calcium salt can be placed in a precipitation reactor, where the amount of the first aqueous solution containing the calcium salt added is sufficient to raise its pH to a desired level (e.g., a pH that induces precipitation of the precipitate), such as pH 7-9, pH 7-8.7, pH 7-8.5, pH 7-8, pH 7.5-8, pH 8-8.5, pH 8.5-9, pH 9-14, pH 10-14, pH 11-14, pH 12-14, or pH 13-14. In some embodiments, the pH of the first aqueous solution containing the calcium salt is maintained between 7 and 9, or between 7 and 8.7, or between 7 and 8.5, or between 7.5 and 8.5, or between 7 and 8, or between 7.6 and 8.5, or between 8 and 8.5, or between 7.5 and 9.5, in order to form a precipitate containing stable vaterite, reactive vaterite, or PCC when brought into contact with carbon dioxide and optionally NH3 or the second aqueous solution.

[0136] In some embodiments, the first aqueous solution is fixed to a column or bed (example of precipitation reactor configuration). In such embodiments, the water is diluted to a desired pH or to a specific divalent cation (Ca 2+A sufficient amount of calcium salt solution is passed through or over the solution to raise the concentration to a certain level. In some embodiments, the first aqueous solution may be circulated more than once, where the first precipitation cycle primarily removes calcium carbonate minerals, leaving an alkaline solution to which an additional first aqueous solution containing calcium salts may be added. A gas stream containing carbon dioxide and optionally NH3, or the second aqueous solution, is brought into contact with the recirculated aqueous solution to allow for further precipitation of calcium carbonate and / or bicarbonate compounds. In these embodiments, it will be recognized that the aqueous solution after the first precipitation cycle may be brought into contact with a gas stream containing CO2 and optionally NH3 (or the second aqueous solution) before, during, and / or after the addition of the first aqueous solution containing calcium salts. In these embodiments, water can be recirculated or newly introduced. Therefore, the order of addition of the gas stream containing CO2 and optionally NH3, and the first aqueous solution containing calcium salts can vary. For example, a first aqueous solution containing a calcium salt can be added to, for example, brine, seawater, or freshwater, and then a gas stream containing CO2 and optionally NH3, or a second aqueous solution, can be added. In another example, a gas stream containing CO2 and optionally NH3, or a second aqueous solution, can be added to, for example, brine, seawater, or freshwater, and then the first aqueous solution containing a calcium salt can be added. In yet another example, a gas stream containing CO2 and optionally NH3, or a second aqueous solution, can be added directly to the first aqueous solution containing a calcium salt.

[0137] A first aqueous solution containing a calcium salt can be brought into contact with a gas stream containing CO2 and optionally NH3 using any convenient protocol. The desired contact protocols include, but are not limited to, direct contact protocols (e.g., gas foaming through the first aqueous solution), simultaneous contact means (i.e., contact between a unidirectional gas-phase stream and a liquid-phase stream), counter-flow means (i.e., contact between a reverse-flow gas-phase stream and a liquid-phase stream), and so on. Thus, contact can be achieved by using injectors, bubblers, fluid venturi reactors, spaggers, gas filters, sprays, trays, or packed column reactors within a precipitation reactor. In some embodiments, gas-liquid contact is achieved by forming a liquid film of the solution using a flat jet nozzle, where the gas and liquid film move in counter-flow, parallel-flow, or reverse-flow directions, or in any other suitable manner. In some embodiments, gas-liquid contact is achieved by bringing droplets of a solution having an average diameter of 500 micrometers or less, for example, 100 micrometers or less, into contact with a gas source.

[0138] In some embodiments, substantially all (e.g., 80% or more, or 90%, 99.9%, or 100%) of the CO2 gas (of calcination origin) and optionally the NH3 waste stream generated by step A of the process illustrated in the figures herein are used for the precipitation of the precipitate material. In some embodiments, a portion of the CO2 gas and optionally the NH3 waste stream is used for the precipitation of the precipitate material, which may be 75% or less of the waste gas stream, or 60% or less, including 50% and less.

[0139] The gas-liquid contact protocols described herein may be used any number of times. The gas-liquid contact or liquid-liquid contact is continued until the pH of the precipitation reaction mixture is optimal (for example, various pH values ​​optimal for forming a precipitate containing reactive vaterite are described herein), after which the precipitation reaction mixture may be stirred. The rate at which the pH decreases can be controlled by further adding a first aqueous solution containing a calcium salt during the gas-liquid contact or liquid-liquid contact. Further additional first aqueous solutions may be added after sparging to raise the pH back to a basic level for precipitating some or all of the precipitate. In any case, the precipitate may be formed when protons are removed from certain species in the precipitation reaction mixture. The precipitate containing the carbonate may then be separated and further processed as needed.

[0140] The rate at which the pH decreases can be controlled by adding an additional supernatant or a first aqueous solution containing a calcium salt during gas-liquid or liquid-liquid contact. Furthermore, an additional supernatant or a first aqueous solution containing a calcium salt may be added after gas-liquid or liquid-liquid contact to raise the pH back to a basic level (e.g., between 7 and 9, or between 7 and 8.5, or between 7 and 8, or between 8 and 9) to precipitate some or all of the precipitated material.

[0141] In the methods and systems provided herein, an aqueous solution produced by contacting a first aqueous solution containing a calcium salt with a gas stream containing CO2 and optionally NH3, or an aqueous solution produced by contacting a first aqueous solution containing a calcium salt with a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, (optionally ammonium carbamate), or a combination thereof, is subjected to one or more precipitation conditions sufficient to produce a precipitate containing stable or reactive vaterite or PCC, and a supernatant (i.e., the portion of the solution remaining after the precipitation of the precipitate) (step C in Figures 1-3). One or more precipitation conditions are favorable for the production of a precipitate containing stable or reactive vaterite or PCC.

[0142] One or more precipitation conditions include those that modulate the environment of the precipitation reaction mixture to produce a desired precipitate containing stable or reactive vaterite or PCC. Such one or more precipitation conditions suitable for forming a precipitate containing stable or reactive vaterite or PCC, which can be used in the embodiments and methods of the systems described herein, include, but are not limited to, temperature, pH, pressure, ion ratio, precipitation rate, presence of additives, presence of ionic species, concentration of additives and ionic species, stirring, residence time, mixing rate, stirring methods such as ultrasonic waves, presence of seed crystals, catalysts, membranes or substrates, dehydration, drying, ball milling, etc. In some embodiments, the average particle size of the stable or reactive vaterite or PCC may also vary depending on the one or more precipitation conditions used in the precipitation of the precipitate. In some embodiments, the percentage of stable or reactive vaterite in the precipitate may also vary depending on the one or more precipitation conditions used in the precipitation process.

[0143] For example, the temperature of the precipitation reaction can be raised to a temperature at which a suitable amount of the desired precipitate is obtained. In such embodiments, the temperature of the precipitation reaction can be raised to values ​​including 25°C to 60°C, or 30°C to 60°C, or 35°C to 60°C, or 40°C to 60°C, or 50°C to 60°C, or 25°C to 50°C, or 30°C to 50°C, or 35°C to 50°C, or 40°C to 50°C, or 25°C to 40°C, or 30°C to 40°C, or 25°C to 30°C. In some embodiments, the temperature of the precipitation reaction can be raised using energy from low- or zero-carbon emission sources (e.g., solar energy sources, wind energy sources, hydroelectric energy sources, waste heat obtained from carbon emission flue gases, etc.).

[0144] The pH of the precipitation reaction can also be raised to an amount suitable for the precipitation of the desired precipitate. In such embodiments, the pH of the precipitation reaction can be raised to an alkaline level suitable for precipitation. In some embodiments, the pH of the first aqueous solution containing a calcium salt, which is brought into contact with a gas stream containing carbon dioxide gas and optionally NH3 gas (or a second aqueous solution), is effective for the formation of stable or reactive vaterite or PCC. In some embodiments, the precipitation conditions required to form the precipitate include carrying out a step of precipitating a gas stream (or a second aqueous solution) containing carbon dioxide gas and optionally NH3 gas with a first aqueous solution containing a calcium salt at a pH higher than 7, i.e., pH 8, or between pH 7.1–8.5, or between pH 7.5–8, or between 7.5–8.5, or between 8–8.5, or between 8–9, or between 7.6–8.4, in order to form the precipitate. The pH can be raised to a pH of 9 or higher, for example, pH 10 or higher, including pH 11 or higher, or pH 12.5 or higher.

[0145] Adjusting the main ion ratio in the precipitate can affect the properties of the precipitate. The main ion ratio can have a considerable influence on polymorph formation. For example, as the magnesium:calcium ratio in water increases, aragonite can become the main polymorph of calcium carbonate in the precipitate, surpassing low-magnesium vaterite. At low magnesium:calcium ratios, low-magnesium calcite can become the main polymorph. In some embodiments, Ca 2+ and Mg 2+ When both are present, Mg in the precipitate 2+ Ca 2+ The ratio of Ca 2+ :Mg 2+ The ratios are 1:1 to 1:2.5, 1:2.5 to 1:5, 1:5 to 1:10, 1:10 to 1:25, 1:25 to 1:50, 1:50 to 1:100, 1:100 to 1:150, 1:150 to 1:200, 1:200 to 1:250, 1:250 to 1:500, or 1:500 to 1:1000. In some embodiments, Ca in the precipitate is 2+ Mg 2+ The ratio of (i.e., Mg 2+ :Ca 2+ The ratios are 1:1~1:2.5, 1:2.5~1:5, 1:5~1:10, 1:10~1:25, 1:25~1:50, 1:50~1:100, 1:100~1:150, 1:150~1:200, 1:200~1:250, 1:250~1:500, or 1:500~1:1000.

[0146] The precipitation rate can also have an effect on the formation of precipitated material, and the fastest precipitation rate is achieved by seeding the desired phase into the solution. Without seeding, rapid precipitation can be achieved by rapidly increasing the pH of the precipitation reaction mixture, which may result in more amorphous components. Higher pH leads to more rapid precipitation, which may result in more amorphous precipitated material.

[0147] The residence time of the precipitation reaction after contacting the first aqueous solution with a gas stream containing carbon dioxide gas and optionally NH3 gas (or with the second aqueous solution) can also have an effect on the formation of the precipitate. For example, in some embodiments, a longer residence time may result in the conversion of reactive vaterite to aragonite / calcite in the reaction mixture. In some embodiments, if the residence time is too short, the formation of reactive vaterite in the reaction mixture may be incomplete. Therefore, the residence time can be very important for the precipitation of reactive vaterite. Furthermore, the residence time may also affect the particle size of the precipitate. For example, if the residence time is too long, the particles may aggregate to form larger particles, which is undesirable for PCC formation. Therefore, in some embodiments, the reaction residence time is between about 5 and 60 minutes, or between about 5 and 15 minutes, or between about 10 and 60 minutes, or between about 15 and 60 minutes, or between about 15 and 45 minutes, or between about 15 and 30 minutes, or between about 30 and 60 minutes.

[0148] In some embodiments, one or more precipitation conditions for generating a desired precipitate from the precipitation reaction may include, as described above, temperature and pH, and, if any, the concentrations of additives and ionic species in the water. Additives are described herein below. The presence and concentration of additives may also be favorable for the formation of stable or reactive vaterites or PCCs. In some embodiments, medium-chain or long-chain fatty acid esters may be added to the first aqueous solution during precipitation to form PCCs. Examples of fatty acid esters, but not limited to, include cellulose, e.g., carboxymethylcellulose; sorbitol; citrates, e.g., sodium citrate or potassium citrate; stearates, e.g., sodium stearate or potassium stearate; phosphates, e.g., sodium phosphate or potassium phosphate; sodium tripolyphosphate; hexametaphosphates; EDTA; or combinations thereof. In some embodiments, a combination of stearate and citrate esters may be added during the precipitation step of the process to form PCCs.

[0149] One or more precipitation conditions may also include factors such as mixing rate, stirring method (e.g., ultrasonic), and the presence of seed crystals, catalysts, membranes, or substrates. In some embodiments, one or more precipitation conditions may include supersaturation conditions, temperature, pH, and / or concentration gradients, or the circulation or variation of any of these parameters. The protocol used to prepare the precipitate may be a batch, semi-batch, or continuous protocol. One or more precipitation conditions for generating precipitate material in a continuous flow system may differ from those in a semi-batch or batch system.

[0150] In some embodiments of the methods and systems provided herein, the formation of a precipitate containing stable or reactive vaterite can be promoted on the surface of the aggregate. In some embodiments of the methods and systems provided herein, where the aqueous solution is produced by contacting a first aqueous solution containing a calcium salt with a gas stream containing CO2 and optionally NH3 under one or more precipitation conditions (step C in Figures 1-3), or where the aqueous solution is produced by contacting a first aqueous solution containing a calcium salt with a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, (optionally ammonium carbamate), or a combination thereof, the methods and systems further include the step of adding aggregate to the aqueous solution to form a precipitate containing stable or reactive vaterite on the surface of the aggregate.

[0151] The term “aggregate,” as used herein, includes particulate compositions used in concrete, mortar, and other materials, such as roadbeds, asphalt, and other structures, and aggregates are suitable for use in such structures. Aggregates are particulate compositions that may be classified in some embodiments as fine aggregates or coarse aggregates. Fine aggregates generally consist of natural sand or crushed stone, with most particles passing through a 3 / 8-inch sieve. Coarse aggregates are generally any particles larger than 0.19 inches, but typically in diameter between 3 / 8 and 1.5 inches. Gravel can constitute coarse aggregates used in concrete, with crushed stone filling the remainder. In some embodiments, aggregates are crushed limestone. In some embodiments, aggregates are concrete that is used for another purpose or reused. The methods and systems provided herein add reusability or value (by having better bonding characteristics) to concrete used for another purpose from older projects.

[0152] In the aforementioned method and system, when aggregate is added to the precipitation step C, the precipitate forms an outer layer surrounding the surface of the aggregate, thereby activating the surface of the inert aggregate material. This activated surface of the aggregate (including reactive vaterite), which will come into contact with water (the dissolution-reprecipitation process from vaterite to aragonite, as described below herein) and cement, converts the vaterite into aragonite that bonds to the cement. The thus activated aggregate bonds better to the cement.

[0153] Therefore, in some embodiments, a method for forming calcium carbonate containing vaterite, (i) A step of calcining limestone to form a gas stream containing lime and carbon dioxide, (ii) Dissolving lime in an aqueous solution of a base under one or more dissolution conditions to produce a first aqueous solution containing a calcium salt and a gas stream containing ammonia, (iii) The step of adding aggregate to the first aqueous solution, (iv) A method is provided which includes the step of treating a first aqueous solution containing a calcium salt and an aggregate with a gas stream containing carbon dioxide and a gas stream containing ammonia under one or more precipitation conditions to form a precipitate containing calcium carbonate containing vaterite on the surface of the aggregate.

[0154] In some embodiments, a method for forming calcium carbonate containing vaterite, (i) A step of calcining limestone to form a gas stream containing lime and carbon dioxide, (ii) Dissolving lime in an aqueous solution of an N-containing inorganic salt under one or more dissolution conditions to produce a first aqueous solution containing a calcium salt and a gas stream containing ammonia, (iii) recovering the gas stream containing carbon dioxide and the gas stream containing ammonia, and subjecting the gas stream to a cooling process under one or more cooling conditions to condense a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, or a combination thereof, (iv) The step of adding aggregate to the first aqueous solution, (v) The first aqueous solution containing a calcium salt and the aggregate are treated with a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, or a combination thereof under one or more precipitation conditions to form a precipitate containing calcium carbonate containing vaterite on the surface of the aggregate. A method is provided that includes this.

[0155] In some embodiments of the aforementioned embodiments, the second aqueous solution further comprises ammonium carbamate. It should be understood that a precipitate containing calcium carbonate may form on the surface of the aggregate, while some precipitate may form in the aqueous solution, and this precipitate is separated from the supernatant solution along with the activated aggregate. In some embodiments, the amount of the first aqueous solution containing the calcium salt in the precipitation reactor may be optimized to selectively precipitate reactive vaterite on the surface of the aggregate, or to selectively precipitate the precipitate in the aqueous solution, or both. In the aforementioned methods and systems, the precipitate containing calcium carbonate comprises reactive vaterite. In the aforementioned methods and systems, the aggregate may be fine aggregate or coarse aggregate. In some embodiments of the aforementioned methods and systems, the aggregate may be the same limestone used in step (i) of the process, or a crushed form of the limestone from step (i).

[0156] In some embodiments, the gas exiting the precipitation reactor (shown as “scrubbed gas” in Figures 1-3) is directed to a gas treatment unit for the scrubbing process. The mass equilibrium and apparatus design for the gas treatment unit may vary depending on the gas characteristics. In some embodiments, the gas treatment unit may incorporate an HCl scrubber to absorb CO2 and recover small amounts of NH3 in the exhaust gas stream that may be carried by the gas from the precipitation step. The NH3 is then removed by the HCl solution. NH3 (gas) + HCl (aqueous solution) → NH4Cl (aqueous solution) It can be captured via.

[0157] The NH4Cl (aqueous solution) derived from the HCl scrubber can be recycled back into dissolution step A.

[0158] In some embodiments, an ammonia-containing exhaust gas stream (indicated as “scrubbed gas” in Figures 1-3) can be subjected to a scrubbing process, where the ammonia-containing exhaust gas stream is scrubbed with carbon dioxide and water from an industrial process to produce an ammonia solution. The inflow into the scrubber may be reactor waste gas containing carbon dioxide (CO2(gas)), ammonia (NH3(gas)), and fresh makeup water (or some other dilution water stream). The outflow may be a slipstream of the scrubber's recirculated fluid (e.g., H3N-CO2(aqueous solution) or carbamate), which may be returned to the main reactor for contact with carbon dioxide and precipitate as needed. The pH of the system can be controlled by adjusting the flow rate of CO2(gas) into the scrubber. The conductivity of the system can be controlled by adding dilution makeup water to the scrubber. The volume can be kept constant by using a level detector on the scrubber or its reservoir. Ammonia is a basic gas, while carbon dioxide gas is an acidic gas. In some embodiments, acidic and basic gases can be ionized to increase their solubility.

[0159] I don't want to be bound by any particular theory, but here's the response: NH3 (aqueous solution) + CO2 (aqueous solution) + H2O → HCO3 - +NH4 + However, this is intended to occur within the scrubber.

[0160] A first aqueous solution containing a calcium salt, when brought into contact with a gas stream containing CO2 gas and optionally NH3 gas (or with a second aqueous solution) under one or more precipitation conditions, produces a precipitate of calcium carbonate. One or more precipitation conditions that form stable or reactive vaterite or PCC in this process are described below herein.

[0161] In some embodiments, the precipitate comprises stable vaterite and / or reactive vaterite or PCC. “Stable vaterite” or its grammatical equivalent, as used herein, comprises vaterite that does not convert to aragonite or calcite during and / or after the dissolution-reprecipitation process in water. “Reactive vaterite” or “activated vaterite” or its grammatical equivalent, as used herein, comprises vaterite that forms aragonite during and / or after the dissolution-reprecipitation process in water. “Light calcium carbonate” or “PCC” as used herein comprises conventional PCC having high-purity particles of micron size or less. PCC may be any polymorph of calcium carbonate, including, but not limited to, vaterite, aragonite, calcite, or a combination thereof. In some embodiments, PCC has a particle size of nanometers or between 0.001 and 5 microns.

[0162] In some embodiments, vaterite in the precipitate and / or on the surface of the aggregate may be formed under appropriate conditions such that the vaterite is reactive during the dissolution and precipitation process in water (during cementation) and converts to aragonite. Aragonite can impart one or more unique characteristics to the product, including, but not limited to, high compressive strength, a complex micro-network structure, and a neutral pH. In some embodiments, vaterite in the precipitate may be formed under appropriate conditions such that the vaterite is stable and can be used as a filler in various applications. In some embodiments, PCC in the precipitate may be formed under appropriate conditions such that the PCC is highly pure and has very small particle sizes.

[0163] The precipitate containing reactive vaterite (including, as specified, solids as described herein) is converted to aragonite, sets, and hardens into a cement product (shown as product (A) in Figures 1-3), and the solid can be incorporated into the cement product. This offers the additional advantage of reducing one step of removing the solid, minimizing the loss of base, e.g., NH4Cl, eliminating a potential waste stream, thereby increasing efficiency and improving the economic aspects of the process. In some embodiments, the solid impurities do not adversely affect the conversion from vaterite to aragonite and / or reactivity. In some embodiments, the solid impurities do not adversely affect the strength of the cement product (e.g., compressive or flexural strength).

[0164] In some embodiments, the methods and systems provided herein further include the step of separating the precipitate from the aqueous solution by dehydration (step D in Figures 1-3) to form a calcium carbonate cake (as shown in Figures 1-3). The calcium carbonate cake may be rinsed and dried as needed (step E in Figures 1-3). The dried precipitate or the dried calcium carbonate cake can then be used to produce cement products or non-cement products (as shown in product (B) in Figures 1-3). In some embodiments, the calcium carbonate cake is ammonium (NH4) + ) ions, sulfur ions, and / or chloride (Cl - ) It may contain ionic impurities (e.g., 1-2% by weight or more). Rinsing the calcium carbonate cake may remove some or all of the ammonium salts and / or sulfur compounds, while simultaneously leaving a diluted concentration of ammonium salts (in the supernatant), which may need to be concentrated before being recycled back into the process.

[0165] Methods and systems provided herein can leave residual bases, such as residual nitrogen-containing inorganic or nitrogen-containing organic salts, such as residual ammonium salts, in the supernatant and the precipitate itself after the precipitate has formed. Residual bases, such as residual nitrogen-containing inorganic or nitrogen-containing organic salts, such as residual ammonium salts (e.g., residual NH4Cl), as used herein, include any salts that can be formed by ammonium ions present in the solution, and, but not limited to, halogen ions, such as chloride ions, nitrate ions, or nitrite ions, and sulfur ions, such as sulfate ions, sulfite ions, thiosulfate ions, hydrogen sulfide ions, and the like, including anions. In some embodiments, residual nitrogen-containing inorganic salts include ammonium halides, ammonium sulfate, ammonium sulfite, ammonium hydrogen sulfide, ammonium thiosulfate, ammonium nitrate, ammonium nitrite, or combinations thereof. Various methods for removing residual salts from the supernatant and precipitate and recovering them as needed are provided herein. In some embodiments, the supernatant solution further containing a nitrogen-containing inorganic or nitrogen-containing organic salt, such as a residual ammonium salt (e.g., residual NH4Cl), is recycled to a dissolution reactor for dissolving lime (step A in Figures 1-3).

[0166] The residual base solution obtained from the dewatering and rinsing streams, such as a nitrogen-containing inorganic salt solution or a nitrogen-containing organic salt solution, such as a residual ammonium salt solution (e.g., residual NH4Cl), can be concentrated as needed and then recycled back for lime dissolution. Further bases, such as ammonium chloride and / or ammonia (anhydrous or aqueous solution), can be added to the recycled solution during the process to compensate for the loss of ammonium chloride and to bring the concentration of ammonium chloride to an optimal level.

[0167] In some embodiments, residual nitrogen-containing inorganic or nitrogen-containing organic salt solutions, such as residual ammonium salt solutions (e.g., residual NH4Cl), can be recovered from the supernatant aqueous solution as shown in Figures 1-3 and concentrated using recovery processes, including, but not limited to, pyrolysis, pH adjustment, reverse osmosis, multi-stage flashing, multiple-effect distillation, vapor recompression, distillation, or a combination thereof. Systems configured to perform these processes are commercially available. For example, the pH of the solution can be increased (e.g., by using a strong base such as NaOH). This can shift the equilibrium towards volatile ammonia (NH3 (aqueous solution) / NH3 (gas)). Both the removal rate and the total removal rate could be improved by heating the solution.

[0168] In some embodiments, residual nitrogen-containing inorganic or nitrogen-containing organic salt solutions, such as residual ammonium salt solutions (e.g., residual NH4Cl), can be separated from the precipitate and recovered by a thermal decomposition process. This process can be incorporated into the process shown in Figures 1-3 after the separation of the CaCO3 precipitate (step D) and / or after the step of dried CaCO3 precipitate or powder (step E).

[0169] Typically, solid NH4Cl can decompose into ammonia (NH3) gas and hydrogen chloride (HCl) gas at 338°C. On the other hand, solid CaCO3 decomposes into solid calcium oxide (CaO) and carbon dioxide (CO2) gas at 840°C. NH4Cl (solid) ←→ NH3 (gas) + HCl (gas) CaCO3 (solid) ←→ CaO (solid) + CO2 (gas)

[0170] In some embodiments, residual ammonium salts in the CaCO3 precipitate and / or dried CaCO3 precipitate, such as, but not limited to, ammonium chloride, ammonium sulfate, ammonium sulfite, ammonium hydrogen sulfide, ammonium thiosulfate, ammonium nitrate, ammonium nitrite, or combinations thereof, can be removed by thermal decomposition at temperatures between 338 and 840°C. This can be done during the normal drying process of the filtered cake and / or as a second post-drying heat treatment. A temperature range is desirable that decomposes the residual ammonium salts in the precipitate while preserving the cement properties of the reactive vaterite in the precipitate, so that the reactive vaterite remains as reactive vaterite after heating and is successfully converted to aragonite after being combined with water to form a cement product.

[0171] In some embodiments of the aforementioned aspects and embodiments, the step of removing residual N-containing inorganic or N-containing organic salts, such as ammonium salts, from the precipitate and recovering them as necessary includes heating the precipitate between approximately 290-375°C, or between approximately 300-360°C, or between approximately 300-350°C, or between approximately 310-345°C, or between approximately 320-345°C, or between approximately 330-345°C, or between approximately 300-345°C to evaporate the residual N-containing inorganic or N-containing organic salts from the precipitate and recovering them by condensing them as necessary.

[0172] In some embodiments of the aforementioned aspects and embodiments, the step of removing residual N-containing inorganic or N-containing organic salts, such as residual ammonium salts, from the precipitate and recovering them as necessary includes heating the precipitate for a period of time exceeding about 10 minutes, or exceeding about 15 minutes, or exceeding about 5 minutes, or for a period of time between about 10 minutes and about 1 hour, or between about 10 minutes and about 1.5 hours, or between about 10 minutes and about 2 hours, or between about 10 minutes and about 5 hours, or between about 10 minutes and about 10 hours.

[0173] In some embodiments, the precipitate is dehydrated (to remove the supernatant aqueous solution), dried to remove water (for example, by heating to about 100°C or above), and then subjected to the aforementioned heating step to remove residual nitrogen-containing inorganic or nitrogen-containing organic salts, such as residual ammonium salts, and recovered as necessary. In some embodiments, the precipitate is partially dehydrated (to remove the bulk of the supernatant aqueous solution), partially dried to remove water (or the drying step is avoided), and then subjected to the heating step to remove residual nitrogen-containing inorganic or nitrogen-containing organic salts, such as residual ammonium salts, and recovered as necessary. In some embodiments, reactive vaterites in the precipitate remain as reactive vaterites after heating. In some embodiments of the above embodiments, it is desirable that reactive vaterites in the precipitate remain as reactive vaterites, and thus the cement properties of the material are preserved. In some embodiments, ammonium salts evaporate from the precipitate in forms including ammonia gas, hydrogen chloride gas, chlorine gas, or a combination thereof. The applicants have found that, in some embodiments, maintaining a combination of heating temperature and heating duration can be crucial for removing ammonium salts from the precipitate while simultaneously preserving the cement properties of the reactive vaterite material. Conventionally, reactive vaterite is highly unstable and readily converts to aragonite / calcite. However, the applicants have found a temperature range in which residual ammonium salts are removed from the material by combining the heating duration, as needed, with a heating duration that minimizes the conversion of reactive vaterite. In some embodiments of the aforementioned embodiments, after the removal of residual N-containing inorganic or N-containing organic salts, such as residual ammonium salts, the vaterite in the precipitate remains as reactive vaterite, which, when combined with water, converts to aragonite (dissolve-reprecipitation process), which then sets and cementifies to form a cement product. The cement product thus formed has minimal or no chloride content and is completely free of ammonia or sulfurous odors. In some embodiments, the chloride content is approximately at or below the ASTM acceptable limit for cement products.

[0174] In some embodiments, the heating period and, as needed, the temperature conditions described above can be combined with pressure conditions that provide a driving force to improve the thermodynamics of the decomposition of residual nitrogen-containing inorganic or nitrogen-containing organic salts, such as residual ammonium salts. For example, heating of a precipitate can be carried out in a system where the headspace pressure is lower than atmospheric pressure. A pressure lower than atmospheric pressure can provide a driving force for heating reactions involving gas-phase products (e.g., but not limited to ammonia gas, hydrogen chloride gas, chlorine gas, or a combination thereof) by reducing the partial pressure of reactants in the gas phase. Another advantage of operating under reduced pressure or vacuum is that at lower pressures, some sublimation reactions can occur at lower temperatures, thereby improving the energy requirements of the heating reaction.

[0175] In some embodiments of the pyrolysis process described above, the separated ammonium chloride in the form of ammonia gas and HCl gas can be recovered for reuse by recrystallizing the combination of gases generated thermally or by absorbing the gases into an aqueous medium. Together, these mechanisms can yield an NH4Cl product that can be sufficiently concentrated for reuse in the processes shown in Figures 1-3.

[0176] In some embodiments, the ammonium salt can be separated and recovered in the aforementioned process by adjusting the pH from the ammonium salt to generate NH3 gas. This process can be incorporated into the process shown in Figures 1-3 when separating the CaCO3 cake. The final pH of the water in the filtered cake can typically be about 7.5. At this pH, NH4 + (pKa=9.25) can be the main species. Increasing the pH of this water can shift the acid-base equilibrium, as described in the following equation, toward NH3 gas. NH4 + ←→ H + +NH3 (gas)

[0177] Any alkaline source can be used to increase the pH of the filtered cake water. In some embodiments, an aqueous solution of calcium oxide and / or calcium hydroxide or lime slurry can provide a highly alkaline source. In some embodiments, an aqueous fraction of lime can be integrated into the rinsing step of the dewatering process (e.g., the filtered cake step) to increase the system's pH and drive the generation of NH3 gas. Since ammonia is quite soluble in water, heat and / or vacuum pressure can be applied to further drive equilibrium toward the gas phase. Ammonia can be recovered for reuse by recrystallizing ammonia with chloride or by absorbing ammonia into an aqueous medium. Together, these mechanisms can result in an ammonia solution or NH4Cl product that can be sufficiently concentrated for reuse in the processes shown in Figures 1-3.

[0178] The calcium carbonate cake (e.g., vaterite or PCC) can be sent to a dryer to form a calcium carbonate powder containing stable or reactive vaterite or PCC (step E in Figure 1). The powder form of the precipitate containing stable or reactive vaterite or PCC can be further used in applications for forming the product as described herein. The cake can be dried using any drying technique known in the art, for example, a fluidized bed dryer or a swirl fluidizer (swirl It can be dried using a fluidizer. The resulting solid powder can then be mixed with additives to produce the various products described herein. In some embodiments, a slurry form containing reduced water or a cake form of the precipitate is used directly to form products such as building panels, as described herein.

[0179] If necessary, the separated solid can be dried and used as a pozzolanic agent. In some embodiments, the separated solid can be added to a powder form of the vaterite-containing precipitate as a filler or auxiliary cementing material.

[0180] In the systems provided herein, separation or dehydration step D may be performed at a separation station. The precipitate may be stored in the supernatant for a certain period of time after precipitation and before separation. For example, the precipitate may be stored in the supernatant at a temperature in the range of 1°C to 40°C, for example, 20°C to 25°C, for a period of time ranging from a few minutes to several hours, 1 to 1000 days or longer, for example, 1 to 10 days or longer. Separation or dehydration of the precipitate from the precipitation reaction mixture may be achieved using any of several convenient methods, including drainage (e.g., drainage after gravity settling of the precipitate), decantation, filtration (e.g., gravity filtration, vacuum filtration, filtration using forced air), centrifugation, pressurization, or any combination thereof. Separation of bulk water from the precipitate produces a wet cake of the precipitate, i.e., dehydrated precipitate. Liquid-solid separators, such as the Epuramat Extreme-Separator ("ExSep"), the Xerox PARC spiral separator, or a modified version of either the Epuramat ExSep or the Xerox PARC spiral separator, can be useful for separating precipitates from precipitation reactions.

[0181] In some embodiments, the resulting dehydrated precipitate, for example, a wet cake material (after removing N-containing salts, for example, thermally), can be used directly to produce product (A) as described herein. For example, a wet cake of the dehydrated precipitate is mixed with one or more additives as described herein and spread on a conveyor belt, where the reactive vaterite or PCC in the precipitate is converted to aragonite, condenses, and hardens (ammonium salts are thermally removed). The hardened material is then cut into desired shapes, for example, boards or panels as described herein. In some embodiments, the wet cake is poured onto a paper sheet at the top of the conveyor belt. Another sheet of paper can be placed on top of the wet cake and then compressed to remove excess water. After the precipitate has condensed and hardened (conversion from vaterite to aragonite), the material is cut into desired shapes, for example, cement paneling and drywall. In some embodiments, the amounts of one or more additives may be optimized according to the desired time required for the conversion from vaterite to aragonite (as described below). For example, in some applications, a rapid conversion of the material may be desirable, while in certain other cases, a slow conversion may be desirable. In some embodiments, the wet cake may be heated on a conveyor belt to accelerate the conversion from vaterite to aragonite. In some embodiments, the wet cake may be poured into a mold of a desired shape, and the mold may then be heated in an autoclave to accelerate the conversion from vaterite to aragonite (and to remove residual salts). Thus, continuous flow processes, batch processes, or semi-batch processes are all well within the scope of the present invention.

[0182] In some embodiments, after separating the baterite-containing precipitate from the precipitation reaction, it is washed with fresh water and then placed in a filtration compressor to produce a filtration cake containing 30-60% solid. This filtration cake is then mechanically compressed in a mold using any convenient means, such as a hydraulic compressor, at a sufficient pressure in the range of 5-5000 psi, for example, 1000-5000 psi, to produce formed solids, such as rectangular bricks. These resulting solids are then cured, for example, by being stored outdoors or placed in a chamber exposed to high levels of humidity and heat. These cured solids are then used as building material itself or crushed to produce aggregate.

[0183] In a process involving the use of temperature and pressure, the dehydrated precipitate cake can be dried. The cake is then exposed to a combination of re-watering and high temperature and / or high pressure for a certain period of time. The combination of the amount of water added and returned, temperature, pressure, and exposure time, as well as the thickness of the cake, can vary depending on the composition of the starting material and the desired result.

[0184] Several different ways of exposing the material to temperature and pressure are described herein, but it will be recognized that any convenient method may be used. The thickness and size of the cake may be adjusted as desired, but the thickness may vary in some embodiments from 0.05 inches to 5 inches, e.g., 0.1 to 2 inches, or 0.3 to 1 inch. In some embodiments, the cake may be 0.5 inches to 6 feet or thicker. The cake is then exposed to high temperature and / or high pressure for a given time by any convenient method, e.g., using a heated platen in a platen compressor. For example, the heat to raise the temperature for the platen can be provided by heat derived from an industrial waste gas stream, e.g., a flue gas stream. The temperature may be any suitable temperature, but generally, higher temperatures are desirable for thicker cakes, and examples of temperature ranges are 40 to 150°C, e.g., 60 to 120°C, e.g., 70 to 110°C, or 80 to 100°C. Similarly, the pressure may be any pressure suitable for producing the desired result, and exemplary pressures include 1,000 to 100,000 pounds per square inch (psi), including 2,000 to 50,000 psi, 2,000 to 25,000 psi, 2,000 to 20,000 psi, or 3,000 to 5,000 psi. Finally, the time for the cake to be compressed may be any appropriate time, e.g., 1 to 100 seconds, or 1 to 100 minutes, or 1 to 50 minutes, or 2 to 25 minutes, or 1 to 10,000 days. The resulting hard tablets can then be cured as needed, for example, by storing them outdoors or by placing them in a chamber exposed to high levels of humidity and heat. These cured hard tablets can then be used as building materials themselves or crushed to produce aggregates.

[0185] Another method for providing temperature and pressure is the use of a compressor. Using a suitable compressor, such as a platen compressor, it is possible to provide a desired temperature (for example, by using heat supplied by flue gas or by other steps in the process for producing the precipitate, such as by electrochemical methods) and pressure for a desired time. A set of rollers can be used in a similar manner.

[0186] Another way to expose the cake to high temperature and pressure is by using an extruder, such as a screw extruder. The barrel of the extruder can be equipped, for example, by having a jacket to achieve high temperature, and this high temperature can be supplied, for example, by exhaust gas. Extrusion can be used as a means of preheating and drying the raw material before the compression operation. Such compression can be carried out by using a compression die, through rollers, through rollers having a molded press die (which can provide aggregate of virtually any desired shape), between belts that provide compression as they move, or by any other convenient method. Alternatively, an extruder can be used to extrude the material through a die, exposing the material to pressure as it is extruded through the die to give it any desired shape. In some embodiments, the carbonate precipitate is mixed with fresh water and then placed in the feed section of a rotary screw extruder. The die of the extruder and / or outlet can be heated to further assist the process. The rotation of the screw transports the material along its length and compresses the material as the height of the screw flite decreases. The screw and barrel of the extruder may further include vents in the barrel, with the reduced pressure zone of the screw coinciding with the vent opening in the barrel. In particular, in the case of a heated extruder, these vented areas can release steam from the material being conveyed, thereby removing water from the material.

[0187] Next, the material transported by the screw is extruded through a die section that further compresses and shapes the material. Typical die openings can be circular, elliptical, square, rectangular, trapezoidal, etc., but any shape desired for the final aggregate can be produced by adjusting the shape of the opening. The material exiting the die can be cut to any convenient length by any convenient method, for example, by a fly knife. The use of a heated die section can further aid in product formation by accelerating the transition from carbonate minerals to a hard, stable form. In the case of binders, a heated die can also be used to harden or solidify the binder. In heated die sections, temperatures generally range from 100°C to 600°C.

[0188] In further embodiments, the precipitate can be used for the fabrication of form-in-place structures. For example, roads, pavement areas, or other structures can be fabricated from the precipitate by, for example, applying a layer of the precipitate to a substrate, such as the ground or subgrade, and then hydrating the precipitate by exposure to water that is naturally applied, such as in the form of rain, or by irrigation. Through hydration, the precipitate solidifies into the desired form-in-place structure, such as a road or pavement area. The process may be repeated, for example, if a thicker layer of the form-in-place structure is desired.

[0189] In some embodiments, the formation of the precipitate and the product takes place within the same facility. In some embodiments, the precipitate is formed in one facility and transported to another facility to produce the final product. The precipitate may be transported in slurry form, wet cake form, or dry powder form.

[0190] In some embodiments, the resulting dehydrated precipitate obtained from the separation station is dried in a drying station to produce a powder form of the precipitate containing stable or reactive vaterite or PCC. Drying can be achieved by air-drying the precipitate. In certain embodiments, drying is achieved by freeze-drying (i.e., lyophilization), where the precipitate is frozen, the ambient pressure is reduced, and enough heat is applied to directly sublimate the frozen water in the precipitate into gas. In yet another embodiment, the precipitate is spray-dried to dry it, where the liquid containing the precipitate is dried by being supplied via a hot gas (e.g., a waste gas stream from a power plant), the supply liquid is pumped through an atomizer into the main drying chamber, and the hot gas passes in parallel or countercurrent relative to the atomizer. Depending on the specific drying protocol of the system, the drying station may include a filtration element, a freeze-drying structure, a spray-drying structure, etc. In some embodiments, the precipitate can be dried by a fluidized bed dryer. In certain embodiments, where appropriate, waste heat from a power plant or similar operation can be used to carry out the drying step. For example, in some embodiments, the drying product is produced by using high temperature (e.g., derived from waste heat of a power plant), pressure, or a combination thereof. After drying the precipitate, the substance can then be heated at a high temperature to remove residual nitrogen-containing salts, such as residual ammonium salts, as described herein.

[0191] The supernatant or slurry of precipitated material resulting from the precipitation process can also be treated as desired. For example, the supernatant or slurry can be returned to the first aqueous solution or to another location. In some embodiments, the supernatant can be contacted with a gas stream containing CO2 and optionally ammonia gas as described herein to capture further CO2. For example, in embodiments where the supernatant is to be returned to the precipitation reactor, the supernatant can be contacted with a gas stream of CO2 and optionally ammonia gas in a manner sufficient to increase the concentration of carbonate ions present in the supernatant. As previously stated, the contact can be carried out using any convenient protocol. In some embodiments, the supernatant has an alkaline pH, and the contact with CO2 gas is carried out in a manner sufficient to reduce the pH to a range of pH 5 to 9, pH 6 to 8.5, or pH 7.5 to 8.7.

[0192] In some embodiments, the precipitate produced by the methods provided herein is used as a building material (e.g., building material for certain types of artificial structures such as buildings, roads, bridges, and dams) so that CO2 is effectively captured in the constructed environment. Any artificial structure such as foundations, parking structures, houses, office buildings, commercial offices, government buildings, and infrastructure (e.g., scaffolding for sidewalks, roads, bridges, overpasses, walls, gates, fences, and poles) is considered part of the constructed environment. Mortar is used to bind building blocks (e.g., bricks) together and to fill the gaps between building blocks. Among other uses, mortar can also be used to repair existing structures (e.g., to replace parts where the original mortar is damaged or eroded).

[0193] In some embodiments, a powdered form of the precipitate containing reactive vaterite is used as cement, which is converted to aragonite (dissolve-reprecipitate process), then set and hardens after being mixed with water. In some embodiments, the precipitate containing reactive vaterite on the surface of the aggregate is converted to aragonite (dissolve-reprecipitate process) after being mixed with water, and then binds to the cement that is mixed together.

[0194] In some embodiments, the aggregate itself is produced from the resulting precipitate. In such embodiments, where the drying process produces particles of the desired size, there is little or no additional processing required to produce the aggregate. In yet another embodiment, further processing of the precipitate is carried out to produce the desired aggregate. For example, the precipitate can be combined with fresh water in a manner sufficient for the precipitate to form a solid product, where reactive vaterite is converted to aragonite. By controlling the water content of the wet material, the porosity of the final aggregate, as well as its final strength and density, can be controlled. Typically, the wet cake may be 40–60% by volume of water. For denser aggregates, the wet cake may be <50% water, and for less dense cakes, the wet cake may be >50% water. The solid product then produced after hardening can be mechanically processed, e.g., crushed or otherwise broken down, and sorted to produce aggregate with desired characteristics, e.g., size, specific shape. In these processes, the setting and mechanical processing steps can be carried out substantially continuously or at intervals of time. In certain embodiments, large volumes of precipitate can be stored in an open environment where the precipitate is exposed to the atmosphere. In the condensation step, the precipitate can be conveniently irrigated with fresh water or left to rain naturally to produce a condensation product. The condensation product can then be mechanically processed as described above. After the formation of the precipitate, it is processed to produce the desired aggregate. In some embodiments, the precipitate can be placed outdoors, where rainwater can be used as a fresh water source to induce a stabilization reaction in the rainwater, hardening the precipitate and forming the aggregate.

[0195] After removing residual salts as necessary, the precipitate or precipitated material formed in the methods and systems herein comprises vaterite or PCC. Stable vaterite includes vaterite that does not convert to aragonite or calcite during and / or after the dissolution-reprecipitation process. Reactive vaterite or activated vaterite includes vaterite that forms aragonite during and / or after the dissolution-reprecipitation process. In some embodiments, the formed PCC is in vaterite form. In some embodiments, the methods described herein further include the step of contacting the precipitated material (in dry or wet form) with water to convert the reactive vaterite to aragonite. In some embodiments, stable vaterite, even when contacted with water, does not convert to aragonite and remains in vaterite form or converts to calcite over a long period of time.

[0196] Typically, when calcium carbonate precipitates, amorphous calcium carbonate (ACC) may precipitate first, and can be converted into one or more of its three more stable phases (vaterite, aragonite, or calcite). A thermodynamic driving force may exist to convert the unstable phase to a more stable one. For this reason, the calcium carbonate phase is converted in the order of ACC to vaterite, aragonite, and calcite, where intermediate phases may or may not be present. During this conversion, excess energy is released, as shown in Figure 8. This intrinsic energy can be used to generate a strong aggregation tendency and surface interactions that can lead to coagulation and solidification or cementation. It should be understood that the values ​​reported in Figure 8 are well known in the art and can vary.

[0197] Methods and systems provided herein generate or isolate precipitates in vaterite form, or in PCC form, which may exist in vaterite, aragonite, or calcite form. The precipitate may be in wet form, slurry form, or dry powder form. The precipitate may have a stable vaterite form that does not readily convert to any other polymorph, or it may have a reactive vaterite form that converts to aragonite form upon dissolution and reprecipitation. The aragonite form may not further convert to the more stable calcite form. Products containing precipitates in aragonite form exhibit one or more unexpected properties, including, but not limited to, high compressive strength, high porosity (low density or light weight), neutral pH (useful as artificial reefs, as described below), and a fine network structure.

[0198] In addition to vaterite, small amounts of other polymorphs of calcium carbonate that may be present in carbonate-containing precipitates include, but are not limited to, amorphous calcium carbonate, aragonite, calcite, vaterite precursors, aragonite precursors, less stable intermediate phases than calcite, polymorphs between these polymorphs, or combinations thereof.

[0199] Vaterite can exist in monodisperse or aggregated forms and may be spherical, elliptic, plate-like, or hexagonal. Vaterite typically has a hexagonal crystalline structure and forms polycrystalline spherical particles during growth. Precursors of vaterite include vaterite nanoclusters, and precursors of aragonite include submicron to nanoclusters of acicular aragonite. When present in a composition with vaterite, aragonite may be acicular, cylindrical, or orthorhombic crystals. When present in a composition with vaterite, calcite may be cubic, fusiform, or hexagonal crystals. Intermediate phases less stable than calcite may be phases between vaterite and calcite, between vaterite precursors and calcite, between aragonite and calcite, and / or between aragonite precursors and calcite.

[0200] Conversion between calcium carbonate polymorphs can occur via solid-state transitions, which may be mediated by solution, or both. In some embodiments, solution-mediated conversion requires less energy than thermally activated solid-state transitions, and therefore the conversion is solution-mediated. Vaterite is metastable, and differences in the thermodynamic stability of calcium carbonate polymorphs may manifest as differences in solubility, where the least stable phase is the most soluble. Therefore, vaterite readily dissolves in solution and can be conveniently converted to a more stable polymorph, such as aragonite. In polymorphic systems like calcium carbonate, two dynamic processes—dissolution of the metastable phase and growth of the stable phase—can coexist in solution simultaneously. In some embodiments, aragonite crystals can grow while vaterite is undergoing dissolution in an aqueous medium.

[0201] In one embodiment, reactive vaterite can be activated so that it follows a pathway to aragonite and not to calcite during the dissolution-reprecipitation process. In some embodiments, a composition containing reactive vaterite is activated such that, after the dissolution-reprecipitation process, aragonite formation is enhanced and calcite formation is inhibited. Activation of a composition containing reactive vaterite can control aragonite formation and crystal growth. Activation of a composition containing vaterite can be achieved by various processes. Various examples of vaterite activation, including but not limited to nucleation activation, thermal activation, mechanical activation, chemical activation, or combinations thereof, are described herein. In some embodiments, vaterite is activated through various processes so that aragonite formation and its morphology, as well as crystal growth, can be controlled during the reaction of the composition containing vaterite with water. The formed aragonite provides higher tensile strength and fracture resistance to products formed from reactive vaterite.

[0202] In some embodiments, reactive vaterite can be activated by mechanical means as described herein. For example, a composition containing reactive vaterite can be activated by creating surface defects on the vaterite composition so as to accelerate the formation of aragonite. In some embodiments, the activated vaterite is ball-milled reactive vaterite or reactive vaterite having surface defects such as to promote the aragonite formation pathway.

[0203] Compositions containing reactive vaterite may also be activated by chemical or nucleation activation of the vaterite composition. Such chemical or nucleation activation may be provided by one or more aragonite seed crystals, inorganic additives, or organic additives. The aragonite seed crystals present in the compositions provided herein may be obtained from natural or synthetic sources. Natural sources include, but are not limited to, rocky reef sands, limestone, the shells of bladders, gastropods, mollusks, and hard skeletal materials of certain freshwater and marine invertebrates, including the calcareous endoskeletons of warm-water and cold-water corals, as well as pearls, rocks, sediments, and ore minerals (e.g., serpentine). Synthetic sources include, but are not limited to, precipitated aragonite formed from, for example, sodium carbonate and calcium chloride, or aragonite formed by the conversion of vaterite to aragonite, such as the converted vaterite described herein.

[0204] In some embodiments, the inorganic or organic additives in the compositions provided herein may be any additives that activate the reactive vaterite. Some examples of inorganic or organic additives in the compositions provided herein, but not limited to, include sodium decyl sulfate, lauric acid, sodium salt of lauric acid, urea, citric acid, sodium salt of citric acid, phthalic acid, sodium salt of phthalic acid, taurine, creatine, glucose, poly(n-vinyl-1-pyrrolidone), aspartic acid, sodium salt of aspartic acid, magnesium chloride, acetic acid, sodium salt of acetic acid, glutamic acid, sodium salt of glutamic acid, strontium chloride, gypsum, lithium chloride, sodium chloride, glycine, anhydrous sodium citrate, sodium bicarbonate, magnesium sulfate, magnesium acetate, sodium polystyrene, sodium dodecyl sulfonate, polyvinyl alcohol, or combinations thereof. In some embodiments, inorganic or organic additives in the compositions provided herein include, but are not limited to, taurine, creatine, poly(n-vinyl-1-pyrrolidone), lauric acid, sodium lauric acid, urea, magnesium chloride, acetic acid, sodium acetic acid, strontium chloride, magnesium sulfate, magnesium acetate, or combinations thereof. In some embodiments, inorganic or organic additives in the compositions provided herein include, but are not limited to, magnesium chloride, magnesium sulfate, magnesium acetate, or combinations thereof.

[0205] While not adhering to any particular theory, it is intended that aragonite formation can be controlled during the dissolution-reprecipitation process of activated reactive vaterite by ball milling or by the activation of vaterite by adding aragonite seed crystals, inorganic or organic additives, or a combination thereof, including, but not limited to, control of properties such as polymorphism, morphology, particle size, bridging, aggregation, solidification, aggregation, sedimentation, crystal structure analysis, inhibiting growth along certain crystal faces, enabling growth along certain crystal faces, or a combination thereof. For example, aragonite seed crystals, inorganic or organic additives may selectively target the morphology of aragonite, inhibit calcite growth, and promote aragonite formation, which may generally be kinetically undesirable.

[0206] In some embodiments, one or more inorganic additives may be added to facilitate the conversion of vaterite to aragonite. One or more additives may be added at any step of the process. For example, one or more additives may be added during the contact of a first aqueous solution containing a calcium salt with carbon dioxide gas and optionally ammonia gas or a second aqueous solution, after the contact of a first aqueous solution containing a calcium salt with carbon dioxide gas and optionally ammonia gas or a second aqueous solution, during the precipitation of the precipitate, after the precipitation of the precipitate in the slurry, in the slurry after the dewatering of the precipitate, in the powder after the slurry has dried, in the aqueous solution to be mixed with the powdered precipitate, or in the slurry prepared from the powdered precipitate using water, or in any combination thereof. In some embodiments, the water used in the process to prepare the precipitate may already contain one or more additives or one or more additive ions. For example, if seawater is used in the process, the additive ions may already be present in the seawater.

[0207] In some embodiments of the method described above, the amount of one or more additives added during the process is greater than 0.1% by weight, or greater than 0.5% by weight, or greater than 1% by weight, or greater than 1.5% by weight, or greater than 1.6% by weight, or greater than 1.7% by weight, or greater than 1.8% by weight, or greater than 1.9% by weight, or greater than 2% by weight, or greater than 2.1% by weight, or greater than 2.2% by weight, or greater than 2.3% by weight, or greater than 2.4% by weight, or greater than 2.5% by weight, or greater than 2.6% by weight, or greater than 2.7% by weight, or greater than 2.8% by weight, or greater than 2.9% by weight, or greater than 3% by weight, or greater than 3.5% by weight, or greater than 4% by weight. , or more than 4.5% by weight, or more than 5% by weight, or between 0.5 and 5% by weight, or between 0.5 and 4% by weight, or between 0.5 and 3% by weight, or between 0.5 and 2% by weight, or between 0.5 and 1% by weight, or between 1 and 3% by weight, or between 1 and 2.5% by weight, or between 1 and 2% by weight, or between 1.5 and 2.5% by weight, or between 2 and 3% by weight, or between 2.5 and 3% by weight, or between 0.5% by weight, or 1% by weight, or 1.5% by weight, or 2% by weight, or 2.5% by weight, or 3% by weight, or 3.5% by weight, or 4% by weight, or 4.5% by weight, or 5% by weight. In some embodiments of the method described above, the amount of one or more additives added during the process is between 0.5 and 3% by weight or between 1.5 and 2.5% by weight.

[0208] In some embodiments, the precipitate is in powder form. In some embodiments, the precipitate is in dry powder form. In some embodiments, the precipitate is disordered, or not in an ordered arrangement, or in powder form. In some further embodiments, the precipitate is in a partially or fully hydrated form. In some further embodiments, the precipitate is present in saline or freshwater. In some further embodiments, the precipitate is present in water containing sodium chloride. In some further embodiments, the precipitate is present in water containing alkaline earth metal ions, such as, but not limited to, calcium, magnesium, etc. In some embodiments, the precipitate is not for medical use or for medical procedures.

[0209] Products derived from the compositions or precipitates provided herein exhibit one or more properties such as high compressive strength, high durability, high porosity (lightweight), high flexural strength, and lower maintenance costs. In some embodiments, compositions or precipitates containing reactive vaterite that condense and harden when combined with water have a compressive strength of at least 3 MPa (megapascals), or at least 7 MPa, or at least 10 MPa, or in some embodiments, between 3 and 30 MPa, or between 14 and 80 MPa, or between 14 and 35 MPa.

[0210] In the aforementioned embodiments and some embodiments of the model, the composition or precipitate contains at least 10 w / w% vaterite, or at least 20 w / w% vaterite, or at least 30 w / w% vaterite, or at least 40 w / w% vaterite, or at least 50 w / w% vaterite, or at least 60 w / w% vaterite, or at least 70 w / w% vaterite, or at least 80 w / w% vaterite, or at least 90 w / w% vaterite, or at least 95 w / w% vaterite, or at least 99 w / w% vaterite, or 10 w / w% to 99 w / w% vaterite, or 10 w / w% to 90 w / w% vaterite, or 10 w / w% to 80 w / w% vaterite, or 10 w / w% to 70 w / w% vaterite, or 10 w / w% to 60 w / w% vaterite, or 10 w / w% to 50 w / w% vaterite, or 10 w / w% to 40 w / w% vaterite, or 10 w / w% to 30 w / w% vaterite, or 10 w / w% to 20 w / w% vaterite, or 20 w / w% to 99 w / w% vaterite, or 20 w / w Vaterite of w / w%~95 w / w%, or vaterite of 20 w / w%~90 w / w%, or vaterite of 20 w / w%~75 w / w%, or vaterite of 20 w / w%~50 w / w%, or vaterite of 30 w / w%~99 w / w%, or vaterite of 30 w / w%~95 w / w%, or vaterite of 30 w / w%~90 w / w%, or vaterite of 30 w / w%~75 w / w%, or vaterite of 30 w / w%~50 w / w%, or vaterite of 40 w / w%~99 w / w%, or vaterite of 40 w / w%~95 w / w%, or 40w / w%~90w / w% vaterite, or 40w / w%~75w / w% vaterite, or 50w / w%~99w / w% vaterite, or 50w / w%~95w / w% vaterite, or 50w / w%~90w / w% vaterite, or 50w / w%~75w / w% vaterite, or 60w / w%~99w / w% vaterite, or 60w / w%~95w / w% vaterite, or 60w / w%~90w / w% vaterite, or 70w / w%~99w / w% vaterite, or 70w / w%~95w / w% vaterite,Or 70 w / w% to 90 w / w% vaterite, or 80 w / w% to 99 w / w% vaterite, or 80 w / w% to 95 w / w% vaterite, or 80 w / w% to 90 w / w% vaterite, or 90 w / w% to 99 w / w% vaterite, or 10 w / w% vaterite, or 20 w / w% vaterite, or 30 w / w% vaterite, Or it may include 40 w / w% vaterite, or 50 w / w% vaterite, or 60 w / w% vaterite, or 70 w / w% vaterite, or 75 w / w% vaterite, or 80 w / w% vaterite, or 85 w / w% vaterite, or 90 w / w% vaterite, or 95 w / w% vaterite, or 99 w / w% vaterite. Vaterite can be stable vaterite, reactive vaterite, or PCC.

[0211] In the embodiments described above and in some embodiments of the embodiments described above, the precipitate containing reactive vaterite that sets and hardens (i.e., converts to aragonite) after being combined with water, or the precipitate containing stable vaterite after being mixed with cement and water, sets and hardens, is at least 3 MPa, at least 7 MPa, at least 14 MPa, or at least 16 MPa, or at least 18 MPa, or at least 20 MPa, or at least 25 MPa, or at least 30 MPa, or at least 35 MPa, or at least 40 MPa, or at least 45 MPa, or at least 50 MPa, or at least 55 MPa, or at least 60 MPa, or at least 65 MPa, or at least 70 MPa, or at least 75 MPa, or at least 80 MPa, or at least 85 MPa, or at least 90 MPa, or at least 95 MPa, or at least 100 MPa, or 3 to 50 MPa, or 3 to 25 MPa, or 3 to 15 MPa, or 3-10 MPa, or 14-25 MPa, or 14-100 MPa, or 14-80 MPa, or 14-75 MPa, or 14-50 MPa, or 14-25 MPa, or 17-35 MPa, or 17-25 MPa, or 20-100 MPa, or 20-75 MPa, or 20-50 MPa, or 20-40 MPa, or 30-90 MPa, or 30-75 MPa, or 30-60 MPa, or 40-90 MPa, or 40-75 MPa, or It has a compressive strength of 50-90 MPa, or 50-75 MPa, or 60-90 MPa, or 60-75 MPa, or 70-90 MPa, or 70-80 MPa, or 70-75 MPa, or 80-100 MPa, or 90-100 MPa, or 90-95 MPa, or 14 MPa, or 3 MPa, or 7 MPa, or 16 MPa, or 18 MPa, or 20 MPa, or 25 MPa, or 30 MPa, or 35 MPa, or 40 MPa, or 45 MPa.For example, in the embodiments described above and in some embodiments of the embodiments described above, the composition and precipitate after coagulation and hardening have compressive strengths of 3 MPa to 25 MPa, or 14 MPa to 40 MPa, or 17 MPa to 40 MPa, or 20 MPa to 40 MPa, or 30 MPa to 40 MPa, or 35 MPa to 40 MPa. In some embodiments, the compressive strength described herein is the compressive strength after 1 day, or 3 days, or 7 days, or 28 days, or 56 days, or longer.

[0212] In some embodiments, the precipitate containing vaterite (stable or reactive) or PCC is a particulate composition having an average particle size of 0.1 to 100 microns. The average particle size (or average particle diameter) can be determined using any conventional particle size determination method, for example, multi-detector laser scattering or laser diffraction or sieving, but not limited to these. In certain embodiments, unimodel or multimodal, such as bimodal or other distributions, may exist. A bimodal distribution can provide smaller reactive particles for the initial reaction while minimizing surface area and thus allowing for a lower liquid / solid mass ratio when the composition is mixed with water.In some embodiments, compositions or precipitates provided herein that include vaterite (stable or reactive) or PCC are 0.1 to 1000 microns, or 0.1 to 500 microns, or 0.1 to 100 microns, or 0.1 to 50 microns, or 0.1 to 20 microns, or 0.1 to 10 microns, or 0.1 to 5 microns, or 1 to 50 microns, or 1 to 25 microns, or 1 to 20 microns, or 1 to 10 microns, or 1 to 5 microns, or 5 to 70 microns, or 5 to 50 microns, or 5 to 20 microns, or 5 to 10 microns, or 10 to 100 microns, or 10 to 50 microns, or 10 to 20 microns, or 10 to 15 microns, or 15 to 50 microns, or 15 to 30 microns, or 15 to 20 microns. Alternatively, it is a particulate composition having an average particle size of 20-50 microns, or 20-30 microns, or 30-50 microns, or 40-50 microns, or 50-100 microns, or 50-60 microns, or 60-100 microns, or 60-70 microns, or 70-100 microns, or 70-80 microns, or 80-100 microns, or 80-90 microns, or 0.1 microns, or 0.5 microns, or 1 micron, or 2 microns, or 3 microns, or 4 microns, or 5 microns, or 8 microns, or 10 microns, or 15 microns, or 20 microns, or 30 microns, or 40 microns, or 50 microns, or 60 microns, or 70 microns, or 80 microns, or 100 microns. For example, in some embodiments, the compositions or precipitates provided herein that include vaterite (stable or reactive) or PCC are particulate matter compositions having an average particle size of 0.1 to 20 microns, or 0.1 to 15 microns, or 0.1 to 10 microns, or 0.1 to 8 microns, or 0.1 to 5 microns, or 1 to 25 microns, or 1 to 20 microns, or 1 to 15 microns, or 1 to 10 microns, or 1 to 5 microns, or 5 to 20 microns, or 5 to 10 microns.In some embodiments, a composition or precipitate containing vaterite (stable or reactive) or PCCs may contain two or more, three or more, four or more, five or more, ten or more, twenty or more, three to twenty, or four to ten particles of different sizes. For example, a composition or precipitate may contain two or more, three or more, or three to twenty particles with particle sizes ranging from 0.1 to 10 microns, 10 to 50 microns, 50 to 100 microns, 100 to 200 microns, 200 to 500 microns, 500 to 1000 microns and / or submicron sizes. In some embodiments, the PCCs in the precipitate may have an average particle size of less than 0.1 microns, for example, between 0.001 and 1 micron or greater. In some embodiments, the PCCs may have a particle size of nanometers.

[0213] In some embodiments, the composition or precipitate containing vaterite (stable or reactive) or PCC may further contain OPC or Portland cement clinker. The amount of Portland cement components may vary, from 10 to 95 w / w%, or 10 to 90 w / w%, or 10 to 80 w / w%, or 10 to 70 w / w%, or 10 to 60 w / w%, or 10 to 50 w / w%, or 10 to 40 w / w%, or 10 to 30 w / w%, or 10 to 20 w / w%, or 20 to 90 w / w%, or 20 to 80 w / w%, or 20 to 70 w / w%, or 20 to 60 w / w%, or 20 to 50 w / w%, or 20 to 40 w / w%, or 20 to 30 w / w%, or 30 to 90 w / w%, or 30 to 8 It may be in the range of 0 w / w%, or 30-70 w / w%, or 30-60 w / w%, or 30-50 w / w%, or 30-40 w / w%, or 40-90 w / w%, or 40-80 w / w%, or 40-70 w / w%, or 40-60 w / w%, or 40-50 w / w%, or 50-90 w / w%, or 50-80 w / w%, or 50-70 w / w%, or 50-60 w / w%, or 60-90 w / w%, or 60-80 w / w%, or 60-70 w / w%, or 70-90 w / w%, or 70-80 w / w%. For example, a composition or precipitate containing vaterite (stable or reactive) or PCC may include blends of 75% OPC and 25% composition, or 80% OPC and 20% composition, or 85% OPC and 15% composition, or 90% OPC and 10% composition, or 95% OPC and 5% composition.

[0214] In certain embodiments, a composition or precipitate containing vaterite (stable or reactive) or PCC may further contain aggregate. Aggregate may be included in the composition or precipitate to provide mortar containing fine aggregate and concrete also containing coarse aggregate. Fine aggregate is material that passes almost entirely through a No. 4 sieve (ASTM C125 and ASTM C33), such as silica sand. Coarse aggregate is material that is mainly held in place by a No. 4 sieve (ASTM C125 and ASTM C33), such as silica, quartz, crushed round marble, glass spheres, granite, lime, calcite, feldspar, alluvial sand, sand or any other durable aggregate, and mixtures thereof. Thus, aggregate is used broadly to refer to several different kinds of fine particulate materials, both coarse and fine, including, but not limited to, sand, gravel, crushed stone, slag, and recycled concrete. In some embodiments, the aggregate added to the precipitate is activated aggregate, which is activated on the surface by the precipitate (this embodiment is described earlier in this specification). The amount and properties of the aggregate can vary widely. In some embodiments, the amount of aggregate may range from 25 to 80 w / w%, e.g., 40 to 70 w / w%, and 50 to 70 w / w%, of the total composition produced from both the composition and the aggregate.

[0215] In some embodiments, the composition or precipitate containing the reactive vaterite prepared by the method described above is treated with an aqueous medium under one or more suitable conditions, after which it sets and hardens. The aqueous medium includes, but is not limited to, fresh water or brine containing additives as needed. In some embodiments, one or more suitable conditions include, but is not limited to, temperature, pressure, duration for setting, ratio of the aqueous medium to the composition, and combinations thereof. The temperature may be a temperature relative to the temperature of the aqueous medium. In some embodiments, the temperature is in the range of 0 to 110°C, or 0 to 80°C, or 0 to 60°C, or 0 to 40°C, or 25 to 100°C, or 25 to 75°C, or 25 to 50°C, or 37 to 100°C, or 37 to 60°C, or 40 to 100°C, or 40 to 60°C, or 50 to 100°C, or 50 to 80°C, or 60 to 100°C, or 60 to 80°C, or 80 to 100°C. In some embodiments, the pressure is atmospheric pressure or above atmospheric pressure. In some embodiments, the time for setting the cement product is 30 minutes to 48 hours, or 30 minutes to 24 hours, or 30 minutes to 12 hours, or 30 minutes to 8 hours, or 30 minutes to 4 hours, or 30 minutes to 2 hours, or 2 to 48 hours, or 2 to 24 hours, or 2 to 12 hours, or 2 to 8 hours, or 2 to 4 hours, or 5 to 4 hours, or 5 to 12 hours, or 5 to 8 hours, or 5 to 4 hours, or 5 to 2 hours, or 10 to 48 hours, or 10 to 24 hours, or 24 to 48 hours.

[0216] While the composition or precipitate is being mixed with an aqueous medium, the precipitate can be subjected to a high-shear mixer. After mixing, the precipitate can be dehydrated again and placed in a pre-formed mold to produce a formed building material, or it can be used to produce a formed building material using a process well known in the art or as described herein. Alternatively, the precipitate can be mixed with water and allowed to set. The precipitate can set over several days and then be placed in an oven to dry, for example, at 40°C, or 40°C-60°C, or 40°C-50°C, or 40°C-100°C, or 50°C-60°C, or 50°C-80°C, or 50°C-100°C, or 60°C-80°C, or 60°C-100°C. The precipitate can be cured at high temperatures such as 50°C to 60°C, 50°C to 80°C, 50°C to 100°C, 60°C to 80°C, 60°C to 100°C, or 60°C or 80°C to 100°C, at high humidity, for example, 30%, 40%, 50%, or 60%.

[0217] Products produced by the methods described herein may be aggregates or building materials or precast or formed building materials. In some embodiments, products produced by the methods described herein include non-cement materials, such as paper, paint, and PVC. In some embodiments, products produced by the methods described herein include artificial reefs. These products are described herein.

[0218] In some embodiments, the precipitate containing vaterite (stable or reactive) or PCC in wet or dry form may be mixed with one or more admixtures to impart one or more properties to the product, including but not limited to strength, flexural strength, compressive strength, porosity, and thermal conductivity. The amount of admixture used may vary depending on the properties of the admixture. In some embodiments, the amount of one or more admixtures is in the range of 1 to 50 w / w%, for example, 1 to 30 w / w%, or 1 to 25 w / w%, or 1 to 20 w / w%, or 2 to 10 w / w%. Examples of admixtures include, but are not limited to, setting accelerators, setting retarders, air entrainers, foaming agents, defoaming agents, alkali reactivity reducers, binding admixtures, dispersants, coloring admixtures, corrosion inhibitors, moisture-proof admixtures, gas-forming agents, permeability reducers, pumping aids, shrinkage-correcting admixtures, fungicidal admixtures, bactericidal admixtures, insecticidal admixtures, rheological modifiers, finely ground mineral admixtures, pozzolanes, aggregates, wetting agents, strength enhancers, water repellents, reinforcing materials such as fibers, and any other admixtures. When admixtures are used, the composition or precipitate into which the admixture material is introduced is mixed for a sufficient amount of time to relatively uniformly disperse the admixture material in the composition.

[0219] The setting accelerator can be used to accelerate the setting and initial strength growth of cement. Examples of setting accelerators that can be used include, but are not limited to, POZZOLITH (registered trademark) NC534, a non-chloride type setting accelerator, and / or RHEOCRETE (registered trademark) CNI, a corrosion inhibitor based on calcium nitrite, both of which are sold under the aforementioned trademarks by BASF Admixtures Inc. of Cleveland, Ohio. Retarding admixtures, also known as retarders or water retarders for delay setting or hydration control, are used to slow down, delay, or retard the setting rate of cement. Most retarders can act as low-level water reducers and can also be used to entrain some air into the product. An example of a retarder is DELVO (registered trademark) by BASF Admixtures Inc. of Cleveland, Ohio. Air-entraining agents include any substance that entrains air into the composition. Some air-entraining agents can also reduce the surface tension of the composition at low concentrations. Air-entraining admixtures are used to intentionally entrain microscopic air bubbles into the cement. Entraining air can increase the workability of the mix while eliminating or reducing segregation and bleeding. The materials used to achieve these desired effects can be selected from wood resins, natural resins, synthetic resins, sulfonated lignins, petroleum acids, proteinaceous materials, fatty acids, resin acids, alkylbenzene sulfonates, sulfonated hydrocarbons, vinsol resins, anionic surfactants, cationic surfactants, non-ionic surfactants, natural rosins, synthetic rosins, inorganic air-entraining agents, synthetic detergents, and their corresponding salts, as well as mixtures thereof. The air-entraining agent is added in an amount that provides the desired level of air in the cement composition. Examples of air-entraining agents that can be utilized in an admixture system include, but are not limited to, MB AE90, MB VR, and MICRO AIR (registered trademark), all of which are available from BASF Admixtures Inc. of Cleveland, Ohio.

[0220] In some embodiments, the precipitated material is mixed with a foaming agent. The foaming agent incorporates a large amount of air pores / porosity and promotes the reduction of the material density. Examples of foaming agents include, but are not limited to, soap, detergents (alkyl ether sulfate), millifoam (trademark) (alkyl ether sulfate), cedepal (trademark) (ammonium alkyl ethoxysulfate), witcolate (trademark) 12760, and the like.

[0221] Defoaming agents are also targeted as admixtures. Defoaming agents are used to reduce the air content in the cement composition. Dispersing agents are also targeted as admixtures. Dispersing agents include, but are not limited to, polycarboxylate dispersants with or without polyether units. The term dispersing agent also means a chemical that functions as a plasticizer, a water reducing agent, such as a high range water reducing agent, a fluidizing agent, an anti-agglomerant, or a superplasticizer for the composition, such as lignin sulfonate, salts of sulfonated naphthalene sulfonate condensates, salts of sulfonated melamine sulfonate condensates, beta naphthalene sulfonate, sulfonated melamine formaldehyde condensates, naphthalene sulfonate formaldehyde condensate resins, such as LOMAR D (registered trademark) dispersant (Cognis Inc., Cincinnati, Ohio), polyaspartic acid, or oligomeric dispersants. Polycarboxylate dispersants can be used, which means dispersants having a carbon skeleton containing pendant side chains in which at least a part of the side chains is bonded to the skeleton via carboxyl groups or ether groups.

[0222] Natural and synthetic admixtures can be used to color products for aesthetic and safety reasons. These coloring admixtures may consist of pigments, including carbon black, iron oxide, phthalocyanine, amber, chromium oxide, titanium dioxide, cobalt blue, and organic colorants. Corrosion inhibitors are also covered as admixtures. Corrosion inhibitors can work to protect embedded rebar from corrosion. Materials commonly used to inhibit corrosion include calcium nitrite, sodium nitrite, sodium benzoate, certain phosphates or fluorosilicates, aluminite, amines, and related chemicals. Moisture-proof admixtures are also covered. Moisture-proof admixtures reduce the permeability of products with low cement content, high water-cement ratio, or fine aggregate defects. These admixtures slow down the penetration of moisture into dry products and include certain soaps, stearates, and petroleum products. Gas-forming admixtures are also covered. Gas-forming agents, or gas-forming agents, are sometimes added to a mix to cause slight expansion before curing. The amount of expansion depends on the amount of gas-forming material used and the temperature of the new admixture. Aluminum powder, resin soaps, and vegetable or animal glues, saponins, or hydrolyzed proteins can be used as gas-forming agents. Permeability-reducing agents are also included. Permeability-reducing agents can reduce the rate at which water moves through the mix under pressure. Silica fume, fly ash, ground slag, natural pozzolanes, water-reducing agents, and latex can be used to reduce the permeability of the mix.

[0223] Admixtures of rheological modifiers are also included. Rheological modifiers can be used to increase the viscosity of a composition. Suitable examples of rheological modifiers include hardened silica, colloidal silica, hydroxyethylcellulose, starch, hydroxypropylcellulose, fly ash (as defined in ASTM C618), mineral oils (e.g., light naphthenes), clays, e.g., hectorite clay, polyoxyalkylenes, polysaccharides, natural gums, or mixtures thereof. Some mineral extenders, for example, but not limited to, meerse clay, are rheological modifiers.

[0224] Shrinkage-correcting admixtures are also included. TETRAGUARD® is an example of a shrinkage-reducing admixture, available from BASF Admixtures Inc. in Cleveland, Ohio. Bacterial and fungal growth on or within cured products can be partially controlled by the use of antifungal and antibacterial admixtures. Materials intended for these purposes include, but are not limited to, polyhalogenated phenols, dieldrin emulsions, and copper compounds. In some embodiments, processability-improving admixtures are also included. Entrained air can be used as a lubricant and processability-improving agent. Other processants include water-reducing agents and certain fine-grit admixtures.

[0225] In some embodiments, a composition or precipitate containing vaterite (stable or reactive) or PCC is used together with a reinforcing material, such as fibers, if a fiber-reinforced product is desired. The fibers can be made from zirconia-containing materials, aluminum, glass, steel, carbon, ceramics, grass, bamboo, wood, glass fibers, or synthetic materials, such as polypropylene, polycarbonate, polyvinyl chloride, polyvinyl alcohol, nylon, polyethylene, polyester, rayon, high-strength aramid (i.e., Kevlar®), or mixtures thereof. The reinforcing material is described in U.S. Patent Application No. 13 / 560,246, filed July 27, 2012, which is incorporated herein by reference in its entirety.

[0226] The components of the precipitate, including vaterite (stable or reactive) or PCC, can be combined using any suitable protocol. Each material can be mixed during the process, or some or all of the materials can be mixed beforehand. Alternatively, some of the materials can be mixed with water, with or without an admixture, such as a high-range water-reducing admixture, and then mixed with the remaining materials. Any conventional mixing apparatus can be used. For example, Hobart mixers, slant cylinder mixers, Omni mixers, Henschel mixers, V-type mixers, and Nauta mixers can be used.

[0227] In one embodiment, a system for forming vaterite-containing calcium carbonate is provided, comprising (i) a dissolution reactor configured to dissolve lime in an aqueous solution of a base under one or more precipitation conditions to produce a precipitate and a supernatant solution containing vaterite-containing calcium carbonate.

[0228] In one embodiment, a system for forming vaterite-containing calcium carbonate is provided, comprising: (i) a calcination reactor configured to calcine limestone to form a gas stream of lime and carbon dioxide; (ii) a dissolution reactor configured to dissolve lime in an aqueous base solution under one or more dissolution conditions to produce a first aqueous solution containing a calcium salt and a gas stream containing ammonia; and (iii) a treatment reactor configured to treat the first aqueous solution containing a calcium salt with a gas stream containing carbon dioxide and a gas stream containing ammonia under one or more precipitation conditions to form a precipitate containing vaterite-containing calcium carbonate and a supernatant solution.

[0229] In one embodiment, a system for forming vaterite-containing calcium carbonate is provided, comprising: (i) a calcination reactor configured to calcine limestone into a gas stream of lime and carbon dioxide; (ii) a dissolution reactor configured to dissolve lime in an aqueous solution of an N-containing inorganic salt under one or more dissolution conditions to produce a first aqueous solution containing a calcium salt and a gas stream containing ammonia; and (iii) a treatment reactor configured to treat the first aqueous solution containing a calcium salt with a gas stream containing carbon dioxide and a gas stream containing ammonia under one or more precipitation conditions to form a precipitate containing vaterite-containing calcium carbonate and a supernatant solution.

[0230] In one embodiment, a system for forming vaterite-containing calcium carbonate is provided, comprising: (i) a calcination reactor configured to calcine limestone into a gas stream of lime and carbon dioxide; (ii) a dissolution reactor configured to dissolve lime in an aqueous solution of an N-containing inorganic salt under one or more dissolution conditions to produce a first aqueous solution containing a calcium salt and a gas stream containing ammonia; (iii) a cooling reactor configured to recover the gas stream containing carbon dioxide and the gas stream containing ammonia, and to subject the gas stream to a cooling process under one or more cooling conditions to condense a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, ammonium carbamate, or a combination thereof; and (iv) a treatment reactor configured to treat the first aqueous solution containing the calcium salt with a second aqueous solution containing ammonium bicarbonate, ammonium carbonate, ammonia, ammonium carbamate, or a combination thereof under one or more precipitation conditions to form a precipitate and supernatant solution containing vaterite-containing calcium carbonate. In some embodiments of the above-described embodiments, the vaterite is stable vaterite, reactive vaterite, or PCC. In the aforementioned embodiments and some of the embodiments, the dissolution reactor is integrated into the cooling reactor (as shown in Figures 4-7 and described herein).

[0231] In the embodiments described above and in some embodiments of the system, the system further includes a recovery system for recovering a base from an aqueous solution and returning it to a dissolution reactor. The recovery system is configured to perform pyrolysis, reverse osmosis, multi-stage flash, multiple-effect distillation, vapor recompression, distillation, and combinations thereof, as described herein.

[0232] The methods and systems provided herein can be carried out on land (for example, near a limestone quarry or in a location that is easily and economically transportable), at sea, or in the ocean. In some embodiments, a cement plant that calcines lime may further incorporate the systems described herein to form a precipitate and, moreover, to form a product from the precipitate.

[0233] Some embodiments include a system, including a processing plant or manufacturing facility, for carrying out the methods described herein. The system may have any stereochemical configuration that enables the specific production method of the object of interest to be carried out.

[0234] In certain embodiments, the system includes a structure having a lime source and an inlet for a base aqueous solution. For example, the system may include a pipeline or similar supply unit for the base aqueous solution as described herein. The system further includes an inlet for CO2 and components for combining these sources with water (an aqueous solution as needed, e.g., water, brine, or seawater) before or in the precipitation reactor. In some embodiments, the gas-liquid contact apparatus is configured to contact enough CO2 to produce more than 1 ton, 10 tons, 100 tons, 1,000 tons, or 10,000 tons of precipitate per day.

[0235] The system further includes a precipitation reactor that subjects water introduced into the precipitation reactor to one or more precipitation conditions (as described herein) to produce a precipitate and a supernatant. In some embodiments, the precipitation reactor is configured to hold enough water to produce more than 1 ton, 10 tons, 100 tons, 1,000 tons, or 10,000 tons of precipitate per day. The precipitation reactor may also be configured to include any of several different elements, such as a temperature modulation element (e.g., configured to heat water to a desired temperature), a chemical addition element (e.g., configured to introduce additives, etc., into the precipitation reaction mixture), or computer automation.

[0236] A waste gas stream containing CO2 and optionally NH3 can be supplied to the precipitation and / or cooling reactors by any convenient method. In some embodiments, the waste gas stream is supplied using a gas conveyor (e.g., a duct) traveling from the dissolution reactor to the precipitation and / or cooling reactors.

[0237] If the water source that the system processes to generate precipitate is seawater, for example, if the inlet is a pipeline or supply pipe from seawater to a land-based system or a ship's inlet port, for example, if the system is part of a ship in a marine system, then the inlet is fluidly connected to the seawater source.

[0238] The method and system may also include one or more detectors (not shown) configured to monitor a basic aqueous solution, lime, and / or carbon dioxide. Monitoring may include, but is not limited to, the collection of data regarding the pressure, temperature, and composition of the water or carbon dioxide gas. The detectors may be any convenient device configured to monitor, e.g., pressure sensors (e.g., electromagnetic pressure sensors, potentiometric pressure sensors, etc.), temperature sensors (e.g., resistance temperature detectors, thermocouples, gas thermometers, thermistors, pyrometers, infrared radiation sensors, etc.), volume sensors (e.g., geophysical diffraction tomography, X-ray tomography, underwater acoustic probes, etc.), and devices for determining the chemical composition of the water or carbon dioxide gas (e.g., IR spectrometers, NMR spectrometers, UV-vis spectrophotometers, high-performance liquid chromatographs, inductively coupled plasma emission spectrometers, inductively coupled plasma mass spectrometers, ion chromatographs, X-ray diffractometers, gas chromatographs, gas chromatography-mass spectrometers, flow injection analysis, scintillation counters, acid titrations, and flame emission spectrometers, etc.).

[0239] In some embodiments, the detector may also include a computer interface configured to provide the user with collected data regarding a basic aqueous solution, lime, and / or carbon dioxide / ammonia gas. In some embodiments, the summary may be stored as a computer-readable data file or printed as a user-readable document.

[0240] In some embodiments, the detector may be a monitoring device capable of collecting real-time data (e.g., internal pressure, temperature, etc.). In other embodiments, the detector may be one or more detectors configured to periodically determine the parameters of a basic aqueous solution, lime, and / or carbon dioxide gas, for example, by determining its composition every minute, every 5 minutes, every 10 minutes, every 30 minutes, every 60 minutes, every 100 minutes, every 200 minutes, every 500 minutes, or any other interval.

[0241] In certain embodiments, the system can further include a station for preparing building materials such as cement or aggregates from the precipitate. Other materials such as the formed building materials and / or non-cement materials can also be formed from the precipitate and a station suitable for their preparation can be used.

[0242] As shown previously, the system can be present on land or at sea. For example, the system can be a land-based system, such as near a coastal area close to a seawater source, or even an inland location where water is piped to the system from a water source, such as the ocean. Alternatively, the system is an aquatic system, i.e., a system present on or in water. Such a system can be present on a boat, an ocean-based platform, etc., as desired.

[0243] The calcium carbonate slurry is pumped to a drying system, which in some embodiments includes spray drying after the filtration step. The water separated from the drying system is either released or recycled to the reactor. The solid or powder resulting from the drying system is utilized as cement or aggregates for producing building materials. The solid or powder can also be used as a PCC filler in non-cement products such as paper, plastics, paints, etc. The solid or powder can also be used in the formation of formed building materials such as drywall, cement board, etc.

[0244] In some embodiments, the system may include a control station configured to control the amount of aqueous base solution and / or lime transported to a precipitation or dissolution reactor; the amount of precipitate transported to a separation unit; the amount of precipitate transported to a drying station; and / or the amount of precipitate transported to a purification station. The control station may include a set or multiple valve system controlled manually, mechanically, or digitally, or may use any other convenient flow control protocol. In some cases, the control station may include a computer interface configured to provide the user with input and output parameters for controlling the amounts (the control may be computer-assisted or fully computer-controlled). II. Products

[0245] This specification provides a method and system for utilizing lime formed from the calcination of limestone by dissolving lime in a basic aqueous solution to produce a precipitate containing vaterite and / or aragonite polymorphs of calcium carbonate, wherein the vaterite is converted to aragonite to form cement. This specification also provides an environmentally friendly method and system for removing or separating CO2 from a waste gas stream derived from the calcination of limestone and fixing the CO2 in a storage-stable non-gasic form (e.g., building materials for structures such as buildings and infrastructure, as well as the structures themselves or the formed building materials, e.g., drywall, or non-cemental materials, e.g., paper, paint, plastic, or artificial reefs), thus preventing the CO2 from escaping into the atmosphere. building materials

[0246] As used herein, “building materials” includes materials used in construction. In one embodiment, a structure or building material is provided that includes, for example, a precipitate in which reactive vaterite is converted to aragonite, or a solidified and hardened form of PCC that solidifies and hardens. Products containing the precipitate in the aragonite form (aragonite formed by the dissolution and reprecipitation of reactive vaterite) (products (A) or (B) in the figure) exhibit one or more unexpected properties, including, but not limited to, high compressive strength, high porosity (low density or light weight), neutral pH (useful as, for example, artificial reefs), and a fine network structure.

[0247] Examples of such structures or building materials include, but are not limited to, buildings, driveways, foundations, kitchen slabs, furniture, sidewalks, roads, bridges, highways, overpasses, parking structures, bricks, blocks, scaffolding for walls and gates, fences or poles, and combinations thereof. Formed building materials

[0248] As used herein, “formed building materials” include materials that have been formed into structures having a defined physical shape (e.g., molded, cast, cut, or otherwise produced). Formed building materials may also be pre-cast building materials, such as pre-cast cement or concrete products. Formed building materials and methods for producing and using formed building materials are described in U.S. Patent Application No. 12 / 571,398, filed September 30, 2009, which is incorporated herein by reference in its entirety. Formed building materials can vary considerably and include materials that have been formed into structures having a defined physical shape, i.e., a three-dimensional arrangement (e.g., molded, cast, cut, or otherwise produced). Formed building materials do not have a defined stable shape and are rather different from amorphous building materials (e.g., powders, pastes, slurries, etc.) that fit into a container, such as a bag or other container, in which they are held. Formed building materials differ from irregularly or imprecisely formed materials (e.g., discarded aggregates, bulk forms, etc.) in that they are produced according to specifications that enable the use of the formed building materials in, for example, buildings. Formed building materials can be prepared according to conventional manufacturing protocols for such structures, except that precipitates are used in the production of such materials.

[0249] In some embodiments, the methods and systems provided herein further include the step of condensing, curing, and forming a building material from a precipitate containing reactive vaterite (which is converted to aragonite) or condensed and cured PPC.

[0250] In some embodiments, the formed building material made from the precipitate has a compressive or flexural strength of at least 3 MPa, at least 10 MPa, or at least 14 MPa, or between 3 and 30 MPa, or between about 14 and 100 MPa, or between about 14 and 45 MPa, or has the compressive strength of the precipitate after it has set and hardened as described herein.

[0251] Examples of formed building materials that can be produced by the methods and systems described herein include, but are not limited to, masonry units, bricks, blocks, and tiles, including ceiling tiles, as merely examples; building panels, as merely examples, cement boards (boards conventionally made from cement, e.g., fiber cement boards) and / or drywalls (boards conventionally made from gypsum); conduits; basins; beams; columns, slabs; sound barriers; thermal insulation materials; or combinations thereof. Building panels are formed building materials used in a broad sense to refer to any non-load-bearing structural element characterized by having length and width substantially greater than thickness. Thus, panels may be plates, boards, roofing boards, and / or tiles. Exemplary building panels formed from precipitated materials provided herein include cement boards and / or drywalls. Building panels are polygonal structures having dimensions that vary considerably depending on their intended use. The dimensions of the building panels can range from 100 to 300 cm in length, for example, 50 to 500 cm including 250 cm; from 75 to 150 cm in width, for example, 25 to 200 cm including 100 cm; and from 7 to 20 mm in thickness, for example, 5 to 25 mm including 10 to 15 mm.

[0252] In some embodiments, cement boards and / or drywalls can be used in the manufacture of different types of boards, for example, but not limited to, paper-clad boards (e.g., surface-reinforced with cellulose fibers), fiberglass-clad or fiberglass mat-clad boards (e.g., surface-reinforced with fiberglass mats), fiberglass mesh-reinforced boards (e.g., surface-reinforced with fiberglass mesh), and / or fiber-reinforced boards (e.g., cement-reinforced with cellulose, glass, fibers, etc.). These boards can be used in a variety of applications, but not limited to, paneling, e.g., fiber-cement paneling, roofing, underlayment, sheathing, cladding, decking, ceilings, shaft liners, wall boards, backers, trim, frieze, roofing panels, and fascia, as well as / or underlayment.

[0253] Cement boards are conventionally made from cement, such as OPC, magnesium oxide cement, and / or calcium silicate cement. Cement boards made by the methods and systems provided herein are made from a precipitate that partially or completely replaces the conventional cement in the board. In some embodiments, the cement board may include building panels prepared as a combination of aragonite cement (which sets and hardens when vaterite is converted to aragonite) and fibers and / or glass fibers, and both sides of the board may be reinforced with additional fibers and / or glass fibers.

[0254] Cement board is a formed building material used as a backerboard for ceramics, which can be used in some embodiments as a backing board for bathroom tiles, kitchen counters, backsplashes, etc., and can have lengths ranging from 100 to 200 cm. The physical and mechanical properties of cement board can vary. In some embodiments, the flexural strength can vary in the range between 1 and 7.5 MPa, including 2 to 6 MPa, e.g., 5 MPa. The compressive strength can also vary in the range between 5 and 50 MPa, including 10 to 30 MPa, e.g., 15 to 20 MPa. In some embodiments, cement board can be used in environments that are extensively exposed to moisture (e.g., commercial saunas). The compositions or precipitates described herein can be used to produce the desired shapes and sizes for forming cement board. Furthermore, various additional components, including, but not limited to, plasticizers, clays, foaming agents, accelerators, retarders, and air-entraining additives, can be added to the cement board. The composition can then be poured into a sheet mold or used with a roller to form sheets of the desired thickness. The molded composition can be further compressed by roller compression, hydraulic pressure, vibration compression, or resonant shock compression. The sheet is then cut into cement boards of the desired dimensions.

[0255] Another type of building panel formed from the compositions or precipitates described herein is backerboard. Backerboard can be used for the construction of interior and / or exterior floors, walls, and ceilings. In some embodiments, backerboard is partially or completely made from a precipitate.

[0256] Another type of building panel formed from this composition or precipitate is drywall. Drywall includes boards used for the construction of interior and / or exterior floors, walls, and ceilings. Traditionally, drywall is formed from gypsum (called paper-backed board). In some embodiments, drywall is partially or completely made from carbonate precipitate, thereby replacing gypsum in drywall products. In some embodiments, drywall may include building panels prepared as a combination of aragonite cement (which sets and hardens when vaterite is converted to aragonite) and cellulose, fibers, and / or glass fibers, with both sides of the board reinforced with additional paper, fibers, glass fiber mesh, and / or glass fiber mats. Various processes for producing drywall products are well known in the art and are well within the scope of the present invention. Some examples, but not limited to, include wet processes, semi-dry processes, extrusion processes, and wonderboard® processes, which are described herein.

[0257] In some embodiments, the drywall is a panel made from a paper liner that wraps around an inner core. For example, in some embodiments, during the process of making a drywall product from a precipitate, a slurry of the precipitate containing vaterite is poured over a paper sheet. Another sheet of paper is then placed on top of the precipitate, so that the precipitate has paper on both sides (the resulting composition is sandwiched between two outer materials, e.g., cardboard or fiberglass mat). The vaterite in the precipitate is then converted to aragonite (using additives and / or heat), and then the aragonite sets and hardens. Once the core has set and is dried in a large drying chamber, the sandwich panel becomes rigid and strong enough to be used as a building material. The drywall sheets are then cut and separated.

[0258] The flexural and compressive strengths of drywalls formed from precipitated material are the same as, or higher than, those of conventional drywalls prepared using gypsum plaster, which is known to be a flexible building material. In some embodiments, the flexural strength may be in the range of 0.1 to 3 MPa, including 0.5 to 2 MPa, e.g., 1.5 MPa. The compressive strength may also vary, in some cases being in the range of 1 to 20 MPa, including 5 to 15 MPa, e.g., 8 to 10 MPa. In some embodiments, formed building materials, e.g., building panels, e.g., cement boards and drywalls, produced by the methods and systems described herein, are low-density and highly porous, thereby making them suitable for lightweight insulation applications. The highly porous and lightweight formed building materials, e.g., building panels, may be due to the aragonite microstructure that arises when vaterite is converted to aragonite. The conversion of vaterite during the dissolution / reprecipitation process can result in microporosity, while the voids created between the formed aragonite crystals can provide nanoporosity, thereby resulting in a highly porous, lightweight structure. During the conversion process, but not limited to, foaming agents, rheological modifiers, and mineral extenders, such as certain admixtures including, but not limited to, clay and starch, can be added. The foaming agent can entrain air into the mixture, thereby adding porosity to the product and reducing its overall density. Additionally, mineral extenders such as sepiolite clay can increase the viscosity of the mixture, thereby preventing the separation of precipitates from water.

[0259] One application of cement board or drywall is fiber cement paneling. Fiber cement paneling formed by the methods and systems provided herein includes building panels prepared as a combination of aragonite cement, aggregate, woven cellulose, and / or polymer fibers, which can have a wood-like texture and flexibility.

[0260] In some embodiments, the formed building material is a masonry unit. A masonry unit is a formed building material used in the construction of load-bearing and non-load-bearing structures, generally assembled using mortar, grout, etc. Exemplary masonry units formed from this composition include bricks, blocks, and tiles.

[0261] Another formed building material created from the precipitates described herein is a conduit. A conduit is a pipe or similar structure configured to transport a gas or liquid from one place to another. A conduit may include, but is not limited to, any of many different structures used for transporting liquids or gases, including pipes, culverts, box culverts, drainage channels and portals, inlet structures, intake towers, gate wells, outlet structures, and the like.

[0262] Another formed building material created from the precipitates described herein is a water basin. The term water basin may include any container of any configuration used to hold a liquid, such as water. Thus, water basins may include, but are not limited to, structures such as wells, collection boxes, public health manholes, septic tanks, catch basins, grease traps / separators, and rainwater collection and storage tanks.

[0263] Another formed building material from the precipitated material described herein is a beam, which in a broad sense refers to a horizontal load-bearing structure having high bending and compressive strength. The beam may be a square cross type, C channel type, L-shaped cross section edge beam, I-beam, spandrel beam, H-beam, and may have an inverted T design. The beam may also be a horizontal load-bearing unit including, but is not limited to, joists, lintels, arch channels and cantilever beams.

[0264] Another formed building material, formed from the precipitated material described herein, is a column, which in a broad sense refers to a vertical load-bearing structure that primarily withstands loads due to axial compression and includes structural elements such as compression members. Other vertical compression members of the present invention may include, but are not limited to, supports, piers, bases, or piles.

[0265] Another formed building material created from the precipitated material described herein is a concrete slab. Concrete slabs are building materials used in the construction of prefabricated foundations, floors, and wall panels. In some cases, concrete slabs can be used as floor units (e.g., hollow slab units or double-T designs).

[0266] Another formed building material formed from the precipitated material described herein is a sound barrier, which refers to a structure used as a barrier for sound attenuation or absorption. Thus, sound barriers may include, but are not limited to, structures such as soundproof panels, reflective barriers, absorbing barriers, and reactive barriers.

[0267] Another formed building material, which is formed from the precipitated material described herein, is an insulating material, which refers to a material used to reduce or suppress heat conduction. Insulating materials may also include materials that reduce or suppress radiative heat transfer.

[0268] In some embodiments, other formed building materials, such as precast concrete products, are not limited to, bunker silos, livestock feed troughs, cattle grids, agricultural fences, H-shaped latticework, J-shaped latticework, livestock slats, livestock water tanks, building panel walls, cladding (bricks), building trim, foundations, floors including slabs, walls, precast sandwich panels for double walls, waterways, mechanically stabilized earth panels, box culverts, three-sided culverts, bridge systems, railroad crossings (RR crossings), railroad ties (RR ties), sound barriers / barriers, Jersey barriers, tunnel segments, reinforced concrete boxes, utility protection structures, handholes, hollow core products, lighting pole bases, meter boxes, panel vaults, pull boxes, telecommunications structures, transformer pads, transformer rooms, trenches, utility storage rooms. This includes vaults, utility poles, control environment rooms, underground bunkers, mausoleums, tombstones, coffins, hazardous materials storage containers, detention vaults, drainage pits, manholes, ventilation systems, distribution boxes, dozing tanks, drywells, grease traps, leachate pits, sand-oil / oil-water separators, septic tanks, water / sewage storage tanks, wetwells, fire cisterns, floating docks, underwater infrastructure, decks, railings, breakwaters, roof tiles, paving stones, community retaining walls, residential retaining walls, modular block systems, and segmental retaining walls. Non-cement composition

[0269] In some embodiments, the methods and systems described herein, without limitation, include steps of preparing other products, including non-cement compositions, from the precipitate materials described herein, including paper, polymer products, lubricants, adhesives, rubber products, chalk, asphalt products, paints, abrasives for paint removal, personal care products, cosmetics, cleaning products, personal hygiene products, edible products, agricultural products, soil conditioners, biocides, environmental remediation products, and combinations thereof. Such compositions are described in U.S. Patent No. 7,829,053 issued November 9, 2010, which is incorporated herein by reference in its entirety. artificial marine structures

[0270] In some embodiments, the methods described herein, though not limited to them, include the step of preparing artificial marine structures, including artificial corals and reefs, from the precipitate materials described herein. In some embodiments, the artificial structures can be used in aquariums or in the ocean. In some embodiments, these products are prepared from precipitate materials containing reactive vaterite that converts to aragonite after setting and hardening. Aragonite cement provides a neutral or near-neutral pH that can promote the maintenance and growth of marine organisms. Aragonite reefs can provide suitable habitats for marine species.

[0271] The following examples are provided to give a complete disclosure and explanation of how the present invention is made and used, and are not intended to limit the scope of what the inventors consider to be the present invention, nor to indicate that the following experiments are all or only experiments performed. While efforts have been made to ensure accuracy with respect to the numerical values ​​used (e.g., quantities, temperatures, etc.), some experimental error and deviation should be taken into consideration. [Examples]

[0272] (Example 1) Formation and transformation of precipitates from lime NH4Cl is dissolved in water. Lime is added to the aqueous solution and mixed at 80°C in a container with a steam outlet. The steam leaves the container through the outlet and condenses with CO2 at 20°C to form an aqueous solution containing ammonia, ammonium bicarbonate, and ammonium carbonate in a first collapsible airtight bag. The solid and liquid mixture remaining in the container is cooled to 20°C and vacuum filtered to remove insoluble impurities. The clear filtrate containing CaCl2 is transferred to a second collapsible airtight bag. Both bags are immersed in a water bath to preheat the solution to 35°C. The precipitation reactor is an acrylic cylinder equipped with baffles, a pH electrode, a thermocouple, a turbine impeller, and inlet and outlet ports for the liquid feed and product slurry. During startup, the CaCl2-containing solution in the second bag is pumped into the reactor at a fixed flow rate. The solution in the first bag is introduced by a separate pump while stirring with a mixer. A computer-controlled loop controls the continuous inflow of ammonium carbonate-containing solution from the first bag to maintain the pH between 7 and 9. A reactive vaterite slurry is formed. The resulting reactive vaterite slurry is continuously collected in a holding container. The slurry is vacuum filtered. The reactive vaterite filtration cake is oven-dried at 100°C. The cake exhibits 100% vaterite with an average particle size of 5 microns. The clear filtrate containing regenerated NH4Cl is reused for subsequent experiments.

[0273] Dried reactive vaterite solids are mixed with water to form a paste. After 1 day, the XRD of the paste shows 99.9% aragonite (the vaterite has been completely converted to aragonite). The paste is cast into a 2-inch x 2-inch x 2-inch cube and allowed to set and harden for 7 days in a humidity chamber set at 60°C and 80% relative humidity. The cemented cube is dried in an oven at 100°C. Destructive testing determines that the compressive strength of the cube is 4600 psi (approximately 31 MPa). (Example 2) Formation and transformation of precipitates from lime

[0274] NH4Cl is dissolved in water. Lime is added to the aqueous solution and mixed under pressure at 120°C in a dissolution vessel with vapor and slurry outlets. The slurry containing insoluble impurities is separated through the bottom outlet and passed through a filter to remove solids. The clear filtrate containing CaCl2 is cooled to 30°C and pumped into a precipitation reactor. The precipitation reactor is an acrylic cylinder equipped with baffles, a gas sparger, a pH electrode, a thermocouple, a turbine impeller, and inlets and outlets for liquid and gas feeds and product slurry. Ammonia-containing vapor passes from the dissolution reactor to a sparger located in the precipitation reactor. CO2 also passes into the precipitation reactor. A computer automated control loop controls the continuous inflow of the CaCl2-containing solution to maintain the pH between 7 and 9. The resulting reactive vaterite slurry is continuously collected in a holding vessel. The slurry is vacuum filtered. The reactive vaterite filtration cake is oven-dried at 100°C. The cake exhibits 100% vaterite with an average particle size of 5 microns. The clear filtrate containing the regenerated NH4Cl is reused in subsequent experiments.

[0275] Dried reactive vaterite solids are mixed into a paste using water. After 1 day, the XRD of the paste shows 99.9% aragonite (the vaterite has been completely converted to aragonite). The paste is cast into a 2-inch x 2-inch x 2-inch cube and allowed to set and harden for 7 days in a humidity chamber set to 60°C and 80% relative humidity. The cemented cube is dried in an oven at 100°C. Destructive testing determines that the compressive strength of the cube is 4600 psi (approximately 31 MPa). (Example 3) Control of product formation in a cooled reactor

[0276] NH4Cl is dissolved in water. Lime is added to the aqueous solution and mixed at 80°C in a container with a vapor outlet. The vapor containing ammonia leaves the container through the outlet, and the vapor condenses with CO2 (and water vapor) at 20°C to form an aqueous solution containing ammonia, ammonium bicarbonate, ammonium carbonate, and ammonium carbamate in a first collapsible airtight bag. The formation of the condensation product can be controlled by controlling the CO2 flow based on the pH of the aqueous solution.

[0277] Simulations of this process demonstrated that (i) by changing the CO2 flow until an outlet pH of 10.3 was obtained, a stream with a carbamate:carbonate:bicarbonate ratio of 45%:35%:20% was obtained; (ii) by changing the CO2 flow until an outlet pH of 9.7 was obtained, a stream with a carbamate:carbonate:bicarbonate ratio of 35%:25%:40% was obtained; and (iii) by changing the CO2 flow until an outlet pH of 8.7 was obtained, a stream with a carbamate:carbonate:bicarbonate ratio of 20%:10%:70% was obtained.

[0278] Therefore, when the system's pH is lowered by adjusting the CO2 flow rate, the amount of bicarbonate is more favorable than the amount of carbamate, and when the system's pH is raised by adjusting the CO2 flow rate, the amount of carbamate is more favorable than both bicarbonate and carbonate. (Example 4) Control of product formation in a cooled reactor

[0279] NH4Cl is dissolved in water. Lime is added to the aqueous solution and mixed at 80°C in a container with a vapor outlet. The ammonia-containing vapor leaves the container through the outlet and condenses with CO2 (and water vapor) at 20°C to form an aqueous solution containing ammonia, ammonium bicarbonate, ammonium carbonate, and ammonium carbamate in a first collapsible airtight bag. The formation of the condensation product can be controlled by controlling the CO2:NH3 ratio.

[0280] Simulations of this process demonstrated that (i) selecting the CO2 flow so that the CO2:NH3 mass ratio is 0.2:1 leads to a speciation of over 98% carbonate, (ii) selecting the CO2 flow so that the CO2:NH3 mass ratio is 1:1 leads to a speciation of over 15.6% carbamate, and (iii) selecting the CO2 flow so that the CO2:NH3 mass ratio is 20:1 leads to a speciation of over 90% bicarbonate. The data are shown in Table I and Figure 9 below. The data demonstrate that the CO2:NH3 ratio directly affects the ratio of the products formed in the refrigerated reactor. [Table I]

[0281] While the aforementioned invention has been described in some detail by examples and embodiments for the purpose of clear understanding, it will be readily apparent to those skilled in the art that certain changes and modifications can be made thereto without departing from the spirit or scope of the appended claims, in light of the teachings of the invention. Therefore, the foregoing merely illustrates the principles of the invention. Those skilled in the art will recognize that various combinations embodying the principles of the invention and falling within its spirit and scope can be devised, even if not explicitly stated or shown herein. Furthermore, the wording of all embodiments and conditions described herein is intended primarily to assist the reader in understanding the principles of the invention and the concepts given by the inventors to advance the art, and should be interpreted without limiting oneself to such specifically described embodiments and conditions. Moreover, all descriptions herein describing the principles, aspects and embodiments of the invention, and specific examples thereof, are intended to encompass both structural and functional equivalents. Furthermore, such equivalents are intended to include both currently known equivalents and future-developed equivalents, i.e., any developed elements that perform the same function regardless of structure. Accordingly, the scope of the present invention is not intended to be limited to the exemplary embodiments shown and described herein. The following claims are intended to define the scope of the present invention, and the methods and structures within these claims, as well as their equivalents, are intended to be protected thereby.

Claims

1. A step of calcining limestone to form lime and a gas stream containing carbon dioxide, The steps include: dissolving the lime in an aqueous solution containing an N-containing salt to produce an aqueous solution containing a calcium salt; The step of adding aggregate, which includes at least one of sand, gravel, crushed stone, slag, recycled concrete, quartz, crushed round marble, glass spheres, granite, lime, calcite, feldspar, and alluvial sand, to the aqueous solution containing a calcium salt, A step of treating the aqueous solution containing a calcium salt and the aggregate with a gas stream containing carbon dioxide so that a precipitate containing calcium carbonate is formed on the surface of the aggregate, wherein the calcium carbonate contains vaterite. Methods that include...

2. The method according to claim 1, wherein the lime comprises calcined lime, lightly calcined quicklime, incompletely combusted lime, or a combination thereof.

3. The method according to claim 1, wherein the N-containing salt is an N-containing inorganic salt, an N-containing organic salt, or a combination thereof.

4. The method according to claim 1, wherein the N-containing salt is an N-containing inorganic salt selected from the group consisting of ammonium halides, ammonium sulfate, ammonium sulfite, ammonium nitrate, ammonium nitrite, and combinations thereof.

5. The method according to claim 1, wherein the N-containing salt is ammonium chloride.

6. The method according to claim 1, wherein the N-containing salt is an N-containing organic salt of an N-containing organic compound selected from the group consisting of aliphatic amines, alicyclic amines, heterocyclic amines, and combinations thereof.

7. The method according to claim 1, wherein the aqueous solution containing the calcium salt further contains ammonia.

8. The method according to claim 1, wherein the dissolving step further comprises generating a gas stream containing ammonia, and the processing step further comprises processing the aqueous solution containing the calcium salt with the gas stream containing ammonia.

9. The method according to claim 1, wherein the aggregate is fine aggregate, coarse aggregate, or a combination thereof.

10. The method according to claim 1, wherein the calcium carbonate on the surface of the aggregate activates the surface of the aggregate.

11. The method according to claim 1, wherein the vaterite is a stable vaterite or a reactive vaterite.

12. The method according to claim 11, further comprising the step of mixing the precipitate containing reactive vaterite on the surface of the aggregate with Portland cement.

13. The method according to claim 12, further comprising the steps of adding water to the precipitate containing reactive vaterite on the surface of the aggregate and converting the reactive vaterite to aragonite, wherein the aragonite sets, hardens and bonds to the Portland cement.

14. The method according to claim 1, wherein the amount of aggregate is 25% to 80% of the weight of the precipitated material.

15. The method according to claim 1, further comprising the step of adding an additive to the aqueous solution or precipitate containing a calcium salt, wherein the additive is selected from the group consisting of fatty acid esters, sodium decyl sulfate, lauric acid, sodium salt of lauric acid, urea, citric acid, sodium salt of citric acid, phthalic acid, sodium salt of phthalic acid, taurine, creatine, glucose, poly(n-vinyl-1-pyrrolidone), aspartic acid, sodium salt of aspartic acid, magnesium chloride, acetic acid, sodium salt of acetic acid, glutamic acid, sodium salt of glutamic acid, strontium chloride, gypsum, lithium chloride, sodium chloride, glycine, anhydrous sodium citrate, sodium bicarbonate, magnesium sulfate, magnesium acetate, sodium polystyrene, sodium dodecyl sulfonate, polyvinyl alcohol, and combinations thereof.

16. The method according to claim 1, further comprising the step of mixing the precipitate with an admixture selected from the group consisting of a setting accelerator, a setting retarder, an air entrainer, a foaming agent, an antifoaming agent, an alkali reactivity reducing agent, a binding admixture, a dispersant, a coloring admixture, a corrosion inhibitor, a moisture-proof admixture, a gas-forming agent, a permeability reducing agent, a pumping aid, a shrinkage-correcting admixture, a fungicidal admixture, a bactericidal admixture, an insecticidal admixture, a rheological modifier, a finely ground mineral admixture, a pozzolane, an aggregate, a wetting agent, a strength enhancer, a water-repellent agent, a reinforcing material, and combinations thereof.

17. The method according to claim 16, wherein the reinforcing material is a fiber made from zirconia, aluminum, glass, steel, carbon, ceramic, grass, bamboo, wood, glass fiber, synthetic material, or a combination thereof.

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