Passive and forced synthesis of Mg (OH) 2 for magnesium-based CO2 capture

Abstract

The invention relates to a method for capturing carbon dioxide and sequestering carbon dioxide as calcium carbonate. The method involves using an aqueous magnesium hydroxide solution as a carbon dioxide absorbing fluid. Magnesium hydroxide in the absorption fluid is produced by two different pathways, i.e., a forced decomposition pathway and a passive dissolution pathway. Combined use of a forced decomposition pathway and a passive dissolution pathway is an important contribution factor to low energy loss in carbon dioxide capture and sequestration methods.

Description

[0001] Specification

[0002] Cross - Reference to Related Applications

[0003] This application claims the benefit of priority of U.S. Provisional Patent Application Serial No. 63 / 400,604, filed Aug. 24, 2022, the entire contents of which are incorporated herein by reference. Technical Field

[0004] The present invention generally relates to methods for capturing and sequestering carbon dioxide. Background Art

[0005] The vast majority of energy use in the United States and globally is based on the combustion of non - renewable fossil fuels, which results in the emission of carbon dioxide (CO 2 ) into the atmosphere. The continuous and increasing release of carbon dioxide into the atmosphere has been shown to have a negative impact on the climate. Since 1880, the Earth's temperature has risen 0.14°F (0.08°C) per decade, but since 1981 the warming rate has more than doubled to 0.32°F (0.18°C) per decade. The nine years from 2013 to 2021 rank among the ten warmest years on record. Although many alternatives to combustion are being considered, the fact is that combustion will still be a major component of the global energy system for decades to come.

[0006] Energy - efficient and scalable carbon dioxide capture is one of the greatest challenges facing modern energy researchers. The idea of separating carbon dioxide from flue gas was initially a means of recovering economically valuable carbon dioxide to increase oil yields. The power industry explored the use of different chemical sorbents and found that monoethanolamine is a functional capture agent. Using amine to capture carbon dioxide was considered an early technology but was considered unacceptable due to material costs and high energy losses. Since then, the technology has been improved; however, it still suffers from high costs and low efficiency.

[0007] The impact of the continuous emission of carbon dioxide into the atmosphere remains one of the most intractable problems facing humanity. Existing carbon capture technologies are expensive and energy - intensive and require new developments to increase efficiency and attract investors. The industry needs energy - efficient and negative - carbon methods for capturing carbon dioxide. Summary of the Invention

[0008] Alkaline solutions, such as monoethanolamine solutions, act as sinks for capturing carbon dioxide and have been the focus of many emission reduction studies. For example, an aqueous solution of magnesium hydroxide is an alkaline solution that can capture gaseous carbon dioxide and seal it in the form of magnesium carbonate salts. Based on this principle, the inventors have designed a hybrid carbon dioxide capture and sequestration method that uses two different approaches to produce the carbon dioxide capture agent magnesium hydroxide. These two different approaches include a forced decomposition approach and a passive dissolution approach. The forced decomposition approach involves the high-temperature decomposition of magnesium chloride hydrate to produce magnesium hydroxide. The passive dissolution approach involves the dissolution of mineral oxides, which immediately forms hydroxides and produces chloride salts from mineral oxides; in this method, the SkyCycle process sequence is used to produce magnesium chloride spontaneously produced from the precipitation process in the same SkyCycle sequence to produce two chemicals required for capture (magnesium hydroxide) and precipitation (calcium) for use in the process. These mineral oxides (CaO is the primary example for making high-quality calcium carbonate, but other Group II metal oxides or oxides of a 1:1 ratio of metal to oxygen (e.g., MgO or FeO, etc.) can be used for similar purposes), including geological minerals and industrial wastes, can be used for passive dissolution. In contrast, forced decomposition is not a spontaneous reaction process, requires a larger amount of energy (and a larger carbon footprint if that energy is provided by a carbon source), and requires multiple steps to complete the production of magnesium hydroxide and Group II chloride; specifically, MgCl 2 - The decomposition of the salts is carried out in two steps with different high heat requirements, requiring condensation and production of HCl acid by condensation of gaseous HCl, which then requires a different dissolution process that uses the generated HCl to remove the HCl from Ca / X-containing materials (especially not calcite (CaCO 3 )) or any carbonate source (where X is a metal or metalloid other than calcium) to produce CaCl 2 or XCl 2 By employing a combination of forced decomposition and passive dissolution pathways, the inventors have developed a CO2 capture and storage process with significantly lower energy penalties than other CO2 capture systems - with the added benefit that the forced decomposition system is operated by using available sources of metal oxides to complete the reaction, thereby forcing the process to remain in stoichiometric balance and operating as an industrial process will benefit from the low energy hydroxide / chloride production portion of the passive process, as all local / available minerals, oxides and wastes (e.g., ashes, slags, dust) can serve as resources for the process.

[0009] In this regard, a method for capturing carbon dioxide from a gas stream and sequestering carbon dioxide in the form of calcium carbonate is disclosed herein. In some aspects, the method includes: a first step of decomposing a material containing magnesium chloride to form a first mixture containing magnesium hydroxide and a second mixture containing gaseous hydrogen chloride and water; a second step of merging calcium oxide with a magnesium chloride brine to produce a third mixture containing magnesium hydroxide and calcium chloride; a third step of merging the first mixture and the third mixture to provide a fourth mixture containing magnesium hydroxide and calcium chloride; and a fourth step of contacting the fourth mixture with carbon dioxide to produce a product mixture containing calcium carbonate and an aqueous solution of magnesium chloride. In some aspects, substantially no heat is provided as an input to the second step. In some aspects, calcium carbonate is a solid precipitate and is separated from an aqueous solution of magnesium chloride. In some aspects, the aqueous solution of magnesium chloride is dehydrated to provide a material containing magnesium chloride. For example, the aqueous solution of magnesium chloride can be dehydrated to provide a magnesium chloride hydrate.

[0010] In some aspects, the fourth mixture comprises approximately equal amounts of magnesium hydroxide produced in the first step and magnesium hydroxide produced in the second step. In some aspects, the weight ratio of magnesium hydroxide produced in the first step to magnesium hydroxide produced in the second step contained in the magnesium hydroxide in the fourth mixture is any one of the following weight ratios, less than the following weight ratio, greater than the following weight ratio, between the following weight ratios, or any range thereof: 1:99, 2:98, 3:97, 4:96, 5:95, 6:94, 7:93; 8:92, 9:91, 10:90, 11:89, 12:88, 13:87, 14:86 、15:85、16:84、17:83、18:82、19:81、20:80、21:79、22:78、23:77、24:76、25:75、26:74、27:73、28:72、29:71、30:70、31:69、32:68、33:67、34:66、35:65、36:64、37:63、38:62、39:61、40:60、41:59、42:5 8, 43:57, 44:56, 45:55, 46:54, 47:53, 48:52, 49:51, 50:50, 51:49, 52:48, 53:47, 54:46, 55:45, 56:44, 57:43, 58:42, 59:41, 60:40, 61:39, 62:38, 63:37, 64:36, 65:35, 66:34, 67:33, 68:32, 69:31, 70: 30, 71:29, 72:28, 73:27, 74:26, 75:25, 76:24, 77:23, 78:22, 79:21, 80:20, 81:19, 82:18, 83:17, 84:16, 85:15, 86:14, 87:13, 88:12, 89:11, 90:10, 91:9, 92:8, 93:7, 94:6, 95:5, 96:4, 97:3, 98:2 and 99:1.

[0011] In some aspects, the material containing magnesium chloride is magnesium chloride hydrate. Magnesium chloride hydrate may include magnesium chloride dodecahydrate, octahydrate, hexahydrate, tetrahydrate, dihydrate, and combinations thereof. In some aspects, magnesium chloride hydrate includes magnesium chloride tetrahydrate or magnesium chloride dihydrate. In some aspects, magnesium chloride hydrate contains 2.0-2.1 molar equivalents of hydration water. All of these forms of magnesium chloride can be used in forced decomposition and passive dissolution methods to produce magnesium hydroxide and the corresponding metal oxide chloride used. Passive dissolution can be achieved in magnesium chloride brine; forced decomposition can only be accomplished with a crystalline form of magnesium chloride. Eliminating the energy required for crystallization and decomposition of magnesium chloride salts (because the passive dissolution step is spontaneous and does not require such energy) is a major contributing factor to the low energy combination of these two processes in the precursor chemicals provided to the SkyCycle process.

[0012] In some aspects, the first mixture contains substantially no magnesium hydroxychloride. In some aspects, the first mixture contains substantially no magnesium oxide. In some aspects, the magnesium chloride-containing material decomposed in the first step contains at least a portion of the magnesium chloride produced in the fourth step.

[0013] In some aspects, calcium-containing mineral or industrial material contacts with acid to produce calcium oxide. In some aspects, calcium-containing mineral is selected from the group consisting of tricalcium silicate, jaffite, perlite, vermiculite, diopside, tremolite, its combination or any other calcium-containing silicate mineral. In some embodiments, calcium-containing industrial material comprises masonry, concrete, steelmaking slag, biomass fuel production slag, discarded fly ash, its combination and other waste materials containing minerals. In some aspects, acid is selected from the group consisting of hydrochloric acid, sulfuric acid and nitric acid. In some aspects, at least a portion of the acid for dissolving calcium-containing mineral or industrial material is obtained from the decomposition of magnesium chloride-containing material. In some aspects, the CaO produced by dissolving calcium-containing mineral or waste material is used as the input raw material of second step.

[0014] It is specifically contemplated that any limitation discussed with respect to one embodiment of the invention may apply to any other embodiment of the invention. In addition, any composition of the invention may be used in any method of the invention, and any method of the invention may be used to produce or utilize any composition of the invention.

[0015] Through the following detailed description, other purposes, features and advantages of the present invention will become apparent. However, it should be understood that, although preferred embodiments of the present invention are shown, the detailed description and specific examples are given by way of illustration only, because various changes and modifications within the spirit and scope of the present invention will be apparent to those skilled in the art from the detailed description. DETAILED DESCRIPTION

[0016] A. Definition

[0017] As used herein, the term "carbonate" or "carbonate product" is generally defined as a carbonate containing a carbonate group [CO 3 ] 2- The terms "bicarbonate" and "bicarbonate product" are generally defined as any product containing a bicarbonate group [HCO 3 ] 1- These terms therefore include both carbonate / bicarbonate mixtures and species containing only bicarbonate ions.

[0018] As used herein, "Ca / Mg" means Ca alone, Mg alone, or a mixture of Ca and Mg. The ratio of Ca to Mg may range from 0:100 to 100:0, including, for example, 1:99, 2:98, 3:97, 4:96, 5:95, 6:94, 7:93, 8:92, 9:91, 10:90, 11:89, 12:88, 13:87, 14:86, 15:85, 16:84, 17:83, 18:82, 19:81, 20:80, 21:79, 22:78, 23:77、24:76、25:75、26:74、27:73、28:72、29:71、30:70、31:69、32:68、33:67、34:66、35:65、36:64、37:63、38:62、39:61、40:60、41:59、42:58、43:57、44:56、45:55、46:54、47:53、4 8:52、49:51、50:50、51:49、52:48、53:47、54:46、55:45、56:44、57:43、58:42、59:41、60:40、61:39、62:38、63:37、64:36、65:35、66:34、67:33、68:32、69:31、70:30、71:29、72:28、73 :27, 74:26, 75:25, 76:24, 77:23, 78:22, 79:21, 80:20, 81:19, 82:18, 83:17, 84:16, 85:15, 86:14, 87:13, 88:12, 89:11, 90:10, 91:9, 92:8, 93:7, 94:6, 95:5, 96:4, 97:3, 98:2 and 99:1. Symbols "Ca / Mg", "Mg x Ca (1-x) ” and “Ca x Mg (1-x)" are synonyms. The phrases "Group II" and "Group 2" are used interchangeably. Magnesium chloride hydrate refers to any hydrate, including but not limited to hydrates having 2, 4, 6, 8 or 12 equivalents of water per equivalent of magnesium chloride. The abbreviation "MW" means molecular weight or megawatt, depending on the context. The abbreviation "PFD" is a process flow diagram. The abbreviation "Q" is heat (or heat load), and heat is a type of energy. This does not include any other type of energy.

[0019] As used herein, the term "capture" is used generally to refer to technologies or practices whose partial or total effect is to remove carbon dioxide from point emissions. As used herein, the term "sequestration" is used generally to refer to technologies or practices whose partial or total effect is to store the captured carbon dioxide in some form to prevent it from returning to the atmosphere. The use of these terms does not preclude any form of the described embodiments from being considered as both capture and sequestration technologies.

[0020] The use of the word "a" or "an" when used in conjunction with the word "comprising" in the claims and / or the specification can mean "one", but it also has the meaning of "one or more", "at least one" and "one or more than one".

[0021] Throughout this application, the term "about" is used to indicate a value that includes the inherent variance of error for the device, the method being used to determine the value, or the variability that exists between study subjects.

[0022] The terms "comprise," "have," and "include" are open-ended linking verbs. Any form or tense of one or more of these verbs (such as "comprises," "comprising," "has," "having," "includes," and "including") are also open-ended. For example, any method that "comprises," "has," or "includes" one or more steps is not limited to having only those one or more steps, and may also cover other unlisted steps.

[0023] The above definitions supersede any conflicting definitions in any references incorporated herein by reference. However, the fact that certain terms are defined should not be construed as indicating that any undefined terms are undefined. Instead, all terms used are considered to describe the present invention in terms that enable a person of ordinary skill to understand the scope of the present invention and to practice the present invention.

[0024] Climate change is a defining issue of our time, and humanity is at a defining moment. From shifting weather patterns that threaten food production to rising sea levels that increase the risk of catastrophic flooding, the impacts of climate change are global and unprecedented in scale. After a century and a half of industrialization, deforestation, and large-scale agriculture, atmospheric carbon dioxide levels have risen to their highest levels in three million years. Carbon capture and storage is widely seen as a key strategy for limiting carbon dioxide emissions to the atmosphere from power plants and other large industrial sources.

[0025] Over the past 30 years, a lot of effort has been invested in improving the technical feasibility of various CO2 capture and storage methods. The main drawbacks of CO2 capture processes are their high cost and energy requirements, and extensive research has been devoted to addressing energy use, operational considerations, product value, and economics to obtain a profitable business model. One of the potential decarbonization technologies is mineral carbonation, which can reproduce natural weathering on an industrial scale with faster kinetics and higher conversion efficiency.

[0026] While researching a mineral carbonation based carbon capture system, the inventors developed a unique method that uses a combination of two sources and processes to obtain magnesium hydroxide. The method uses a combination of passive dissolution and forced decomposition to provide magnesium hydroxide. The end result is a system that reduces reliance on forced decomposition of magnesium chloride while maintaining the required chloride balance.

[0027] The carbon capture system disclosed herein adopts a combination of a passive dissolution part and a forced decomposition part. In some embodiments, the passive dissolution part includes contacting a mineral-containing material, preferably a waste material containing a leachable mineral, with an acid and optionally water to leach mineral ion salts from the mineral material into a brine or slurry. The mineral ion salts from the brine or slurry can be used as carbon dioxide capture and / or carbon dioxide mineral storage reagents. In some embodiments, the waste material serves as a source of calcium cations, particularly calcium oxide. In some embodiments, the mineral-containing material comprises calcium oxide. In some embodiments, the mineral-containing material is or includes a calcium-containing silicate mineral. In some embodiments, the mineral-containing material includes tricalcium silicate, jaffite, perlite, vermiculite, diopside, tremolite, a combination thereof, or any other calcium-containing silicate mineral. In some embodiments, the mineral-containing material includes masonry, concrete, steelmaking slag, biomass fuel production slag, waste fly ash, a combination thereof, and other mineral-containing waste materials. In some embodiments, the calcium oxide obtained by the passive dissolution part can be combined with magnesium chloride to produce magnesium hydroxide and calcium chloride. The magnesium chloride can be obtained externally or internally from different parts of the carbon capture system. The reaction between calcium oxide obtained by passive dissolution and magnesium chloride is shown below.

[0028] CaO+MgCl2 +H 2 O→Mg(OH) 2 +CaCl 2 (1)

[0029] In some embodiments, the forced decomposition part includes heat conduction driven decomposition of magnesium chloride. In some embodiments, magnesium chloride hydrate is used, and any hydrated form of magnesium chloride can be used, including magnesium chloride dodecahydrate, magnesium chloride octahydrate, magnesium chloride hexahydrate, magnesium chloride tetrahydrate and magnesium chloride dihydrate. In some embodiments, magnesium chloride dihydrate is selected as the starting material.

[0030] The formation enthalpy of magnesium chloride (Δ f H° solid) is -601.58 kJ / mol. f H° solid is -924.66 kJ / mol. Because solid magnesium hydroxide is at an energy trough relative to the magnesium chloride starting material, heat can be collected from the decomposition of magnesium chloride into magnesium hydroxide. The collected heat can be used internally, helping to reduce energy losses in the CO2 capture and storage process. The enthalpy difference between the initial and final stages in the above equation is 0.0465 kWh, excluding the enthalpy of the exothermic HCl absorption into water, which is approximately 55 kJ / mol HCl. This includes the formation of 2 moles of HCl, which is 110 kJ (0.031 kWh). The total is 0.0155 kWh. Each mole of magnesium hydroxide reacts with one mole of CO 2 Reaction, 0.0155 / 0.044=0.35kWh / kg CO 2 As the minimum theoretical energy requirement.

[0031] In some embodiments, the magnesium chloride forced decomposition process is conducted in a manner to avoid the formation of magnesium hydroxychloride partial decomposition products. The magnesium chloride forced decomposition process is conducted so that the decomposition reaction is substantially complete and the magnesium hydroxide product is substantially free of magnesium hydroxychloride.

[0032] In some aspects, the magnesium chloride forced decomposition process is performed in a manner to avoid the formation of magnesium oxide decomposition products. The magnesium chloride forced decomposition process is performed so that the magnesium hydroxide product is substantially free of magnesium oxide. Magnesium oxide is a dehydrated form of magnesium hydroxide (Mg(OH) 2 ≡MgO+H 2 O). Additional energy is required to remove individual water molecules from magnesium hydroxide and produce magnesium oxide. Using magnesium hydroxide as an intermediate and avoiding the forced decomposition part to completely dehydrate magnesium to magnesium oxide can save energy and contribute to low energy loss of the CO2 capture and storage process.

[0033] The magnesium hydroxide produced by the forced decomposition of magnesium chloride can be combined with the magnesium hydroxide produced by the reaction of magnesium chloride and calcium oxide, i.e., the passive dissolution product (Reaction 1 above). The combined magnesium hydroxide (in solution) can then be used as an absorption fluid for absorbing carbon dioxide.

[0034] Combining the magnesium hydroxide obtained by passive dissolution with the magnesium hydroxide obtained by the forced decomposition of magnesium chloride allows for a reduction in the amount of magnesium chloride decomposed. Reducing the amount of magnesium chloride decomposed lowers the total energy input required for the decomposition of magnesium chloride. Reducing the total energy input required for the decomposition of magnesium chloride contributes to a favorable thermodynamic energy loss in the carbon capture process.

[0035] Combining the magnesium hydroxide obtained by passive dissolution with the magnesium hydroxide obtained by the forced decomposition of magnesium chloride enables a carbon dioxide capture and sequestration system to utilize mineral-containing materials that might otherwise be disposed of as unwanted waste materials. Using waste materials as a source of minerals contributes to the eco-friendly nature of the carbon capture process.

[0036] The magnesium hydroxide obtained by the combination of passive dissolution and forced decomposition can be combined with water and exposed to flue gas in a bubble column. Compressing the flue gas requires energy, and the flue gas contains approximately 12% - 19% carbon dioxide and additional components, with nitrogen being the major additional component. At least a portion of the carbon dioxide in the flue gas is absorbed into the magnesium hydroxide solution (i.e., the absorption fluid) and initially forms magnesium carbonate. The calcium chloride present in the absorption fluid reacts with the magnesium carbonate through an "ion conversion" reaction and forms calcium carbonate. The calcium carbonate spontaneously precipitates out of the solution, leaving magnesium chloride in the solution. The calcium chloride solution in the absorption fluid is an indirect product of passive dissolution; however, additional calcium chloride can be added to the absorption fluid. Obtaining calcium chloride from the passive dissolution of industrial waste materials contributes to the eco-friendly nature of the carbon capture process. The solid precipitated calcium carbonate (PCC) is then separated, yielding PCC and a magnesium chloride solution. Various methods can be used to separate the PCC from the solution. In one example, the PCC and the solution are separated by passive hydrostatic pressure, i.e., natural drainage by filtration under hydrostatic head pressure. The spontaneous formation of PCC is exothermic, and the heat released from this reaction can be recovered. The heat recovered from the "ion conversion" reaction for the formation of calcium chloride contributes to reducing the energy loss in the carbon capture process. The recovered heat can be used internally to generate steam, thus contributing to a favorable thermodynamic energy loss in the carbon capture process.

[0037] The magnesium chloride solution can be dehydrated to regenerate magnesium chloride or its hydrate. In an exemplary dehydration process, waste heat from a co-operating facility or process can be used to drive the removal of water. In one embodiment, steam can be used to remove water from the magnesium chloride solution. In this exemplary process, a two-step dehydration method is adopted, wherein a boiler / evaporator is used to remove at least a portion of the water from the magnesium chloride solution in the first step, and a spray dryer is used to remove at least a portion of the remaining water in the second step. A boiler / evaporator can be used to remove at least a portion of the water in the magnesium chloride solution to produce an intermediate fluid with approximately three molar equivalents of hydrated water. The intermediate fluid can then be transferred to a spray dryer and heated to a temperature of ≥105°C. The fluid can then be flashed under pressure, during which water / steam is separated as steam, and magnesium chloride hydrate crystals with approximately 2.0-2.1 molar equivalents of hydrated water are collected. Heat recovered from various stages of the carbon dioxide capture and sequestration process or from a co-operating facility can be used in an evaporation step or a spray drying step to dehydrate the magnesium chloride solution. For example, steam generated by the recovered heat can be used to heat a drying gas for spray drying the magnesium chloride solution. The spray drying conditions can be adjusted to regenerate solid magnesium chloride having a desired degree of hydration. The regenerated magnesium chloride hydrate can then be transferred to a magnesium chloride forced decomposition reactor for decomposition.

[0038] In some embodiments, the carbon dioxide capture and storage process uses carbon dioxide collected from a carbon dioxide emission source (e.g., from the flue gas of a power generation facility). In some embodiments, heat is collected from the flue gas of the carbon dioxide emission source. Traditionally, the flue gas of a power generation facility is discharged into the atmosphere. Flue gas contains water in the form of carbon dioxide, water vapor or steam, and other gases. These waste flue gases can be used to recover heat. The carbon dioxide capture and storage process described herein can utilize external co-generated heat to further reduce energy input requirements. The recovered heat can then be used to generate electricity, provide power for a compressor, generate steam and / or increase the temperature of steam. Excess heat from various high-heat parts can be utilized and directed to heat input or heat absorption (negative heat) parts. By connecting various process parts with excess heat and insufficient heat, dependence on external heat sources is reduced. This reduces process net energy loss and also reduces energy input costs because the use of external energy sources is reduced. In general, carbon sequestration and heat recovery and transfer parts provide efficient carbon dioxide capture and storage processes with very low energy losses.

Claims

1. A method to capture CO from gas streams 2 And CaCO 3 The CO is stored in the form of 2 method, the method include: (a) Decomposition of MgCl 2 to form a material containing Mg(OH) 2 The first mixture and the mixture comprising HCl and H 2 A second mixture of O; (b) CaO and MgCl 2 The brines are combined to produce a Mg(OH) 2 and CaCl 2 a third mixture of (c) combining the first mixture and the third mixture to provide a 2 and CaCl 2 A fourth mixture of (d) mixing the fourth mixture with CO 2 contact to produce a CaCO 3 and MgCl 2 The product mixture is an aqueous solution.

2. The method of claim 1, wherein substantially no heat input is provided into step (b).

3. The method of claim 1, wherein the Mg(OH) in step (c) 2 Contains approximately the same amount of Mg(OH) produced in step (a) 2 and Mg(OH) produced in step (b) 2 .

4. The method of claim 1, wherein the MgCl 2 The material is MgCl 2 Hydrate.

5. The method of claim 4, wherein the MgCl 2 Hydrates contain 2.0-2.1 molar equivalents of water of hydration.

6. The method of claim 1, wherein the first product mixture comprises substantially no Mg(OH)Cl.

7. The method of claim 1, wherein the MgCl 2 The material comprises MgCl produced in step (d) 2 at least a portion of.

8. The method of claim 1, further comprising dissolving calcium-containing minerals or calcium-containing waste materials with an acid to produce CaO.

9. A method as claimed in claim 8, wherein CaO produced from the dissolution of calcium-containing minerals or calcium-containing waste materials is used as input to step (b).

10. The method of claim 8, wherein the acid is hydrochloric acid, nitric acid or sulfuric acid.

11. The process of claim 9, wherein at least a portion of the hydrochloric acid is obtained from step (a).

12. The method of claim 8, wherein the calcium-containing mineral is selected from the group consisting of tricalcium silicate, jaffite, perlite, vermiculite, diopside, tremolite, and combinations thereof.

13. The method of claim 8, wherein the calcium-containing waste material is selected from the group consisting of masonry, concrete, steelmaking slag, biomass fuel production slag, waste fly ash, and combinations thereof.