Method and system for preparing vaterite type calcium carbonate from waste incineration fly ash

Abstract

The invention belongs to the technical field of solid waste resource utilization, and relates to a method and system for preparing vaterite type calcium carbonate from waste incineration fly ash. The method comprises the following steps: by taking ammonium chloride as a leaching agent, leaching the waste incineration fly ash in a leaching agent solution, and then carrying out solid-liquid separation to obtain a calcium solution; and carrying out carbonation reaction on the calcium solution, an alkaline compound, sodium dodecyl benzene sulfonate and carbon dioxide under the conditions that the pressure intensity is 0.5-0.7 MPa and the temperature is 25-180 DEG C for 60-90 minutes to obtain the calcium carbonate. According to the method, high-quality vaterite type calcium carbonate can be prepared at a high conversion rate, the risk of fly ash is reduced, and mineralization of carbon dioxide is realized, so that waste is treated by waste, and green production is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste resource utilization, and relates to a method and system for preparing vaterite-type calcium carbonate by burning fly ash from garbage incineration. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Fly ash from the incineration of domestic waste (referred to as fly ash) has the characteristics of high salt content and contains a variety of toxic substances such as heavy metals and dioxins, so it is classified as hazardous waste. At present, the main disposal method for fly ash is safe landfill, but the toxicity of water-soluble salts, heavy metal pollution and dioxins has not been completely eliminated. From the composition of fly ash, the calcium content is also very high compared to other components, so calcium is a beneficial element with high potential resource utilization value.

[0004] Calcium carbonate products are mainly used as fillers and additives, so fly ash can be used as a raw material for the production of calcium carbonate products. The crystal forms of calcium carbonate include calcite, aragonite and vaterite. In the study, it was found that vaterite has the characteristics of large specific surface area, good dispersibility, uniform spherical size distribution, etc., and its ability to improve the filling performance of products such as inks, plastics, paper, and coatings, as well as the ability to improve product fluidity and gloss is significantly better than the other two crystal forms of calcium carbonate. However, compared with other crystal forms, the thermodynamic properties of vaterite are unstable and belong to a metastable crystal structure. It is easy to be converted into calcite or aragonite with a more stable crystal structure during the preparation process, making it difficult to obtain high-quality vaterite calcium carbonate. At the same time, the main morphology of vaterite calcium carbonate is spherical, and there are also disc-shaped, flake-shaped, hexagonal, lens-shaped and other morphologies. Therefore, although fly ash can be used as a raw material for the production of calcium carbonate products, due to the large number of impurities in fly ash and the instability of vaterite calcium carbonate, it is difficult to obtain high-quality vaterite calcium carbonate from fly ash with high efficiency. Summary of the invention

[0005] In order to overcome the deficiencies of the prior art, the present invention aims to provide a method and system for preparing vaterite-type calcium carbonate from waste incineration fly ash. The present invention provides a new method for resource utilization of fly ash, which can prepare high-quality vaterite-type calcium carbonate with a high conversion rate, not only reduces the danger of fly ash, but also realizes the mineralization of carbon dioxide, thereby achieving waste treatment and green production.

[0006] In order to achieve the above object, the technical solution of the present invention is:

[0007] In the first aspect, a method for preparing vaterite-type calcium carbonate from waste incineration fly ash comprises the following steps:

[0008] Using ammonium chloride as a leaching agent, placing the waste incineration fly ash in a leaching agent solution for leaching, and then separating the solid and liquid to obtain a calcium solution;

[0009] The calcium solution, alkaline compound, sodium dodecylbenzene sulfonate and carbon dioxide are subjected to carbonation reaction for 60 to 90 minutes at a pressure of 0.5 to 0.7 MPa and a temperature of 25 to 180° C. to obtain the product.

[0010] The invention selects ammonium chloride as the leaching agent. During the leaching process, the ammonium ions in the leaching solution make the reaction system have a certain buffering capacity. When the ammonium chloride solution leaches the fly ash, the entire leaching system is alkaline with a pH value between 8 and 9. A small amount of other metal ions in the fly ash are leached out, but most of them remain in the fly ash slag, so that the ammonium chloride solution has selectivity for the calcium-containing components in the fly ash, which not only improves the leaching efficiency, but also increases the content of calcium ions in the calcium solution, thereby providing a basis for preparing vaterite-type calcium carbonate with a high conversion rate of fly ash.

[0011] At present, carbonation method (or carbonization method) is one of the main methods for preparing vaterite calcium carbonate. Its essence is to use CO2 gas to dissolve in alkaline solution to obtain CO3 2- With Ca in solution 2+ The precipitation reaction occurs to prepare calcium carbonate. The dissolution rate and dispersion of CO2 gas in water are low. Therefore, the yield and efficiency of preparing vaterite calcium carbonate by this method are low. In order to increase the mass transfer rate and dispersion of CO2 gas in the solution, the generally used method is to add a gas disperser (or gas distributor) for bubbling. However, in any case, the calcium ion concentration directly affects the CO3 in the solution. 2- Therefore, carbonation usually requires the use of lower concentrations of Ca 2+ However, in order to improve the conversion rate of fly ash into vaterite calcium carbonate, the calcium ion content in the calcium solution must be increased when leaching calcium ions from fly ash. Therefore, the existing carbonation method is not conducive to achieving the purpose of preparing vaterite calcium carbonate with a high conversion rate of fly ash.

[0012] The present invention changes the pressure of the reaction system so that the reaction system is under high pressure conditions; at the same time, the present invention uses sodium dodecylbenzenesulfonate as a crystal form control agent, which can react with Ca 2+There is a strong electrostatic interaction between the two, which can form a strong Ca-O bond, inhibit the growth of certain specific crystal faces, and is conducive to the efficient formation of vaterite. The greater the concentration, the more obvious the inhibitory effect. Therefore, the present invention can cooperate with sodium dodecylbenzene sulfonate under high pressure conditions in the reaction process, not only can the calcium solution with high calcium concentration be used to prepare vaterite calcium carbonate, which is conducive to the high conversion of fly ash to prepare vaterite calcium carbonate, but also the prepared vaterite calcium carbonate has high calcium carbonate content, high whiteness, few black spots and other high-quality characteristics, which is conducive to further improving the value of vaterite calcium carbonate.

[0013] In addition, since the leaching system is alkaline, the calcium solution prepared therefrom is also alkaline, so the amount of alkaline compounds added can be greatly reduced in the subsequent carbonation process, thereby saving costs.

[0014] On the other hand, a system for preparing vaterite-type calcium carbonate from waste incineration fly ash is used to implement the above method, comprising:

[0015] A leaching device, configured to place the waste incineration fly ash in a leaching agent solution for leaching;

[0016] A first solid-liquid separation device, configured to perform solid-liquid separation on the material after the leaching device;

[0017] The high-pressure reaction device is configured to carry out a carbonation reaction on the calcium solution obtained by the solid-liquid separation device, an alkaline compound, sodium dodecylbenzene sulfonate and carbon dioxide.

[0018] The beneficial effects of the present invention are:

[0019] (1) The present invention can selectively leach calcium in fly ash by selecting ammonium chloride as the leaching agent, thereby efficiently leaching calcium ions in the fly ash to obtain a high-concentration calcium solution, and then under high pressure conditions, in combination with sodium dodecylbenzene sulfonate as a crystal form control agent, the calcium is efficiently converted into high-quality vaterite-type calcium carbonate.

[0020] (2) The method provided by the present invention not only realizes the resource utilization of waste incineration fly ash, but also uniformly introduces carbon dioxide in the carbonation stage to obtain uniformly distributed vaterite-type calcium carbonate, thereby realizing the mineralization of carbon dioxide. The obtained vaterite-type calcium carbonate has the advantages of high calcium carbonate content, high whiteness, and few black spots.

[0021] (3) The method of the present invention has low energy and material consumption, high CO2 mineralization efficiency, simple process, and recycled chloride salts. The carbonized leaching solution and leaching residue are treated to achieve a waste-free experiment, which is easy to realize industrial production and can achieve high-value utilization of solid waste. It has good environmental benefits and broad market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0023] Figure 1 This is a flow chart of preparing vaterite-type calcium carbonate from waste incineration fly ash in an embodiment of the present invention;

[0024] Figure 2 The mineral composition diagram of the calcium carbonate product prepared in the embodiment of the present invention;

[0025] Figure 3 This is a surface morphology of the calcium carbonate product prepared in Example 1 of the present invention;

[0026] Figure 4 This is a surface morphology of the calcium carbonate product prepared in Example 2 of the present invention;

[0027] Figure 5 This is a surface morphology of the calcium carbonate product prepared in Example 3 of the present invention;

[0028] Figure 6 This is a surface morphology of the calcium carbonate product prepared in Example 4 of the present invention;

[0029] Figure 7 This is a surface morphology of the calcium carbonate product prepared in Example 5 of the present invention. DETAILED DESCRIPTION

[0030] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0031] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0032] In view of the problem that it is difficult to efficiently prepare high-quality vaterite calcium carbonate using fly ash in the prior art, the present invention proposes a method and system for preparing vaterite calcium carbonate from waste incineration fly ash.

[0033] A typical embodiment of the present invention provides a method for preparing vaterite-type calcium carbonate from waste incineration fly ash, comprising the following steps:

[0034] Using ammonium chloride as a leaching agent, placing the waste incineration fly ash in a leaching agent solution for leaching, and then separating the solid and liquid to obtain a calcium solution;

[0035] The calcium solution, alkaline compound, sodium dodecylbenzene sulfonate and carbon dioxide are subjected to carbonation reaction for 60 to 90 minutes at a pressure of 0.5 to 0.7 MPa and a temperature of 25 to 180° C. to obtain the product.

[0036] In some embodiments, during leaching, the liquid-to-solid ratio of the leaching agent solution to the waste incineration fly ash is 10-60 mL / g, and the concentration of the leaching agent solution is 1-5 mol / L. Specifically, the liquid-to-solid ratio is 30-50 mL / g. Specifically, the concentration of the leaching agent solution is 1-2 mol / L. Studies have shown that the effect of leaching calcium ions is better under this condition.

[0037] In some embodiments, the leaching temperature is 25-85°C, and the leaching time is 20-140 min. Specifically, the leaching temperature is preferably 25-45°C. Specifically, the leaching time is 60-80 min. Studies have shown that the effect of leaching calcium ions is better under this condition.

[0038] In some embodiments, the pH of the leaching system is 8 to 9. Under this condition, the selectivity of leaching calcium is improved.

[0039] In some embodiments, the leaching is followed by static precipitation, and then solid-liquid separation is performed to obtain a calcium solution and ash. Specifically, the ash is dried, ground, and solidified and stabilized before landfill.

[0040] In some embodiments, the calcium ion concentration in the calcium solution is 4000-8000 mg / L, preferably 4500-7500 mg / L.

[0041] The alkaline compound of the present invention is a compound that is alkaline after being dissolved in water, and can be an inorganic substance or an organic substance. In some embodiments, the alkaline compound is ammonia water, caustic soda or triethanolamine. Preferably, it is ammonia water. The mass concentration of the ammonia water of the present invention is 5 to 25%, preferably 20 to 25%. Specifically, the volume ratio of the calcium solution to the ammonia water is 50:3 to 5.

[0042] In some embodiments, the volume ratio of the calcium solution to the mass ratio of sodium dodecylbenzene sulfonate is 50 mL: 0.05-0.15 g.

[0043] In some embodiments, the temperature of the carbonation reaction is 80-100°C.

[0044] In some embodiments, solid-liquid separation is performed after the carbonation reaction, and the separated solid is dried to obtain vaterite-type calcium carbonate.

[0045] In some embodiments, solid-liquid separation is performed after the carbonation reaction, sodium sulfide is added to the separated liquid and mixed evenly to obtain a turbid liquid, the turbid liquid is filtered, and the filtered liquid is evaporated, crystallized and recovered.

[0046] Another embodiment of the present invention provides a system for preparing vaterite-type calcium carbonate from waste incineration fly ash, which is used to implement the above method, comprising:

[0047] A leaching device, configured to place the waste incineration fly ash in a leaching agent solution for leaching;

[0048] A first solid-liquid separation device, configured to perform solid-liquid separation on the material after the leaching device;

[0049] The high-pressure reaction device is configured to carry out a carbonation reaction on the calcium solution obtained by the solid-liquid separation device, an alkaline compound, sodium dodecylbenzene sulfonate and carbon dioxide.

[0050] In some embodiments, a second solid-liquid separation device is further included, which is configured to perform solid-liquid separation on the material output from the high-pressure reaction device.

[0051] In some embodiments, a post-processing device is also included, which is configured to further process the liquid output by the second solid-liquid separation device.

[0052] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0053] The composition of the fly ash used in the following examples is shown in Table 1.

[0054] Table 1 Composition of raw fly ash

[0055]

[0056] Example 1

[0057] A method for preparing vaterite-type calcium carbonate from fly ash from garbage incineration, such as Figure 1 As shown, the steps are as follows:

[0058] (1) Dry the fly ash from the incineration of domestic waste in an oven at 105°C.

[0059] (2) The domestic waste incineration fly ash is leached with a 1 mol / L ammonium chloride solution, the leaching time is 60 min, the leaching liquid-to-solid ratio is 50 mL / g, the pH is 8.5, the leaching temperature is 45° C., and it is placed on a magnetic stirrer at a speed of 400 r / min for stirring, and a leaching experiment is performed to obtain a mixture.

[0060] (3) The mixture is allowed to settle and then solid-liquid is separated to obtain a calcium-rich solution and ash.

[0061] (4) Drying and grinding the ash, solidifying and stabilizing it before landfilling.

[0062] (5) 50 mL of the calcium-rich solution (calcium ion concentration of 4725.76 mg / L) was placed in a high-pressure reactor, the experimental temperature was 80° C., the experimental time was 80 min, the rotation speed was 400 r / min, and 4 mL of 25% ammonia water was added, pure CO2 was introduced, the pressure in the reactor was 0.6 MPa, and 0.1 g of a crystal form control agent, sodium dodecylbenzene sulfonate, was added, the lid of the high-pressure reactor was tightened, and a carbonation experiment was carried out to obtain a turbid liquid containing calcium carbonate.

[0063] (6) The turbid liquid is taken out, and the solid and liquid in the turbid liquid are separated by a suction filtration device, and the obtained white solid is placed in an oven for drying. That is, the white solid is a calcium carbonate sample, such as Figure 2 , 3 shown.

[0064] (7) Add 5% Na2S to the carbonated leaching solution, and mix them in a ratio of leaching solution: 5% Na2S = 4:1. Place the mixture on a magnetic stirrer and react for 3 h to fully mix the mixture and obtain a turbid solution.

[0065] (8) The turbid liquid is filtered to obtain a clear liquid, and its heavy metal concentration is tested to see if it complies with the "GB 8978-1996 Comprehensive Wastewater Discharge Standard", and then it is discharged. The leachate contains a large amount of chloride salt components, which are evaporated and crystallized for recovery.

[0066] Example 2

[0067] A method for preparing vaterite-type calcium carbonate from fly ash from garbage incineration, such as Figure 1 As shown, the steps are as follows:

[0068] (1) Dry the fly ash from the incineration of domestic waste in an oven at 105°C.

[0069] (2) The domestic waste incineration fly ash is leached with a 1 mol / L ammonium chloride solution, the leaching time is 60 min, the leaching liquid-to-solid ratio is 40 mL / g, the pH is 8.5, the leaching temperature is 25° C., and it is placed on a magnetic stirrer at a speed of 400 r / min for stirring, and a leaching experiment is performed to obtain a mixture.

[0070] (3) The mixture is allowed to settle and then solid-liquid is separated to obtain a calcium-rich solution and ash.

[0071] (4) Drying and grinding the ash, solidifying and stabilizing it before landfilling.

[0072] (5) 50 mL of the calcium-rich solution (calcium ion concentration of 5574.4 mg / L) was placed in a high-pressure reactor, the experimental temperature was 100° C., the experimental time was 80 min, the rotation speed was 400 r / min, and 4 mL of 25% ammonia water was added, pure CO2 was introduced, the pressure in the reactor was 0.6 MPa, and 0.1 g of a crystal form control agent, sodium dodecylbenzene sulfonate, was added, the lid of the high-pressure reactor was tightened, and a carbonation experiment was carried out to obtain a turbid liquid containing calcium carbonate.

[0073] (6) The turbid liquid is taken out, and the solid and liquid in the turbid liquid are separated by a suction filtration device, and the obtained white solid is placed in an oven for drying. That is, the white solid is a calcium carbonate sample, such as Figure 2 , 4 shown.

[0074] (7) Add 5% Na2S to the carbonated leaching solution, and mix them in a ratio of leaching solution: 5% Na2S = 4:1. Place the mixture on a magnetic stirrer and react for 3 h to fully mix the mixture and obtain a turbid solution.

[0075] (8) The turbid liquid is filtered to obtain a clear liquid, and its heavy metal concentration is tested to see if it complies with the "GB 8978-1996 Comprehensive Wastewater Discharge Standard", and then it is discharged. The leachate contains a large amount of chloride salt components, which are evaporated and crystallized for recovery.

[0076] Example 3

[0077] A method for preparing vaterite-type calcium carbonate from fly ash from garbage incineration, such as Figure 1 As shown, the steps are as follows:

[0078] (1) Dry the fly ash from the incineration of domestic waste in an oven at 105°C.

[0079] (2) The domestic waste incineration fly ash is leached with a 1 mol / L ammonium chloride solution, the leaching time is 80 min, the leaching liquid-to-solid ratio is 40 mL / g, the pH is 8.5, the leaching temperature is 25° C., and it is placed on a magnetic stirrer at a speed of 400 r / min for stirring, and a leaching experiment is performed to obtain a mixture.

[0080] (3) The mixture is allowed to settle and then solid-liquid is separated to obtain a calcium-rich solution and ash.

[0081] (4) Drying and grinding the ash, solidifying and stabilizing it before landfilling.

[0082] (5) 50 mL of the calcium-rich solution (calcium ion concentration of 5670.4 mg / L) was placed in a high-pressure reactor, the experimental temperature was 80° C., the experimental time was 90 min, the rotation speed was 400 r / min, and 4 mL of 25% ammonia water was added, pure CO2 was introduced, the pressure in the reactor was 0.6 MPa, and 0.1 g of a crystal form control agent, sodium dodecylbenzene sulfonate, was added, the lid of the high-pressure reactor was tightened, and a carbonation experiment was carried out to obtain a turbid liquid containing calcium carbonate.

[0083] (6) The turbid liquid is taken out, and the solid and liquid in the turbid liquid are separated by a suction filtration device, and the obtained white solid is placed in an oven for drying. That is, the white solid is a calcium carbonate sample, such as Figure 2 , 5 shown.

[0084] (7) Add 5% Na2S to the carbonated leaching solution, and mix them in a ratio of leaching solution: 5% Na2S = 4:1. Place the mixture on a magnetic stirrer and react for 3 h to fully mix the mixture and obtain a turbid solution.

[0085] (8) The turbid liquid is filtered to obtain a clear liquid, and its heavy metal concentration is tested to see if it complies with the "GB 8978-1996 Comprehensive Wastewater Discharge Standard", and then it is discharged. The leachate contains a large amount of chloride salt components, which are evaporated and crystallized for recovery.

[0086] Example 4

[0087] A method for preparing vaterite-type calcium carbonate from fly ash from garbage incineration, such as Figure 1 As shown, the steps are as follows:

[0088] (1) Dry the fly ash from the incineration of domestic waste in an oven at 105°C.

[0089] (2) The domestic waste incineration fly ash is leached with a 1 mol / L ammonium chloride solution, the leaching time is 70 min, the leaching liquid-to-solid ratio is 30 mL / g, the pH is 8.5, the leaching temperature is 35° C., and it is placed on a magnetic stirrer at a speed of 400 r / min for stirring, and a leaching experiment is performed to obtain a mixture.

[0090] (3) The mixture is allowed to settle and then solid-liquid is separated to obtain a calcium-rich solution and ash.

[0091] (4) Drying and grinding the ash, solidifying and stabilizing it before landfilling.

[0092] (5) 50 mL of the calcium-rich solution (calcium ion concentration of 7449.6 mg / L) was placed in a high-pressure reactor, the experimental temperature was 90° C., the experimental time was 100 min, the rotation speed was 400 r / min, and 4 mL of 25% ammonia water was added, pure CO2 was introduced, the pressure in the reactor was 0.6 MPa, and 0.1 g of a crystal form control agent, sodium dodecylbenzene sulfonate, was added, the lid of the high-pressure reactor was tightened, and a carbonation experiment was carried out to obtain a turbid liquid containing calcium carbonate.

[0093] (6) The turbid liquid is taken out, and the solid and liquid in the turbid liquid are separated by a suction filtration device, and the obtained white solid is placed in an oven for drying. That is, the white solid is a calcium carbonate sample, such as Figure 2 , 6 shown.

[0094] (7) Add 5% Na2S to the carbonated leaching solution, and mix them in a ratio of leaching solution: 5% Na2S = 4:1. Place the mixture on a magnetic stirrer and react for 3 h to fully mix the mixture and obtain a turbid solution.

[0095] (8) The turbid liquid is filtered to obtain a clear liquid, and its heavy metal concentration is tested to see if it complies with the "GB 8978-1996 Comprehensive Wastewater Discharge Standard", and then it is discharged. The leachate contains a large amount of chloride salt components, which are evaporated and crystallized for recovery.

[0096] Example 5

[0097] A method for preparing vaterite-type calcium carbonate from fly ash from garbage incineration, such as Figure 1 As shown, the steps are as follows:

[0098] (1) Dry the fly ash from the incineration of domestic waste in an oven at 105°C.

[0099] (2) The domestic waste incineration fly ash is leached with a 1 mol / L ammonium chloride solution, the leaching time is 60 min, the leaching liquid-to-solid ratio is 50 mL / g, the pH is 8.5, the leaching temperature is 45° C., and it is placed on a magnetic stirrer at a speed of 400 r / min for stirring, and a leaching experiment is performed to obtain a mixture.

[0100] (3) The mixture is allowed to settle and then solid-liquid is separated to obtain a calcium-rich solution and ash.

[0101] (4) Drying and grinding the ash, solidifying and stabilizing it before landfilling.

[0102] (5) 50 mL of the calcium-rich solution (calcium ion concentration of 4725.76 mg / L) was placed in a high-pressure reactor, the experimental temperature was 80° C., the experimental time was 90 min, the rotation speed was 400 r / min, and 4 mL of 25% ammonia water was added, pure CO2 was introduced, the pressure in the reactor was 0.6 MPa, and 0.1 g of crystal form control agent serine was added. The lid of the high-pressure reactor was tightened, and a carbonation experiment was carried out to obtain a turbid liquid containing calcium carbonate.

[0103] (6) The turbid liquid is taken out, and the solid and liquid in the turbid liquid are separated by a suction filtration device, and the obtained white solid is placed in an oven for drying. That is, the white solid is a calcium carbonate sample, such as Figure 2 , 7 shown.

[0104] (7) Add 5% Na2S to the carbonated leaching solution, and mix them in a ratio of leaching solution: 5% Na2S = 4:1. Place the mixture on a magnetic stirrer and react for 3 h to fully mix the mixture and obtain a turbid solution.

[0105] (8) The turbid liquid is filtered to obtain a clear liquid, and its heavy metal concentration is tested to see if it complies with the "GB8978-1996 Comprehensive Wastewater Discharge Standard", and then it is discharged. The leachate contains a large amount of chloride salt components, which are evaporated and crystallized for recovery.

[0106] After testing Examples 1, 2, 3, 4, and 5, the data obtained are as follows:

[0107] Table 2 Experimental data table of Examples 1, 2, 3, 4, and 5

[0108]

[0109] In the calcium carbonate of Example 4, the content of vaterite is 95%, and calcite is 5%. It is mainly due to the long time (100min) that the unstable vaterite type calcium carbonate develops to calcite. In the calcium carbonate of Example 5, calcite is 41.25%, aragonite is 35.61%, and vaterite is 23.14%.

[0110] Table 3 Calcium carbonate index data table of example samples

[0111]

[0112] As can be known from Table 2, the calcium ion leaching rate utilizing sodium chloride solution to leach the fly ash can reach 92.3%, illustrating that most calcium-containing components in the fly ash have been leached in the solution, and the carbonation rate of solution has also reached 96.87%, and the purity of calcium carbonate is also very high. In conjunction with Table 2 and Table 3, it can be seen that this method can prepare high-quality vaterite type calcium carbonate efficiently, the leaching rate of calcium ion in the fly ash is all more than 85%, the content of calcium carbonate is all more than 98% and is much greater than the requirement in " GB 8978-1996 ", and other indexes of calcium carbonate all meet the standard in " GB 8978-1996 ", so this method can make standard-compliant vaterite type calcium carbonate.

[0113] Depend on Figure 2 It can be seen that the crystal forms of the calcium carbonate samples in Examples 1 to 4 are all vaterite-type, and only a small amount of calcite is present in Example 4, but the crystal form of the sample is still mainly vaterite-type. Since the added crystal form control agent is changed in Example 5, calcium carbonate mainly composed of calcite and aragonite appears. Figure 7 It can be seen that in Example 5, cubic calcite and needle-shaped aragonite are the main components. Figure 3 It can be seen that the vaterite calcium carbonate of Example 1 is mainly in the shape of a disk, and there are some hexagonal columns, which is consistent with Figure 2 The XRD pattern of the embodiment 2 is consistent with that of the embodiment 3, and the vaterite calcium carbonate has a disc shape and a hexagonal shape. The calcium carbonate of embodiment 2 is the most common spherical vaterite calcium carbonate, such as Figure 4 shown. Figure 5 It can be seen that the sample of Example 3 is mainly flake-shaped vaterite-type calcium carbonate. Figure 2 It shows that the calcium carbonate sample in Example 4 is mainly vaterite type and calcite type. Figure 6 Spherical vaterite calcium carbonate and cubic calcite calcium carbonate can be seen; Figure 2 and Figure 3 In summary, the preparation of vaterite-type calcium carbonate from waste incineration fly ash is feasible and has high purity.

[0114] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing vaterite-type calcium carbonate from waste incineration fly ash, characterized in that: The steps include: Using ammonium chloride as a leaching agent, placing the waste incineration fly ash in a leaching agent solution for leaching, and then separating the solid and liquid to obtain a calcium solution; The calcium solution, alkaline compound, sodium dodecylbenzene sulfonate and carbon dioxide are subjected to carbonation reaction for 60 to 90 minutes at a pressure of 0.5 to 0.7 MPa and a temperature of 25 to 180° C. to obtain the product.

2. The method according to claim 1, characterized in that: During leaching, the liquid-solid ratio of the leaching agent solution to the waste incineration fly ash is 10-60 mL / g, and the concentration of the leaching agent solution is 1-5 mol / L; preferably, the liquid-solid ratio is 30-50 mL / g; preferably, the concentration of the leaching agent solution is 1-2 mol / L.

3. The method according to claim 1, characterized in that: The leaching temperature is 25-85°C, and the leaching time is 20-140 min; preferably, the leaching temperature is 25-45°C; preferably, the leaching time is 60-80 min.

4. The method according to claim 1, characterized in that: The pH of the leaching system is 8-9.

5. The method according to claim 1, characterized in that: After leaching, the mixture is allowed to settle and then solid-liquid separation is performed to obtain a calcium solution and ash residue. Preferably, the ash residue is dried, ground, and solidified and stabilized before being landfilled.

6. The method according to claim 1, characterized in that: The alkaline compound is aqueous ammonia, caustic soda or triethanolamine, preferably aqueous ammonia.

7. The method according to claim 1, characterized in that: After the carbonation reaction, solid-liquid separation is carried out, and the separated solid is dried to obtain vaterite-type calcium carbonate.

8. The method according to claim 1, characterized in that: After the carbonation reaction, solid-liquid separation is performed, sodium sulfide is added to the separated liquid and mixed evenly to obtain a turbid liquid, the turbid liquid is filtered, and the filtered liquid is evaporated and crystallized for recovery.

9. A system for preparing vaterite-type calcium carbonate from fly ash from garbage incineration, characterized in that: The method for implementing claim 1 comprises: A leaching device, configured to place the waste incineration fly ash in a leaching agent solution for leaching; A first solid-liquid separation device, configured to perform solid-liquid separation on the material after the leaching device; The high-pressure reaction device is configured to carry out a carbonation reaction on the calcium solution obtained by the solid-liquid separation device, an alkaline compound, sodium dodecylbenzene sulfonate and carbon dioxide.

10. The system according to claim 9, characterized in that: It also includes a second solid-liquid separation device, which is configured to perform solid-liquid separation on the material output from the high-pressure reaction device.

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