METHOD FOR INTEGRATED UTILIZATION OF CALCIUM CHLORIDE SOLUTION AND CARBON DIOXIDE

Abstract

The present invention provides a method for integrated utilization of a calcium chloride solution and CO.sub.2. In this method, with the calcium chloride solution and the CO.sub.2 being taken as raw materials, a water-soluble amine is added as an auxiliary agent to promote the occurrence of a mineralization reaction. As a result of crystallization following the reaction, calcium carbonate and a solution of a hydrochloride of the water-soluble amine are obtained. After the reaction is completed, the water-soluble amine is regenerated by subjecting a liquid phase resulting from separation to bipolar membrane electrodialysis, and dilute hydrochloric acid is obtained as a by-product at the same time. The method provides a novel perspective and approach to integrated utilization of calcium chloride-containing liquid waste and flue gas CO.sub.2. The water-soluble amine allows excellent mineralization, and the bipolar membrane electrodialysis enables excellent regeneration of the amine. By means of process regulation, a calcium carbonate product of high value with controlled morphology and particle size can be obtained. For applications equipped with a lime kiln and allowing recycling of calcium carbonate, such as the ammonia-soda industry, the present invention also provides a combined cycle process for carbon and calcium resources, in which calcium carbonate produced by a mineralization reaction is calcined in lieu of limestone used in the soda production process to provide the soda production process with CO.sub.2 and milk of lime, enabling recycling of carbon and calcium resources in an ammonia soda plant. The entire process is free of waste discharge, showing a promising prospect of application. It is of great significance to the fields of calcium chloride-containing liquid waste disposal and carbon emission reduction.

Claims

1. A method for integrated utilization of a calcium chloride solution and CO.sub.2, characterized in comprising: (1) taking the calcium chloride solution and the CO.sub.2 as raw materials, adding a water-soluble amine as an auxiliary agent to cause a mineralization reaction, which produces calcium carbonate and a hydrochloride of the water-soluble amine, and obtaining a calcium carbonate product from solid-liquid separation; (2) regenerating the water-soluble amine by subjecting a liquid phase from the separation to bipolar membrane electrodialysis and producing dilute hydrochloric acid as a by-product.

2. The method according to claim 1, characterized in that the calcium chloride solution is calcium chloride-containing liquid waste discharged from soda ash production based on the ammonia-soda process, or from production of dicalcium phosphate and potassium chlorate through extraction with hydrochloric acid from ground phosphate rock, or from polycrystalline silicon production and has a concentration of 0.1-3 mol/L, wherein the CO.sub.2 is from flue gas CO.sub.2 emitted from a power plant, a lime kiln or a carbonation tower and is present in the flue gas CO.sub.2 at a concentration of from 2% to 100%.

3. The method according to claim 1, characterized in that the mineralization reaction occurs at a temperature of 10-80? C., wherein: a molar ratio of calcium chloride to the water-soluble amine is 1:(0.4-10), preferably 1: (1-4); and the CO.sub.2 is added in such a manner that it is introduced into a solution of the water-soluble amine and then mixed with the calcium chloride-containing liquid waste to cause the mineralization reaction, or that it is introduced into the calcium chloride-containing liquid waste and then mixed with a solution of the water-soluble amine to cause the mineralization reaction, or that it is introduced into a mixed solution of a solution of the water-soluble amine and the calcium chloride-containing liquid waste to cause the mineralization reaction.

4. The method according to claim 1, characterized in that the water-soluble amine is selected from one or more of alkanolamine compounds, amino acid salt compounds, basic amino acid compounds, diamine compounds, polyamine compounds, aliphatic amine compounds, aromatic amine compounds, heterocyclic amine compounds and biogenic amine compounds.

5. The method according to claim 4, characterized in that the water-soluble amine is selected from one or more of monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), N-methyl diethanolamine (MDEA), 2-amino-2-methyl-1-propanol (AMP), sodium glycinate (GlyNa), arginine (Arg), piperazine (PZ), ethylenediamine (EDA), tetramethylethylenediamine (TEMED), triethylenetetramine (TETA), pyridine (PD), cadaverine, putrescine, spermine and spermidine.

6. The method according to claim 1, characterized in that the bipolar membrane electrodialysis is conducted with a device of a salt-acid-base three-chamber structure, or of a salt-acid two-chamber structure, wherein dilute hydrochloric acid is produced as a by-product in an acid chamber, and the water-soluble amine is regenerated in a base chamber or in a salt chamber in the form of a solution thereof, which is then circulated back to the mineralization process in step (1) for reuse.

7. The method according to claim 6, characterized in that, at the beginning of operation of the bipolar membrane electrodialysis device, there are a 0.01-2.00 mol/L HCl solution in the acid chamber, a 0.01-2.00 mol/L NaOH solution in the base chamber, a solution obtained as a liquid phase from the solid-liquid separation in the salt chamber, and a 0.01%-10% Na.sub.2SO.sub.4 solution in an electrode solution chamber, wherein there is a flow rate of 10-200 L/h in each chamber of the bipolar membrane electrodialysis device, and a constant current with a strength of 0.1-5.0 A is applied.

8. The method according to claim 2, characterized in that, the calcium chloride-containing liquid waste is liquid waste discharged from ammonia evaporation during soda ash production based on the ammonia-soda process, wherein the calcium carbonate produced by the mineralization reaction is calcined in place of limestone used in a soda production process based on the ammonia-soda process to provide the soda production process with CO.sub.2 and milk of lime, allowing recycling of calcium resources and CO.sub.2.

9. The method according to claim 8, characterized in that the flue gas CO.sub.2 is concentrated after being subjected to desulfurization and denitrification and then used to directly carbonate ammoniated brine in the soda production process to produce soda ash, and/or to treat liquid waste from the ammonia-soda process that has not been treated yet to produce a calcium carbonate product through mineralization.

10. The method according to claim 2, characterized in that, after being subjected to desulfurization and denitrification, the flue gas CO.sub.2 is compressed or not, and then introduced into a reaction solution system, wherein the flue gas CO.sub.2 is compressed to a pressure of up to 0.8 MPa.

11. The method according to claim 4, characterized in that when the water-soluble amine is selected from diamine compounds, the calcium carbonate product obtained in step (1) is calcium carbonate in the form of calcite.

12. The method according to claim 4, characterized in that when the water-soluble amine is selected from amino acid salt compounds and basic amino acid compounds, the calcium carbonate product obtained in step (1) is calcium carbonate in the form of vaterite.

13. The method according to claim 4, characterized in that when the water-soluble amine is selected from alkanolamine compounds, regulation is performed through a mineralization process comprising: when a molar ratio of the calcium chloride to the water-soluble amine is greater than 1:2, obtaining the calcium carbonate product in step (1) as calcium carbonate in the form of calcite, wherein the ratio of the two is preferred to be 1:(0.4-2), not including 1:2; when the materials are added so that a solution of the water-soluble amine is added to the calcium chloride solution, and when the CO.sub.2 is added in such a manner that it is introduced into the solution of the water-soluble amine and then mixed with calcium chloride-containing liquid waste, or that it is introduced into calcium chloride-containing liquid waste and then mixed with the solution of the water-soluble amine, obtaining the calcium carbonate product in step (1) as calcium carbonate in the form of calcite; when a molar ratio of the calcium chloride to the water-soluble amine is not greater than 1:2, when the materials are added so that the calcium chloride solution is added to a solution of the water-soluble amine, and when the CO.sub.2 is added in such a manner that it is introduced into the solution of the water-soluble amine and then mixed with calcium chloride-containing liquid waste, or that it is introduced into calcium chloride-containing liquid waste and then mixed with the solution of the water-soluble amine, obtaining the calcium carbonate product as calcium carbonate in the form of vaterite by running the mineralization reaction at a low temperature of 10-40? C., preferably 20-30? C., or obtaining the calcium carbonate product as calcium carbonate in the form of calcite by running the mineralization reaction at a high temperature of 50-80? C., preferably 60-70? C.

14. The method according to claim 1, characterized in that when the calcium chloride solution is mixed with a solution of the water-soluble amine by direct pouring, the calcium carbonate product is obtained in step (1) as calcium carbonate with a small particle size, which is calcium carbonate with an average particle size of smaller than 20 ?m, preferably calcium carbonate with an average particle size of smaller than 10 ?m, or when the calcium chloride solution is mixed with a solution of the water-soluble amine by dropwise addition, the calcium carbonate product is obtained in step (1) as calcium carbonate with a large particle size, which is calcium carbonate with an average particle size of greater than 10 ?m, preferably calcium carbonate with an average particle size of greater than 20 ?m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] FIG. 1 shows a flowchart of a process for integrated utilization of calcium chloride-containing liquid waste and flue gas CO.sub.2 according to the present invention.

[0051] FIG. 2 shows a flowchart of a process for producing soda ash based on the ammonia-soda process.

[0052] FIG. 3 shows a flowchart of a coupled carbon-calcium cycle process for the soda production industry based on the ammonia-soda process.

[0053] FIG. 4 is a schematic illustration of a coupled carbon-calcium cycle process for the soda production industry based on the ammonia-soda process.

[0054] FIG. 5 shows an XRD pattern of a calcium carbonate product prepared according to Example 2-1.

[0055] FIG. 6 shows an SEM image of the calcium carbonate product prepared according to Example 2-1.

[0056] FIG. 7 shows an XRD pattern of a calcium carbonate product prepared according to Example 3-1.

[0057] FIG. 8 shows an SEM image of the calcium carbonate product prepared according to Example 3-1.

[0058] FIG. 9 shows an XRD pattern of a calcium carbonate product prepared according to Example 4-1.

[0059] FIG. 10 shows an SEM image of the calcium carbonate product prepared according to Example 4-1.

[0060] FIG. 11 shows an XRD pattern of a calcium carbonate product prepared according to Example 4-2.

[0061] FIG. 12 shows an SEM image of the calcium carbonate product prepared according to Example 4-2.

[0062] FIG. 13 shows an XRD pattern of a calcium carbonate product prepared according to Example 4-5.

[0063] FIG. 14 shows an SEM image of the calcium carbonate product prepared according to Example 4-5.

[0064] FIG. 15 shows mobility profiles of Cl.sup.? in an acid chamber as a result of treating hydrochlorides of various water-soluble amines by bipolar membrane electrodialysis.

[0065] FIG. 16 shows residual rate profiles of Cl.sup.? in a salt chamber as a result of treating hydrochlorides of various water-soluble amines by bipolar membrane electrodialysis.

[0066] FIG. 17 shows amine regeneration rate profiles in a salt chamber as a result of treating hydrochlorides of various water-soluble amines by bipolar membrane electrodialysis.

DETAILED DESCRIPTION

[0067] The present invention will be clearly and fully described below with reference to the specific examples below. It would be appreciated that the examples described herein are only some, but not all, possible embodiments of the invention. It is intended that any and all other embodiments made by those of ordinary skill in the art in light of those disclosed herein without exerting any creative effort are embraced in the scope of the invention.

[0068] FIG. 1 shows a flowchart of a process for integrated utilization of calcium chloride-containing liquid waste and flue gas CO.sub.2 according to the present invention. With the calcium chloride-containing liquid waste and flue gas CO.sub.2 being used as raw materials, a water-soluble amine is added thereto as an auxiliary agent to promote a mineralization reaction. From filtration, solid calcium carbonate is obtained as a product, as well as a filtrate containing a hydrochloride of the water-soluble amine. In order to further recover the water-soluble amine and allow utilization of chlorine as resources without producing chlorine-containing liquid waste, the hydrochloride of the water-soluble amine is regenerated by bipolar membrane electrodialysis. As a result of the filtrate containing the hydrochloride of the water-soluble amine being added to a salt chamber, the regenerated water-soluble amine and dilute hydrochloric acid are simultaneously obtained in a salt chamber (or a base chamber) and an acid chamber, respectively. The regenerated water-soluble amine is circulated back to the mineralization section for reuse, and the dilute hydrochloric acid can be used in another workshop in the factory. The obtained calcium carbonate can be circulated to a limestone calcination section in a soda production line.

[0069] Alternatively, nano- or micro-sized calcium carbonate of high value with controlled morphology and particle size can be produced for sale, or for use in another workshop in the factory.

[0070] Reactions that occur respectively in the section for mineralization of CO.sub.2 with the water-soluble amine and in the section for amine regeneration by bipolar membrane electrodialysis can be described by the following equations:

CaCl.sub.2)+2RNH.sub.2+CO.sub.2+H.sub.2O.fwdarw.CaCO.sub.3?+2RNH.sub.2.Math.HCl RNH.sub.2.Math.HCl.fwdarw.RNH.sub.2+HCl

Example 1: Carbon-Calcium Cycle Process in Soda Production Industry Based on Ammonia-Soda Process

[0071] FIG. 2 shows a flowchart of a process for producing soda ash based on the ammonia-soda process, in which NH.sub.3 is introduced and absorbed in a saturated solution of common salt to obtain ammoniated brine, and CO.sub.2 is then further introduced to bring about a carbonation reaction. NaHCO.sub.3 is then obtained by crystallization, and the obtained NaHCO.sub.3 is filtered, separated and calcined, producing the soda ash product. CO.sub.2 is recycled, and NH.sub.3 is recovered by adding milk of lime to the filtrate that contains NH.sub.4Cl and then performing an ammonia evaporation process thereon. CaCl.sub.2)-containing liquid waste left from the ammonia evaporation process is directly discharged. The milk of lime is obtained from calcination and slaking of commercially available limestone, and CO.sub.2 produced during the calcination is also recycled. Reactions in each section of the soda ash production line based on the ammonia-soda process can be described by the following equations:

##STR00001##

[0072] Combined reference is made to FIGS. 3 and 4, which are schematic flowcharts of a carbon-calcium cycle process for the ammonia-soda industry according to the present invention. This process enables integrated utilization of the calcium chloride-containing liquid waste resulting from the ammonia evaporation in the ammonia-soda industry and flue gas CO.sub.2. Specifically, it includes the steps as follows:

[0073] Step I: liquid waste pre-treatment. The liquid waste from the ammonia evaporation in the soda production process based on the ammonia-soda process is pre-treated for removal of impurities therefrom, giving CaCl.sub.2)-containing liquid waste. The removed impurities include insoluble solid residues and impurity ions other than calcium, sodium and chlorine ions. CaCl.sub.2) is present at a concentration of 0.5-3 mol/L in the liquid waste from the ammonia evaporation.

[0074] Step II: flue gas CO.sub.2 pre-treatment. After being desulfurized and denitrified, the flue gas CO.sub.2 is compressed and then introduced into a solution of an auxiliary agent. Alternatively, the desulfurized and denitrified flue gas CO.sub.2 may be directly introduced into the auxiliary agent without being compressed. The flue gas CO.sub.2 may be compressed to a pressure of up to 0.8 MPa. The auxiliary agent is a water-soluble amine.

[0075] Step III: mineralization reaction. The CaCl.sub.2)-containg liquid waste is introduced into the solution of the auxiliary agent, in which the flue gas CO.sub.2 has been absorbed, causing a mineralization reaction. Micro- or nano-sized calcium carbonate is obtained from crystallization. The CaCl.sub.2)-containg liquid waste is added at a volume ratio of 1:(0.5-3) to the solution of the auxiliary agent.

[0076] Step IV: As a result of solid-liquid separation being conducted after the mineralization reaction, calcium carbonate is obtained as a solid, as well as a solution of a hydrochloride of the auxiliary agent. After being washed and dried, the solid calcium carbonate is fed to a limestone calcination section in the soda ash production line based on the ammonia-soda process, where it is calcined in a lime kiln, producing CaO and CO.sub.2, which are then used respectively for ammonia evaporation and carbonation of ammoniated brine for soda production after slaking in the soda ash production process based on the ammonia-soda process.

[0077] Step V: The solution of the hydrochloride of the auxiliary agent resulting from solid-liquid separation is fed to an auxiliary agent regeneration section, where the regenerated auxiliary agent is recycled and dilute hydrochloric acid is obtained as a by-product. The chlorine-containing product can be used as resources in another workshop in the ammonia soda plant or sold. The auxiliary agent is regenerated through bipolar membrane electrodialysis.

[0078] Step VI: The above steps are repeated on the liquid waste resulting from the ammonia evaporation conducted after the addition of milk of lime. This is coupled with flue gas CO.sub.2 mineralization and crystallization, enabling carbon-calcium cycling in the ammonia-soda industry.

[0079] It is to be noted that the above-described carbon-calcium cycle process for the soda production industry based on the ammonia-soda process according to the present invention enables recycling of calcium resources and carbon resources. The numbering of steps I to VI above does not represent an absolute sequential ordering. That is, these steps are not limited to being performed one before or after another in time. For the coupled carbon-calcium cycle process for the soda production industry based on the ammonia-soda process, the mineralization reaction section, the auxiliary agent regeneration section and the carbon-calcium cycling for the mineralization reaction are important.

[0080] In the coupled carbon-calcium cycle process for the soda production industry based on the ammonia-soda process, soda production based on the ammonia-soda process can be described by the following overall equation:

##STR00002##

[0081] The ammonia-soda industry uses a NaCl solution and flue gas CO.sub.2 as raw materials to produce industrial soda ash as a product and dilute hydrochloric acid as a by-product. Subjecting the liquid waste from the ammonia evaporation to mineralization and crystallization and circulating it back to the limestone calcination section of the ammonia-soda process avoids external purchase of limestone used in the ammonia-soda industry and discharge or backfilling of the calcium chloride-containing liquid waste and realizes recycling of calcium resources. At the same time, flue gas from a thermal power plant can be utilized in an integrated manner to produce industrial soda ash and realize recycling of carbon resources. The entire process is free of solid or liquid waste discharge, achieving integrated all-atom utilization.

Example 2-4 Mineralization Processes for Producing Calcium Carbonate of High Value with Controlled Morphology and Particle Size

Example 2

[0082] In a jacketed reactor, 100 ml of a 1 mol/L piperazine (PZ) solution was added. Stirring was conducted at a controlled speed of 200 r/min, with the reaction temperature being controlled at 25? C. In the reaction system, 15% CO.sub.2 gas was introduced at a controlled input rate of 500 ml/min. After the reaction ran for 1 h, the solution of the water-soluble amine was saturated with CO.sub.2, and the CO.sub.2 supply was halted. 50 mL of liquid waste containing CaCl.sub.2) at 1 mol/L was added dropwise into the jacketed reactor at a rate of 1.667 ml/min. The stirring speed was maintained at 200 r/min, and the reaction temperature was kept at 25? C. The reaction was stop after 0.5 h. Filtration was carried out, and the resulting filter cake was washed several times with deionized water and ethanol and then dried in an oven at 110? C., obtaining calcium carbonate as a product, denoted as Example 2-1. As calculated based on the results of an ICP test, 98.87% of calcium chloride was converted by the first-order reaction, and calcium carbonate was obtained at a yield of 95.59%. According to X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis, as shown in FIGS. 5 to 6, the calcium carbonate product was obtained as cubic calcite with an average particle size of 16.65 ?m.

[0083] Examples 2-2 to 2-5 were each produced in a similar way except for differences in process conditions and reaction results as summarized in the table below. Examples 2-2 to 2-5 showed the same XRD and SEM results as Example 2-1. In the table, A stands for absorption followed by mineralization, a mode in which the CO.sub.2 gas was first introduced into the solution of the water-soluble amine and then mixed with the CaCl.sub.2)-containing liquid waste; B stands for simultaneous absorption and mineralization, a mode in which the solution of the water-soluble amine was mixed with the CaCl.sub.2)-containing liquid waste and the CO.sub.2 gas was then introduced; c (dropwise) stands for dropwise addition of the CaCl.sub.2)-containing liquid waste to the solution of the water-soluble amine; d (pouring) stands for direct pouring of the CaCl.sub.2)-containing liquid waste into the solution of the water-soluble amine; and e (Calcium/Amine Ratio) stands for a molar ratio of calcium chloride to the water-soluble amine, which were raw materials for the reaction. The same denotations apply to the following description.

[0084] According to the results of Examples 2-1 to 2-5, when the water-soluble amine is selected from diamine compounds, calcium carbonate is obtained as a product of mineralization in the form of calcite with controlled morphology, without being limited by any other process conditions.

TABLE-US-00001 Calcium/Amine Average Water-Soluble Addition Mixing of Ratio .sup.e Reaction Mineralization Crystal Particle Example Amine of CO.sub.2 Solution (n:n) Temperature Percentage Form Size 2-1 piperazine A dropwise .sup.c 1:2 25? C. 95.59% calcite 16.65 ?m 2-2 piperazine A pouring .sup.d 1:1 40? C. 80.34% 7.44 ?m 2-3 piperazine B pouring 1:2 70? C. 96.47% 9.56 ?m 2-4 ethylenediamine A dropwise 1:4 25? C. 94.26% 12.53 ?m 2-5 Tetramethyleth- A dropwise 1:2 40? C. 92.43% 15.37 ?m ylenediamine

Example 3

[0085] In a jacketed reactor, 100 ml of a 1 mol/L sodium glycinate (GlyNa) solution was added. Stirring was conducted at a controlled speed of 200 r/min, with the reaction temperature being controlled at 25? C. In the reaction system, 15% CO.sub.2 gas was introduced at a controlled input rate of 500 ml/min. After the reaction ran for 1 h, the solution of the water-soluble amine was saturated with CO.sub.2, and the CO.sub.2 supply was halted. 50 mL of liquid waste containing CaCl.sub.2) at 1 mol/L was added dropwise into the jacketed reactor at a 25 rate of 1.667 ml/min. The stirring speed was maintained at 200 r/min, and the reaction temperature was kept at 25? C. The reaction was terminated after 0.5 h. Filtration was carried out, and the resulting filter cake was washed several times with deionized water and ethanol and then dried in an oven at 110? C., obtaining calcium carbonate as a product, denoted as Example 3-1. As calculated based on the results of an ICP test, 98.30% of calcium chloride was converted by the first-order reaction, and calcium carbonate was obtained at a yield of 96.48%. According to XRD and SEM analysis, as shown in FIGS. 7 to 8, the calcium carbonate product was obtained as spherical vaterite with an average particle size of 34.6 ?m.

[0086] Examples 3-2 to 3-5 were each produced in a similar way except for differences in process conditions and reaction results as summarized in the table below. Examples 3-2 to 3-5 showed the same XRD and SEM results as Example 3-1.

[0087] According to the results of Examples 3-1 to 3-5, when the water-soluble amine is selected from amino acid salt compounds and basic amino acid compounds, calcium carbonate is obtained as a product of mineralization in the form of vaterite with controlled morphology, without being limited by any other process conditions.

TABLE-US-00002 Calcium/Amine Average Water-Soluble Addition Mixing of Ratio Reaction Mineralization Crystal Particle Example Amine of CO.sub.2 Solution (n:n) Temperature Percentage Form Size 3-1 sodium A dropwise 1:2 25? C. 96.48% vaterite 34.6 ?m glycinate 3-2 sodium A pouring 1:2 40? C. 97.5% 12.8 ?m glycinate 3-3 sodium B pouring 1:4 70? C. 98.4% 7.5 ?m glycinate 3-4 arginine A dropwise 1:2 40? C. 97.7% 19.4 ?m 3-5 arginine A dropwise 1:1 25? C. 90.2% 13.7 ?m

Example 4

[0088] In a jacketed reactor, 100 ml of a 1 mol/L monoethanolamine (MEA) solution was added. Stirring was conducted at a controlled speed of 200 r/min, with the reaction temperature being controlled at 25? C. In the reaction system, 15% CO.sub.2 gas was introduced at a controlled input rate of 500 ml/min. After the reaction ran for 1 h, the solution of the water-soluble amine was saturated with CO.sub.2, and the CO.sub.2 supply was halted. 50 mL of liquid waste containing CaCl.sub.2) at 1 mol/L was added dropwise into the jacketed reactor at a rate of 1.667 ml/min. The stirring speed was maintained at 200 r/min, and the reaction temperature was kept at 25? C. The reaction was terminated after 0.5 h. Filtration was carried out, and the resulting filter cake was washed several times with deionized water and ethanol and then dried in an oven at 110? C., obtaining calcium carbonate as a product, denoted as Example 4-1. As calculated based on the results of an ICP test, 99.18% of calcium chloride was converted by the first-order reaction, and calcium carbonate was obtained at a yield of 97.52%. According to XRD and SEM analysis, as shown in FIGS. 9 to 10, the calcium carbonate product was obtained as spherical vaterite with an average particle size of 7.6 ?m.

[0089] Examples 4-2 to 4-16 were each produced in a similar way using a water-soluble alkanolamine, except for differences in process conditions and reaction results as summarized in the table below.

[0090] According the results of Examples 4-1 to 4-4, XRD and SEM analysis of the product prepared according to Example 4-2 is as shown in FIGS. 11 to 12, Examples 4-3 to 4-4 show the same XRD and SEM results as Example 4-2. When a molar ratio of calcium chloride to the water-soluble amine is greater than 1:2, i.e., when calcium chloride is added in excess, calcium carbonate will be obtained as a product in the form of calcite with controlled morphology.

[0091] According the results of Examples 4-5 to 4-11, when the molar ratio of calcium chloride to the water-soluble amine is not greater than 1:2, i.e., when the water-soluble amine is added in stoichiometric equivalence or excess, if CO.sub.2 absorption occurs simultaneously with the mineralization reaction, i.e., if the introduced CO.sub.2 experiences the mineralization reaction in a mixed solution of the solution of the water-soluble amine and the calcium chloride solution, then calcium carbonate will be obtained as a product existing in a multi-crystalline form. For the results of Examples 4-5 to 4-6, reference can be made to FIGS. 13 to 14, which show XRD and SEM analysis of the product prepared according to Example 4-5.

[0092] When CO.sub.2 is absorbed and then mineralized, i.e., when CO.sub.2 is introduced into the solution of the water-soluble amine and then mixed with the calcium chloride-containing liquid waste, the calcium carbonate product will be obtained as vaterite with controlled morphology if the mineralization reaction is carried out at a low temperature, or as calcite with controlled morphology if the mineralization reaction is carried out at a high temperature. According to the results of Examples 4-7 to 4-11, the morphology of Examples 4-7 to 4-8 is similar to that of Example 4-1, and all the products were obtained in the form of vaterite. Moreover, the morphology of Examples 4-9 to 4-10 is similar to that of Example 4-2, and all the products were obtained in the form of calcite. Example 4-11 was obtained in a multi-crystalline form.

[0093] Examples 4-12 to 4-16 differ from Example 4-1 in that the solution of the water-soluble amine and the CaCl.sub.2)-containing liquid waste were added in opposite orders. In the table, a also stands for absorption followed by mineralization, but this refers to a mode in which, after the CaCl.sub.2)-containing liquid waste was added to the jacketed reactor, the CO.sub.2 gas was introduced into the reaction system until saturation was reached, and the solution of the water-soluble amine was then added to the jacketed reactor to cause the mineralization reaction. Moreover, b also stands for simultaneous absorption and mineralization, but this refers to a mode in which, the solution of the water-soluble amine was added to and mixed with the CaCl.sub.2)-containing liquid waste and the CO.sub.2 gas was then introduced. All the other operation regulation parameters were the same as Example 4-1.

[0094] According to the results of Examples 4-12 to 4-16, when the materials are added in such an order that, during the addition of the solution of the water-soluble amine to the calcium chloride solution, CO.sub.2 absorption is followed by a mineralization reaction, i.e., CO.sub.2 is introduced into the calcium chloride-containing liquid waste and then mixed with the solution of the water-soluble amine, calcium carbonate will be obtained as a product in the form of calcite with controlled morphology, without being limited by any other process conditions. According to the results of Examples 4-12 to 4-14, the morphology of the products is similar to that of Example 4-2. When the materials are added in such an order that CO.sub.2 absorption occurs at the same time as a mineralization reaction, i.e., CO.sub.2 is introduced into a mixed solution of the solution of the water-soluble amine and the calcium chloride solution to cause a mineralization reaction, calcium carbonate will be obtained as a product with heterogeneous morphology in a multi-crystalline form. For this, reference can be made to the results of Examples 4-15 to 4-16.

TABLE-US-00003 Calcium/Amine Average Water-Soluble Addition Mixing of Ratio Reaction Mineralization Crystal Particle Example Amine of CO.sub.2 Solution (n:n) Temperature Percentage Form Size 4-1 MEA A dropwise 1:2 25? C. 97.52% vaterite 12.6 ?m 4-2 MEA A dropwise 1:1 25? C. 83.66% calcite 10.3 ?m 4-3 AMP A dropwise 1:0.5 65? C. 70.52% calcite 11.2 ?m 4-4 MDEA B dropwise 1:1 25? C. 81.46% calcite 13.8 ?m 4-5 MEA B dropwise 1:4 25? C. 99.23% multi-crystalline 14.7 ?m 4-6 TEA B dropwise 1:4 25? C. 99.33% multi-crystalline 18.9 ?m 4-7 MEA A dropwise 1:4 25? C. 98.79% vaterite 20.8 ?m 4-8 TEA A pouring 1:2 25? C. 97.44% vaterite 7.9 ?m 4-9 TEA A pouring 1:4 65? C. 98.59% calcite 6.3 ?m 4-10 MEA A dropwise 1:2 65? C. 97.25% calcite 13.4 ?m 4-11 MEA A dropwise 1:4 45? C. 99.53% multi-crystalline 15.5 ?m 4-12 MEA a dropwise 1:2 25? C. 98.62% calcite 18.2 ?m 4-13 DEA a dropwise 1:2 65? C. 97.96% calcite 16.9 ?m 4-14 MDEA a pouring 1:4 25? C. 99.46% calcite 10.7 ?m 4-15 TEA b dropwise 1:2 25? C. 97.88% multi-crystalline 23.4 ?m 4-16 MEA b pouring 1:2 25? C. 97.69% multi-crystalline s 8.9 ?m

Example 5 Processes for Amine Regeneration Through Bipolar Membrane Electrodialysis

[0095] Filtrates resulting from filtration conducted in Examples 2-1, 3-1,4-1, 4-3,4-4, 4-8 (which were solutions of hydrochlorides of piperazine, sodium glycinate, monoethanolamine, 2-amino-2-methyl-1-propanol, N-methyl diethanolamine and triethanolamine) were treated by bipolar membrane electrodialysis for recovery of the water-soluble amines and preparation of dilute hydrochloric acid.

[0096] Each filtrate was treated by bipolar membrane electrodialysis, which was conducted with a salt-acid two-chamber structure, including: a salt chamber initially containing 300 ml of a solution of the filtrate; an acid chamber initially containing 300 ml of a 0.03 mol/L dilute hydrochloric acid solution; and an electrode solution chamber containing 300 ml of a 0.3 mol/L Na.sub.2SO.sub.4 solution. The treatment was carried out at a constant current of 0.5 A provided by a DC power supply and at a flow rate of 500 ml/min in each chamber. The regenerated water-soluble amine and dilute hydrochloric acid were obtained in the salt and acid chambers, respectively, 60-100 min after the treatment began.

[0097] All the water-soluble amines can be regenerated from their hydrochlorides through bipolar membrane electrodialysis in an excellent manner. All the water-soluble amines, except for piperazine, can be regenerated at a rate of 90% or higher. FIG. 15 shows mobility of Cl.sup.? in the acid chamber as a result of treating the hydrochlorides of the various water-soluble amines by bipolar membrane electrodialysis. FIG. 16 shows residual rates of Cl.sup.? in the salt chamber as a result of treating the hydrochlorides of the various water-soluble amines by bipolar membrane electrodialysis. FIG. 17 shows amine regeneration rate in the salt chamber as a result of treating the hydrochlorides of the various water-soluble amines by bipolar membrane electrodialysis.

[0098] The above-discussed method for integrated utilization of calcium chloride-containing liquid waste and flue gas CO.sub.2 through mineralization with a water-soluble amine and regeneration of the amine by bipolar membrane electrodialysis is applicable to solutions of various water-soluble amines. The mineralization process is easy to implement and can provide excellent mineralization performance, and the resulting calcium carbonate can be circulated to a carbon-calcium cycling like that in a soda production process based on the ammonia-soda process. In addition, the process can be regulated to produce micro- or nano-sized calcium carbonate of high value with controlled morphology and particle size for sale or use in another workshop in the factory. Various water-soluble amines can be regenerated by bipolar membrane electrodialysis from their hydrochlorides in filtrates from the process, and dilute hydrochloric acid can be obtained at the same time. Various water-soluble amines can be regenerated from their hydrochlorides in an excellent manner. This method enables integrated utilization of calcium chloride-containing liquid waste and flue gas CO.sub.2 and can produce a calcium carbonate product of high value and dilute hydrochloric acid. It is significantly advantageous over conventional processes and provides a novel perspective and approach to calcium chloride disposal and carbon emission reduction. The process is highly feasible and shows a promising prospect of application.

[0099] The detailed description of the present application set forth herein is intended to enable those familiar with the art to understand the disclosure of the present application and to practice the application, and is not meant to limit the scope thereof in any sense. Any and all equivalent variations or modifications made within the substantive spirit of the application are all intended to be embraced within the scope thereof.