Carbon-calcium combined cycle process for ammonia-soda process of alkali production industry

Abstract

The application provides a carbon-calcium combined cycle process in an ammonia-soda method alkali industry, which takes ammonia evaporation waste liquid of an alkali plant and flue gas of a power plant for capturing CO2 or other CO2 tail gas as raw materials, realizes mineralization reaction crystallization through an auxiliary to obtain micron or nanometer calcium carbonate, and uses the calcium carbonate to replace limestone in an alkali production process for calcination, provides CO2 and lime milk for the alkali production process, and realizes recycling of carbon resources and calcium resources. Through mineralization crystallization of the ammonia evaporation waste liquid and recycling back to the limestone calcination section for alkali production, the ammonia-soda method process avoids purchasing of limestone and discarding or backfilling of calcium chloride waste liquid; meanwhile, the flue gas of a thermal power plant is comprehensively utilized for preparation of industrial soda ash and calcium carbonate. The whole process realizes resource utilization of the calcium chloride waste liquid and the purpose of CO2 emission reduction, realizes waste residue and waste liquid emission-free of the ammonia-soda industry, and realizes full-atom comprehensive utilization.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of industrial waste resource utilization, and in particular relates to a process for comprehensive utilization of ammonia-alkali plant waste liquid and power plant flue gas to capture CO2 or other CO2 tail gas, realizing carbon-calcium resource joint recycling in the ammonia-alkali method for alkali production industry. BACKGROUND

[0002] The ammonia-alkali method for alkali production is one of the most important soda production methods in China, and its annual output accounts for about half of the total output, with the advantages of good investment benefit and high product purity. However, for every ton of soda produced by the ammonia-alkali method, about 11 m 3 of ammonia distillation waste liquid and 200 kg of solid waste residue are produced as by-products. The basic composition of the ammonia distillation waste liquid is about 95-105 g / L of calcium chloride solution and about 35-45 g / L of unreacted sodium chloride solution.

[0003] CN112850770A discloses a resource utilization method for using ammonia-alkali waste liquid for sodium sulfate type salt mine well injection brine production. Ammonia-alkali waste liquid is injected into the underground of sodium sulfate type salt mine instead of fresh water. Calcium chloride in the ammonia-alkali waste liquid reacts with sodium sulfate in the salt cavity to generate calcium sulfate dihydrate precipitate and sodium chloride brine. The calcium sulfate fills the salt cavity underground, and the brine is exploited and utilized, which not only reduces the sodium sulfate content in the brine, but also recovers NaCl in the ammonia-alkali waste liquid, realizing the resource utilization of the ammonia-alkali waste liquid. However, the calcium sulfate precipitate is at the bottom of the salt cavity, which covers the bottom mineral deposit and affects the exploitation of the bottom mineral layer. Moreover, with the increase of the amount of ammonia-alkali waste liquid injected into the well, the sodium sulfate in the brine well cavity will be gradually consumed, which is not a long-term solution. In addition, the salt gypsum produced underground cannot be changed into a product due to technical problems, resulting in a large waste of resources. At present, the treatment of calcium chloride waste liquid produced by the ammonia-alkali method is mainly by direct discharge and well injection, and with the continuous expansion of the soda production scale, the amount of calcium chloride waste liquid is increasing, and its treatment has become an industry common technical problem that needs to be solved in the soda industry.

[0004] At the same time, with the current global climate change, CO2 emission reduction has become urgent. The soda industry is one of the industries that are seriously troubled by carbon emission reduction, because it not only involves carbon emission caused by power generation and heat generation, but also involves carbon emission in the manufacturing process. At present, there are still few studies on the transformation of the soda industry to carbon net zero emission. Carbon emission caused by power plants accounts for 43% of the total global carbon emission. Many ammonia-alkali plants have their own thermal power plants, and the CO2 tail gas of the thermal power plant is directly discharged after desulfurization and denitrification, which aggravates the greenhouse effect. If the ammonia distillation waste liquid of the ammonia-alkali plant and the flue gas CO2 of the thermal power plant can be comprehensively utilized, it will have social, economic and environmental benefits. SUMMARY

[0005] The present application aims at overcoming the deficiencies in the prior art, and provides a carbon-calcium resource recycling process in the ammonia-soda alkali industry, which comprehensively utilizes the ammonia evaporation calcium chloride waste liquid of an ammonia-soda plant and the CO2 tail gas of a thermal power plant, realizes the resource utilization of the calcium chloride waste liquid and the purpose of CO2 emission reduction, realizes the recycling utilization of the carbon resource and the calcium resource of the ammonia-soda plant, and obtains calcium carbonate products and chlorination resource products. According to the calculation, the CO2 discharged by the ammonia-soda plant and the thermal power plant can fully meet the needs of the entire soda production, and the CO2 discharged by the lime kiln and the carbonization tower can fully meet the needs of the soda production and the needs of the treatment and mineralization of the calcium chloride waste liquid into calcium carbonate. The recycling utilization of the carbon-calcium resource avoids the purchase of limestone in the ammonia-soda industry, and since the prepared calcium carbonate does not contain many impurities such as Fe in the limestone mine, the calcium carbonate is more beneficial to calcination than the limestone, and the lime kiln is not easy to form a tumor.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A carbon-calcium recycling process in the ammonia-soda alkali industry, the process method is: taking the ammonia evaporation waste liquid and the CO2 tail gas as raw materials, adding an additive to carry out mineralization reaction and crystallization to obtain calcium carbonate, the calcium carbonate is used to replace limestone in the alkali production process for calcination, and CO2 and lime milk are provided for the alkali production process, realizing the recycling utilization of calcium resource and CO2.

[0008] The calcium recycling route of the present application is: the limestone in the alkali production process is calcined to produce raw lime, digestion is carried out to obtain lime milk, ammonia evaporation is carried out to obtain ammonia evaporation waste liquid, the ammonia evaporation waste liquid is mineralized with CO2 tail gas to obtain micron or nanometer calcium carbonate, the calcium carbonate replaces limestone for calcination, the above process is repeated, and the calcium recycling of the ammonia-soda alkali industry is realized.

[0009] The carbon recycling route of the present application is: the thermal power plant, the lime kiln and the carbonization tower can provide CO2 for the entire ammonia-soda process, the CO2 tail gas is mineralized with the ammonia evaporation waste liquid to obtain calcium carbonate, the calcium carbonate is calcined to provide slaked lime and CO2 for the alkali production, and finally sodium carbonate products and calcium carbonate are obtained, the sodium carbonate products are sold, and the calcium carbonate is used to replace the purchased limestone for recycling utilization.

[0010] The present application is further provided that the additive is an alkaline amine, and the alkaline amine is selected from water-soluble amine or oil-soluble amine.

[0011] The present application is further provided that the water-soluble amine is selected from one or more of alcohol amine compounds, amino acid salt compounds, alkaline amino acid compounds, diamine compounds, polyamine compounds and aromatic amine compounds, and the oil-soluble amine is selected from one or more of long-chain tertiary amine compounds.

[0012] The application is further configured that the ammonia distillation waste liquid is crystallized into calcium carbonate after being pretreated and impurity-removed and being mineralized with the CO2 tail gas, or is directly mineralized with the CO2 tail gas to obtain calcium carbonate.

[0013] The application is further configured that the CO2 tail gas is from a flue gas of a thermal power plant, a kiln gas of a lime kiln and / or a tail gas of a carbonization tower, i.e., the CO2 tail gas is from one or more of the flue gas of the thermal power plant, the kiln gas of the lime kiln and the tail gas of the carbonization tower.

[0014] The application is further configured that the concentration of CO2 in the CO2 tail gas is 2% to 45%.

[0015] The application is further configured that the CO2 tail gas is compressed after being desulfurized and denitrified, or is directly introduced into the auxiliary solution and then mixed with the ammonia distillation waste liquid to occur the mineralization reaction, or is introduced into the ammonia distillation waste liquid and then mixed with the auxiliary solution to occur the mineralization reaction, or is introduced into the mixed solution of the auxiliary solution and the ammonia distillation waste liquid to occur the mineralization reaction. The pressure of the compressed CO2 tail gas is up to 0.8 MPa.

[0016] The application is further configured that the volume ratio of the ammonia distillation waste liquid to the auxiliary solution is 1:(0.5-3).

[0017] The application is further configured that the carbon recycling route of the application further comprises that the CO2 tail gas is concentrated after being desulfurized and denitrified, and is directly used for preparing soda in the carbonation of ammonia brine in an alkali preparation process, or / and is used for treating the calcium chloride ammonia alkali waste liquid which has not been treated before to mineralize and prepare calcium carbonate products, so as to fully utilize the flue gas CO2 and help the carbon emission reduction of the ammonia alkali plant.

[0018] The application is further configured that the solid-liquid separation is performed after the mineralization reaction is completed, the liquid-phase auxiliary hydrochloride solution is recycled by using the auxiliary regeneration, and a by-product HCl gas or a dilute hydrochloric acid and other chlorine resource products are produced.

[0019] The application is further configured that the method of the auxiliary regeneration is a chemical desorption, a thermal desorption or a bipolar membrane electrodialysis method.

[0020] Compared with the prior art, the application has the beneficial effects that:

[0021] The carbon-calcium combined cycle process of the soda production industry by the ammonia-soda method makes the raw material of the soda production process as a whole be NaCl solution and CO2 tail gas of a thermal power plant, and industrial soda product and by-product HCl gas or dilute hydrochloric acid are prepared. By mineralization crystallization of the ammonia evaporation waste liquid and recycling back to the limestone calcination section for soda production, purchase of limestone in the ammonia soda industry and disposal or backfill of calcium chloride waste liquid are avoided, and recycling of calcium resources is realized; meanwhile, flue gas of the thermal power plant is comprehensively utilized for preparation of industrial soda and recycling of carbon resources, and the whole process realizes no waste residue and waste liquid discharge and full atomic comprehensive utilization. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Process flow diagram for preparation of soda by the ammonia-soda method;

[0023] Figure 2 Process flow diagram for the carbon-calcium combined cycle process of the soda production industry by the ammonia-soda method;

[0024] Figure 3 Schematic diagram of the carbon-calcium combined cycle process of the soda production industry by the ammonia-soda method. DETAILED DESCRIPTION

[0025] The technical solutions of the present application will be described below in specific embodiments. It should be understood that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0026] According to Figure 1 The process flow diagram of the soda production process by the ammonia-soda method is shown in the figure, NH3 is introduced into saturated brine to absorb ammonia to obtain ammonia brine, and then CO2 is introduced to perform carbonation reaction and crystallization to prepare NaHCO3, and after filtration separation, the NaHCO3 is calcined to obtain soda product, CO2 is recycled, the NH4Cl filtrate is evaporated with lime milk to recover NH3, and the remaining CaCl2 evaporation waste liquid is directly disposed. The lime milk is obtained by calcination and digestion of purchased limestone, and the obtained CO2 is also recycled. The reaction equations of each section in the preparation of soda by the ammonia-soda method are as follows:

[0027] NaCl + NH3 + H2O + CO2 → NH4Cl + NaHCO3↓

[0028] 2NaHCO3 → Na2CO3 + H2O + CO2↑

[0029] 2NH4Cl + Ca(OH)2 → 2NH3↑ + CaCl2 + 2H2O

[0030] CaCO3 → CaO + CO2↑

[0031] CaO + H2O → Ca(OH)2

[0032] combined Figure 2 and Figure 3 As shown in the figure, the process flow diagram of the carbon calcium cycle of the ammonia alkali industry of the present application comprehensively utilizes the calcium chloride waste liquor and CO2 tail gas of the ammonia alkali industry, and specifically includes the following steps:

[0033] Step one, waste liquor pretreatment: the ammonia distillation waste liquor of the ammonia alkali method is pretreated to remove impurities to obtain CaCl2 waste liquor, the removal of impurities is to remove insoluble solid residue and other impurity ions except calcium, sodium and chlorine ions, and the concentration of CaCl2 in the ammonia distillation waste liquor is 0.5-3 mol / L.

[0034] Step two, CO2 tail gas pretreatment: the CO2 tail gas is compressed after desulfurization and denitrification and then introduced into the auxiliary solution, or the CO2 tail gas is directly introduced into the auxiliary solution after desulfurization and denitrification without compression treatment; the compressed gas pressure after compression of the CO2 tail gas can be up to 0.8 MPa.

[0035] Further, the auxiliary agent is an alkaline amine, and the alkaline amine is selected from one or more of water-soluble amines or oil-soluble amines, the water-soluble amines are selected from one or more of alcohol amine compounds, amino acid salt compounds, alkaline amino acid compounds, diamine compounds, polyamine compounds and aromatic amine compounds, and specifically selected from one or more of ethanolamine, triethanolamine, 2-amino-2-methyl-1-propanol, N-methyl diethanolamine, glycine sodium, arginine, piperazine, triethylenetetramine, pyridine and the like; the oil-soluble amine includes tertiary amine compounds, and specifically selected from one or more of trioctylamine, trihexylamine and other long-chain tertiary amines.

[0036] Step three, mineralization reaction: the CaCl2 waste liquor is introduced into the auxiliary solution for absorbing the CO2 tail gas to obtain micron or nanometer calcium carbonate through mineralization reaction; the volume ratio of the CaCl2 waste liquor to the auxiliary solution is 1:(0.5-3); the mineralization reaction equation is as follows, and the auxiliary agent is represented by X:

[0037] CaCl2 + 2X + H2O + CO2 → 2XHCl + CaCO3↓

[0038] Step four, solid-liquid separation of the material after the mineralization reaction to obtain calcium carbonate solid and auxiliary hydrochloride solution; the calcium carbonate solid is washed and dried and then sent to the limestone calcination section in the soda ash production process of the ammonia alkali method for calcination in a lime kiln, and the products CaO and CO2 are used for ammonia distillation after digestion and carbonation of ammonia brine for soda ash production in the soda ash production process of the ammonia alkali method, respectively.

[0039] Step five, the assistant hydrochloride solution after solid-liquid separation is sent to the assistant regeneration section, and regenerated assistant is recycled and used, and HCl gas or dilute hydrochloric acid is by-produced, and the chloro resource product is used in other workshops of the ammonia alkali plant or sold; the equation of the assistant regeneration is as follows:

[0040] XHCl→X+HCl

[0041] Further, the assistant regeneration method is chemical desorption, thermal desorption or bipolar membrane electrodialysis.

[0042] The chemical desorption is that a basic substance is added in the assistant hydrochloride solution, and a strong base is used to prepare a weak base, so that the assistant is regenerated.

[0043] The thermal desorption is that the assistant hydrochloride solution is thermally decomposed into the assistant and hydrogen chloride at a reaction temperature of 100-300 DEG C, and the thermal desorption is carried out in a reduced pressure rectifying tower, an atmospheric pressure rectifying tower, a pressurized rectifying tower, a rotary evaporation device or a molecular distillation device.

[0044] The bipolar membrane electrodialysis is that the assistant hydrochloride solution is subjected to the action of a positive voltage in a bipolar membrane electrodialysis device, and the cations and anions are directionally moved, the protonated assistant ions are left in a salt chamber or migrated to a base chamber and combined with OH- ions hydrolyzed from a bipolar membrane to be regenerated into the assistant; the chloride ions migrate to an acid chamber and combine with H + to be HCl, so that the regenerated assistant and dilute hydrochloric acid solution are obtained.

[0045] The bipolar membrane electrodialysis device adopts a salt chamber-acid chamber two-chamber structure or a salt chamber-acid chamber-base chamber three-chamber structure.

[0046] Step six, the ammonia evaporation waste liquid obtained after the lime milk is evaporated is subjected to the above steps, and is crystallized by mineralization reaction with the CO2 tail gas, so that the carbon-calcium circulation of the ammonia alkali industry is realized.

[0047] It should be noted that, since the above-mentioned carbon-calcium circulation process of the ammonia alkali method for producing alkali industry constitutes the recycling of calcium resources and carbon resources, the above-mentioned steps one to step six do not represent an absolute sequence, that is, the above-mentioned steps are not limited in time. In the above-mentioned carbon-calcium combined circulation process of the ammonia alkali method for producing alkali industry, the focus is on the mineralization reaction section, the assistant regeneration section and the carbon-calcium circulation process around the mineralization reaction.

[0048] Through the above-mentioned carbon-calcium combined circulation process of the ammonia alkali method for producing alkali industry, the total equation of the ammonia alkali method for producing alkali is as follows:

[0049] 2NaCl+H2O+CO2→Na2CO3+2HCl

[0050] The raw material of the ammonia alkali industry is a NaCl solution and a CO2 tail gas, and an industrial soda product and a byproduct HCl gas or dilute hydrochloric acid are prepared. By mineralizing and crystallizing the ammonia distillation waste liquid and recycling it back to the limestone calcination section of the ammonia alkali method, the limestone purchase and the calcium chloride waste liquid discharge or backfill in the ammonia alkali industry are avoided, the calcium resource recycling is realized, the flue gas of a thermal power plant is comprehensively utilized for preparing the industrial soda, the carbon resource recycling is realized, the whole process realizes no waste residue and waste liquid discharge, and the full atom comprehensive utilization is realized.

[0051] As an embodiment of the present application, the ammonia distillation waste liquid is mineralized with the CO2 tail gas after being pretreated and impurity-removed to obtain calcium carbonate; or is directly mineralized with the CO2 tail gas to obtain calcium carbonate.

[0052] As an embodiment of the present application, the CO2 tail gas is mineralized with the ammonia distillation waste liquid after being compressed and treated after desulfurization and denitrification; or is directly mineralized with the ammonia distillation waste liquid after being desulfurized and denitrified without compression treatment.

[0053] As an embodiment of the present application, the CO2 tail gas is mineralized after being introduced into an auxiliary solution, or is introduced into the ammonia distillation waste liquid, or is introduced after the ammonia distillation waste liquid is mixed with the auxiliary solution, and then the mineralization reaction is carried out.

[0054] As an embodiment of the present application, the flue gas of a thermal power plant is compressed after being desulfurized and denitrified, and is used for mineralizing the ammonia distillation waste liquid to obtain calcium carbonate, instead of limestone calcination; since the discharge amount of the CO2 tail gas of the ammonia alkali plant is much larger than the demand of the ammonia distillation waste liquid mineralization, in order to fully utilize the flue gas CO2, the CO2 tail gas can be further concentrated after being desulfurized and denitrified, and is directly used for preparing soda by carbonating the ammonia salt water, or can be further used for treating the calcium chloride ammonia alkali waste liquid left untreated before, and mineralization is carried out to obtain a high-value nano calcium carbonate product for sale, and to help the carbon emission reduction of the ammonia alkali plant.

[0055] Example 1

[0056] An ammonia alkali plant with an annual output of 400,000 tons of soda is added with a carbon-calcium recycling process on the basis of the original process, and the soda is prepared by the above-mentioned ammonia alkali method of the present application. The water quality analysis of the ammonia distillation waste liquid of the ammonia alkali plant is as follows, and the composition concentration is g / L.

[0057] Item Density pH NaCl CaCl2 CaCO3 CaO Mg(OH)2 Results 1.1-1.2 g / m 3 ]] 11.4-11.6 41 110 19 3 6

[0058] The ammonia distillation waste liquid is removed of solid residue to obtain a waste liquid mainly containing calcium chloride, and the CO2 tail gas of a thermal power plant is desulfurized and denitrified, compressed, and introduced into an organic amine solution. The waste liquid and the organic amine solution are mixed at a volume ratio of 1:2 to occur mineralization reaction, and calcium carbonate is prepared. The calcium carbonate solid is washed and dried, and then sent to the original process to replace limestone calcination, and the products CaO and CO2 are used for ammonia distillation after digestion and ammonia brine carbonation to prepare alkali. The ammonia distillation waste liquid obtained after lime milk ammonia distillation is repeated in the above steps, and the CO2 tail gas is mineralized to crystallize, realizing the carbon-calcium cycle of the ammonia-alkali industry. At the same time, the organic amine salt hydrochloride solution after solid-liquid separation is regenerated by heat desorption, and HCl gas is by-produced.

[0059] The above ammonia-alkali plant, through modification of the original process, does not need to purchase limestone and avoids the discharge of ammonia distillation waste liquid, and the annual discharge of ammonia distillation waste liquid is reduced by at least 4 million m 3 The calcium loss in the calcium resource recycling process can be supplemented by mineralization reaction of the existing untreated ammonia distillation waste liquid to prepare calcium carbonate; at the same time, the CO2 tail gas of the thermal power plant of the ammonia-alkali plant is utilized, and the annual carbon dioxide emission is reduced by at least 160,000 tons. The ammonia-alkali plant ammonia distillation calcium chloride waste liquid and the thermal power plant CO2 tail gas are comprehensively utilized, realizing the recycling of carbon resources and calcium resources of the ammonia-alkali plant.

[0060] The present application is described in detail, which aims to enable those skilled in the art to understand the content of the present application and implement it, and cannot limit the protection scope of the present application, and equivalent changes or modifications made according to the spirit and essence of the present application should be covered within the protection scope of the present application. In addition, the present inventors have also carried out tests with other raw materials, process operations, and process conditions described in the specification with reference to the foregoing examples, and all have obtained relatively ideal results.

Claims

1. A carbon-calcium combined cycle process for alkali production using the ammonia-soda process, characterized in that, The process is as follows: using ammonia stripping waste liquid and CO2 tail gas from an ammonia-soda plant as raw materials, calcium carbonate is obtained by mineralization reaction and crystallization through the addition of additives. The calcium carbonate is used to replace limestone in the alkali production process for calcination, providing CO2 and lime milk for the alkali production process, and realizing the recycling of calcium resources and CO2. The adjuvant is a water-soluble amine, which is selected from one or more of the following: alkanolamines, amino acid salts, basic amino acids, diamines, polyamines, and aromatic amines. The ammonia stripping waste liquid is directly reacted with CO2 tail gas for mineralization and crystallization to obtain micron-sized calcium carbonate without pretreatment to remove impurities; the CO2 tail gas comes from one or more of the following: flue gas from thermal power plants, kiln gas from lime kilns, and tail gas from carbonation towers; the concentration of CO2 in the CO2 tail gas is 2% to 45%; after desulfurization and denitrification, the CO2 tail gas is directly reacted with the ammonia stripping waste liquid for mineralization without compression to obtain calcium carbonate products.

2. The carbon-calcium recycling process for alkali production in the ammonia-soda process according to claim 1, characterized in that, The volume ratio of the ammonia stripping waste liquid to the auxiliary agent solution is 1:(0.5-3).

3. The carbon-calcium recycling process for alkali production in the ammonia-soda process according to claim 1, characterized in that, After the mineralization reaction is completed, solid and liquid are separated. The liquid phase auxiliary agent hydrochloride solution is recycled through auxiliary agent regeneration and chlorine resource products are produced as by-products.

4. The carbon-calcium recycling process for alkali production in the ammonia-soda process according to claim 3, characterized in that, The method for regenerating the additive is bipolar membrane electrodialysis.

5. The carbon-calcium recycling process for alkali production in the ammonia-soda process according to claim 4, characterized in that, The chlorine resource recovery product is dilute hydrochloric acid.

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