Integrated comprehensive treatment method and device for waste salt and carbon dioxide in iron and steel industry

Abstract

The invention belongs to the technical field of industrial waste treatment, and particularly relates to an integrated comprehensive treatment method for waste salt and carbon dioxide in the steel industry, which comprises the following steps: collecting industrial waste brine generated by a steel mill, and then carrying out treatment steps of pretreatment and sodium salt extraction to obtain a sodium salt solution with the COD value lower than 10mg / L; introducing the coked residual ammonia water into the treated carbon dioxide flue gas of the hot blast stove to obtain an ammonium bicarbonate-containing solution; introducing the sodium salt solution and the ammonium bicarbonate-containing solution into an electrodialysis module for ion exchange to generate a sodium bicarbonate dilute solution and an ammonium salt dilute solution; concentrating the sodium bicarbonate dilute solution by adopting a reverse osmosis system to obtain a sodium bicarbonate concentrated solution; and carrying out calcium and magnesium removal treatment on the sodium bicarbonate concentrated solution, heating the treated sodium bicarbonate concentrated solution to 190-270 DEG C through a heating tank, and then introducing the carbon dioxide flue gas of the hot blast stove again to obtain a sodium bicarbonate solid product with the purity greater than or equal to 98.5%. Organic combination of carnallite recycling and carbon dioxide adsorption and utilization is realized, and economic benefits and environmental benefits are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial waste treatment, and in particular to an integrated comprehensive treatment method and device for waste salt and carbon dioxide in the steel industry. Background Art

[0002] The steel industry produces waste brine and carbon dioxide during the production process. The composition of waste brine is complex and difficult to handle. It mainly includes inorganic salts, heavy metals, and chemicals used in the desalination process. According to the composition analysis of waste salt in the steel industry, inorganic salts may contain sodium chloride, sodium sulfate, sodium sulfite, sodium nitrate, sodium carbonate, sodium bromide and other salts. Wet desulfurization wastewater or acid washing wastewater generated by the steel sintering process usually contains a large amount of suspended matter, chloride ions, sulfate ions, ammonia nitrogen, as well as a certain amount of calcium and magnesium and a small amount of heavy metal ions. The steel industry is one of the main sources of global carbon dioxide emissions, especially in China, where carbon emissions from the steel industry account for about 15% of the country's total carbon emissions, and China contributes more than 60% of the global steel industry's carbon emissions.

[0003] The treatment and resource utilization of waste salt are of great significance to environmental protection and sustainable development. Current methods for the resource utilization of waste salt include the resource utilization process technology of waste salt produced as a byproduct of molten salt chlorination, the coupled technology and equipment for the resource utilization of waste salt solid waste with elemental level removal of pollutants, a complete set of technologies for the treatment of high-salt wastewater, the reduction of concentrated brine of comprehensive steel wastewater, and a combined method and system for resource utilization treatment. In the above traditional processes, sodium chloride and sodium sulfate are the end points of zero discharge of industrial wastewater. However, these two products are cheap, and even high-purity products do not have good sales and prices. At present, the economic benefits of waste salt treatment in the steel industry are poor.

[0004] Carbon dioxide treatment methods in the steel industry mostly use alkali technology, which is difficult to treat and the technology is immature. Among the current alkali production processes, the circulating alkali production method has a relative advantage in terms of energy consumption and product purity, but a refrigeration device needs to be set up during the production process, the equipment investment is relatively large, the production cost is high, and it cannot improve the key problem of low primary utilization rate of Na+; although the organic amine alkali production method is simpler than the circulating alkali production method in terms of process, and can greatly improve the primary utilization rate of Na+, the process of recovering organic amines is relatively difficult, and the equipment and energy consumption are large, which is not economical; the proton circulating membrane electrolysis (PCME) method combined with electrochemical technology produces soda ash, which has high product purity and avoids the calcination of limestone in the Solvay method, greatly reducing energy consumption, and has obvious energy advantages, but the CO2 absorption reaction rate is low. Summary of the invention

[0005] In view of the above technical problems, a method and device for integrated treatment of waste salt and carbon dioxide in the steel industry are provided to improve treatment efficiency and economic efficiency.

[0006] In a first aspect, an embodiment of the present invention provides an integrated comprehensive treatment method for waste salt and carbon dioxide in the steel industry, comprising:

[0007] After the industrial waste brine generated by the steel plant is concentrated, it is subjected to pretreatment and sodium salt extraction to obtain a sodium salt solution with a COD value lower than 10 mg / L; the remaining ammonia water after coking is introduced into the treated carbon dioxide flue gas of the hot blast furnace to obtain an ammonium bicarbonate solution;

[0008] Passing the sodium salt solution and the ammonium bicarbonate solution into an electrodialysis module for ion exchange to generate a dilute sodium bicarbonate solution and a dilute ammonium salt solution;

[0009] Using a reverse osmosis system to concentrate the dilute sodium bicarbonate solution to obtain a concentrated sodium bicarbonate solution;

[0010] The sodium bicarbonate concentrated solution is treated to remove calcium and magnesium, and the treated sodium bicarbonate concentrated solution is heated to 180-270° C. in a heating tank, and then introduced into the hot blast furnace carbon dioxide flue gas again to obtain a sodium bicarbonate solid product with a purity greater than or equal to 98.5%.

[0011] In combination with the first aspect, in one embodiment, a reverse osmosis system is used to concentrate the dilute ammonium salt solution to obtain a concentrated ammonium salt solution; the concentrated ammonium salt solution is passed into a cooling precipitation tank for cooling to obtain ammonium sulfate solid crystals.

[0012] In combination with the first aspect, in one embodiment, the pretreatment includes a treatment step for removing impurities, including: using flotation to remove insoluble impurities in the waste brine, preliminarily removing heavy metal ions and organic impurities, so that the COD content of the waste brine is less than 50 mg / L.

[0013] In combination with the first aspect, in one embodiment, the treatment step of removing organic matter includes: filtering organic matter in the waste brine using an ultrafiltration membrane to separate the sodium-containing salt water solution on the water production side;

[0014] The ozone advanced oxidation method is used to oxidize organic matter and reduce the COD value of the sodium salt solution to below 10 mg / L.

[0015] In combination with the first aspect, in one embodiment, a nanofiltration membrane group is used to separate the obtained sodium salt aqueous solution to obtain a monovalent sodium salt solution and a divalent sodium salt solution; the obtained monovalent sodium salt and divalent sodium salt solutions are concentrated to 9-10 g / L for standby use.

[0016] In combination with the first aspect, in one embodiment, the nanofiltration membrane group includes a NF150 membrane group, a NF90 membrane group and a NF210 membrane group, and after separation treatment, a NaCl solution and a Na2SO4 solution are obtained.

[0017] In combination with the first aspect, in one embodiment, the sodium bicarbonate concentrated solution is treated to remove calcium and magnesium, and the treated sodium bicarbonate concentrated solution is heated to 170-200° C. in a heating tank to obtain a sodium carbonate solid product with a purity of ≥99%.

[0018] In combination with the first aspect, in one embodiment, the electrodialysis module adopts four-chamber electrodialysis, including ten groups of homogeneous membrane components, each group of homogeneous membrane components includes a cathodic membrane, a cation membrane and a separator; the electrode liquid adopts 4% to 5% Na2SO4 solution.

[0019] In combination with the first aspect, in one embodiment, the step of concentrating the dilute sodium bicarbonate solution using a reverse osmosis system to obtain a concentrated sodium bicarbonate solution comprises:

[0020] The DTRO reverse osmosis system is used for multiple concentrations to reach a concentration of 25-35%.

[0021] In a second aspect, an embodiment of the present invention further provides an integrated comprehensive treatment device for waste salt and carbon dioxide in the steel industry, comprising: a mixing sedimentation tank for concentrating the industrial waste brine generated by the steel plant, and then performing pretreatment and sodium salt extraction;

[0022] The carbonization reaction tank is used to pass the residual ammonia water after coking into the treated carbon dioxide flue gas of the hot blast furnace to carry out a carbonization reaction to obtain an ammonium bicarbonate solution;

[0023] An electrodialysis module, used for passing the sodium salt solution and the ammonium bicarbonate solution into the electrodialysis module for ion exchange to generate a dilute sodium bicarbonate solution and a dilute ammonium salt solution;

[0024] A mixing reaction tank is used to heat and decarbonize the sodium bicarbonate concentrated solution obtained after concentration and calcium and magnesium removal treatment to produce a solid sodium bicarbonate product;

[0025] The cooling crystallization tank is used to purify and crystallize the dilute ammonium salt solution to obtain ammonium sulfate solid crystals.

[0026] The integrated comprehensive treatment method and device for waste salt and carbon dioxide in the steel industry provided by the embodiment of the present invention adopts electrodialysis technology to open up the last mile of zero emission in the steel industry, solves the treatment problem of waste salt resource utilization and carbon dioxide adsorption in the steel industry, and realizes the organic combination of miscellaneous salt resource utilization and carbon dioxide adsorption utilization. Combined with the current status of hot blast furnace flue gas treatment in steel plants, carbon dioxide is effectively fixed, and the efficiency of waste treatment in steel plants is improved. Cheap sodium chloride and sodium sulfate can both be used as sodium sources. Ammonia water collected in the previous process is introduced into cheap and easily available carbon dioxide to generate ammonium bicarbonate, generating sodium bicarbonate or sodium carbonate products with high economic value. In addition, by-products ammonium sulfate and ammonium chloride can also be sold as fertilizers. Economic and environmental benefits are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of an integrated comprehensive treatment method for waste salt and carbon dioxide in the steel industry in one embodiment;

[0028] Figure 2 A schematic diagram of the working process of an integrated comprehensive treatment method for waste salt and carbon dioxide in the steel industry in one embodiment;

[0029] Figure 3 A schematic diagram of an integrated comprehensive treatment device for waste salt and carbon dioxide in the steel industry in one embodiment;

[0030] Figure 4 Schematic diagram of an electrodialysis module in one embodiment. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0032] like Figure 1 As shown, the integrated comprehensive treatment method for waste salt and carbon dioxide in the steel industry provided by the present invention comprises the following steps:

[0033] S10, the industrial waste brine generated by the steel plant is concentrated and pre-treated and sodium salt is extracted to obtain a sodium salt solution with a COD value lower than 10 mg / L; the remaining ammonia water after coking is introduced into the treated carbon dioxide flue gas of the hot blast furnace to obtain an ammonium bicarbonate solution.

[0034] The industrial wastewater in the steel plant is concentrated and treated by the water treatment center of the whole plant, and then concentrated in the sedimentation tank to control the COD at 110-120 mg / L. The concentrations of calcium, magnesium, silicon and heavy metal ions are preliminarily measured using inductively coupled plasma optical emission spectrometry (ICP-OES).

[0035] The pretreatment includes removing impurities and heavy metals. In step S11, air flotation is used to remove insoluble impurities in the waste brine, and heavy metal ions and organic impurities are preliminarily removed to make the COD content of the waste brine less than 50 mg / L.

[0036] Pretreatment includes removing organic matter. Step S121, use ultrafiltration membrane to filter organic matter in waste brine, and separate sodium salt water solution on the water production side. The water production side refers to the side where the water (i.e. pure water or filtered water) produced after being treated by the membrane element during the membrane filtration process is located. In ultrafiltration technology, the water production side refers to the water filtered through the ultrafiltration membrane. The ultrafiltration membrane can intercept substances with larger molecular weight (such as proteins, bacteria, etc.), while allowing water molecules and substances with smaller molecular weight to pass through. Optionally, the ultrafiltration membrane includes: PVDF (polyvinylidene fluoride) material UF membrane, hollow fiber UF membrane, external pressure / internal pressure UF membrane. Hollow fiber UF membrane is preferred, which has the advantages of high flux, easy cleaning, and easy recovery.

[0037] Organic membranes such as ultrafiltration membranes can isolate organic matter and organic salts with larger molecular weight in water at the concentrated water end. The concentrated water end refers to the side where the high-concentration solution is formed after the impurities, ions or other unwanted substances are intercepted by the membrane element during the membrane filtration process. Common organic matter includes carbohydrates, proteins, oils, organic heavy metal compounds (lead, mercury, etc.), phenols, alcohols, aldehydes, ketones, lipids, etc. Depending on the composition and properties of the organic matter, the organic membrane can remove 60-90% of the organic matter.

[0038] The step of obtaining the ammonium bicarbonate solution includes: the residual ammonia water after coking is introduced into the treated hot blast furnace flue gas to form a mixed solution of ammonium bicarbonate, ammonium carbonate and ammonium carbamate, and the concentration is adjusted to 0.1-0.3 mol / L and the pH is adjusted to 7.5-8.0 for standby use. The pH adjustment is mainly achieved by using acetic acid (CH3COOH) and ammonia water, and the concentration is mainly adjusted by adding circulating treated water. Optionally, the concentration of the residual ammonia water is about 21%, and the ammonia nitrogen content is about 2600 mg / L. The CO2 content in the hot blast furnace flue gas is about 18-28%. The CO2 concentration after absorption is about 3%, and the absorption rate is more than 80%.

[0039] S122, use ozone advanced oxidation method to oxidize organic matter and reduce the COD value of sodium salt water solution to below 10mg / L. Ozone advanced oxidation method is a water and wastewater treatment technology based on the oxidizing properties of ozone (O3). It uses the strong oxidizing property of ozone to convert organic and inorganic pollutants in water into harmless or more easily removable products. Ozone molecules (O3) will decompose into oxygen and elemental oxygen in water. Elemental oxygen is very active and can react with organic matter in water to produce a series of oxidation products. These oxidation products will further decompose into smaller molecules and eventually convert into harmless substances such as carbon dioxide, water, etc., thereby meeting water quality standards, product standards and long-term operation requirements of membrane systems.

[0040] The sodium salt extraction step S13 includes: using a nanofiltration membrane group to separate different salt components to obtain monovalent sodium salt and divalent sodium salt respectively. According to the different charges and screening properties of inorganic salt ion groups, different salt components are separated by nanofiltration membranes. The selection of nanofiltration membranes here mainly depends on the specific ion components in the water sample, and a specific separation membrane group is selected according to the condensation state of the ion functional groups in water. For example, a company selected nanofiltration membrane groups including NF150 membrane group, NF90 membrane group and NF210 membrane group. First, the NF150 membrane group is used to separate the monovalent salt and divalent salt in the aqueous solution, and the monovalent salt and divalent salt are separated into the water production end and the concentrated water end respectively. Monovalent salts include NaCl and KCl, and divalent salts include Na2SO4, MgSO4, and CaSO4. Next, the NF90 membrane group is used to separate NaCl from other monovalent salts, so that NaCl is at the concentrated water end and other monovalent salts are at the produced water end; the NF210 membrane group is used to separate Na2SO4 from other divalent salts, so that Na2SO4 is at the produced water side and other divalent salts are at the concentrated water side.

[0041] Optionally, step S13 is followed by step S14, in which a DTRO reverse osmosis system is used to concentrate the salt solution separated in step S13 to 9-10 g / L for standby use. Optionally, in order to minimize the energy consumption of the entire process, each reverse osmosis system is equipped with a turbine energy recovery device, and the concentrated water after high-pressure pumping passes through the turbine energy recovery device before flowing through the membrane assembly. The concentrated water here has a high osmotic pressure due to the high salt content or other impurities, and thus carries a large pressure potential energy. The turbine energy recovery device uses this characteristic of the concentrated water to rotate the turbine blades at high speed, converting part of the kinetic energy into mechanical energy, which is then transmitted to the water inlet pump on the low-pressure side through the coupling, helping to increase the water inlet pressure and reduce the power required by the main boost pump.

[0042] S20, the sodium salt solution and the ammonium bicarbonate solution obtained in step S10 are passed into the electrodialysis module for ion exchange to generate a dilute sodium bicarbonate solution and a dilute ammonium salt solution. Optionally, the electrodialysis module uses four-chamber electrodialysis. The main internal structure is a homogeneous membrane assembly, and a total of ten groups are used. Each group of homogeneous membrane assemblies includes a negative membrane, a positive membrane and a spacer. Here, the selection of the number of homogeneous membrane groups in the electrodialysis mainly depends on the influence of ion conductivity, current density, selectivity, operational stability and economic benefits. Considering the influencing factors comprehensively, ten groups are selected with a daily hourly processing capacity of 100 kilograms as the optimal condition. The electrode liquid uses a 4% to 5% Na2SO4 solution for the best effect. Optionally, a sodium chloride solution can also be used as an alternative. Optionally, the concentration of the sodium salt solution as a raw material is 8 to 10%, and the concentration of ammonium bicarbonate is 10 to 12%. Optionally, the concentration of the generated sodium bicarbonate is 7 to 8%, the purity is ≥98.5%, and the concentration of ammonium salt is 8 to 10%. Optionally, the ammonium salt includes ammonium chloride and ammonium sulfate, with a purity of ≥98%. The specific type and purity depend on the composition of the feed and can be specifically adjusted according to the subsequent processing method.

[0043] S30, using a reverse osmosis system to concentrate the sodium bicarbonate dilute solution to obtain a sodium bicarbonate concentrated solution. The generated sodium bicarbonate dilute solution is concentrated multiple times by the DTRO reverse osmosis system to reach a concentration of 25-35%. At this time, the concentrated sodium bicarbonate solution can be directly reused in the system to the water treatment calcium and magnesium removal process, realizing the recycling of carbon fixation and water treatment in the whole process. Optionally, the number of concentrations is 3-6 times.

[0044] Optionally, a reverse osmosis system is used to concentrate the dilute ammonium salt solution to obtain a concentrated ammonium salt solution. The generated dilute ammonium salt solution is concentrated multiple times by the DTRO reverse osmosis system to obtain a concentrated solution with a concentration of 18-23%. Optionally, the number of concentrations is 2-4 times. The concentrated solution is passed into a cooling sedimentation tank for cooling, and the lower layer of ammonium sulfate solid crystals can be directly taken out from the lower port for subsequent use or sale. The core of reverse osmosis technology lies in the application of semipermeable membranes. The so-called semipermeable membrane refers to a special membrane that allows certain specific substances (usually water molecules) to pass through and prevents most solutes from passing through. In the natural osmosis process, the solvent (such as water) will spontaneously diffuse from the dilute solution side to the concentrated solution side until the concentrations on both sides reach equilibrium. In the reverse osmosis process, this natural trend is artificially reversed: by applying sufficient external pressure to the concentrated solution side, the solvent is forced to reversely penetrate the semipermeable membrane into the dilute solution side, thereby achieving the purpose of concentration. The main purpose of using the reverse osmosis membrane multiple times here is to make the concentrated solution obtain a nearly saturated solution at room temperature, thereby minimizing the crystallization cost.

[0045] S40, remove calcium and magnesium from the concentrated sodium bicarbonate solution, dry the treated concentrated sodium bicarbonate solution, and obtain a solid sodium bicarbonate product. For subsequent use or sale. The concentrated sodium bicarbonate solution is heated to 190-270°C in a heating tank, and then the carbon dioxide flue gas from the hot blast furnace is introduced again to saturate the solution and stabilize the product as sodium bicarbonate. The introduction of carbon dioxide flue gas from the hot blast furnace again can prevent the sodium bicarbonate from partially decomposing into sodium carbonate due to its unstable form after being heated, thereby improving the purity and stability of the product. The purity of the product is ≥98.5%, which meets the national standard for industrial sodium bicarbonate. Optionally, the concentrated sodium bicarbonate solution is continuously heated to 170-190°C to obtain a stable solid sodium carbonate product with a purity of ≥99%.

[0046] Optionally, the concentrated ammonium salt solution is passed into a cooling precipitation tank for cooling to obtain solid ammonium sulfate crystals.

[0047] like Figure 2 As shown, the integrated comprehensive treatment method for waste salt and carbon dioxide in the steel industry of this embodiment is as follows: the carbon dioxide flue gas from the hot blast furnace of the steel enterprise and the ammonia wastewater from the coking plant are carbonized in the reactor to fix carbon dioxide and generate ammonium bicarbonate solution. The comprehensive wastewater of the whole plant undergoes the pretreatment step of the water treatment center to obtain a relatively pure sodium chloride solution. Ammonium bicarbonate and sodium chloride solution react in the electrodialysis module to generate sodium bicarbonate solution and ammonium chloride solution. The sodium bicarbonate solution undergoes concentration (hot film evaporation) and crystallization steps to obtain a sodium bicarbonate product that meets the national standard, which is reused in the steps of decalcification and magnesium removal, pickling neutralization and heat treatment atmosphere control agent in the steel industry or sold to the outside. The ammonium chloride solution undergoes concentration and crystallization steps to obtain an ammonium chloride product that meets the national standard, which is supplied to the needs of industries such as metallurgy, petroleum, and agriculture.

[0048] Compared with traditional methods, the present invention realizes the organic combination of waste salt resource utilization and carbon dioxide adsorption and utilization. Combined with the current status of hot blast furnace flue gas treatment in steel plants, it effectively fixes carbon dioxide, increases environmental benefits, realizes carbon dioxide absorption and recycling within the steel industry, and improves the economic value of waste salt treatment.

[0049] The present invention also provides an integrated comprehensive treatment device for waste salt and carbon dioxide in the steel industry, such as Figure 3 As shown, including:

[0050] The mixing sedimentation tank S2 is used to concentrate the industrial waste brine generated by the steel plant and then perform pretreatment and sodium salt extraction.

[0051] The carbonization reaction tank S1 is used to pass the remaining ammonia water after coking into the treated carbon dioxide flue gas of the hot blast furnace to carry out a carbonization reaction to obtain an ammonium bicarbonate solution.

[0052] The electrodialysis module S3 is used to pass the sodium salt solution and the ammonium bicarbonate solution into the electrodialysis module for ion exchange to generate a dilute sodium bicarbonate solution and a dilute ammonium salt solution. The main structure and reaction logic are as follows: Figure 4 As shown: the electrodialysis device is equipped with 5 chambers, one of which is the pole chamber, which is mainly responsible for providing stable electron conversion electrical properties in the electrodialysis device; the other four are raw material chamber 1, raw material chamber 2 and product chamber 1, product chamber 2, and the specific positions can be swapped. The membrane pores in the electrodialysis membrane are arranged alternately to achieve stable ion exchange from the raw material to the product end.

[0053] The mixed reaction tank S5 is used to heat and decarbonize the sodium bicarbonate solution obtained after concentration and calcium and magnesium removal to generate a sodium carbonate solid product. The mixed reaction tank S5 is also used to introduce carbon dioxide into the sodium carbonate generated by decarbonization again for secondary carbonization, so that all the sodium carbonate is converted into sodium bicarbonate, and then crystallized and purified. In this way, the maximum carbon fixation amount is achieved.

[0054] For the specific limitations on the integrated comprehensive treatment device for waste salt and carbon dioxide in the steel industry, please refer to the limitations on the integrated comprehensive treatment method for waste salt and carbon dioxide in the steel industry mentioned above, which will not be repeated here.

[0055] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0056] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An integrated comprehensive treatment method for waste salt and carbon dioxide in the steel industry, characterized in that: include: After the industrial waste brine generated by the steel plant is concentrated, it is subjected to pretreatment and sodium salt extraction steps to obtain a sodium salt solution with a COD value lower than 10 mg / L; Passing the remaining ammonia water after coking into the treated carbon dioxide flue gas of the hot blast furnace to obtain an ammonium bicarbonate solution; Passing the sodium salt solution and the ammonium bicarbonate solution into an electrodialysis module for ion exchange to generate a dilute sodium bicarbonate solution and a dilute ammonium salt solution; Using a reverse osmosis system to concentrate the dilute sodium bicarbonate solution to obtain a concentrated sodium bicarbonate solution; The sodium bicarbonate concentrated solution is treated to remove calcium and magnesium, and the treated sodium bicarbonate concentrated solution is heated to 190-270° C. in a heating tank, and then introduced into the hot blast furnace carbon dioxide flue gas again to obtain a sodium bicarbonate solid product with a purity greater than or equal to 98.5%.

2. The method according to claim 1, characterized in that Using a reverse osmosis system to concentrate the dilute ammonium salt solution to obtain a concentrated ammonium salt solution; The concentrated ammonium salt solution is passed into a cooling precipitation tank for cooling to obtain ammonium sulfate solid crystals.

3. The method according to claim 1 or 2, characterized in that: The pretreatment includes a treatment step of removing impurities, including: using flotation to remove insoluble impurities in the waste brine, preliminarily removing heavy metal ions and organic impurities, and making the COD content of the waste brine less than 50 mg / L.

4. The method according to claim 3, characterized in that: The treatment step of removing organic matter includes: filtering organic matter in the waste brine with an ultrafiltration membrane to separate the sodium salt solution on the water production side; The ozone advanced oxidation method is used to oxidize organic matter and reduce the COD value of the sodium salt solution to below 10 mg / L.

5. The method according to claim 4, characterized in that The obtained sodium salt aqueous solution is separated and treated by a nanofiltration membrane group to obtain a monovalent sodium salt solution and a divalent sodium salt solution; the obtained monovalent sodium salt and divalent sodium salt solutions are concentrated to 9-10 g / L for later use.

6. The method according to claim 5, characterized in that The nanofiltration membrane group includes a NF150 membrane group, a NF90 membrane group and a NF210 membrane group, and NaCl solution and Na2SO4 solution are obtained after separation treatment.

7. The method according to claim 1, characterized in that The sodium bicarbonate concentrated solution is treated to remove calcium and magnesium, and the treated sodium bicarbonate concentrated solution is heated to 170-190° C. in a heating tank to obtain a sodium carbonate solid product with a purity of ≥99%.

8. The method according to claim 1, characterized in that The electrodialysis module adopts four-chamber electrodialysis, including ten groups of homogeneous membrane components, each group of homogeneous membrane components includes a negative membrane, a positive membrane and a spacer; the electrode liquid adopts 4% to 5% Na2SO4 solution.

9. The method according to claim 1, characterized in that: The method of using a reverse osmosis system to concentrate the dilute sodium bicarbonate solution to obtain a concentrated sodium bicarbonate solution comprises: The DTRO reverse osmosis system is used for multiple concentrations to reach a concentration of 25-35%.

10. An integrated comprehensive treatment device for waste salt and carbon dioxide in the steel industry, characterized in that: include: Mixing sedimentation tank, used to concentrate the industrial waste brine generated by the steel plant, and then perform pretreatment and sodium salt extraction; The carbonization reaction tank is used to pass the residual ammonia water after coking into the treated carbon dioxide flue gas of the hot blast furnace to carry out a carbonization reaction to obtain an ammonium bicarbonate solution; An electrodialysis module, used for passing the sodium salt solution and the ammonium bicarbonate solution into the electrodialysis module for ion exchange to generate a dilute sodium bicarbonate solution and a dilute ammonium salt solution; A mixing reaction tank is used to heat and decarbonize the sodium bicarbonate concentrated solution obtained after concentration and calcium and magnesium removal treatment to produce a solid sodium bicarbonate product; The cooling crystallization tank is used to purify and crystallize the dilute ammonium salt solution to obtain ammonium sulfate solid crystals.

Images