Method and system for absorbing and solidifying carbon dioxide by using metallurgical industry waste brine and ammonia water

Abstract

The invention relates to a method and a system for absorbing and solidifying carbon dioxide by using metallurgical industry waste brine and ammonia water, which are characterized in that alkali is prepared by combining waste brine, ammonia water and industrial tail gas, CO2 and NaCl in the industrial tail gas containing CO2 and industrial waste brine are converted into recyclable sodium bicarbonate products, CO2 is absorbed and solidified, the emission of greenhouse gases is reduced, the industrial waste brine is comprehensively utilized, and the production cost is reduced. The industrial waste brine treatment problem is effectively solved, and waste resource utilization is truly achieved. According to the invention, manpower, material resources and financial resources consumed for treating industrial tail gas and industrial waste brine by a traditional process are avoided; and the use of an ammonia absorber is avoided on the system, the process flow is simplified, and the operation cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of carbon dioxide absorption and solidification, and in particular to a method and system for absorbing and solidifying carbon dioxide by utilizing metallurgical industrial waste brine and ammonia water. Background Art

[0002] Greenhouse gases are the main cause of global warming, and carbon dioxide is the main component of greenhouse gases. Reducing carbon dioxide emissions is an important measure to mitigate global warming. At present, various carbon dioxide emission reduction technologies in the world cannot meet the needs of rapid social development due to the constraints of economic costs. Therefore, the development of new technologies and methods for carbon dioxide emission reduction and recycling in industrial production has great environmental and economic benefits.

[0003] The combined alkali production process includes two processes: the first process is to pass ammonia into saturated salt water to form ammonia brine, then pass carbon dioxide into sodium bicarbonate precipitation, filter and wash to obtain NaHCO3 micro crystals, and then calcine to obtain soda ash products, the filtrate of which is a solution containing ammonium chloride and sodium chloride. The second process is to crystallize and precipitate ammonium chloride crystals from the filtrate containing ammonium chloride and sodium chloride.

[0004] Since the existing metallurgical industry will discharge a large amount of concentrated salt wastewater and flue gas containing different concentrations of carbon dioxide during production, the treatment of these emissions requires manpower, material and financial resources. In the alkali industry, concentrated brine and carbon dioxide are the raw materials required in the process. Therefore, the waste brine produced in the metallurgical industry absorbs and solidifies carbon dioxide. On the one hand, it combines industrial wastewater treatment technology with alkali production technology, and on the other hand, it can prepare sodium bicarbonate and by-product ammonium chloride, which can not only solve the problem of industrial waste brine treatment, but also reduce the emission of carbon dioxide greenhouse gas.

[0005] Chinese Patent 2021114311612 discloses "a waste salt resource treatment system and its treatment method". This patent uses waste salt and industrial carbon dioxide exhaust gas as raw materials to obtain high-purity industrial-grade baking soda, soda ash, ammonium chloride and other products. The waste salt and exhaust gas are refined respectively, and the obtained salt and carbon dioxide are used as raw materials to prepare industrial-grade baking soda, soda ash and ammonium chloride.

[0006] Chinese Patent 2022108278448 discloses "A waste resource coupling process system and method based on membrane technology". In this patent, fly ash from the incineration of domestic waste is treated to obtain potassium chloride and sodium chloride separations, which are then mixed with liquid nitrogen to obtain ammonia mother liquor, and then treated CO2-rich flue gas of different purities is introduced to obtain sodium carbonate or sodium bicarbonate after treatment.

[0007] Chinese Patent 2022115717736 discloses a "system and method for preparing soda ash from sodium sulfate", wherein ammonia water and effluent mother liquor are passed into a batching device, solid sodium sulfate is added to the batching device to obtain sodium ammonium sulfate brine, the sodium ammonium sulfate brine is sent to a carbonization reactor, carbon dioxide is passed into the carbonization reactor for carbonization reaction, and crystal slurry is obtained; the crystal slurry is sent to a centrifugal device for centrifugal treatment to obtain sodium bicarbonate wet salt and filtrate, and the sodium bicarbonate wet salt is sent to a calcination system for calcination to obtain soda ash. Ammonia water and carbon dioxide are used as raw materials instead of ammonium bicarbonate, which reduces the cost of raw materials; in addition, by first configuring sodium ammonium sulfate brine and then performing carbonization reaction, the centrifugal mother liquor obtained by the centrifugal device is in the crystallization range of ammonium sulfate before entering the evaporation crystallization system, so that ammonium sulfate can be directly evaporated and crystallized in large quantities, avoiding the high-energy consumption mother liquor treatment method of "first evaporation crystallization to produce sodium sulfate + then freezing crystallization to produce double salt + finally evaporation crystallization to produce ammonium sulfate", and high-purity ammonium sulfate can be obtained at the same time.

[0008] Chinese patent 2021108390759 discloses "a system and method for waste incineration flue gas purification combined with fly ash desalination". After the fly ash is treated, high-salt wastewater is obtained, which absorbs ammonia gas from the power plant to form a first mother liquor. NH4Cl crystals are precipitated from the first mother liquor, and the crystallized liquid is collected as the second mother liquor. The second mother liquor receives the flue gas from the power plant to obtain NaHCO3. The chlorine salts in the fly ash from waste incineration and the CO2 in the flue gas can be recycled, thereby solving the negative impact of chloride ions in fly ash treatment, and at the same time, the product NaHCO3 that can be used for flue gas dry purification and the by-product NH4Cl are obtained, which reduces the high cost of waste incineration flue gas purification, generates certain economic benefits, and reduces greenhouse gas emissions. Summary of the invention

[0009] The purpose of the present invention is to provide a method and system for absorbing and solidifying carbon dioxide by utilizing metallurgical industrial waste brine and ammonia water, so as to convert industrial tail gas containing CO2 and metallurgical waste brine into useful baking soda, which can not only reduce the emission of industrial carbon dioxide greenhouse gas, but also effectively solve the problem of industrial waste brine treatment; in addition, the use of ammonia water for combined alkali production simplifies the process flow and equipment and reduces the cost compared with the traditional combined alkali production process using ammonia gas.

[0010] To achieve the above object, the technical solution of the present invention is:

[0011] A method for absorbing and solidifying carbon dioxide by using metallurgical industrial waste brine and ammonia water, comprising the following steps:

[0012] 1) Pretreatment of industrial wastewater

[0013] Remove macromolecular particles and impurities from industrial waste brine;

[0014] 2) Prepare saturated ammonia salt solution

[0015] Adding salt and ammonia water to the pretreated industrial waste brine to obtain a saturated ammonia brine solution, wherein the molar ratio of NaCl to NH3 is ≥1:1;

[0016] 3) Absorption and solidification of carbon dioxide

[0017] Introducing industrial tail gas containing CO2 at a temperature below 45°C into a saturated aqueous ammonia solution, wherein the molar ratio of NH3 to CO2 is ≥1:1, and after the reaction is completed, cooling the reaction liquid temperature to below 65°C to obtain sodium bicarbonate solid and ammonium chloride aqueous solution;

[0018] 4) Separation

[0019] The sodium bicarbonate solid obtained in step 3) and the ammonium chloride aqueous solution are subjected to vacuum pressure filtration to obtain sodium bicarbonate.

[0020] Preferably, in step 1), the industrial waste brine is purified by membrane method to remove macromolecular particles with a particle size of 0.002 to 0.1 μm, impurities and proteins.

[0021] Preferably, in step 1), the industrial waste brine is separated to obtain high-concentration waste brine with a concentration of ≥10%.

[0022] Preferably, in step 2), stirring is continued during the process of adding salt and ammonia water to the industrial waste brine.

[0023] Preferably, in step 3), the CO2-containing industrial tail gas is dust-removed furnace tail gas or blast furnace tail gas.

[0024] Preferably, in step 3), the reaction liquid is cooled by water cooling or air cooling.

[0025] The industrial waste brine is purified by membrane method to remove the macromolecular particles and related impurities, and then enters the ultrafiltration system to intercept macromolecular substances and proteins with a particle size between 0.002 and 0.1 μm. The membrane in the ultrafiltration system allows small molecules and soluble solid brine to pass through, while intercepting colloids, proteins, microorganisms and macromolecular organic matter. The brine containing small molecules and soluble solids passes through the separation system to obtain high-concentration waste brine.

[0026] In order to obtain a saturated ammonia salt solution, it is necessary to add salt and ammonia water to the waste brine, and control the molar ratio of NaCl and NH3 in the saturated ammonia salt solution to be ≥ 1: 1. The salt and ammonia water are continuously stirred during the process of adding the waste brine to promote full contact between the waste brine and the salt and ammonia water.

[0027] The saturated ammonia brine is fully in contact with the industrial exhaust gas containing CO2 in the carbonation tower. The flow rate of the industrial exhaust gas is adjusted according to the different CO2 concentrations in the industrial exhaust gas, so that the CO2 in the industrial exhaust gas can be absorbed and solidified as much as possible, reducing carbon dioxide greenhouse gas emissions.

[0028] The product that has been completely reacted in the carbonation tower is passed through a vacuum filter press to achieve solid-liquid separation to obtain the main product sodium bicarbonate and the by-product ammonium chloride solution.

[0029] The present invention also provides a system for a method for absorbing and solidifying carbon dioxide using metallurgical industrial waste brine and ammonia water, comprising:

[0030] A membrane filter is provided with a waste brine inlet and a waste brine outlet; the waste brine inlet is connected to an industrial waste brine delivery pipeline;

[0031] A saturated ammonia-salt water storage tank, on which an ammonia water inlet, a salt inlet and a brine inlet are provided; the brine inlet is connected to the waste brine outlet of the membrane filter through a brine delivery pipeline and a first water pump;

[0032] An ammonia water storage tank is connected to the ammonia water inlet of the saturated ammonia water storage tank through an ammonia water delivery pipeline and a metering pump;

[0033] A carbonation tower, with a gas inlet and a material outlet at the bottom and a gas outlet and a material inlet at the top; the ammonia water inlet of the saturated ammonia brine storage tank is connected to the material inlet through a liquid delivery pipeline and a second water pump;

[0034] The inlet end of the vacuum filter press is connected to the material outlet of the carbonation tower through a pipeline.

[0035] Furthermore, it also includes an industrial tail gas storage tank, which is connected to the gas inlet of the carbonation tower through a gas delivery pipeline and a mass flow controller, and a cooler is installed on the gas delivery pipeline; preferably, an air volume regulating valve and / or a booster fan are sequentially arranged on the gas delivery pipeline.

[0036] Furthermore, it also includes a flash tank, which is provided with a liquid inlet, a liquid outlet and a gas outlet; the liquid inlet of the flash tank is connected to the waste brine outlet of the membrane filter through a pipeline, and the liquid outlet is connected to the brine inlet of the saturated ammonia brine storage tank through a pipeline.

[0037] Preferably, a plurality of gas inlets are provided in the circumferential direction at the lower portion of the carbonation tower.

[0038] The present invention utilizes a combined alkali production system of waste brine, ammonia water and industrial tail gas. Since ammonia water is directly used to prepare saturated ammonia brine, an ammonia absorber is not required, thereby simplifying the process flow and reducing the operating cost.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] The present invention utilizes the combined alkali production method to convert CO2 and NaCl into recyclable sodium bicarbonate products from industrial tail gas and industrial waste brine containing CO2, absorbs and solidifies CO2, reduces greenhouse gas emissions, comprehensively utilizes industrial waste brine, effectively solves the problem of industrial waste brine treatment, and truly achieves waste resource utilization. It avoids the human, material and financial resources consumed by traditional processes for treating industrial tail gas and industrial waste brine.

[0041] Compared with the common chemical absorption method (such as MEA solvent) to capture carbon dioxide in flue gas and then carry out oil recovery or geological storage, the method of the present invention can directly absorb carbon dioxide in the solidified flue gas to generate sodium bicarbonate, which reduces the process flow and is more economical.

[0042] The existing method of using solid waste (such as steel slag) to directly mineralize and absorb carbon dioxide in flue gas to generate calcium carbonate, the calcium carbonate generated on the surface of the steel slag will hinder the further absorption reaction of CO2, while the present invention absorbs and solidifies CO2 in the solution, which has the advantage of a fast carbon dioxide absorption and solidification reaction speed.

[0043] Compared with the traditional combined alkali production method, the combined alkali production method using waste brine, ammonia water and industrial tail gas does not use ammonia gas to prepare saturated ammonia brine, but directly uses ammonia water and brine to fully mix to obtain saturated ammonia brine, thereby avoiding the use of an ammonia absorber, simplifying the process flow and reducing the operating cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The present invention is a process flow chart of an embodiment of the method of the present invention.

[0045] Figure 2 A schematic diagram of an embodiment of the system of the present invention. DETAILED DESCRIPTION

[0046] The present invention will be further described below in conjunction with the embodiments and drawings.

[0047] See also Figure 1 The method of using metallurgical industrial waste brine and ammonia water to absorb and solidify carbon dioxide in the present invention comprises the following steps:

[0048] 1) Pretreatment of industrial wastewater

[0049] Remove macromolecular particles and impurities from industrial waste brine;

[0050] 2) Prepare saturated ammonia salt solution

[0051] Adding salt and ammonia water to the pretreated industrial waste brine to obtain a saturated ammonia brine solution, wherein the molar ratio of NaCl to NH3 is ≥1:1;

[0052] 3) Absorption and solidification of carbon dioxide

[0053] Introducing industrial tail gas containing CO2 whose temperature is lowered to below 45°C into a saturated aqueous ammonia solution, wherein the molar ratio of NH3 to CO2 is ≥1:1, and after the reaction is completed, cooling the temperature of the reaction liquid to below 65°C to obtain sodium bicarbonate solid and ammonium chloride aqueous solution;

[0054] 4) Separation

[0055] The sodium bicarbonate solid obtained in step 3) and the ammonium chloride aqueous solution are subjected to vacuum pressure filtration to obtain sodium bicarbonate.

[0056] Preferably, in step 1), the industrial waste brine is purified by membrane method to remove macromolecular particles with a particle size of 0.002 to 0.1 μm, impurities and proteins.

[0057] Preferably, in step 1), the industrial waste brine is separated to obtain high-concentration waste brine with a concentration of ≥10%.

[0058] Preferably, in step 2), stirring is continued during the process of adding salt and ammonia water to the industrial waste brine.

[0059] Preferably, in step 3), the CO2-containing industrial tail gas is furnace tail gas or blast furnace tail gas.

[0060] Preferably, in step 3), the reaction liquid is cooled by water cooling or air cooling.

[0061] See also Figure 2 The system for absorbing and solidifying carbon dioxide by using metallurgical industrial waste brine and ammonia water according to the present invention comprises:

[0062] A membrane filter 1 is provided with a waste brine inlet and a waste brine outlet; the waste brine inlet is connected to an industrial waste brine delivery pipeline;

[0063] The saturated ammonia salt water storage tank 2 is provided with an ammonia water inlet, a salt inlet and a salt water inlet; the waste salt water outlet of the membrane filter 1 is connected to the salt water inlet through a salt water delivery pipeline and a first water pump 11;

[0064] The ammonia water storage tank 3 is connected to the ammonia water inlet of the saturated ammonia water storage tank 2 through an ammonia water delivery pipeline and a metering pump 12;

[0065] The carbonation tower 4 has a gas inlet and a material outlet at the bottom and a gas outlet and a material inlet at the top; the ammonia inlet of the saturated ammonia brine storage tank 2 is connected to the material inlet through a liquid delivery pipeline and a second water pump 13;

[0066] The inlet end of the vacuum filter press 5 is connected to the material outlet of the carbonation tower 4 through a pipeline, and the outlet end of the vacuum filter press 5 is respectively connected to the NaHCO3 roasting furnace 8 and the ammonia brine storage tank 9 through pipelines.

[0067] Furthermore, it also includes a flash tank 6, which is provided with a liquid inlet, a liquid outlet and a gas outlet; the liquid inlet of the flash tank 6 is connected to the waste brine outlet of the membrane filter 1 through a pipeline, and the liquid outlet is connected to the brine inlet of the saturated ammonia brine storage tank 2 through a pipeline.

[0068] Furthermore, it also includes an industrial tail gas storage tank, which is connected to the gas inlet of the carbonation tower through a gas delivery pipeline and a mass flow controller; a cooler 7 is installed on the gas delivery pipeline; preferably, an air volume regulating valve 14 and / or a booster fan 10 are sequentially arranged on the gas delivery pipeline.

[0069] Preferably, a plurality of gas inlets are arranged at the lower portion of the carbonation tower 4 along the circumferential direction.

[0070] Example 1

[0071] The method of using metallurgical industrial waste brine and ammonia water to absorb and solidify carbon dioxide has the following specific operating steps:

[0072] 1) Pretreatment of industrial wastewater

[0073] After the industrial cold rolling wastewater is pretreated by the membrane filter 1, the macromolecular particles and impurities in the wastewater are removed, and the wastewater is concentrated into a highly concentrated brine with a NaCl concentration of 10% by the flash tank 6;

[0074] 2) Prepare saturated ammonia salt solution

[0075] The obtained highly concentrated brine is transported to the saturated ammonia brine storage tank 2 through a water pump 11, and then salt and ammonia water (NaCl and NH3 molar ratio = 1:1) are added to the saturated ammonia brine storage tank 2 to prepare a saturated ammonia brine solution;

[0076] 3) Absorption and solidification of carbon dioxide

[0077] The saturated ammonia salt solution enters the carbonation tower 4 from the upper part of the carbonation tower through a water pump. The industrial tail gas with a CO2 concentration of 20% is purified and passes through the air volume regulating valve 14 (controlling the molar ratio of NH3 and CO2 to be 1:1). After passing through the flue gas cooler 7, its temperature is reduced to 45°C and then enters the carbonation tower 4 from the lower part of the carbonation tower. It is absorbed and reacted by the saturated ammonia salt solution flowing from top to bottom. After the reaction is completed, the reaction liquid is cooled to a temperature below 65°C in the cooling section to obtain sodium bicarbonate solid and ammonium chloride aqueous solution.

[0078] 4) Separation

[0079] The sodium bicarbonate solid and the ammonium chloride aqueous solution are separated by a vacuum filter press 5, the separated sodium bicarbonate enters a NaHCO3 roasting furnace 8, and the ammonium chloride aqueous solution enters an ammoniacal brine storage tank 9 to obtain a NaHCO3 concentration of 92%, and a carbon dioxide absorption efficiency of 56%.

[0080] Example 2

[0081] The method of using metallurgical industrial waste brine and ammonia water to absorb and solidify carbon dioxide has the following specific operating steps:

[0082] 1) Pretreatment of industrial wastewater

[0083] After the industrial cold rolling wastewater is pretreated by the membrane filter 1, the macromolecular particles and impurities in the wastewater are removed, and the wastewater is concentrated into a highly concentrated brine with a NaCl concentration of 10% by the flash tank 6;

[0084] 2) Prepare saturated ammonia salt solution

[0085] The obtained highly concentrated brine is transported to the saturated ammonia brine storage tank 2 through a water pump 11, and then salt and ammonia water (NaCl and NH3 molar ratio = 1.2:1) are added to the saturated ammonia brine storage tank to prepare a saturated ammonia brine solution;

[0086] 3) Absorption and solidification of carbon dioxide

[0087] The saturated ammonia salt solution enters the carbonation tower 4 from the upper part of the carbonation tower through a water pump. The industrial tail gas with a CO2 concentration of 20% is purified and passes through the air volume regulating valve 14 (controlling the molar ratio of NH3 and CO2 to be 1.5:1). After passing through the flue gas cooler 7, its temperature is reduced to 45°C and then enters the carbonation tower 4 from the lower part of the carbonation tower. It is absorbed and reacted by the saturated ammonia salt solution flowing from top to bottom. After the reaction is completed, the reaction liquid is cooled to a temperature below 65°C in the cooling section to obtain sodium bicarbonate solid and ammonium chloride aqueous solution.

[0088] 4) Separation

[0089] The sodium bicarbonate solid and the ammonium chloride aqueous solution were separated by a vacuum filter press to obtain NaHCO3 with a concentration of 92% and a carbon dioxide absorption efficiency of 64%.

Claims

1. A method for absorbing and solidifying carbon dioxide using metallurgical industrial waste brine and ammonia water, characterized in that: The steps include: 1) Pretreatment of industrial wastewater Remove macromolecular particles and impurities from industrial waste brine; 2) Prepare saturated ammonia salt solution Adding salt and ammonia water to the pretreated industrial waste brine to obtain a saturated ammonia brine solution, wherein the molar ratio of NaCl to NH3 is ≥1:1; 3) Absorption and solidification of carbon dioxide Introducing industrial tail gas containing CO2 at a temperature below 45°C into a saturated aqueous ammonia solution, wherein the molar ratio of NH3 to CO2 is ≥1:1; after the reaction is completed, cooling the temperature of the reaction liquid to below 65°C to obtain sodium bicarbonate solid and ammonium chloride aqueous solution; 4) Separation The sodium bicarbonate solid obtained in step 3) is separated from the ammonium chloride aqueous solution by vacuum filtration to obtain sodium bicarbonate.

2. The method for absorbing and solidifying carbon dioxide by using metallurgical industrial waste brine and ammonia water as claimed in claim 1, characterized in that: In step 1), the industrial waste brine is purified by membrane method to remove macromolecular particles with a particle size of 0.002 to 0.1 μm, impurities and proteins.

3. The method for absorbing and solidifying carbon dioxide by utilizing metallurgical industrial waste brine and ammonia water as claimed in claim 1 or 2, characterized in that: In step 1), the industrial waste brine is separated to obtain high-concentration waste brine with a concentration of ≥10%.

4. The method for absorbing and solidifying carbon dioxide by using metallurgical industrial waste brine and ammonia water as claimed in claim 1, characterized in that: In step 2), the process of adding salt and ammonia water to the industrial waste brine is carried out with continuous stirring.

5. The method for absorbing and solidifying carbon dioxide by using metallurgical industrial waste brine and ammonia water as claimed in claim 1, characterized in that: In step 3), the industrial tail gas containing CO2 is the tail gas from a furnace or a blast furnace after dust removal.

6. The method for absorbing and solidifying carbon dioxide by utilizing metallurgical industrial waste brine and ammonia water as claimed in claim 1 or 5, characterized in that: In step 3), the reaction liquid is cooled by water cooling or air cooling.

7. A system for the method of absorbing and solidifying carbon dioxide using metallurgical industrial waste brine and ammonia water as claimed in any one of claims 1 to 6, characterized in that: include: A membrane filter is provided with a waste brine inlet and a waste brine outlet; the waste brine inlet is connected to an industrial waste brine delivery pipeline; A saturated ammonia salt water storage tank is provided with an ammonia water inlet, a salt inlet, a salt water inlet and a saturated ammonia salt water outlet; the salt water inlet is connected to the waste salt water outlet of the membrane filter through a salt water delivery pipeline and a first water pump; An ammonia water storage tank is connected to the ammonia water inlet of the saturated ammonia water storage tank through an ammonia water delivery pipeline and a metering pump; A carbonation tower, wherein a gas inlet and a material outlet are arranged at the bottom, and a gas outlet and a material inlet are arranged at the top; the saturated ammonia brine outlet of the saturated ammonia brine storage tank is connected to the material inlet through a liquid delivery pipeline and a second water pump; The vacuum filter press has an inlet end connected to the material outlet of the carbonation tower through a pipeline, and an outlet end connected to the NaHCO3 roasting furnace and the alkali solution storage tank through pipelines.

8. The system according to claim 7, characterized in that: It also includes an industrial tail gas storage tank, which is connected to the gas inlet of the carbonation tower through a gas delivery pipeline and a mass flow controller, and a cooler is installed on the gas delivery pipeline; preferably, an air volume regulating valve and / or a booster fan are sequentially arranged on the gas delivery pipeline.

9. The system according to claim 7 or 8, characterized in that: It also includes a flash tank, which is provided with a liquid inlet, a liquid outlet and a gas outlet; the liquid inlet of the flash tank is connected to the waste brine outlet of the membrane filter through a pipeline, and the liquid outlet is connected to the brine inlet of the saturated ammonia brine storage tank through a pipeline.

10. The system according to claim 7, 8 or 9, characterized in that: A plurality of gas inlets are arranged circumferentially at the lower part of the carbonation tower.

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