System and method for preparing potassium sulfite

Abstract

The application belongs to the technical field of potassium sulfite preparation, and discloses a potassium sulfite preparation system and a preparation method. The preparation system comprises: an absorber, which is used for forming an absorption solution containing potassium bisulfite by controlling the pH of a solution to be less than or equal to 6 through a potassium hydroxide absorption method; an oxygen removal device, whose inlet is connected with the outlet of the absorber; a regulating tank, which is connected with the outlet of the oxygen removal device, is used for supplementing potassium hydroxide and controlling the pH of a solution to be greater than or equal to 8, and obtains a potassium sulfite solution through a reaction; an evaporation crystallizer, whose inlet is connected with the outlet of the regulating tank; a solid-liquid separator, whose inlet is connected with the outlet of the evaporation crystallizer, is used for separating a slurry after crystallization into potassium sulfite solids and a crystallization mother liquor; and a dryer, which is used for drying the potassium sulfite solids to obtain a potassium sulfite product. The application can solve the problems of the influence of carbon dioxide on the quality of the potassium sulfite product and the oxidation of the potassium sulfite, and can improve the purity of the potassium sulfite product.

Description

Technical Field

[0001] This invention relates to the field of potassium sulfite preparation technology, and in particular to a potassium sulfite preparation system and preparation method. Background Technology

[0002] Potassium sulfite is a widely used chemical raw material, commonly found in industries such as chlor-alkali, papermaking, printing, textiles, leather, food, pharmaceuticals, and photography. A primary production method for potassium sulfite involves using potassium hydroxide to absorb SO2, generating a potassium sulfite solution, which is then evaporated, crystallized, dried, and packaged to obtain the final product. SO2 can originate from processes such as waste acid decomposition, sulfur-containing coal combustion, and smelting flue gas. Treating these SO2-containing flue gases with potassium hydroxide not only achieves environmental protection goals but also produces potassium sulfite, a product with higher economic value.

[0003] However, the inventors noted that these SO2-containing flue gases typically also contain impurities such as SO3, CO2, O2, and dust, which can affect the quality of potassium sulfite products. For example, SO3 reacts with potassium hydroxide to form K2SO4, CO2 reacts with potassium hydroxide to form K2CO3, O2 oxidizes K2SO3 to form K2SO4, and dust directly increases the impurities in the product. Dust and SO3 in the flue gas can be effectively removed using conventional flue gas purification technology of "gas scrubbing tower + wet electrostatic precipitator," thereby reducing their impact on product quality. However, CO2 and O2 in the flue gas have a significant impact on the quality of potassium sulfite products, and currently there are no good treatment methods.

[0004] Chinese patent CN 117228639A discloses a sulfur dioxide washing system and method for producing potassium products. This patent uses potassium hydroxide to absorb SO2-containing gas to generate an "SO2 contact liquid," namely potassium sulfite, potassium bisulfite, or a mixture thereof. The "SO2 contact liquid" is then dehydrated to obtain concentrated potassium sulfite, potassium bisulfite, or a mixture thereof. The patent controls the composition of the "SO2 contact liquid" by controlling the pH of the absorption reaction, with a pH range of 5-10, a preferred pH range of 7-9, and a more preferred pH range of 8-8.5.

[0005] Although the patent mentions that when SO2 gas contains CO2, the pH control range is less than 8.5, the inventors have noted that, according to the patented method, if the pH of the "SO2 contact liquid" is controlled at 8-8.5, the system is highly alkaline, and a large amount of CO2 will be absorbed into the "SO2 contact liquid." While the product is mainly potassium sulfite, the potassium carbonate impurity content is high. If the pH of the "SO2 contact liquid" is controlled at 5-7, the product is mainly potassium bisulfite, and potassium sulfite cannot be produced. If the pH of the "SO2 contact liquid" is controlled at 7-8, the potassium carbonate impurity content in the product decreases, but the potassium bisulfite impurity content increases significantly. Therefore, the method and system disclosed in this patent cannot effectively remove the influence of CO2 when preparing potassium sulfite.

[0006] In addition, the patent only proposes a "combustion process for controlling and limiting excess oxygen in SO2 gas flow", but this measure cannot effectively solve the oxidation problem in potassium sulfite production. For example, the upstream flue gas of smelting flue gas and waste acid cracking gas is usually controlled based on its own conventional or stable process requirements. It is not possible to excessively reduce the O2 concentration in order to adapt to the system. Under reasonable O2 concentration, the patent does not provide effective measures to control oxidation.

[0007] In summary, the current process for producing potassium sulfite using the potassium hydroxide absorption method has the following problems: 1) When using flue gas containing SO2 and CO2 to produce potassium sulfite, the CO2 gas will react to form potassium carbonate, affecting the purity of the product. 2) During the production of potassium sulfite, potassium sulfite is oxidized to potassium sulfate, which in turn affects the purity of the product. Summary of the Invention

[0008] The purpose of this invention is to provide a potassium sulfite preparation system and method, so as to effectively solve the influence of CO2 on the quality of potassium sulfite products and effectively control the oxidation of potassium sulfite, thereby preparing high-purity potassium sulfite products.

[0009] The above objective can be achieved through the following technical solutions: According to one aspect of the present invention, a potassium sulfite preparation system is provided, comprising: An absorber is used in the potassium hydroxide absorption method to form an absorbent containing potassium bisulfite by controlling the solution pH ≤ 6. An oxygen removal device, the inlet of which is connected to the outlet of the absorber, is used to remove dissolved oxygen from the absorbent liquid; An adjustment tank, connected to the outlet of the deoxygenation device, is used to add potassium hydroxide and control the pH of the solution to ≥ 8, and the reaction yields a potassium sulfite solution. An evaporator crystallizer, the inlet of which is connected to the outlet of the regulating tank; A solid-liquid separator, whose inlet is connected to the outlet of an evaporator crystallizer, is used to separate the solid and liquid components of the slurry after crystallization of potassium sulfite solution to obtain potassium sulfite solid and crystallization mother liquor; A dryer is used to dry the potassium sulfite solid to obtain the potassium sulfite product.

[0010] Preferably, the absorber includes a first absorber and a second absorber; the first absorber has a flue gas inlet, a water inlet, a liquid inlet, a liquid outlet, and an air outlet; the second absorber has an air inlet, a liquid inlet, an air outlet, and a liquid outlet; wherein, the air inlet of the second absorber is connected to the air outlet of the first absorber, the liquid inlet of the second absorber is used to add potassium hydroxide and control the pH of the solution in the second absorber to be ≥8; the liquid outlet of the second absorber is connected to the liquid inlet of the deoxygenation device, and the liquid outlet of the deoxygenation device is connected to the liquid inlet of the first absorber.

[0011] Preferably, the mother liquor outlet of the solid-liquid separator is connected to both the evaporator / crystallizer and the deoxygenation device.

[0012] Preferably, a first mixer is provided before the inlet of the deoxygenation device to mix and react the solution that is about to enter the deoxygenation device, and to adjust the pH of the solution to ≤6 to form the inlet liquid of the deoxygenation device.

[0013] Preferably, a cooler is provided on the pipeline connecting the outlet of the deoxygenation device to the inlet of the first absorber.

[0014] Preferably, a circulation pipeline is also provided between the liquid outlet and the liquid inlet of the second absorber.

[0015] Preferably, the deoxygenation method in the deoxygenation device is any one of air stripping deoxygenation, adsorption deoxygenation, or deoxygenation with reducing agents.

[0016] Preferably, when performing air stripping deoxygenation, an inert gas is introduced as the deoxygenation medium.

[0017] Preferably, a heater is provided before the inlet of the evaporator crystallizer to heat the potassium sulfite solution to the evaporation temperature, wherein the evaporation temperature is <90°C.

[0018] Preferably, a second mixer is provided before the heater; the liquid outlet of the evaporator crystallizer is connected to the second mixer through a circulation pipeline; the mother liquor outlet of the solid-liquid separator is connected to the second mixer; and the outlet of the regulating tank is connected to the second mixer.

[0019] Preferably, the outlet of the regulating tank is further provided with a preheater, and the outlet of the preheater is connected to the second mixer.

[0020] Preferably, the dryer has an inert gas inlet for using inert gas as the drying medium to perform low-temperature drying on the solid after solid-liquid separation, with a drying temperature of <85°C.

[0021] Preferably, it also includes: multiple conveying pumps connected between two adjacent devices to complete the material conveying between the two devices.

[0022] According to another aspect of the present invention, a method for preparing potassium sulfite is provided, comprising: Based on the potassium hydroxide absorption method, the solution pH is controlled to be ≤6, and the reaction forms an absorption solution containing potassium bisulfite; The potassium bisulfite-containing absorbent solution is deoxygenated to obtain a deoxygenated absorbent solution. Potassium hydroxide was added to the deoxygenated absorbent, and the pH of the solution was controlled to be ≥8. The reaction yielded a potassium sulfite solution. The potassium sulfite solution is evaporated and crystallized, and the slurry after crystallization is separated into solid and liquid to obtain potassium sulfite solid and crystallization mother liquor; The potassium sulfite solid was dried to obtain the potassium sulfite product.

[0023] Preferably, before the step of deoxygenating the potassium bisulfite-containing absorbent, the method further includes: mixing the potassium bisulfite-containing absorbent with the crystallization mother liquor, adjusting the solution pH to ≤ 6 to form the inlet liquid for the deoxygenation device, and deoxygenating the inlet liquid for the deoxygenation device.

[0024] Preferably, the evaporation temperature for evaporating and crystallizing the potassium sulfite solution is <90°C.

[0025] Preferably, the potassium sulfite solid is dried at a low temperature, with the drying temperature being <85°C.

[0026] According to another aspect of the present invention, another method for preparing potassium sulfite is provided, comprising: The sulfur dioxide-containing flue gas, water, and a portion of the deoxygenated absorbent are mixed in the first absorber, and the pH of the solution is controlled to be ≤6. The reaction forms a first absorbent containing potassium bisulfite, and the remaining flue gas after the reaction enters the second absorber. Potassium hydroxide is added to the second absorption tower, and the pH of the solution is controlled to be ≥8, and the reaction forms the second absorption liquid; The first and second absorbents are deoxygenated to obtain a deoxygenated absorbent. Potassium hydroxide was added to another portion of the deoxygenated absorbent, and the pH of the solution was controlled to be ≥8. The reaction yielded a potassium sulfite solution. The potassium sulfite solution is evaporated and crystallized, and the crystallized slurry is separated into solid and liquid components to obtain potassium sulfite solid and crystallization mother liquor; The potassium sulfite solid was dried to obtain the potassium sulfite product.

[0027] Preferably, before the step of deoxygenating the first absorbent and the second absorbent, the method further includes: mixing the first absorbent, the second absorbent, and the crystallization mother liquor, and adjusting the pH of the solution to ≤6 to form the inlet liquid of the deoxygenation device, and deoxygenating the inlet liquid of the deoxygenation device.

[0028] Preferably, the evaporation temperature for evaporating and crystallizing the potassium sulfite solution is <90°C.

[0029] Preferably, the potassium sulfite solid is dried at a low temperature, with the drying temperature being <85°C.

[0030] Beneficial effects: The potassium sulfite preparation system provided by this invention includes an absorber, a deoxygenation device, an adjustment tank, an evaporator crystallizer, and a dryer connected in sequence. Based on the potassium hydroxide absorption method, an absorbent containing potassium bisulfite is generated by controlling the pH reaction of the solution, and dissolved oxygen in the absorbent is removed. Then, potassium hydroxide is added to the deoxygenated absorbent and the pH reaction of the solution is controlled to obtain a potassium sulfite solution containing potassium sulfite, which is the evaporator crystallizer feed liquid. Through evaporation crystallization, solid-liquid separation, and drying, potassium sulfite product is obtained, thereby effectively reducing the impact of CO2 and O2 in flue gas on the quality of potassium sulfite product and improving the purity of potassium sulfite product. At the same time, this method is also a method for separating CO2 and SO2 gases.

[0031] Compared with the prior art, the present invention has the following advantages: 1) A potassium hydroxide solution was used to absorb flue gas containing SO2, CO2, and O2, and the pH of the absorption process was controlled to be ≤6 to obtain a potassium bisulfite absorbent. Because the pH of the absorbent was very low, the CO2 absorption rate was significantly reduced.

[0032] 2) Deoxygenate the potassium bisulfite absorbent solution to remove dissolved O2. Since the reaction rate of potassium sulfite and potassium bisulfite with O2 is limited by the liquid phase diffusion rate, reducing the O2 content in the solution can effectively reduce the oxidation degree of potassium sulfite and potassium bisulfite.

[0033] 3) Add potassium hydroxide solution to the deoxygenated absorbent to adjust the pH to ≥8. The potassium hydroxide reacts with potassium bisulfite to obtain a potassium sulfite solution. This potassium sulfite solution is then evaporated and crystallized to concentrate it to saturation and crystallize potassium sulfite crystals. These crystals are then separated by a solid-liquid separator to obtain wet potassium sulfite solids, while potassium carbonate enters the crystallization mother liquor. The potassium sulfite solution, i.e., the evaporation and crystallization influent, contains a small amount of potassium carbonate, but its concentration is much lower than its saturation concentration. Therefore, it will not crystallize during the evaporation and crystallization process. After solid-liquid separation, it enters the crystallization mother liquor, thus achieving further separation from the solid potassium sulfite. In other words, the crystallization operation further separates potassium carbonate from the potassium sulfite product, further improving the purity of the potassium sulfite product.

[0034] 4) The wet potassium sulfite solid is dried in a dryer to obtain a high-purity potassium sulfite product. Furthermore, a low-temperature drying process is preferred for the wet potassium sulfite solid, controlling the drying temperature to <85℃ to reduce the oxidation and decomposition of potassium sulfite.

[0035] 5) The evaporation and crystallization process is carried out at low temperature, with the temperature controlled below 90℃ (preferably <85℃), which can further reduce the oxidation and decomposition of potassium sulfite.

[0036] 6) The preferred embodiment of this application, by setting up a mixer and adjusting the solution to a slightly acidic condition with pH ≤ 6, is more conducive to the reaction of potassium carbonate and potassium bisulfite to produce potassium sulfite. The generated CO2 can be mixed into the outlet gas 005 through the deoxygenation device, which further reduces the impact of carbon dioxide on potassium sulfite.

[0037] 7) In the preferred embodiment of this application, two absorption towers are set up and the reaction is completed by adding potassium hydroxide in the subsequent process. This is beneficial for pH control, further reducing the CO2 absorption rate, and obtaining potassium bisulfite-containing absorption liquid and potassium sulfite solution. Attached Figure Description

[0038] Figure 1 This is a schematic diagram illustrating the principle of a method for preparing potassium sulfite in one embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the principle of a method for preparing potassium sulfite in one embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of a potassium sulfite preparation system in one embodiment of the present invention; Figure 3 Chinese diagram labeling: The following line segment numbers represent pipelines: 001: The purified gaseous material mainly contains SO2, CO2, O2, N2, and H2O; 002: The gas material at the outlet of absorber #1 mainly contains SO2, CO2, O2, N2, and H2O; 003: The gas material at the outlet of absorber #2 mainly contains CO2, O2, N2, and H2O; 004: Deoxygenating medium; 005: Deoxygenated gaseous material, mainly containing N2, O2, and CO2; 006: Drying medium; 007: Evaporation and crystallization secondary steam; 101: The liquid effluent from absorber #1 mainly contains potassium bisulfite, potassium sulfite and a small amount of potassium carbonate, and contains a small amount of dissolved oxygen; 102: The inlet liquid of the deoxygenation device mainly contains potassium bisulfite, potassium sulfite and a small amount of potassium carbonate, and contains a small amount of dissolved oxygen; 103: The circulating fluid of absorber #1 mainly contains potassium bisulfite, potassium sulfite and a small amount of potassium carbonate, and does not contain dissolved oxygen; 104: The drain liquid from absorber #1 mainly contains potassium bisulfite, potassium sulfite and a small amount of potassium carbonate, and does not contain dissolved oxygen; 105: The circulating fluid of absorber #2 mainly contains potassium sulfite, potassium hydroxide and potassium carbonate, and contains a small amount of dissolved oxygen; 106: The drain liquid from absorber #2 mainly contains potassium sulfite, potassium hydroxide and potassium carbonate, and contains a small amount of dissolved oxygen; 107: Potassium hydroxide solution; 108: Water; 109: Potassium hydroxide solution; 110: Evaporation and crystallization liquid inlet; 111: Evaporation and crystallization of the liquid; 112: Evaporation and crystallization circulating liquid; 113: Evaporated crystallization discharge liquid; 114: Crystallization circulating mother liquor; 115: Crystallization discharge of mother liquor; 201: Wet potassium sulfite solid; 202: Potassium sulfite products.

[0039] The following numbers represent equipment: PT01: Absorber #1; PT02: Absorber #2; PT03: Deoxygenation device; PT04: Evaporator / Crystallizer; TK01: Adjustment groove; TK02: Mother liquor tank; PU01: #1 circulating pump; PU02: #2 circulating pump; PU03: Feed pump for deaerator; PU04: Evaporation and crystallization circulating pump; PU05: Evaporation crystallization feed pump; HX01: Cooler; HX02: Preheater; HX03: Heater; CE01: Solid-liquid separator; DR01: Dryer; MX01: Mixer #1; MX02: Mixer #2 Detailed Implementation

[0040] The technical solution of the present invention will be clearly and completely described below with reference to embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0041] To address the issues of CO2 forming potassium carbonate and affecting product purity during potassium sulfite production from SO2-containing flue gas, and the oxidation of potassium sulfite to potassium sulfate during production, which also impacts product purity, this invention proposes a high-purity potassium sulfite preparation system and method. This effectively solves the problem of CO2 affecting product purity and effectively controls potassium sulfite oxidation, enabling the production of high-purity potassium sulfite products.

[0042] The following is for reference. Figure 1 The construction principle of this invention is described as follows: 1) A potassium hydroxide solution is used to absorb flue gas containing SO2, CO2, and O2. The pH of the absorption process is controlled to be ≤6, preferably within the range of 4-6, to obtain a potassium bisulfite absorbent. Due to the very low pH of the absorbent, the CO2 absorption rate is significantly reduced. The purpose of this step is to form a potassium bisulfite absorbent by controlling the pH based on the potassium hydroxide absorption method. This can be achieved by introducing a potassium hydroxide solution, sulfur dioxide-containing flue gas, and water into the absorber for reaction; alternatively, a potassium hydroxide solution can be introduced only at the beginning, and subsequently, the absorbent containing potassium bisulfite discharged from the deoxygenation device is not introduced, but instead reacts with the introduced sulfur dioxide to form the potassium bisulfite absorbent.

[0043] 2) The potassium bisulfite absorbent solution is deoxygenated using a deoxygenation device to remove dissolved O2. Since the reaction rate of potassium sulfite and potassium bisulfite with O2 is limited by the liquid-phase diffusion rate, reducing the O2 content in the solution can effectively reduce the oxidation degree of potassium sulfite and potassium bisulfite and improve product purity.

[0044] 3) The deoxygenated absorbent is sent to the conditioning tank, and potassium hydroxide solution is added to the tank to adjust the pH of the solution to 8-10, preferably 9-10, so that potassium hydroxide reacts with potassium bisulfite to obtain potassium sulfite solution.

[0045] 4) Evaporate and crystallize the potassium sulfite solution to concentrate it to saturation and crystallize potassium sulfite crystals. The potassium sulfite solution contains a small amount of potassium carbonate, but its concentration is much lower than its saturation concentration, so it will not crystallize. The potassium carbonate can be further separated from the potassium sulfite product through the crystallization process.

[0046] 5) After crystallization, the slurry is separated into wet potassium sulfite solid and crystallization mother liquor. The wet potassium sulfite solid enters the dryer, while the potassium carbonate enters the crystallization mother liquor. The crystallization mother liquor can be sent to be further treated with the absorbent (the carbon dioxide formed by the reaction can be discharged through the deoxygenation device) to avoid the enrichment of potassium carbonate in the evaporator crystallizer, reduce the potassium carbonate content in the product, and further reduce the impact of carbon dioxide on the product.

[0047] Preferably, the evaporation and crystallization process is carried out at a low temperature, with the temperature controlled below 85°C, to reduce the oxidation and decomposition of potassium sulfite and further improve the purity of potassium sulfite.

[0048] 6) The wet potassium sulfite solid is dehydrated in a dryer to obtain a high-purity potassium sulfite product. Preferably, a low-temperature drying process is used, controlling the drying temperature to <85℃, to reduce the oxidation and decomposition of potassium sulfite and further improve the purity of potassium sulfite.

[0049] In some embodiments, the potassium sulfite preparation system provided by the present invention, with reference to Figure 1 As shown, the system includes, in sequence, an absorber 1, a deoxygenation device 2, a regulating tank 3, an evaporator / crystallizer 4, a solid-liquid separator 5, and a dryer 6. In the absorber, an absorbent containing potassium bisulfite is produced by controlling the pH of the solution through a potassium hydroxide absorption method. After dissolved oxygen is removed from the absorbent by the deoxygenation device, it is fed into the regulating tank. A potassium hydroxide solution is added, and the pH is controlled to generate a potassium sulfite solution. Then, the solution is evaporated and crystallized, followed by solid-liquid separation and drying to obtain the potassium sulfite product and the crystallization mother liquor. The crystallization mother liquor can be stored in a mother liquor tank or recycled back to the evaporator / crystallizer.

[0050] By supplementing potassium hydroxide and controlling the pH of the reaction in each device, the impact of carbon dioxide on potassium sulfite was reduced, and the possibility of potassium sulfite being oxidized was reduced by the deoxygenation device, thereby improving the purity of the product.

[0051] In some implementations, reference Figure 2 As shown, a mixer is provided before the inlet of the deoxygenation device 2. The outlet of the absorber 1 and the mother liquor outlet of the solid-liquid separator 5 are connected to the mixer, so that they are mixed and reacted in the mixer. The pH of the solution is adjusted to ≤6 to form the deoxygenation device inlet liquid, which is then sent to the deoxygenation device 2 for deoxygenation.

[0052] The mother liquor for crystallization contains potassium carbonate and potassium hydroxide. A portion of it can be recycled to the evaporator crystallizer, while the other portion is sent to the mixer. This allows the potassium carbonate and potassium hydroxide in the mother liquor to react with the potassium bisulfite discharged from the absorber, thereby reducing the potassium carbonate content in the evaporator crystallizer and improving product purity.

[0053] In some implementations, two absorbers are set up. The first absorber controls the pH to ≤6 to form a potassium bisulfite absorbent. The second absorber absorbs the remaining SO2 flue gas after the reaction in the first absorber by adding potassium hydroxide. The resulting second absorbent is also sent to a deoxygenation device for deoxygenation.

[0054] By setting up two absorption towers and subsequently adding potassium hydroxide to complete the reaction, pH control is facilitated, further reducing the CO2 absorption rate and obtaining a potassium bisulfite-containing absorbent solution, thus obtaining a potassium sulfite solution.

[0055] In some preferred embodiments, the potassium bisulfite absorbent and the second absorbent are first mixed, and the pH of the solution is adjusted to ≤6 to form the inlet liquid of the deoxygenation device, which is then sent to the deoxygenation device for deoxygenation.

[0056] By first mixing and reacting, potassium carbonate in the second absorbent can react with potassium bisulfite to form carbon dioxide, thereby further reducing the influence of carbon dioxide on potassium bisulfite.

[0057] Figure 3 The structure of a potassium sulfite preparation system according to an embodiment of the present invention is shown. For example... Figure 3 As shown, it includes two absorbers, namely absorber #1 and absorber #2, as well as a deoxygenation device, a regulating tank, an evaporator crystallizer, and a dryer. The following section describes this embodiment in conjunction with... Figure 3 The connection methods between the devices in the system of the present invention and the reactions occurring within each device are described as follows.

[0058] Flue gas purification treatment: Before entering this system, SO2-containing flue gas 001 undergoes pre-treatment using a flue gas purification system. The appropriate purification process and system can be selected based on the impurities in the flue gas. A conventional flue gas purification process / system is: "Scrubber → Cooling Tower → Wet Electrostatic Precipitator," which can remove impurities such as SO3, HCl, HF, dust, and acid mist from the flue gas, while simultaneously reducing the flue gas temperature. The purified flue gas mainly contains SO2, CO2, O2, N2, and H2O, with a temperature of 40-70℃.

[0059] Absorber #1 has an inlet for SO2-containing flue gas, an inlet for water, an inlet for liquid, an outlet for liquid, and an outlet for gas. The inlet for liquid is connected to the outlet of the deaerator. Water 108 enters absorber #1 (PT01), and SO2-containing flue gas 001 enters absorber #1 (PT01) and reacts with circulating liquid 103. Circulating liquid 103 is mainly a mixture of potassium bisulfite and potassium sulfite. Potassium sulfite absorbs SO2 in the flue gas to form potassium bisulfite. The remaining SO2-containing gas 002 enters absorber #2 (PT02) through the outlet.

[0060] The #2 absorber has an air inlet, a liquid outlet, a liquid inlet, and an air outlet, and a circulation pipeline is provided between the liquid outlet and the liquid inlet.

[0061] The circulating liquid 105 of the No. 2 absorber is mainly a mixture of potassium sulfite, potassium carbonate, and potassium hydroxide. SO2-containing flue gas 002 reacts with the circulating liquid 105 of the No. 2 absorber. Potassium hydroxide solution 107 is added to the No. 2 absorber PTO2 through the inlet, causing it to absorb SO2 and CO2 gases from the flue gas to generate potassium sulfite and potassium carbonate. The pH of the reaction solution is controlled to be ≥8, preferably 9-10.

[0062] The gas 003 exhaust system at the outlet of absorber #2 is typically discharged through a chimney or exhaust stack. Before being released into the environment, treatment measures can be implemented according to environmental protection requirements, such as removing acid mist and particulate matter through a wet electrostatic precipitator, or removing NOx through a denitrification facility.

[0063] The circulating liquid 105 of the No. 2 absorber is sent to the No. 2 absorber PT02 through the No. 2 circulating pump PU02, and the No. 2 absorber discharge liquid 106 is drawn out from the No. 2 absorber circulating liquid 105 and sent to the No. 1 mixer MX01.

[0064] Mixer MX01 (No. 1) is located upstream of the deoxygenation device to mix and react the solution about to enter the deoxygenation device, and to adjust the pH of the solution to ≤6, thus forming the inlet liquid for the deoxygenation device. At this pH, the potassium carbonate in the mixer will react with the potassium bisulfite in the effluent 101 of absorber 1 to produce potassium sulfite. The generated CO2 is then mixed into the outlet gas 005 via the deoxygenation device. The installation of mixer MX01 (No. 1) in this invention plays a crucial role in addressing the effect of carbon dioxide on potassium sulfite. This mixer can be of any type, such as a stirred tank or a pipeline mixer.

[0065] The No. 1 mixer MX01 is connected to the outlet of the No. 2 absorber, the outlet of the No. 1 absorber, and the outlet of the crystallization mother liquor. The No. 1 absorber outlet 101 is discharged from the bottom of the No. 1 absorber PT01 and enters the No. 1 mixer MX01, where it mixes and reacts with the No. 2 absorber discharge liquid 106 and the crystallization mother liquor 115. The potassium hydroxide and potassium carbonate in the No. 2 absorber discharge liquid 106 and the crystallization mother liquor 115 react with the potassium bisulfite in the No. 1 absorber outlet 101 to generate potassium sulfite. Further, the pH of the mixture in the No. 1 mixer MX01 is controlled to be ≤6, that is, the pH of the No. 1 absorber circulating liquid 103 is controlled to be ≤6. Preferably, the pH of the mixture is controlled to be 5-6. The CO2 generated after the reaction of potassium carbonate and potassium bisulfite enters the outlet gas 005 of the deoxygenation device.

[0066] The mixed solution, which is the inlet liquid 102 of the deoxygenation device, is sent to the deoxygenation device PTO3 via the deoxygenation device feed pump PU03 to remove dissolved oxygen. The deoxygenation device of this invention employs any deoxygenation method, such as air stripping deoxygenation, adsorption deoxygenation, or reducing agent deoxygenation, for deoxygenation operation. The deoxygenation device preferably employs air stripping deoxygenation.

[0067] An oxygen removal medium inlet is provided on the deoxygenation unit PT03. Dissolved oxygen in the inlet liquid 102 of the deoxygenation unit is removed by adding oxygen removal medium 004 to PT03. Furthermore, the oxygen removal medium 004 used for gas stripping deoxygenation is typically N2, but other inert gases can also be used. The oxygen removal medium 004 can be recycled or regenerated as needed. The deoxygenated gas 005 can be mixed with the outlet gas 002 of absorber #1 and enter absorber #2 PT02. The deoxygenation operation effectively reduces the oxidation degree of potassium bisulfite and potassium sulfite.

[0068] The outlet of the deoxygenation device is connected to the inlet of absorber #1 via a pipeline. The deoxygenated solution is the circulating liquid 103 of absorber #1, which is sent to absorber #1 PT01 by circulating pump #1 PU01 to absorb SO2 in the flue gas. Optionally, a cooler is installed on the pipeline connecting the outlet of the deoxygenation device and the inlet of absorber #1. Based on the temperature of the circulating liquid 103 of absorber #1, it can be cooled and heat exchanged by cooler HX01 before entering absorber #1 PT01. The cooling medium can be cooling water, air, etc., with cooling water being the preferred cooling medium.

[0069] The outlet of the deoxygenation device is also connected to a regulating tank via a pipeline. By replenishing potassium hydroxide solution, the pH of the evaporation crystallization inlet liquid 110 is controlled to be ≥8, preferably 9-10. Specifically, as... Figure 3 As shown, the No. 1 absorber discharge liquid 104 is drawn from the No. 1 absorber circulating liquid 103 and enters the regulating tank TK01. Potassium hydroxide solution 109 is added to the regulating tank TK01, and after mixing and reaction, evaporation crystallization feed liquid 110 is obtained. In the regulating tank TK01, potassium hydroxide reacts with potassium bisulfite to produce potassium sulfite. The pH of the evaporation crystallization feed liquid 110 is adjusted to ≥8, preferably 9-10, to obtain a high-purity potassium sulfite solution. In specific operation, the amount of No. 1 absorber discharge liquid 104 and the amount of potassium hydroxide solution 109 are determined according to the amount of SO2 gas in the SO2-containing flue gas 001.

[0070] The evaporator crystallizer has an outlet at the bottom and a secondary steam outlet at the top. The evaporator crystallizer is equipped with a circulation pipeline. A #2 mixer and a heater are installed on the circulation pipeline. The #2 mixer is connected to a regulating tank and also to the crystallization circulating mother liquor pipeline. The heater is located near the inlet of the evaporator crystallizer.

[0071] In the evaporator crystallizer PT04, water in the dilute potassium sulfite solution is evaporated, becoming a supersaturated potassium sulfite solution, and potassium sulfite crystals are formed. The secondary steam 007 from the evaporation crystallizer is discharged from the top of PT04. After discharge, it can be further condensed into condensate or mechanically compressed and returned to the system as a heat source. The evaporation crystallization operation can be a single-stage or multi-stage operation to achieve the purpose of potassium sulfite crystallization. The evaporation crystallization process can employ single-effect evaporation crystallization, multi-effect evaporation crystallization, or MVR evaporation crystallization, and can be falling film evaporation crystallization, rising film evaporation crystallization, or forced circulation evaporation crystallization.

[0072] The evaporation crystallization liquid 111 is discharged from the bottom of the evaporation crystallizer PT04 and sent to the No. 2 mixer MX02 by the evaporation crystallization circulation pump PU04. It is then mixed with the evaporation crystallization feed 110 and the crystallization circulation mother liquor 114 that have entered the No. 2 mixer to obtain the evaporation crystallization circulation liquid 112.

[0073] The evaporation crystallization circulating liquid 112 first enters the heater HX03 and is heated to the evaporation temperature, which is controlled to be <90℃, preferably 75-85℃, to reduce the oxidation and decomposition of potassium sulfite. The heated evaporation crystallization circulating liquid 112 then enters the evaporation crystallizer PT04 for evaporation crystallization. The heating medium of the heater HX03 can be mechanically compressed secondary steam, fresh steam, or electric heating, etc.

[0074] Furthermore, a preheater can be installed on the outlet pipe of the regulating tank. The evaporation crystallization feed liquid 110 obtained after the reaction in the regulating tank is sent to the preheater HX02 for preheating via the evaporation crystallization feed pump PU05. The preheating operation can be single-stage preheating or multi-stage preheating. After preheating, it is heated to the evaporation temperature by the heater before the evaporation crystallizer. The HX02 preheater is a preferred option, for example, using the condensate of secondary steam for heating, which can be used for heat recovery within the system. The heating medium in the preheater can be fresh steam, secondary steam, hot water, etc., or it can be electrically heated. The preferred heating medium is the condensate of the evaporation crystallization secondary steam 007. The preheated solution enters the #2 mixer MX02 and finally enters the evaporation crystallizer PT04 for crystallization.

[0075] The inlet of the solid-liquid separator is connected to the outlet of the evaporator crystallizer, and the mother liquor outlet of the solid-liquid separator is connected to the mother liquor tank. Through evaporation crystallization and solid-liquid separation operations, potassium carbonate can be further separated from potassium sulfite products.

[0076] Evaporation crystallization discharge liquid 113 is drawn from evaporation crystallization effluent 111 and sent to solid-liquid separator CE01 for solid-liquid separation. The separated liquid is crystallization circulation mother liquor 114, which enters mother liquor tank TK02 and is then sent to mixer #2 MX02 via mother liquor pump PU06. The separated solid is wet potassium sulfite solid 201, which enters dryer DR01 for drying. The solid-liquid separator CE01 can be a centrifuge, filter press, etc., preferably a centrifuge.

[0077] Although the evaporation crystallization feed 110 discharged from the regulating tank is mainly composed of potassium sulfite, it also contains a small amount of potassium carbonate. After entering the evaporation crystallizer PTO4, this portion of potassium carbonate will also be concentrated along with the evaporation of water, but its concentration is much lower than that of potassium sulfite. When potassium sulfite reaches saturation and crystallizes, the concentration of potassium carbonate is far below its saturation concentration, so it will not crystallize. Therefore, the evaporation crystallization operation further separates potassium carbonate impurities from the wet potassium sulfite solid 201, allowing the potassium carbonate to enter the crystallization circulating mother liquor 114.

[0078] The mother liquor outlet or mother liquor tank outlet of the solid-liquid separator is also connected to the No. 1 mixer to draw the crystallization discharge mother liquor 115 from the crystallization circulation mother liquor 114 to the No. 1 mixer MX01, so that some potassium carbonate impurities are returned to the No. 1 mixer for treatment, avoiding the enrichment of potassium carbonate in the evaporation crystallizer PTO4, reducing the impact of potassium carbonate on the product, that is, reducing the impact of carbon dioxide on the product purity.

[0079] The dryer is equipped with a drying medium inlet. In dryer DR01, wet potassium sulfite solid 201 is dehydrated by drying medium 006 to obtain dry, high-purity potassium sulfite product 202. The drying medium 006 can be air, nitrogen, inert gas, etc., and before entering dryer DR01, the drying medium 006 can undergo necessary operations such as dehydration, dust removal, and heating.

[0080] Preferably, the dryer employs low-temperature drying, controlling the drying temperature to <85℃, preferably 70-75℃, to reduce the decomposition of potassium sulfite. Using low-temperature, inert gas drying further effectively reduces the oxidation and decomposition of potassium sulfite.

[0081] The following describes specific embodiments and... Figure 3 The technical solution and effects of the present invention are described below: Example 1 Potassium sulfite products are prepared by absorbing SO2-containing flue gas from the decomposition of waste acid with potassium hydroxide solution.

[0082] Flue gas purification: Waste acid decomposition utilizes the exothermic combustion of natural gas to pyrolyze waste sulfuric acid at high temperatures, producing flue gas containing SO2, SO3, CO2, N2, O2, and H2O. This flue gas, after dust collection and heat exchange in a waste heat boiler, is sent to a purification system for further treatment. Based on the composition of the waste acid decomposition flue gas, a conventional flue gas purification process of "scrubber → cooling tower → wet electrostatic precipitator" is adopted to remove SO3 and dust impurities from the flue gas, while simultaneously reducing the flue gas temperature. The purified flue gas contains approximately 5%-6% SO2 by volume, approximately 7-8% CO2 by volume, and has a temperature of approximately 45-65℃.

[0083] use Figure 3 The system shown is used to prepare potassium sulfite, including the following steps: 1) Absorption by absorber #1: The purified SO2-containing flue gas 001 enters absorber #1 PTO1 and reacts with circulating liquid 103 in absorber #1 to form potassium bisulfite. The remaining SO2-containing gas 002 enters absorber #2 PTO2.

[0084] 2) Absorption by absorber #2: In absorber #2 PTO2, SO2-containing flue gas 002 reacts with absorber #2 circulating liquid 105; potassium hydroxide solution 107 is added to absorber #2 to absorb SO2 and CO2 gas in flue gas, generating potassium sulfite and potassium carbonate. The pH of absorber #2 circulating liquid 105 is controlled to be ≥8, preferably 9-10.

[0085] The gas outlet gas 003 of the No. 2 absorber is discharged into the environment through the chimney. Since the flue gas contains a small amount of liquid droplets, a wet electrostatic precipitator is added before it is discharged into the environment to remove acid mist and particulate matter. The flue gas does not contain NOx, so no denitrification facility is required.

[0086] The circulating liquid 105 discharged from the No. 2 absorber is sent to the No. 2 absorber PT02 through the No. 2 circulating pump PU02, and the No. 2 absorber discharge liquid 106 is drawn out from the No. 2 absorber circulating liquid 105 and sent to the No. 1 mixer MX01.

[0087] 3) Pre-oxygenation mixing: The effluent 101 from the bottom of absorber PT01 is discharged into mixer MX01, where it mixes and reacts with the effluent 106 from absorber 2 and the mother liquor 115 discharged from crystallization in mixer MX01 to generate potassium sulfite. The pH of the mixture is controlled at 5.

[0088] Meanwhile, the CO2 generated from the reaction of potassium carbonate and potassium bisulfite enters the outlet gas 005 of the deoxygenation device.

[0089] The No. 1 mixer is a stirring tank type.

[0090] 4) Deoxygenation: The mixed solution, namely the deoxygenation device inlet liquid 102, is sent into the deoxygenation device PTO3 via the deoxygenation device feed pump PU03. Nitrogen gas is added as the deoxygenation medium 004. The dissolved oxygen in the deoxygenation device inlet liquid 102 is removed by the gas stripping deoxygenation method, which effectively reduces the oxidation degree of potassium bisulfite and potassium sulfite.

[0091] After deoxygenation, gas 005 mixes with gas 002 from the outlet of absorber #1 and enters absorber #2, PTO2.

[0092] The deoxygenated solution is the circulating liquid 103 of absorber #1. It is sent to cooler HX01 by circulating pump #1 PU01 and cooled to about 40°C before entering absorber PT01 to absorb SO2 in the flue gas. The cooling medium in cooler HX01 is cooling water.

[0093] 6) Generation of potassium sulfite solution: The effluent 104 from the No. 1 absorber circulating liquid 103 is drawn into the regulating tank TK01. Potassium hydroxide solution 109 is added to the regulating tank TK01 and mixed. The potassium hydroxide reacts with potassium bisulfite to generate potassium sulfite, yielding the evaporation and crystallization feed liquid 110. By adjusting the pH of the mixed solution / evaporation and crystallization feed liquid 110 in the regulating tank to 9, a high-purity potassium sulfite solution is obtained. The amounts of effluent 104 from the No. 1 absorber and potassium hydroxide solution 109 are determined based on the amount of SO2 gas in the SO2-containing flue gas 001.

[0094] 7) Preheating: The evaporation crystallization feed liquid 110 is sent to the preheater HX02 via the evaporation crystallization feed pump PU05 for preheating. The preheating operation adopts two-stage preheating. The heating medium of the first-stage heat exchanger is the condensate of the secondary steam 007 from the evaporation crystallization process. The second-stage heat exchanger uses fresh steam to heat the solution temperature to 75-85℃.

[0095] 8) Mixing before evaporation and crystallization: The preheated solution, i.e., the evaporation and crystallization feed 110, enters the #2 mixer MX02 and finally enters the evaporation crystallizer PT04 for crystallization.

[0096] 9) Evaporation Crystallization: In the evaporator crystallizer PT04, the water in the dilute potassium sulfite solution is evaporated, becoming a supersaturated potassium sulfite solution, and potassium sulfite crystals are formed. The secondary steam 007 from the evaporation crystallization is discharged from the top of the evaporator crystallizer PT04, and after mechanical compression, it is returned to the heater HX03 as a heat source. The evaporation crystallization adopts a single-stage forced circulation evaporation crystallization process.

[0097] 10) Mother liquor circulation: The evaporation crystallization liquid 111 is discharged from the bottom of the evaporation crystallizer PT04 and sent to the 2# mixer MX02 via the evaporation crystallization circulation pump PU04. It is mixed with the evaporation crystallization feed 110 and the crystallization circulation mother liquor 114 sent into the 2# mixer to obtain the evaporation crystallization circulation liquid 112.

[0098] 11) Heating: The evaporation crystallization circulating liquid 112 first enters the heater HX03 and is heated to the evaporation temperature of 75-85℃. The heated evaporation crystallization circulating liquid 112 then enters the evaporation crystallizer PT04 for evaporation crystallization. The heating medium of the heater HX03 is mechanically compressed secondary steam.

[0099] 12) Solid-liquid separation: The evaporated crystallization discharge liquid 113 is drawn out from the evaporated crystallization liquid 111 and sent to the solid-liquid separator CE01, specifically a centrifuge, for solid-liquid separation; the separated liquid is the crystallization circulation mother liquor 114, potassium carbonate enters the crystallization circulation mother liquor 114, and the separated solid is wet potassium sulfite solid 201.

[0100] After the crystallization circulating mother liquor 114 enters the mother liquor tank TK02, it is sent to the #2 mixer MX02 by the mother liquor pump PU06; at the same time, the crystallization discharge mother liquor 115 is drawn out from the crystallization circulating mother liquor 114 to the #1 mixer MX01.

[0101] 13) Drying: The separated solid, wet potassium sulfite solid 201, enters dryer DR01. In dryer DR01, the wet potassium sulfite solid 201 is dehydrated by drying medium 006 to obtain dry, high-purity potassium sulfite product 202. The drying temperature is 70-75℃, and the drying medium 006 is nitrogen. Furthermore, the drying medium 006 undergoes necessary operations such as dehydration, dust removal, and heating before entering dryer DR01.

[0102] By mixing the effluent 106 from absorber #2, the crystallization discharge mother liquor 115, and the effluent 101 from absorber #1 in mixer #1 (MX01), and controlling the pH of the mixture to ≤6, the CO2 absorption rate is reduced. A deoxygenation device is used to reduce the oxidation levels of potassium sulfite and potassium bisulfite. After deoxygenation, potassium hydroxide solution 109 is added, and the pH of the evaporation crystallization inlet 110 is controlled to ≥8 to generate potassium sulfite solution. Finally, potassium carbonate is further separated from the potassium sulfite product through evaporation crystallization and solid-liquid separation. By controlling low-temperature evaporation and low-temperature drying, the oxidation and decomposition of potassium sulfite are further reduced, improving product purity.

[0103] The description of this invention is given for illustrative and descriptive purposes only and is not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A system for preparing potassium sulfite, characterized in that, include: An absorber is used in the potassium hydroxide absorption method to form an absorbent containing potassium bisulfite by controlling the solution pH ≤ 6. An oxygen removal device, the inlet of which is connected to the outlet of the absorber, is used to remove dissolved oxygen from the absorbent liquid; An adjustment tank, connected to the outlet of the deoxygenation device, is used to add potassium hydroxide and control the pH of the solution to ≥ 8, and the reaction yields a potassium sulfite solution. An evaporator crystallizer, the inlet of which is connected to the outlet of the regulating tank; A solid-liquid separator, whose inlet is connected to the outlet of an evaporator crystallizer, is used to separate the solid and liquid components of the slurry after crystallization of potassium sulfite solution to obtain potassium sulfite solid and crystallization mother liquor; A dryer is used to dry the potassium sulfite solid to obtain the potassium sulfite product.

2. The potassium sulfite preparation system according to claim 1, characterized in that, The absorber includes a first absorber and a second absorber. The first absorber has a flue gas inlet, a water inlet, a liquid inlet, a liquid outlet, and a gas outlet; The second absorber has an air inlet, a liquid inlet, an air outlet, and a liquid outlet; The second absorber's air inlet is connected to the first absorber's air outlet, and the second absorber's liquid inlet is used to add potassium hydroxide and control the pH of the solution in the second absorber to be ≥8. The outlet of the second absorber is connected to the inlet of the deoxygenation device, and the outlet of the deoxygenation device is connected to the inlet of the first absorber.

3. The potassium sulfite preparation system according to claim 1 or 2, characterized in that, The mother liquor outlet of the solid-liquid separator is connected to the evaporator crystallizer and the deoxygenation device, respectively.

4. The potassium sulfite preparation system according to claim 3, characterized in that, A first mixer is installed before the inlet of the deoxygenation device to mix and react the solution that is about to enter the deoxygenation device, and to adjust the pH of the solution to ≤6 to form the inlet liquid of the deoxygenation device.

5. The potassium sulfite preparation system according to claim 2, characterized in that, A cooler is installed on the pipeline connecting the liquid outlet of the deoxygenation device to the liquid inlet of the first absorber. And / or, a circulation pipeline is also provided between the liquid outlet and the liquid inlet of the second absorber.

6. The potassium sulfite preparation system according to claim 1, characterized in that, The deoxygenation method in the deoxygenation device is any one of air stripping deoxygenation, adsorption deoxygenation, or deoxygenation by reducing agents. In the case of air stripping deoxygenation, an inert gas is introduced as the deoxygenation medium.

7. The potassium sulfite preparation system according to claim 1, characterized in that, A heater is provided before the inlet of the evaporator crystallizer to heat the potassium sulfite solution to the evaporation temperature, which is <90°C.

8. The potassium sulfite preparation system according to claim 7, characterized in that, A second mixer is also provided in front of the heater; The liquid outlet of the evaporator crystallizer is connected to the second mixer via a circulation pipeline; The mother liquor outlet of the solid-liquid separator is connected to the second mixer; The outlet of the regulating tank is connected to the second mixer.

9. The potassium sulfite preparation system according to claim 8, characterized in that, The outlet of the regulating tank is also equipped with a preheater, which is connected to the second mixer through the outlet of the preheater.

10. The potassium sulfite preparation system according to claim 1, characterized in that, The dryer has an inert gas inlet for using inert gas as the drying medium to perform low-temperature drying of the solid after solid-liquid separation, with a drying temperature of <85℃.

11. The potassium sulfite preparation system according to claim 1, characterized in that, Also includes: Multiple transfer pumps are connected between two adjacent pieces of equipment to complete the material transfer between the two pieces of equipment.

12. A method for preparing potassium sulfite using the potassium sulfite preparation system of claim 1, characterized in that, include: Based on the potassium hydroxide absorption method, the solution pH is controlled to be ≤6, and the reaction forms an absorption solution containing potassium bisulfite; The potassium bisulfite-containing absorbent solution is deoxygenated to obtain a deoxygenated absorbent solution. Potassium hydroxide was added to the deoxygenated absorbent, and the pH of the solution was controlled to be ≥8. The reaction yielded a potassium sulfite solution. The potassium sulfite solution is evaporated and crystallized, and the slurry after crystallization is separated into solid and liquid to obtain potassium sulfite solid and crystallization mother liquor; The potassium sulfite solid was dried to obtain the potassium sulfite product.

13. The method for preparing potassium sulfite according to claim 12, characterized in that, The evaporation temperature for evaporating and crystallizing the potassium sulfite solution is <90℃, and the potassium sulfite solid is dried at a low temperature of <85℃. And / or, prior to the step of deoxygenating the potassium bisulfite-containing absorbent, the method further includes: mixing the potassium bisulfite-containing absorbent with the crystallization mother liquor, adjusting the solution pH to ≤ 6 to form the inlet liquid for the deoxygenation device, and deoxygenating the inlet liquid for the deoxygenation device.

14. A method for preparing potassium sulfite using the potassium sulfite preparation system of claim 2, characterized in that, include: The sulfur dioxide-containing flue gas, water, and a portion of the deoxygenated absorbent are mixed in the first absorber, and the pH of the solution is controlled to be ≤6. The reaction forms a first absorbent containing potassium bisulfite, and the remaining flue gas after the reaction enters the second absorber. Potassium hydroxide is added to the second absorption tower, and the pH of the solution is controlled to be ≥8, and the reaction forms the second absorption liquid; The first and second absorbents are deoxygenated to obtain a deoxygenated absorbent. Potassium hydroxide was added to another portion of the deoxygenated absorbent, and the pH of the solution was controlled to be ≥8. The reaction yielded a potassium sulfite solution. The potassium sulfite solution is evaporated and crystallized, and the crystallized slurry is separated into solid and liquid components to obtain potassium sulfite solid and crystallization mother liquor; The potassium sulfite solid was dried to obtain the potassium sulfite product.

15. The method for preparing potassium sulfite according to claim 14, characterized in that, The evaporation temperature for evaporating and crystallizing the potassium sulfite solution is <90℃, and the potassium sulfite solid is dried at a low temperature of <85℃. And / or, before the step of deoxygenating the first absorbent and the second absorbent, the method further includes: mixing the first absorbent, the second absorbent, and the crystallization mother liquor, and adjusting the pH of the solution to ≤6 to form the inlet liquid of the deoxygenation device, and deoxygenating the inlet liquid of the deoxygenation device.

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