Method and system for recovering high-purity potassium bicarbonate and potassium sulfate from dust collected during blast furnace ferromanganese smelting

Abstract

This invention discloses a method and system for recovering high-purity potassium bicarbonate and potassium sulfate from dust collected during blast furnace ferromanganese smelting. It proposes for the first time a technical route for recovering potassium bicarbonate and potassium sulfate by washing blast furnace ferromanganese smelting dust. Addressing the characteristics of the ash washing wastewater, pre-oxidation coupled with reduction impurity removal achieves efficient removal of sulfite and high-valence iron and manganese ions without introducing new impurities, significantly improving the purity of the recovered potassium salts. Secondly, considering the difficulty and cumbersome operation of separating carbonate, sulfate, and chloride ions, and taking into account the carbon dioxide consumption required for potassium bicarbonate preparation, the invention employs acid hydrolysis of carbonates to recover carbon dioxide, recycling carbon, and controlling the liquid-phase anion composition to co-produce high-purity potassium bicarbonate and potassium sulfate, reducing the cost of bicarbonate recovery and the difficulty of salt separation. Simultaneously, it achieves zero emissions of wastewater and waste gas.

Description

Technical Field

[0001] This invention relates to the treatment of solid waste ash in the steel industry, specifically to a method and system for recovering high-purity potassium bicarbonate and potassium sulfate from dust collected during blast furnace ferromanganese smelting, belonging to the technical field of resource utilization treatment of solid waste ash in the steel industry. Background Technology

[0002] Ferromanganese is a ferroalloy material with a wide range of applications. Current production processes include the blast furnace method and the electric furnace method. The blast furnace method was the earliest developed and is still widely used in China. The blast furnace ferromanganese production process generates a large amount of dust, which mainly contains iron, manganese, fluorine, and alkali metals.

[0003] Currently, there is no specific technology for treating dust from blast furnace ferromanganese smelting. Some domestic steel plants use ferromanganese dust to produce cold-consolidated agglomerates and then reuse them in the furnace. Although this method is simple and low-cost, it leads to a decrease in the grade of the final ore, as well as the enrichment of fluoride and chloride ions, equipment corrosion, and nodule formation.

[0004] Currently, there are few reported technologies for the disposal of dust from ferromanganese smelting. Chinese patent CN105905925B, "A Method for Comprehensive Recovery of Valuable Metals from Dust and Residue from Ferromanganese Smelting," deals with dust from electric furnace ferromanganese smelting. The method involves water washing, followed by concentration and crystallization of the washing liquid to obtain potassium hydroxide. The washed residue is then leached with concentrated sulfuric acid, with an oxidant added to the leachate, pH adjusted, and a deweighting agent added. After fine filtration, concentration, crystallization, and drying, manganese sulfate is obtained. This process recovers potassium hydroxide, zinc slag, and manganese sulfate, employing a hydrometallurgical approach to recover multiple metals. However, this method treats dust generated from electric furnaces, whose composition differs from that of dust from blast furnace ferromanganese smelting. Studies have shown that blast furnace ferromanganese smelting dust contains large amounts of carbonates and fluoride ions, as well as high levels of sulfite ions in addition to sulfate ions. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes for the first time a technical route for recovering potassium bicarbonate and potassium sulfate by washing ash from blast furnace ferromanganese smelting. Taking advantage of the characteristics of the ash washing wastewater, pre-oxidation coupled with reduction purification achieves efficient removal of sulfite and high-valence iron and manganese ions without introducing new impurities, significantly improving the purity of the recovered potassium salts. Secondly, addressing the difficulties and cumbersome operations of separating carbonate, sulfate, and chloride ions, and considering the carbon dioxide consumption required for potassium bicarbonate production, this invention employs acid hydrolysis of carbonates to recover carbon dioxide, recycling carbon and controlling the liquid-phase anion composition, co-producing high-purity potassium bicarbonate and potassium sulfate, reducing bicarbonate recovery costs and salt separation difficulties. This invention produces no wastewater or waste gas emissions throughout the entire process, has high economic value, and meets the requirements of green and environmentally friendly production.

[0006] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is specifically as follows:

[0007] According to a first embodiment of the present invention, a method for recovering high-purity potassium bicarbonate and potassium sulfate from dust collected during blast furnace ferromanganese smelting is provided.

[0008] A method for recovering high-purity potassium bicarbonate and potassium sulfate from dust collected during blast furnace ferromanganese smelting includes the following steps:

[0009] 1) Ash washing: Industrial water is used to wash and leach the dust from blast furnace ferromanganese smelting to obtain ash washing wastewater.

[0010] 2) Wastewater pretreatment: First, an oxidant is added to the ash washing wastewater obtained in step 1) for oxidation treatment. Then, a reducing agent is added to the oxidized wastewater for reduction treatment. After solid-liquid separation, pretreated wastewater is obtained.

[0011] 3) Weak Alkaline Zinc Removal and Defluorination: Add acid to the pretreated wastewater obtained in step 2) to adjust the wastewater to a weak alkaline state for zinc precipitation and removal. Then add aluminum sulfate to the zinc-removed wastewater for defluorination treatment. After solid-liquid separation, the purified wastewater is obtained.

[0012] 4) Concentration to produce potassium bicarbonate: The wastewater obtained in step 3) is concentrated (the concentration ratio is generally 2 to 3 times, so that the potassium carbonate concentration in the wastewater reaches about 300 g / L). Then, carbon dioxide is introduced into the concentrated wastewater to carry out a carbonation reaction. After solid-liquid separation, high-purity potassium bicarbonate and desalination mother liquor are obtained.

[0013] 5) Circulating evaporation and salt separation: When the sulfate ion concentration in the desalination mother liquor is lower than the set value, the desalination mother liquor and the impurity removal wastewater are combined and proceeded to step 4). When the sulfate ion concentration in the desalination mother liquor is greater than or equal to the set value, acid is added to the desalination mother liquor to adjust the wastewater to neutral, and then high-purity potassium sulfate and sodium chloride are recovered through temperature-variable evaporation and salt separation.

[0014] Preferably, the method further includes the following steps:

[0015] 6) The carbon dioxide generated from adding acid to adjust the wastewater to a weakly alkaline state in step 3) and the carbon dioxide generated from adding acid to adjust the wastewater to a neutral state in step 5) are recycled to step 4) for carbonation reaction.

[0016] Preferably, the dust from the blast furnace ferromanganese smelting is dust containing iron, manganese, fluorine, alkali metals, carbonate and sulfite generated during ferromanganese smelting using the blast furnace method.

[0017] Preferably, in step 1), the water washing is a three-stage countercurrent water washing. The water-to-ash ratio during water washing is 1-7:1, preferably 2-5:1.

[0018] Preferably, in step 1), the ash washing wastewater is strongly alkaline wastewater, preferably with a pH > 10, and more preferably with a pH > 11.

[0019] Preferably, in step 2), the oxidant is a potassium permanganate solution. The concentration (mass concentration) of the potassium permanganate solution is 15-40%, preferably 20-30%.

[0020] Preferably, in step 2), the amount of oxidant added is 2-8% of the total mass of the wastewater, more preferably 3-5%. The oxidation treatment time is 5-50 min, more preferably 10-30 min.

[0021] Preferably, in step 2), the reducing agent is a soluble ferrous salt solution. The concentration (mass concentration) of the soluble ferrous salt solution is 10-30%, preferably 15-25%. Preferably, the soluble ferrous salt is ferrous sulfate and / or ferrous chloride.

[0022] Preferably, in step 2), the amount of reducing agent added is 3-9% of the total mass of the wastewater, preferably 4-6%. The reduction treatment time is 5-50 min, preferably 10-30 min.

[0023] Preferably, in step 3), the addition of acid to adjust the wastewater to a weakly alkaline state specifically involves adding dilute sulfuric acid to adjust the pH of the wastewater to 7.5-9, preferably 8-8.5.

[0024] Preferably, in step 3), the aluminum sulfate is an aluminum sulfate solution with a concentration (mass concentration) of 20-35%, more preferably a 25-30% aluminum sulfate solution. The amount of aluminum sulfate added is 0.1-0.8% of the total mass of the wastewater, preferably 0.3-0.6%. The defluorination treatment time is 0.3-2 hours, preferably 0.5-1.5 hours.

[0025] Preferably, in step 5), adding acid to adjust the wastewater to neutral specifically involves adding dilute sulfuric acid to adjust the pH of the wastewater to 6-7, preferably 6.5-7.

[0026] Preferably, in step 5), the sulfate ion concentration is set to 130-180 g / L, more preferably 140-160 g / L.

[0027] According to a second embodiment of the present invention, a system for recovering high-purity potassium bicarbonate and potassium sulfate from dust collected during blast furnace ferromanganese smelting is provided.

[0028] A system for recovering high-purity potassium bicarbonate and potassium sulfate from dust collected during blast furnace ferromanganese smelting, or a system for the method described in the first embodiment, is disclosed. The system comprises, in series, a three-stage countercurrent water washing device, a filter press, a redox tank, a first setback tank, a defluorination tank, an evaporation and concentration device, a carbonation reaction tank, a transition tank, a second setback tank, and an evaporation and salt separation device. The ash inlet of the three-stage countercurrent water washing device is connected to a ferromanganese ash conveying mechanism, and its water inlet is connected to an industrial water conveying pipeline. The air inlet of the carbonation reaction tank is connected to a carbon dioxide conveying pipeline. The transition tank is equipped with a sulfate ion sampling and detection meter, and its outlet is connected to the inlet of the evaporation and concentration device via a circulating water pipeline.

[0029] Preferably, the redox tank is equipped with an oxidant addition mechanism and a reducing agent addition mechanism. The first setback tank is equipped with a first acid addition mechanism, which contains a first pH probe. The defluorination tank is equipped with an aluminum sulfate addition mechanism. The second setback tank is equipped with a second acid addition mechanism, which contains a second pH probe.

[0030] Preferably, the exhaust ports of the first and second backflow tanks are both connected to the carbon dioxide delivery pipeline via carbon dioxide circulation pipelines.

[0031] In existing technologies, the dust generated during blast furnace ferromanganese smelting is complex in composition. Direct discharge of this dust pollutes the environment and wastes valuable resources. However, current treatment methods for this dust are unsatisfactory, lacking a complete processing technology. Achieving efficient resource utilization of blast furnace ferromanganese smelting dust has long been a major challenge for researchers in this field.

[0032] This invention proposes for the first time a technical concept for the resource-based treatment and recovery of dust from blast furnace ferromanganese smelting to obtain high-purity potassium bicarbonate, potassium sulfate, and sodium chloride. The process flow is as follows: 1) Washing of dust from blast furnace ferromanganese smelting: The dust from blast furnace ferromanganese smelting is conveyed into a three-stage countercurrent washing system for washing, resulting in filter cake and leaching wastewater (ash washing wastewater). The filter cake is transported off-site for disposal. 2) Purification and impurity removal of leaching wastewater: The leaching wastewater is conveyed into an oxidation reaction tank, and then potassium permanganate solution is added for oxidation treatment. The oxidized wastewater is then conveyed into a reduction reaction tank, and soluble ferrous salt solution is added for reduction. The reduced wastewater enters a first pH adjustment tank for pH adjustment (preferably by adding dilute sulfuric acid to adjust the pH of the wastewater to around 8). The pH-adjusted wastewater is then conveyed into a defluorination reaction tank, and aluminum sulfate is added for defluorination. The defluorinated wastewater enters a sedimentation tank. The sedimentation process yields sludge and supernatant (wastewater for impurity removal). The sludge is either transported off-site for disposal or returned to the sintering and ore blending process. 3) Co-production of potassium bicarbonate and potassium sulfate: The supernatant is transported to an evaporation and concentration equipment for evaporation and concentration treatment. After the wastewater is concentrated to a certain extent, it enters a carbonation reaction tank, where carbon dioxide is introduced for carbonation. The carbonated wastewater is separated by a centrifuge to obtain potassium bicarbonate and desalination mother liquor. The desalination mother liquor is preferentially returned to the evaporation and concentration section for recycling. When the sulfate concentration in the mother liquor is high, it is transported to a second pH adjustment tank for pH adjustment (preferably by adding dilute sulfuric acid to adjust the pH value of the wastewater to about 6-7). The adjusted wastewater is then transported to a salt separation system for variable-temperature evaporation to recover potassium sulfate and sodium chloride. At the same time, the carbon dioxide generated during the two pH adjustment processes is recycled for the carbonation reaction to promote the precipitation of potassium bicarbonate.

[0033] In this invention, the dust from blast furnace ferromanganese smelting is the dust generated during ferromanganese smelting using the blast furnace method. It is treated by mixing and washing industrial water with the dust in a certain ratio (e.g., a water-to-ash ratio of 1-7:1). After thorough washing and leaching, the easily soluble substances in the dust are released into the water. The washed filter residue is returned to sintering or transported for disposal. The resulting ash-washing wastewater is strongly alkaline (generally pH > 10). The cations in the ash-washing wastewater mainly include iron, manganese, potassium, sodium, and zinc, while the anions mainly include carbonate, sulfite, sulfate, chloride, fluoride, and hydroxide ions.

[0034] In this invention, the pretreatment and impurity removal of ash washing wastewater mainly includes four stages: oxidation, reduction, pH adjustment, and defluorination. ① Oxidation: Analysis shows that the ash washing wastewater contains a large amount of sulfite ions, which, if not removed, will reduce the purity of the recovered potassium sulfate. Strong oxidizing potassium permanganate is used to oxidize it to sulfate ions. The potassium introduced by potassium permanganate will not affect the water quality, and the introduced manganese will be removed in the subsequent reduction process. ② Reduction: Studies have shown that the ash washing wastewater after oxidation treatment contains high-valence manganese and iron, which can exist stably in highly alkaline solutions. Therefore, reducing ferrous salts are used to reduce high-valence manganese and iron ions to divalent manganese ions and trivalent iron ions. Then, the high alkalinity of the wastewater is utilized to achieve deep purification of manganese and iron in the wastewater. ③ pH Adjustment: Since the ash washing wastewater after oxidation and reduction treatment also contains a large amount of zinc metal, combined with the ion fraction analysis of potassium bicarbonate, adjusting the solution to a pH of around 8 can simultaneously achieve the removal of zinc metal and the purification of potassium bicarbonate. ④ Defluorination: The wastewater after the backwash treatment contains a high concentration of fluoride ions, which, if not removed, will affect the quality of salt products and corrode equipment. Aluminum sulfate is used to remove fluoride ions. Aluminum sulfate hydrolyzes in water at pH 8 to form aluminum hydroxide colloid, which adsorbs and removes fluoride ions without introducing impurity ions.

[0035] In this invention, after pretreatment and impurity removal, the ash washing wastewater is fed into an evaporation system for concentration. Carbon dioxide is then introduced into the concentrated wastewater to produce potassium bicarbonate. Taking advantage of the lower solubility of potassium bicarbonate compared to potassium carbonate, the potassium bicarbonate is separated and recovered. The recovered mother liquor is sampled for sulfate concentration testing. If the sulfate concentration is below a set value (e.g., 150 g / L), this portion of the mother liquor is returned to the evaporation system for further concentration. If the sulfate concentration is above the set value (e.g., 150 g / L), dilute sulfuric acid is added to adjust the pH to 6-7. Then, high-value potassium sulfate and sodium chloride products are separated and recovered through variable-temperature evaporation, achieving zero wastewater discharge and resource recovery.

[0036] In this invention, the wastewater after evaporation, concentration, and separation of potassium bicarbonate contains a large amount of carbonate, sulfate, and chloride ions, forming a five-element phase diagram, making salt separation difficult. Therefore, dilute sulfuric acid is added to adjust the pH of the wastewater to 6-7, causing acid hydrolysis of the carbonate ions. This converts the anions in the wastewater into sulfate and chloride ions, reducing the difficulty of evaporation and salt separation.

[0037] In this invention, a two-stage pH adjustment process is used to purify potassium bicarbonate and reduce the difficulty of separating potassium sulfate and sodium chloride. Simultaneously, due to the large amount of carbonate ions in the wastewater, a significant amount of carbon dioxide is generated during both pH adjustments. This released carbon dioxide is used for the carbonation reaction of potassium carbonate, promoting the precipitation of potassium bicarbonate. This saves production costs and achieves zero emissions of wastewater and waste gas.

[0038] In this invention, the concentration of the dilute sulfuric acid is an aqueous solution of sulfuric acid with a solute mass fraction of less than or equal to 70%.

[0039] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0040] 1. Based on the characteristics of dust from blast furnace ferromanganese smelting, this invention proposes for the first time a technical concept of using water washing to recover high-purity potassium bicarbonate and potassium sulfate from blast furnace ferromanganese smelting dust. The purification and removal of impurities from the wastewater are achieved through water washing, oxidation, reduction, backflushing, and defluorination. At the same time, the recycling of carbon dioxide through two-stage backflushing promotes the recovery and utilization of high-purity potassium bicarbonate and greatly ensures the high-value potassium sulfate salt and sodium chloride salt products obtained through temperature-variable evaporation separation and recovery.

[0041] 2. This invention is specifically designed for the water quality of ash washing wastewater, enabling the low-cost removal of key pollutants affecting the quality of by-products without introducing impurities or causing secondary pollution. Simultaneously, the separation process for carbonate, sulfate, and chloride ions is optimized, simplifying the complex multi-phase diagram, significantly reducing the difficulty of salt separation, and recovering a variety of high-value salt products while achieving zero emissions of wastewater and exhaust gas. Attached Figure Description

[0042] Figure 1 This is a flowchart illustrating the method for recovering high-purity potassium bicarbonate and potassium sulfate from dust collected during blast furnace ferromanganese smelting, as per the present invention.

[0043] Figure 2 This is a simplified diagram of the system structure for recovering high-purity potassium bicarbonate and potassium sulfate from dust collected during blast furnace ferromanganese smelting, as per the present invention.

[0044] Figure 3 This is a schematic diagram of the overall structure of the system for recovering high-purity potassium bicarbonate and potassium sulfate from dust collected during blast furnace ferromanganese smelting, as per the present invention.

[0045] Reference numerals: 1: Three-stage countercurrent water washing device; 101: Manganese iron ash conveying mechanism; 102: Industrial water conveying pipeline; 2: Filter press device; 3: Oxidation-reduction tank; 301: Oxidant adding mechanism; 302: Reducing agent adding mechanism; 4: First setback tank; 401: First acid adding mechanism; 402: First pH probe; 5: Defluoridation tank; 501: Aluminum sulfate adding mechanism; 6: Evaporation and concentration device; 7: Carbonation reaction tank; 701: Carbon dioxide conveying pipeline; 8: Transition tank; 801: Sulfate ion sampling and detection meter; 802: Circulating water pipeline; 9: Second setback tank; 901: Second acid adding mechanism; 902: Second pH probe; 10: Evaporation and salt separation device; 11: Carbon dioxide circulation pipeline. Detailed Implementation

[0046] The technical solution of the present invention will be illustrated below with examples. The scope of protection sought by the present invention includes, but is not limited to, the following embodiments.

[0047] A system for recovering high-purity potassium bicarbonate and potassium sulfate from dust collected during blast furnace ferromanganese smelting is disclosed. The system comprises, in series, a three-stage countercurrent water washing device 1, a filter press 2, a redox tank 3, a first setback tank 4, a defluorination tank 5, an evaporation and concentration device 6, a carbonation reaction tank 7, a transition tank 8, a second setback tank 9, and an evaporation and salt separation device 10. The ash inlet of the three-stage countercurrent water washing device 1 is connected to a ferromanganese ash conveying mechanism 101, and its water inlet is connected to an industrial water conveying pipeline 102. The air inlet of the carbonation reaction tank 7 is connected to a carbon dioxide conveying pipeline 701. The transition tank 8 is equipped with a sulfate ion sampling and detection meter 801, and its outlet is connected to the water inlet of the evaporation and concentration device 6 via a circulating water pipeline 802.

[0048] Preferably, the redox tank 3 is equipped with an oxidant adding mechanism 301 and a reducing agent adding mechanism 302. The first return tank 4 is equipped with a first acid adding mechanism 401, which contains a first pH probe 402. The defluorination tank 5 is equipped with an aluminum sulfate adding mechanism 501. The second return tank 9 is equipped with a second acid adding mechanism 901, which contains a second pH probe 902.

[0049] Preferably, the exhaust ports of the first backflow tank 4 and the second backflow tank 9 are both connected to the carbon dioxide delivery pipe 701 via the carbon dioxide circulation pipe 11.

[0050] Example 1

[0051] like Figure 2-3As shown, a system for recovering high-purity potassium bicarbonate and potassium sulfate from dust collected during blast furnace ferromanganese smelting is disclosed. The system comprises, in series, a three-stage countercurrent water washing device 1, a filter press 2, a redox tank 3, a first setback tank 4, a defluorination tank 5, an evaporation and concentration device 6, a carbonation reaction tank 7, a transition tank 8, a second setback tank 9, and an evaporation and salt separation device 10. The ash inlet of the three-stage countercurrent water washing device 1 is connected to a ferromanganese ash conveying mechanism 101, and its water inlet is connected to an industrial water conveying pipeline 102. The air inlet of the carbonation reaction tank 7 is connected to a carbon dioxide conveying pipeline 701. The transition tank 8 is equipped with a sulfate ion sampling and detection meter 801, and its outlet is connected to the water inlet of the evaporation and concentration device 6 via a circulating water pipeline 802.

[0052] Example 2

[0053] Example 1 is repeated, except that the redox pool 3 is equipped with an oxidant adding mechanism 301 and a reducing agent adding mechanism 302.

[0054] Example 3

[0055] Example 2 is repeated, except that the first callback pool 4 is provided with a first acid addition mechanism 401, which is provided with a first pH probe 402 inside.

[0056] Example 4

[0057] Example 3 is repeated, except that the defluorination tank 5 is equipped with an aluminum sulfate addition mechanism 501.

[0058] Example 5

[0059] Repeat Example 4, except that the second callback pool 9 is provided with a second acid addition mechanism 901, which is provided with a second pH probe 902 inside.

[0060] Example 6

[0061] Example 5 is repeated, except that the exhaust ports of the first callback pool 4 and the second callback pool 9 are both connected to the carbon dioxide delivery pipeline 701 through the carbon dioxide circulation pipeline 11.

[0062] Example 7

[0063] A method for recovering high-purity potassium bicarbonate and potassium sulfate from dust collected during blast furnace ferromanganese smelting includes the following steps:

[0064] 1) Ash washing: Industrial water is used to wash and leach the dust from blast furnace ferromanganese smelting to obtain ash washing wastewater.

[0065] 2) Wastewater pretreatment: First, an oxidant is added to the ash washing wastewater obtained in step 1) for oxidation treatment. Then, a reducing agent is added to the oxidized wastewater for reduction treatment. After solid-liquid separation, pretreated wastewater is obtained.

[0066] 3) Weak Alkaline Zinc Removal and Defluorination: Add acid to the pretreated wastewater obtained in step 2) to adjust the wastewater to a weak alkaline state for zinc precipitation and removal. Then add aluminum sulfate to the zinc-removed wastewater for defluorination treatment. After solid-liquid separation, the purified wastewater is obtained.

[0067] 4) Concentration to produce potassium bicarbonate: The wastewater obtained in step 3) is concentrated, and then carbon dioxide is introduced into the concentrated wastewater to carry out a carbonation reaction. After solid-liquid separation, high-purity potassium bicarbonate and desalination mother liquor are obtained.

[0068] 5) Circulating evaporation and salt separation: When the sulfate ion concentration in the desalination mother liquor is lower than the set value, the desalination mother liquor and the impurity removal wastewater are combined and proceeded to step 4). When the sulfate ion concentration in the desalination mother liquor is greater than or equal to the set value, acid is added to the desalination mother liquor to adjust the wastewater to neutral, and then high-purity potassium sulfate and sodium chloride are recovered through temperature-variable evaporation and salt separation.

[0069] Example 8

[0070] A method for recovering high-purity potassium bicarbonate and potassium sulfate from dust collected during blast furnace ferromanganese smelting includes the following steps:

[0071] 1) Ash washing: Industrial water is used to wash and leach the dust from blast furnace ferromanganese smelting to obtain ash washing wastewater.

[0072] 2) Wastewater pretreatment: First, an oxidant is added to the ash washing wastewater obtained in step 1) for oxidation treatment. Then, a reducing agent is added to the oxidized wastewater for reduction treatment. After solid-liquid separation, pretreated wastewater is obtained.

[0073] 3) Weak Alkaline Zinc Removal and Defluorination: Add acid to the pretreated wastewater obtained in step 2) to adjust the wastewater to a weak alkaline state for zinc precipitation and removal. Then add aluminum sulfate to the zinc-removed wastewater for defluorination treatment. After solid-liquid separation, the purified wastewater is obtained.

[0074] 4) Concentration to produce potassium bicarbonate: The wastewater obtained in step 3) is concentrated, and then carbon dioxide is introduced into the concentrated wastewater to carry out a carbonation reaction. After solid-liquid separation, high-purity potassium bicarbonate and desalination mother liquor are obtained.

[0075] 5) Circulating evaporation and salt separation: When the sulfate ion concentration in the desalination mother liquor is lower than the set value, the desalination mother liquor and the impurity removal wastewater are combined and proceeded to step 4). When the sulfate ion concentration in the desalination mother liquor is greater than or equal to the set value, acid is added to the desalination mother liquor to adjust the wastewater to neutral, and then high-purity potassium sulfate and sodium chloride are recovered through temperature-variable evaporation and salt separation.

[0076] 6) The carbon dioxide generated from adding acid to adjust the wastewater to a weakly alkaline state in step 3) and the carbon dioxide generated from adding acid to adjust the wastewater to a neutral state in step 5) are recycled to step 4) for carbonation reaction.

[0077] Example 9

[0078] Repeat Example 8, except that in step 2), the oxidant is a potassium permanganate solution.

[0079] Example 10

[0080] Repeat Example 9, except that in step 2), the reducing agent is a ferrous sulfate solution.

[0081] Example 11

[0082] Repeat Example 10, except that in step 5), the sulfate ion concentration is set to 150 g / L.

[0083] Application Example 1

[0084] The dust generated during blast furnace ferromanganese smelting using the system described in Example 6 and the method described in Example 11 will be used as raw material to prepare high-purity potassium bicarbonate and potassium sulfate. The specific process is as follows:

[0085] Dust from blast furnace ferromanganese smelting was subjected to a three-stage water washing and leaching process using industrial water at a water-to-ash ratio of 1:6. The resulting filter cake (transported for disposal) and washing wastewater (pH > 11) were then obtained through pressure filtration. A 25% potassium permanganate solution (5% of the total wastewater mass) was added to the resulting wastewater, and the mixture was stirred for oxidation treatment for 30 minutes. Next, a 20% ferrous sulfate solution (7% of the total wastewater mass) was added to the oxidized wastewater, and the mixture was stirred for reduction treatment for 30 minutes. After treatment, solid-liquid separation was performed to obtain pretreated wastewater.

[0086] Dilute sulfuric acid was added to the pretreated wastewater to adjust the pH to 8 (and maintained at this state) for precipitation treatment. Then, aluminum sulfate with a concentration of 30% (based on 0.6% of the total mass of the supernatant) was added to the zinc-removed supernatant for defluorination treatment for 1 hour. After treatment, solid-liquid separation was performed to obtain the purified wastewater.

[0087] The wastewater was concentrated until the potassium carbonate concentration in the solution reached approximately 300 g / L. Then, carbon dioxide was introduced into the concentrated wastewater to initiate a carbonation reaction for 1.5 hours. After the reaction, solid-liquid separation was performed to obtain high-purity potassium bicarbonate and a desalination mother liquor. The purity of potassium bicarbonate was detected to be 99.14%. The concentration of sulfate ions in the desalination mother liquor was detected to be 58.3 g / L. This desalination mother liquor was then returned to be mixed with the wastewater for further concentration and recycling. Simultaneously, the carbon dioxide generated during the alkalinity adjustment of the pretreated wastewater was used in the carbonation reaction of the concentrated wastewater. In this embodiment, the entire process produces no wastewater or exhaust gas emissions.

[0088] Application Example 2

[0089] The dust generated during blast furnace ferromanganese smelting using the system described in Example 6 and the method described in Example 11 will be used as raw material to prepare high-purity potassium bicarbonate and potassium sulfate. The specific process is as follows:

[0090] Dust from blast furnace ferromanganese smelting was subjected to a three-stage water washing and leaching process using industrial water at a water-to-ash ratio of 1:5. The resulting filter cake (transported for disposal) and ash-washing wastewater (pH > 11) were then obtained through pressure filtration. A 25% potassium permanganate solution (4.6% of the total wastewater mass) was added to the oxidized wastewater, and the mixture was stirred for 30 minutes for oxidation. A 20% ferrous sulfate solution (6.2% of the total wastewater mass) was then added to the oxidized wastewater, and the mixture was stirred for reduction for 30 minutes. After treatment, solid-liquid separation was performed to obtain pretreated wastewater.

[0091] Dilute sulfuric acid was added to the pretreated wastewater to adjust the pH to 8 (and maintained at this state) for precipitation treatment. Then, aluminum sulfate with a concentration of 30% (based on 0.5% of the total mass of the supernatant) was added to the zinc-removed supernatant for defluorination treatment for 1 hour. After the treatment, solid-liquid separation was performed to obtain the purified wastewater.

[0092] The wastewater was concentrated until the potassium carbonate concentration in the solution reached approximately 300 g / L. Then, carbon dioxide was introduced into the concentrated wastewater to initiate a carbonation reaction for 1.2 hours. After the reaction, solid-liquid separation was performed to obtain high-purity potassium bicarbonate and a desalination mother liquor. The purity of potassium bicarbonate was found to be 99.33%. The sulfate ion concentration in the desalination mother liquor was found to be 175.3 g / L. Dilute sulfuric acid was added to the desalination mother liquor to adjust its pH to 6.5. The neutralized desalination mother liquor was then evaporated to separate the salts, yielding potassium sulfate and sodium chloride. The purity of potassium sulfate was found to be 91.18%, and the purity of sodium chloride was 90.75%. Simultaneously, the carbon dioxide generated during the alkalinization process of the pretreated wastewater and the process of adjusting the desalination mother liquor to neutrality were used in the carbonation reaction of the concentrated wastewater. This embodiment of the process resulted in no wastewater or exhaust gas emissions.

Claims

1. A method for recovering high-purity potassium bicarbonate and potassium sulfate from dusting ash smelted with a blast furnace manganese iron, characterized by, The method comprises the following steps: 1) Washing ash: using industrial water to wash and leach the blast furnace ferromanganese smelting dust removal ash to obtain washing ash wastewater; 2) Wastewater pretreatment: first, adding an oxidizing agent to the washing ash wastewater obtained in step 1) for oxidation treatment; then adding a reducing agent to the wastewater after oxidation for reduction treatment, and obtaining pretreated wastewater after solid-liquid separation; the oxidizing agent is potassium permanganate solution; the reducing agent is soluble ferrous salt solution; 3) Weak base zinc removal and fluorine removal: adding acid to the pretreated wastewater obtained in step 2) to adjust the wastewater to weak alkaline for zinc removal by precipitation; then adding aluminum sulfate to the wastewater after zinc removal for fluorine removal treatment, and obtaining impurity-removed wastewater after solid-liquid separation; 4) Concentration and preparation of potassium bicarbonate: concentrating the impurity-removed wastewater obtained in step 3), then passing carbon dioxide into the concentrated wastewater for carbonation reaction, and obtaining high-purity potassium bicarbonate and desalination mother liquor after solid-liquid separation; 5) Circulating evaporation and salt separation: when the concentration of sulfate ions in the desalination mother liquor is lower than the set value, the desalination mother liquor is combined with the impurity-removed wastewater and step 4) is performed; when the concentration of sulfate ions in the desalination mother liquor is greater than or equal to the set value, acid is added to the desalination mother liquor to adjust the wastewater to neutral, and then high-purity potassium sulfate and sodium chloride are recovered by temperature-variable evaporation and salt separation; the set value of the concentration of sulfate ions is 130-180 g / L.

2. The method of claim 1, wherein: The method further comprises the following steps: 6) The carbon dioxide produced by adding acid to the wastewater to weak alkaline in step 3) and the carbon dioxide produced by adding acid to the wastewater to neutral in step 5) are recycled to step 4) for carbonation reaction.

3. The method of claim 1, wherein: The blast furnace ferromanganese smelting dust removal ash is a dust removal ash containing iron, manganese, fluorine, alkali metal, carbonate and sulfite generated during the smelting of ferromanganese by the blast furnace method.

4. The method of claim 1, wherein: In step 1), the water washing is three-stage countercurrent water washing; the washing ash wastewater is strong alkaline wastewater.

5. The method of claim 4, wherein: In step 1), the water ash ratio during water washing is 1-7:1; the washing ash wastewater is wastewater with pH>10.

6. The method of claim 5, wherein: In step 1), the water ash ratio during water washing is 2-5:1; the washing ash wastewater is wastewater with pH>11.

7. The method of claim 1, wherein: In step 2), the concentration of potassium permanganate solution is 15-40%.

8. The method of claim 7, wherein: In step 2), the concentration of potassium permanganate solution is 20-30%.

9. The method of claim 1, wherein: The amount of oxidizing agent added is 2-8% of the total mass of wastewater; the oxidation treatment time is 5-50 min.

10. The method of claim 9, wherein: The amount of oxidizing agent added is 3-5% of the total mass of wastewater; the oxidation treatment time is 10-30 min.

11. The method of claim 1, wherein: In step 2), the concentration of soluble ferrous salt solution is 10-30%.

12. The method of claim 11, wherein: In step 2), the concentration of soluble ferrous salt solution is 15-25%.

13. The method of claim 1, wherein: In step 2), the soluble ferrous salt is ferrous sulfate and / or ferrous chloride.

14. The method of claim 1, wherein: The amount of reducing agent added is 3-9% of the total mass of wastewater; the reduction treatment time is 5-50 min.

15. The method of claim 14, wherein: The amount of reducing agent added is 4-6% of the total mass of wastewater; the reduction treatment time is 10-30 min.

16. The method of claim 1, wherein: In step 3), the adjustment of the wastewater to weak alkaline by adding acid specifically refers to adjusting the pH of the wastewater to 7.5-9 by adding dilute sulfuric acid; and / or The aluminum sulfate is an aluminum sulfate solution with a concentration of 20-35%; the aluminum sulfate is added in an amount of 0.1-0.8% of the total mass of the wastewater; and the defluorination treatment time is 0.3-2h.

17. The method of claim 16, wherein: In step 3), the acid is added to adjust the wastewater to weak alkaline, specifically, dilute sulfuric acid is added to adjust the pH of the wastewater to 8-8.5; and / or The aluminum sulfate is an aluminum sulfate solution with a concentration of 25-30%; the aluminum sulfate is added in an amount of 0.3-0.6% of the total mass of the wastewater; and the defluorination treatment time is 0.5-1.5h.

18. The method of claim 1, wherein: In step 5), the acid is added to adjust the wastewater to neutral, specifically, dilute sulfuric acid is added to adjust the pH of the wastewater to 6-7; and / or The set value of the sulfate ion concentration is 140-160g / L.

19. A system for use in the method of any one of claims 1-18, characterized by: The system comprises three-stage countercurrent water washing devices (1), filter pressing devices (2), oxidation-reduction tanks (3), first readjustment tanks (4), defluorination tanks (5), evaporation concentration devices (6), carbonation reaction tanks (7), transition tanks (8), second readjustment tanks (9) and evaporation salt separation devices (10) arranged in series; the ash inlet of the three-stage countercurrent water washing devices (1) is connected with a manganese-iron ash conveying mechanism (101), and the water inlet is connected with an industrial water conveying pipeline (102); the gas inlet of the carbonation reaction tank (7) is connected with a carbon dioxide conveying pipeline (701); the transition tank (8) is provided with a sulfate ion sampling and detecting meter (801), and the water outlet is connected with the water inlet of the evaporation concentration device (6) through a circulating water conveying pipeline (802).

20. The system of claim 19, wherein: The oxidation-reduction tank (3) is provided with an oxidizing agent adding mechanism (301) and a reducing agent adding mechanism (302); the first readjustment tank (4) is provided with a first acid adding mechanism (401), and is provided with a first pH probe (402) inside; the defluorination tank (5) is provided with an aluminum sulfate adding mechanism (501); the second readjustment tank (9) is provided with a second acid adding mechanism (901), and is provided with a second pH probe (902) inside.

21. The system of claim 20, wherein: The exhaust outlets of the first readjustment tank (4) and the second readjustment tank (9) are connected with the carbon dioxide conveying pipeline (701) through a carbon dioxide circulating pipeline (11).

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