Device and method for producing potassium sulfate and nitrogen-potassium fertilizer through flue gas desulfurization

Abstract

The invention discloses a potassium sulfate and nitrogen-potassium fertilizer co-production device and method based on flue gas desulfurization. The device comprises an ammonium sulfate buffer tank, a potassium sulfate first-section reactor, a first-section reaction centrifugal machine, a potassium sulfate second-section reactor and a second-section reaction centrifugal machine, and is provided with a matched nitrogen and potassium solution buffer tank, an energy-saving evaporation system, a nitrogen and potassium fertilizer separating and drying system and a potassium sulfate drying system. The process method comprises the following steps: conveying reaction liquid to a potassium sulfate first-section reactor through an ammonium sulfate buffer tank, adding KCl according to a certain molar ratio, and after centrifugal separation, enabling filtrate to enter a nitrogen-potassium solution buffer tank; a solid-phase product enters a second-stage reactor for deep reaction, and finally potassium sulfate is obtained through centrifugal drying. By establishing a graded reaction system and a K < + > conversion rate regulation and control mechanism, K < + > enters a nitrogen-potassium fertilizer system to synchronously prepare the nitrogen-potassium high-chlorine blended fertilizer (conforming to the GB / T 21633 standard) with the total nutrient being greater than or equal to 35%, a traditional ammonium chloride product is replaced, and the total conversion rate of K < + > being greater than or equal to 85% is realized through process simplification and additional value improvement.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flue gas treatment, in particular to a device and method for producing potassium sulfate and nitrogen-potassium fertilizer from flue gas desulfurization. BACKGROUND

[0002] As an important category of inorganic salts, potassium sulfate is widely used in agriculture, chemical industry and pharmaceutical field. It is particularly important in agriculture: not only provides essential potassium elements for crops, but also rich in sulfur, which is the core component of plant synthesis of amino acids, proteins and coenzymes. For economic crops such as tobacco, citrus and grape, which are sensitive to chlorine, the application of chlorine-free potassium sulfate can significantly improve the quality and stress resistance of fruits, and is the preferred fertilizer for high-end agriculture. Therefore, it is of great significance to develop efficient and low-cost potassium sulfate preparation technology.

[0003] In the existing production process, although the Mannheim method (high-temperature double decomposition reaction) is mature, it has problems such as high energy consumption (≥1.8 tons of coal per ton of product), serious equipment corrosion and difficult treatment of by-product hydrochloric acid; the potassium ore extraction method and the bitter brine method are difficult to scale due to resource distribution. In contrast, the double decomposition conversion method using ammonium sulfate and potassium chloride as raw materials has attracted much attention due to its easy availability of raw materials and resource utilization of by-product (ammonium chloride). However, this process still faces multiple technical bottlenecks:

[0004] The process proposed by Chinese patent CN93103865.0 adds cationic fatty amine compounds in the reaction, which increases the cost investment, and involves enrichment and separation problems caused by the added substances, which is not conducive to industrial production.

[0005] Chinese patent CN97112031.5 introduces a method for crystallizing and precipitating main product potassium sulfate by cooling, but the potassium conversion rate is only 70%, the resource utilization rate is low, and the evaporation and concentration process has high energy consumption, resulting in rising production cost.

[0006] The potassium sulfate preparation method based on two-stage conversion process proposed by Chinese patent CN201410598258.6 can produce potassium sulfate products with potassium oxide content of more than 50%, but the specific conversion rate is not specified, and the multiple washing and separation cause insufficient mother liquor circulation efficiency, resulting in resource waste, lack of high-value application of by-product potassium chloride, and limited economic benefit.

[0007] Therefore, it is necessary to provide a device and method for producing high-quality potassium sulfate and nitrogen-potassium fertilizer from ammonium sulfate produced by flue gas desulfurization, which has simple process and low energy consumption. SUMMARY

[0008] The technical problem to be solved by the present application is to provide a device and method for producing potassium sulfate and nitrogen-potassium fertilizer from flue gas desulfurization.

[0009] To solve the above technical problems, the technical scheme of the present application is:

[0010] A device for producing potassium sulfate and nitrogen-potassium fertilizer from flue gas desulfurization, comprising an ammonium sulfate buffer tank, a mother liquor tank, a nitrogen-potassium solution buffer tank, an energy-saving evaporation system, a nitrogen-potassium fertilizer separation and drying system, and a potassium sulfate drying system, wherein the ammonium sulfate buffer tank is connected with a potassium sulfate first-stage reactor through an ammonium sulfate liquid pump, and the outlet of the potassium sulfate first-stage reactor is connected with a first-stage reaction centrifuge; the filtrate outlet of the first-stage reaction centrifuge is connected with the nitrogen-potassium solution buffer tank, and the discharge outlet is connected with a potassium sulfate second-stage reactor; the discharge outlet of the potassium sulfate second-stage reactor is connected with a second-stage reaction centrifuge;

[0011] The discharge outlet of the second-stage reaction centrifuge is connected with the potassium sulfate drying system, and the filtrate outlet is connected with the mother liquor tank; the mother liquor tank is connected with the inlet of the potassium sulfate first-stage reactor through an ammonium sulfate mother liquor pipe, and a mother liquor pump is arranged on the ammonium sulfate mother liquor pipe;

[0012] The discharge outlet of the energy-saving evaporation system is connected with the inlet of the nitrogen-potassium fertilizer separation and drying system, and the external discharge evaporation mother liquor generated by the energy-saving evaporation system is sent to the nitrogen-potassium solution buffer tank for recycling;

[0013] The nitrogen-potassium outlet of the nitrogen-potassium fertilizer separation and drying system is connected with the inlet of the nitrogen-potassium solution buffer tank;

[0014] The nitrogen-potassium solution buffer tank is connected with the inlet of the energy-saving evaporation system through a nitrogen-potassium solution pump.

[0015] As one of the preferred technical solutions of the present application, an overflow pipe is arranged on the nitrogen-potassium solution buffer tank and connected with the mother liquor tank, when the liquid level in the nitrogen-potassium solution buffer tank exceeds a certain level, the solution is transported to the mother liquor tank through the overflow pipe to form a mother liquor closed-loop circulation system, and the residual K + in the solution in the nitrogen-potassium solution buffer tank is removed through material circulation to improve the utilization rate of K + ; the concentration gradient of SO4 2- and Cl - in the reaction system is maintained to effectively inhibit the reverse reaction; through the control of ion migration direction, K + in the system migrates to the potassium sulfate system, and Cl - migrates to the nitrogen-potassium fertilizer system.

[0016] As one of the preferred technical solutions of the present application, it further comprises a purification liquid tank, the outlet of the purification liquid tank is connected with the inlet of the potassium sulfate second-stage reactor through a purification liquid pump, the overflow port of the potassium sulfate second-stage reactor is connected with the purification liquid tank, and a water adding pipe is arranged on the purification liquid tank.

[0017] As one of the preferred technical solutions of the present application, the device can simultaneously produce potassium sulfate and nitrogen-potassium high-chlorine binary blended fertilizer, and the crude potassium sulfate is sent into the potassium sulfate two-stage reactor for refining; the nitrogen-potassium high-chlorine binary blended fertilizer solution can be transported to the energy-saving evaporation system through the nitrogen-potassium solution buffer tank, and then directly output the nitrogen-potassium fertilizer finished product after solid-liquid separation and drying treatment.

[0018] As one of the preferred technical solutions of the present application, the potassium sulfate one-stage reactor adopts a stirred tank reactor.

[0019] As one of the preferred technical solutions of the present application, the potassium sulfate two-stage reactor adopts a stirred tank reactor.

[0020] At the same time, the present application also provides a method based on the above-mentioned device, and the technical solution is as follows:

[0021] A method for producing potassium sulfate and nitrogen-potassium fertilizer by flue gas desulfurization, which adopts the device as described above, and the method specifically includes the following steps:

[0022] S1, first, the ammonium sulfate solution generated by flue gas desulfurization is sent into the ammonium sulfate buffer tank, and then the ammonium sulfate solution is sent into the potassium sulfate one-stage reactor through the ammonium sulfate liquid pump, and the mass ratio of potassium chloride to the ammonium sulfate solute in the solution is 0.9-1.3, the temperature in the potassium sulfate one-stage reactor is controlled at 25-100℃, and the stirring reaction is maintained at this temperature for 20-40 minutes, and the mass ratio of the total water amount to the total solid amount of the feed is 0.9-1.6;

[0023] S2, after the reaction in the potassium sulfate one-stage reactor is completed, the reaction is settled for 10-20 minutes, and the crude potassium sulfate slurry and the first filtrate are obtained by separation and filtration through the one-stage reaction centrifuge, the first filtrate is sent into the nitrogen-potassium solution buffer tank, and the crude potassium sulfate slurry is sent into the potassium sulfate two-stage reactor, and KCl solution is added into the potassium sulfate two-stage reactor, the concentration of the KCl solution is 5-20%, the KCl solution is sent into the potassium sulfate two-stage reactor through the purification liquid pump, and the amount of the KCl solution is 10-20% of the liquid volume in the first reaction, and after stirring reaction at 25-100℃ for 30-60 minutes, the reaction is settled for 10-20 minutes;

[0024] S3, after washing, the refined potassium sulfate product and the second filtrate are obtained by filtration through the two-stage reaction centrifuge, and the refined potassium sulfate is sent into the potassium sulfate drying system for fluidized bed drying to obtain the potassium sulfate finished product;

[0025] S4, then, the second filtrate is sent into the mother liquor tank, and the second filtrate in the mother liquor tank is sent into the potassium sulfate one-stage reactor through the mother liquor pump for recycling as the one-stage reaction conversion raw material;

[0026] S5, the liquid in the nitrogen-potassium solution buffer tank is pumped to the energy-saving evaporation system by a nitrogen-potassium solution pump, enters the nitrogen-potassium fertilizer separation and drying system after evaporation and crystallization, and the nitrogen-potassium fertilizer product is obtained through the nitrogen-potassium fertilizer separation and drying system, and the evaporation mother liquor discharged from the energy-saving evaporation system is sent to the nitrogen-potassium solution buffer tank for recycling.

[0027] As one of the preferred technical solutions of the present application, the density of the ammonium sulfate solution in S1 is 410-420 g / L.

[0028] As one of the preferred technical solutions of the present application, the percentage concentration of each ion in the primary filtrate is: K + 2.1-4.5%, NH4 + 8.5-11.7%, SO4 2- 7.0-12.5%, Cl - 12.0-16.0%.

[0029] As one of the preferred technical solutions of the present application, the percentage concentration of each ion in the secondary filtrate is: K + 7.0-8.5%, NH4 + 6.5-8.7%, SO4 2- 2.0-3.5%, Cl - 18.0-21.0%.

[0030] The above technical solution has the following advantages:

[0031] The present application purifies by two-stage reaction to obtain potassium sulfate product with potassium oxide content of more than 50% at room temperature, which meets the first-grade product standard of potassium sulfate product; by controlling the conversion rate of K + in the reaction process, part of K + enters the ammonium chloride system to directly generate nitrogen-potassium high-chlorine binary blended fertilizer (total nutrient content ≥ 35%) meeting the GB / T 21633 standard, replacing the traditional ammonium chloride product, realizing process simplification and added value improvement, and the total conversion rate of K + in the process reaches 85% without adding catalyst; the method uses flue gas desulfurization by-product ammonium sulfate as raw material to reduce external sulfur resource consumption, has mild process conditions, is easy to control, has low equipment material requirement, low investment cost, no three wastes emission in the production process, realizes efficient recovery of potassium element, and the comprehensive recovery rate is more than 90%. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of the device of the present application;

[0033] In the figure:

[0034] 1-Ammonium sulfate solution produced by flue gas desulfurization; 2-Ammonium sulfate buffer tank; 3-Ammonium sulfate liquid pump; 4-Mother liquor pump; 5-Mother liquor tank; 6-Purified liquid pump; 7-Purified liquid tank; 8-Nitrogen-potassium solution buffer tank; 9-Nitrogen-potassium solution pump; 10-Ammonium sulfate mother liquor pipe; 11-Second-stage reaction centrifuge; 12-Potassium sulfate second-stage reactor; 13-First-stage reaction centrifuge; 14-Potassium sulfate first-stage reactor; 15-Potassium chloride; 16-Energy-saving evaporation system; 17-Nitrogen-potassium fertilizer separation and drying system; 18-Nitrogen-potassium fertilizer finished product; 19-Potassium sulfate drying system; 20-Potassium sulfate finished product; 21-Water addition pipe; 22-Overflow pipe. Detailed Implementation

[0035] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0036] Example 1

[0037] As attached Figure 1 As shown, an apparatus and method for producing potassium sulfate and nitrogen-potassium fertilizer through flue gas desulfurization includes an ammonium sulfate buffer tank 2, a mother liquor tank 5, a nitrogen-potassium solution buffer tank 8, an energy-saving evaporation system 16, a nitrogen-potassium fertilizer separation and drying system 17, and a potassium sulfate drying system 19. The ammonium sulfate buffer tank 2 is connected to a potassium sulfate primary reactor 14 via an ammonium sulfate liquid pump 3. The outlet of the potassium sulfate primary reactor 14 is connected to a primary reaction centrifuge 13. The filtrate outlet of the primary reaction centrifuge 13 is connected to the nitrogen-potassium solution buffer tank 8, and its discharge port is connected to a potassium sulfate secondary reactor 12. The discharge port of the potassium sulfate secondary reactor 12 is connected to a secondary reaction centrifuge 11.

[0038] The discharge port of the two-stage reaction centrifuge 11 is connected to the potassium sulfate drying system 19, and the filtrate outlet is connected to the mother liquor tank 5; the mother liquor tank 5 is connected to the inlet of the potassium sulfate primary reactor 14 through the ammonium sulfate mother liquor pipe 10, and the ammonium sulfate mother liquor pipe 10 is equipped with a mother liquor pump 4.

[0039] The discharge port of the energy-saving evaporation system 16 is connected to the inlet of the nitrogen and potassium fertilizer separation and drying system 17, and the liquid discharge port of the energy-saving evaporation system 16 is connected to the nitrogen and potassium solution buffer tank 8.

[0040] The nitrogen and potassium outlet of the nitrogen and potassium fertilizer separation and drying system 17 is connected to the inlet of the nitrogen and potassium solution buffer tank 8;

[0041] The nitrogen-potassium solution buffer tank 8 is connected to the inlet of the energy-saving evaporation system 16 via the nitrogen-potassium solution pump 9.

[0042] As a further improved technical solution of the embodiment, the nitrogen-potassium solution buffer tank 8 is provided with an overflow pipe 22 connected with the mother liquor tank 5. When the liquid level in the nitrogen-potassium solution buffer tank 8 exceeds a certain level, the solution is transported to the mother liquor tank 5 through the overflow pipe 22 to form a mother liquor closed-loop circulation system. The residual K + The potassium sulfate reaction system is reintroduced to improve the utilization rate of K + ; maintain the concentration gradient of SO4 2- and Cl - in the reaction system to effectively inhibit the reverse reaction; control the ion migration direction to make K + migrate to the potassium sulfate system and C l- migrate to the nitrogen-potassium fertilizer system.

[0043] The nitrogen-potassium fertilizer separation and drying system 17 includes a centrifuge, a fluidized bed, etc.

[0044] As one of the preferred technical solutions of the embodiment, it further includes a purification liquid tank 7, the outlet of the purification liquid tank 7 is connected with the inlet of the potassium sulfate two-stage reactor 12 through a purification liquid pump 6, the overflow port of the potassium sulfate two-stage reactor 12 is connected with the purification liquid tank 7, and the purification liquid tank 7 is provided with a water adding pipe 21.

[0045] As one of the preferred technical solutions of the embodiment, the potassium sulfate one-stage reactor 14 is a stirred tank reactor. The potassium sulfate two-stage reactor 12 is also a stirred tank reactor. The stirred tank design ensures the uniformity of the reaction and promotes the complete chemical reaction.

[0046] The device can simultaneously produce potassium sulfate and nitrogen-potassium high-chlorine binary blended fertilizer. After the crude potassium sulfate is produced, it is sent to the potassium sulfate two-stage reactor 12 for refining. The nitrogen-potassium high-chlorine binary blended fertilizer solution can be transported to the energy-saving evaporation system 16 through the nitrogen-potassium solution buffer tank 8, and then after solid-liquid separation and drying treatment, the nitrogen-potassium fertilizer product 18 is directly produced.

[0047] Embodiment 2

[0048] A method for producing potassium sulfate and nitrogen-potassium fertilizer by flue gas desulfurization, which adopts the device as described in Embodiment 1. The method is as follows:

[0049] S1, first, the ammonium sulfate solution 1 produced by flue gas desulfurization is sent to the ammonium sulfate buffer tank 2, and then the ammonium sulfate solution is sent to the potassium sulfate one-stage reactor 14 through the ammonium sulfate liquid pump 3. The density of the ammonium sulfate solution is 415 g / L, and the mass ratio of potassium chloride 15 to the ammonium sulfate solute in the solution is 0.9. The temperature in the potassium sulfate one-stage reactor 14 is controlled at 25-50℃, and the solution is fully stirred and reacted at this temperature for 40 minutes. The total water amount and the total solid amount of the feed have a mass ratio of 0.9.

[0050] S2, after the reaction in the potassium sulfate primary reactor 14 is completed, it is settled for 10 minutes, and the crude potassium sulfate slurry and the primary filtrate are separated and filtered by the primary reaction centrifuge 13. The primary filtrate is introduced into the potassium sulfate solution buffer tank 8. The percentage concentration of each ion in the primary filtrate is as follows (in % w / v): K + 2.1-4.5%, NH4 + 8.5-11.7%, SO4 2- 7.0-12.5%, Cl - 12.0-16.0%; the crude potassium sulfate slurry is introduced into the potassium sulfate secondary reactor 12, and KCl solution is added to the potassium sulfate secondary reactor 12. The potassium sulfate secondary reactor 12 is mainly used to remove residual chlorine ions in the crude potassium sulfate slurry and improve the conversion rate of K+ by using KCl solution. The KCl solution is prepared by sending potassium chloride 15 into the purification liquid tank 7. The concentration of the KCl solution is 5% (molar concentration). The KCl solution is sent to the potassium sulfate secondary reactor 12 by the purification liquid pump 6. The amount of KCl solution is 20% of the liquid volume in the primary reaction. After sufficient stirring and reaction at a constant temperature of 25-50°C for 60 minutes, it is settled for 10 minutes.

[0051] S3, after the washing is completed, it is filtered by the secondary reaction centrifuge 11 to obtain refined potassium sulfate product and secondary filtrate. The refined potassium sulfate is introduced into the potassium sulfate drying system 19 and dried by the fluidized bed to obtain potassium sulfate finished product 20. The refined potassium sulfate product meets the requirements of GB / T 20406-2017 agricultural potassium sulfate first-class product: K2O≥50%, Cl - ≤2%, and the material with a crystal particle greater than 0.15 mm accounts for 70-80%, which ensures stable product quality.

[0052] S4, then the secondary filtrate is introduced into the mother liquor tank 5. The percentage concentration of each ion in the secondary filtrate is as follows (in % w / v): K + 7.0-8.5%, NH4 + 6.5-8.7%, SO4 2- 2.0-3.5%, Cl - 18.0-21.0%; the secondary filtrate in the mother liquor tank 5 is sent to the potassium sulfate primary reactor 14 by the mother liquor pump 4 and is used as a primary reaction conversion raw material for recycling;

[0053] S5, the liquid in the nitrogen-potassium solution buffer tank 8 is sent to the energy-saving evaporation system 16 by the nitrogen-potassium solution pump 9, enters the nitrogen-potassium fertilizer separation and drying system 17 after evaporation crystallization, and enters the fluidized bed drying after solid-liquid separation by the centrifuge of the nitrogen-potassium fertilizer separation and drying system 17 to obtain the finished product 18 of nitrogen-potassium fertilizer (total nutrient element content ≥ 35%, meeting the blending fertilizer GB / T 21633 standard, which is a binary high-chlorine blending fertilizer).

[0054] Example 3

[0055] A method for producing potassium sulfate and nitrogen-potassium fertilizer by flue gas desulfurization, which adopts the device as described in Example 1, and the method is specifically as follows:

[0056] S1, first, the ammonium sulfate solution generated by flue gas desulfurization 1 is sent to the ammonium sulfate buffer tank 2, and then the ammonium sulfate solution is sent to the potassium sulfate first reactor 14 by the ammonium sulfate liquid pump 3, wherein the density of the ammonium sulfate solution is 410 g / L, the mass ratio of potassium chloride 15 to the solute of ammonium sulfate in the solution is 1.3, the temperature in the potassium sulfate first reactor 14 is controlled at 50-80℃, and the total water volume and the total solid mass ratio of the feed are kept at 1.6 under sufficient stirring for 28 minutes;

[0057] S2, after the reaction in the potassium sulfate first reactor 14 is completed, it is settled for 15 minutes, and the crude potassium sulfate slurry and the first filtrate are obtained by separation and filtration by the first reaction centrifuge 13, the first filtrate is sent to the nitrogen-potassium solution buffer tank 8, and the percentage concentration of each ion in the above-mentioned first filtrate (calculated as % w / v) is as follows: K + 2.1-4.5%, NH4 + 8.5-11.7%, SO4 2- 7.0-12.5%, Cl - 12.0-16.0%; the crude potassium sulfate slurry enters the potassium sulfate second reactor 12, and KCl solution is added to the potassium sulfate second reactor 12, the potassium sulfate second reactor 12 mainly uses KCl solution to remove residual chlorine ions in the crude potassium sulfate slurry and improve the conversion rate of K+, the KCl solution is prepared by sending potassium chloride 15 to the purification liquid tank 7, the concentration of the KCl solution is 20% (molar concentration), the KCl solution is sent to the potassium sulfate second reactor 12 by the purification liquid pump 6, and the amount of KCl solution is 10% of the liquid volume in the first reaction, after sufficient stirring for 45 minutes at a constant temperature of 50-80℃, it is settled for 15 minutes;

[0058] S3, after the washing is completed, entering a two-stage reaction centrifuge 11 to filter, obtaining refined potassium sulfate product and secondary filtrate, the refined potassium sulfate enters a potassium sulfate drying system 19, after being dried by a fluidized bed, obtaining potassium sulfate finished product 20, the refined potassium sulfate product meets GB / T 20406-2017 agricultural potassium sulfate first-grade product: K2O≥50%, Cl - ≤2%, the product has 70-80% of material with crystal particles greater than 0.15mm, ensuring stable product quality;

[0059] S4, then the secondary filtrate enters a mother liquor tank 5, the secondary filtrate has the following ion percentage concentrations (in % w / v): K + 7.0-8.5%, NH4 + 6.5-8.7%, SO4 2- 2.0-3.5%, Cl - 18.0-21.0%; the secondary filtrate in the mother liquor tank 5 is sent to a potassium sulfate first-stage reactor 14 by a mother liquor pump 4, and is used as a first-stage reaction conversion raw material for recycling;

[0060] S5, the liquid in the nitrogen-potassium solution buffer tank 8 is sent to an energy-saving evaporation system 16 by a nitrogen-potassium solution pump 9, after evaporation and crystallization, enters a nitrogen-potassium fertilizer separation and drying system 17, after solid-liquid separation by a centrifuge of the nitrogen-potassium fertilizer separation and drying system 17, enters a fluidized bed drying to obtain nitrogen-potassium fertilizer finished product 18 (total nutrient element content≥35%, meeting the blending fertilizer GB / T 21633 standard, which is a binary high-chlorine blending fertilizer).

[0061] Example 4

[0062] A method for producing potassium sulfate and nitrogen-potassium fertilizer by flue gas desulfurization, which adopts the device as described in Example 1, and the method is as follows:

[0063] S1, first, the ammonium sulfate solution 1 generated by flue gas desulfurization is sent to the ammonium sulfate buffer tank 2, then the ammonium sulfate solution is sent to the potassium sulfate first-stage reactor 14 by the ammonium sulfate liquid pump 3, wherein the density of the ammonium sulfate solution is 420g / L, the potassium chloride 15 is added according to the mass ratio of the potassium chloride 15 to the ammonium sulfate solute in the solution =1.1, the temperature in the potassium sulfate first-stage reactor 14 is controlled at 80-100℃, and the reaction is kept at this temperature for 20 minutes, and the total water amount and the total solid mass ratio of the total feeding is 1.3;

[0064] S2, after the reaction in the potassium sulfate first-stage reactor 14 is completed, the reaction is settled for 20 minutes, and the crude potassium sulfate slurry and the primary filtrate are obtained by separation and filtration by the first-stage reaction centrifuge 13, the primary filtrate enters the nitrogen-potassium solution buffer tank 8, the primary filtrate has the following ion percentage concentrations (in % w / v): K + 2.1-4.5%, NH4 +8.5-11.7%, SO4 2- 7.0-12.5%, Cl - 12.0-16.0%; the crude potassium sulfate slurry enters the potassium sulfate two-stage reactor 12, and KCl solution is added to the potassium sulfate two-stage reactor 12, the potassium sulfate two-stage reactor 12 mainly uses KCl solution to wash and remove residual chlorine ions in the crude potassium sulfate slurry and improve the conversion rate of K+, the KCl solution is prepared by sending potassium chloride 15 into the purification liquid tank 7, the concentration of the KCl solution is 17% (molar concentration), the KCl solution is sent to the potassium sulfate two-stage reactor 12 by the purification liquid pump 6, the amount of KCl solution is 15% of the liquid volume in the first reaction, after fully stirring at a constant temperature of 80-100°C for 30 minutes, and settling for 20 minutes;

[0065] S3, after washing, enter the two-stage reaction centrifuge 11 for filtration to obtain refined potassium sulfate product and secondary filtrate, the refined potassium sulfate enters the potassium sulfate drying system 19 and is dried by the fluidized bed to obtain potassium sulfate finished product 20, the refined potassium sulfate product meets the GB / T 20406-2017 agricultural potassium sulfate first-class product: K2O≥50%, Cl - ≤2%, the product contains 70-80% of material with crystal particles greater than 0.15mm, to ensure stable product quality;

[0066] S4, then the secondary filtrate enters the mother liquor tank 5, the secondary filtrate contains ions with a percentage concentration of (in % w / v): K + 7.0-8.5%, NH4 + 6.5-8.7%, SO4 2- 2.0-3.5%, Cl - 18.0-21.0%; the secondary filtrate in the mother liquor tank 5 is sent to the potassium sulfate one-stage reactor 14 by the mother liquor pump 4, and is used as a one-stage reaction conversion raw material for recycling;

[0067] S5, the liquid in the nitrogen-potassium solution buffer tank 8 is sent to the energy-saving evaporation system 16 by the nitrogen-potassium solution pump 9, and after evaporation and crystallization, it enters the nitrogen-potassium fertilizer separation and drying system 17, and after solid-liquid separation by the centrifuge of the nitrogen-potassium fertilizer separation and drying system 17, it enters the fluidized bed drying to obtain nitrogen-potassium fertilizer finished product 18 (total nutrient element content≥35%, meeting the binary high-chlorine blended fertilizer GB / T 21633 standard).

[0068] In the above embodiments, the exhaust evaporation mother liquor generated by the energy-saving evaporation system 16 is sent to the nitrogen-potassium solution buffer tank 8 for recycling, when the liquid level in the nitrogen-potassium solution buffer tank 8 exceeds a certain level, it is transported to the mother liquor tank 5 through the overflow pipe 22 to build a mother liquor closed-loop system, and the residual K +Reintroducing potassium sulfate reaction system, improving K + Utilization rate of high quality; maintaining the concentration gradient of SO4 2- and Cl - in the reaction system, effectively inhibiting the reverse reaction; by controlling the direction of ion migration, K+ in the system migrates to the potassium sulfate system, and Cl - migrates to the nitrogen and potassium fertilizer system.

[0069] Through the above examples, the invention is purified by two-stage reaction, and potassium sulfate products with a mass percentage of potassium oxide of more than 50% are prepared under normal temperature conditions (without heating equipment), which meets the standard of first-grade potassium sulfate products; by controlling the conversion rate of K + in the reaction process, part of K + enters the ammonium chloride system to directly generate nitrogen and potassium high-chlorine binary blended fertilizer (total nutrient content ≥ 35%) that meets the GB / T 21633 standard, replacing traditional ammonium chloride products, simplifying the process and increasing the added value, and the total conversion rate of K + in the process is 85%, without the need for adding catalysts.

[0070] In the description of the above examples, some components and their specific structural details that are not directly related to the core innovative points of the invention are omitted in order to make the specification concise and clear. These omitted parts belong to the existing technical field, and for those skilled in the art, they can design and manufacture these parts according to their own professional knowledge and existing technical materials. Therefore, detailed elaboration is not required here.

[0071] The embodiments of the invention are described in detail above in combination with the drawings, but the invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, replacements and variations of these embodiments can be made without departing from the principles and spirits of the invention, and still fall within the protection scope of the invention.

Claims

1. An apparatus for flue gas desulfurization to produce potassium sulfate and nitrogen-potassium fertilizer, comprising an ammonium sulfate buffer tank (2), a mother liquor tank (5), a nitrogen-potassium solution buffer tank (8), an energy-saving evaporation system (16), a nitrogen-potassium fertilizer separation and drying system (17), and a potassium sulfate drying system (19), characterized in that: The ammonium sulfate buffer tank (2) is connected to a potassium sulfate stage 1 reactor (14) via an ammonium sulfate liquid pump (3). The outlet of the potassium sulfate stage 1 reactor (14) is connected to a stage 1 reaction centrifuge (13). The filtrate outlet of the stage 1 reaction centrifuge (13) is connected to a nitrogen-potassium solution buffer tank (8), and the outlet is connected to a potassium sulfate stage 2 reactor (12). The outlet of the potassium sulfate stage 2 reactor (12) is connected to a stage 2 reaction centrifuge (11). The outlet of the two-stage reaction centrifuge (11) is connected to the potassium sulfate drying system (19), and the filtrate outlet is connected to the mother liquor tank (5); the mother liquor tank (5) is connected to the inlet of the potassium sulfate first-stage reactor (14) through the ammonium sulfate mother liquor pipe (10), and the ammonium sulfate mother liquor pipe (10) is equipped with a mother liquor pump (4). The discharge port of the energy-saving evaporation system (16) is connected to the inlet of the nitrogen and potassium fertilizer separation and drying system (17), and the liquid discharge port of the energy-saving evaporation system (16) is connected to the mother liquor tank (5). The nitrogen and potassium outlet of the nitrogen and potassium fertilizer separation and drying system (17) is connected to the inlet of the nitrogen and potassium solution buffer tank (8); The nitrogen-potassium solution buffer tank (8) is connected to the inlet of the energy-saving evaporation system (16) via a nitrogen-potassium solution pump (9).

2. The apparatus for flue gas desulfurization to produce potassium sulfate and nitrogen-potassium fertilizer according to claim 1, characterized in that: The nitrogen-potassium solution buffer tank (8) is equipped with an overflow pipe (22) connected to the mother liquor tank (5). When the liquid level in the nitrogen-potassium solution buffer tank (8) exceeds a certain level, it is transported to the mother liquor tank (5) through the overflow pipe (22) to form a closed-loop circulation system for the mother liquor. The residual potassium in the solution in the nitrogen-potassium solution buffer tank (8) is removed through material circulation. + Reintroducing potassium sulfate into the reaction system increases K + High-quality utilization rate; maintaining SO4 levels in the reaction system 2- With Cl - The concentration gradient effectively suppresses the reverse reaction; by controlling the direction of ion migration, K+ in the system migrates to the potassium sulfate system, and Cl... - Migrate to the nitrogen and potassium fertilizer system.

3. The apparatus for flue gas desulfurization to produce potassium sulfate and nitrogen-potassium fertilizer according to claim 1, characterized in that: It also includes a purification tank (7), the outlet of which is connected to the inlet of a potassium sulfate two-stage reactor (12) via a purification pump (6), the overflow port of the potassium sulfate two-stage reactor (12) is connected to the purification tank (7), and a water supply pipe (21) is provided on the purification tank (7).

4. The apparatus for flue gas desulfurization to produce potassium sulfate and nitrogen-potassium fertilizer according to claim 1, characterized in that: The device can simultaneously produce potassium sulfate and nitrogen-potassium-chlorine binary blended fertilizer. After the crude potassium sulfate is generated, it enters the potassium sulfate two-stage reactor (12) for refining. The nitrogen-potassium-chlorine binary blended fertilizer liquid can be transported to the energy-saving evaporation system (16) through the nitrogen-potassium solution buffer tank (8), and then directly produces nitrogen-potassium fertilizer product (18) after solid-liquid separation and drying treatment.

5. The apparatus for flue gas desulfurization to produce potassium sulfate and nitrogen-potassium fertilizer according to claim 1, characterized in that: The potassium sulfate stage reactor (14) is a stirred tank reactor.

6. The apparatus for flue gas desulfurization to produce potassium sulfate and nitrogen-potassium fertilizer according to claim 1, characterized in that: The potassium sulfate two-stage reactor (12) is a stirred tank reactor.

7. A method for producing potassium sulfate and nitrogen-potassium fertilizer through flue gas desulfurization, characterized in that... The method, employing the apparatus as described in any one of claims 1-6, is specifically as follows: S1. First, the ammonium sulfate solution (1) generated by flue gas desulfurization is sent into the ammonium sulfate buffer tank (2). Then, the ammonium sulfate solution is sent into the potassium sulfate stage reactor (14) by the ammonium sulfate liquid pump (3). Potassium chloride (15) is fed in at a mass ratio of 0.9 to 1.3 with the mass ratio of the ammonium sulfate solute in the solution. The temperature in the potassium sulfate stage reactor (14) is controlled at 25 to 100°C. The reaction is stirred at this temperature for 20 to 40 minutes. The total water volume to the total solid mass of the feed is 0.9 to 1.

6. S2. After the reaction in the potassium sulfate stage 1 reactor (14) is completed, the mixture settles for 10-20 minutes and is separated and filtered by the stage 1 reaction centrifuge (13) to obtain crude potassium sulfate slurry and primary filtrate. The primary filtrate enters the nitrogen-potassium solution buffer tank (8), and the crude potassium sulfate slurry enters the potassium sulfate stage 2 reactor (12). KCl solution is added to the potassium sulfate stage 2 reactor (12). The concentration of KCl solution is 5-20%. KCl solution is sent to the potassium sulfate stage 2 reactor (12) through the purification liquid pump (6). The amount of KCl solution used is 10-20% of the liquid volume during the primary reaction. After stirring and reacting at 25-100℃ for 30-60 minutes, the mixture settles for 10-20 minutes. S3. After washing, the product is filtered in a two-stage reaction centrifuge (11) to obtain refined potassium sulfate product and secondary filtrate. The refined potassium sulfate is then dried in a fluidized bed in a potassium sulfate drying system (19) to obtain finished potassium sulfate product (20). S4. Subsequently, the secondary filtrate enters the mother liquor tank (5). The secondary filtrate in the mother liquor tank (5) is sent to the potassium sulfate stage reactor (14) by the mother liquor pump (4) and recycled as a raw material for stage reaction conversion. S5. The liquid in the nitrogen-potassium solution buffer tank (8) is sent to the energy-saving evaporation system (16) by the nitrogen-potassium solution pump (9). After evaporation and crystallization, it enters the nitrogen-potassium fertilizer separation and drying system (17). The nitrogen-potassium fertilizer product (18) is obtained through the nitrogen-potassium fertilizer separation and drying system (17). The evaporation mother liquor generated by the energy-saving evaporation system (16) is sent to the nitrogen-potassium solution buffer tank (8) for recycling.

8. The method for producing potassium sulfate and nitrogen-potassium fertilizer from flue gas desulfurization according to claim 7, characterized in that: The density of the ammonium sulfate solution in S1 is 410–420 g / L.

9. The method for producing potassium sulfate and nitrogen-potassium fertilizer from flue gas desulfurization according to claim 7, characterized in that: The percentage concentration of each ion in the primary filtrate is: K + 2.1–4.5%, NH4 + 8.5–11.7%, SO4 2- 7.0–12.5%, Cl - 12.0%–16.0%.

10. The method for producing potassium sulfate and nitrogen-potassium fertilizer from flue gas desulfurization according to claim 7, characterized in that: The percentage concentration of each ion in the secondary filtrate is: K + 7.0–8.5%, NH4 + 6.5-8.7%, SO4 2- 2.0–3.5%, Cl - 18.0%–21.0%.

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