Method for preparing ammonium sulfate from ammonia-containing waste gas

Abstract

The invention relates to a method for preparing ammonium sulfate from ammonia-containing waste gas, which comprises the following steps: S1, ammonia gas or ammonia-containing waste gas enters from an ammonia-containing waste gas inlet of a reactor, then collides with the liquid level of a crystalline region, rebounds and is dispersed, and then rises to the top of the reactor; s2, in the rising process, countercurrent and sulfuric acid-containing circulating slurry sprayed by an absorption spraying layer in the absorption area are subjected to absorption and reaction, and ammonium sulfate is generated; s3, demisting the tail gas absorbed by the circulating slurry containing sulfuric acid, and discharging the tail gas from the top of the reactor; meanwhile, the ammonium sulfate slurry at the bottom of the crystallization area is sequentially conveyed to a cyclone and a centrifugal machine through a crystallization pump to be concentrated and separated, and an ammonium sulfate crystal wet material product is obtained. The method improves the crystallization blockage resistance of equipment, is high in absorption efficiency, utilizes reaction heat as much as possible to reduce external heat, is energy-saving and environment-friendly, and is stable and reliable in technology.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical environmental protection, and particularly to a method for preparing ammonium sulfate from ammonia-containing waste gas in the field of wastewater treatment. Background Art

[0002] In the production processes of chemical plants and environmental protection facilities such as synthetic ammonia, synthesis of gold ore dressing agents, sour water stripping, and phenol-ammonia recovery, ammonia gas or ammonia-containing waste gas with different concentrations will be generated. The composition is complex, the concentration is high, and the difference is large. It is difficult to recover ammonia gas or ammonia-containing waste gas into valuable qualified products. Moreover, it is even more difficult to achieve the up-to-standard discharge of the tail gas after treating high-concentration ammonia gas or ammonia-containing waste gas. Due to the malodorous characteristics of ammonia, once the discharge exceeds the standard, it will cause serious environmental protection accidents. And the added value of ammonia is relatively high. Therefore, realizing the treatment and resource recovery of ammonia-containing waste gas has significant economic value and environmental protection value.

[0003] A large number of studies have been carried out in China on the purification and recovery of ammonia gas or ammonia-containing waste gas. The existing technologies mainly include physical absorption, chemical absorption, catalytic decomposition, catalytic aerobic decomposition, and biodegradation. However, due to the high concentration of ammonia gas or ammonia-containing waste gas with a concentration ≥ 1% v, the treatment process spans two fields of chemical engineering and environmental protection. For example, physical absorption and chemical absorption have long treatment processes, it is difficult to achieve water balance, high corrosivity, and it is difficult for the tail gas to meet the standard. Catalytic decomposition and catalytic aerobic decomposition have high operating temperatures, large consumption of fuel gas, and high treatment costs. Biodegradation is difficult to meet the treatment requirements of high-concentration ammonia-containing waste gas and often requires a combination of multiple processes, resulting in problems such as long process chains, large investments, and high operating costs.

[0004] The resource recovery of ammonia gas or ammonia-containing waste gas can be recovered in the form of liquid ammonia, ammonia water, ammonium salts, etc. Due to the absorption equilibrium limitation, ammonia gas or ammonia-containing waste gas is directly absorbed by water to generate ammonia water, and the concentration of ammonia water is often low and difficult to be directly utilized. Generally, processes such as rectification need to be supported for further concentration or purification to recover high-concentration ammonia water or liquid ammonia. The process is complex, the treatment cost is relatively high, and the ammonia concentration in the tail gas after absorption is still high and difficult to meet the discharge standard. Recycling ammonia gas or ammonia-containing waste gas into ammonium salts, such as ammonium sulfate, ammonium phosphate, ammonium chloride, ammonium carbonate, etc., has the advantages of short process, complete absorption, high product purity, etc., and the products can be directly applied to agricultural fertilizers.

[0005] Chinese patent document CNCN210057881U discloses an ammonium sulfate preparation device for ammonia stripping and absorption of ammonia-containing waste gas. Its structure includes a sulfuric acid diluter, a sulfuric acid storage tank, a sulfuric acid delivery pump, a first mixer, a second mixer, a bottom circulation pump, a top circulation pump, a bottom cooler, a top cooler, an ammonia absorption tower, a pH meter, a multi-effect evaporation and crystallization system, etc. This technical solution mainly aims at the absorption of ammonia-containing waste gas after ammonia stripping of wastewater to prepare ammonium sulfate. Since the ammonia concentration is low, it is difficult to maintain the water balance after using the sulfuric acid diluter, and the resulting dilute ammonium sulfate solution completely relies on the multi-effect evaporation and crystallization system to achieve concentration and crystallization. Therefore, this patent has large energy losses and high energy consumption, and is not economically conducive to long-term continuous operation.

[0006] Chinese patent document CN113262616A discloses a resource recovery and treatment process for ammonia-containing tail gas, which includes the following steps: S1. Pressure stabilization treatment: The ammonia-containing tail gas generated during the incineration process of the kiln is transported through an exhaust gas collection pipeline to a pressure stabilization device for pressure stabilization treatment for a period of time; S2. Spray absorption treatment: The exhaust gas after pressure stabilization treatment in S1 is introduced into a spray absorption device for treatment, and the ammonia in the exhaust gas is transferred to the spray liquid and recycled. In this technical solution, the pressure stabilization treatment only plays a role of buffering and storage. The main equipment is a gas buffer tank, which is provided with complex structures such as a filter screen, a cleaning plate, a collection box, a suction pump, a dust sticking plate, and a compression spring to deal with blockage by impurity dust. The operation and maintenance are difficult, and the effect of removing impurity dust is not significant; the main equipment for spray absorption treatment is a first-stage spray plate tower with strong anti-blocking performance, a second-stage spray packing tower with high absorption efficiency, and a demisting tower. Although this technical solution has considered the crystallization blockage situation of the first-stage and second-stage spray towers, the spray circulating liquid still uses saturated ammonium sulfate solution, which inevitably contains crystals, and the concentration of the slurry and solution is not graded, so the risk of crystallization blockage is large, and it is difficult to guarantee the absorption effect of ammonia. This patent mainly treats waste gas containing NH3 5-7%, CO2 5-8%, tungsten oxide dust, etc. generated during the incineration process of tungsten powder smelting kilns, and has greater limitations in treating higher-concentration ammonia or ammonia-containing waste gas.

[0007] Chinese patent document CN215916954U discloses a system for absorbing ammonia gas and preparing ammonium sulfate. The system includes: a first stripping tank and a second stripping tank; the water replenishment inlet of the first stripping tank is connected to the liquid phase outlet of a heat exchanger, the liquid phase inlet of the first stripping tank is connected to the liquid phase outlet of a first hydraulic ejector, the liquid phase outlet of the first stripping tank is connected to the liquid phase inlet of a first circulation pump, the sulfuric acid outlet of the first stripping tank is connected to the liquid phase inlet of the second stripping tank, and the gas phase outlet of the first stripping tank is connected to an external exhaust pipeline. This technical solution uses sulfuric acid as an absorbent, and adopts two-stage hydraulic ejectors to absorb ammonia gas and react it into ammonium sulfate, generating a crystallization slurry. However, this system does not consider the classification of the crystallization slurry and solution concentration, resulting in a reduced absorption efficiency, making it difficult to achieve zero emission of ammonia waste gas, and even difficult to meet the emission standards for high-concentration ammonia-containing waste gas; it does not consider the impurity situation in the ammonia gas, exacerbating the system corrosion and blockage, and it is also difficult to ensure the quality of ammonium sulfate; sulfuric acid is only added to the first stripping tank, making it difficult to control the pH and operate the first stripping tank and the second stripping tank; the bottoms of the first stripping tank and the second stripping tank adopt an oval head design, with dead zones in the process flow, exacerbating the risk of crystallization blockage and making it difficult to meet the requirements of long-term stable operation.

[0008] Therefore, it is necessary to propose a method for preparing ammonium sulfate from ammonia-containing waste gas, which has a fast acid-base neutralization reaction rate, complete reaction, high absorption efficiency, low energy consumption, and stable and reliable technology. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a method for preparing ammonium sulfate from ammonia-containing waste gas, which uses a vertical spray reactor, and after reaching supersaturation, it precipitates in the form of ammonium sulfate crystals, and the ammonium sulfate crystals are then sent to a hydrocyclone and a centrifuge for separation by a crystallization pump to obtain a wet ammonium sulfate crystal product.

[0010] To solve the above technical solution, the technical solution of the present invention is: the method for preparing ammonium sulfate from ammonia-containing waste gas specifically includes the following steps:

[0011] S1: Ammonia gas or ammonia-containing waste gas enters from the ammonia-containing waste gas inlet of the reactor, and then collides, rebounds and disperses with the liquid surface in the crystallization zone, and rises to the top of the reactor.

[0012] S2: During the rising process, it countercurrently absorbs and reacts with the circulating slurry containing sulfuric acid sprayed by the absorption spray layer in the absorption zone to generate ammonium sulfate.

[0013] S3: The tail gas absorbed by the circulating slurry containing sulfuric acid is discharged through the top of the reactor after demisting; at the same time, the ammonium sulfate slurry at the bottom of the crystallization zone is successively sent to a hydrocyclone and a centrifuge by a crystallization pump for concentration and separation to obtain a wet ammonium sulfate crystal product.

[0014] With the above technical solution, high-concentration ammonia gas or ammonia-containing waste gas continuously enters the reactor, and a cyclic absorption reaction occurs in the reactor to generate ammonium sulfate. After reaching supersaturation, it precipitates in the form of ammonium sulfate crystals. The ammonium sulfate crystals are then sent to a hydrocyclone and a centrifuge for concentration and separation by a crystallization pump to obtain a wet ammonium sulfate crystal product. The wet product can be sold directly, or sold after further drying and packaging. The present invention adopts a vertical structure spray reactor, which is respectively provided with an absorption zone and a crystallization zone inside. The absorption zone can be provided with multiple absorption spray layers to ensure efficient absorption of high-concentration ammonia gas. At the same time, the solid content in the absorption zone is low and it is not easy to be blocked. The crystallization zone adopts supersaturation control measures, with good crystal quality, uniform particle size, large particles, easy to concentrate and separate. The obtained wet ammonium sulfate crystal product can be sold directly, or sold after further drying and packaging.

[0015] Preferably, the reactor includes an absorption zone and a crystallization zone from top to bottom, and the crystallization zone is communicated with the absorption zone; a tail gas outlet is provided at the top of the absorption zone, and a slurry outlet is provided at the bottom of the crystallization zone; the ammonia-containing waste gas inlet is inclined downward relative to the reactor, and the downward inclination angle with the reactor is 5-30°. The downward inclination angle of the ammonia-containing waste gas inlet relative to the reactor is preferably 15-20°. The reactor is respectively provided with an absorption zone and a crystallization zone. The slurry in the absorption zone has a low solid content and is not easy to be blocked. The crystallization zone adopts supersaturation control measures, with good crystal quality, uniform particle size, large particles, easy to concentrate and separate.

[0016] Preferably, according to the different sources and impurity components of ammonia gas or ammonia-containing waste gas, a pretreatment device is provided at the ammonia-containing waste gas inlet of the reactor. The pretreatment device includes but is not limited to dust removal, pre-washing, heating or cooling, etc., to meet the normal operation of the system and the quality of ammonium sulfate products.

[0017] Preferably, in step S2, the circulating slurry with a solid content lower than 3% (preferably lower than 1%) in the upper part of the crystallization zone overflows to the circulation tank and is sent to the multiple absorption spray layers in the absorption zone for spray absorption by at least one reaction circulation pump, and the solid content of the slurry in the absorption zone is ≤3%. The solid content of the slurry in the absorption zone is ≤3%, preferably the solid content is ≤1%. Such a low solid content reduces the risk of blockage and the wear on the pipeline nozzles. The crystallization zone adopts supersaturation control measures, optimizes the circulating slurry volume and the elutriation liquid volume, controls the slurry flow rate, and the supersaturation concentration control fluctuates little, so as to achieve good crystal quality, uniform particle size, large particles, and easy to concentrate and separate.

[0018] Preferably, in step S2, the circulating slurry is extracted from the circulation tank, pressurized by a elutriation pump and sent to the bottom of the crystallization zone, and elutriated through an elutriation spray layer and shunted according to the crystal grain size of ammonium sulfate.

[0019] Preferably, at least one mixer is provided on the main pipe at the outlet of the reaction circulation pump. The mixer is communicated with the circulating liquid inlet on the reactor, and the circulating liquid inlet is connected to the absorption spray layer. The mixer is used to fully mix the added sulfuric acid with the circulating slurry.

[0020] Preferably, the circulation tank is connected to the elutriation pump to send the circulating slurry with a solid content of less than 1% to the bottom of the crystallization zone to wash the bottom area of the crystallization zone, thereby maintaining the fluidity of the crystals, removing the fine crystal nuclei on the crystal surface, and forming larger and more regular crystals.

[0021] Preferably, a stirrer is provided in the circulation tank. The overflowing circulating slurry in the upper part of the crystallization zone is mixed with the hydrocyclone mother liquor and the centrifuge mother liquor, and then sent to the mixer through the reaction circulation pump. After being fully mixed with sulfuric acid, it is sent to the absorption spray layer. The concentration of the sulfuric acid is ≥60%. The crystal slurry outlet is connected to the crystallization pump, and the ratio of the flow rate of the elutriation pump to the flow rate of the crystallization pump is 1 to 3. The ratio of the flow rate of the elutriation pump to the flow rate of the crystallization pump is preferably 2 to 3. Fresh sulfuric acid or waste sulfuric acid can be used for sulfuric acid. To achieve the water balance in the reaction system and reduce or avoid the consumption of external energy, it is necessary to reasonably control the sulfuric acid concentration ≥60%, preferably concentrated sulfuric acid.

[0022] Preferably, the absorption zone is provided with 1 to 6 layers of absorption spray layers, and the top of the reactor is provided with 1 to 2 layers of demisters.

[0023] Preferably, a pH meter is provided in the circulation tank, and the pH of the circulating slurry in the circulation tank is controlled at 4.5 to 5.5.

[0024] Preferably, the elutriation spray layer is provided with annular tangential elutriation nozzles. The elutriation nozzles are evenly distributed and the elutriation nozzles are obliquely downward towards the center of the crystallization zone. The solid content of the slurry in the crystallization zone is controlled at 5 to 50%; preferably 10 to 25%. A pH meter is provided in the circulation tank, and the pH of the circulating slurry in the circulation tank is controlled at 4.5 to 5.5. By evenly distributing the elutriation circulating slurry through the elutriation nozzles, the ammonium sulfate is thus shunted according to the crystal size. The larger particles of ammonium sulfate precipitate to the bottom of the crystallization zone, and the smaller particles of ammonium sulfate return to the upper and middle parts of the crystallization zone to continue to grow by crystallization.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: The method for preparing ammonium sulfate from ammonia-containing waste gas defines process control indicators and control methods, and has the advantages of fast acid-base neutralization reaction rate, complete reaction, high quality of ammonium sulfate product, and less solid waste generation. The reactor adopts a vertical structure, with an absorption zone arranged in the upper part and a crystallization zone arranged in the lower part. The slurry solid content gradient control is adopted, which improves the anti-crystallization and blockage performance of the equipment, has high absorption efficiency, and uses the reaction heat as much as possible to reduce the use of external heat, saving energy and protecting the environment. The technology is stable and reliable, with low investment and operation and maintenance costs. The higher the ammonia concentration in ammonia or ammonia-containing waste gas, the higher the recovery value. The ammonia concentration in ammonia or ammonia-containing waste gas is ≥1% v, and the ammonia concentration in high-concentration ammonia or ammonia-containing waste gas can be as high as 100% v. The ammonia recovery rate can reach more than 98%, and even can reach more than 99.9%. The treated tail gas can be discharged according to local environmental protection requirements or further treated in the absorption tower and then discharged. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The technical solution of the present invention will be further described below with reference to the drawings:

[0027] Figure 1 is a schematic structural diagram of the method for preparing ammonium sulfate from ammonia-containing waste gas of the present invention;

[0028] Wherein: 1 - crystallization zone; 2 - reactor; 3 - absorption zone; 4 - elutriation pump; 5 - circulation tank; 6 - reaction circulation pump; 7 - mixer; 8 - crystallization pump; 9 - hydrocyclone; 10 - centrifuge; 11 - absorption spray layer; 12 - elutriation spray layer; 101 - ammonia-containing waste gas inlet; 102 - tail gas outlet; 103 - sulfuric acid inlet; 104 - wet ammonium sulfate crystal outlet. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to the drawings and embodiments. The embodiments are only used to explain the present invention and do not limit the protection scope of the present invention.

[0030] Embodiment: As Figure 1 shown, the method for preparing ammonium sulfate from ammonia-containing waste gas specifically includes the following steps:

[0031] S1: Ammonia or ammonia-containing waste gas enters from the ammonia-containing waste gas inlet 101 of the reactor 2, and then collides with and rebounds from the liquid surface of the crystallization zone 1 and disperses, and then rises to the top of the reactor 2. The reactor 2 includes an absorption zone 3 and a crystallization zone 1 from top to bottom. The crystallization zone 1 and the absorption zone 3 are connected through a reduced-diameter section. The top of the absorption zone 3 is provided with a tail gas outlet 102, and the bottom of the crystallization zone 1 is provided with a crystal slurry outlet. The ammonia-containing waste gas inlet 101 is provided on the absorption zone 3. The ammonia-containing waste gas inlet 101 is inclined downward relative to the reactor 2, and the downward inclination angle with the reactor 2 is 5-30°; preferably 15-20°. According to the different sources and impurity components of ammonia or ammonia-containing waste gas, a pretreatment device can be set up. The pretreatment device includes but is not limited to dust removal, pre-washing, heating or cooling, etc., to meet the normal operation of the system and the quality of ammonium sulfate products.

[0032] S2: During the rising process, it countercurrently absorbs and reacts with the sulfuric acid-containing circulating slurry sprayed by the absorption spray layer 11 in the absorption zone 3 to generate ammonium sulfate. In step S2, the circulating slurry with a solid content lower than 3% in the upper part of the crystallization zone 1 overflows to the circulation tank 5 and is sent to the multi-layer absorption spray layer in the absorption zone by at least one reaction circulation pump 6 for spray absorption. The slurry in the absorption zone 3 has a solid content ≤ 3%. In step S2, a part of the circulating slurry is extracted from the circulation tank 5, pressurized by the elutriation pump 4 and sent to the bottom of the crystallization zone 1, and is elutriated through the elutriation spray layer 12 and is shunted according to the crystal size of ammonium sulfate. The elutriation spray layer 12 is provided with annular tangential elutriation nozzles, and the elutriation nozzles are evenly distributed and the elutriation nozzles are obliquely downward towards the center of the crystallization zone. The circulating slurry for elutriation is evenly distributed through the elutriation nozzles. Larger particles of ammonium sulfate precipitate to the bottom of the crystallization zone 1, and smaller particles of ammonium sulfate return to the upper and middle parts of the crystallization zone 1 to continue to grow by crystallization.

[0033] At least one mixer 7 is provided on the main pipe at the outlet of the reaction circulation pump 6. The mixer 7 is provided with a sulfuric acid inlet 102, and the mixer 7 is connected to the circulating liquid inlet on the reactor 2, and the circulating liquid inlet is connected to the absorption spray layer 11. The mixer 7 is provided with a sulfuric acid inlet 103. The mixer 7 is used to fully mix the added sulfuric acid with the circulating slurry. The circulation tank 5 is connected to the elutriation pump 4 to send the circulating slurry with a solid content lower than 1% to the bottom of the crystallization zone 1 to scour the bottom area of the crystallization zone 1.

[0034] A stirrer is arranged in the circulation tank 5. The overflow circulating slurry in the upper part of the crystallization zone 1 is mixed with the cyclone mother liquor and the centrifugal mother liquor, and is sent to the mixer 7 through the reaction circulating pump 6. After being fully mixed with sulfuric acid, it is sent to the absorption spray layer 11; the concentration of the sulfuric acid is ≥60%; the crystal slurry outlet is connected to the crystallization pump 8, and the flow ratio of the elutriation pump 4 to the crystallization pump 8 is 1-3; the absorption zone 3 is provided with 1-6 layers of absorption spray layers 11, and the top of the reactor 2 is provided with 1-2 layers of demisters; the circulation tank 5 is provided with a pH meter, and the pH of the circulating slurry in the circulation tank 5 is controlled to be 4.5-5.5; the solid content of the slurry in the crystallization zone is controlled to be 5-50%; the circulation tank 5 is provided with a pH meter, and the pH of the circulating slurry in the circulation tank 5 is controlled to be 4.5-5.5;

[0035] S3: The tail gas absorbed by the circulating slurry containing sulfuric acid is discharged through the top of the reactor 2 after demisting; at the same time, the ammonium sulfate slurry at the bottom of the crystallization zone 1 is successively sent to the hydrocyclone 9 and the centrifuge 10 through the crystallization pump 8 for concentration and separation, and the obtained wet ammonium sulfate crystal product is discharged through the wet ammonium sulfate crystal outlet 104. The wet product can be sold directly, or sold after further drying and packaging.

[0036] The device used in the method for preparing ammonium sulfate from ammonia-containing waste gas includes a reactor 2, a elutriation pump 4, a circulation tank 5, a reaction circulation pump 6, a mixer 7, a crystallization pump 8, a hydrocyclone 9 and a centrifuge 10. The reactor 2 includes an absorption zone 3 and a crystallization zone 1 from top to bottom. The crystallization zone 1 and the absorption zone 3 are connected through a reduced-diameter section. The top of the absorption zone 3 is provided with a tail gas outlet 102, and the bottom of the crystallization zone 1 is provided with a crystal slurry outlet. The absorption zone 3 is provided with an ammonia-containing waste gas inlet 101, and the ammonia-containing waste gas inlet 101 is inclined downward relative to the reactor 2, and the downward inclination angle with the reactor 2 is 5-30°. The upper part of the crystallization zone 1 is provided with a circulating slurry outlet, and the circulating slurry outlet is connected to the circulation tank 5. The circulation tank 5 is respectively connected to the elutriation pump and the reaction circulation pump. The reaction circulation pump is connected to the mixer, and the mixer 7 is then connected to the circulating slurry inlet of the absorption zone. The circulating liquid inlet is connected to the absorption spray layer 11. The mixer 7 is provided with a sulfuric acid inlet. The mixer 7 is used to fully mix the added sulfuric acid with the circulating slurry. The mixer 7 is provided with a sulfuric acid inlet. The top of the reactor 2 is provided with 1-2 layers of demisters. The circulation tank 5 is provided with a pH meter, and the pH of the circulating slurry in the circulation tank 5 is controlled at 4.5-5.5. The solid content of the slurry in the crystallization zone is controlled at 5-50%. The circulation tank 5 is provided with a pH meter, and the pH of the circulating slurry in the circulation tank 5 is controlled at 4.5-5.5. The crystal slurry outlet is connected to the crystallization pump 8, the crystallization pump 8 is sequentially connected to the hydrocyclone 9 and the centrifuge 10, and the centrifuge 10 is provided with a wet ammonium sulfate crystal outlet 104. The flow rate ratio of the elutriation pump 4 to the crystallization pump 8 is 1-3. The absorption zone 3 is provided with 1-6 layers of absorption spray layers 11, Specific Example 1:

[0038] Using the above method for preparing ammonium sulfate from ammonia to treat the ammonia-containing tail gas of a synthetic ammonia plant, with an ammonia content of 1-3.5% v, and other components mainly being methane, hydrogen, and nitrogen. The reactor 2 adopts a vertical structure, with an absorption zone 3 set at the upper part and a crystallization zone 1 set at the lower part. The absorption zone 3 is provided with 3 layers of absorption spray layers 11. A two-stage wire mesh demister is set at the top of the reactor 2. One circulating tank 5 with stirring and one reaction circulating pump 6 are set. The circulating slurry is supplied to the 3 layers of absorption spray layers 11 by the main pipe system. The reaction raw material is concentrated sulfuric acid with a concentration of 98%, which is added to the circulating slurry through a mixer 7 arranged on the outlet main pipe of the reaction circulating pump 6. One elutriation pump 4 and one crystallization pump 8 are set. The flow rate ratio of the elutriation pump 4 to the crystallization pump 8 is 1. The overflow liquid and the hydrocyclone centrifugal mother liquor at the upper part of the crystallization zone 1 of the reactor 2 are all collected into the circulating tank 5. A pH meter is set on the circulating tank 5 to control the pH of the circulating absorption slurry at 4.5-5.5. The solid content of ammonium sulfate crystals in the circulating absorption slurry is ≤1%. The reaction temperature is 50-70°C. After the ammonium sulfate crystals are elutriated, they are discharged from the bottom of the reactor 2, and the ammonium sulfate crystal wet material product is obtained through hydrocyclone and centrifugation, which is directly used for the compound fertilizer production of the enterprise. The ammonia recovery rate of this project is 98%-99.5%. When the solid content at the bottom of the crystallization zone 1 reaches 10-25%, it is discharged through the crystallization pump 8. The ammonium sulfate crystals are in good condition and have large particles. The by-product ammonium sulfate product meets the requirements of Type I indicators in Table 1 of "Fertilizer Grade Ammonium Sulfate GB / T 535-2020" (except for moisture). The treated tail gas is further washed by the tail gas scrubber and then discharged, with significant economic and environmental benefits. Specific Example 2:

[0040] Using the above method for preparing ammonium sulfate from ammonia to treat the high-concentration ammonia-containing waste gas from the fine chemical section of a project, with an ammonia content of 27-30% v, a water content of 15-20% v, and the rest being CO2 and air, and the temperature is about 60-80°C. There are few impurity components in the high-concentration ammonia-containing waste gas of this project. The absorption zone 3 of the reactor 2 is provided with 6 layers of absorption spray layers 11. Two reaction circulating pumps 6 are set, with each corresponding to 3 layers of absorption spray layers 11. A mixer 7 is set on the outlet main pipe of the reaction circulating pump 6 corresponding to the lower 3 layers of absorption spray layers 11, for adding 98% concentrated sulfuric acid to the circulating slurry, controlling the pH of the circulating slurry in the circulating tank 5 at 4.5-5.5, the solid content in the circulating slurry is ≤1%, the reaction temperature is 70-80°C, and two-layer roof-type demisters are set at the top of the reactor. One elutriation pump 4 and one crystallization pump 8 are set. The flow rate ratio of the elutriation pump 4 to the crystallization pump 8 is 3. The solid content in the slurry at the bottom of the crystallization zone 1 is 10-25%, which is discharged through the crystallization pump 8, and the ammonium sulfate product is recovered after hydrocyclone, centrifugation, drying, and packaging. The ammonia recovery rate of this project is 99.5%-99.9%. The treated tail gas meets the local environmental protection requirements and is directly discharged. The by-product ammonium sulfate product meets the requirements of Type I indicators in Table 1 of "Fertilizer Grade Ammonium Sulfate GB / T 535-2020" and is directly sold. Specific Embodiment 3:

[0042] Apply the above method for treating ammonia to prepare ammonium sulfate to treat the ammonia-containing waste gas from the calcination section of a tungsten powder smelting project. The ammonia content is 1-8% v, the water content is ~10% v, and the rest are tungsten oxide dust, CO2, N2, O2, etc. The temperature is about 90-110°C. First, pre-wash the ammonia-containing waste gas. The pre-wash tower uses an alkali solution with a concentration of ~45% for washing. After cooling and dust removal of the ammonia-containing tail gas, it enters the ammonium sulfate preparation unit. Reactor 2 adopts a vertical structure spray reactor, with an absorption zone 3 set in the upper part and a crystallization zone 1 set in the lower part. The absorption zone is provided with 5 layers of absorption spray layers. A 2-stage wire mesh demister is set on the top of reactor 2. One stirring-type circulation tank and two reaction circulation pumps are set. One corresponds to the lower 3 layers of absorption spray layers 44, and one corresponds to the upper 2 layers of absorption spray layers 11. A mixer 7 is set on the outlet header pipe of the reaction circulation pump 6 corresponding to the lower 3 layers of absorption spray layers to add 98% concentrated sulfuric acid into the circulating slurry. One elutriation pump 4 and one crystallization pump 8 are set. The flow rate ratio of elutriation pump 4 to crystallization pump 8 is 2. The overflow liquid and cyclone centrifugal mother liquid in the upper part of the crystallization zone of the reactor are all collected into the circulation tank 5. A pH meter is set on the circulation tank 5 to control the pH of the circulating absorption slurry at 4.5-5.5. The solid content of ammonium sulfate crystals in the circulating absorption slurry is ≤1.5%. The reaction temperature is 50-70°C. After elutriation, the ammonium sulfate crystals are discharged from the bottom of reactor 2, and wet ammonium sulfate crystal products are obtained through cyclone and centrifugation and are directly sold outside. The ammonia recovery rate of this project is 98%-99.7%. When the solid content at the bottom of the crystallization zone reaches 10-25%, it is discharged through the crystallization pump. The ammonium sulfate crystals are in good condition and have larger particles. The by-product ammonium sulfate product meets the requirements of Type I indicators (except for moisture) in Table 1 of "Ammonium Sulfate for Fertilizer Grade GB / T 535-2020". The treated tail gas is further washed by the tail gas washing tower and then discharged, with significant economic and environmental benefits. Specific Embodiment 4:

[0044] Using the above method for preparing ammonium sulfate from ammonia to treat high-concentration ammonia from an acidic water stripping unit, with an ammonia content of 90-95% v, a water content of 5-10% v, and an impurity content of about 1-3%. The impurities include a small amount of hydrogen sulfide, CO2, etc., and the temperature is about 40-60°C. The reactor adopts a vertical spray reactor 2, with an absorption zone 3 set at the upper part and a crystallization zone 1 set at the lower part. The absorption zone is provided with 6 layers of absorption spray layers. A 2-stage wire mesh demister is set at the top of the reactor 2. One circulating tank 5 with stirring is set, and 2 reaction circulating pumps 6 are set. Each pump corresponds to 3 layers of absorption spray layers 11. A mixer 7 is set on the outlet header pipe of the reaction circulating pump 6 corresponding to the lower 3 layers of absorption spray layers 11 for adding recycled sulfuric acid with a concentration of 60%-70% to the circulating slurry. One elutriation pump 4 and one crystallization pump 8 are set. The flow rate ratio of the elutriation pump 4 to the crystallization pump 8 is 3. The overflow liquid and the hydrocyclone centrifugal mother liquid at the upper part of the crystallization zone 1 of the reactor 2 are all collected into the circulating tank. A pH meter is set on the circulating tank 5 to control the pH of the circulating absorption slurry at 4.5-5.5. The solid content of ammonium sulfate crystals in the circulating absorption slurry is ≤1%. The reaction temperature is 60-80°C. After the ammonium sulfate crystals are elutriated, they are discharged from the bottom of the reactor, and ammonium sulfate crystal wet material products are obtained through hydrocyclone and centrifugation and are directly sold outside. The ammonia recovery rate of this project is 99.5%-99.9% or above. When the solid content at the bottom of the crystallization zone 1 reaches 10-25%, it is discharged through the crystallization pump. The ammonium sulfate crystals are in good condition and have larger particles. The by-product ammonium sulfate product meets the requirements of Type I indicators (except for moisture) in Table 1 of "Fertilizer-grade Ammonium Sulfate GB / T 535-2020". The treated tail gas is further washed by a tail gas scrubber and then discharged, with significant economic benefits.

[0045] The method of the present invention can treat ammonia or ammonia-containing waste gas with an ammonia concentration ≥1% v, and the ammonia absorption efficiency ≥98%. The treated tail gas can be discharged according to local environmental protection requirements or further treated in an absorption tower and then discharged, realizing the resource recovery of high-concentration ammonia or ammonia-containing waste gas into ammonium sulfate, improving the quality of ammonium sulfate products, having a high ammonia recovery rate, solving the problem of blockage in the solid-containing and crystallization systems, and having no waste gas, waste liquid, or waste solid emissions during the treatment process, realizing the long-term stable operation of the device.

[0046] For those of ordinary skill in the art, the specific embodiments only exemplarily describe the present invention. Obviously, the specific implementation of the present invention is not limited by the above methods. As long as various non-substantive improvements are made by adopting the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for preparing ammonium sulfate from ammonia-containing waste gas, characterized in that: The specific steps include: S1: Ammonia or ammonia-containing waste gas enters from the ammonia-containing waste gas inlet of the reactor, then collides with the liquid surface in the crystallization zone, rebounds, and disperses, and then rises to the top of the reactor; S2: During the rising process, it countercurrently absorbs and reacts with the circulating slurry containing sulfuric acid sprayed by the absorption spray layer in the absorption zone to generate ammonium sulfate; S3: The tail gas absorbed by the circulating slurry containing sulfuric acid is discharged through the top of the reactor after demisting; at the same time, the ammonium sulfate slurry at the bottom of the crystallization area is sent to the cyclone and centrifuge in sequence through a crystallization pump for concentration and separation to obtain an ammonium sulfate crystal wet material product.

2. The method for preparing ammonium sulfate from ammonia-containing waste gas according to claim 1, characterized in that: The reactor comprises an absorption zone and a crystallization zone from top to bottom, and the crystallization zone is connected to the absorption zone; a tail gas outlet is provided at the top of the absorption zone, and a slurry outlet is provided at the bottom of the crystallization zone; the ammonia-containing waste gas inlet is tilted downward relative to the reactor, and the downward tilt angle between the inlet and the reactor is 5 to 30 degrees.

3. The method for preparing ammonium sulfate from ammonia-containing waste gas according to claim 1, characterized in that: In step S2, the circulating slurry with a solid content of less than 3% in the upper part of the crystallization zone overflows to the circulation tank, and is pumped to the multi-layer absorption spray layer in the absorption zone for spray absorption through at least one reaction circulation pump, and the solid content of the slurry in the absorption zone is ≤3%.

4. The method for preparing ammonium sulfate from ammonia-containing waste gas according to claim 3, characterized in that: In step S2, circulating slurry is extracted from the circulation tank, pressurized by an elutriation pump and sent to the bottom of the crystallization zone, elutriated through the elutriation spray layer, and diverted according to the grain size of ammonium sulfate.

5. The method for preparing ammonium sulfate from ammonia-containing waste gas according to claim 4, characterized in that: At least one mixer is provided on the main pipe at the outlet of the reaction circulation pump, and the mixer is connected to the circulating liquid inlet on the reactor, and the circulating liquid inlet is connected to the absorption spray layer; the mixer is used to fully mix the added sulfuric acid with the circulating slurry.

6. The method for preparing ammonium sulfate from ammonia-containing waste gas according to claim 4, characterized in that: The circulation tank is connected to the elutriation pump to deliver the circulating slurry with a solid content of less than 1% to the bottom of the crystallization zone to flush the bottom area of ​​the crystallization zone.

7. The method for preparing ammonium sulfate from ammonia-containing waste gas according to claim 6, characterized in that: The circulation tank is provided with an agitator, and the upper overflow circulation slurry of the crystallization zone is mixed with the cyclone mother liquor and the centrifugal mother liquor, and is sent to the mixer through a reaction circulation pump, and is sent to the absorption spray layer after being fully mixed with sulfuric acid; the concentration of the sulfuric acid is ≥60%; the crystal slurry outlet is connected to the crystallization pump, and the ratio of the flow rate of the washing pump to the flow rate of the crystallization pump is 1 to 3.

8. The method for preparing ammonium sulfate from ammonia-containing waste gas according to claim 4, characterized in that: The absorption zone is provided with 1 to 6 absorption spray layers, and the top of the reactor is provided with 1 to 2 demister layers.

9. The method for preparing ammonium sulfate from ammonia-containing waste gas according to claim 4, characterized in that: The circulation tank is provided with a pH meter, and the pH of the circulating slurry in the circulation tank is controlled to be 4.5-5.

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10. The method for preparing ammonium sulfate from ammonia-containing waste gas according to claim 4, characterized in that: The washing spray layer is provided with annular tangential washing nozzles, which are evenly distributed and obliquely directed downward toward the center of the crystallization zone; the solid content of the slurry in the crystallization zone is controlled at 5-50%; the circulation tank is provided with a pH meter, and the circulating slurry in the circulation tank is controlled to have a pH value of 4.5-5.5.

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