Ammonium chloride drying and tail gas treatment method and device

Abstract

The invention relates to an ammonium chloride drying and tail gas treatment method and device, and belongs to the technical field of ammonium chloride production. The traditional ammonium chloride drying process adopts fluidized bed drying and has the problems of difficult tail gas treatment, large heat loss, high energy consumption, difficult cost control and the like. The problems are effectively solved by adopting a rotary dry ammonium furnace to replace a fluidized bed drying process and combining a novel tail gas comprehensive recovery tower. The drying method comprises the steps of wet ammonium crushing, mixing, drying, cooling, tail gas treatment and the like, efficient drying is achieved through steam indirect heating, and tail gas is subjected to heat recovery, acid pickling and water washing and then reaches the standard to be discharged. The device comprises a wet ammonium vibrating screen, a premixer, a rotary dry ammonium furnace, a powder flow cooler, a tail gas treatment unit and the like, and by optimizing equipment configuration and process parameters, the steam utilization rate is increased, the drying energy consumption is reduced, the tail gas output is reduced, the tail gas treatment efficiency is improved, tail gas up-to-standard emission is realized, the production cost is reduced, and the production cost is reduced. And the economic benefit and the environmental protection level of enterprises are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ammonium chloride production, and in particular to a method and a device for drying ammonium chloride and treating tail gas. Background Art

[0002] At present, ammonium chloride is usually dried by fluidized bed drying. Its production principle is to use steam to heat air, and use a blower to blow hot air into the fluidized bed to make the wet ammonium fluidized in the fluidized bed. The hot air and internal heat exchanger are used to dry the dry ammonium. Although this production process has the characteristics of large production capacity, it also produces a large amount of drying exhaust gas, which brings great difficulties to exhaust gas treatment and is not conducive to environmental protection management. At the same time, the large amount of high-temperature exhaust gas causes great heat loss and the utilization rate of steam energy is low, resulting in relatively high energy consumption in the drying ammonium process, which is not conducive to cost control. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and provide an ammonium chloride drying and tail gas treatment method and device. By adopting a rotary ammonium chloride drying furnace instead of a traditional fluidized bed drying process and combining it with a novel tail gas comprehensive recovery tower, the present invention achieves improved steam utilization and reduced drying energy consumption; significantly reduces tail gas generation and reduces tail gas treatment pressure; improves tail gas treatment efficiency and achieves tail gas emission standards; reduces production costs and improves the economic benefits and environmental protection level of the enterprise.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for drying ammonium chloride and treating tail gas comprises the following steps:

[0006] Step S1: The wet ammonium from the crystallization process is crushed by a wet ammonium vibrating screen and then distributed to a premixer through a wet ammonium distribution belt, and mixed with the return material from the return screw conveyor according to a preset ratio;

[0007] Step S2: The mixed wet ammonium is fed into a rotary ammonium drying furnace, and 0.8-1.2 MPa steam is passed into a spirally distributed steam heating pipe in the rotary ammonium drying furnace, preferably 0.9 MPa, to indirectly heat the wet ammonium, and the temperature in the rotary ammonium drying furnace is controlled at 90-100° C. to dry the wet ammonium, and the steam condensate is recovered through a flash tank;

[0008] Step S3: a portion of the dried ammonium chloride is returned to the premixer via a return screw conveyor, and the other portion is cooled to 50-65° C. in a powder flow cooler before being output;

[0009] Step S4: The tail gas in the rotary ammonium drying furnace is drawn to a slightly negative pressure state by an induced draft fan, passes through a cyclone separator and a bag filter to remove dust, and then enters a tail gas comprehensive recovery tower;

[0010] In the exhaust gas comprehensive recovery tower, the exhaust gas first passes through the lower tower heating section to heat the ammonium sulfate solution, and the heat in the exhaust gas is used to heat and concentrate the ammonium sulfate solution. The exhaust gas then passes through the middle tower acid washing section to circulate and wash with a dilute sulfuric acid solution with a pH value of 2.5-3.5 to remove ammonia and residual dust. The exhaust gas then passes through the upper tower water washing section to circulate and wash the acid mist with water, and is discharged after meeting the standards.

[0011] In step S5, when the solid-liquid ratio of ammonium sulfate in the heating section reaches 10-15%, the ammonium sulfate circulation pump is used to discharge the solution to the ammonium sulfate temporary storage tank. The ammonium sulfate temporary storage tank is stirred to prevent crystallization sedimentation. When the ammonium sulfate concentration in the pickling section reaches a set threshold, part of the solution is discharged to the lower tower heating section. The water in the water washing section is added to the pickling section, and concentrated sulfuric acid is added to maintain the pH value. Fresh water is added to the water washing section to maintain the liquid level.

[0012] Beneficial effects:

[0013] First, the present invention uses an indirect heating method of a rotary ammonium drying furnace to achieve a steam utilization rate of 70-75%, which is significantly improved compared to the 40-50% of the traditional fluidized bed drying process, and reduces the drying energy consumption;

[0014] Second, because the rotary ammonium drying furnace uses the principle of thermal radiation, it does not require a large amount of dry air. Compared with the fluidized bed drying process, the amount of tail gas can be reduced by more than 80%, which greatly reduces the pressure of tail gas treatment and alleviates the environmental burden.

[0015] Third, the new exhaust gas comprehensive recovery tower adopts a three-tower structure. The lower tower uses high-temperature exhaust gas to concentrate the ammonium sulfate solution, the middle tower uses acid washing to remove ammonia and dust, and the upper tower uses water washing to remove acid mist, ensuring that the exhaust gas meets emission standards. At the same time, it improves the recovery rate of ammonia in the exhaust gas and recovers the heat in the exhaust gas, improves the steam utilization rate and reduces the exhaust gas treatment volume, reduces energy consumption and environmental protection costs, and improves the economic benefits of the enterprise.

[0016] Furthermore, the mixing mass ratio of the wet ammonium to the returned material in step S1 is 1:0.5-1:1, which can ensure that the materials are fully mixed and dried in the rotary ammonium drying furnace, thereby improving the drying efficiency and the stability of product quality.

[0017] Furthermore, the steam condensate is recovered through a flash tank, specifically including:

[0018] The steam condensate generated by the steam heating tube in the rotary ammonium drying furnace flows into the flash tank, and the pressure is reduced to below 0.6MPa in the tank, so that part of the condensate flashes into 0.6MPa steam and returns to the low-pressure steam network for recycling. The remaining unflashed high-temperature condensate is discharged into the condensate network through the condensate pump.

[0019] Beneficial effects: Steam condensate is recovered through the flash tank, part of the condensate flashes to 0.6MPa steam and returns to the low-pressure steam network for recycling, and the remaining condensate is discharged into the condensate network, achieving efficient recovery and reuse of energy, and further reducing energy consumption and costs in the production process.

[0020] Furthermore, the micro-negative pressure in step S4 is -50Pa to -100Pa, which is dynamically adjusted by the induced draft fan to ensure that the exhaust gas can be discharged smoothly, while preventing outside air from entering and affecting the drying effect, thereby ensuring the stability and safety of the drying process.

[0021] Furthermore, in step S5, the pH value of the circulating washing liquid in the pickling section is dynamically adjusted by a concentrated acid pump, and when the ammonium sulfate concentration reaches 20-30wt%, it is discharged to the lower tower heating section, which can effectively remove ammonia and residual dust in the tail gas, ensuring that the tail gas treatment effect is stable and reliable. The lower tower heating section continuously heats and concentrates the 20-30wt% ammonium sulfate solution discharged from the middle tower through the tail gas, so that the ammonium sulfate solution reaches supersaturation, ammonium sulfate crystals are precipitated, and a solid-liquid ratio is formed. When the solid-liquid ratio of ammonium sulfate in the lower tower heating section reaches 10-15%, it is discharged to the ammonium sulfate temporary storage tank.

[0022] Furthermore, the cooling medium of the powder flow cooler in step S3 is circulating water, and the cooling time is 5-10 minutes, which can quickly cool the dried ammonium chloride to 50-65°C. A temperature sensor is provided at the ammonium chloride outlet and is linked to a circulating water inlet valve, thereby improving cooling efficiency, ensuring product quality, simplifying cooling equipment, and reducing equipment cost and energy consumption.

[0023] Furthermore, an ammonium chloride drying and tail gas treatment device for use in any of the methods described in the first aspect comprises:

[0024] Wet ammonium vibrating screen, used to break up lumps in wet ammonium;

[0025] a wet ammonium distribution belt, the inlet of which is connected to the outlet of the wet ammonium vibrating screen;

[0026] A premixer is provided with a wet ammonium inlet, a return material inlet and a mixed material outlet, wherein the wet ammonium inlet is connected to the outlet of the wet ammonium distribution belt;

[0027] A rotary ammonium drying furnace, wherein the feed port is connected to the mixed material outlet of the premixer, and a spirally distributed steam heating pipe is provided inside the rotary ammonium drying furnace, the steam inlet of the rotary ammonium drying furnace is connected to a 0.8-1.2 MPa steam network, preferably, a 0.9 MPa steam network, the steam condensate outlet of the rotary ammonium drying furnace is connected to a flash tank, and the discharge port of the rotary ammonium drying furnace is connected to a return screw conveyor and a powder flow cooler; the steam coil inside the rotary ammonium drying furnace is made of stainless steel corrosion-resistant material, and the rotary ammonium drying furnace body is made of titanium composite plate;

[0028] A powder flow cooler is used to cool the dried ammonium chloride, connected to the discharge port of the rotary ammonium drying furnace, and the outlet is connected to the dry ammonium finished product belt;

[0029] The tail gas treatment unit includes a cyclone separator, a bag dust collector, an induced draft fan, and a tail gas comprehensive recovery tower connected in sequence; the tail gas comprehensive recovery tower is divided into a lower tower heating section, a middle tower pickling section, and an upper tower water washing section, wherein the lower tower heating section is provided with an ammonium sulfate circulating heating and concentration system, the middle tower pickling section is provided with a pickling liquid circulation system, and the upper tower water washing section is provided with a water washing circulation system;

[0030] A negative pressure sensor is provided between the tail gas outlet of the rotary ammonium drying furnace and the induced draft fan, which is used to cooperate with the induced draft fan to maintain a slight negative pressure of -50Pa to -100Pa; the induced draft fan is driven by a variable frequency motor, and the negative pressure sensor and the motor drive frequency are linked. The induced draft fan frequency is adjusted in time according to the sensor value to keep the negative pressure of the rotary ammonium drying furnace constant;

[0031] The return screw conveyor has an inlet connected to the discharge port of the rotary ammonium drying furnace, and an outlet connected to the return inlet of the premixer.

[0032] Beneficial effects: The device integrates ammonium chloride drying and tail gas treatment into one. Through the coordinated work of wet ammonium vibrating screen, wet ammonium distribution belt, premixer, rotary ammonium drying furnace, powder flow cooler, tail gas treatment unit and other equipment, it realizes the full process automation control of efficient drying and environmentally friendly tail gas treatment, improves production efficiency and environmental protection level, and reduces manual operation costs.

[0033] Furthermore, the ammonium sulfate heating and concentration system includes an ammonium sulfate auxiliary heater, an ammonium sulfate circulation pump and an ammonium sulfate temporary storage tank. The ammonium sulfate auxiliary heater is in the lower tower heating section, and the ammonium sulfate circulation pump is connected between the lower tower heating section and the ammonium sulfate temporary storage tank; the pickling liquid circulation system includes a concentrated acid barrel, a concentrated acid pump, and a circulating pickling pump. The concentrated acid pump is connected to the concentrated acid barrel and the middle tower pickling section, and the circulating pickling pump is connected to the middle tower pickling section and the washing liquid temporary storage tank. The water washing circulation system includes a circulating water washing pump, and the circulating water washing pump is connected to the upper tower water washing section and the fresh water replenishment pipeline, which can ensure the recycling of pickling liquid and water washing liquid, improve the washing effect and resource utilization, and reduce the tail gas treatment cost.

[0034] Furthermore, the steam outlet of the flash tank is connected to the 0.6MPa steam network, and the condensate outlet is connected to the condensate network, which can fully recycle the waste heat in the steam condensate, further improve the energy utilization efficiency, and reduce the energy consumption and cost in the production process.

[0035] Furthermore, the steam heating pipe of the rotary ammonium drying furnace is spirally wound along the axial direction of the furnace body, and a temperature sensor is provided in the furnace. The temperature sensor monitors the temperature in the furnace in real time and feeds back the temperature signal to a control module that communicates with the temperature sensor. The control module sends a control signal to the steam valve of the steam heating pipe according to the temperature signal to adjust the opening of the steam valve, which can accurately control the temperature in the furnace, ensure the stability and safety of the drying process, and at the same time improve the uniformity of product quality.

[0036] In summary, compared with the prior art, the present invention adopts a rotary ammonium drying furnace to replace the traditional fluidized bed drying process, and combines a new tail gas comprehensive recovery tower to achieve comprehensive benefits in many aspects, such as significantly improving steam utilization, significantly reducing tail gas generation, improving tail gas treatment efficiency and environmental performance, reducing comprehensive production costs, and improving the automation and stability of the production process. Specifically, the rotary ammonium drying furnace of the present invention increases the steam utilization rate to 70-75%, which greatly reduces energy consumption compared to 40-50% of the traditional fluidized bed; the tail gas volume is reduced by more than 80%, greatly reducing the tail gas treatment pressure and environmental pollution; the new three-tower structure of the tail gas comprehensive recovery tower can efficiently remove ammonia, dust and acid mist in the tail gas, ensuring that the tail gas meets the emission standards, while improving the recovery rate of ammonia in the tail gas and waste heat recovery; by optimizing the drying and tail gas treatment process, it reduces equipment investment, reduces energy consumption and tail gas treatment costs, and improves the economic benefits and market competitiveness of the enterprise; the device design realizes the full process automation control of ammonium chloride drying and tail gas treatment, ensures the stability of the production process and the uniformity of product quality, reduces manual intervention, and improves production efficiency. Against the backdrop of fierce competition in the soda ash industry and increasingly stringent environmental protection requirements, the present invention provides ammonium chloride production companies with an efficient, energy-saving, and environmentally friendly drying and tail gas treatment solution, helping companies reduce costs, improve environmental management, and promote the sustainable development of the industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic structural diagram of an ammonium chloride drying and tail gas treatment device of the present invention;

[0038] Figure 2 This is a schematic flow chart of a method for drying ammonium chloride and treating tail gas according to the present invention;

[0039] Figure numerals: 1. Wet ammonium vibrating screen; 2. Wet ammonium distribution belt; 3. Premixer; 4. Return screw conveyor; 5. Rotary dry ammonium furnace; 6. Cyclone separator; 7. Bag dust collector; 8. Screw conveyor; 9. Induced draft fan; 10. Tail gas comprehensive recovery tower; 11. Concentrated acid barrel; 12. Concentrated acid pump; 13. Circulating pickling pump; 14. Ammonium sulfate temporary storage tank; 15. Circulating water washing pump; 16. Powder flow cooler; 17. Flash tank; 18. Dry ammonium finished product belt; 19. Dry ammonium discharging auger; 20. Ammonium sulfate auxiliary heater; 21. Ammonium sulfate circulation pump. DETAILED DESCRIPTION

[0040] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0041] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0042] In the description of the invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0043] The present invention will be further described in detail below with reference to the accompanying drawings and specific preferred embodiments.

[0044] Against the backdrop of increasingly fierce competition in the soda ash industry and increasingly stringent environmental protection requirements, the present invention provides ammonium chloride production companies with an efficient, energy-saving, and environmentally friendly drying and tail gas treatment solution, helping companies reduce costs, improve environmental management levels, enhance market competitiveness, and promote the sustainable development of the industry.

[0045] like Figures 1 and 2 As shown, a method for drying ammonium chloride and treating tail gas comprises the following steps:

[0046] Step S1: The wet ammonium from the crystallization process is crushed by the wet ammonium vibrating screen 1 and then distributed to the premixer 3 through the wet ammonium distribution belt 2. It is mixed with the return material returned by the return screw conveyor 4 according to a preset ratio. The mixing mass ratio of wet ammonium to return material is 1:0.5-1:1;

[0047] Step S2, the mixed wet ammonium is fed into the rotary ammonium drying furnace 5, 0.8-1.2 MPa steam is passed into the steam heating pipes distributed in a spiral shape in the rotary ammonium drying furnace 5 to indirectly heat the wet ammonium, and the temperature in the rotary ammonium drying furnace is controlled at 90-100° C. to dry the wet ammonium, and the steam condensate is recovered through the flash tank 17. The specific recovery process is as follows: the steam condensate generated by the steam heating pipe in the rotary ammonium drying furnace 5 flows into the flash tank 17, and the pressure is reduced to below 0.6 MPa in the tank, so that part of the condensate is flashed into 0.6 MPa steam, which is returned to the low-pressure steam network for recycling, and the remaining high-temperature condensate that has not been flashed is discharged into the condensate network through the condensate pump;

[0048] Step S3: a portion of the dried ammonium chloride is returned to the premixer 3 via the return screw conveyor 4, and the other portion is cooled to 50-65° C. by the powder flow cooler 16 before being output;

[0049] Step S4: The tail gas in the rotary ammonium drying furnace 5 is drawn to a slightly negative pressure state by the induced draft fan 9, the slightly negative pressure is -50Pa to -100Pa, and passes through the cyclone separator 6 and the bag dust collector 7 in sequence to remove dust, and then enters the tail gas comprehensive recovery tower 10;

[0050] In the tail gas comprehensive recovery tower 10, the tail gas first passes through the ammonium sulfate heating section of the lower tower to recover heat, and the residual heat in the tail gas is used to heat and concentrate the ammonium sulfate solution. Then, the tail gas passes through the acid washing section of the middle tower and is circulated and washed with a dilute sulfuric acid solution with a pH value of 2.5-3.5 to remove ammonia and residual dust. Then, the tail gas passes through the water washing section of the upper tower and is circulated with water to wash the acid mist. After meeting the standards, it is discharged;

[0051] Step S5: The ammonium sulfate in the heating section is heated and concentrated by the tail gas and the ammonium sulfate auxiliary heater. When the ammonium sulfate solution reaches a certain solid-liquid ratio, it is discharged to the ammonium sulfate temporary storage tank 14. When the ammonium sulfate concentration of the pickling section reaches a set threshold, part of the solution is discharged to the lower tower heating section. The water in the water washing section is replenished to the pickling section, and concentrated sulfuric acid is added to maintain the pH value. Fresh water is replenished in the water washing section to maintain the liquid level. Specifically, the pH value of the circulating washing liquid in the pickling section is dynamically adjusted by a concentrated acid pump. When the ammonium sulfate concentration reaches 20-30wt%, it is discharged to the lower tower heating section.

[0052] Furthermore, in step S1, the mixing mass ratio of wet ammonium to return material is 1:0.5-1:1.

[0053] Furthermore, the steam condensate is recovered through the flash tank 17, specifically including:

[0054] The steam condensate generated by the steam heating tube in the rotary ammonium drying furnace 5 flows into the flash tank 17, and the pressure is reduced to below 0.6 MPa in the tank, so that part of the condensate flashes into 0.6 MPa steam and returns to the low-pressure steam network for recycling. The remaining unflashed high-temperature condensate is discharged into the condensate network through the condensate pump.

[0055] Furthermore, the slight negative pressure in step S4 is dynamically adjusted by the induced draft fan 9 .

[0056] Furthermore, in step S5, when the solid-liquid ratio of ammonium sulfate in the heating section reaches 10-15%, it is discharged into the ammonium sulfate temporary storage tank.

[0057] Furthermore, in step S5, the pH value of the circulating washing liquid in the pickling section is dynamically adjusted by a concentrated acid pump, and when the ammonium sulfate concentration reaches 20-30 wt%, it is discharged to the lower tower heating section.

[0058] Furthermore, in step S3, the cooling medium of the powder flow cooler 16 is circulating water, and the cooling time is 5-10 minutes.

[0059] Compared with the prior art, the present invention achieves the following comprehensive beneficial effects by adopting a rotary ammonium drying furnace 5 instead of a traditional fluidized bed drying process and combining it with a tail gas comprehensive recovery tower 10:

[0060] Significantly improve steam utilization: The design of the rotary ammonium drying furnace 5 of the present invention increases the steam utilization from 40-50% of the traditional fluidized bed to 70-75%, greatly reducing energy consumption in the drying process, reducing energy waste, and improving the economy of the production process.

[0061] Significantly reduce the amount of tail gas generated: by drying in the rotary ammonium drying furnace 5, the amount of tail gas can be reduced by more than 80%, which greatly reduces the pressure and cost of tail gas treatment, while reducing pollution to the environment and improving the environmental protection level of the enterprise.

[0062] Improve tail gas treatment efficiency and environmental performance: The tail gas comprehensive recovery tower 10, through the synergistic effect of heat recovery, acid washing and water washing, effectively recovers the waste heat in the tail gas while removing ammonia, dust and acid mist in the tail gas, ensuring that the tail gas meets emission standards. At the same time, it improves the recovery and utilization rate of ammonia in the tail gas, achieving the dual benefits of environmental protection and resource recovery.

[0063] Reduce overall production costs: By optimizing the drying and tail gas treatment processes, equipment investment is reduced (such as eliminating blowers, external heaters, etc.), energy consumption and tail gas treatment costs are reduced, and the company's economic benefits and market competitiveness are improved.

[0064] Improve the automation and stability of the production process: The device design of the present invention realizes the automatic control of the whole process of ammonium chloride drying and tail gas treatment. Through the temperature sensor, negative pressure sensor and dynamic adjustment system, the stability of the production process and the uniformity of product quality are ensured, which reduces manual intervention and improves production efficiency.

[0065] As an example, Figures 1 and 2 The ammonium chloride drying and tail gas treatment device of any method comprises:

[0066] Wet ammonium vibrating screen 1, used to break up the lumps in wet ammonium;

[0067] A wet ammonium distribution belt 2, the inlet of which is connected to the outlet of the wet ammonium vibrating screen 1;

[0068] The premixer 3 is provided with a wet ammonium inlet, a return material inlet and a mixed material outlet, and the wet ammonium inlet is connected to the outlet of the wet ammonium distribution belt 2;

[0069] The rotary ammonium drying furnace 5 has a feed port connected to the mixture outlet of the premixer 3, and a spirally distributed steam heating pipe is provided inside the rotary ammonium drying furnace 5, the steam inlet of the rotary ammonium drying furnace 5 is connected to the 0.8-1.2 MPa steam network, the steam condensate outlet of the rotary ammonium drying furnace 5 is connected to the flash tank 17, and the discharge port of the rotary ammonium drying furnace 5 is connected to the return screw conveyor 4 and the powder flow cooler 16; the steam heating pipe of the rotary ammonium drying furnace 5 is spirally wound along the axial direction of the furnace body, and a temperature sensor is provided in the furnace to monitor the temperature in real time and feed it back to the steam valve; further, the steam coil inside the rotary ammonium drying furnace 5 is made of stainless steel corrosion-resistant material, preferably stainless steel-316L, and the furnace body of the rotary ammonium drying furnace is made of titanium composite plate, preferably titanium-304, which saves cost and can resist the strong corrosiveness of ammonium chloride, thereby extending the service life of the rotary ammonium drying furnace.

[0070] The powder flow cooler 16 is used to cool the dried ammonium chloride, connected to the discharge port of the rotary ammonium drying furnace 5, and the outlet is connected to the dry ammonium finished product belt 18;

[0071] The tail gas treatment unit includes a cyclone separator 6, a bag dust collector 7, an induced draft fan 9 and a tail gas comprehensive recovery tower 10 connected in sequence; the tail gas comprehensive recovery tower 10 is divided into a lower tower heating section, a middle tower pickling section and an upper tower water washing section, wherein the lower tower heating section is provided with an ammonium sulfate heating and concentration system, the middle tower pickling section is provided with a pickling liquid circulation system, and the upper tower water washing section is provided with a water washing circulation system; and a negative pressure sensor is provided between the tail gas outlet of the rotary ammonium drying furnace 5 and the induced draft fan 9, which is used to cooperate with the induced draft fan 9 to maintain a micro-negative pressure of -50Pa to -100Pa; the induced draft fan is driven by a variable frequency motor, and the negative pressure sensor and the motor drive frequency are linked. The induced draft fan frequency is adjusted in time according to the sensor value to keep the negative pressure of the rotary ammonium drying furnace constant;

[0072] The return screw conveyor 4 has an inlet connected to the discharge port of the rotary ammonium drying furnace 5 and an outlet connected to the return inlet of the premixer 3.

[0073] In order to improve the energy efficiency of the ammonium chloride drying process and reduce the impact on the environment, the present invention adopts a drying system consisting of components such as a rotary ammonium drying furnace 5, a cyclone separator 6 and a premixer 3 in the device. The system achieves efficient drying of materials, reduces overall energy consumption, and reduces tail gas emissions. By returning the partially dried ammonium chloride to the premixer 3 through a return screw conveyor 4 and mixing it with the wet ammonium material, and utilizing the indirect heating method of the steam heating pipe in the rotary ammonium drying furnace 5, the environmental protection problems and energy waste phenomena existing in the original fluidized bed process are effectively solved. At the same time, the flash steam (0.6MPa) is recovered by the steam condensate through the flash tank 17 and returned to the pipe network, achieving efficient recovery and reuse of heat, so that the steam utilization rate is increased from 40-50% to 70-75%, further improving the energy efficiency of the whole drying process.

[0074] As an embodiment, in the exhaust gas treatment process of the present invention, the dust-containing exhaust gas in the production process is subjected to the action of the induced draft fan 9. After the large particles in the exhaust gas are separated by the cyclone separator 6, the larger particles fall to the bottom of the cyclone separator 6 due to the action of centrifugal force, and the dry ammonium dust is placed on the dry ammonium finished product belt 18 through the star-shaped discharger; the exhaust gas containing small particles of dust is drawn by the induced draft fan 9 through the bag dust collector 7, and the dust particles are intercepted by the filter bag. The purified gas passes through the filter bag and is sent by the induced draft fan 9 to the exhaust gas comprehensive recovery tower 10 for treatment and then discharged.

[0075] As an example, the working principle of the bag filter 7 is as follows: When dust-laden exhaust gas enters the bag filter 7 from the inlet, some coarser particles naturally settle into the ash hopper due to inertial collision. Most dust particles rise with the airflow into the bag chamber. After being filtered by the filter bags, the dust particles are retained outside the filter bags. The purified gas enters the box outlet through the filter bags and is discharged into the atmosphere. As the filtration process progresses, dust accumulation outside the filter bags gradually increases. When the operating resistance increases to a set value, the dust cleaning system sends a signal, and the solenoid valve opens, blowing 0.4-0.6MPa compressed air into the box for 0.1-2.2 seconds. The compressed air rapidly expands, deforms, and vibrates in the box. Combined with the impact of the airflow, the dust outside the filter bags is removed and falls into the ash hopper. The accumulated dust in the ash hopper is discharged via the screw conveyor 8 and the star-shaped discharger to the dry ammonium finished product belt 18.

[0076] Furthermore, the ammonium sulfate heating and concentration system includes an ammonium sulfate auxiliary heater 20, an ammonium sulfate circulation pump 21, and an ammonium sulfate temporary storage tank 14. The tail gas in the tail gas comprehensive recovery tower 10 first passes through the lower tower heating section, and the ammonium sulfate solution is heated and concentrated by using the waste heat in the tail gas. The ammonium sulfate auxiliary heater 20 is in the lower tower heating section. As a preferred redundant design, when the heat of the tail gas is insufficient, the ammonium sulfate solution is auxiliary heated and concentrated. The ammonium sulfate circulation pump 21 is connected between the lower tower heating section and the ammonium sulfate temporary storage tank 14.

[0077] The pickling liquid circulation system includes a concentrated acid barrel 11, a concentrated acid pump 12, and a circulating pickling pump 13. The concentrated acid pump 12 connects the concentrated acid barrel 11 with the lower tower pickling section, and the circulating pickling pump 13 connects the middle tower pickling section with the lower tower heating section.

[0078] The water washing circulation system includes a circulating water washing pump 15, which is connected to the upper tower water washing section and the fresh water replenishment pipeline.

[0079] Furthermore, the steam outlet of the flash tank 17 is connected to the 0.6 MPa steam network, and the condensed water outlet is connected to the condensed water network.

[0080] Furthermore, the steam heating pipe of the rotary ammonium drying furnace 5 is spirally wound along the axial direction of the furnace body, and a temperature sensor is provided in the furnace. The temperature sensor monitors the temperature in the furnace in real time and feeds back the temperature signal to a control module that communicates with the temperature sensor. The control module sends a control signal to the steam valve of the steam heating pipe according to the temperature signal to adjust the opening of the steam valve.

[0081] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for drying ammonium chloride and treating tail gas, characterized in that: The following steps are involved: Step S1: The wet ammonium from the crystallization process is crushed by a wet ammonium vibrating screen (1), distributed to a premixer (3) through a wet ammonium distribution belt (2), and mixed with the return material from a return screw conveyor (4) according to a preset ratio; Step S2, the mixed wet ammonium is fed into a rotary ammonium drying furnace (5), 0.8-1.2 MPa steam is passed into a steam heating pipe distributed in a spiral shape in the rotary ammonium drying furnace (5) to indirectly heat the wet ammonium, and the temperature in the rotary ammonium drying furnace is controlled at 90-100° C. to dry the wet ammonium, and the steam condensate is recovered through a flash tank (17); Step S3: a portion of the dried ammonium chloride is returned to the premixer (3) via the return screw conveyor (4), and the other portion is cooled to 50-65° C. by the powder flow cooler (16) before being output; Step S4: The tail gas in the rotary ammonium drying furnace (5) is drawn to a slightly negative pressure state by an induced draft fan (9), wherein the slightly negative pressure is -50 Pa to -100 Pa, and then passes through a cyclone separator (6) and a bag dust collector (7) to remove dust, and then enters a tail gas comprehensive recovery tower (10); In the exhaust comprehensive recovery tower (10), the exhaust gas first passes through the lower tower heating section, where the residual heat in the exhaust gas is used to heat and concentrate the ammonium sulfate solution, then passes through the middle tower acid washing section, where it is circulated and washed with a dilute sulfuric acid solution with a pH value of 2.5-3.5 to remove ammonia and residual dust, and then passes through the upper tower water washing section where it is circulated and washed with water to wash the acid mist, and is discharged after meeting the standards; Step S5: After the ammonium sulfate solution in the heating section reaches a certain solid-liquid ratio, it is discharged to the ammonium sulfate temporary storage tank (14). When the ammonium sulfate concentration of the pickling section reaches a set threshold, the solution is added to the lower tower heating section. The water in the water washing section is added to the pickling section, and concentrated sulfuric acid is added to maintain the pH value. Fresh water is added to the water washing section to maintain the liquid level.

2. The ammonium chloride drying and tail gas treatment method according to claim 1, wherein The mixing mass ratio of the wet ammonium to the return material in step S1 is 1:0.5-1:

1.

3. The ammonium chloride drying and tail gas treatment method according to claim 1, wherein The steam condensate is recovered through the flash tank (17), specifically including: The steam condensate generated by the steam heating tube in the rotary ammonium drying furnace (5) flows into the flash tank (17), and the pressure is reduced to below 0.6 MPa in the tank, so that part of the condensate flashes into 0.6 MPa steam and returns to the low-pressure steam network for recycling. The remaining high-temperature condensate that has not flashed is discharged into the condensate network through the condensate pump.

4. The ammonium chloride drying and tail gas treatment method according to claim 1, wherein The slight negative pressure in step S4 is dynamically adjusted by the induced draft fan (9).

5. The method for drying ammonium chloride and treating tail gas according to claim 1, wherein: The pH value of the circulating washing liquid in the pickling section in step S5 is dynamically adjusted by a concentrated acid pump, and when the ammonium sulfate concentration reaches 20-30wt%, it is discharged to the lower tower heating section, and when the solid-liquid ratio of the ammonium sulfate solution in the lower tower heating section reaches 10-15%, it is discharged to the ammonium sulfate temporary storage tank.

6. The method for drying ammonium chloride and treating tail gas according to claim 1, wherein: The cooling medium of the powder flow cooler (16) in step S3 is circulating water, and the cooling time is 5-10 minutes.

7. An ammonium chloride drying and tail gas treatment device for the method according to any one of claims 1 to 6, characterized in that: include: Wet ammonium vibrating screen (1), used to break up lumps in wet ammonium; a wet ammonium distribution belt (2), the inlet of which is connected to the outlet of the wet ammonium vibrating screen (1); The premixer (3) is provided with a wet ammonium inlet, a return material inlet and a mixed material outlet, wherein the wet ammonium inlet is connected to the outlet of the wet ammonium distribution belt (2); A rotary ammonium drying furnace (5) has a feed port connected to the mixed material outlet of the premixer (3), and a spirally distributed steam heating pipe is provided inside the rotary ammonium drying furnace (5), the steam inlet of the rotary ammonium drying furnace (5) is connected to a 0.8-1.2 MPa steam pipe network, the steam condensate outlet of the rotary ammonium drying furnace (5) is connected to a flash tank (17), and the discharge port of the rotary ammonium drying furnace (5) is connected to a return screw conveyor (4) and a powder flow cooler (16); the steam coil inside the rotary ammonium drying furnace (5) is made of stainless steel corrosion-resistant material, and the rotary ammonium drying furnace body is made of titanium composite plate; A powder flow cooler (16) is used to cool the dried ammonium chloride, connected to the discharge port of the rotary ammonium drying furnace (5), and the outlet is connected to the dry ammonium finished product belt (18); The tail gas treatment unit comprises a cyclone separator (6), a bag dust collector (7), an induced draft fan (9) and a tail gas comprehensive recovery tower (10) connected in sequence; the tail gas comprehensive recovery tower (10) is divided into a lower tower heating section, a middle tower pickling section and an upper tower water washing section, wherein an ammonium sulfate circulating heating and concentration system is provided for the lower tower heating section, an acid washing liquid circulation system is provided for the middle tower pickling section, and a water washing circulation system is provided for the upper tower water washing section; A negative pressure sensor is provided between the tail gas outlet of the rotary ammonium drying furnace (5) and the induced draft fan (9), for cooperating with the induced draft fan (9) to maintain a slight negative pressure of -50Pa to -100Pa; the induced draft fan is driven by a variable frequency motor, and the negative pressure sensor and the motor drive frequency are linked to maintain a constant negative pressure in the rotary ammonium drying furnace; The return screw conveyor (4) has an inlet connected to the discharge port of the rotary ammonium drying furnace (5), and an outlet connected to the return inlet of the premixer (3).

8. The ammonium chloride drying and tail gas treatment device according to claim 7, characterized in that: The ammonium sulfate heating and concentration system comprises an ammonium sulfate auxiliary heater (20), an ammonium sulfate circulation pump (21), and an ammonium sulfate temporary storage tank (14); the ammonium sulfate auxiliary heater (20) is arranged in the lower tower heating section, and the ammonium sulfate circulation pump (21) is connected between the lower tower heating section and the ammonium sulfate temporary storage tank (14); The pickling liquid circulation system comprises a concentrated acid barrel (11), a concentrated acid pump (12), and a circulating pickling pump (13), wherein the concentrated acid pump (12) is connected to the concentrated acid barrel (11) and the middle tower pickling section, and the circulating pickling pump (13) is connected to the middle tower pickling section; The water washing circulation system comprises a circulating water washing pump (15), and the circulating water washing pump (15) is connected to the upper tower water washing section and the fresh water replenishment pipeline.

9. The ammonium chloride drying and tail gas treatment device according to claim 7, characterized in that: The steam outlet of the flash tank (17) is connected to the 0.6MPa steam network, and the condensed water outlet is connected to the condensed water network.

10. The ammonium chloride drying and tail gas treatment device according to claim 7, characterized in that: The steam heating pipe of the rotary ammonium drying furnace (5) is spirally wound along the axial direction of the furnace body, and a temperature sensor is provided in the furnace. The temperature sensor monitors the temperature in the furnace in real time and feeds back the temperature signal to a control module that communicates with the temperature sensor. The control module sends a control signal to the steam valve of the steam heating pipe according to the temperature signal to adjust the opening of the steam valve.

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