Urea storage tank tail gas emptying and purifying treatment system and method

Abstract

The invention discloses a tail gas emptying and purifying treatment system for a urea storage tank, which relates to the technical field of urea production and comprises a tail gas absorbing and washing tank, a tail gas washing circulating pump, a gas phase pipeline and a liquid phase pipeline, wherein the tail gas absorbing and washing tank is filled with a polypropylene Pall ring filler, a liquid distributor is arranged above the polypropylene Pall ring filler, and a gas distributor is arranged below the polypropylene Pall ring filler; the tail gas purification efficiency is remarkably improved, a single-tower integrated multi-strand tail gas treatment mode is adopted, a polypropylene Pall ring packing layer and a gas-liquid distributor are matched, the mass transfer effect of gas-liquid countercurrent contact is enhanced, the removal efficiency of ammonia in the tail gas is greatly improved, it is ensured that the treated tail gas can stably reach the environment-friendly emission standard, and the treatment effect is good. The problem that tail gas emission exceeds the standard in a traditional process is effectively solved, and pollution of ammonia-containing gas to the atmospheric environment is fundamentally reduced.

Description

Technical Field

[0001] This invention relates to the field of urea production technology, and more specifically, to a system and method for purifying and treating tail gas from urea storage tanks. Background Technology

[0002] In the urea production sector, the carbon dioxide stripping process generates ammonia-containing exhaust gas from equipment such as ammonia tanks, emergency tanks, and urea tanks. Existing exhaust gas treatment technologies have significant shortcomings. Traditional treatment processes often suffer from low gas-liquid contact efficiency due to equipment structural design flaws, making it difficult to achieve efficient absorption of ammonia in the exhaust gas and thus making it difficult to consistently meet environmental protection requirements for exhaust gas emissions.

[0003] Meanwhile, existing technologies have significant shortcomings in resource recovery. Most processes lack a complete ammonia recovery system, which not only wastes ammonia resources but also increases raw material costs for enterprises. Furthermore, some treatment processes are energy-intensive, requiring substantial additional energy investment to maintain operation, thus lacking economic viability and sustainability. There is an urgent need to develop a high-efficiency, low-consumption exhaust gas purification technology that also features resource recovery capabilities.

[0004] No effective solutions have yet been proposed to address the problems in the relevant technologies. Summary of the Invention

[0005] In view of the problems in the related technologies, the present invention proposes a urea storage tank tail gas venting and purification system and method to overcome the above-mentioned technical problems existing in the existing related technologies.

[0006] The technical solution of this invention is implemented as follows:

[0007] One aspect of the present invention:

[0008] A urea storage tank tail gas venting and purification system includes: a tail gas absorption and scrubbing tank, a tail gas scrubbing circulation pump, and supporting gas phase pipelines and liquid phase pipelines.

[0009] The exhaust gas absorption and scrubbing tank is filled with polypropylene Pall ring packing, with a liquid distributor above the polypropylene Pall ring packing and a gas distributor below it.

[0010] The gas phase pipeline includes: an emergency tank gas phase pipeline, a final condenser gas phase pipeline, a urine tank gas phase pipeline, a closed drain tank gas phase pipeline, a hydraulic jet outlet gas phase pipeline, and an ammonia tank gas phase pipeline. The emergency tank gas phase pipeline, the final condenser gas phase pipeline, the urine tank gas phase pipeline, the closed drain tank gas phase pipeline, the hydraulic jet outlet gas phase pipeline, and the ammonia tank gas phase pipeline are all connected to the lower part of the tail gas absorption and scrubbing tank.

[0011] The liquid phase pipeline includes: a purification process condensate pipeline, an absorbent circulation pipeline, and an absorbent discharge pipeline. The purification process condensate pipeline is drawn from the dust replenishment pump of the granulation tower, spraying the condensate from the top of the tail gas absorption scrubbing tank to the liquid distributor. The absorbent circulation pipeline connects the bottom of the tail gas absorption scrubbing tank to the inlet of the tail gas scrubbing circulation pump, pressurizing the absorbent and sending it to the upper part of the tail gas absorption scrubbing tank for circulation absorption. When the ammonia concentration of the absorbent exceeds the threshold, the absorbent discharge pipeline discharges the absorbent into the ammonia water tank.

[0012] Furthermore, the gas phase pipelines of the emergency tank and the final condenser are made of stainless steel 304, while the gas phase pipelines of the urine tank, the sealed drain tank, the hydraulic jet gas phase pipeline, and the ammonia tank are made of carbon steel.

[0013] Furthermore, the exhaust gas absorption scrubbing tank is equipped with an exhaust gas emission pipeline at the top, with a diameter of DN300 and made of carbon steel, and an online ammonia concentration monitor is installed at the outlet.

[0014] Furthermore, pneumatic regulating valves and electromagnetic flow meters are respectively installed on the gas phase pipelines of the accident tank, the final condenser, the urine tank, the sealed drain tank, the hydraulic jet outlet, and the ammonia tank.

[0015] Furthermore, the liquid distributor is a tray-type distributor, and the gas distributor is a perforated plate type distributor, with a gas-liquid contact area ≥ 200 m². 2 .

[0016] Another aspect of the present invention:

[0017] A method for purifying and treating exhaust gas from a urea storage tank includes the following steps:

[0018] Ammonia-containing tail gas generated from various storage tanks and equipment is collected and sent to the lower part of the tail gas absorption and scrubbing tank through a gas phase pipeline, with the total intake volume controlled at 300-500 m³ / h. 3 / h, the pneumatic regulating valves of each pipeline automatically adjust their opening degree according to the flow signal;

[0019] The purification process condensate at a temperature of 20-30℃ is drawn from the dust makeup water pump of the granulation tower and pumped at a flow rate of 50-80m³. 3 A flow rate of / h is sprayed from the top of the exhaust gas absorption scrubbing tank, and comes into countercurrent contact with the exhaust gas flowing from bottom to top in the packing layer. Ammonia is absorbed through mass transfer, and the pH value of the scrubbing liquid is monitored in real time and controlled at 7-9.

[0020] The absorbent liquid is pressurized by the exhaust gas washing circulation pump from the bottom of the exhaust gas absorption and washing tank, and then flows at a rate of 80-120 m³ / h. 3 A flow rate of / h is sent to the upper part of the washing tank for circulation absorption, and the concentration of circulating liquid ammonia is monitored online;

[0021] When the concentration of circulating liquid ammonia exceeds 2%, the pneumatic discharge valve of the absorbent discharge pipeline is automatically opened to discharge the absorbent into the ammonia tank, while fresh purification process condensate is added to maintain the circulating liquid level.

[0022] The treated exhaust gas is discharged through the top emission pipeline, and the ammonia content is ensured to be ≤225mg / m³ by an online ammonia concentration monitor. 3 .

[0023] This also includes maintaining the gas-liquid ratio in the packing layer at 5-8:1 by controlling the flow rate and temperature of the condensate in the purification process.

[0024] The pH value of the circulating liquid is adjusted by adding dilute sulfuric acid or ammonia.

[0025] The treated exhaust gas is discharged through the top discharge pipeline, which includes: real-time data linkage between the ammonia concentration online monitoring instrument and the gas phase pipeline intake volume; when the ammonia content of the exhaust gas approaches 225 mg / m3, the flow rate of the purification process condensate is automatically increased to 70-80 m3 / h.

[0026] The step of discharging the absorbent into the ammonia tank includes maintaining the ammonia temperature at 40-50°C using a heating coil inside the ammonia tank to reduce ammonia volatilization loss and improve recovery efficiency.

[0027] The beneficial effects of this invention are:

[0028] 1. This invention achieves a significant improvement in exhaust gas purification efficiency through optimized system structure and process design. It employs a single-tower integrated multi-stream exhaust gas treatment mode, combined with a polypropylene Pall ring packing layer and a gas-liquid distributor, enhancing the mass transfer effect of gas-liquid countercurrent contact. This greatly improves the ammonia removal efficiency in the exhaust gas, ensuring that the treated exhaust gas consistently meets environmental emission standards. This effectively solves the problem of excessive exhaust gas emissions in traditional processes, fundamentally reducing ammonia-containing gas pollution of the atmospheric environment.

[0029] 2. This invention utilizes the condensate from the existing purification process in the production process as the absorbent, eliminating the need for additional chemical agents, thus reducing operating costs and avoiding secondary pollution. Through the synergistic action of the circulating pump and the automated control system, precise circulation and concentration control of the absorbent are achieved, maximizing the recovery of ammonia resources from the exhaust gas and reducing raw material waste. Simultaneously, the system employs a low-power circulating pump and a high-efficiency packed tower design, significantly reducing energy consumption compared to traditional treatment processes. This improves resource utilization while significantly enhancing the economic efficiency and sustainability of the process. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic flowchart of a method for purifying and venting tail gas from a urea storage tank according to an embodiment of the present invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0033] According to an embodiment of the present invention, a urea storage tank tail gas venting and purification system is provided.

[0034] The urea storage tank tail gas venting and purification system according to an embodiment of the present invention includes: a tail gas absorption and scrubbing tank, a tail gas scrubbing circulation pump, and supporting gas phase pipeline, liquid phase pipeline and tail gas discharge pipeline.

[0035] The exhaust gas absorption and scrubbing tank is made of Q235-B carbon steel lined with fiberglass, with a specification of φ1400×2400mm. It is filled with polypropylene Pall ring packing with a height of 1.5m. A liquid distributor is set above the packing layer and a gas distributor is set below to ensure uniform gas-liquid contact.

[0036] The gas phase pipelines include: the emergency tank gas phase pipeline (DN400, 304 stainless steel, pressure resistance ≥0.6MPa), the final condenser gas phase pipeline (DN100, 304 stainless steel), the urine tank gas phase pipeline (DN350, carbon steel), the closed drainage tank gas phase pipeline (DN150, carbon steel), the hydraulic jet outlet gas phase pipeline (DN200, carbon steel), and the ammonia tank gas phase pipeline (DN400, carbon steel). Each gas phase pipeline connects to the lower part of the tail gas absorption and scrubbing tank, and each pipeline is equipped with a pneumatic regulating valve (accuracy ±1%) and an electromagnetic flowmeter (range 0-500m). 3 / h), to achieve precise control of exhaust gas flow.

[0037] The liquid phase pipelines include: purification process condensate pipelines, absorbent circulation pipelines, and absorbent discharge pipelines, as detailed below:

[0038] The condensate pipeline for the purification process is drawn from the dust makeup water pump of the granulation tower. The pipe diameter is DN80, the material is 304 stainless steel, and a rotor flow meter (range 0-100m) is installed. 3 / h), the condensate at a temperature of 20-30℃ is sprayed in from the top of the exhaust gas absorption and scrubbing tank.

[0039] The absorbent circulation pipeline has a diameter of DN100, is made of carbon steel, and connects the bottom of the exhaust gas absorption and scrubbing tank to the inlet of the exhaust gas scrubbing circulation pump. The pump model is IS100-80-125, with a flow rate of 100 m³ / h. 3 / h, head 32m, power 15kW, after pressurization, the absorbent liquid is sent to the upper part of the tail gas absorption and scrubbing tank for circulation absorption.

[0040] The absorbent discharge pipeline has a diameter of DN50 and is made of carbon steel. An online ammonia concentration meter (measurement range 0-10%, accuracy ±0.5%) is installed at the bottom of the tail gas absorption and scrubbing tank. When the ammonia concentration in the absorbent exceeds 2%, the pneumatic discharge valve is automatically opened to discharge the absorbent into the ammonia water tank.

[0041] The exhaust gas emission pipeline has a diameter of DN300, is made of carbon steel, and is installed on the top of the exhaust gas absorption and scrubbing tank. An online ammonia concentration monitor is installed at the outlet to monitor the ammonia content in the exhaust gas in real time.

[0042] Using the above technical solution, ammonia-containing tail gas generated by various storage tanks and equipment is collected at the bottom of the tail gas absorption and scrubbing tank via a gas phase pipeline. The total intake air volume is controlled by a pneumatic regulating valve and a flow meter to ensure stable system operation. The purification process condensate is sprayed from the top of the tail gas absorption and scrubbing tank at a controlled flow rate, and comes into countercurrent contact with the tail gas flowing upwards in the packing layer. Ammonia in the tail gas is absorbed through mass transfer, and the scrubbing temperature and pH value are controlled within a preset range. The absorbent is pressurized by the tail gas scrubbing circulation pump and circulated to the top of the tail gas absorption and scrubbing tank. The ammonia concentration in the circulating liquid is monitored online. When the concentration exceeds the preset value, the discharge program is automatically initiated. The discharged absorbent is discharged into the ammonia water tank to realize ammonia resource recovery, and fresh purification process condensate is added to maintain the circulating liquid level. The treated tail gas is discharged through the top tail gas discharge pipeline, and the ammonia content is monitored online to meet the requirements of the GB16297-1996 Class II standard.

[0043] According to an embodiment of the present invention, a method for purifying and treating the exhaust gas from a urea storage tank is provided.

[0044] like Figure 1 As shown, the urea storage tank tail gas venting and purification treatment method according to an embodiment of the present invention includes the following steps:

[0045] Ammonia-containing tail gas generated from various storage tanks and equipment is collected and sent to the lower part of the tail gas absorption and scrubbing tank through a gas phase pipeline, with the total intake volume controlled at 300-500 m³ / h. 3 / h, the pneumatic regulating valves of each pipeline automatically adjust their opening degree according to the flow signal;

[0046] The purification process condensate at a temperature of 20-30℃ is drawn from the dust makeup water pump of the granulation tower and pumped at a flow rate of 50-80m³. 3 A flow rate of / h is sprayed from the top of the exhaust gas absorption scrubbing tank, and comes into countercurrent contact with the exhaust gas flowing from bottom to top in the packing layer. Ammonia is absorbed through mass transfer, and the pH value of the scrubbing liquid is monitored in real time and controlled at 7-9.

[0047] The absorbent liquid is pressurized by the exhaust gas washing circulation pump from the bottom of the exhaust gas absorption and washing tank, and then flows at a rate of 80-120 m³ / h. 3 A flow rate of / h is sent to the upper part of the washing tank for circulation absorption, and the concentration of circulating liquid ammonia is monitored online;

[0048] When the concentration of circulating liquid ammonia exceeds 2%, the pneumatic discharge valve of the absorbent discharge pipeline is automatically opened to discharge the absorbent into the ammonia tank, while fresh purification process condensate is added to maintain the circulating liquid level.

[0049] The treated exhaust gas is discharged through the top emission pipeline, and the ammonia content is ensured to be ≤225mg / m³ by an online ammonia concentration monitor. 3 .

[0050] This also includes maintaining the gas-liquid ratio in the packing layer at 5-8:1 by controlling the flow rate and temperature of the condensate in the purification process.

[0051] The pH value of the circulating liquid is adjusted by adding dilute sulfuric acid or ammonia.

[0052] The treated exhaust gas is discharged through the top discharge pipeline, which includes: real-time data linkage between the ammonia concentration online monitoring instrument and the gas phase pipeline intake volume; when the ammonia content of the exhaust gas approaches 225 mg / m3, the flow rate of the purification process condensate is automatically increased to 70-80 m3 / h.

[0053] The step of discharging the absorbent into the ammonia tank includes maintaining the ammonia temperature at 40-50°C using a heating coil inside the ammonia tank to reduce ammonia volatilization loss and improve recovery efficiency.

[0054] Specifically, taking the application of a certain company's No. 2 urea plant as an example, this company uses the carbon dioxide stripping process with a production capacity of 2800 t / d. Before the modification, the tail gas from each storage tank was directly emitted, with an ammonia content of 1800 mg / m³. 3 The annual ammonia emissions are approximately 1,642 tons, resulting in environmental fines and raw material waste losses amounting to 4.926 million yuan per year.

[0055] A tail gas absorption and scrubbing tank with a specification of φ1400×2400mm was pre-installed on the fourth floor of the plant area, filled with 1.5m high polypropylene Pall rings, and equipped with an IS100-80-125 circulation pump. Simultaneously, six gas phase pipelines (total diameter DN1600) were connected to the lower part of the tail gas absorption and scrubbing tank, each equipped with a pneumatic regulating valve and flow meter. A DN80 condensate pipeline was led from the dust makeup water pump of the granulation tower to the top of the scrubbing tank. Two online ammonia concentration meters, six electromagnetic flow meters, and one pH meter were also installed and connected to the DCS system for automatic control.

[0056] During operation, the relevant operating parameters, specifically the exhaust gas treatment capacity, are: 420m³. 3 / h; Condensate flow rate in purification process: 65m³ / h 3 / h, temperature 25℃; circulating pump flow rate: 100m³ / h 3 / h, power 15kW; automatic discharge when absorbent concentration is 2.3%.

[0057] Using the above method, the ammonia content in the exhaust gas was reduced from 1800 mg / m³. 3 Reduced to 210 mg / m 3 The system meets or exceeds the GB16297-1996 Class II standard. Its resource recovery rate is 52 tons of 20% concentration ammonia water recovered daily, totaling 1378 tons annually, valued at 4.134 million yuan. Energy consumption is reduced compared to before the upgrade, saving 126,000 kWh of electricity annually, equivalent to 94,500 yuan in electricity costs. The total investment for the upgrade was 1.2 million yuan, with a payback period of approximately 2.3 months.

[0058] In summary, by employing the above-described technical solution of the present invention, the following effects can be achieved:

[0059] 1. This invention achieves a significant improvement in exhaust gas purification efficiency through optimized system structure and process design. It employs a single-tower integrated multi-stream exhaust gas treatment mode, combined with a polypropylene Pall ring packing layer and a gas-liquid distributor, enhancing the mass transfer effect of gas-liquid countercurrent contact. This greatly improves the ammonia removal efficiency in the exhaust gas, ensuring that the treated exhaust gas consistently meets environmental emission standards. This effectively solves the problem of excessive exhaust gas emissions in traditional processes, fundamentally reducing ammonia-containing gas pollution of the atmospheric environment.

[0060] 2. This invention utilizes the condensate from the existing purification process in the production process as the absorbent, eliminating the need for additional chemical agents, thus reducing operating costs and avoiding secondary pollution. Through the synergistic action of the circulating pump and the automated control system, precise circulation and concentration control of the absorbent are achieved, maximizing the recovery of ammonia resources from the exhaust gas and reducing raw material waste. Simultaneously, the system employs a low-power circulating pump and a high-efficiency packed tower design, significantly reducing energy consumption compared to traditional treatment processes. This improves resource utilization while significantly enhancing the economic efficiency and sustainability of the process.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Those skilled in the art, upon considering the disclosure in the specification and embodiments, will readily conceive of other embodiments of this disclosure. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the claims.

[0062] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. A urea storage tank tail gas venting and purification system, characterized in that, include: The exhaust gas absorption and scrubbing tank, the exhaust gas scrubbing circulation pump, and the supporting gas phase pipeline and liquid phase pipeline; The exhaust gas absorption and scrubbing tank is filled with polypropylene Pall ring packing, with a liquid distributor above the polypropylene Pall ring packing and a gas distributor below it. The gas phase pipeline includes: an emergency tank gas phase pipeline, a final condenser gas phase pipeline, a urine tank gas phase pipeline, a closed drain tank gas phase pipeline, a hydraulic jet outlet gas phase pipeline, and an ammonia tank gas phase pipeline. The emergency tank gas phase pipeline, the final condenser gas phase pipeline, the urine tank gas phase pipeline, the closed drain tank gas phase pipeline, the hydraulic jet outlet gas phase pipeline, and the ammonia tank gas phase pipeline are all connected to the lower part of the tail gas absorption and scrubbing tank. The liquid phase pipeline includes: a purification process condensate pipeline, an absorbent circulation pipeline, and an absorbent discharge pipeline. The purification process condensate pipeline is drawn from the dust replenishment pump of the granulation tower, spraying the condensate from the top of the tail gas absorption scrubbing tank to the liquid distributor. The absorbent circulation pipeline connects the bottom of the tail gas absorption scrubbing tank to the inlet of the tail gas scrubbing circulation pump, pressurizing the absorbent and sending it to the upper part of the tail gas absorption scrubbing tank for circulation absorption. When the ammonia concentration of the absorbent exceeds the threshold, the absorbent discharge pipeline discharges the absorbent into the ammonia water tank.

2. The urea storage tank tail gas venting and purification system according to claim 1, characterized in that, The gas phase pipelines for the emergency tank and the final condenser are made of 304 stainless steel, while the gas phase pipelines for the urine tank, the sealed drain tank, the hydraulic jet outlet, and the ammonia tank are made of carbon steel.

3. The urea storage tank tail gas venting and purification system according to claim 1, characterized in that, The exhaust gas absorption and scrubbing tank is equipped with an exhaust gas emission pipeline at the top, with a diameter of DN300 and made of carbon steel. An online ammonia concentration monitor is installed at the outlet.

4. The urea storage tank tail gas venting and purification system according to claim 1, characterized in that, Pneumatic regulating valves and electromagnetic flow meters are respectively installed on the gas phase pipelines of the accident tank, the final condenser, the urine tank, the sealed drain tank, the hydraulic jet outlet, and the ammonia tank.

5. The urea storage tank tail gas venting and purification system according to claim 1, characterized in that, The liquid distributor is a tray-type distributor, and the gas distributor is a perforated plate type distributor, with a gas-liquid contact area ≥ 200 m². 2 .

6. A method for purifying and treating urea storage tank tail gas, used in the treatment method of the urea storage tank tail gas venting and purification system according to any one of claims 1-5, characterized in that, Includes the following steps: Ammonia-containing tail gas generated from various storage tanks and equipment is collected and sent to the lower part of the tail gas absorption and scrubbing tank through a gas phase pipeline, with the total intake volume controlled at 300-500 m³ / h. 3 / h, the pneumatic regulating valves of each pipeline automatically adjust their opening degree according to the flow signal; The purified process condensate at a temperature of 20-30℃ is drawn from the dust makeup water pump of the granulation tower and pumped at a flow rate of 50-80m³. 3 A flow rate of / h is sprayed from the top of the exhaust gas absorption scrubbing tank, and comes into countercurrent contact with the exhaust gas flowing from bottom to top in the packing layer. Ammonia is absorbed through mass transfer, and the pH value of the scrubbing liquid is monitored in real time and controlled at 7-9. The absorbent liquid is pressurized by the exhaust gas washing circulation pump from the bottom of the exhaust gas absorption and washing tank, and then flows at a rate of 80-120 m³ / h. 3 A flow rate of / h is sent to the upper part of the washing tank for circulation absorption, and the concentration of circulating liquid ammonia is monitored online; When the concentration of circulating liquid ammonia exceeds 2%, the pneumatic discharge valve of the absorbent discharge pipeline is automatically opened to discharge the absorbent into the ammonia tank, while fresh purification process condensate is added to maintain the circulating liquid level. The treated exhaust gas is discharged through the top emission pipeline, and the ammonia content is ensured to be ≤225mg / m³ by an online ammonia concentration monitor. 3 .

7. The method for purifying and treating urea storage tank tail gas according to claim 6, characterized in that, Also includes: By controlling the flow rate and temperature of the condensate in the purification process, the gas-liquid ratio in the packing layer is maintained at 5-8:

1.

8. The method for purifying and treating urea storage tank tail gas according to claim 6, characterized in that, The pH value of the circulating fluid is adjusted by adding dilute sulfuric acid or ammonia.

9. The method for purifying and treating urea storage tank tail gas according to claim 6, characterized in that, The treated exhaust gas is discharged through the top discharge pipeline, including: real-time data linkage between the ammonia concentration online monitoring instrument and the gas phase pipeline intake volume; when the ammonia content of the exhaust gas approaches 225 mg / m3, the flow rate of the purification process condensate is automatically increased to 70-80 m3 / h.

10. The method for purifying and treating urea storage tank tail gas according to claim 6, characterized in that, The step of discharging the absorbent into the ammonia tank includes maintaining the ammonia temperature at 40-50°C using a heating coil inside the ammonia tank to reduce ammonia volatilization loss and improve recovery efficiency.

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