Simple and safe recovery system for residual ammonia gas

Abstract

The invention relates to the technical field of chemical engineering, in particular to a simple and safe ammonia residual gas recovery system which comprises a liquid ammonia storage tank (1), an accident ammonia absorption tower (2), a circulating pump set, a gas phase pipeline and a liquid phase pipeline, the circulating pump set comprises a circulating water pump, a compression pump and a waste heat recovery pump, the waste heat recovery pump is connected with a steam valve, and the liquid ammonia storage tank (1) is connected with a gasifier (11). The vaporizer (11) is connected with the buffer tank (12), the buffer tank (12) and the accident ammonia absorption tower (2) circulate pure ammonia gas through a gas phase pipeline, the accident ammonia absorption tower (2) and the liquid ammonia storage tank (1) circulate pure liquid ammonia through a liquid phase pipeline, the absorption tank (21) adsorbs exhaust gas detected by the accident ammonia absorption tower (2), and recovered nitrogen is used for purging the liquid ammonia storage tank (1), so that escape-free environment-friendly treatment and recycling of ammonia are realized.

Description

Technical Field

[0001] The invention relates to the technical field of chemical tanks, in particular to a simple and safe recovery system for residual ammonia gas. Background Art

[0002] Ammonia is an important chemical widely used in industrial production, and cryogenic liquid ammonia is a storage state commonly used in industrial and agricultural production, and is generally stored in special pressure vessels. When in use, it is converted into a gas in the use state through a set liquid-gas conversion supply system. But it is also a toxic and harmful gas, which has certain harm to the human body and the environment. It is irritating and corrosive to the eyes, nose, and skin, and can suffocate people. In the liquid ammonia liquid-gas conversion supply system, due to various working conditions such as system commissioning, abnormal safety valve start-up emissions, and tail gas emissions, more or less accidental ammonia emissions will be emitted. These accidental ammonia cannot be discharged directly into the atmosphere, which will cause pollution and harm to the surrounding environment and individuals. However, it cannot be simply diluted and discharged by discharging a pool, which also wastes precious resources. It should be comprehensively considered to absorb and recover it through specific devices. Compared with the liquid ammonia liquid-gas conversion supply system, the traditional ammonia recovery process not only has a high investment cost, but also has a complex process and high energy consumption, which is not suitable for such supply systems.

[0003] Therefore, a simple ammonia recovery system is developed to achieve the absorption of ammonia in the system and the liquid conversion of ammonia, so that it can be directly used in production after recovery. Summary of the invention

[0004] In order to achieve the above objectives, the present invention creates the following technical solutions:

[0005] A simple and safe recovery system for residual ammonia gas comprises a liquid ammonia storage tank 1, an accident ammonia absorption tower 2, a circulation pump group, a gas phase pipeline and a liquid phase pipeline, the circulation pump group comprises a circulating water pump, a compression pump and a waste heat recovery pump, the waste heat recovery pump is connected with a steam valve, the liquid ammonia storage tank 1 is connected to a vaporizer 11, the vaporizer 11 is connected to a buffer tank 12, the vaporizer 11 is connected to an accident ammonia absorption tower 2, the accident ammonia absorption tower 2 is connected to an absorption tank 21, the liquid ammonia storage tank 1, the vaporizer 11, the buffer tank 12 and the accident ammonia absorption tower 2 circulate ammonia through a gas phase pipeline, the accident ammonia absorption tower 2 and the liquid ammonia storage tank 1 circulate liquid ammonia through a liquid phase pipeline, the absorption tank 21 absorbs the exhaust gas detected by the accident ammonia absorption tower 2, and recovers nitrogen for purging the liquid ammonia storage tank 1.

[0006] The liquid ammonia in the liquid ammonia storage tank 1 is pressed to the vaporizer 11 by the pressure of the tank body itself. The vaporizer 11 is connected to the buffer tank 12 through a gas phase pipeline. When the pressure of the buffer tank 12 exceeds the set value, the system automatically introduces the remaining gas into the accident ammonia absorption tower 2; the vaporizer 11 is an electrically heated water bath gasifier, which vaporizes the liquid ammonia by heating in a hot water bath; the water bath is heated evenly to ensure that the liquid ammonia is completely vaporized, reducing the impact of residual liquid ammonia on subsequent processes.

[0007] The liquid ammonia storage tank 1 is provided with a booster pump 13, which is linked to the liquid ammonia inlet valve. Under normal working conditions, the liquid ammonia is pressed into the gasifier by the pressure in the storage tank. When the pressure in the storage tank is insufficient, the booster pump system is turned on to assist in pressurization to ensure continuous delivery of liquid ammonia.

[0008] The liquid ammonia storage tank 1 is connected to a compression pump. When the pressure in the liquid ammonia storage tank 1 is too high or the gas concentration is too high, the compression pump can directly extract the ammonia gas in the liquid ammonia storage tank 1 for freezing, liquefaction and reflux.

[0009] There is a water curtain spray system above the liquid ammonia storage tank 1, and the spray valve group switch is designed in the absorption area of ​​the accident ammonia absorption tower 2. In this ammonia treatment system, nitrogen purge can ensure the safety of the environment inside the equipment, while the water curtain spray handles the leaked or unabsorbed residual ammonia, forming a double protection.

[0010] The pipeline of the gasifier 11 is provided with a pressure regulating device and a temperature regulating device. The pressure transmitter monitors the downstream pressure in real time, adjusts the opening of the liquid ammonia inlet valve in linkage, controls the liquid ammonia flow entering the gasifier, and the temperature sensor monitors the temperature of the ammonia after gasification, and adjusts the power of the gasifier electric heater through the PID controller. The gasified ammonia first enters the ammonia buffer tank 12 for storage to balance the system pressure fluctuation. Then the ammonia is stabilized by the pressure regulating device and delivered to each end user to ensure safe and stable gas supply.

[0011] A gravity flow system is provided at the bottom of the buffer tank 12, and the gravity flow system returns the liquid at the bottom of the buffer tank 12 to the front end of the degasifier 11 for re-gasification and utilization.

[0012] The accident ammonia absorption tower 2 is provided with a microbubble cloud ammonia dissolution layer 21, an ammonia vapor distillation and purification layer 22, and a low-temperature cooling layer 23. Ammonia is absorbed by circulating water in the microbubble cloud dissolution layer 21 to form ammonia water, and undissolved ammonia rises to the ammonia vapor distillation and purification layer 22. The vaporizer 11 pipeline is connected to the steam valve and the waste heat recovery pump to provide a steam heat source for the ammonia vapor distillation and purification layer 22. The ammonia vapor enters the low-temperature cooling layer 23 after distillation and purification. After liquid ammonia is separated in the low-temperature cooling layer 23, it returns to the liquid ammonia storage tank 1 through the liquid phase pipeline. After ammonia is separated in the low-temperature cooling layer 23, it returns to the buffer tank 12.

[0013] The described microbubble cloud ammonia dissolution layer 21 is located below the ammonia vapor rectification and purification layer 22, and the low-temperature cooling layer 23 is located above the ammonia vapor rectification and purification layer 22. The low-temperature cooling layer 23 includes a partial condenser 24 and a cyclone demister 25; the microbubble cloud ammonia dissolution layer 21 is provided with a cyclone bubble generator 21-1 and a Venturi tube 21-2 at the bottom of the accident ammonia absorption tower 2, and the cyclone bubble generator 21-1 includes a control motor 21-3. This microbubble cloud ammonia dissolution layer solves the pain points of high ammonia escape rate, high energy consumption, and easy blockage in the traditional process through triple technologies of cyclone fragmentation + Venturi mixing + dynamic control.

[0014] The bottom of the described microbubble cloud ammonia dissolution layer 21 is provided with an inclined diversion bottom plate 26, and a water outlet 26-1 with an anti-vortex baffle is designed beside the diversion bottom plate 26.

[0015] The ammonia vapor rectification and purification layer 22 is provided with multiple trays 22-1 and multiple packing layers 22-2. Atomizing sprayers 22-3 are distributed on the trays 22-1. The atomizing sprayers 22-3 can spray the steam for waste heat recovery and atomized production water or circulating liquid. The packing layer 22-2 is filled with Pall rings. An alkali liquid inlet 22-4 and packing holes 22-5 are distributed on the packing layer 22-2. The alkali liquid inlet 22-4 and the packing holes 22-5 can be designed at the top and bottom of the ammonia vapor rectification and purification layer 22.

[0016] The low-temperature cooling layer 23 includes a cyclone demister 25. The cyclone demister 25 is provided with a cyclone plate 25-1. A reflux rail 25-2 is arranged outside the cyclone plate 25-1. An overflow port 25-3 is arranged on the reflux rail 25-2, and a drain port is arranged below the overflow port 25-3. The partial condenser 24 is provided with a reflux tank 24-1, and the drain port on the cyclone demister 25 is above the reflux tank 24-1.

[0017] The liquid ammonia storage tank 1, vaporizer 11, buffer tank 12, accident ammonia absorption tower 2, and absorption tank 21 are equipped with temperature transmitters, liquid level differential pressure transmitters, pressure controllers, and gas analyzers, and the information is fed back to the control system through 4-20ma signals.

[0018] When the control system detects that the ammonia concentration in the gas in the liquid ammonia storage tank 1 reaches a high value through online detection by the gas analyzer, the control system automatically starts the circulation pump to pump the liquid in the liquid ammonia storage tank 1 into the accident ammonia absorption tower 2, and at the same time, the control system opens the make-up water pipeline to supplement fresh water into the liquid ammonia storage tank 1.

[0019] When the control system detects that the ammonia concentration at the outlet of the accident ammonia absorption tower 2 reaches the high value, it opens the makeup water valve and the steam valve to supply water vapor to the accident ammonia absorption tower 2, and opens the bypass of the pump outlet to pump the circulating liquid at the bottom of the microbubble cloud ammonia dissolution layer 21 into the inner packaging of the ammonia water recovery barrel for sealing;

[0020] The control system compares the preset temperature value with the temperature transmitter signal received. When the temperatures of the ammonia vapor rectification and purification layer 22 and the low-temperature cooling layer 23 are higher than the set value, the control system will issue an instruction to increase the flow rate of the cooling medium in the low-temperature cooling layer 23, strengthen the cooling of the rising ammonia vapor, reduce the temperature of the ammonia vapor rectification and purification layer 22, and at the same time adjust the steam parameters in the ammonia vapor rectification and purification layer 22 to optimize the rectification process and indirectly affect the temperature.

[0021] When the pressure of the ammonia vapor rectification and purification layer 22 fed back by the pressure controller is higher than the set value, the control system will appropriately discharge the liquid in the container based on the liquid level information provided by the comprehensive liquid level differential pressure transmitter. The control system will also adjust the flow rate of the ammonia residue gas and the steam flow rate entering the accident ammonia absorption tower 2 according to the feedback of the pressure controller, reduce the ammonia vapor inflow, and can also adjust the cooling effect of the low-temperature cooling layer 23 to condense the ammonia vapor into liquid ammonia more quickly and reduce the gas volume in the tower;

[0022] When the pressure of the low-temperature cooling layer 23 fed back by the pressure controller is too high, the control system adjusts the flow rate of the cooling medium, controls the ammonia vapor condensation speed, and adjusts the flow rate of the ammonia residue gas and the steam flow rate entering the accident ammonia absorption tower 2 to balance the pressure.

[0023] Furthermore, a water pipe can be connected to the filler hole 22-5 for cleaning the filler layer 22-2.

[0024] Furthermore, the structure of the filler layer 22-2 is designed as a conical flanging metal cascade ring. The filler layer 22-2 not only serves as a filler load-bearing structure (preventing the filler from sinking and deforming), but also guides the gas to rise evenly through the opening design to avoid the decline of the absorption efficiency caused by local gas flow concentration.

[0025] Furthermore, an arched bottom support member for increasing the ventilation area is designed on the multi-layer tray 22-1. While ensuring the load-bearing capacity, the arched structure increases the bottom opening rate to more than 40%, reduces the local resistance of the airflow, avoids the collapse and deformation of the packing layer, and adapts to the impact load of high-concentration ammonia gas. At the same time, the Pall metal rings in the packing layer 22-2 cooperate with the arched bottom support member to make the gas rise evenly, avoiding "hot spots" or "dead zones" caused by local airflow concentration, and reducing the fluctuation of ammonia absorption efficiency to within ±2%. The high porosity (>95%) of the Pall metal rings in the packing layer 22-2 and the guiding effect of the arched bottom support member enable solid particles or crystallized substances to be discharged with the airflow, extending the continuous operation period of the ammonia vapor rectification and purification layer 22 equipment to more than 3 years.

[0026] Furthermore, multiple sets of the atomizing sprayers 22-3 are designed and evenly distributed in the packing layer 22-2. Ensure that the absorption liquid is evenly sprayed onto the packing surface, avoid "channeling" or "dry zones", and increase the gas-liquid contact area.

[0027] Furthermore, the inclined surface design of the flow guiding bottom plate 26 can guide the liquid at the bottom of the tower to quickly gather at the discharge port, avoid the formation of dead zones due to local liquid accumulation, reduce the risk of deposition of crystallized substances or particulate matters, and at the same time reduce the probability of bottom corrosion. At the same time, the inclined surface structure of the flow guiding bottom plate 26 can also guide the uniform distribution of the upward airflow, reduce the disturbance of the gas eddy to the bottom liquid layer, and improve the gas-liquid separation efficiency.

[0028] Furthermore, the anti-vortex baffle 26-1 is designed with a special shape (such as a spiral flow guiding vane or a honeycomb partition) to break the rotational trend of the liquid flow, convert the vortex energy into laminar flow, reduce the liquid level fluctuation and bubble entrainment, and combine the inclined surface flow guiding and vortex suppression of the flow guiding bottom plate 26 to achieve the unity of efficient discharge, stable operation and low-cost maintenance. Compared with the traditional flat-bottom tower structure, its liquid discharge efficiency is increased by about 30%, and the pumping energy consumption is reduced by 10% - 15%. It is especially suitable for ammonia absorption scenarios with high corrosiveness and easy crystallization.

[0029] Furthermore, the circulating water pump is a canned motor pump, and the circulating water pump is provided with a pump outlet bypass connected to the ammonia water recovery tank. The bypass return liquid of the pump outlet bypass can be linked with the built-in cooling cycle of the canned motor pump, and the coolant flow can be optimized by adjusting the bypass valve opening to ensure the motor temperature rise and extend the equipment life.

[0030] Furthermore, the waste heat recovery pump recovers the heat energy generated during the gasification of the vaporizer 11, the low-temperature cooling layer 23, and the gasification and compression of the liquid ammonia storage tank 1, and supplies heat to the ammonia vapor rectification and purification layer 22.

[0031] Furthermore, the absorption tank 21 can also recover and temporarily store the leaked liquid ammonia or spray liquid in the accident state to prevent secondary pollution.

[0032] Furthermore, the control system dynamically optimizes the flow rate and pump speed according to real-time data (temperature, liquid level, concentration, pressure). When the control system detects abnormal liquid level pressure difference (such as a sudden increase in pressure difference), it can give an early warning of the blockage of the packing layer and trigger the cleaning program. When the temperature is abnormal, the cooling system is started, and an ammonia monitoring plan is formed in combination with the gas analyzer, thus forming a complete fault handling chain. The control system forms a triple monitoring network based on the temperature transmitters and liquid level pressure difference transmitters equipped in the liquid ammonia storage tank 1 and the accident ammonia absorption tower 2, in combination with the ammonia concentration analyzer. Temperature monitoring can identify overheating of the absorption liquid or cooling failure, the liquid level pressure difference reflects the risk of packing layer blockage, and the concentration data is directly related to the absorption efficiency, ensuring a full-range perception of the system operation status.

[0033] The beneficial effects of the improved technical solution are as follows:

[0034] This system simplifies the multi-stage absorption structure into a single-stage absorption, deeply integrates modular design and intelligent control, and forms a triple monitoring network through temperature, pressure, liquid level, and concentration sensors. Each functional layer is independently set, facilitating later upgrading and transformation.

[0035] This system realizes the supply and recycling of energy during the cyclic conversion of liquid ammonia and ammonia gas, achieving good economic benefits. The absorption tank recovers nitrogen for purging the liquid ammonia storage tank, and the water curtain spray treats the leaked ammonia gas to form a double protection. The waste heat recovery system recovers the hot water from the vaporizer and the hot gas from the compression pump to convert the heat energy into steam heat source.

[0036] The swirling bubble generator and Venturi tube at the bottom dissolution layer generate a microbubble cloud, significantly increasing the gas-liquid contact area and improving the ammonia dissolution efficiency. The diversion bottom plate at the bottom of the dissolution layer further optimizes the gas-liquid flow path and reduces the dead zone. High-concentration crude ammonia water is obtained at the bottom of the dissolution layer.

[0037] The combined design of multiple trays and Pall metal ring packings in the ammonia vapor rectification and purification layer, combined with the uniform distribution of the atomizing sprayer, and the recovery system recovers low-temperature waste heat through the phase change and compression processes, rather than directly using steam heat for atomization. This realizes a comprehensive improvement in ammonia recovery efficiency, economy, and safety. At the same time, steam heat extraction improves the rectification efficiency, the ammonia purity can reach over 99%, and the load adaptation range is expanded to 50% - 120% of the design value.

[0038] The partial condenser and cyclone demister between the low-temperature cooling layers can accurately separate gas and liquid. The cyclone demister rotates at the top, forming a tornado-like upward vortex system in the accident ammonia absorption tank, enabling the ammonia water vapor not recovered in the dissolution layer to enter the subsequent rectification and purification layer. The residual ammonia gas is separated by steam heating, and the purified liquid ammonia returns to the storage tank, forming a resource closed-loop, further improving the separation efficiency and reducing energy consumption. Description of the Drawings

[0039] Figure 1 This is the system flow chart of the present invention.

[0040] Figure 2 This is the control system diagram of the liquid ammonia storage tank of the present invention.

[0041] Figure 3 This is the control system diagram of the accident ammonia absorption tower of the present invention.

[0042] Figure 4 This is the schematic diagram of the microbubble cloud ammonia dissolution layer of the present invention.

[0043] Figure 5 This is the schematic diagram of the structure of the low-temperature cooling layer of the present invention.

[0044] Figure 6 This is the structure diagram of the accident ammonia absorption tower of the present invention.

[0045] Figure 7 This is the diagram of the control module of the present invention.

[0046] Figure 8 This is the schematic diagram of the structure of the filled Pall rings Figure 1 .

[0047] Figure 9 This is the schematic diagram of the structure of the filled Pall rings Figure 2 . Detailed implementation manners

[0048] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below with reference to the accompanying drawings. The description in this part is only exemplary and explanatory, and should not have any restrictive effect on the protection scope of the present invention.

[0049] Generally, traditional ammonia recovery processes mainly include the following methods: Adsorption method: Adsorb ammonia in the air through adsorbents such as activated carbon and collect and store it. Distillation method: Distill the ammonia-containing aqueous solution and collect the escaped ammonia. Freezing method: Convert ammonia in the air into liquid state by cooling and collect the liquid ammonia. Combustion method: Burn ammonia into nitrogen and water, and then collect water through cooling to obtain pure nitrogen. Adsorbent regeneration method: Regenerate the adsorbent adsorbed with ammonia, so as to recover the collected ammonia into pure ammonia. Chemical absorption method: Dissolve ammonia in the air in a chemical absorbent, and then collect ammonia through reaction. Microbial method: Use specific microorganisms to convert ammonia into other useful substances and collect and store the products. Acid absorption method: Use an acid absorbent to absorb ammonia and transfer ammonia into the absorbent solution for removal. Water absorption method: Ammonia is highly soluble in water, and ammonia can be recovered by heating or adding quicklime. Catalytic combustion decomposition method: Decompose ammonia into hydrogen and nitrogen through heating in a catalyst bed, and then react with oxygen in the air to burn ammonia into nitrogen and water vapor. These methods have their own advantages and disadvantages, and the selection of a suitable method needs to be evaluated according to specific circumstances. For example, the adsorption method is suitable for small-scale treatment, while the chemical absorption method and the acid absorption method are suitable for large-scale industrial applications. Although the catalytic combustion decomposition method has a relatively high equipment investment, it can effectively treat a large amount of ammonia.

[0050] However, for the liquid ammonia liquid-gas conversion supply system, the above ammonia recovery processes not only have high investment costs, but also are complex in process and large in energy consumption, and are not applicable to such supply systems.

[0051] Therefore, a simple and safe ammonia recovery system is developed. This system realizes the efficient recovery and recycling of ammonia through multi-stage physical and chemical treatments (gasification, absorption, rectification, cooling), and has the characteristics of safety, environmental protection and economy. Its core advantages lie in the integration of waste heat recovery, microbubble absorption and closed-loop design, breaking through the bottlenecks of high energy consumption and secondary pollution in traditional processes. And through automatic control of circulating water replenishment, waste heat recovery and liquid replacement, the equipment investment and energy consumption are effectively reduced. Compared with the high investment cost of traditional pickling or membrane processes, this design is more applicable.

[0052] Specifically, such as Figures 1-7As shown in the figure, a simple and safe ammonia waste gas recovery system includes a liquid ammonia storage tank 1, an accident ammonia absorption tower 2, a circulation pump group, a gas-phase pipeline, and a liquid-phase pipeline. The circulation pump group includes a circulating water pump, a compression pump, and a waste heat recovery pump. A steam valve is connected to the waste heat recovery pump. The liquid ammonia storage tank 1 is connected to a vaporizer 11, the vaporizer 11 is connected to a buffer tank 12, the vaporizer 11 is connected to the accident ammonia absorption tower 2, and the liquid ammonia storage tank, the vaporizer 11, the buffer tank 12, and the accident ammonia absorption tower 2 are circulated through the gas-phase pipeline. The accident ammonia absorption tower 2 and the liquid ammonia storage tank 1 are circulated through the liquid-phase pipeline;

[0053] An absorption tank 21 is designed behind the accident ammonia absorption tower 2. The absorption tank 21 absorbs the inert gas processed by the accident ammonia absorption tower 2, and nitrogen can be obtained to purge the liquid ammonia storage tank 1.

[0054] The liquid ammonia in the liquid ammonia storage tank 1 is pressured to the vaporizer 11 by the self-pressure of the tank body. The vaporizer 11 is connected to the buffer tank 12 through the gas-phase pipeline. When the pressure of the buffer tank 12 exceeds the set value, the system automatically introduces the waste gas into the accident ammonia absorption tower 2; the vaporizer 11 is an electric heating water bath type vaporizer, and the liquid ammonia is vaporized by heating through a hot water bath.

[0055] A microbubble cloud ammonia gas dissolution layer 21, an ammonia vapor rectification and purification layer 22, and a low-temperature cooling layer 23 are arranged in the accident ammonia absorption tower 2. The ammonia gas is absorbed by the circulating water in the microbubble cloud dissolution layer 21 to form ammonia water. The un-dissolved ammonia gas rises to the ammonia vapor rectification and purification layer 22. After the ammonia vapor is rectified and purified, it enters the low-temperature cooling layer 23. In the low-temperature cooling layer 23, the separated liquid ammonia returns to the liquid ammonia storage tank 1 through the liquid-phase pipeline, and the separated ammonia gas returns to the buffer tank 12.

[0056] The hot water after the vaporizer 11 is used is connected to the steam valve. The waste heat recovery pump recovers the hot gas of the compression pump. The hot water and the hot gas are mixed and together provide a steam heat source for the ammonia vapor rectification and purification layer 22 through the steam valve. This step fully recovers the heat source of the system itself to heat the ammonia water solution to separate ammonia gas and impurities, realizing the internal circulation supply of the system without the need to add additional equipment.

[0057] The microbubble cloud ammonia gas dissolution layer 21 is located below the ammonia vapor rectification and purification layer 22, the low-temperature cooling layer 23 is located above the ammonia vapor rectification and purification layer 22, and the low-temperature cooling layer 23 includes a partial condenser 24 and a cyclone demister 25. A reflux groove 24-1 is arranged on the partial condenser 24, which can recycle the reflux dripping liquid of the cyclone demister 25.

[0058] The waste heat recovery pump is connected to the low-temperature cooling layer 23 to absorb the heat during ammonia vapor separation and the heat in the compressed pump gas step, and combines with the water heated by the vaporizer 11 to generate low-pressure steam. The steam is supplied to the ammonia vapor rectification and purification layer 22 for the purification of ammonia gas, and at the same time, an automatic convection circulation system with warm and humid lower layer and dry and cold upper layer is formed in the tank.

[0059] The microbubble cloud ammonia gas dissolution layer 21 is located at the bottom of the accident ammonia absorption tower 2, equipped with a swirl bubble generator 21-1 and a Venturi tube 21-2. There is an inclined diversion bottom plate 26 at the bottom of the microbubble cloud ammonia gas dissolution layer 21, and a water outlet 26-1 with an anti-vortex baffle is designed beside the diversion bottom plate 26. The swirl bubble generator 21-1 includes a control motor 21-3. Driven by the control motor 21-3, water or ammonia water is mixed with ammonia gas to form microbubbles. This significantly improves the gas-liquid contact efficiency and effectively reduces bottom crystallization at the same time; the inclined design (30° - 45°) of the diversion bottom plate 26 cooperates with the anti-vortex baffle to prevent particulate matter from accumulating in the swirl area. At the same time, the inclined structure of the diversion bottom plate 26 can also guide the uniform distribution of the rising gas flow, reduce the disturbance of the gas vortex to the bottom liquid layer, and improve the gas-liquid separation efficiency.

[0060] The ammonia vapor rectification and purification layer 22 is provided with multiple trays 22-1 and multiple packing layers 22-2. Atomizing sprayers 22-3 are arranged on the trays 22-1. The atomizing sprayers 22-3 can be designed at the top and bottom of the ammonia vapor rectification and purification layer 22. The atomizing sprayers 22-3 are designed in multiple groups and are evenly distributed in the packing layer 22-2. This ensures that the absorption liquid is evenly sprayed onto the packing surface, avoids "channeling" or "dry areas", and increases the gas-liquid contact area.

[0061] An alkali liquid inlet 22-4 and packing holes 22-5 are distributed on the packing layer 22-2. The alkali liquid inlet 22-4 and the packing holes 22-5 can be designed at the top and bottom of the ammonia vapor rectification and purification layer 22. Water pipes can be connected to the packing holes 22-5 for cleaning the packing layer 22-2. The packing layer 22-2 is filled with Pall metal rings with a tapered flanged metal stepped ring structure. The packing layer 22-2 not only serves as a packing load-bearing structure (preventing the packing from sinking and deforming), but also guides the uniform rise of gas through the opening design, avoiding the decrease in absorption efficiency caused by local gas flow concentration. The packing parameters of the tapered flanged Pall metal ring are designed as shown in Table 1 below, and the dimensional structure parameters are designed as shown in Table 2 and Figure 8 and 9 as shown.

[0062] Table 1 Characteristic Parameters of Tapered Flanged Pall Metal Ring Packing

[0063] Table 2 Dimensional Parameters of Tapered Flanged Pall Metal Ring Packing

[0064] The multi-layer tray 22-1 is designed with an arched bottom support that can increase the ventilation area. While ensuring the load-bearing capacity, the arched structure increases the bottom opening rate to more than 40%, reduces the local resistance of the airflow, avoids the collapse and deformation of the packing layer, and adapts to the impact load of high-concentration ammonia gas. At the same time, the Pall rings in the packing layer 22-2 cooperate with the arched bottom support to make the gas rise evenly, avoiding "hot spots" or "dead zones" caused by local airflow concentration, and reducing the fluctuation of ammonia absorption efficiency to within ±2%. The high porosity (>95%) of the Pall rings in the packing layer 22-2 and the guiding effect of the arched bottom support allow solid particles or crystallized substances to be discharged with the airflow, extending the continuous operation period of the ammonia steam rectification and purification layer 22 equipment. The packing hole 22-5 has an open-top structure with a wound sealing gasket, increasing the sealing degree of the ammonia steam rectification and purification layer 22 to prevent ammonia gas escape.

[0065] The lye inlet 22-4 can improve the purity of ammonia gas and the stability of the rectification and purification system in the ammonia steam rectification and purification layer 22. Ammonia gas often contains , and other acidic gases. The lye contacts the gas phase countercurrently through the packing layer and undergoes a neutralization reaction: . The sulfates, thiocyanates, etc. generated by the reaction dissolve in the liquid phase, preventing acidic substances from entering the partial condenser section to form ammonium salt crystals (such as ) and causing pipeline blockages. The lye can also increase the pH to 10-12, promoting the dissociation of into , increasing the concentration of gaseous ammonia and improving the rectification efficiency.

[0066] The cyclone demister 25 is equipped with a cyclone plate 25-1 driven by a motor. There is a reflux rail 25-2 outside the cyclone plate 25-1, and an overflow port 25-3 is provided on the reflux rail 25-2. A drain port is provided below the overflow port 25-3 and is connected to the reflux channel 24-1 of the partial condenser 24. The partial condenser 24 is designed with cooling water inlet and outlet, and the purified ammonia steam in the ammonia steam rectification and purification layer 22 can be preliminarily cooled by circulating cooling water in the shell side. The cyclone plate 25-1 of the cyclone demister 25 uses centrifugal force to throw the uncondensed ammonia mist droplets towards the tower wall. The liquid ammonia converges along the reflux rail 25-2 to the overflow port 25-3, and the liquid ammonia collected by the overflow port 25-3 flows into the reflux channel 24-1 of the partial condenser 24 through the drain port and is discharged together with the circulating condensed water. The qualified gas phase then circulates upward into the buffer tank 12 or the absorption tank 21. The low-temperature cooling layer 23 is designed with a cascading process of partial condensation - cyclone demisting - reflux - partial condensation, achieving efficient recovery of liquid ammonia. The partial condenser 24 separates high-concentration liquid ammonia through circulating cooling and condensation, and the cyclone demisting further purifies it to industrial grade standards. At the same time, the cyclone demister 25 rotates at the top to more fully drive the water vapor in the lower layer to rise, further improving the working efficiency of the accident ammonia absorption tower 2.

[0067] The liquid ammonia storage tank 1, the vaporizer 11, the buffer tank 12, the accident ammonia absorption tower 2, and the absorption tank 21 are equipped with a temperature transmitter, a liquid level pressure difference transmitter, a pressure controller, and a gas analyzer, which feed back information to the control system through a 4-20ma signal. When the gas analyzer detects that the ammonia concentration of the gas in the liquid ammonia storage tank 1 reaches a high value online, the control system automatically starts the circulation pump to extract the gas in the liquid ammonia storage tank 1 into the accident ammonia absorption tower 2, and at the same time, the control system starts the water supply pipeline to replenish fresh water into the liquid ammonia storage tank 1;

[0068] When the control system detects that the ammonia concentration at the outlet of the accident ammonia absorption tower 2 reaches a high value, the water supply valve and the steam valve are opened to replenish water vapor to the accident ammonia absorption tower 2, and the pump outlet bypass is opened to pump the circulating liquid at the bottom of the microbubble cloud ammonia solution layer 21 into the ammonia recovery barrel for packaging and sealing;

[0069] The control system compares the preset temperature value with the received temperature transmitter signal. If the temperature of the ammonia vapor distillation and purification layer 22 and the low-temperature cooling layer 23 is higher than the set value, the control system will issue an instruction to increase the cooling medium flow of the low-temperature cooling layer 23, strengthen the cooling of the rising ammonia vapor, and reduce the temperature of the ammonia vapor distillation and purification layer 22. At the same time, the steam parameters in the ammonia vapor distillation and purification layer 22 are adjusted to optimize the distillation process, which indirectly affects the temperature.

[0070] When the pressure of the ammonia vapor distillation and purification layer 22 fed back by the pressure controller is higher than the set value, the control system discharges the liquid in the container appropriately based on the liquid level information provided by the liquid level differential pressure transmitter. The control system also adjusts the ammonia residual gas flow and steam flow entering the accident ammonia absorption tower 2 according to the feedback of the pressure controller to reduce the amount of ammonia vapor entering. It can also adjust the cooling effect of the low-temperature cooling layer 23 to condense the ammonia vapor into liquid ammonia more quickly and reduce the amount of gas in the tower.

[0071] When the pressure of the low-temperature cooling layer 23 fed back by the pressure controller is too high, the control system adjusts the cooling medium flow, controls the ammonia vapor condensation rate, and adjusts the ammonia residual gas flow and steam flow entering the accident ammonia absorption tower 2 to balance the pressure.

[0072] The gasifier 11 is also equipped with a pressure transmitter and a temperature sensor. The pressure transmitter monitors the downstream pressure in real time, adjusts the opening of the liquid ammonia inlet valve in conjunction with the flow of liquid ammonia into the gasifier, and the temperature sensor monitors the temperature of the ammonia after gasification, and adjusts the power of the gasifier electric heater through the PID controller.

[0073] A booster pump 13 is provided on the liquid ammonia storage tank 1, and the booster pump 13 is linked with the liquid ammonia inlet valve to ensure the continuity of liquid supply. The liquid ammonia storage tank 1 is also connected to a compression pump, and the compression pump directly freezes and liquefies the gasified ammonia gas in the liquid ammonia storage tank 1 to achieve simple recovery.

[0074] Furthermore, the circulating water pump is a canned motor pump, and a bypass connection to the ammonia recovery tank is provided at the pump outlet. The bypass return liquid of the pump outlet bypass can be linked with the built-in cooling cycle of the canned motor pump. By adjusting the bypass valve opening, the coolant flow rate can be optimized to ensure the motor temperature rise and extend the equipment life.

[0075] Furthermore, the control system dynamically optimizes the flow rate and pump speed according to real-time data (temperature, liquid level, concentration, pressure). When the control system detects abnormal liquid level pressure difference (such as a sudden increase in pressure difference), it can give an early warning of the blockage of the packing layer and trigger the cleaning program. When the temperature is abnormal, the cooling system is started. Combined with a gas analyzer, an ammonia monitoring plan is formed, and then a complete fault handling chain is formed. The control system forms a triple monitoring network based on the temperature transmitters and liquid level pressure difference transmitters equipped on the liquid ammonia storage tank 1 and the accident ammonia absorption tower 2, combined with an ammonia concentration analyzer. Temperature monitoring can identify overheating of the absorption liquid or cooling failure, the liquid level pressure difference reflects the risk of packing layer blockage, and the concentration data is directly related to the absorption efficiency to ensure a full-range perception of the system operation status.

[0076] Furthermore, referring to the system process Figure 1 and 3 An absorption tank 21 at the tail of the gas outlet of the accident ammonia absorption tower 2 absorbs inert gases , and 5% - 10% dilute sulfuric acid (or hydrochloric acid, adsorbent, etc.) can be used in the absorption tank 21 to neutralize the residual ammonia, and the reaction equation for generating ammonium sulfate (or ammonium chloride) is: , when the exhaust gas passes through the absorption tank 21, ammonia is captured by the adsorbent, and nitrogen directly passes through due to its inertness, achieving physical separation.

[0077] Furthermore, a filter can also be provided on the recovery pipe of the ammonia recovery tank to remove particulate impurities and metal ions and improve the purity of the recovered ammonia water.

[0078] Furthermore, when purging the liquid ammonia storage tank 1 with nitrogen, a water curtain spray can be added above the liquid ammonia storage tank 1, especially in a special environment, especially when the ambient temperature is high in summer. The spray valve group switch is designed in the absorption area of the accident ammonia absorption tower 2.

[0079] Furthermore, a gravity flow system is provided at the bottom of the buffer tank 12. When the ambient temperature is relatively low, liquid will accumulate at the bottom of the buffer tank 12, and the gravity flow system returns the liquid to before the vaporizer 11 for re-vaporization and utilization.

[0080] The operation sequence of this ammonia residual gas safety recovery system is as follows:

[0081] Liquid usage method: Liquid ammonia storage tank 1 → Vaporizer 11 (electrical heating for water vaporization) → Buffer tank 12 (pressure stabilization) → End user (ammonia-using equipment).

[0082] Liquid ammonia is pumped by the pressure of its own storage tank (when its own pressure is insufficient, the booster pump system can be started) to the electric heating water bath vaporizer. The pressure on the gas-phase ammonia pipeline automatically regulates the liquid ammonia flow rate entering the vaporizer, and the thermometer on the gas-phase ammonia pipeline automatically regulates the power of the electric heater of the vaporizer, so as to ensure that the ammonia gas flow rate (≤60 Nm³ / h, w) leaving the vaporizer is within the control index range, enters the ammonia buffer tank for storage, and then is sent to each terminal through the pressure regulating device.

[0083] Recovery process: Ammonia gas leaked from liquid ammonia storage tank 1, buffer tank 12 or the system → accident ammonia absorption tower 2 (absorption → purification → liquefaction) → the recovered liquid ammonia returns to storage tank 1 → absorption tank 21 recovers nitrogen to purge liquid ammonia storage tank 1; uncondensed ammonia gas → returns to buffer tank 12 for circulation.

[0084] The materials processed by the accident ammonia absorption tower are the relief gases from the safety valves of the liquid ammonia tank and ammonia buffer tank, the liquid ammonia unloading, the purge and replacement gases of pipelines and equipment, etc. The processing capacity is about 704.23 kg / h. The qualified gas after treatment is discharged from the top of the tower or recycled to the buffer tank. The ammonia gas spray liquid after preliminary dissolution and absorption at the bottom layer of the accident ammonia absorption tower is pumped away by a pump for barrel filling and circulated for treatment. The coolant after rectification and purification is pumped back to the liquid ammonia storage tank. When the treatment of the accident ammonia absorption tower is unqualified due to too much mixed gas, the absorption tank is used to further adsorb and separate gases such as water vapor, residual ammonia gas, and carbon dioxide in the tail gas, and the separated inert gas is left for recycling.

[0085] It should be noted that in this article, the terms "including", "comprising" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0086] Specific examples are used in this article to elaborate on the principles and implementation manners of the present invention. The description of the above examples is only used to help understand the method and its core idea of the present invention. The above is only the preferred implementation manner of the present invention. It should be noted that due to the limitation of literal expression, objectively there are infinite specific structures. For those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements, modifications or changes can also be made, or the above technical features can be combined in an appropriate manner; these improvements, modifications, changes or combinations, or directly applying the concept and technical solution of the invention to other occasions without improvement, shall all be regarded as the protection scope of the present invention.

Claims

1. A simple and safe ammonia residue gas recovery system, comprising a liquid ammonia storage tank (1), an accident ammonia absorption tower (2), a circulating pump group, a gas-phase pipeline and a liquid-phase pipeline. The circulating pump group includes a circulating water pump and a compression pump. The compression pump is connected to a waste heat recovery pump, and a steam valve is connected to the waste heat recovery pump. It is characterized in that: The described liquid ammonia storage tank (1) is connected to a vaporizer (11), and the vaporizer (11) is connected to a buffer tank (12). The liquid ammonia storage tank (1), vaporizer (11), buffer tank (12) and the accident ammonia absorption tower (2) circulate ammonia gas through a gas-phase pipeline. The accident ammonia absorption tower (2) and the liquid ammonia storage tank (1) circulate liquid ammonia through a liquid-phase pipeline. The accident ammonia absorption tower (2) is connected to an absorption tank (21), and the absorption tank (21) adsorbs the exhaust gas detected by the accident ammonia absorption tower (2), and then recovers nitrogen gas for purging the liquid ammonia storage tank (1); The liquid ammonia in the liquid ammonia storage tank (1) is pressed to the vaporizer (11) by the self-pressure of the tank body. The vaporizer (11) is an electric heating water bath type vaporization. The vaporizer (11) is connected to the buffer tank (12) through a gas-phase pipeline. When the pressure in the buffer tank (12) exceeds the set value, the system automatically introduces ammonia gas into the accident ammonia absorption tower (2); A microbubble cloud ammonia gas dissolution layer (21), an ammonia vapor rectification and purification layer (22), and a low-temperature cooling layer (23) are provided in the accident ammonia absorption tower (2). Ammonia gas is absorbed by circulating water in the microbubble cloud dissolution layer (21) to form ammonia water. The un-dissolved ammonia gas rises to the ammonia vapor rectification and purification layer (22). The vaporizer (11) is connected to a steam valve and, together with a waste heat recovery pump, provides a steam heat source for the ammonia vapor rectification and purification layer (22). After the ammonia vapor is rectified and purified, it enters the low-temperature cooling layer (23). After separating pure liquid ammonia in the low-temperature cooling layer (23), it returns to the liquid ammonia storage tank (1) through a liquid-phase pipeline. After separating pure ammonia gas in the low-temperature cooling layer (23), it returns to the buffer tank (12).

2. The simple and safe ammonia residual gas recovery system according to claim 1, characterized in that: The microbubble cloud ammonia gas dissolution layer (21) is located at the bottom of the accident ammonia absorption tower (2). An inclined diversion bottom plate (26) is provided at the bottom of the microbubble cloud ammonia gas dissolution layer (21). A swirl bubble generator (21-1) and a Venturi tube (21-2) are also provided on the microbubble cloud ammonia gas dissolution layer (21). The low-temperature cooling layer (23) includes a partial condenser (24) and a swirl demister (25).

3. The simple and safe ammonia tail gas recovery system according to claim 1, characterized in that: Multiple trays (22-1) and multiple packing layers (22-2) are provided in the ammonia vapor rectification and purification layer (22). An arched bottom support is provided on the tray (22-1). Pall rings are filled on the packing layer (22-2). A lye inlet (22-4) and packing holes (22-5) are distributed on the packing layer (22-2).

4. The simple and safe ammonia residual gas recovery system according to claim 2, characterized in that: A swirl plate (25-1) is provided on the swirl demister (25). A reflux rail (25-2) is provided outside the swirl plate (25-1). An overflow port (25-3) is provided on the reflux rail (25-2). A drain port is provided below the overflow port (25-3). A reflux trough (24-1) is provided on the partial condenser (24). The drain port on the swirl demister (25) is above the reflux trough (24-1).

5. The simple and safe ammonia tail gas recovery system according to claim 1, characterized in that: A water curtain spraying system is provided above the liquid ammonia storage tank (1). The design of the water curtain spraying system is within the absorption area of the accident ammonia absorption tower (2).

6. The simple and safe ammonia residual gas recovery system according to claim 1, characterized in that: A gravity flow system is provided between the vaporizer (11) and the buffer tank (12) to return the liquid ammonia at the bottom of the buffer tank (12) to the vaporizer (11) for re-vaporization.

7. The simple and safe ammonia residual gas recovery system according to claim 1, characterized in that: The liquid ammonia storage tank (1) is connected to a booster pump (13), and the booster pump (13) is linked with the liquid ammonia inlet valve. The liquid ammonia storage tank (1) is also connected to a compression pump, and the compression pump directly recovers the ammonia gas vaporized from the liquid ammonia storage tank (1) by freezing and liquefying it back into the liquid ammonia storage tank (1).

8. The simple and safe ammonia residual gas recovery system according to claim 1, wherein: Temperature transmitters, liquid level differential pressure transmitters, pressure controllers, and gas analyzers are installed on the liquid ammonia storage tank (1), vaporizer (11), buffer tank (12), accident ammonia absorption tower (2), and absorption tank (21). Information is fed back to the control system via 4 - 20 mA signals. When the control system detects, through on-line detection by the gas analyzer, that the ammonia gas concentration in the gas within the liquid ammonia storage tank (1) reaches a high value, the control system turns on the circulation pump to extract the gas within the liquid ammonia storage tank (1) into the accident ammonia absorption tower (2). At the same time, the control system turns on the make-up water pipeline to supplement fresh water into the liquid ammonia storage tank (1). When the control system detects that the ammonia gas concentration at the outlet of the accident ammonia absorption tower (2) reaches a high value, it turns on the make-up water valve and steam valve to supplement water vapor into the accident ammonia absorption tower (2), and turns on the pump outlet bypass to pump the circulating liquid at the bottom of the micro-bubble cloud ammonia gas dissolution layer (21) into the ammonia water recovery barrel for packaging and sealing. The control system compares the preset temperature value with the signal received from the temperature transmitter. When the temperatures of the ammonia vapor rectification and purification layer (22) and the low-temperature cooling layer (23) are higher than the set value, the control system issues an instruction to increase the flow rate of the cooling medium in the low-temperature cooling layer (23) to strengthen the cooling of the rising ammonia vapor and reduce the temperature of the ammonia vapor rectification and purification layer (22). At the same time, the steam parameters within the ammonia vapor rectification and purification layer (22) are adjusted to optimize the rectification process, indirectly affecting the temperature. When the pressure in the ammonia vapor rectification and purification layer (22) fed back by the pressure controller is higher than the set value, the control system appropriately discharges the liquid in the container based on the liquid level information provided by the liquid level differential pressure transmitter. The control system also adjusts the flow rates of the ammonia residual gas and steam entering the accident ammonia absorption tower (2) according to the feedback from the pressure controller to reduce the amount of ammonia vapor entering. It can also adjust the cooling effect of the low-temperature cooling layer (23) to make the ammonia vapor condense into liquid ammonia more quickly and reduce the amount of gas in the tower. When the pressure in the low-temperature cooling layer (23) fed back by the pressure controller is too high, the control system adjusts the flow rate of the cooling medium, controls the ammonia vapor condensation speed, and adjusts the flow rates of the ammonia residual gas and steam entering the accident ammonia absorption tower (2) to balance the pressure.

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