A simple and safe recovery system for residual ammonia gas

Abstract

The present invention relates to the field of chemical technology, and in particular to a simple and safe recovery system for residual ammonia gas, comprising 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, wherein the circulation pump group comprises a circulating water pump, a compression pump and a waste heat recovery pump, and the waste heat recovery pump is connected to 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), pure ammonia gas is circulated between the buffer tank (12) and the accident ammonia absorption tower (2) through a gas phase pipeline, pure liquid ammonia is circulated between the accident ammonia absorption tower (2) and the liquid ammonia storage tank (1) through a liquid phase pipeline, an absorption tank (3) absorbs exhaust gas detected by the accident ammonia absorption tower (2), and recovers nitrogen for purging the liquid ammonia storage tank (1), thereby realizing non-escape environmentally friendly treatment and recycling of ammonia.

Description

Technical Field

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

[0002] Ammonia is a critical chemical widely used in industrial production. Cryogenic liquid ammonia is a common storage form used in industrial and agricultural production, typically stored in specialized pressure vessels. Upon use, it is converted to a usable gas through a dedicated liquid-to-gas conversion supply system. However, it is also toxic and hazardous, posing a risk to both humans and the environment. It is irritating and corrosive to the eyes, nose, and skin, and can cause asphyxiation. In liquid ammonia liquid-to-gas conversion supply systems, accidental ammonia emissions occur frequently due to various operating conditions, such as system commissioning, abnormal safety valve tripping, and exhaust emissions. This unintended ammonia cannot be released directly into the atmosphere, as this would pollute and harm the surrounding environment and individuals. It cannot simply be diluted in a discharge tank, as this would waste precious resources. Instead, specialized equipment for absorption and recovery should be considered. Traditional ammonia recovery processes are not only costly, complex, and energy-intensive, but also unsuitable for such systems.

[0003] Therefore, a simple ammonia recovery system was 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] To achieve the above objectives, the present invention adopts the following technical solutions:

[0005] A simple and safe recovery system for ammonia residual 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 to 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 the accident ammonia absorption tower 2, the accident ammonia absorption tower 2 is connected to an absorption tank 3. The liquid ammonia storage tank 1, the vaporizer 11, the buffer tank 12 and the accident ammonia absorption tower 2 circulate ammonia gas through the gas phase pipeline. The accident ammonia absorption tower 2 and the liquid ammonia storage tank 1 circulate liquid ammonia through the liquid phase pipeline. The absorption tank 3 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 tank's own pressure. 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 emergency 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 heats 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 equipped with a booster pump 13, which is linked to the liquid ammonia inlet valve. Under normal operating conditions, the booster pump 13 relies on the pressure within the storage tank to pressurize the liquid ammonia into the vaporizer. If the storage tank pressure is insufficient, the booster pump system is activated to provide additional pressure to ensure continuous liquid ammonia delivery.

[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 from the liquid ammonia storage tank 1 and refrigerate and liquefy it for reflux.

[0009] A water curtain spray system is installed above the liquid ammonia storage tank 1, and the spray valve group switch is designed in the absorption zone of the emergency ammonia absorption tower 2. In this ammonia treatment system, nitrogen purge ensures a safe environment within the equipment, while the water curtain spray treats leaked or unabsorbed residual ammonia, forming a dual protection.

[0010] The pipeline of the vaporizer 11 is equipped with pressure and temperature regulators. A pressure transmitter monitors the downstream pressure in real time, which in turn adjusts the opening of the liquid ammonia inlet valve to control the flow of liquid ammonia into the vaporizer. A temperature sensor monitors the temperature of the vaporized ammonia, and a PID controller regulates the power of the vaporizer's electric heater. The vaporized ammonia is first stored in the ammonia buffer tank 12 to balance system pressure fluctuations. The pressure regulator then stabilizes the ammonia pressure before delivery to various end users, ensuring a 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 ammonia 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. After distillation and purification, the ammonia vapor enters the low-temperature cooling layer 23. After the 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 the ammonia gas is separated in the low-temperature cooling layer 23, it returns to the buffer tank 12.

[0013] The microbubble cloud ammonia dissolution layer 21 is located below the ammonia vapor distillation and purification layer 22, and the low-temperature cooling layer 23 is located above the ammonia vapor distillation and purification layer 22. The low-temperature cooling layer 23 includes a degassing device 24 and a cyclone demister 25. The microbubble cloud ammonia dissolution layer 21 is located at the bottom of the emergency ammonia absorption tower 2 and is equipped with a cyclone bubble generator 21-1 and a venturi tube 21-2. The cyclone bubble generator 21-1 includes a control motor 21-3. This microbubble cloud ammonia dissolution layer uses the triple technology of cyclone fragmentation, Venturi mixing, and dynamic control to solve the pain points of traditional processes: high ammonia escape rate, high energy consumption, and easy clogging.

[0014] An oblique guide bottom plate 26 is provided at the bottom of the micro-bubble cloud ammonia dissolution layer 21 , and a water outlet 26 - 1 with an anti-vortex baffle is designed next to the guide bottom plate 26 .

[0015] The ammonia vapor distillation and purification layer 22 is provided with multi-layer tower plates 22-1 and multi-stage packing layers 22-2. Atomizing sprayers 22-3 are distributed on the tower plates 22-1. The atomizing sprayers 22-3 can spray steam recovered from waste heat and atomized production water or circulating liquid. The packing layer 22-2 is filled with ball metal rings. The packing layer 22-2 is distributed with alkali solution inlet 22-4 and packing holes 22-5. The alkali solution inlet 22-4 and packing holes 22-5 can be designed at the top and bottom of the ammonia vapor distillation and purification layer 22.

[0016] The low-temperature cooling layer 23 includes a cyclone demister 25, which is equipped with a cyclone plate 25-1. A return rail 25-2 is provided outside the cyclone plate 25-1. An overflow port 25-3 is provided on the return rail 25-2, and a drain port is provided below the overflow port 25-3. The constrictor 24 is equipped with a return trough 24-1, and the drain port of the cyclone demister 25 is located above the return trough 24-1.

[0017] The liquid ammonia storage tank 1, vaporizer 11, buffer tank 12, emergency ammonia absorption tower 2, and absorption tank 3 are equipped with temperature transmitters, liquid level pressure differential transmitters, pressure controllers, and gas analyzers, which feed back information to the control system through 4~20ma signals.

[0018] When the gas analyzer detects that the ammonia concentration in the liquid ammonia storage tank 1 reaches a high value online, the control system automatically starts the circulation pump to extract the liquid in the liquid ammonia storage tank 1 into the emergency 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;

[0019] When the control system detects that the ammonia concentration at the outlet of the accident ammonia absorption tower 2 reaches a high value, it opens the water supply valve and the steam valve to replenish water vapor to the accident ammonia absorption tower 2, and opens the pump outlet bypass 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;

[0020] 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.

[0021] 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 will appropriately discharge the liquid in the container based on the liquid level information provided by the liquid level differential pressure transmitter. The control system will also adjust the ammonia residual gas flow and steam flow entering the emergency ammonia absorption tower 2 based on 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 condense the ammonia vapor into liquid ammonia more quickly, thereby reducing the amount of gas 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 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.

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

[0024] Furthermore, the packing layer 22-2 structure is designed as a conical flanged metal step ring. The packing layer 22-2 serves as a load-bearing structure for the packing (to prevent the packing from sinking and deforming), and guides the gas to rise evenly through the opening design, thereby avoiding local concentration of airflow and resulting in a decrease in absorption efficiency.

[0025] Furthermore, the multi-layer tray 22-1 is designed with an arched bottom support to increase the air permeability. While ensuring load-bearing capacity, the arched structure increases the bottom open area to over 40%, reducing local airflow resistance, preventing packing layer collapse and deformation, and accommodating the shock load of high-concentration ammonia. Simultaneously, the ball metal rings within packing layer 22-2 cooperate with the arched bottom support to ensure uniform gas rise, avoiding "hot spots" or "dead zones" caused by localized airflow concentration, and reducing fluctuations in ammonia absorption efficiency to within ±2%. The high porosity (>95%) of the ball metal rings in packing layer 22-2 and the flow-guiding effect of the arched bottom support allow solid particles or crystals to be discharged with the airflow, extending the continuous operation period of the ammonia vapor distillation and purification layer 22 equipment to over three years.

[0026] Furthermore, the atomizing sprayers 22-3 are designed in multiple groups and are evenly distributed in the packing layer 22-2, ensuring that the absorption liquid is evenly sprayed onto the packing surface, avoiding "channeling" or "dry areas", and increasing the gas-liquid contact area.

[0027] Furthermore, the inclined design of the guide plate 26 guides the liquid at the bottom of the tower to quickly converge at the outlet, avoiding localized liquid accumulation and forming dead zones, reducing the risk of crystallization or particle deposition, and lowering the probability of tower bottom corrosion. Furthermore, the inclined structure of the guide plate 26 evenly distributes the rising airflow, reducing the disturbance of the bottom liquid layer by gas vortices and improving gas-liquid separation efficiency.

[0028] Furthermore, the anti-vortex baffles 26-1 feature a special design (such as spiral guide vanes or honeycomb baffles) that disrupt the liquid's rotational tendency, converting vortex energy into laminar flow, reducing liquid surface fluctuations and bubble entrainment. Combined with the inclined flow diversion and vortex suppression of the guide bottom plate 26, this system achieves efficient discharge, stable operation, and low-maintenance costs. Compared to traditional flat-bottom tower structures, this system improves liquid discharge efficiency by approximately 30% and reduces pumping energy consumption by 10% to 15%, making it particularly suitable for absorbing highly corrosive and easily crystallized ammonia.

[0029] Furthermore, the circulating water pump is a shielded pump equipped with a pump outlet bypass connected to an ammonia recovery tank. The bypass reflux liquid from the pump outlet bypass can be linked to the shielded pump's built-in cooling circuit. By adjusting the bypass valve opening, the coolant flow rate is optimized, ensuring motor temperature rise and extending equipment life.

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

[0031] Furthermore, the absorption tank 3 can also recover and temporarily store the leaked liquid ammonia or spray liquid in the event of an accident, thereby preventing secondary pollution.

[0032] Furthermore, the control system dynamically optimizes flow and pump speed based on real-time data (temperature, liquid level, concentration, and pressure). When it detects an abnormal liquid level pressure differential (such as a sudden increase in differential pressure), it warns of packing blockage and triggers a cleaning procedure. Temperature anomalies activate the cooling system, and combined with a gas analyzer, it forms an ammonia monitoring solution, ultimately forming a complete fault handling chain. The control system utilizes temperature transmitters and liquid level pressure differential transmitters equipped in the liquid ammonia storage tank 1 and the emergency ammonia absorber 2, along with an ammonia concentration analyzer, to form a triple monitoring network. Temperature monitoring can identify absorbent overheating or cooling failure, liquid level pressure differential indicates the risk of packing blockage, and concentration data directly correlates to absorption efficiency, ensuring comprehensive awareness of the system's operating status.

[0033] The beneficial effects of this improved technical solution are:

[0034] The system simplifies the multi-stage absorption structure into one-stage absorption, deeply integrates modular design with intelligent control, and forms a triple monitoring network through temperature, pressure, liquid level, and concentration sensors. Each functional layer is independently set to facilitate later upgrades and modifications.

[0035] The system realizes the supply and circulation 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 to form a double protection. The waste heat recovery system recovers the hot water from the vaporizer and the hot air from the compression pump to convert the heat energy into steam heat source.

[0036] The microbubble cloud produced by the swirl bubble generator and venturi tube in the bottom dissolving layer significantly increases the gas-liquid contact area, improving the ammonia dissolution efficiency. The guide plate at the bottom of the dissolving layer further optimizes the gas-liquid flow path and reduces dead zones, resulting in a high-concentration crude ammonia solution at the bottom of the dissolving layer.

[0037] The ammonia vapor distillation and purification layer features a combination of multi-layer trays and Ball metal ring packing, evenly distributed with atomizing sprayers. The recovery system recycles low-temperature waste heat through phase change and compression, rather than directly using steam thermal atomization. This improves ammonia recovery efficiency, economy, and safety. Steam thermal extraction also boosts distillation efficiency, achieving ammonia purity exceeding 99%, and expanding the load range to 50%-120% of the design value.

[0038] The separator and cyclone demister between the low-temperature cooling layers can accurately separate gas and liquid. The cyclone demister rotates at the top, forming an upward vortex system similar to a tornado in the accident ammonia absorption tank, so that the ammonia vapor not recovered in the dissolving layer enters the subsequent distillation purification layer, and the residual ammonia is separated by steam heating. The purified liquid ammonia is returned to the storage tank, forming a closed loop of resources, further improving separation efficiency and reducing energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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

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

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

[0046] Figure 8 Schematic diagram of the filled ball metal ring structure Figure 1 .

[0047] Figure 9 Schematic diagram of the filled ball metal ring structure Figure 2 . DETAILED DESCRIPTION

[0048] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is 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 limiting effect on the scope of protection of the present invention.

[0049] Traditional ammonia recovery processes generally include the following methods: Adsorption: Ammonia in the air is adsorbed using materials such as activated carbon, then collected and stored. Distillation: Ammonia-containing aqueous solutions are distilled and the escaping ammonia is collected. Refrigeration: Ammonia in the air is converted into liquid form by cooling and the liquid ammonia is collected. Combustion: Ammonia is burned into nitrogen and water, and the water is collected by cooling to obtain pure nitrogen. Adsorbent regeneration: The adsorbent that has adsorbed ammonia is regenerated to restore the collected ammonia to pure ammonia. Chemical absorption: Ammonia in the air is dissolved in a chemical absorbent, and the ammonia is collected through a reaction. Microbial absorption: Specific microorganisms are used to convert ammonia into other useful substances, and the products are collected and stored. Acid absorption: Ammonia is absorbed by an acid absorbent, transferred to an absorption liquid for removal. Water absorption: Ammonia is highly soluble in water and can be recovered by heating or adding quicklime. Catalytic combustion decomposition: Ammonia is decomposed into hydrogen and nitrogen by heating a catalytic bed. The gases then react with oxygen in the air to burn the ammonia into nitrogen and water vapor. Each of these methods has its advantages and disadvantages, and selecting the appropriate one requires a case-by-case evaluation. For example, adsorption is suitable for small-scale treatment, while chemical absorption and acid absorption are suitable for large-scale industrial applications. While the catalytic combustion decomposition method requires a higher equipment investment, it can effectively treat large quantities of ammonia.

[0050] However, for the liquid ammonia liquid-gas conversion supply system, the above-mentioned ammonia recovery process not only has high investment costs, but also has complex processes and high energy consumption, and is not suitable for this type of supply system.

[0051] Therefore, we developed a simple and safe ammonia recovery system. This system utilizes a multi-stage physical and chemical process (gasification, absorption, distillation, and cooling) to efficiently recover and recycle ammonia, ensuring safety, environmental friendliness, and economic efficiency. Its core advantages lie in its integrated waste heat recovery, microbubble absorption, and closed-loop design, overcoming the bottlenecks of traditional processes, such as high energy consumption and secondary pollution. Furthermore, through automated control of circulating water replenishment, waste heat recovery, and liquid replacement, it effectively reduces equipment investment and energy consumption. This design is more suitable compared to the high investment costs of traditional acid cleaning or membrane processes.

[0052] Specific examples Figure 1-7 As shown, a simple and safe ammonia waste gas recovery system includes a liquid ammonia storage tank 1, an emergency 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, a compression pump, and a waste heat recovery pump, and the waste heat recovery pump is connected to a steam valve. The liquid ammonia storage tank 1 is connected to a vaporizer 11, and the vaporizer 11 is connected to a buffer tank 12. The vaporizer 11 is connected to the emergency ammonia absorption tower 2. The liquid ammonia storage tank, vaporizer 11, buffer tank 12 and the emergency ammonia absorption tower 2 circulate through the gas phase pipeline, and the emergency ammonia absorption tower 2 circulates through the liquid phase pipeline with the liquid ammonia storage tank 1.

[0053] An absorption tank 3 is designed after the accident ammonia absorption tower 2. The absorption tank 3 absorbs the inert gas treated by the accident ammonia absorption tower 2 and can obtain nitrogen to purge the liquid ammonia storage tank 1.

[0054] The liquid ammonia in the liquid ammonia storage tank 1 is pressed into the vaporizer 11 by the tank's own pressure. 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 emergency 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.

[0055] A microbubble cloud ammonia dissolution layer 21, an ammonia vapor distillation and purification layer 22, and a low-temperature cooling layer 23 are provided in the accident ammonia absorption tower 2. The ammonia gas is absorbed by the circulating water in the microbubble cloud ammonia dissolution layer 21 to form ammonia water, and the undissolved ammonia gas rises to the ammonia vapor distillation and purification layer 22. The ammonia vapor enters the low-temperature cooling layer 23 after distillation and purification. After the 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 the ammonia gas is separated in the low-temperature cooling layer 23, it returns to the buffer tank 12.

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

[0057] The microbubble cloud ammonia dissolution layer 21 is located below the ammonia vapor distillation and purification layer 22, and the low-temperature cooling layer 23 is located above the ammonia vapor distillation and purification layer 22. The low-temperature cooling layer 23 includes a deflator 24 and a cyclone demister 25. The deflator 24 is provided with a reflux groove 24-1, which can reflux dripping liquid of the cyclone demister 25.

[0058] A waste heat recovery pump connected to the low-temperature cooling layer 23 absorbs heat from the ammonia vapor separation process and the compression step, combining it with the water heated by the vaporizer 11 to produce low-pressure steam. This steam is then supplied to the ammonia vapor distillation and purification layer 22 for ammonia purification. Simultaneously, an automatic convection circulation system is formed within the tank, with a warm and humid lower layer and a dry and cool upper layer.

[0059] Located at the bottom of the accident ammonia absorber 2, the microbubble cloud ammonia dissolution layer 21 is equipped with a swirl bubble generator 21-1 and a Venturi tube 21-2. A slanted guide plate 26 is located at the bottom of the microbubble cloud ammonia dissolution layer 21. Next to the guide plate 26 is a water outlet 26-1 with an anti-vortex baffle. The swirl bubble generator 21-1 includes a control motor 21-3. Driven by the control motor 21-3, the swirl bubble generator mixes water or ammonia solution with ammonia gas to form microbubbles. This significantly improves gas-liquid contact efficiency and effectively reduces bottom crystallization. The slanted design of the guide plate 26 (30° to 45°) works in conjunction with the anti-vortex baffle to prevent particulate accumulation in the swirl zone. Furthermore, the slanted structure of the guide plate 26 evenly distributes the rising airflow, reducing the disturbance of the bottom liquid layer by gas vortices and improving gas-liquid separation efficiency.

[0060] The ammonia vapor distillation and purification layer 22 is equipped with multiple trays 22-1 and multiple packing layers 22-2. Trays 22-1 are equipped with atomizing sprayers 22-3. Atomizing sprayers 22-3 can be located at the top and bottom of the ammonia vapor distillation and purification layer 22. Multiple groups of atomizing sprayers 22-3 are evenly distributed within the packing layer 22-2. This ensures that the absorption liquid is evenly sprayed onto the packing surface, avoiding "channeling" or "dry areas" and increasing the gas-liquid contact area.

[0061] The packing layer 22-2 is provided with an alkali liquid inlet 22-4 and a packing hole 22-5. The alkali liquid inlet 22-4 and the packing hole 22-5 can be designed at the top and bottom of the ammonia vapor distillation purification layer 22. The packing hole 22-5 can be connected to a water pipe to clean the packing layer 22-2. The ball metal ring structure filled on the packing layer 22-2 is designed as a conical flanging metal step ring. The packing layer 22-2 serves as a packing load-bearing structure (to prevent the packing from sinking and deforming) and guides the gas to rise evenly through the opening design, avoiding local concentration of airflow and resulting in a decrease in absorption efficiency. The packing parameter design of the conical flanging metal step ring is shown in Table 1 below, and the size and structure parameter design is shown in Table 2 and Figure 8 and 9 shown.

[0062] Table 1 Characteristics of conical flanged ball metal ring packing

[0063]

[0064] Table 2 Dimensional parameters of tapered flanged ball metal ring packing

[0065]

[0066] The multi-layer tray 22-1 is designed with an arched bottom support to increase the air permeability. While ensuring load-bearing capacity, the arched structure increases the bottom open area to over 40%, reducing local airflow resistance, preventing packing layer collapse and deformation, and accommodating the shock load of high-concentration ammonia gas. Furthermore, the ball metal rings within packing layer 22-2 cooperate with the arched bottom support to ensure uniform gas rise, avoiding "hot spots" or "dead zones" caused by localized airflow concentrations, and reducing fluctuations in ammonia absorption efficiency to within ±2%. The high porosity (>95%) of the ball metal rings in packing layer 22-2 and the flow-guiding effect of the arched bottom support allow solid particles and crystals to be discharged with the airflow, extending the continuous operation cycle of the ammonia distillation and purification layer 22. The packing holes 22-5 are open-topped and equipped with spiral-wound sealing gaskets to enhance the sealing of the ammonia distillation and purification layer 22 and prevent ammonia gas escape.

[0067] The alkali liquor inlet 22-4 in the ammonia gas distillation purification layer 22 can improve the purity of ammonia gas and the stability of the distillation purification system. 、 The alkali solution passes through the packing layer and contacts with the gas phase in countercurrent, and a neutralization reaction occurs:

[0068] , the sulfates and hydrogensulfates generated by the reaction are dissolved in the liquid phase to prevent acidic substances from entering the fractionation section to form ammonium salt crystals (such as ) Cause pipe blockage. Alkali solution can also increase pH to 10~12, promoting Dissociation , increase the concentration of gaseous ammonia and improve the distillation efficiency.

[0069] The cyclone demister 25 is equipped with a motor-driven swirl plate 25-1. A return rail 25-2 is provided outside the swirl plate 25-1. An overflow port 25-3 is provided on the return rail 25-2. A drain port is provided below the overflow port 25-3, which is connected to the return ditch 24-1 of the deconcentrator 24. The deconcentrator 24 is provided with cooling water inlets and outlets, allowing the purified ammonia vapor in the ammonia vapor distillation and purification layer 22 to be initially cooled by circulating cooling water in the shell side. The swirl plate 25-1 of the cyclone demister 25 uses centrifugal force to fling uncondensed ammonia droplets toward the tower wall. Liquid ammonia is collected along the return rail 25-2 and collected at the overflow port 25-3. The liquid ammonia collected at the overflow port 25-3 flows through the drain port into the return ditch 24-1 of the deconcentrator 24 and is then discharged along with the circulating condensed water. The gas phase, after passing the inspection, circulates upward into the buffer tank 12 or the absorption tank 3. The low-temperature cooling layer 23 utilizes a cascaded process of fractionation, cyclone defoaming, reflux, and fractionation to achieve efficient recovery of liquid ammonia. The fractionator 24 separates high-concentration liquid ammonia through circulating cooling and condensation, and cyclone defoaming further purifies it to industrial-grade standards. Furthermore, the cyclone defoamer 25 rotates at the top, creating a more efficient airflow that drives water vapor upward from the lower layers, further improving the efficiency of the accident ammonia absorber 2.

[0070] The liquid ammonia storage tank 1, vaporizer 11, buffer tank 12, emergency ammonia absorption tower 2, and absorption tank 3 are equipped with temperature transmitters, liquid level pressure differential transmitters, pressure controllers, and gas analyzers. Information is fed back to the control system via a 4-20ma signal. When the gas analyzer detects that the ammonia concentration 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 emergency ammonia absorption tower 2. At the same time, the control system opens the water supply pipeline to replenish fresh water into the liquid ammonia storage tank 1.

[0071] When the control system detects that the ammonia concentration at the outlet of the accident ammonia absorption tower 2 reaches a high value, it opens the water supply valve and the steam valve to replenish water vapor to the accident ammonia absorption tower 2, and opens the pump outlet bypass 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;

[0072] 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.

[0073] 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 will appropriately discharge the liquid in the container based on the liquid level information provided by the liquid level differential pressure transmitter. The control system will also adjust the ammonia residual gas flow and steam flow entering the emergency ammonia absorption tower 2 based on 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 condense the ammonia vapor into liquid ammonia more quickly, thereby reducing the amount of gas in the tower.

[0074] 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.

[0075] The vaporizer 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 entering the vaporizer, and monitors the temperature of the ammonia gas after vaporization. The power of the vaporizer electric heater is adjusted through the PID controller.

[0076] The liquid ammonia storage tank 1 is provided with a booster pump 13, which is linked to 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, which directly freezes and liquefies the vaporized ammonia gas in the liquid ammonia storage tank 1 to achieve simple recovery.

[0077] Furthermore, the circulating water pump is a shielded pump with a pump outlet bypass connected to an ammonia recovery tank. The bypass reflux liquid from the pump outlet can be linked to the shielded pump's built-in cooling circuit. By adjusting the bypass valve opening, the coolant flow rate is optimized, ensuring motor temperature rise and extending equipment life.

[0078] Furthermore, the control system dynamically optimizes flow and pump speed based on real-time data (temperature, liquid level, concentration, and pressure). When the control system detects an abnormal liquid level pressure differential (such as a sudden increase in differential pressure), it warns of packing blockage and triggers a cleaning procedure. Temperature anomalies activate the cooling system, and combined with a gas analyzer, it forms an ammonia monitoring solution, ultimately forming a complete fault handling chain. The control system utilizes temperature transmitters and liquid level pressure differential transmitters equipped on the liquid ammonia storage tank 1 and the emergency ammonia absorber 2, along with an ammonia concentration analyzer, to form a triple monitoring network. Temperature monitoring can identify absorbent overheating or cooling failure, liquid level pressure differential indicates the risk of packing blockage, and concentration data directly correlates to absorption efficiency, ensuring comprehensive awareness of the system's operating status.

[0079] Further, refer to the system process Figure 1 and 3 The absorption tank 3 at the tail of the outlet of the accident ammonia absorption tower 2 absorbs the inert gas , 5%~10% dilute sulfuric acid (or hydrochloric acid, adsorbent, etc.) can be used in the absorption tank 3 to neutralize the residual ammonia to generate ammonium sulfate (or ammonium chloride) reaction equation: When the exhaust gas passes through the absorption tank 3, the ammonia is captured by the adsorbent, and the nitrogen passes directly due to its inertness, thus achieving physical separation.

[0080] Furthermore, a filter may be provided on the recovery pipe of the ammonia recovery barrel to remove particulate impurities and metal ions to improve the purity of the recovered ammonia.

[0081] Furthermore, when nitrogen is purging the liquid ammonia storage tank 1, a water curtain spray can be added above the liquid ammonia storage tank 1 to adapt to special environments, 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.

[0082] 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. The gravity flow system returns the liquid to the front of the degasifier 11 for re-gasification and utilization.

[0083] The operating sequence of this ammonia residual gas safety recovery system is as follows:

[0084] Liquid usage: liquid ammonia storage tank 1 → vaporizer 11 (electrically heated water for vaporization) → buffer tank 12 (pressure stabilization) → end user (ammonia-using equipment).

[0085] Liquid ammonia is pressed by the tank's own pressure (when the pressure is insufficient, the booster pump system can be turned on) to the electrically heated water bath vaporizer. The pressure on the gaseous ammonia pipeline automatically adjusts the liquid ammonia flow entering the vaporizer. The thermometer on the gaseous ammonia pipeline automatically adjusts the power of the vaporizer's electric heater to ensure that the ammonia flow out of the vaporizer (≤60Nm³ / h, w) is within the control index range. The ammonia is then stored in the ammonia buffer tank and then delivered to each terminal through a pressure regulating device.

[0086] Recovery process: Ammonia leaked from liquid ammonia storage tank 1, buffer tank 12 or the system → accident ammonia absorber 2 (absorption → purification → liquefaction) → recovered liquid ammonia returns to storage tank 1 → absorption tank 3 recovers nitrogen to purge liquid ammonia storage tank 1; uncondensed ammonia → returns to buffer tank 12 for circulation.

[0087] The accident ammonia absorber processes residual ammonia gases, including vented gas from safety valves in liquid ammonia tanks and ammonia buffer tanks, liquid ammonia truck unloading, and pipeline equipment purge and replacement gas. The process capacity is approximately 704.23 kg / h. After treatment meets standards, the gas is discharged from the top of the tower or recycled into the buffer tank. The ammonia spray liquid, which has been initially dissolved and absorbed at the bottom of the accident ammonia absorber, is pumped away and barreled for recycling. The coolant, after distillation and purification, is also pumped back into the liquid ammonia storage tank. If the mixed gas is too high for the accident ammonia absorber to meet treatment standards, an absorption tank is used to further absorb and separate water vapor, residual ammonia, carbon dioxide, and other gases from the tail gas, leaving the separated inert gas for further recycling.

[0088] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0089] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. The above is only a preferred implementation method of the present invention. It should be pointed out that due to the limitations of textual expression, there are objectively infinite specific structures. For ordinary technicians in this technical field, without departing from the principles of the present invention, they can make several improvements, modifications or changes, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the inventive concept and technical solution to other occasions without improvement, should be regarded as the scope of protection of the present invention.

Claims

1. A simple and safe recovery system for residual ammonia gas, comprising a liquid ammonia storage tank (1), an emergency ammonia absorption tower (2), a circulating pump group, a gas phase pipeline and a liquid phase pipeline, wherein the circulating pump group comprises a circulating water pump and a compression pump, the compression pump is connected to a waste heat recovery pump, and the waste heat recovery pump is connected to a steam valve, characterized in that: The liquid ammonia storage tank (1) is connected to the vaporizer (11), the vaporizer (11) is connected to the buffer tank (12), 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 accident ammonia absorption tower (2) is connected to the absorption tank (3), the absorption tank (3) absorbs the exhaust gas detected by the accident ammonia absorption tower (2), and then recovers nitrogen 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 pressure of the tank body itself. The vaporizer (11) is an electrically heated water bath type vaporizer. 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 guides the ammonia gas into the emergency ammonia absorption tower (2); The accident ammonia absorption tower (2) is provided with a micro-bubble 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 micro-bubble cloud ammonia dissolution layer (21) to form ammonia water, and undissolved ammonia rises to the ammonia vapor distillation and purification layer (22). The vaporizer (11) is connected to the steam valve and, together with the waste heat recovery pump, provides a steam heat source for the ammonia vapor distillation and purification layer (22). After distillation and purification, the ammonia vapor 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). The microbubble cloud ammonia dissolution layer (21) is located at the bottom of the accident ammonia absorption tower (2). An inclined guide bottom plate (26) is provided at the bottom of the microbubble cloud ammonia dissolution layer (21). A swirl bubble generator (21-1) and a venturi tube (21-2) are also provided on the microbubble cloud ammonia dissolution layer (21). The low-temperature cooling layer (23) includes a decompressor (24) and a swirl demister (25). The cyclone demister (25) is provided with a cyclone plate (25-1), a return rail (25-2) is provided outside the cyclone plate (25-1), an overflow port (25-3) is provided on the return rail (25-2), a drain port is provided below the overflow port (25-3), a return trough (24-1) is provided on the divider (24), and the drain port on the cyclone demister (25) is above the return trough (24-1).

2. A simple and safe ammonia waste gas recovery system according to claim 1, characterized in that: The ammonia vapor distillation and purification layer (22) is provided with a multi-layer tower plate (22-1) and a multi-stage packing layer (22-2), the tower plate (22-1) is provided with an arched bottom support member, the packing layer (22-2) is filled with ball metal rings, and the packing layer (22-2) is provided with an alkali solution inlet (22-4) and packing holes (22-5).

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

4. The simple and safe recovery system for residual ammonia gas 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-gasification.

5. The simple and safe recovery system for residual ammonia gas according to claim 1, characterized in that: The liquid ammonia storage tank (1) is connected to a booster pump (13), which is linked to a liquid ammonia inlet valve. The liquid ammonia storage tank (1) is also connected to a compression pump, which directly freezes and liquefies the ammonia gas vaporized in the liquid ammonia storage tank (1) and recycles it into the liquid ammonia storage tank (1).

6. The simple and safe recovery system for residual ammonia gas according to claim 1, characterized in that: The liquid ammonia storage tank (1), vaporizer (11), buffer tank (12), emergency ammonia absorption tower (2), and absorption tank (3) are equipped with a temperature transmitter, a liquid level pressure differential transmitter, a pressure controller, and a gas analyzer, which feed information back to the control system via a 4-20ma signal. When the gas analyzer detects online that the ammonia concentration in the liquid ammonia storage tank (1) reaches a high value, the control system 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 supply fresh water to the liquid ammonia storage tank (1); 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 supply 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; 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, reduce the temperature of the ammonia vapor distillation and purification layer (22), and adjust the steam parameters in the ammonia vapor distillation and purification layer (22) to optimize the distillation process, thereby indirectly affecting the temperature. When the pressure of the ammonia vapor distillation 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 pressure differential transmitter. The control system also adjusts the ammonia residual gas flow rate and steam flow rate 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, thereby reducing the amount of gas in the tower. 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.

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