Ammonia and VOCs gas recovery system for synthetic ammonia plant

Abstract

The present invention discloses an ammonia-containing VOCs gas recovery system for a synthetic ammonia device, including a synthetic ammonia nitrogen hydrogen combined compressor and a synthetic ammonia circulating gas compressor. A collection tank is added near the synthetic ammonia nitrogen hydrogen combined compressor and the synthetic ammonia circulating gas compressor to collect the sewage from the synthetic ammonia nitrogen hydrogen combined compressor and the synthetic ammonia circulating gas compressor in a centralized and closed manner; the top of the collection tank is provided with a local remote level gauge, a nitrogen sealing facility, a sewage pipe inlet pipeline and a safety valve from right to left, the outlet pipeline of the collection tank is provided with a local remote pressure gauge, a transmission pump is provided at the bottom of the left side of the collection tank, and a solenoid valve is provided at the outlet of the transmission pump; a single call valve is provided at the outlet pipeline of the collection tank, and the ammonia-containing waste gas is sent to the saturator of a chemical plant after passing through an ammonia washing tower. The present invention solves the problem of gas leakage at various points in the synthetic ammonia production area, and the leaked gas is collected in a closed manner. The collected gas is washed with water in the ammonia washing tower and sent to the saturator of a chemical plant for recycling, thereby solving the problem of gas leakage on site.

Description

Technical Field

[0001] The invention relates to the technical field of chemical environmental protection, and in particular to a system for recovering ammonia and VOCs gases in a synthetic ammonia device. Background Art

[0002] The production of synthetic ammonia mainly involves the mixing of pure hydrogen and pure nitrogen in a specified ratio, which are then pressurized by a nitrogen-hydrogen mixed gas compressor and sent to an ammonia synthesis tower to generate ammonia under the action of a catalyst. Most of the ammonia is condensed step by step to produce qualified liquid synthetic ammonia (referred to as liquid ammonia), and some of the uncondensed ammonia and nitrogen-hydrogen mixed gas are pressurized by a circulating machine and added to the synthetic system for circulating gas use. During the production process, some gases escape into the atmosphere when the equipment pipelines are discharged and vented, affecting the safety and environmental protection of the production area. The main emission points are as follows: the nitrogen-hydrogen mixed gas entrained from the nitrogen-hydrogen mixed gas compressor during the discharge process of buffer tanks at all levels escapes into the surrounding atmosphere; the nitrogen-hydrogen mixed gas and ammonia entrained from the inlet and outlet piston rod packing of the synthetic ammonia circulating gas compressor escape into the surrounding atmosphere; the pure ammonia gas discharged from the liquid ammonia flash tank during the pressure control of the inlet and outlet materials; the pure ammonia gas discharged from the liquid ammonia storage tank during the pressure control of the inlet and outlet materials.

[0003] However, in the process of synthetic ammonia production, the lubricating oil of the nitrogen-hydrogen mixed gas combined compressor and the synthetic ammonia circulating gas compressor will be brought into the cylinder and separator in small amounts along with the packing and piston rod. If these oil and water enter the ammonia synthesis tower, the synthesis efficiency and the quality of the liquid ammonia product will be affected. Therefore, in the operation of the synthetic ammonia unit, the nitrogen-hydrogen mixed gas combined compressor and the synthetic ammonia circulating gas compressor separators at all levels need to be discharged regularly to discharge the separated oil and water. Since the discharge pressure of each level of separator is relatively high, part of the nitrogen-hydrogen mixed gas and ammonia will be entrained during the discharge process, and the discharged gas will escape into the atmosphere of the production area, which has a great impact on the safety and environment of the production area. In addition, in its production process, due to the high pressure of the production system, the produced liquid ammonia needs to be stored at reduced pressure. , after the pressure is reduced in the liquid ammonia flash tank, it is sent to the liquid ammonia storage tank for storage and export. The ammonia separated during the pressure reduction is discharged into the air through a high-level venting pipe. A certain amount of ammonia is also volatilized in the liquid ammonia storage tank when the material is in and out, and an appropriate amount of discharge is carried out to control the tank pressure, and the ammonia is discharged into the air through a high-level venting pipe. The discharged ammonia escapes into the atmosphere of the production area, which has a great impact on the safety and environment of the production area. With the gradual increase in environmental protection pressure, the same industry generally adopts the method of adding an ammonia washing tower to collect the vented ammonia-containing gas and wash it with water before discharging it into the air. The washing water is circulated and sprayed in the tower to absorb ammonia. When the ammonia content of the washing water in the ammonia washing tower is high (referred to as ammonia water), part of the ammonia will escape into the atmosphere of the production area, which has certain safety hazards to the production area. Summary of the invention

[0004] The purpose of the present invention is to solve the problems in the prior art and to propose a system for recovering ammonia and VOCs gases from a synthetic ammonia plant.

[0005] In order to achieve the above-mentioned object, the present invention adopts the following technical scheme: a synthetic ammonia unit ammonia and VOCs gas recovery system, including a synthetic ammonia nitrogen hydrogen combined compressor and a synthetic ammonia circulating gas compressor, a collection tank is added near the synthetic ammonia nitrogen hydrogen combined compressor and the synthetic ammonia circulating gas compressor, for centralized and closed collection of sewage from the synthetic ammonia nitrogen hydrogen combined compressor and the synthetic ammonia circulating gas compressor;

[0006] The top of the collecting tank is equipped with a local remote level gauge, nitrogen sealing facilities, sewage pipe inlet pipe and safety valve from right to left. The outlet pipe of the collecting tank is equipped with a local remote pressure gauge. A transmission pump is installed at the bottom of the left side of the collecting tank, and a solenoid valve is installed at the outlet of the transmission pump. A single call valve is installed at the outlet pipe of the collecting tank, and the ammonia-containing waste gas is sent to the saturator of the chemical plant after passing through the ammonia washing tower.

[0007] The process interlocking system includes an interlocking device consisting of a transmission pump, a solenoid valve, and a local remote liquid level gauge. The transmission pump and the solenoid valve are interlocked through the process interlocking system according to the liquid level displayed by the local remote liquid level gauge, and interlocking control is performed on valves, pressure gauges and other electrical appliances at various positions.

[0008] Preferably, the nitrogen sealing facility is a nitrogen sealing pressure-stabilizing valve.

[0009] Preferably, when the pressure in the collection tank is ≤0.5KPa (adjustable), the nitrogen replenishment valve is interlocked to open, when the outlet pipeline pressure reaches 20kPa, the single call valve is automatically opened, and when the pressure in the collection tank rises to 2kPa (adjustable), the nitrogen replenishment valve is interlocked to close.

[0010] The operating steps of the ammonia and VOCs gas recovery system of the synthetic ammonia unit are as follows:

[0011] S1: Collect the ammonia gas discharged from the liquid ammonia flash tank and the liquid ammonia storage tank in a centralized manner, and add an ammonia washing tower on site. The vented gas from the flash tank and the storage tank is washed by the ammonia washing tower and then sent to the saturator of the chemical plant. The washed ammonia water is used in the flue gas purification process. The liquid at the bottom of the collection tank enters the transmission pump and is uniformly transported to the condensate to the chemical system;

[0012] S2: A remote level gauge is provided in the ammonia washing tower, and the transmission pump and the solenoid valve at the transmission pump outlet are interlocked with the local remote level gauge. When the liquid level displayed by the local remote level gauge reaches 80%, the transmission pump is started for 5 seconds, and the solenoid valve at the transmission pump outlet is opened within 10 seconds. The ammonia water is sent to the condensate to the chemical system. When the liquid level drops to 20%, the solenoid valve at the transmission pump outlet is closed for 5 seconds, and the transmission pump is stopped for 10 seconds;

[0013] S3: Before the collected gas enters the chemical plant saturator, when the outlet pipeline pressure reaches 60KPa (adjustable), the VOCs emergency release valve at the inlet of the chemical plant saturator will be automatically opened to prevent overpressure in the pipeline and collection tank. When the pressure drops to 20KPa (adjustable), the emergency release valve will be automatically closed.

[0014] S4: Before the collected gas enters the chemical plant saturator, an online oxygen content analyzer is installed on the outlet pipeline. When the oxygen content reaches 2%, the VOCs gas valve at the inlet of the chemical plant saturator is interlocked to close, and the VOCs gas emergency release valve at the inlet of the chemical plant saturator is interlocked to open to ensure the production safety of the condensate dechemical system.

[0015] The process interlocking system of the ammonia and VOCs gas recovery system of the synthetic ammonia unit is as follows:

[0016] ① Before the VOCs gas enters the chemical plant saturator, when the online oxygen content analyzer shows that the oxygen content reaches 2%, the VOCs gas valve of the chemical plant saturator is interlocked and closed, and the emergency release valve of the VOCs gas inlet of the chemical plant saturator is interlocked and opened;

[0017] ② Before the VOCs gas enters the saturator of the chemical plant, when the local remote pressure gauge shows that the VOCs gas pipeline pressure reaches 60KPa (adjustable), the emergency relief valve in front of the saturator will be automatically opened, and when the pressure drops to 20KPa (adjustable), the emergency relief valve will be automatically closed;

[0018] ③ The transmission pump of the collection tank, the solenoid valve at the outlet of the transmission pump and the local remote liquid level gauge are interlocked. When the liquid level reaches 80%, the transmission pump is started and the solenoid valve at the outlet of the transmission pump is opened. When the liquid level drops to 20%, the solenoid valve at the outlet of the transmission pump is closed and the transmission pump is stopped.

[0019] ④ A nitrogen-sealed pressure-stabilizing valve is added to the collection tank. When the pressure in the tank is ≤0.5KPa (adjustable), the nitrogen replenishing valve is interlocked to open. When the pressure in the tank rises to 2KPa (adjustable), the nitrogen replenishing valve is interlocked to close to ensure that the tank is always in a positive pressure state;

[0020] ⑤ The transmission pump of the ammonia washing tower and the solenoid valve at the outlet of the transmission pump are interlocked with the liquid level setting. When the liquid level reaches 80%, the interlock starts the transmission pump and opens the solenoid valve at the outlet of the transmission pump. When the liquid level drops to 20%, the interlock closes the solenoid valve at the outlet of the transmission pump and stops the operation of the transmission pump.

[0021] The beneficial effects of the present invention are:

[0022] 1. The gas leaking from each point in the synthetic ammonia production area is collected in a closed manner, and the collected gas is washed with water in the ammonia washing tower and then sent to the chemical plant saturator for recycling. After being deaminated again in the saturator, it is sent to the company's internal gas system for use, thus solving the problem of nitrogen-hydrogen mixed gas and ammonia leakage entrained in the discharge process of traditional nitrogen-hydrogen combined compressors and circulating gas compressors.

[0023] 2. Solve the problem of ammonia gas escaping into the atmosphere when liquid ammonia flash tanks and liquid ammonia storage tanks are vented.

[0024] 3. Through the closed washing and recovery of nitrogen-hydrogen mixed gas and ammonia gas emitted from the synthetic ammonia production area, the traditional treatment route in the industry is broken, and the effective recovery of hydrogen-containing and ammonia-containing gas resources is achieved. At the same time, it has the advantages of safety, stability and environmental protection. The nitrogen-hydrogen mixed gas and ammonia gas emitted by the synthetic ammonia device are collected and treated in a closed manner. After collection and washing, the gas is sent to the chemical ammonium saturator for recycling, and the ammonia-containing liquid after washing is sent to the coke oven flue gas purification process as raw material, achieving a new breakthrough in the process and the effect of resource recovery and reuse.

[0025] 4. Solve the problem of personnel frequently starting the pump and checking the liquid level, and realize the conditions for on-site remote monitoring and automatic pumping and water delivery. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a process flow chart of the ammonia and VOCs gas recovery system of the synthetic ammonia device proposed by the present invention;

[0027] Figure 2 This is a control flow chart of the ammonia and VOCs gas recovery system of the synthetic ammonia device proposed by the present invention;

[0028] Figure 3 This is the process interlocking diagram of the ammonia and VOCs gas recovery system of the synthetic ammonia device proposed by the present invention;

[0029] Figure 4 This is an interlocking logic block diagram of the ammonia and VOCs gas recovery system of the synthetic ammonia device proposed by the present invention.

[0030] In the figure: 1. Synthetic ammonia circulating gas compressor; 2. Synthetic ammonia nitrogen hydrogen combined compressor; 3. Condensate to chemical system; 4. Collection tank; 5. Liquid ammonia flash tank; 6. Liquid ammonia storage tank; 7. Ammonia washing tower; 8. Ammonia water to flue gas purification; 9. Chemical plant saturator; 10. Transmission pump. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0032] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0033] Reference Figure 1-4 , the ammonia and VOCs gas recovery system of the synthetic ammonia unit includes a synthetic ammonia nitrogen hydrogen combined compressor 2 and a synthetic ammonia circulating gas compressor 1, and a collection tank 4 is added near the synthetic ammonia nitrogen hydrogen combined compressor 2 and the synthetic ammonia circulating gas compressor 1 to collect the sewage from the synthetic ammonia nitrogen hydrogen combined compressor 2 and the synthetic ammonia circulating gas compressor 1 in a centralized and closed manner;

[0034] The top of the collecting tank 4 is provided with a local remote level gauge, a nitrogen sealing facility, a sewage pipe inlet pipe and a safety valve from right to left. The outlet pipe of the collecting tank 4 is provided with a local remote pressure gauge. A transmission pump 10 is provided at the bottom of the left side of the collecting tank 4, and a solenoid valve is provided at the outlet of the transmission pump 10. A single call valve is provided at the outlet pipe of the collecting tank 4, and the ammonia-containing waste gas is sent to the chemical plant saturator 9 after passing through the ammonia washing tower 7;

[0035] The process interlocking system includes an interlocking device consisting of a transmission pump 10, a solenoid valve, and a local remote liquid level gauge. The transmission pump 10 and the solenoid valve are interlocked through the process interlocking system according to the liquid level displayed by the local remote liquid level gauge, and interlocking control is performed on valves, pressure gauges and other electrical appliances at various positions.

[0036] In specific use, the nitrogen sealing facility is a nitrogen sealing pressure-stabilizing valve.

[0037] In actual use, when the pressure in collecting tank 4 is ≤0.5KPa (adjustable), the nitrogen replenishing valve is interlocked to open, and when the outlet pipeline pressure reaches 20kpa, the single call valve is automatically opened. When the pressure in collecting tank 4 rises to 2kpa (adjustable), the nitrogen replenishing valve is interlocked to close.

[0038] In specific use, the operating steps of the ammonia and VOCs gas recovery system of the synthetic ammonia unit are as follows:

[0039] S1: Collect the ammonia gas discharged from the liquid ammonia flash tank 5 and the liquid ammonia storage tank 6, and add an ammonia washing tower 7 on site. The discharged gas from the flash tank and the storage tank is washed by the ammonia washing tower 7 and then sent to the chemical plant saturator 9. The washed ammonia water is used in the flue gas purification 8 process. The bottom liquid of the collection tank 4 enters the transmission pump 10 and is uniformly transported to the condensate to the chemical system 3;

[0040] S2: A remote level gauge is provided in the ammonia washing tower 7, and the transmission pump 10 and the solenoid valve at the outlet of the transmission pump 10 are interlocked with the local remote level gauge. When the liquid level displayed by the local remote level gauge reaches 80%, the transmission pump 10 is started for 5 seconds, and the solenoid valve at the outlet of the transmission pump 10 is opened within 10 seconds, and the ammonia water is sent to the condensate to the chemical system 3. When the liquid level drops to 20%, the solenoid valve at the outlet of the transmission pump 10 is closed for 5 seconds, and the transmission pump 10 is stopped for 10 seconds;

[0041] S3: Before the collected gas enters the chemical plant saturator 9, when the outlet pipeline pressure reaches 60KPa (adjustable), the VOCs emergency release valve of the chemical plant saturator inlet is automatically opened to prevent overpressure of the pipeline and the collection tank. When the pressure drops to 20KPa (adjustable), the emergency release valve is automatically closed;

[0042] S4: Before the collected gas enters the chemical plant saturator 9, an online oxygen content analyzer is installed on the outlet pipeline. When the oxygen content reaches 2%, the VOCs gas valve at the inlet of the chemical plant saturator is interlocked to close, and the VOCs gas emergency release valve at the inlet of the chemical plant saturator is interlocked to open to ensure the production safety of the condensate dechemical system 3.

[0043] In specific use, the process interlocking system of the ammonia and VOCs gas recovery system of the synthetic ammonia unit is as follows:

[0044] ① Before the VOCs gas enters the chemical plant saturator, when the online oxygen content analyzer shows that the oxygen content reaches 2%, the VOCs gas valve of the chemical plant saturator is interlocked and closed, and the emergency release valve of the VOCs gas inlet of the chemical plant saturator is interlocked and opened;

[0045] ② Before the VOCs gas enters the saturator of the chemical plant, when the local remote pressure gauge shows that the VOCs gas pipeline pressure reaches 60KPa (adjustable), the emergency relief valve in front of the saturator will be automatically opened, and when the pressure drops to 20KPa (adjustable), the emergency relief valve will be automatically closed;

[0046] ③ The transmission pump 10 of the collection tank 4, the solenoid valve at the outlet of the transmission pump 10 and the local remote liquid level gauge are interlocked. When the liquid level reaches 80%, the transmission pump is started and the solenoid valve at the outlet of the transmission pump is opened. When the liquid level drops to 20%, the solenoid valve at the outlet of the transmission pump is closed and the transmission pump is stopped.

[0047] ④ A nitrogen-sealed pressure-stabilizing valve is added to the collection tank 4. When the pressure in the tank is ≤0.5KPa (adjustable), the nitrogen replenishing valve is interlocked to open. When the pressure in the tank rises to 2KPa (adjustable), the nitrogen replenishing valve is interlocked to close, ensuring that the tank is always in a positive pressure state;

[0048] ⑤ The transmission pump 10 of the ammonia washing tower 7 and the solenoid valve at the outlet of the transmission pump 10 are interlocked with the liquid level setting. When the liquid level reaches 80%, the interlock starts the transmission pump 10 and opens the solenoid valve at the outlet of the transmission pump 10. When the liquid level drops to 20%, the interlock closes the solenoid valve at the outlet of the transmission pump 10 and stops the operation of the transmission pump.

Claims

1. Ammonia and VOCs gas recovery system for ammonia synthesis unit, characterized in that: include: For the synthetic ammonia nitrogen hydrogen combined compressor and the synthetic ammonia circulating gas compressor, a collection tank shall be added near the synthetic ammonia nitrogen hydrogen combined compressor and the synthetic ammonia circulating gas compressor to collect the sewage from the synthetic ammonia nitrogen hydrogen combined compressor and the synthetic ammonia circulating gas compressor in a centralized and closed manner; The top of the collecting tank is equipped with a local remote level gauge, nitrogen sealing facilities, sewage pipe inlet pipe and safety valve from right to left. The outlet pipe of the collecting tank is equipped with a local remote pressure gauge. A transmission pump is installed at the bottom of the left side of the collecting tank, and a solenoid valve is installed at the outlet of the transmission pump. A single call valve is installed at the outlet pipe of the collecting tank, and the ammonia-containing waste gas is sent to the saturator of the chemical plant after passing through the ammonia washing tower. The process interlocking system includes an interlocking device consisting of a transmission pump, a solenoid valve, and a local remote level gauge. The transmission pump and the solenoid valve are interlocked through the process interlocking system according to the liquid level displayed by the local remote level gauge, and the valves, pressure gauges and other electrical appliances at various positions are interlocked and controlled; The nitrogen sealing facility is a nitrogen sealing pressure stabilizing valve; When the outlet pipeline pressure reaches 20kPa, the single call valve opens automatically. When the pressure in the collection tank is ≤0.5KPa, the interlock opens the nitrogen replenishment valve. When the pressure in the collection tank rises to 2kPa, the interlock closes the nitrogen replenishment valve.

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