Liquid ammonia spherical tank pressure control device

Abstract

The utility model relates to a liquid ammonia spherical tank pressure control device which comprises a pressure reducing pipeline and a pressure supplementing pipeline, the pressure supplementing pipeline comprises a pump inlet pipeline, a delivery pump, an ammonia removal heat exchanger pipeline and a pressure supplementing pipeline which are connected in sequence, a pump backflow pipeline is further connected between the discharging end of the delivery pump and the feeding end of the pump inlet pipeline in parallel, and a pressure supplementing pipeline is further connected between the delivery pump and the feeding end of the pressure supplementing pipeline. The ammonia removal heat exchanger pipeline is also connected with a downstream removal pipeline; a control valve I is arranged at the feeding end of the downstream removal pipeline; the pressure reduction pipeline comprises a pressure reduction feeding pipeline, a control valve II, a one-way valve I, a gas-liquid separator, an ammonia refrigerator unit and a low-temperature liquid ammonia storage tank removal pipeline which are connected in sequence; when the pressure in the liquid ammonia spherical tank is low, the storage pressure in the liquid ammonia spherical tank can be increased through the pressure supplementing pipeline, that is, materials in the liquid ammonia spherical tank are heated through the steam heat exchanger, liquid-phase materials are heated and converted into gas-phase materials, and the gas-phase materials return to the spherical tank, so that the pressurization effect is achieved.

Description

Technical Field

[0001] This utility model relates to the field of pressure control technology for spherical tanks, specifically a pressure control device for liquid ammonia spherical tanks. Background Technology

[0002] With the continuous development of China's chemical industry, liquid ammonia storage and transportation technology has become increasingly mature. Because ammonia is gaseous at normal pressure, it must be stored in cryogenic tanks or pressurized spherical tanks. Cryogenic liquid ammonia storage tanks operate at normal pressure and a temperature of approximately -32℃. Liquid ammonia spherical tanks operate at a pressure of approximately 0.5-1.2 MPa and a temperature of ambient temperature. The pressure of liquid ammonia spherical tanks varies significantly with ambient temperature, requiring appropriate measures for pressure control in both winter and summer.

[0003] When the pressure in a liquid ammonia spherical tank becomes excessively high in summer, spraying is typically used to cool the outer wall of the tank, or a refrigeration unit is used to control the tank pressure. However, external cooling methods waste a lot of water, and installing a separate refrigeration unit requires a large investment and occupies a significant area. If the pressure continues to rise, the tank pressure can only be controlled by opening the local manual valve or until the safety valve trips and discharges through a flare. The inability to open or close the local manual valve in a timely manner is also detrimental to personnel safety, while the tripping of the safety valve constitutes a production accident, which is detrimental to production safety and stable operation.

[0004] When the pressure of liquid ammonia spherical tanks drops in winter, nitrogen is usually added to maintain the pressure. However, this method will cause the content of non-condensable gases in the spherical tanks to increase, resulting in excessively high and uncontrollable pressure in the spherical tanks in summer. During the non-condensable gas emission process, ammonia is emitted simultaneously, causing material loss and environmental problems.

[0005] Therefore, pressure control of liquid ammonia spherical tanks is particularly important. Utility Model Content

[0006] The technical problem to be solved by this utility model is to address the shortcomings of the existing technology by providing a liquid ammonia tank pressure control device that can increase or decrease the pressure of liquid ammonia tanks in a factory area.

[0007] The technical problem to be solved by this utility model is achieved through the following technical solution: a pressure control device for a liquid ammonia spherical tank, the device including a pressure reducing pipeline and a pressure replenishing pipeline, the pressure reducing pipeline being located at the top of the liquid ammonia spherical tank and the pressure replenishing pipeline being located at the bottom of the liquid ammonia spherical tank;

[0008] The pressurization pipeline includes a pump inlet pipeline, a transfer pump, an ammonia heat exchanger pipeline, and a pressurization pipeline connected in sequence. The feed end of the pump inlet pipeline is connected to the bottom of the liquid ammonia spherical tank. A steam heat exchanger is installed between the discharge end of the ammonia heat exchanger pipeline and the feed end of the pressurization pipeline. The discharge end of the pressurization pipeline is connected to the top of the liquid ammonia spherical tank. A pump return pipeline is also connected in parallel between the discharge end of the transfer pump and the feed end of the pump inlet pipeline. A downstream pipeline is also connected to the ammonia heat exchanger pipeline. A control valve I is installed at the feed end of the ammonia heat exchanger pipeline.

[0009] The pressure-reducing pipeline includes a pressure-reducing feed pipeline, control valve II, check valve I, gas-liquid separator, ammonia refrigeration unit, and pipeline to cryogenic liquid ammonia storage tank connected in sequence.

[0010] It also includes the flare system pipeline connected to the flare system, with the inlet end of the flare system pipeline connected to the top of the liquid ammonia spherical tank.

[0011] The technical problem to be solved by this utility model can also be achieved through the following technical solution: the pressure control device for liquid ammonia spherical tank described above is provided with a bypass pipeline on the pressure-reducing feed pipeline between the feed end and the discharge end of control valve II, and control valve III is installed on the bypass pipeline.

[0012] The technical problem to be solved by this utility model can also be achieved through the following technical solution: the liquid ammonia spherical tank pressure control device described above is equipped with valve bodies on the pump inlet pipeline, the ammonia heat exchanger pipeline, the pressure replenishment pipeline, the pressure reducing and feeding pipeline, and the pipeline to the cryogenic liquid ammonia storage tank.

[0013] Compared with the prior art, the beneficial technical effects of this utility model are:

[0014] (1) When the internal pressure of the liquid ammonia spherical tank is low, the storage pressure inside the liquid ammonia spherical tank can be increased through the pressure replenishment pipeline. That is, the material inside the liquid ammonia spherical tank is heated by the steam heat exchanger, and the liquid phase material is heated and converted into gas phase material and returned to the spherical tank to achieve the pressurization effect.

[0015] (2) When the internal pressure of the liquid ammonia sphere tank is high, the ammonia gas accumulated at the top of the liquid ammonia sphere tank can be cooled and liquefied by a refrigeration unit, and then transported to other storage tanks in the plant area through the pipeline to the low-temperature liquid ammonia storage tank, or the excess ammonia gas in the liquid ammonia sphere tank can be transported to the flare system in the plant area for combustion through the flare system pipeline, thereby reducing material emissions and increasing the safety of personnel operation. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the pipeline for pressure control of the liquid ammonia spherical tank according to this utility model.

[0017] Attached reference numerals: 1. Liquid ammonia spherical tank; 2. Pump inlet line; 3. Transfer pump; 4. Ammonia heat exchanger line; 5. Pressure replenishment line; 6. Steam heat exchanger; 7. Pump return line; 8. Downstream line; 9. Control valve I; 10. Pressure reducing and feeding line; 11. Control valve II; 12. Check valve I; 13. Gas-liquid separator; 14. Ammonia refrigeration unit; 15. Line to cryogenic liquid ammonia storage tank; 16. Bypass line; 17. Control valve III; 18. Flare system line. Detailed Implementation

[0018] The specific technical solutions of this utility model are further described below with reference to the accompanying drawings, so as to enable those skilled in the art to further understand this utility model, without constituting a limitation on its rights.

[0019] Example 1, referring to Figure 1 A pressure control device for a liquid ammonia spherical tank, the device comprising a pressure reducing pipeline and a pressure replenishing pipeline, the pressure reducing pipeline being located at the top of the liquid ammonia spherical tank 1 and the pressure replenishing pipeline being located at the bottom of the liquid ammonia spherical tank 1;

[0020] The pressure replenishment pipeline includes a pump inlet line 2, a conveying pump 3, an ammonia heat exchanger line 4, and a pressure replenishment line 5 connected in sequence. The feed end of the pump inlet line 2 is connected to the bottom of the liquid ammonia spherical tank 1. A steam heat exchanger 6 is installed between the discharge end of the ammonia heat exchanger line 4 and the feed end of the pressure replenishment line. The discharge end of the pressure replenishment line 5 is connected to the top of the liquid ammonia spherical tank 1. A pump return line 7 is also connected in parallel between the discharge end of the conveying pump 3 and the feed end of the pump inlet line 2. A downstream line 8 is also connected to the ammonia heat exchanger line 4. A control valve I is installed at the feed end of the ammonia heat exchanger line. The downstream line 8 is used for material outgoing. If the pressure in the spherical tank is low during outgoing, the pressure in the spherical tank can be increased by going to the heater through the ammonia heat exchanger line 4.

[0021] The pressure-reducing pipeline includes a pressure-reducing feed line 10, a control valve II 11, a check valve I 12, a gas-liquid separator 13, an ammonia refrigeration unit 14, and a pipeline to a cryogenic liquid ammonia storage tank connected in sequence. A bypass line 16 is also provided on the pressure-reducing feed line 10 between the feed end and the discharge end of the control valve II 11, and a control valve III 17 is installed on the bypass line 16.

[0022] Valve bodies are installed on the pump inlet pipeline 2, the ammonia heat exchanger pipeline 4, the pressure replenishment pipeline 5, the pressure reducing and feeding pipeline 10, and the pipeline to the cryogenic liquid ammonia storage tank 15.

[0023] It also includes a flare system pipeline 18 connected to the flare system, with the inlet end of the flare system pipeline 18 connected to the top of the liquid ammonia spherical tank 1.

[0024] The operation process of the pressure control device for the liquid ammonia spherical tank is as follows:

[0025] (1) Increase the pressure of the spherical tank: When the pressure of the liquid ammonia spherical tank is low (close to 0.5 MPa), start the transfer pump 3 to provide power, pressurize and transfer the liquid ammonia to the steam heat exchanger 6, and heat it with steam to heat the liquid ammonia into ammonia gas and return it to the liquid ammonia spherical tank 1, thereby increasing the pressure of the liquid ammonia spherical tank 1. According to the usage requirements, a heat insulation layer (heat insulation cotton, etc.) (not shown in the figure) can be installed on the outer circumference of the outlet pipe of the steam heat exchanger 6 to prevent the low winter temperature from causing excessive heat loss and the ammonia gas to liquefy with the air in the pipe, which would affect the pressurization effect. In addition, a regulating valve can be set on the ammonia heat exchanger pipeline 4, and a temperature detection can be set on the steam heater outlet pipeline. The flow rate of liquid ammonia and steam heater can be adjusted according to the tank pressure to control the heater outlet temperature. A DCS loop control logic can be set to realize automatic control of the tank pressure and the steam heater outlet temperature to control the pressure of the liquid ammonia spherical tank 1. The usage principle and implementation method of this DCS interlock control logic are existing technologies, so its specific process will not be described here.

[0026] (2) Reduce tank pressure: When the tank pressure rises (close to 2.07 MPa), the pressure is reduced by depressurizing the cryogenic storage tank refrigeration unit. The ammonia gas at the top of the liquid ammonia tank 1 passes through the pressure reducing feed line 10, control valve II 11, check valve I 12 and gas-liquid separator 13. Because ammonia is easily liquefied, a gas-liquid separator 13 is set before the inlet of the ammonia refrigeration unit 14 to prevent the compressor from carrying liquid and affecting the operation of the equipment. Finally, the ammonia gas enters the ammonia refrigeration unit 14 and, after being liquefied, enters the pipeline to the cryogenic liquid ammonia storage tank 15. The high liquid level interlock protection of the gas-liquid separator 13 can be set according to the usage requirements to keep the equipment in a safe state and achieve the purpose of reducing the tank pressure. When the tank pressure continues to rise and the cryogenic storage tank refrigeration unit is insufficient, the regulating valve for flare discharge can be opened to reduce the pressure by discharging part of the ammonia gas. Both of these pressure relief measures can reduce material discharge to a certain extent and avoid the occurrence of safety production accidents.

Claims

1. A pressure control device for a liquid ammonia spherical tank, characterized in that: The device includes a pressure-reducing pipeline and a pressure-replenishing pipeline. The pressure-reducing pipeline is located at the top of the liquid ammonia spherical tank, and the pressure-replenishing pipeline is located at the bottom of the liquid ammonia spherical tank. The pressurization pipeline includes a pump inlet pipeline, a transfer pump, an ammonia heat exchanger pipeline, and a pressurization pipeline connected in sequence. The feed end of the pump inlet pipeline is connected to the bottom of the liquid ammonia spherical tank. A steam heat exchanger is installed between the discharge end of the ammonia heat exchanger pipeline and the feed end of the pressurization pipeline. The discharge end of the pressurization pipeline is connected to the top of the liquid ammonia spherical tank. A pump return pipeline is also connected in parallel between the discharge end of the transfer pump and the feed end of the pump inlet pipeline. A downstream pipeline is also connected to the ammonia heat exchanger pipeline. A control valve I is installed at the feed end of the ammonia heat exchanger pipeline. The pressure-reducing pipeline includes a pressure-reducing feed pipeline, control valve II, check valve I, gas-liquid separator, ammonia refrigeration unit, and pipeline to cryogenic liquid ammonia storage tank connected in sequence. It also includes the flare system pipeline connected to the flare system, with the inlet end of the flare system pipeline connected to the top of the liquid ammonia spherical tank.

2. The pressure control device for a liquid ammonia spherical tank according to claim 1, characterized in that: A bypass line is also installed on the pressure-reducing feed line between the inlet and outlet ends of control valve II, and control valve III is installed on the bypass line.

3. The pressure control device for a liquid ammonia spherical tank according to claim 1, characterized in that: Valve bodies are installed on the pump inlet pipeline, ammonia heat exchanger pipeline, pressure replenishment pipeline, pressure reducing feed pipeline, and pipeline to cryogenic liquid ammonia storage tank.

Images