An oil type liquid ammonia delivery tank area flash gas recovery and explosion prevention optimization system

Abstract

The application discloses a kind of little oil type liquid ammonia conveying tank area flash gas recovery and explosion prevention optimization system, it is related to liquid ammonia production and storage field, including: liquid ammonia subcooler, normal pressure ammonia separator, cold ammonia pump, three-stage ammonia ice machine, ammonia compressor water cooler and ammonia receiving tank;The inlet of liquid ammonia subcooler is used to connect low pressure separator, the outlet of liquid ammonia subcooler is connected to the inlet of normal pressure ammonia separator, the bottom outlet of normal pressure ammonia separator is connected to the inlet of cold ammonia pump, the outlet of cold ammonia pump is used to connect to normal pressure tank area;The top outlet of normal pressure ammonia separator, three-stage ammonia ice machine, ammonia compressor water cooler and ammonia receiving tank are sequentially connected, the top outlet of ammonia receiving tank is connected with inert gas cooler for connecting to fuel gas pipe network;The bottom outlet of ammonia receiving tank is connected to the inlet of normal pressure ammonia separator.The application avoids the overpressure risk of normal pressure tank area, greatly reduces the safety investment cost, greatly improves ammonia recovery rate, and reduces loss.

Description

Technical Field

[0001] This invention relates to the field of liquid ammonia production and storage technology, and in particular to a low-oil liquid ammonia transport tank farm flash vapor recovery and explosion-proof optimization system. Background Technology

[0002] In small-scale ammonia synthesis projects using screw-type ammonia refrigeration systems, the liquid ammonia output from the low-pressure separator needs to be processed by a cooler before being transported to the atmospheric pressure tank area. However, during the transport process, when the pressure of the liquid ammonia at the outlet of the low-pressure separator (e.g., 1.6 MPa) suddenly drops to atmospheric pressure, flash evaporation occurs, producing ammonia-containing... ,hydrogen and nitrogen Flash vapor. If flash vapor directly enters the atmospheric pressure tank area, it will cause the pressure inside the tank to rise, posing a risk of overpressure explosion; at the same time, the flash vapor contains... (Approximately 6.5%) This will raise the explosion-proof requirements for atmospheric pressure tank areas, significantly increasing equipment investment and operation and maintenance costs. If flash vapor is directly sent to the fuel gas pipeline for combustion, the unrecovered ammonia (such as approximately 154.4 kg / h in a 190,000-ton / year synthetic ammonia unit) will cause significant product loss and reduce production efficiency.

[0003] The traditional solution is to flash the product ammonia to atmospheric pressure and then recover it through an ammonia compressor. However, this results in about 9.5 wt% of the product ammonia coming into contact with the compressor lubricating oil, causing ammonia carrying oil and seriously affecting product purity. Summary of the Invention

[0004] To address the technical problems existing in the background art, this invention proposes an optimized system for flash vapor recovery and explosion prevention in a low-oil liquid ammonia transport tank area.

[0005] The present invention proposes a low-oil liquid ammonia transport tank area flash vapor recovery and explosion-proof optimization system, comprising: a liquid ammonia subcooler, an atmospheric pressure ammonia separator, a cold ammonia pump, a three-stage ammonia ice machine, an ammonia compressor water cooler, an ammonia receiving tank, and an inert gas cooler; The inlet of the liquid ammonia subcooler is connected to the low-pressure separator, the outlet of the liquid ammonia subcooler is connected to the inlet of the atmospheric pressure ammonia separator, the bottom outlet of the atmospheric pressure ammonia separator is connected to the inlet of the cold ammonia pump, and the outlet of the cold ammonia pump is connected to the atmospheric pressure tank area; the top outlet of the atmospheric pressure ammonia separator is connected to the inlet of the three-stage ammonia refrigeration unit, the outlet of the three-stage ammonia refrigeration unit is connected to the inlet of the ammonia compressor water cooler, the outlet of the ammonia compressor water cooler is connected to the inlet of the ammonia receiving tank, the top outlet of the ammonia receiving tank is connected to the inlet of the inert gas cooler, and the outlet of the inert gas cooler is connected to the fuel gas pipeline network; the bottom outlet of the ammonia receiving tank is connected to the inlet of the atmospheric pressure ammonia separator.

[0006] Preferably, a feed regulating valve is connected between the inlet of the atmospheric pressure ammonia separator and the outlet of the liquid ammonia subcooler.

[0007] Preferably, the atmospheric pressure ammonia separator is equipped with a first liquid level control system, which is electrically connected to the feed regulating valve. The first liquid level control system is used to control the liquid level in the separator to be stable at a preset level by adjusting the opening of the feed regulating valve.

[0008] Preferably, a flash vapor outlet valve is connected between the top outlet of the atmospheric pressure ammonia separator and the inlet of the three-stage ammonia refrigeration unit.

[0009] Preferably, the atmospheric pressure ammonia separator is equipped with a pressure control system, which is electrically connected to the flash vapor outlet valve. The pressure control system is used to control the pressure inside the separator to stabilize at a preset pressure by adjusting the opening of the flash vapor outlet valve.

[0010] Preferably, a first liquid ammonia reflux valve is connected between the bottom outlet of the ammonia receiving tank and the inlet of the atmospheric pressure ammonia separator.

[0011] Preferably, the bottom outlet of the ammonia receiving tank is connected to the inlet of the inert gas cooler.

[0012] Preferably, a liquid level control valve is connected between the bottom outlet of the ammonia receiving tank and the inlet of the inert gas cooler.

[0013] Preferably, the ammonia receiving tank is equipped with a second liquid level control system, which is electrically connected to the liquid level control valve. The second liquid level control system is used to control the stability of the liquid level in the receiving tank by adjusting the opening of the liquid level control valve.

[0014] Preferably, the bottom outlet of the ammonia receiving tank is connected to the inlet of the liquid ammonia subcooler.

[0015] Preferably, the bottom outlet of the ammonia receiving tank is connected to the inlet of the liquid ammonia subcooler via a second liquid ammonia reflux valve.

[0016] Preferably, the outlet of the inert gas cooler is connected to the fuel gas pipeline via an exhaust gas valve.

[0017] In practice, the liquid ammonia subcooler is used to subcool the liquid ammonia from the low-pressure ammonia separator to -33°C; the atmospheric pressure ammonia separator is used to receive the subcooled liquid ammonia, allowing it to undergo flash evaporation at atmospheric pressure, separating it into liquid ammonia and flash vapor (containing ammonia, etc.). , The ammonia pump is used to pressurize and transport the flash-evaporated liquid ammonia to the atmospheric pressure tank area; the three-stage ammonia refrigeration unit is used to compress the flash vapor; the ammonia receiving tank is used to buffer and separate the compressed flash vapor; and the inert gas condenser is used to condense and recover inert gases. , The ammonia in the ammonia receiving tank; excess ammonia in the ammonia receiving tank is returned to the atmospheric pressure ammonia separator through pipelines to participate in the flash evaporation process again.

[0018] The proposed low-oil liquid ammonia transport tank area flash vapor recovery and explosion-proof optimization system in this invention completes the flash vaporization of liquid ammonia in an atmospheric pressure ammonia separator before transporting it to the atmospheric pressure tank area. This prevents secondary flash vaporization in the atmospheric pressure ammonia tank area, avoiding the risk of overpressure in the atmospheric pressure tank area. At the same time, H2 in the flash vapor has been separated, eliminating the need to upgrade the explosion-proof level of the atmospheric pressure tank area and significantly reducing safety investment costs. Moreover, after the flash vapor is treated by a three-stage ammonia refrigeration machine and an inert gas condenser, the ammonia recovery rate reaches 99.4%, greatly improving the ammonia recovery rate and reducing losses. Furthermore, through the design of a three-stage ammonia refrigeration machine, ammonia receiving tank, inert gas condenser, and closed-loop circulation circuit, this invention reduces the amount of ammonia in contact with lubricating oil from 2281 kg / h to 194.6 kg / h, a reduction of approximately 91.5%, compared to the traditional small-capacity synthetic ammonia scheme using a screw-type ammonia refrigeration machine as the refrigeration source. The oil content of the ammonia product can be controlled below 0.1 ppm, far exceeding the national superior product standard and fully meeting the application requirements of high-end industries. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a low-oil liquid ammonia transport tank area flash vapor recovery and explosion-proof optimization system in one embodiment of the present invention. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] Reference Figure 1 The present invention proposes a low-oil liquid ammonia transport tank area flash vapor recovery and explosion-proof optimization system, comprising: liquid ammonia subcooler 2, atmospheric pressure ammonia separator 3, cold ammonia pump 4, three-stage ammonia ice machine 5, ammonia compressor water cooler 6, ammonia receiving tank 7, and inert gas cooler 8; The inlet of liquid ammonia subcooler 2 is connected to low-pressure separator 1, and the outlet of liquid ammonia subcooler 2 is connected to the inlet of atmospheric pressure ammonia separator 3. The bottom outlet of atmospheric pressure ammonia separator 3 is connected to the inlet of cold ammonia pump 4, and the outlet of cold ammonia pump 4 is connected to the atmospheric pressure tank area. The top outlet of atmospheric pressure ammonia separator 3 is connected to the inlet of three-stage ammonia refrigeration machine 5, and the outlet of three-stage ammonia refrigeration machine 5 is connected to the inlet of ammonia compressor water cooler 6. The outlet of ammonia compressor water cooler 6 is connected to the inlet of ammonia receiving tank 7, and the top outlet of ammonia receiving tank 7 is connected to the inlet of inert gas cooler 8. The outlet of inert gas cooler 8 is connected to the fuel gas pipeline network. The bottom outlet of ammonia receiving tank 7 is connected to the inlet of atmospheric pressure ammonia separator 3, forming a circulation loop.

[0022] In specific implementation, the liquid ammonia subcooler 2 is used to subcool the liquid ammonia from the low-pressure ammonia separator to -33℃; the atmospheric pressure ammonia separator 3 is used to receive the subcooled liquid ammonia, allowing the liquid ammonia to complete flash evaporation at atmospheric pressure, separating it into liquid ammonia and gaseous flash vapor (containing ammonia, etc.). , ); Cold ammonia pump 4 is used to pressurize the flashed liquid ammonia (e.g., to 0.6 MPa) and transport it to the atmospheric pressure tank area; Three-stage ammonia refrigeration unit 5 is used to compress the flash vapor; Ammonia receiving tank 7 is used to buffer and separate the compressed flash vapor; Inert gas condenser is used to condense and recover inert gas ( , The ammonia in the ammonia receiving tank 7; excess ammonia in the ammonia receiving tank 7 is returned to the atmospheric pressure ammonia separator 3 through pipelines to participate in the flash evaporation process again.

[0023] This invention completes the flash evaporation of liquid ammonia in the atmospheric pressure ammonia separator 3 before it is transported to the atmospheric pressure tank area, thus preventing secondary flash evaporation in the atmospheric pressure tank area and avoiding the risk of overpressure in the atmospheric pressure tank area; at the same time, the H2 in the flash vapor has been separated, so there is no need to upgrade the explosion-proof level of the atmospheric pressure tank area, which greatly reduces the safety investment cost; Moreover, after the flash vapor is treated by the three-stage ammonia refrigeration machine 5 and the inert gas condenser, the ammonia recovery rate reaches 99.4%, which greatly improves the ammonia recovery rate. Only about 1 kg / h of ammonia is emitted with the tail gas. Based on the ammonia price of 4,000 yuan / ton, the annual ammonia loss can be reduced by about 492,000 yuan, thus reducing the loss. Furthermore, by employing a three-stage ammonia refrigeration unit 5, an ammonia receiving tank 7, an inert gas condenser, and a closed-loop circulation design, this invention reduces the amount of ammonia in contact with lubricating oil from 2281 kg / h to 194.6 kg / h, a reduction of approximately 91.5%, compared to traditional solutions. The ammonia product oil content can be controlled below 0.1 ppm, far exceeding the national superior product standard and fully meeting the application needs of high-end industries.

[0024] This invention modifies the existing process flow without requiring large-scale adjustments to the original production equipment, resulting in low modification costs and a short cycle.

[0025] In some embodiments, the three-stage ammonia refrigeration unit 5 is a screw compressor with an inlet pressure of -25 kPaG, an outlet pressure of 1.6 MPa, and a processing capacity of 223.7 Nm³ / h.

[0026] In some embodiments, the inert gas condenser is a shell-and-tube heat exchanger, and the cold source is liquid ammonia at a temperature of -38°C.

[0027] In some embodiments, the cold ammonia pump 4 is a cryogenic centrifugal pump with a head of 80m and a flow rate that matches the transportation needs of the atmospheric pressure tank area.

[0028] In some embodiments, a feed regulating valve 10 is connected between the inlet of the atmospheric pressure ammonia separator 3 and the outlet of the liquid ammonia subcooler 2.

[0029] Of course, the processing capacity of atmospheric pressure ammonia separator 3 is matched with the liquid ammonia flow rate at the outlet of the subcooler.

[0030] In some further embodiments, the atmospheric pressure ammonia separator 3 is provided with a first liquid level control system, which is electrically connected to the feed regulating valve 10. The first liquid level control system is used to control the liquid level in the separator to be stable at a preset liquid level by adjusting the opening of the feed regulating valve 10.

[0031] In some embodiments, a flash vapor outlet valve 11 is connected between the top outlet of the atmospheric pressure ammonia separator 3 and the inlet of the three-stage ammonia refrigeration machine 5, so as to control the flash vapor flow rate through the flash vapor outlet valve 11, thereby facilitating the control of the pressure of the atmospheric pressure ammonia separator 3.

[0032] In some further embodiments, the atmospheric pressure ammonia separator 3 is equipped with a pressure control system, which is electrically connected to the flash vapor outlet valve 11. The pressure control system is used to control the pressure inside the separator to stabilize at a preset pressure by adjusting the opening degree of the flash vapor outlet valve 11.

[0033] In some embodiments, a first liquid ammonia reflux valve is connected between the bottom outlet of the ammonia receiving tank 7 and the inlet of the atmospheric pressure ammonia separator 3, so as to control the ammonia reflux rate through the first liquid ammonia reflux valve.

[0034] In some embodiments, a level control valve 12 is connected between the bottom outlet of the ammonia receiving tank 7 and the inlet of the inert gas cooler 8.

[0035] In some further embodiments, the ammonia receiving tank 7 is provided with a second liquid level control system, which is electrically connected to the liquid level control valve 12. The second liquid level control system is used to control the liquid level in the receiving tank to stabilize by adjusting the opening of the liquid level control valve 12, thereby ensuring the smooth operation of the system.

[0036] In some embodiments, the bottom outlet of the ammonia receiving tank 7 is connected to the inlet of the liquid ammonia subcooler 2 so that excess ammonia can be recooled.

[0037] In some further embodiments, the bottom outlet of the ammonia receiving tank 7 is connected to the inlet of the liquid ammonia subcooler 2 via a second liquid ammonia reflux valve 9, so as to control the ammonia reflux rate through the second liquid ammonia reflux valve 9.

[0038] In some embodiments, the outlet of the inert gas cooler 8 is connected to the fuel gas pipeline via the exhaust gas valve 13 so as to control the emission rate via the exhaust gas valve 13.

[0039] The present invention will now be described in conjunction with specific embodiments.

[0040] Example 1

[0041] like Figure 1As shown, this embodiment discloses a low-oil liquid ammonia transport tank area flash vapor recovery and explosion-proof optimization system, including: liquid ammonia subcooler 2, atmospheric pressure ammonia separator 3, cold ammonia pump 4, three-stage ammonia ice machine 5, ammonia compressor water cooler 6, ammonia receiving tank 7, and inert gas cooler 8; The inlet of the liquid ammonia subcooler 2 is connected to the outlet of the low-pressure separator 1. The outlet of the liquid ammonia subcooler 2 is connected to the inlet of the atmospheric pressure ammonia separator 3 via the feed regulating valve 10. The bottom outlet of the atmospheric pressure ammonia separator 3 is connected to the inlet of the cold ammonia pump 4. The outlet of the cold ammonia pump 4 is connected to the atmospheric pressure tank area. The top outlet of the atmospheric pressure ammonia separator 3 is connected to the inlet of the three-stage ammonia refrigeration machine 5 via the flash vapor outlet valve 11. The outlet of the three-stage ammonia refrigeration machine 5 is connected to the ammonia compressor water cooler 6. The outlet of the ammonia compressor water cooler 6 is connected to the inlet of the ammonia receiving tank 7. The top outlet of the ammonia receiving tank 7 is connected to the inlet of the inert gas cooler 8. The outlet of the inert gas cooler 8 is connected to the fuel gas pipeline via the tail gas discharge valve 13. The bottom outlet of the ammonia receiving tank 7 is connected to the inlet of the atmospheric pressure ammonia separator 3 via the first liquid ammonia reflux valve, forming a closed-loop circulation circuit.

[0042] In practice, the liquid ammonia pressure in the low-pressure separator 1 is 1.6 MPa, and the temperature is -10℃. After flowing out of the outlet of the low-pressure separator 1, the liquid ammonia enters the liquid ammonia subcooler 2, where it is cooled to -33℃. The subcooled liquid ammonia then enters the atmospheric pressure ammonia separator 3 through the feed regulating valve 10. The atmospheric pressure ammonia separator 3 operates at atmospheric pressure (-25 kPaG slightly negative pressure), where the liquid ammonia completes the flash evaporation process, separating into liquid ammonia and gaseous flash vapor. The flash vapor components include 68% ammonia, 6.5% hydrogen, and 25.5% nitrogen. Liquid ammonia flows out from the bottom outlet of atmospheric pressure ammonia separator 3, is pressurized to 0.6MPa by cold ammonia pump 4 and then transported to atmospheric pressure tank area. Since the flash evaporation process has been completed in atmospheric pressure ammonia separator 3, no flash vapor is generated after liquid ammonia enters atmospheric pressure tank area, thus avoiding the overpressure risk of atmospheric pressure tank area from the source. At the same time, the hydrogen in flash vapor has been separated, so there is no need to upgrade the explosion protection level of atmospheric pressure tank area. The gaseous flash vapor flows out from the top outlet of the atmospheric pressure ammonia separator 3 and enters the three-stage ammonia refrigeration unit 5 through the flash vapor outlet valve 11. In the three-stage ammonia refrigeration unit 5, it is compressed to 1.6MPa. The compressed high-temperature gaseous ammonia enters the ammonia compressor water cooler 6 and is cooled to 40°C. The cooled gas-liquid mixture enters the ammonia receiving tank 7 for gas-liquid separation. The non-condensable gases (hydrogen, nitrogen and a small amount of uncondensed ammonia) at the top of the ammonia receiving tank 7 enter the inert gas cooler 8, where liquid ammonia at -38°C is used as a cold source for deep condensation to recover the ammonia components. The liquid ammonia at the bottom of the ammonia receiving tank 7 returns to the atmospheric pressure ammonia separator 3 through the first liquid ammonia reflux valve, re-participates in the flash evaporation process, and returns to the liquid ammonia subcooler 2 through the second liquid ammonia reflux valve 9, forming a closed-loop recovery circuit. The pressure control system of the atmospheric ammonia separator 3 controls the pressure inside the separator to be stable at -25 kPaG by adjusting the opening of the flash vapor outlet valve 11; the first liquid level control system of the atmospheric ammonia separator 3 controls the liquid level inside the atmospheric ammonia separator 3 to be stable at 50% ± 5% by adjusting the opening of the feed regulating valve 10; the second liquid level control system on the ammonia receiving tank 7 controls the liquid level inside the ammonia receiving tank 7 to be stable by adjusting the opening of the liquid level control valve 12, ensuring the smooth operation of the system.

[0043] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A flash vapor recovery and explosion-proof optimization system for low-oil liquid ammonia transport tank areas, characterized in that, include: Liquid ammonia subcooler, atmospheric pressure ammonia separator, cold ammonia pump, three-stage ammonia ice machine, ammonia compressor water cooler, ammonia receiving tank and inert gas cooler; The inlet of the liquid ammonia subcooler is connected to the low-pressure separator, the outlet of the liquid ammonia subcooler is connected to the inlet of the atmospheric pressure ammonia separator, the bottom outlet of the atmospheric pressure ammonia separator is connected to the inlet of the cold ammonia pump, and the outlet of the cold ammonia pump is connected to the atmospheric pressure tank area; the top outlet of the atmospheric pressure ammonia separator is connected to the inlet of the three-stage ammonia refrigeration unit, the outlet of the three-stage ammonia refrigeration unit is connected to the inlet of the ammonia compressor water cooler, the outlet of the ammonia compressor water cooler is connected to the inlet of the ammonia receiving tank, the top outlet of the ammonia receiving tank is connected to the inlet of the inert gas cooler, and the outlet of the inert gas cooler is connected to the fuel gas pipeline network; the bottom outlet of the ammonia receiving tank is connected to the inlet of the atmospheric pressure ammonia separator.

2. The flash vapor recovery and explosion-proof optimization system for low-oil liquid ammonia transport tank areas according to claim 1, characterized in that, A feed regulating valve is connected between the inlet of the atmospheric pressure ammonia separator and the outlet of the liquid ammonia subcooler.

3. The flash vapor recovery and explosion-proof optimization system for low-oil liquid ammonia transport tank areas according to claim 2, characterized in that, The atmospheric pressure ammonia separator is equipped with a first liquid level control system, which is electrically connected to the feed regulating valve. The first liquid level control system is used to control the liquid level in the separator to be stable at a preset level by adjusting the opening of the feed regulating valve.

4. The flash vapor recovery and explosion-proof optimization system for low-oil liquid ammonia transport tank areas according to claim 1, characterized in that, A flash vapor outlet valve is connected between the top outlet of the atmospheric pressure ammonia separator and the inlet of the three-stage ammonia refrigeration unit.

5. The flash vapor recovery and explosion-proof optimization system for low-oil liquid ammonia transport tank areas according to claim 4, characterized in that, The atmospheric pressure ammonia separator is equipped with a pressure control system, which is electrically connected to the flash vapor outlet valve. The pressure control system is used to control the pressure inside the separator to stabilize at a preset pressure by adjusting the opening of the flash vapor outlet valve.

6. The flash vapor recovery and explosion-proof optimization system for low-oil liquid ammonia transport tank areas according to claim 1, characterized in that, A first liquid ammonia reflux valve is connected between the bottom outlet of the ammonia receiving tank and the inlet of the atmospheric pressure ammonia separator.

7. The flash vapor recovery and explosion-proof optimization system for low-oil liquid ammonia transport tank areas according to claim 1, characterized in that, The bottom outlet of the ammonia receiving tank is connected to the inlet of the liquid ammonia subcooler; The bottom outlet of the ammonia receiving tank is connected to the inlet of the liquid ammonia subcooler via a second liquid ammonia reflux valve.

8. The flash vapor recovery and explosion-proof optimization system for low-oil liquid ammonia transport tank areas according to claim 1, characterized in that, The bottom outlet of the ammonia receiving tank is connected to the inlet of the inert gas cooler.

9. The flash vapor recovery and explosion-proof optimization system for low-oil liquid ammonia transport tank areas according to claim 7, characterized in that, The bottom outlet of the ammonia receiving tank and the inlet of the inert gas cooler are connected by a level control valve.

10. The flash vapor recovery and explosion-proof optimization system for low-oil liquid ammonia transport tank areas according to claim 8, characterized in that, The ammonia receiving tank is equipped with a second liquid level control system, which is electrically connected to the liquid level control valve. The second liquid level control system is used to control the liquid level in the receiving tank to stabilize by adjusting the opening of the liquid level control valve.

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