Liquid Ammonia Storage Tank Maintenance Pressure Test Method

Abstract

The invention discloses a liquid ammonia storage tank maintenance pressure test method, which is used for testing the liquid ammonia storage tank, and the steps include: S100. emptying the liquid ammonia storage tank; S200. replacing the tank body with clean water; S300. tank body maintenance; S400. water pressure test; S500. airtightness test; S600. nitrogen discharge from the tank body. By adopting the new maintenance pressure test method, not only the work efficiency is improved, but also the construction personnel's stay time at the ammonia station is reduced, thereby improving safety.

Description

Technical Field

[0001] The invention relates to the technical field of liquid ammonia storage tanks, in particular to a liquid ammonia storage tank maintenance and pressure testing method. Background Art

[0002] According to the requirements of "TSG 21-2016 Technical Specifications for Safety of Special Equipment", 3.1.17 Pressure Test, pressure vessels shall be subjected to pressure test. Pressure test is divided into three types: hydraulic test, airtight test and gas-liquid combined pressure test. 3.1.18 Leakage test, after passing the pressure test, a leakage test shall be carried out for pressure vessels that contain extremely or highly toxic media or that are not designed to allow trace leakage. Leakage tests are divided into airtight tests, ammonia leak tests, halogen leak tests and helium leak tests, depending on the test medium. The liquid ammonia storage tank for flue gas denitrification in power plants is a pressure vessel that contains toxic hazards and is not designed to allow trace leakage. Therefore, during the regular inspection of the tank body, it is necessary to wait until the tank body is replaced and emptied before conducting an internal inspection. After the inspection is passed, a water pressure test and an airtight test shall be conducted.

[0003] The internal cleaning, inspection and pressure testing of the liquid ammonia storage tanks at the ammonia station requires an airtightness test. An air compressor is usually used to inject compressed air into the tank. The entire air pressure test process lasts for a long time and takes 4-5 days. The risk of a long-term airtightness test is relatively high, mainly because the gas is highly compressible. If the container or accessories are damaged during the airtightness test, the compressed air must not only release the accumulated energy, but also restore the volume compressed during the pressure increase process as quickly as possible, so its destructive power is extremely great. In addition, the construction workers stay in the ammonia station for a long time, and the safety risk of personnel being exposed to major hazard sources is greatly increased. Summary of the invention

[0004] In order to overcome the deficiencies of the prior art, the present invention provides a liquid ammonia storage tank maintenance pressure testing method.

[0005] The technical solution adopted by the present invention to solve the technical problem is: to provide a liquid ammonia storage tank maintenance pressure test method for testing the liquid ammonia storage tank, the steps comprising:

[0006] S100. Emptying the liquid ammonia storage tank: emptying the interior of the liquid ammonia storage tank;

[0007] S200. Replace the tank with clean water and fill the liquid ammonia storage tank with enough clean water;

[0008] S300. Tank maintenance, maintenance work on the liquid ammonia storage tank;

[0009] S400. A hydraulic pressure test is performed on the liquid ammonia storage tank;

[0010] S500. Airtightness test: liquid nitrogen is gasified and pressurized and injected into the liquid ammonia storage tank, and clean water in the liquid ammonia storage tank is discharged to perform an airtightness test;

[0011] S600. Discharge nitrogen from the tank, reduce and maintain a predetermined low pressure of nitrogen in the liquid ammonia storage tank, and discharge the nitrogen in the liquid ammonia storage tank.

[0012] The liquid ammonia storage tank maintenance and pressure testing method provided by the present invention not only improves work efficiency but also reduces the time construction workers stay at the ammonia station, thereby improving safety by adopting a new maintenance and pressure testing method.

[0013] As some preferred embodiments of the present invention, after the water pressure test in step S400, if the test fails, the tank body is inspected in step S300.

[0014] As some preferred embodiments of the present invention, after the airtightness test in step S500, if the test fails, the tank body is inspected in step S300.

[0015] As some preferred embodiments of the present invention, when clean water is injected into the clean water replacement tank in step S200, the water pressure of the liquid ammonia storage tank is monitored in real time by a pressure sensor of the liquid ammonia storage tank.

[0016] As some preferred embodiments of the present invention, in the step S600 of discharging nitrogen from the tank, the nitrogen pressure in the liquid ammonia storage tank is higher than the external air pressure.

[0017] As some preferred embodiments of the present invention, the liquid ammonia storage tank is connected to a purge input pipe and a sewage discharge pipe.

[0018] As some preferred embodiments of the present invention, the liquid ammonia storage tank is connected to a liquid ammonia input pipe and a liquid ammonia output pipe.

[0019] As some preferred embodiments of the present invention, the liquid ammonia storage tank is connected to a gaseous ammonia output pipe for connecting to an outlet of a liquid ammonia evaporator.

[0020] As some preferred embodiments of the present invention, the liquid ammonia storage tank is connected to a waste ammonia discharge pipe for connecting to an ammonia absorption tank.

[0021] As some preferred embodiments of the present invention, the liquid ammonia storage tank is connected to an ammonia unloading pipe for connecting to an ammonia unloading compressor.

[0022] The beneficial effects of the present invention are:

[0023] 1. The new maintenance and pressure test process can greatly shorten the maintenance period, save labor costs, improve work efficiency, and reduce the time construction workers stay in the ammonia station, reducing the safety risks of personnel exposed to major hazardous source areas;

[0024] 2. Optimizing the maintenance process can reduce the time of effective airtightness testing. For example, it takes 4-5 days to conduct air pressure testing using compressed air. The air pressure testing process is relatively risky. Reducing the pressurization time can reduce the safety risks of the testing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0026] Figure 1 It is a schematic diagram of the device structure of the present invention;

[0027] Figure 2 It is a schematic diagram of the process of the present invention.

[0028] Reference numerals:

[0029] Liquid ammonia storage tank 100; purge input pipe 200, sewage pipe 210; liquid ammonia input pipe 300, liquid ammonia output pipe 310; gas ammonia output pipe 400; waste ammonia discharge pipe 500; ammonia unloading pipe 600. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. In order to thoroughly understand the present invention, some specific details will be involved in the following description. However, the present invention can still be implemented without these specific details, that is, technicians in the field can use these descriptions and statements here to more effectively introduce the essence of their work to other technicians in the field.

[0031] In addition, it should be noted that the words "inside" and "outside" refer to the directions toward or away from the geometric center of a specific component, respectively, and simple, non-creative adjustments made to the above directions by relevant technical personnel should not be construed as technologies outside the scope of protection of this application.

[0032] If described as "first", "second", etc., it is only used for the purpose of distinguishing technical features and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0033] It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the actual protection scope. In order to avoid confusing the purpose of the present invention, the technical details of the well-known manufacturing methods, control procedures, component sizes, material compositions, pipeline layouts, etc. are not described in detail because they are already easy to understand.

[0034] Figure 1 is a schematic diagram of the device structure of an embodiment of the present invention, referring to Figure 1One embodiment of the present invention provides a liquid ammonia storage tank maintenance pressure test method for testing a liquid ammonia storage tank 100.

[0035] Further, see Figure 2 , the liquid ammonia storage tank maintenance pressure test method steps include:

[0036] S100. The liquid ammonia storage tank is emptied, and the interior of the liquid ammonia storage tank 100 is emptied;

[0037] S200. Replace the tank with clean water and fill the liquid ammonia storage tank 100 with enough clean water;

[0038] S300. Tank maintenance: perform maintenance work on the liquid ammonia storage tank 100;

[0039] S400. Hydrostatic test: perform a hydrostatic test on the liquid ammonia storage tank 100;

[0040] S500. Airtightness test: liquid nitrogen is gasified and pressurized and injected into the liquid ammonia storage tank 100, and the water in the liquid ammonia storage tank 100 is discharged to perform an airtightness test;

[0041] S600. The tank body discharges nitrogen, reduces and maintains a predetermined low pressure of nitrogen in the liquid ammonia storage tank 100, discharges nitrogen in the liquid ammonia storage tank 100, and maintains a low pressure state in the liquid ammonia storage tank 100 to prevent air from entering.

[0042] That is, after the water pressure test in step S400 is completed, the liquid ammonia storage tank 100 directly enters the air tightness test in step S500, and the compressed air pressure test is replaced by the nitrogen pressure test. Nitrogen is injected into the liquid ammonia storage tank 100, and clean water in the liquid ammonia storage tank 100 is discharged at the same time to ensure that no air enters the liquid ammonia storage tank 100 after drainage, which can effectively prevent the risk of explosion caused by the mixing of liquid ammonia injected after maintenance and the air in the tank.

[0043] The above disclosed method for inspecting and testing the pressure of a liquid ammonia storage tank is only a preferred embodiment of the present invention, and is only used to illustrate the technical solution of the present invention, but not to limit it. The following is further described in conjunction with some embodiments, wherein the "embodiment" referred to herein refers to a specific feature, structure or characteristic that can be included in at least one implementation of the present application.

[0044] In some embodiments, during the evacuation of the liquid ammonia storage tank in step S100, after the liquid ammonia storage tank 100 is isolated, the top evacuation door of the liquid ammonia storage tank 100 is opened to allow the ammonia in the liquid ammonia storage tank 100 to be naturally discharged to the ammonia dilution tank, thereby reducing the pressure of the liquid ammonia storage tank 100. During the evaporation and pressure reduction process of the liquid ammonia in the liquid ammonia storage tank 100, the outer wall of the storage tank may be frosted at low temperature due to the heat absorption of evaporation, so it is necessary to replace the tank body with clean water in step S200, and prepare clean water to spray the liquid ammonia storage tank 100 body.

[0045] In some embodiments, in step S200, in which the tank is replaced with clean water, the specific steps include:

[0046] S210. When the pressure of the liquid ammonia storage tank 100 drops to 0-0.02MPa, close the safety isolation door of the liquid ammonia storage tank 100, slowly open the bottom discharge door of the liquid ammonia storage tank 100 to discharge sewage, and ensure that the wastewater pool is at a high water level before discharging sewage (to prevent the storage tank from generating zero pressure or negative pressure).

[0047] S220. After the liquid ammonia storage tank 100 is discharged, the rear flange of the primary door (closed state) on the top of the liquid ammonia storage tank 100 is removed, and after the temporary pipe is connected, the valve is opened to inject clean water for replacement.

[0048] S230. After the replacement process is completed, all pipe openings connected to the liquid ammonia storage tank 100 need to be equipped with plugging plates to prevent accidental contact during the construction process and ammonia backflow.

[0049] In some embodiments, when clean water is injected into the clean water replacement tank in step S200, the water pressure of the liquid ammonia storage tank 100 is monitored in real time through the pressure sensor of the liquid ammonia storage tank 100, which not only ensures safety but also facilitates the detection of real-time data.

[0050] In some embodiments, during the tank body inspection in step S300, after the tank body is replaced with clean water in the previous step S200, S310 is performed. Clean water is continued to be used to rinse the inside of the tank body, and the debris in the tank is further cleaned after the ammonia and oxygen content in the tank meets the standard.

[0051] In this embodiment, optionally, step S300 of tank body overhaul includes step S320 of disassembling and assembling pipe valve bolts, and the specific steps include:

[0052] S321. Remove the safety valve of the liquid ammonia tank and send it for inspection, then reinstall it after passing the inspection.

[0053] S322. Anti-static jumper wires must be installed simultaneously during bolt installation.

[0054] S323. Remove the flange bolts within the isolation range. The pressure should be released before removal. The bolts of the same flange cannot be removed all at the same time. After removing each bolt, a new bolt should be installed immediately and tightened with a torque wrench.

[0055] In this embodiment, preferably, the jumper wire in step S322 is provided by the construction party.

[0056] In this embodiment, preferably, the flange connection in step S322 should use bolts of the same specification and the installation direction should be consistent.

[0057] In this embodiment, preferably, the fastening bolts in step S322 should be symmetrical and uniform, and of appropriate tightness, and the bolt torques corresponding to fastening bolts of different models are determined according to pre-established standards.

[0058] In some embodiments, the specific process of the water pressure test in step S400 includes:

[0059] S410. Water pressure test 2.5MPa (liquid ammonia storage tank 100).

[0060] S420. Water filling: Use clean water (domestic water, industrial water or fire water) to fill the liquid ammonia storage tank until water overflows from the top, and then all the main body primary doors can be closed.

[0061] S430. Boost pressure. The outlet pipe of the electric pressure test pump is connected to the valve on the top of the tank to prepare for the water pressure test. The power supply of the pressure test pump (380V) can be taken from the power distribution room of No. 1 and No. 2 ammonia stations or the maintenance power box at the dock. The following three situations during the boost process indicate that the gas in the pipeline has not been completely exhausted and the exhaust should continue:

[0062] S431. When increasing pressure, the water pump continuously fills water, but the pressure increase is very slow. The pressure increase speed is preferably ≤0.2-0.3MPa / min;

[0063] S432. When increasing pressure, the pressure gauge pointer swings greatly and the reading is unstable;

[0064] S433. When the pressure is increased to 80%, stop increasing the pressure, open the water valve, there will be a "thump thump" sound in the water column and many bubbles will be ejected; increase the pressure in stages, 0.2Mpa as one stage each time, and continue to increase the pressure only after it is confirmed that there are no abnormalities; during the water pressure test, it is strictly forbidden to stand on the back support and both ends of the pipe; in case of defects, they should be marked and repaired after the pressure is released.

[0065] S440. Requirements and standards for water pressure test: Maintain pressure at 2.5MPa for 30 minutes without any drop, leakage, or visible deformation of the equipment.

[0066] In some embodiments, after the water pressure test in step S400, if the test fails, the tank body is inspected and repaired in step S300 to promptly address the problems of the liquid ammonia storage tank 100 found in the test.

[0067] In some embodiments, in the airtight test of step S500, the airtight test pressure is 2.4 MPa (liquid ammonia storage tank), and the medium is nitrogen.

[0068] In some embodiments, the specific process of the airtight test in step S500 includes:

[0069] S510. After the water pressure test of the liquid ammonia storage tank is completed, drain the water. When the body pressure drops to 0.1MPa, start injecting nitrogen (nitrogen gas taken from the gasified liquid nitrogen tank truck) to conduct an airtight test. After the nitrogen is connected, continue to drain the tank until it is empty (only nitrogen gas flows out), and close the valve.

[0070] S520. If there is no abnormality, then gradually increase the pressure by 10% of the specified test pressure until the test pressure is reached and maintain the pressure for 30 minutes. Then reduce the pressure to at least 87% of the specified test pressure and maintain the pressure for a sufficient time for inspection. The pressure should remain unchanged during the inspection and continuous pressurization shall not be used to maintain the test pressure unchanged.

[0071] S530. During the airtightness test, it is strictly prohibited to tighten the bolts under pressure or apply external force to the pressure-bearing components.

[0072] S540. Nitrogen replacement is completed, and the system pressure is maintained above 0.1MPa to prepare for ammonia injection.

[0073] In some embodiments, the requirements and standards for the airtight test in step S500 are:

[0074] There is no abnormal sound from the pressure vessel and pipe valves;

[0075] Check for leaks with soap solution or other leak detection fluid;

[0076] No visible deformation.

[0077] In some embodiments, after the airtightness test in step S500, if the test fails, the tank body is inspected and repaired in step S300 to promptly address the problems of the liquid ammonia storage tank 100 found in the test.

[0078] In some embodiments, in the airtightness test of step S500, the liquid nitrogen in the tank truck is gasified and then injected into the liquid ammonia storage tank 100.

[0079] In some embodiments, during the step S600 of discharging nitrogen from the tank, after the nitrogen retained in the liquid ammonia storage tank 100 passes the water pressure test, it can be regarded as a standby state and ammonia can be injected at any time.

[0080] In some embodiments, during the tank nitrogen discharge in step S600, the nitrogen pressure in the liquid ammonia storage tank 100 is higher than the external pressure.

[0081] In some embodiments, the liquid ammonia storage tank 100 is connected to a purge input pipe 200 and a sewage pipe 210. In step S200, the clean water in the clean water replacement tank is sprayed and cleaned by the clean water in the purge input pipe 200, and the sewage is discharged through the sewage pipe 210.

[0082] In this embodiment, optionally, the purge inlet pipe 200 is provided with a purge inlet pipe nitrogen purge primary door, a purge inlet pipe nitrogen purge check valve, a purge inlet pipe nitrogen purge secondary door, and a purge inlet pipe nitrogen purge limiting valve in sequence.

[0083] In this embodiment, optionally, the sewage pipe 210 is provided with a primary sewage discharge door at the bottom of the sewage pipe and a secondary sewage discharge door at the bottom of the sewage pipe in sequence.

[0084] In some embodiments, the liquid ammonia storage tank 100 is connected to a liquid ammonia input pipe 300 and a liquid ammonia output pipe 310 to ensure stable input and output of liquid ammonia in the liquid ammonia storage tank 100 .

[0085] In this embodiment, optionally, the liquid ammonia input pipe 300 is connected to a tank truck.

[0086] In this embodiment, optionally, the liquid ammonia output pipe 310 is connected to the inlet of the liquid ammonia evaporator.

[0087] In this embodiment, optionally, the liquid ammonia input pipe 300 is provided with a pneumatic door on the liquid ammonia side of the liquid ammonia input pipe, a primary door on the liquid ammonia side of the liquid ammonia input pipe, a secondary door on the liquid ammonia side of the liquid ammonia input pipe, and a flow limiting valve on the liquid ammonia side of the liquid ammonia input pipe in sequence. When liquid ammonia is input, the pneumatic door on the liquid ammonia side of the liquid ammonia input pipe, the primary door on the liquid ammonia side of the liquid ammonia input pipe, and the secondary door on the liquid ammonia side of the liquid ammonia input pipe are opened in sequence, and the flow limiting valve on the liquid ammonia side of the liquid ammonia input pipe acts as a check valve.

[0088] In this embodiment, optionally, the liquid ammonia output pipe 310 is provided with a liquid ammonia output pipe outlet primary door, a liquid ammonia output pipe outlet pneumatic door, a liquid ammonia output pipe outlet secondary door, and a liquid ammonia output pipe outlet main door in sequence.

[0089] In some embodiments, the liquid ammonia storage tank 100 is connected to a gaseous ammonia output pipe 400 for connecting to the outlet of the liquid ammonia evaporator.

[0090] In this embodiment, optionally, the gas ammonia output pipe 400 is provided with a first manual door of the gas ammonia output pipe, a second manual door of the gas ammonia output pipe, and a shut-off valve of the gas ammonia output pipe in sequence.

[0091] In some embodiments, the liquid ammonia storage tank 100 is connected to a waste ammonia discharge pipe 500 for connecting to an ammonia absorption tank.

[0092] In this embodiment, the exhaust ammonia exhaust pipe 500 optionally includes a first exhaust branch, a second safety branch, and a third safety branch, that is, one of the three branches is for exhaust, and the other two are connected to safety valves.

[0093] In this embodiment, optionally, the second safety branch and the third safety branch are each provided with a safety branch safety valve in sequence, and the safety branch isolates the manual door.

[0094] In some embodiments, the liquid ammonia storage tank 100 is connected to an ammonia unloading pipe 600 for connecting to an ammonia unloading compressor.

[0095] According to the above principle, the present invention can also make appropriate changes and modifications to the above implementation. Therefore, the present invention is not limited to the specific implementation disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention.

Claims

1. A liquid ammonia storage tank maintenance pressure test method, used for testing a liquid ammonia storage tank (100), characterized in that: Steps include; S100. Emptying the liquid ammonia storage tank: emptying the interior of the liquid ammonia storage tank (100); S200. The clean water replacement tank is filled with sufficient clean water into the liquid ammonia storage tank (100). When the clean water is injected into the clean water replacement tank in step S200, the water pressure of the liquid ammonia storage tank (100) is monitored in real time by the pressure sensor of the liquid ammonia storage tank (100); S300. Tank maintenance: performing maintenance work on the liquid ammonia storage tank (100); S400. A water pressure test is performed on the liquid ammonia storage tank (100). After the water pressure test in step S400, if the test fails, the tank body is overhauled in step S300; S500. Airtightness test: liquid nitrogen is gasified and pressurized and injected into the liquid ammonia storage tank (100), and clean water in the liquid ammonia storage tank (100) is discharged to perform an airtightness test to ensure that no air enters the liquid ammonia storage tank (100) after drainage. After the airtightness test in step S500, if the test fails, the tank body is overhauled in step S300; S600. Discharging nitrogen from the tank, reducing and maintaining a predetermined low pressure of nitrogen in the liquid ammonia storage tank (100), and discharging nitrogen from the liquid ammonia storage tank (100). In step S600, the nitrogen pressure in the liquid ammonia storage tank (100) is higher than the external pressure. The liquid ammonia storage tank (100) is connected to a purge input pipe (200) and a sewage discharge pipe (210); The liquid ammonia storage tank (100) is connected to a liquid ammonia input pipe (300) and a liquid ammonia output pipe (310); The liquid ammonia storage tank (100) is connected to a gaseous ammonia output pipe (400) for connecting to the outlet of the liquid ammonia evaporator; The liquid ammonia storage tank (100) is connected to a waste ammonia discharge pipe (500) for connecting to an ammonia absorption tank; The liquid ammonia storage tank (100) is connected to an ammonia unloading pipe (600) for connecting to an ammonia unloading compressor; The specific process of the airtight test in step S500 includes: S510. After the hydraulic test of the liquid ammonia storage tank is completed, drain the water. When the body pressure drops to 0.1 MPa, start injecting nitrogen to perform an airtight test. After the nitrogen is connected, continue to drain the tank until it is empty and close the valve; S520. If there is no abnormality, then gradually increase the pressure by 10% of the specified test pressure until the test pressure is reached, maintain the pressure for 30 minutes, then reduce it to at least 87% of the specified test pressure, maintain the pressure for a sufficient time for inspection. The pressure should remain unchanged during the inspection, and continuous pressurization shall not be used to maintain the test pressure unchanged; S530. It is strictly forbidden to tighten bolts under pressure or apply external force to the pressure components during the airtightness test; S540. Nitrogen replacement is completed, and the system pressure is maintained above 0.1MPa to prepare for ammonia injection.

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