Debugging method suitable for MDEA method natural gas deacidification system of offshore oil and gas field development project

Abstract

The invention provides an MDEA-method natural gas deacidification system debugging method suitable for offshore oil and gas field development engineering, and relates to the technical field of ocean engineering, the MDEA-method natural gas deacidification system debugging method comprises the following steps: before testing, ensuring that an MDEA deacidification unit is constructed and obtaining a corresponding mechanical completion certificate; deionized water is used as a medium to simulate establishment of an MDEA deacidification unit flow; a 1% K2CO3 solution is used for conducting degreasing circulating cleaning on the system; performing deionized water rinsing twice in sequence, and performing a nitrogen bubbling test; mDEA, amine liquid desalted water and a defoaming agent are mixed in proportion and placed in a solution tank; establishing solution cold circulation; sampling and testing the concentration of the solution after the system runs; starting a regeneration tower bottom heater, and establishing a solution heat cycle; feeding raw material gas to a normal working condition, measuring the content of CO2 and H2S in purified gas at the top of the absorption tower after the system is stable, checking whether the content reaches the standard or not, and checking and solving problems in time if the problems are found; and after the test is completed, closing the feed gas inlet valve. By means of the method, it can be guaranteed that the MDEA method offshore natural gas deacidification system can be smoothly put into production and stably run.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ocean engineering, and particularly relates to a debugging method of an MDEA method natural gas deacidification system suitable for offshore oil and gas field development engineering. BACKGROUND

[0002] The acid components in offshore natural gas are mainly H2S and CO2, wherein H2S has strong acidity and is easy to corrode equipment, and CO2 greatly affects the combustibility of natural gas. In addition, if the acid natural gas is directly combusted without treatment, the environment will be seriously polluted, and if it is directly used as an industrial raw material, the catalyst will be poisoned and the catalytic efficiency will be reduced, so it is necessary to realize the application of the natural gas deacidification process on the offshore platform.

[0003] N-methyldiethanolamine (MDEA) can absorb CO2 and H2S under certain conditions, and has the advantages of good regeneration effect, low regeneration temperature, good thermal stability, and no corrosion to carbon steel equipment, and is therefore widely used for offshore natural gas deacidification. The reaction principle is as follows, wherein H2S and MDEA are instantaneous reactions: H2S+H2O+R2CH3N⇌R2CH3NH + +HS - And CO2 and MDEA are slow reactions: CO2+H2O+R2CH3N⇌R2CH3NH + +HCO3 - With the help of amine solution (R ’ 2NH), the reaction rate of CO2 and MDEA can be increased: R ’ 2NH+CO2⇌R ’ 2NCOOH R ’ 2NCOOH+R2CH3N+H2O⇌R ’ 2NH+R2CH3NH + +HCO3 - The reactions of H2S and MDEA and the reactions of CO2 and MDEA are reversible reactions, when the temperature is low and the pressure is high, the reactions proceed from left to right, and MDEA solution absorbs H2S and CO2; when the temperature is high and the pressure is low, the reactions proceed from right to left, and MDEA solution desorbs H2S and CO2 to realize regeneration.

[0004] A typical MDEA method natural gas deacidification process can refer to Figure 2, mainly divided into raw gas deacidification part and MDEA circulation regeneration part. First, the raw gas (containing acid gas H2S, CO2) is pretreated and enters the bottom of the acid gas absorption tower, flows from bottom to top and the lean amine liquid flows from top to bottom in the tower, and the acid gas in the raw gas is removed after the wet purified gas leaves the absorption tower and enters the subsequent treatment process. Secondly, the MDEA circulation regeneration part, the rich MDEA liquid flowing out of the bottom of the absorption tower is separated from the part of hydrocarbons carried by the flash tank, enters the MDEA regeneration tower, flows from top to bottom and flows upward in the tower, and the steam is removed from the rich MDEA liquid, and the acid gas is produced at the top and enters the downstream processing device for recovery. The lean amine liquid flowing out of the bottom of the regeneration tower is supplemented with water and MDEA to maintain the concentration of the solution, then it is lifted by the lean liquid lifting pump and cooled by the lean liquid cooler, and then it is sent to the top of the absorption tower for circulation.

[0005] However, the prior art lacks a specific commissioning method for the MDEA method offshore natural gas deacidification system, and cannot find and clear the problems existing before the MDEA method natural gas deacidification system is put into production, and cannot guarantee that the MDEA method offshore natural gas deacidification system can be smoothly put into production and stable operation. SUMMARY

[0006] The main technical problem to be solved by the present application is that the prior art lacks a specific commissioning method for the MDEA method offshore natural gas deacidification system, and cannot find and clear the problems existing before the MDEA method natural gas deacidification system is put into production, and in order to overcome the above-mentioned defects existing in the prior art, a MDEA method natural gas deacidification system commissioning method suitable for offshore oil and gas field development engineering is provided.

[0007] The technical scheme adopted by the present application to solve its technical problems is: The MDEA method natural gas deacidification system commissioning method suitable for offshore oil and gas field development engineering provided by the present application adopts the following technical scheme: A MDEA method natural gas deacidification system commissioning method suitable for offshore oil and gas field development engineering, comprising the following steps: S1: Ensure that the MDEA deacidification unit has been completed and obtained the corresponding mechanical completion certificate before formal test; S2: Simulate the MDEA deacidification unit process with deionized water as the medium to test the process integrity and continuity, and further clean the equipment and adjust the instruments; S3. Use 1% K2CO3 solution to circulate clean the system; S4: Refer to step S3 to use deionized water to rinse the system for the first time to remove the residual alkali solution; S5: Refer to step S3, the system is rinsed with deionized water for the second time, and the second rinse water of the system is taken at multiple points to test the rinsing effect by nitrogen bubbling test; S6: According to the relevant design parameters, MDEA, amine desalted water and defoaming agent are mixed in proportion and placed in the solution tank; S7: Refer to step S3 to establish solution cold circulation; S8: After the system runs for 2-4 hours, sample at multiple points to test whether the solution concentration meets the standard, and if problems are found, they should be promptly investigated and solved; S9: Open the regeneration tower bottom heater to establish solution heat circulation, and open the coolers and air cooling devices of the system in turn; S10: Gradually put in raw gas from small to large to normal working condition, and after the system stabilizes, measure the CO2 and H2S content in the purified gas at the top of the absorption tower to test whether it meets the standard, and if problems are found, they should be promptly investigated and solved; S11: After the test is completed, gradually close the raw gas inlet valve until it is fully closed, maintain 20% solution circulation, and the debugging is completed.

[0008] Further, the specific steps of establishing the MDEA acid removal unit process with deionized water as the medium in S2 are as follows: S21. Nitrogen is filled into the absorption tower and flash tank to establish normal working pressure; S22. Start the solution pump to inject deionized water into the solution tank and the regeneration tower in turn to the appropriate liquid level; S23. Start the lean liquid lifting pump and lean liquid booster pump in turn, adjust the flow by adjusting the opening of the liquid level control valve and the flow regulating valve, inject deionized water into the absorption tower and the flash tank to the appropriate liquid level, open the valve from the flash tank to the regeneration tower, and establish a water circulation process; S24. After the system runs normally, open the blowdown valves at the bottom of the absorption tower, flash tank and regeneration tower to blow down, and when there is no visible solid matter, stop blowing down and stop supplementing deionized water to the system; S25. Start the absorption tower purifier separator, lean liquid air cooler and regeneration overhead cooler respectively and debug and put into use; S26. Open the regeneration tower bottom heater to heat and clean the system, and every 2 hours, blow down the circulating liquid until no visible solid impurities and clear water are observed, and end the linkage test run; S27. Close the regeneration tower bottom heater, stop adding water to the system, close the lean liquid lifting pump and lean liquid booster pump, and when the water temperature drops to a reasonable range, close the purified gas cooler, lean liquid cooler and regeneration acid gas cooler; S28. Open the blowdown valves of the system to drain the water.

[0009] Further, the specific steps of the system degreasing circulation cleaning in S3 using 1% K2CO3 solution are as follows: S31. Nitrogen is filled into the absorption tower and flash tank to establish normal working pressure; S32. The required mass of K2CO3 is calculated according to the system solution retention, and K2CO3 is prepared according to the calculation result; S33. K2CO3 is dissolved in deionized water in a temporary solution tank and then put into the solution tank, the deionized water pump is started to fill the solution tank with water to the upper limit liquid level, and the solution pump is started to pour the lye into the regeneration tower; S34. The lean liquid booster pump and the lean liquid lifting pump are started in turn, the liquid levels at various points are established in turn, and the liquid level automatic control is timely put into operation, after the stable liquid levels at various points and the normal lye cold circulation, the regeneration tower bottom heater is opened to heat the lye, and when the lye temperature reaches the working temperature at the bottom of the absorption tower, the lean liquid water cooler is opened to control the lye temperature at the inlet of the absorption tower; S35. After the lye temperature in the regeneration tower reaches the working temperature, the lye washing time is calculated, and the lye washing time should be 4-6h; S36. After the lye washing is completed, the regeneration tower heater is stopped first, and then the pump is stopped after the system lye is cooled.

[0010] Further, the method for testing the rinsing effect by nitrogen bubbling in S5 is as follows: 1-3% dilute amine solution is prepared by using a barrel of amine, nitrogen is used for bubbling test, the bubble height should be ≤300ml, and the defoaming time should be ≤20s, if not, a water rinsing is needed.

[0011] Further, between the steps S1 and S2, all the pumps of the MDEA decarbonization unit should be individually tested.

[0012] Further, between the steps S7 and S8, the step S6 of mixing MDEA, amine solution desalting water and defoaming agent in proportion to prepare standby solution in the solution tank should be repeated.

[0013] Based on the above, the beneficial effects of the present application are: 1. The method uses deionized water as a medium to simulate the test working condition, realizes the verification of the process integrity and continuity of the MDEA acid removal device.

[0014] 2. The method is designed carefully and meticulously from water circulation to system lye washing, rinsing and finally to normal test run, so that problems can be found and solved in time.

[0015] 3. The method uses K2CO3 solution to clean the system to prevent grease from affecting the MDEA treatment effect.

[0016] 4. The method creates a good MDEA circulation environment from water washing to alkali washing to rinsing.

[0017] 5. The method uses nitrogen bubbling test to check the rinsing effect.

[0018] 6. The method is well designed, and through continuous adjustment and optimization of process parameters at each link, it can efficiently find and clear problems existing before the commissioning of the MDEA natural gas acid removal system, and can ensure the smooth commissioning and stable operation of the MDEA offshore natural gas acid removal system. BRIEF DESCRIPTION OF DRAWINGS

[0019] The application will be further described below in combination with the drawings and examples.

[0020] Figure 1 The flow chart of the MDEA natural gas acid removal system commissioning method for offshore oil and gas field development engineering of the application; Figure 2 The MDEA natural gas acid removal process flow chart of the application. DETAILED DESCRIPTION

[0021] The application will be further described below in combination with the drawings and examples. The illustrative examples of the application and the description are used to explain the application, but do not limit the application.

[0022] Example: as shown in the method for commissioning the MDEA natural gas acid removal system suitable for offshore oil and gas field development engineering. Figures 1-2

[0023] As shown in the method for commissioning the MDEA natural gas acid removal system suitable for offshore oil and gas field development engineering. Figure 1 and Figure 2 The application discloses a method for commissioning the MDEA natural gas acid removal system suitable for offshore oil and gas field development engineering, comprising the following steps: First step: before formal testing, ensure that the MDEA acid removal unit has been completed and obtained the corresponding mechanical completion certificate, to ensure the system hardware integrity, and provide a reliable material basis for subsequent commissioning work, avoid problems such as the commissioning cannot be normally carried out or hardware failure occurs during the commissioning due to incomplete hardware.

[0024] Second step: carry out single test run on all pumps of the MDEA decarbonization unit, and through the inspection on the independent performance of the pumps, eliminate the hidden troubles of the equipment before the system linkage, and provide a foundation support for the overall stable operation of the MDEA acid removal system.

[0025] Third step: use deionized water as medium to simulate the MDEA acid removal unit process to test the completeness and continuity of the process, and further clean the equipment and adjust the instruments, the specific method can refer to the following steps: ​(1) Fill nitrogen to the absorption tower and flash tank to establish normal working pressure.

[0026] (2) Start the solution pump to inject deionized water into the solution tank and regeneration tower in sequence to the appropriate liquid level to provide medium basis for subsequent circulation process.

[0027] (3) Start the lean liquid lifting pump and lean liquid booster pump, adjust the opening of the liquid level control valve and flow regulating valve to adjust the flow, inject deionized water into the absorption tower and flash tank to the appropriate liquid level, open the valve from the flash tank to the regeneration tower, and establish the water circulation process. (4) After the system runs normally, open the blowdown valves at the bottom of the absorption tower, flash tank and regeneration tower to blow down, and stop blowing down when there is no visible solid matter, and stop supplementing deionized water to the system, so as to avoid impurities blocking the equipment or affecting the subsequent process effect.

[0028] (5) Start the absorption tower purifier separator, lean liquid air cooler, and regeneration top cooler respectively and debug them.

[0029] (6) Start the regeneration tower bottom heater to heat and clean the system, and blow down the circulating liquid every 2 hours until no visible solid impurities and clear water are observed, and then end the linkage test run to ensure the cleanliness of the internal equipment of the system.

[0030] (7) Turn off the regeneration tower bottom heater, stop adding water to the system with the solution pump, turn off the lean liquid lifting pump and lean liquid booster pump, and turn off the purification gas cooler, lean liquid cooler and regeneration acid gas cooler when the water temperature drops to a reasonable range.

[0031] (8) Open the system's blowdown valves to drain the system water to prevent residual water from mixing with the subsequent K2CO3 solution and affecting the degreasing effect.

[0032] Step 4: Use 1% K2CO3 solution to circulate and clean the system to remove oil and grease in the system. The specific method can be referred to the following steps: (1) Fill nitrogen to the absorption tower and flash tank to establish normal working pressure.

[0033] (2) Calculate the required mass of K2CO3 according to the system solution retention amount, and prepare K2CO3 according to the calculation results.

[0034] (3) Dissolve K2CO3 in the temporary solution tank with deionized water, then put it into the solution tank, start the deionized water pump to fill the solution tank to the upper limit liquid level, and start the solution pump to pour the lye into the regeneration tower.

[0035] (4) Start the lean liquid booster pump and the lean liquid lifting pump in sequence, and establish the liquid levels at each point in sequence and timely input the liquid level automatic control. After the liquid levels at each point are stable and the caustic soda cold circulation is normal, open the regenerator bottom heater to heat the caustic soda. When the caustic soda temperature reaches the working temperature of the absorption tower bottom, open the lean liquid water cooler to control the caustic soda temperature at the absorption tower inlet.

[0036] (5) After the caustic soda temperature in the regenerator reaches the working temperature, start to calculate the caustic washing time, which should be 4-6h.

[0037] (6) After the caustic washing is completed, first stop the regenerator heater, and then stop the pump after the system caustic soda is cooled.

[0038] Step 5: Refer to Step 4 to use deionized water to perform the first rinse on the system to remove residual caustic soda.

[0039] Step 6: Refer to Step 4 to use deionized water to perform the second rinse on the system, and take the second rinse water at multiple points in the system. Use barreled amine to configure 1-3% dilute amine solution, and use nitrogen to perform a bubbling test. The bubbling test should meet the requirements of bubble height ≤300ml and defoaming time ≤20s. If the requirements are not met, an additional water rinse is needed. The system cleanliness is detected through the bubbling test to ensure that there is no foam characteristic impurity residue that affects the MDEA solution.

[0040] Step 7: Mix MDEA, amine desalting water and defoaming agent in proportion according to the relevant design parameters and place them in the solution tank.

[0041] Step 8: Refer to Step 4 to establish a solution cold circulation, thereby verifying the continuity of the solution circulation path and preparing for subsequent hot circulation and raw gas inlet.

[0042] Step 9: Repeat Step 7 to mix MDEA, amine desalting water and defoaming agent in proportion to configure standby solution in the solution tank, thereby ensuring that the system can supplement qualified solution at any time and reducing the risk of shutdown.

[0043] Step 10: After the system runs for 2-4 hours, sample at multiple points to check whether the solution concentration meets the requirements. If problems are found, they should be timely investigated and solved.

[0044] Step 11: Open the regenerator bottom heater to establish a solution hot circulation, and open the coolers and air coolers of the process in sequence.

[0045] Step 12: Gradually put in raw gas from small to large to normal working conditions. After the system is stable, measure the CO2 and H2S contents in the purified gas at the top of the absorption tower, thereby ensuring that the purified gas indicators meet the requirements and that problems such as insufficient absorption tower efficiency can be timely investigated.

[0046] Thirteenth step: after the test is completed, gradually close the raw material gas inlet valve until it is fully closed, and maintain a 20% solution circulation, and the debugging is completed, wherein, by maintaining a 20% solution circulation, low-cost continuous circulation can be realized, and the effects of equipment protection and rapid start-up are realized.

[0047] The method uses deionized water as a medium to simulate the test working condition in a way of building the test, realizes verification of the MDEA deacidification device process integrity and continuity; from water circulation to system alkali washing, to rinsing and finally to normal test run, the design is rigorous and careful, problems can be found and solved in time; K2CO3 solution is used for degreasing circulation cleaning of the system to prevent oil from affecting the MDEA treatment effect; from water washing to alkali washing to rinsing, a good MDEA circulation environment is created; nitrogen is used for bubbling test to test the rinsing effect; the method is designed comprehensively, through continuous adjustment and optimization of process parameters of each link, high-quality guarantee is provided for the system commissioning and stable operation.

[0048] The method can efficiently find and clear the problems existing before the MDEA method natural gas deacidification system is put into production, and can guarantee that the MDEA method offshore natural gas deacidification system can be smoothly put into production and stably run.

[0049] The above is only a preferred embodiment of the present application, and does not limit the present application in any form, and any simple modification, equivalent change and modification made according to the technical essence of the present application to the above embodiment still belongs to the scope of the technical solution of the present application.

Claims

1. A commissioning method for a natural gas deacidification system using the MDEA method in offshore oil and gas field development projects, characterized in that, Includes the following steps: S1: Ensure that the MDEA deacidification unit has been built and the corresponding mechanical completion certificate has been obtained before the formal test; S2: The process of MDEA deacidification unit is established by simulating the process using deionized water as a medium to verify the integrity and continuity of the process, and at the same time, the equipment can be cleaned and the instruments calibrated. S3. Use a 1% K2CO3 solution to degrease and circulate the system for cleaning; S4: Refer to step S3 and rinse the system with deionized water for the first time to remove alkaline residue; S5: Refer to step S3 and rinse the system a second time with deionized water. Take the second rinse water from multiple points and test the rinsing effect with a nitrogen bubbling test. S6: Mix MDEA, amine desalinated water and defoamer according to the relevant design parameters and place them in a solution tank; S7: Establish a solution cooling cycle as per step S3; S8: After the system has been running for 2-4 hours, take multiple samples to check whether the solution concentration meets the standard. If any problems are found, they should be investigated and resolved in a timely manner. S9: Turn on the bottom heater of the regeneration tower to establish a solution thermal cycle, and then turn on each cooler and air cooling device of the system in sequence. S10: Gradually introduce raw gas from small to large until the system is in normal working condition. After the system is stable, measure the CO2 and H2S content in the purified gas at the top of the absorption tower to check whether it meets the standard. If any problems are found, they should be investigated and resolved in time. S11: After the test is completed, gradually close the raw material gas inlet valve until it is completely closed, maintain 20% solution circulation, and the debugging is complete.

2. The commissioning method for a natural gas deacidification system using the MDEA method in offshore oil and gas field development engineering, as described in claim 1, is characterized in that... The specific steps for establishing the MDEA deacidification unit process in S2 using deionized water as the medium are as follows: S21. Pour nitrogen into the absorption tower and flash tank to establish normal operating pressure; S22. Start the solution pump and sequentially inject deionized water into the solution tank and regeneration tower until the appropriate liquid level is reached; S23. Start the lean liquid booster pump and lean liquid pressure pump in sequence, adjust the flow rate by adjusting the opening of the liquid level control valve and the flow rate control valve, inject deionized water into the absorption tower and flash tank to the appropriate liquid level, open the valve from the flash tank to the regeneration tower, and establish a water circulation process. S24. After the system is running normally, open the drain valves at the bottom of the absorption tower, flash tank and regeneration tower to drain the sewage. When there is no visible solid matter, stop draining the sewage and stop adding deionized water to the system. S25. Start the absorber separator, lean liquid air cooler and regeneration top cooler of the absorption tower respectively and put them into operation; S26. Turn on the bottom heater of the regeneration tower to heat and clean the system. Drain the circulating liquid every 2 hours until the sample is clear and no visible solid impurities are observed. End the joint test run. S27. Turn off the bottom heater of the regeneration tower, turn off the solution pump to stop adding water to the system, turn off the lean liquid lift pump and lean liquid booster pump, and wait for the water temperature to drop to a reasonable range before turning off the purified gas cooler, lean liquid cooler and regenerated acid gas cooler. S28. Open all drain valves in the system to drain all the water.

3. The commissioning method for a natural gas deacidification system using the MDEA method in offshore oil and gas field development projects according to claim 1, characterized in that, The specific steps for degreasing and circulating cleaning the system using a 1% K2CO3 solution in S3 are as follows: S31. Charge nitrogen into the absorption tower and flash tank to establish normal operating pressure; S32. Calculate the required mass of K2CO3 based on the system solution content, and prepare K2CO3 based on the calculation results; S33. Dissolve K2CO3 in deionized water in a temporary solution tank and then put it into a solution tank. Start the deionized water pump to fill the solution tank to the upper limit level. Start the solution pump to pump the alkaline solution into the regeneration tower. S34. Start the lean liquid booster pump and lean liquid lift pump in sequence, establish the liquid level at each point in sequence, and put the liquid level automatic control into place in time. After the liquid level at each point is stable and the alkali cold circulation is normal, turn on the regeneration tower bottom heater to heat the alkali. When the alkali temperature reaches the working temperature at the bottom of the absorption tower, turn on the lean liquid water cooler to control the alkali temperature at the inlet of the absorption tower. S35. Once the temperature of the alkali solution in the regeneration tower reaches the operating temperature, start calculating the alkali washing time, which should be 4-6 hours. S36. After the alkaline washing is completed, first stop the heater of the regeneration tower, and after the alkaline solution in the system cools down, stop the pump and drain the alkaline solution from the system.

4. The commissioning method for a natural gas deacidification system using the MDEA method in offshore oil and gas field development projects according to claim 1, characterized in that, The method for verifying the rinsing effect using nitrogen bubbling test in S5 is as follows: Prepare a 1-3% dilute amine solution using barrel-packaged amine. Conduct a bubbling test using nitrogen gas. The bubbling test should meet the following requirements: bubble height ≤ 300ml and defoaming time ≤ 20s. If the requirements are not met, a water rinse is required.

5. The commissioning method for a natural gas deacidification system using the MDEA method in offshore oil and gas field development projects according to claim 1, characterized in that, Between steps S1 and S2, all pumps and motors in the MDEA decarbonization unit should also undergo individual commissioning.

6. The commissioning method for a natural gas deacidification system using the MDEA method in offshore oil and gas field development engineering, as described in claim 1, is characterized in that... Between steps S7 and S8, step S6 should be repeated to mix MDEA, amine desalinated water and defoamer in proportion to prepare a standby solution for placement in a solution tank.

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