Liquefied gas desulfurization system

Abstract

The utility model discloses a liquefied gas desulfurization system and belongs to the technical field of liquefied gas. According to the technical scheme, the liquefied gas desulfurization system comprises a liquefied gas buffer tank, a pre-alkali washing settling tank, a first-stage extraction settling tank, a second-stage extraction settling tank, a water washing settling tank, a liquefied gas sand filter tower and a controller which are sequentially connected through pipelines; the pre-alkali washing settling tank, the first-stage extraction settling tank and the second-stage extraction settling tank are respectively provided with an interface level meter, and the interface level meters are electrically connected with the controller; the liquefied gas buffer tank is connected with a raw material heat exchanger and an amine liquid flash tank pipeline, a pre-alkali-washing venturi tube and a pre-alkali-washing mixer are arranged on a pipeline between the liquefied gas buffer tank and the pre-alkali-washing settling tank, and the pre-alkali-washing settling tank is communicated with the pre-alkali-washing venturi tube. The device can well solve the problem of pressure relief in summer and the problem of crystallization of an extraction agent in winter.

Description

Technical Field

[0001] This utility model belongs to the field of liquefied gas technology, specifically relating to a liquefied gas desulfurization system. Background Technology

[0002] In the petrochemical industry, liquefied petroleum gas (LPG) produced by catalytic cracking units is generally subjected to preliminary desulfurization with ethanolamine. Under normal circumstances, the sulfides in the LPG after amine removal are mainly mercaptan sulfur, and also contain a small amount of hydrogen sulfide and trace amounts of carbonyl sulfur and dimethyl sulfide. The content of dimethyl sulfide is about 1 to 2% of the total sulfur content in the LPG.

[0003] After amine removal, the product enters the liquefied petroleum gas (LPG) dethiol system. This system operates on the principle of the weak acidity of thiols and the ease with which thiols are oxidized to disulfide compounds. The reaction equation is as follows:

[0004] RSH + NaOH → RSNa + H2O (Removal of mercaptan sulfur from oil products)

[0005] 2RSNa + 1 / 2O2 + H2O → RSSR + 2NaOH (Desulfurization of thioglycolate anions from alkali)

[0006] First, the strong alkali (NaOH) in the extractant reacts with the thiol to produce sodium thiolate. The sodium thiolate dissolves in the extractant and is removed from the liquefied gas. The extractant containing sodium thiolate is then oxidized to disulfide by oxygen under the action of a catalyst, and the extractant is regenerated. The regenerated extractant can be recycled, which can avoid the generation of a large amount of alkali residue.

[0007] The liquefied petroleum gas (LPG) first enters the pre-alkali washing settling tank to remove hydrogen sulfide and entrained amine-rich liquid. Then, it enters the extraction unit for mercaptan removal. These processes cause a decrease in the alkali concentration in the alkali solution and extraction agent system, and an increase in the amount of carbonates, sulfates, and anions carried or generated within the system. In severe cases, saturation precipitation and deposition within the system can lead to the phenomenon of "impurities and salts accumulating" at the remote pressure points of the pre-alkali washing settling tank and extraction settling tank. Therefore, when the temperature changes and decreases, it easily leads to a "distortion" phenomenon where the "remote pressure transmission" continuously rises with increasing temperature. Simultaneously, because the pre-alkali washing alkali solution contains a large amount of sulfides and has a strong pungent odor, it poses a health hazard to workers and causes a certain degree of environmental pollution.

[0008] During the high-temperature season in summer, due to the long-distance transmission of external liquefied gas to the unit and the uncertainty of its composition, the temperature of the gas entering the unit can rise to 50-55℃, causing the pressure in the raw material buffer tank to rise continuously. Part of the C3 component in the liquefied gas is vaporized, and the original C2 light component depressurization process of the unit can not meet the requirements. It is necessary to depressurize by opening the safety valve branch valve to prevent the raw material buffer tank from overpressure.

[0009] The temperature of the liquefied gas entering the existing desulfurization system needs to be adjusted to reduce on-site liquid level verification work, ensure the stable operation of the pre-alkali washing settling tank, and ensure the safety of the operators. Utility Model Content

[0010] This invention provides a liquefied petroleum gas desulfurization system that can effectively solve the problems of pressure relief in summer and crystallization of extractants in winter.

[0011] The technical solution of this utility model is as follows:

[0012] The liquefied petroleum gas (LPG) desulfurization system includes an LPG buffer tank, a pre-alkali washing settling tank, a primary extraction settling tank, a secondary extraction settling tank, a water washing settling tank, an LPG sand filter tower, and a controller, all connected in sequence via pipelines. The pre-alkali washing settling tank, the primary extraction settling tank, and the secondary extraction settling tank are all equipped with interface gauges, which are electrically connected to the controller.

[0013] The liquefied petroleum gas (LPG) buffer tank is connected to a raw material heat exchanger and a pipeline from the amine liquid to the flash tank. A pre-alkali washing venturi tube and a pre-alkali washing mixer are installed on the pipeline between the LPG buffer tank and the pre-alkali washing settling tank. The pre-alkali washing settling tank and the pre-alkali washing venturi tube are connected. The shell side of the raw material heat exchanger is equipped with an LPG inlet pipeline and an LPG outlet pipeline. The LPG outlet pipeline is connected to the LPG buffer tank. The tube side of the raw material heat exchanger is equipped with a circulating water inlet pipeline, a circulating water outlet pipeline, a hot medium water inlet pipeline, and a hot medium water outlet pipeline. Temperature control valves are installed on the circulating water outlet pipeline and the hot medium water outlet pipeline. A remote temperature sensor is installed on the LPG outlet pipeline. Both the remote temperature sensor and the temperature control valve are electrically connected to the controller.

[0014] The pre-alkali washing settling tank is equipped with a new alkali solution feed line from the filter and an alkali residue discharge line to the alkali residue tank. The primary extraction settling tank and the secondary extraction settling tank are both connected to the alkali residue discharge line to the alkali residue tank via pipelines.

[0015] A primary extraction mixer is installed on the pipeline between the pre-alkali washing settling tank and the primary extraction settling tank; a secondary extraction mixer is installed on the pipeline between the primary extraction settling tank and the secondary extraction settling tank, and the primary extraction mixer and the secondary extraction mixer are connected by pipeline.

[0016] The primary extraction settling tank is equipped with a rich extractant deoxidation and regeneration tower pipeline. The primary extraction settling tank is connected to an alkali heater via a pipeline. The alkali heater tube side is equipped with a hot water inlet pipeline and a hot water return pipeline. Both the primary extraction mixer and the secondary extraction mixer are equipped with feed pipelines from the FI-901A / B lean extractant.

[0017] A water washing venturi tube is installed on the pipeline between the secondary extraction settling tank and the water washing settling tank; an alkaline wastewater outlet pipeline is installed at the bottom of the water washing settling tank and the liquefied gas sand filter tower; the water washing venturi tube is also connected to the demineralized water inlet pipeline from the system.

[0018] The LPG sand filter tower is connected to a refined LPG discharge pipeline.

[0019] It also includes an oxidation regeneration tower, a three-phase separation tank, a tail gas settling tank, and an emergency venting tank, which are connected in sequence by pipelines.

[0020] The lower part of the oxidation regeneration tower is connected to a rich extractant feed pipeline, an oxygen feed pipeline, and a self-stabilized gasoline back-extracting oil feed pipeline. The rich extractant feed pipeline is equipped with a regeneration mixer, which is connected to a three-phase separator tank via a pipeline. The tail gas outlet pipeline at the top of the three-phase separator tank is connected to a tail gas settling tank, which is connected to an emergency vent tank. The bottom of the three-phase separator tank is equipped with a regeneration lean extractant circulation pipeline, which is connected to the oxidation regeneration tower.

[0021] The bottom of the oxidation regeneration tower is equipped with a fresh alkali solution discharge pipeline, which is connected to the fresh alkali solution inlet pipeline from the filter and enters the pre-alkali washing settling tank for recycling; both the oxidation regeneration tower and the three-phase separation tank are connected to the system demineralized water inlet pipeline, the alkali solution or extractant inlet pipeline from the self-preparation tank, and the lean solution to the MI-903A / B discharge pipeline.

[0022] The rich extractant feed line is connected to the three-phase separator via a pipeline; the rich extractant feed line is also connected to the back-extraction oil to heavy feedstock line for reprocessing, the new alkali solution feed line from the filter and the fresh alkali solution discharge line are connected, the demineralized water inlet line from the system and the demineralized water feed line from the system are connected; the lean liquor to MI-903A / B discharge line is provided with two branch lines, one connected to the lean extractant feed line from FI-901A / B and the other connected to the pre-alkali washing mixer, the rich extractant to oxidation regeneration tower line and the rich extractant feed line are connected.

[0023] Preferably, an LPG feed pump is installed on the pipeline between the LPG buffer tank and the pre-alkali washing settling tank.

[0024] A semi-lean agent pump is installed in the pipeline between the preferred primary extraction mixer and the secondary extraction settling tank.

[0025] Preferably, a water washing pump is installed on the demineralized water inlet pipe of the system.

[0026] Preferably, a lean solvent pump is installed on the regenerated lean extractant circulation pipeline.

[0027] Preferably, the circulating water inlet pipe is equipped with control valve one and control valve two, and the circulating water outlet pipe is equipped with control valve three and control valve four; the hot medium water inlet pipe is equipped with control valve five and control valve six, and the hot medium water outlet pipe is equipped with control valve seven and control valve eight. The circulating water inlet pipe and the circulating water outlet pipe are connected by a pipeline, and the connected pipeline is equipped with control valve nine. The hot medium water inlet pipe and the hot medium water outlet pipe are also connected by a pipeline.

[0028] The interface position transmission of the pre-alkali washing tank, primary extraction settling tank, and secondary extraction settling tank in the LPG desulfurization system uses interface level gauges. These gauges have a gas phase (negative pressure P) function. A ) and liquid phase (positive pressure P) B There are two pressure taps. The pressure at the negative pressure tap is the gas phase pressure inside the equipment; the pressure at the positive pressure tap is affected by both the gas phase pressure and the hydrostatic pressure of the liquid column. The difference between the negative pressure and the hydraulic pressure is the hydrostatic pressure generated by the liquid column. When one end of the interface gauge is connected to the liquid phase and the other end to the gas phase, according to the principles of fluid statics, we have:

[0029] P B =P A +Hpg

[0030] Where: H -- liquid height; p -- density of the measured medium; g -- gravitational acceleration at the local area of ​​the measurement.

[0031] From the formula, we can obtain: ΔP=P B -P A =Hpg; Under normal circumstances, the density and gravity of the measured medium

[0032] Since the accelerations are known, the differential pressure measured by the level gauge is proportional to the liquid height H, thus transforming the problem of measuring the liquid height into the problem of measuring the differential pressure.

[0033] Compared with the prior art, this utility model has the following advantages:

[0034] 1. The present invention relates to a raw material heat exchanger and its piping, which, by adjusting the medium and flow rate in the tube side of the heat exchanger, can reasonably control the temperature of the liquefied gas entering the system, thus solving the problem of frequent interface failure and fluctuation. Temperature adjustment is simple and easy to implement.

[0035] 2. It eliminates the risk of alkali burns that may occur when on-site personnel perform glass plate calibration, improves the working environment, protects the health of workers, protects the environment, and reduces fluctuations in the equipment caused by system salt buildup.

[0036] 3. This utility model reduces the amount of alkali replacement and lowers the cost of hazardous waste disposal of waste alkali.

[0037] 4. This utility model not only ensures stable temperature of LPG entering the device in winter, significantly reduces the probability of crystallization caused by high salt content in the alkali system, and eliminates abnormalities such as inaccurate interface display, but also significantly reduces the amount of alkali consumed and waste alkali generated by the device due to interface fluctuations. In the high-temperature season of summer, it can also maintain a lower temperature of LPG, ensuring that the existing depressurization process into the oil-gas separator can maintain the pressure of the LPG buffer tank and prevent depressurization into the flare from causing burn-out and waste. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the structure of this utility model. Figure 1 .

[0039] Figure 2 This is a schematic diagram of the structure of this utility model. Figure 2 .

[0040] Figure 3 This is a schematic diagram of the raw material heat exchanger and its pipeline of this utility model.

[0041] In the diagram, 1. LPG buffer tank; 2. Pre-alkali washing settling tank; 3. Primary extraction settling tank; 4. Secondary extraction settling tank; 5. Water washing settling tank; 6. LPG sand filter tower; 7. Raw material heat exchanger; 8. Amine solution to flash tank pipeline; 9. LPG feed pump; 10. Pre-alkali washing venturi tube; 11. Pre-alkali washing mixer; 12. LPG feed pipeline; 13. LPG discharge pipeline; 14. Circulating water inlet pipeline; 15. Circulating water outlet pipeline; 16. Heat transfer medium water. 17. Inlet water pipeline; 18. Outlet water pipeline for hot medium; 19. Inlet pipeline for new alkali solution from the filter; 20. Pipeline for alkali residue to alkali residue tank; 21. Primary extraction mixer; 22. Secondary extraction mixer; 23. Semi-lean extractant pump; 24. Pipeline for rich extractant to oxidation regeneration tower; 25. Alkali solution heater; 26. Hot water inlet pipeline; 27. Hot water return pipeline; 28. Inlet pipeline for FI-901A / B lean extractant; 29. ​​Water washing Venturi tube; 20. Alkali-containing... 30. Wastewater effluent pipeline; 31. Demineralized water inlet pipeline; 32. Washing water injection pump; 33. Refined liquefied gas outlet pipeline; 34. Oxidation regeneration tower; 35. Three-phase separator; 36. Tail gas settling tank; 37. Emergency venting tank; 38. Rich extractant feed pipeline; 39. Oxygen feed pipeline; 40. Self-stabilized gasoline back-extraction oil feed pipeline; 41. Regeneration mixer; 42. Tail gas outlet pipeline; 43. Regeneration lean extractant circulation pipeline; 44. Lean solvent... 44. Fresh alkali solution discharge pipeline; 45. Demineralized water feed pipeline from the system; 46. Alkali solution or extractant feed pipeline from the self-prepared agent tank; 47. Lean solution to MI-903A / B discharge pipeline; 48. Back-extraction oil to heavy feed pipeline; 49. Control valve one; 50. Control valve two; 51. Control valve three; 52. Control valve four; 53. Control valve five; 54. Control valve six; 55. Control valve seven; 56. Control valve eight; 57. Control valve nine. Detailed Implementation

[0042] To enable those skilled in the art to better understand the technical solutions of this utility model, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this utility model.

[0043] Example 1

[0044] like Figure 1-3 As shown, this embodiment provides a liquefied petroleum gas (LPG) desulfurization system, including an LPG buffer tank 1, a pre-alkali washing settling tank 2, a primary extraction settling tank 3, a secondary extraction settling tank 4, a water washing settling tank 5, an LPG sand filter tower 6, and a controller, all connected in sequence via pipelines. Each of the pre-alkali washing settling tank 2, the primary extraction settling tank 3, and the secondary extraction settling tank 4 is equipped with a boundary gauge, which is electrically connected to the controller. The boundary gauge is manufactured by Rosemount Corporation, model number 3051DP2A22A1BS2M5B4I1D4HR5.

[0045] The liquefied petroleum gas (LPG) buffer tank 1 is connected to the raw material heat exchanger 7 and the amine liquid to flash tank pipeline 8. An LPG feed pump 9, a pre-alkali washing venturi tube 10, and a pre-alkali washing mixer 11 are installed on the pipeline between the LPG buffer tank 1 and the pre-alkali washing venturi tube 10. The pre-alkali washing venturi tube 10 is connected to the pre-alkali washing venturi tube 2. The shell side of the raw material heat exchanger 7 is equipped with an LPG feed pipeline 12 and an LPG discharge pipeline 13, which is connected to the LPG buffer tank 1. The tube side of the raw material heat exchanger 7 is equipped with a circulating water inlet pipeline 14, a circulating water outlet pipeline 15, a hot medium water inlet pipeline 16, and a hot medium water outlet pipeline 17. The circulating water outlet pipeline 15 and the hot medium water outlet pipeline 17 are equipped with… The liquefied gas outlet pipeline 13, equipped with a temperature control valve, is equipped with a remote temperature sensor. Both the remote temperature sensor and the temperature control valve are electrically connected to the controller. The circulating water inlet pipeline 14 is equipped with control valve 1 49 and control valve 2 50. The circulating water outlet pipeline is equipped with control valve 3 51 and control valve 4 52. The hot medium water inlet pipeline 16 is equipped with control valve 53 and control valve 6 54. The hot medium water outlet pipeline 17 is equipped with control valve 7 55 and control valve 8 56. The circulating water inlet pipeline 14 and the circulating water outlet pipeline 15 are connected by a pipeline, and the connected pipeline is equipped with control valve 9 57. The hot medium water inlet pipeline 16 and the hot medium water outlet pipeline 17 are connected by a pipeline.

[0046] The pre-alkali washing settling tank 2 is equipped with a new alkali solution feed line 18 from the filter and an alkali residue to alkali residue tank line 19. The primary extraction settling tank 3 and the secondary extraction settling tank 4 are both connected to the alkali residue to alkali residue tank line 19 through pipelines.

[0047] A primary extraction mixer 20 is installed on the pipeline between the pre-alkali washing settling tank 2 and the primary extraction settling tank 3; a secondary extraction mixer 21 is installed on the pipeline between the primary extraction settling tank 3 and the secondary extraction settling tank 4; the primary extraction mixer 20 and the secondary extraction mixer 21 are connected by a pipeline; a semi-lean agent pump 22 is installed on the pipeline between the primary extraction mixer 20 and the secondary extraction settling tank 4.

[0048] The primary extraction settling tank 3 is equipped with a rich extractant deoxidation regeneration tower pipeline 23. The primary extraction settling tank 3 is connected to an alkali heater 24 through a pipeline. The alkali heater 24 is equipped with a hot water inlet pipeline 25 and a hot water return pipeline 26 in its tube side, and the hot water is returned to the original system after circulating heat extraction. The primary extraction mixer 20 and the secondary extraction mixer 21 are both equipped with a lean extractant feed pipeline 27 from FI-901A / B.

[0049] A water washing venturi tube 28 is installed on the pipeline between the secondary extraction settling tank 4 and the water washing settling tank 5; an alkaline wastewater outlet pipeline 29 is installed at the bottom of the water washing settling tank 5 and the liquefied gas sand filter tower 6; the water washing venturi tube 28 is also connected to the demineralized water inlet pipeline 30 from the system, and a water washing injection pump 31 is installed on the demineralized water inlet pipeline 30 from the system.

[0050] The liquefied gas sand filter tower 6 is connected to a refined liquefied gas outlet pipeline 32;

[0051] It also includes an oxidation regeneration tower 33, a three-phase separation tank 34, a tail gas settling tank 35 and an emergency venting tank 36, which are connected in sequence by pipelines.

[0052] The lower part of the oxidation regeneration tower 33 is connected to a rich extractant feed line 37, an oxygen feed line 38, and a self-stabilized gasoline back-extracting oil feed line 39. The rich extractant feed line 37 is equipped with a regeneration mixer 40, which is connected to a three-phase separator 34 via a pipeline. The tail gas outlet line 41 at the top of the three-phase separator 34 is connected to a tail gas settling tank 35. The tail gas settling tank 35 is connected to an emergency venting tank 36. The bottom of the three-phase separator 34 is equipped with a regeneration lean extractant circulation line 42, which is connected to the oxidation regeneration tower 33. A lean solvent pump 43 is installed on the regeneration lean extractant circulation line 42.

[0053] The bottom of the oxidation regeneration tower 33 is equipped with a fresh alkali solution discharge pipeline 44, which is connected to the fresh alkali solution inlet pipeline 18 from the filter and enters the pre-alkali washing settling tank 2 for recycling; both the oxidation regeneration tower 33 and the three-phase separation tank 34 are connected to the system demineralized water inlet pipeline 45, the alkali solution or extractant inlet pipeline 46 from the self-preparation tank, and the lean solution to MI-903A / B discharge pipeline 47.

[0054] The rich extractant feed line 37 is connected to the three-phase separator 34 via a pipeline; the rich extractant feed line 37 is also connected to the reverse extraction oil to heavy feed line 48; the new alkali solution feed line 18 from the filter and the fresh alkali solution discharge line 44 are connected, the demineralized water inlet line 30 from the system and the demineralized water feed line 45 from the system are connected; the lean solution to MI-903A / B discharge line 47 is provided with two branch lines, one of which is connected to the lean extractant feed line 27 from FI-901A / B, and the other is connected to the pre-alkali washing mixer 11; the rich extractant to oxidation regeneration tower line 23 is connected to the rich extractant feed line 37.

[0055] Work process:

[0056] The liquefied petroleum gas (LPG) supplied by the pump, after being heated by the raw material heat exchanger 7, is mixed with the alkaline solution from the bottom of the pre-alkali washing settling tank in the pre-alkali washing venturi tube 10. After thorough contact and reaction in the pre-alkali washing mixer 11, the mixture enters the pre-alkali washing settling tank 2 for sedimentation and separation, where hydrogen sulfide is removed. The pre-alkali washed LPG is then expelled from the top of the pre-alkali washing settling tank 2 to the primary extraction mixer 20. The interface of the pre-alkali washing settling tank 2 is controlled to prevent the LPG from carrying alkali after pre-alkali washing. A sampling port is provided for the pre-alkali washing alkaline solution, and the alkali concentration is analyzed periodically to determine if alkali replacement is necessary. The regenerated lean extractant is first injected before the secondary extraction mixer 21, and then pumped out from the bottom of the secondary extraction settling tank 4 by the semi-lean extractant pump 22 and returned to the primary extraction mixer 20.

[0057] The qualified liquefied petroleum gas (LPG) after pre-alkali washing flows out from the top of the pre-alkali washing settling tank 2 and is fully mixed and reacted with the semi-lean extractant from the semi-lean extractant pump 22 in the first-stage extraction mixer 20, and then enters the first-stage extraction settling tank 3 for sedimentation and separation. The LPG flows out from the top of the first-stage extraction settling tank 3 and is mixed with the lean extractant from the lean solvent pump 43 in the second-stage extraction mixer 21 for second-stage extraction and desulfurization reaction, and then enters the second-stage extraction settling tank 4 for sedimentation and separation.

[0058] The sodium thiolate-rich extractant is pressed out from the bottom of the primary extraction settling tank 3 and then sent to the oxidation regeneration tower 33 via boundary control.

[0059] A sampling port is installed on the refined liquefied gas outlet pipeline 32 to sample and analyze the desulfurization and total sulfur effects, which serve as the basis for adjusting the extraction operation.

[0060] After mercaptan removal, the liquefied petroleum gas (LPG) is pressurized from the top of the secondary extraction settling tank 4 and mixed with circulating water from the bottom of the washing settling tank 5. This mixture is then passed through a water washing venturi tube 28 to wash away any alkaline substances entrained in the LPG before entering the water washing settling tank 5 for further sedimentation and separation. The LPG flows out from the top of the tank and passes through an LPG sand filter tower 6 to remove any entrained moisture before exiting the system. The washing water is circulated from the bottom of the tank via the water washing venturi tube, and its alkalinity (pH value) is controlled. The washing water is replaced periodically.

[0061] The back-extraction oil from the system, along with the rich solvent from the primary extraction settling tank, oxygen from the oxygen-enriched unit, and the circulating solvent, is premixed in regeneration mixer 40 and then enters the lower part of oxidation regeneration tower 33 for regeneration reaction via the packed section. The sodium thiolate dissolved in the extractant is oxidized to disulfide and dissolved in the back-extraction oil. The extractant and back-extraction oil flow from the top of the tower into three-phase separator 34 for separation. The tail gas from the top of three-phase separator 34 is discharged to the incinerator via a pressure control device. The regenerated lean extractant is recycled from the bottom of three-phase separator 34 via liquefied gas feed pump 9.

[0062] The back-extracted oil passes through the lower baffle inside the three-phase separator 34 and is drawn from the bottom of the tank by the back-extracted oil circulation pump. A portion is recycled to the regeneration mixer 40 by flow control, and the remainder is discharged from the back-extracted oil level control device to be used as raw material.

[0063] By adding a raw material heat exchanger 7 and flexibly adjusting the tube-side medium and flow rate, the temperature of the shell-side liquefied gas in the heat exchanger can be stably controlled. During high-temperature seasons, the circulating water medium in the tube-side is used in a green flow to open control valves 1 (49), 2 (50), 3 (51), and 4 (52), while control valves 6 (54) and 7 (55) are closed to prevent cross-contamination. This low-temperature medium exchanges heat with the shell-side liquefied gas. The outlet temperature of the raw material heat exchanger 7 is generally set at 35-38℃. The temperature control valve at the outlet of the raw material heat exchanger 7 is set to automatic. When the liquefied gas temperature is high, the valve automatically increases its opening to increase the flow of circulating water, achieving cooling until the heat exchanger outlet temperature reaches the set temperature. When the temperature is too low, the valve automatically closes, achieving regulation while reducing circulating water consumption. During the low-temperature season, the tube-side medium of raw material heat exchanger 7 is changed to hot water in the red flow. The circulating water flow is overloaded with the auxiliary line, and control valves 1-49, 2-50, 3-51, and 4-52 are closed. Control valve 9-57 is opened 2-3 notches to prevent freezing. Hot water, as a high-temperature heat source, is used to open control valves 5-53, 6-54, 7-55, and 8-56. The outlet temperature of the raw material heat exchanger is generally set at 30-35℃. The temperature control valve at the outlet of raw material heat exchanger 7 is set to automatic. When the liquefied gas temperature is low, the valve automatically adjusts and increases its opening to increase the flow of hot water, achieving the purpose of heating until the temperature control valve reaches the set temperature. When the temperature is too high, the valve automatically closes, achieving the purpose of regulation while reducing the consumption of hot water.

[0064] Following the above procedures not only ensures that the temperature of the LPG entering the unit remains stable at 35℃ during winter, significantly reducing the probability of crystallization caused by high salt content in the alkali system and eliminating abnormalities such as inaccurate interface display, but also greatly reduces the amount of alkali consumed and waste alkali generated due to interface fluctuations. In the high-temperature summer season, it can also maintain the LPG temperature below 40℃, ensuring that the existing depressurization process for oil-gas separator recovery can maintain the pressure of LPG buffer tank 1, preventing depressurization into the flare and resulting in burn-out and waste.

Claims

1. A liquefied gas desulfurization system, characterized by, The application relates to a liquefied gas production system, which comprises a liquefied gas buffer tank (1), a pre-alkali washing settling tank (2), a first-stage extraction settling tank (3), a second-stage extraction settling tank (4), a water washing settling tank (5), a liquefied gas sand filter tower (6) and a controller which are sequentially connected through pipelines; the pre-alkali washing settling tank (2), the first-stage extraction settling tank (3) and the second-stage extraction settling tank (4) are all provided with interface level meters which are electrically connected with the controller; The liquefied gas buffer tank (1) is connected with a raw material heat exchanger (7) and an amine liquid flash tank pipeline (8), a pre-alkali washing Venturi tube (10) and a pre-alkali washing mixer (11) are arranged on the pipeline between the liquefied gas buffer tank (1) and the pre-alkali washing settling tank (2), and the pre-alkali washing settling tank (2) is communicated with the pre-alkali washing Venturi tube (10); the shell side of the raw material heat exchanger (7) is provided with a liquefied gas feeding pipeline (12) and a liquefied gas discharging pipeline (13), the liquefied gas discharging pipeline (13) is communicated with the liquefied gas buffer tank (1), the tube side of the raw material heat exchanger (7) is provided with a circulating water inlet pipeline (14), a circulating water outlet pipeline (15), a heat medium water inlet pipeline (16) and a heat medium water outlet pipeline (17); temperature control regulating valves are arranged on the circulating water outlet pipeline (15) and the heat medium water outlet pipeline (17), and a temperature remote transmission sensor is arranged on the liquefied gas discharging pipeline (13); the temperature remote transmission sensor and the temperature control regulating valves are electrically connected with the controller; The pre-alkali washing settling tank (2) is provided with a new alkali liquid feeding pipeline (18) from a filter and an alkali residue alkali residue tank pipeline (19), the first-stage extraction settling tank (3) and the second-stage extraction settling tank (4) are communicated with the alkali residue alkali residue tank pipeline (19) through pipelines; A first-stage extraction mixer (20) is arranged on the pipeline between the pre-alkali washing settling tank (2) and the first-stage extraction settling tank (3); a second-stage extraction mixer (21) is arranged on the pipeline between the first-stage extraction settling tank (3) and the second-stage extraction settling tank (4), and the first-stage extraction mixer (20) and the second-stage extraction mixer (21) are communicated through pipelines; The first-stage extraction settling tank (3) is provided with an oxidized regeneration tower pipeline (23) for rich extractant, and the first-stage extraction settling tank (3) is connected with an alkali liquid heater (24) through a pipeline; the tube side of the alkali liquid heater (24) is provided with a hot water inlet pipeline (25) and a hot water return pipeline (26); the first-stage extraction mixer (20) and the second-stage extraction mixer (21) are both provided with a FI-901A / B lean extractant feeding pipeline (27); A water washing Venturi tube (28) is arranged on the pipeline between the second-stage extraction settling tank (4) and the water washing settling tank (5); the water washing settling tank (5) and the bottom of the liquefied gas sand filter tower (6) are provided with an alkali-containing sewage outlet pipeline (29); the water washing Venturi tube (28) is also connected with a system desalted water inlet pipeline (30); The liquefied gas sand filter tower (6) is connected with a refined liquefied gas discharging pipeline (32); The application further comprises an oxidized regeneration tower (33), a three-phase separation tank (34), a tail gas settling tank (35) and an emergency venting tank (36) which are sequentially communicated through pipelines; The application further comprises an oxidized regeneration tower (33), a three-phase separation tank (34), a tail gas settling tank (35) and an emergency venting tank (36) which are sequentially communicated through pipelines; The lower part of the oxidation regeneration tower (33) is connected with a rich extractant feeding pipeline (37), an oxygen feeding pipeline (38) and a self-stabilized gasoline anti-extraction oil feeding pipeline (39), the rich extractant feeding pipeline (37) is provided with a regeneration mixer (40) which is communicated with the three-phase separation tank (34) through a pipeline, the top of the three-phase separation tank (34) is communicated with a tail gas settling tank (35) through a tail gas outflow pipeline (41), the tail gas settling tank (35) is connected with an emergency venting tank (36), the bottom of the three-phase separation tank (34) is provided with a regenerated lean extractant circulating pipeline (42) which is communicated with the oxidation regeneration tower (33); The bottom of the oxidation regeneration tower (33) is provided with a fresh lye outflow pipeline (44) which is communicated with the new lye feeding pipeline (18) from the filter and is circulated into the pre-alkali washing settling tank (2); the oxidation regeneration tower (33) and the three-phase separation tank (34) are both connected with a system desalted water feeding pipeline (45), a lye or extractant feeding pipeline (46) from the agent preparation tank and a lean liquid to MI-903A / B outflow pipeline (47); The rich extractant feeding pipeline (37) is communicated with the three-phase separation tank (34) through a pipeline; the rich extractant feeding pipeline (37) is also connected with a heavy oil anti-extraction oil pipeline (48) for back refining; The new lye feeding pipeline (18) from the filter is communicated with the fresh lye outflow pipeline (44), the system desalted water inflow pipeline (30) is communicated with the system desalted water feeding pipeline (45); the lean liquid to MI-903A / B outflow pipeline (47) is provided with two branch pipelines, one of which is communicated with the FI-901A / B lean extractant feeding pipeline (27) and the other of which is communicated with the pre-alkali washing mixer (11), the rich extractant to the oxidation regeneration tower pipeline (23) is communicated with the rich extractant feeding pipeline (37).

2. The liquefied gas desulfurization system as claimed in claim 1, wherein, A liquefied gas feeding pump (9) is arranged on the pipeline between the liquefied gas buffer tank (1) and the pre-alkali washing settling tank (2).

3. The liquefied gas desulfurization system as claimed in claim 1, wherein, A semi-lean agent pump (22) is arranged on the pipeline between the primary extraction mixer (20) and the secondary extraction settling tank (4).

4. The liquefied gas desulfurization system as claimed in claim 1, wherein, A water washing feeding pump (31) is arranged on the system desalted water inflow pipeline (30).

5. The liquefied gas desulfurization system as claimed in claim 1, wherein, A lean solvent pump (43) is arranged on the regenerated lean extractant circulating pipeline (42).

6. The liquefied gas desulfurization system as claimed in claim 1, wherein, Control valve one (49) and control valve two (50) are arranged on the circulating water inflow pipeline (14), control valve three (51) and control valve four (52) are arranged on the circulating water outflow pipeline (15), control valve five (53) and control valve six (54) are arranged on the heat medium water inflow pipeline (16), control valve seven (55) and control valve eight (56) are arranged on the heat medium water outflow pipeline (17), the circulating water inflow pipeline (14) and the circulating water outflow pipeline (15) are communicated through a pipeline, the communicated pipeline is provided with control valve nine (57), the heat medium water inflow pipeline (16) and the heat medium water outflow pipeline (17) are communicated through a pipeline.

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