Comprehensive recovery method and device for saturated light hydrocarbon

Abstract

The invention belongs to the field of oil refining and chemical engineering, and relates to a comprehensive recovery method and device for saturated light hydrocarbon. The method has the following advantages: the naphtha-containing liquid phase after the atmospheric and vacuum distillation unit, each hydrofining unit and the sulfur-containing gas phase are pressurized and cooled is concentrated and stabilized, the content of heavy components in the sulfur-containing rich gas is reduced, and the foaming risk of the gas phase desulfurization tower is reduced; the tail gas of the whole plant is uniformly brought into a recovery range for centralized recovery, so that the recovery range is widened, and the loss of C2 and above components is reduced; an atmospheric and vacuum distillation unit and a hydrocracking unit are not required to be independently provided with an absorption stabilizing system, so that the secondary separation problem of key components is reduced; crude hydrocarbon after desulfurization and mercaptan removal and crude hydrocarbon condensed by a cooler at an outlet of a third raw material gas compressor are sent to the middle section of the absorption tower, C3-C5 components contained in the raw materials are used as absorbents, the amount of circulating C4 is reduced, and energy consumption can be reduced.

Description

Technical Field

[0001] The present invention belongs to the field of oil refining and chemical industry, and more specifically, relates to a comprehensive recovery method and device for saturated light hydrocarbons, and more specifically to a device and method for recovering saturated light hydrocarbons from the atmospheric and vacuum distillation, hydrocracking, hydrofining, aromatics reforming and other devices in a refinery that are rich in saturated light hydrocarbons. Background Art

[0002] Saturated light hydrocarbons in refineries primarily come from atmospheric and vacuum unit overhead gas and mixed naphtha, overhead gas and crude hydrocarbons from the hydrogen sulfide stripping towers of various hydrocracking units, fuel gas from various hydrotreating units, disproportionated isomerization tail gas and pre-hydrogenated fuel gas from aromatics reformers, hydrogenation low-fraction PSA tail gas, reformer PSA tail gas, and hydrocracking membrane separation tail gas. Light hydrocarbon recovery from these streams primarily involves atmospheric and vacuum light hydrocarbon recovery and various hydrocracking absorption and stabilization systems to recover liquefied gas components such as C3 and C4. C2 is used in dry gas as fuel. With the development of integrated refining and chemical integration, further recovery of C2 from dry gas to provide lightweight ethylene feed for ethylene plants has gained importance. Chemical refineries with ethylene plants typically install new C2 recovery units to recover C2 from dry gas and feed the ethane-rich gas to the ethylene unit cracking furnaces as cracking feed, reducing external ethylene feed purchases and further improving the refinery's economic efficiency.

[0003] The conventional process setup involves recovering liquefied gas through absorption stabilization, and then recovering the C2 component through a C2 recovery unit that uses shallow cold oil absorption technology. Since the C2 recovery unit uses C4 as an absorbent to absorb the C2 component in the absorption tower, the C4 component and the C2 component are separated in advance in the upstream absorption and stabilization system. The C2 recovery unit needs to supplement with C4 as an absorbent to recover C2, which results in a secondary separation of the C2 / C4 components. Meanwhile, for the hydrocracking unit, the C4 component and the naphtha component are separated in the debutanizer / hydrogen sulfide stripper. To achieve the separation of the C2 and C3 components in the absorption and stabilization system, naphtha is used as an absorbent and mixed again in the absorption tower. To obtain the liquefied gas product, they need to be separated again in the stabilization tower, which is the secondary separation of the C4 component and the naphtha component. The secondary separation of key components increases separation energy consumption and the number of equipment. Since C2, C3 and C4 components can all be used as ethylene cracking materials, and C4 is also needed as an absorbent to recover C2 components, the necessity of setting up an absorption stabilization system is greatly reduced for chemical refineries that do not have C3 and C4 deep processing and comprehensive utilization equipment.

[0004] The present invention is proposed in order to realize the full recovery of saturated light hydrocarbons in all units of the plant, provide lightweight ethylene materials for the ethylene unit, optimize the component separation sequence, simplify the separation process, and reduce investment and energy consumption. Summary of the Invention

[0005] The purpose of the present invention is to provide a comprehensive recovery device and method for saturated light hydrocarbons in the entire plant, which has a reasonable component separation sequence, reduced energy consumption and more optimized equipment quantity. Through this method, comprehensive recovery of saturated light hydrocarbons in atmospheric and vacuum units, various hydrocracking units, various hydrogen refining units and aromatics reforming units can be achieved, the operating conditions of the absorption tower can be optimized, and energy consumption can be reduced.

[0006] In order to achieve the above object, the first aspect of the present invention provides a comprehensive recovery method for saturated light hydrocarbons, the recovery method comprising:

[0007] (1) Gas phase pressurization I: The hydrotreated sulfur-rich gas is compressed and pressurized by the first feed gas compressor, cooled by the cooler I, and separated by the liquid separator I. The sulfur-rich and heavy component-rich gas is obtained at the top of the tank, and the sulfur-rich and heavy component crude hydrocarbons are obtained at the bottom of the tank;

[0008] (2) Naphtha stabilization in the whole plant: mixed naphtha, sulfur-containing and heavy component rich gas and sulfur-containing and heavy component crude hydrocarbon are sent to the stabilization tower for stabilization treatment. Stabilized naphtha is obtained at the bottom of the tower and divided into two parts. One part is used as the mixed naphtha product, and the top gas phase of the stabilization tower is obtained at the top of the tower. After condensation in the condenser, it is sent to the stabilization tower reflux tank to obtain the top rich gas of the stabilization tower reflux tank and the bottom liquid phase of the stabilization tower reflux tank;

[0009] (3) Gas phase pressure boosting II: The rich gas at the top of the stabilization tower reflux tank is sent to the second raw gas compressor for compression and pressure boosting, cooled in cooler II, and separated in separator II to obtain the rich gas at the top of separator II and the liquid phase at the bottom of separator II;

[0010] (4) Rich gas desulfurization: The rich gas at the top of the separator tank II passes through the superheater and is sent to the gas phase desulfurization tower, where it comes into contact with the lean amine liquid in reverse flow to remove hydrogen sulfide and obtain the rich gas from the gas phase desulfurization tower;

[0011] (5) Crude hydrocarbon desulfurization: The liquid phase at the bottom of the stabilization tower reflux tank is pressurized by the stabilization tower reflux pump and then divided into two parts. One part enters the desulfurization and demercaptan tower, and the liquid phase at the bottom of the separator tank II is pumped out by the crude hydrocarbon pump II and sent to the desulfurization and demercaptan tower. After removing hydrogen sulfide and mercaptan, crude hydrocarbon is obtained from the desulfurization and demercaptan tower.

[0012] (6) Gas phase pressurization III: The PSA tail gas is pressurized by the third raw gas compressor, cooled by cooler III, and separated by separator III to obtain a gas phase at the top of separator III and a liquid phase at the bottom of separator III;

[0013] (7) Gas-liquid balance: The rich gas from the gas phase desulfurization tower, the gas phase at the top of the separator III tank, and the tail gas separated by the hydrocracking membrane are mixed to obtain sulfur-free rich gas. The sulfur-free rich gas is cooled by the shallow cooler I and then enters the separator IV for separation to obtain the gas phase at the top of the separator IV tank and the liquid phase at the bottom of the separator IV tank;

[0014] (8) C1 / C2 separation: The gas phase at the top of the separator IV enters the absorption tower for C1 / C2 separation, wherein the liquid phase at the bottom of the separator III is extracted by the crude hydrocarbon pump III and mixed with the crude hydrocarbon of the desulfurization and demercaptan unit to obtain sulfur-free crude hydrocarbon, which is then cooled by the shallow cooler II and sent to the middle section of the absorption tower as the absorbent in the middle of the absorption tower. At least one of a mixture of C4, normal C4, isomeric C4 and liquefied gas is used as the absorbent at the top of the absorption tower to obtain the gas phase at the top of the absorption tower and the liquid phase at the bottom of the absorption tower. The liquid phase at the bottom of the absorption tower is returned to be mixed with the sulfur-free rich gas for gas-liquid equilibrium;

[0015] (9) C3 / C4 separation: The liquid phase at the bottom of separator IV is further separated by a demethanizer and a depropanizer to obtain an ethane-rich gas product and a mixed C4 product;

[0016] (10) Reabsorption: The gas phase at the top of the absorption tower is sent to the reabsorption tower to recover C3 and components above C3. Another part of the stabilized naphtha is used as the reabsorbent. The gas phase at the top of the reabsorption tower is produced as dry gas, and the liquid phase at the bottom of the reabsorption tower is returned to the stabilization tower.

[0017] In the present invention, the mixed naphtha comes from various hydrogen refining units, atmospheric and vacuum units, and the gas and liquid phases of various hydrogen-refined sulfur-containing fuel gases after passing through the second raw gas compressor and cooling and liquid separation, thereby reducing the carbon five and above components in the sulfur-containing fuel gas and reducing the risk of foaming in the gas phase desulfurization tower.

[0018] According to the present invention, gas phase desulfurization adopts medium and high pressure desulfurization to reduce the amount of lean amine liquid and the diameter of the desulfurization tower, and a sulfur-rich gas superheater is set in front of the gas phase desulfurization tower.

[0019] According to the present invention, the crude hydrocarbons in the reflux tank of the stabilization tower are pressurized by a reflux pump, and are sent to the desulfurization and demercaptan after the degree of supercooling is increased. After the gas phase in the reflux tank of the stabilization tower is pressurized by the first raw gas compressor, cooled by the cooler, and separated by the liquid separator, a part of the C3 / C4 components in the gas phase will be condensed into the liquid phase, thereby reducing the content of the heavy components in the gas phase and reducing the risk of foaming in the gas phase desulfurization tower. The liquid phase is pressurized by a pump, and is sent to the desulfurization and demercaptan after the degree of supercooling is increased.

[0020] According to the present invention, the hydrogenated low-fraction gas PSA tail gas and the reformed hydrogen PSA tail gas are pressurized by the third raw gas compressor, cooled by the cooler, and separated by the liquid separator, and the gas phase and the gas phase desulfurized rich gas are sent to the shallow cooler I together, and the liquid phase is pressurized by the pump and sent, together with the crude hydrocarbons after desulfurization and demercaptanization, through the shallow cooler to be cooled to 15°C to 20°C, and then sent to the middle section of the absorption tower.

[0021] According to the present invention, the cooled raw gas and the crude hydrocarbon at the bottom of the absorption tower pass through a shallow cooler together and are cooled to 15°C to 20°C. During the mixed cooling process, the crude hydrocarbon at the bottom of the absorption tower will further absorb C2 and above components in the raw material, reducing the load of the absorption tower. After mixed cooling, the gas phase passes through a separatory tank and then enters the absorption tower, and the liquid phase is sent to the demethanizer.

[0022] According to the present invention, the top of the absorption tower uses poor C4 as the absorbent, and the middle of the tower uses raw crude hydrocarbon as the absorbent, which jointly absorb C2 and above components in the raw gas to achieve C1 / C2 separation.

[0023] According to the present invention, the intermediate reboiler and the bottom reboiler of the demethanizer use the depleted carbon four at the bottom of the depropanizer as the heat source, do not need to consume steam, and no cooling reflux is set at the top of the tower, and directly return to the inlet of the third raw gas compressor.

[0024] According to the present invention, the bottom of the depropanizer is poor in carbon four, part of which is sent to the top of the absorption tower as a circulating absorbent after passing through the intermediate reboiler of the demethanizer and the bottom reboiler, and part of it is sent out of the device. The top of the tower is a mixture of carbon two, carbon three and carbon four components, and carbon three and carbon four are no longer strictly separated. The top gas is sent to the ethylene unit for cracking.

[0025] According to the present invention, the dry gas from the top of the absorption tower is sent to the reabsorption tower, and the stabilized naphtha at the bottom of the stabilization tower is used as the reabsorbent to recover the entrained C4 absorbent and reduce the absorbent loss. The mixed naphtha at the bottom of the tower is then returned to the stabilization tower.

[0026] According to the present invention, preferably, the operating temperature of the top of the stabilization tower is 40-60° C., and the operating pressure is 0.8-1.2 MPaG.

[0027] According to the present invention, preferably, the operating temperature of the stabilization tower reflux tank is 30-45°C.

[0028] According to the present invention, preferably, the operating temperature of the gas phase desulfurization tower is 40-45° C., and the operating pressure is 2.5-4.5 MPaG.

[0029] According to the present invention, preferably, the operating temperature of the desulfurization and demercaptan tower is 35-45° C., and the operating pressure is 3.0-5.0 MPaG.

[0030] According to the present invention, preferably, the outlet pressure of the first raw gas compressor is 2.5-4.5 MPaG, the crude hydrocarbon containing sulfur and heavy components is sent to the middle part of the stabilization tower, and the rich gas containing sulfur and heavy components is sent to the upper part of the stabilization tower.

[0031] According to the present invention, preferably, the outlet pressure of the second raw gas compressor is 2.5-4.5 MPaG.

[0032] According to the present invention, preferably, another part of the liquid phase at the bottom of the stabilization tower reflux tank is sent to the upper part of the stabilization tower.

[0033] According to the present invention, preferably, another portion of the stabilized naphtha is used as a reabsorbent.

[0034] According to the present invention, preferably, the temperature of the shallow cooler I is 15-20° C., and the pressure is 2.0-4.0 MPag.

[0035] According to the present invention, preferably, the pressure of the absorption tower is 2.0-4.0 MPag.

[0036] According to the present invention, preferably, the liquid phase at the bottom of the liquid tank IV enters the demethanizer, the gas phase obtained at the top of the demethanizer is returned and mixed with the PSA tail gas, and the gas phase is pressurized III, and the liquid phase at the bottom of the demethanizer is sent to the depropanizer, and an ethane-rich gas product is obtained at the top of the tower, and a mixed C4 product is obtained at the bottom of the tower.

[0037] According to the present invention, preferably, part of the mixed C4 product is used as the C4-depleted absorbent circulated at the top of the absorption tower.

[0038] According to the present invention, preferably, the top pressure of the demethanizer is 1.0-1.5 MPag.

[0039] According to the present invention, preferably, the top pressure of the depropanizer is 1.4-2.0 MPag.

[0040] A second aspect of the present invention provides a comprehensive recovery device for saturated light hydrocarbons, comprising: a mixed naphtha feed line, a hydrorefining sulfur-rich gas feed line, a PSA tail gas feed line, a hydrocracking membrane separation tail gas feed line, a stabilization tower, a first raw gas compressor, a cooler I, a liquid separator I, a second raw gas compressor, a cooler II, a liquid separator II, a crude hydrocarbon pump II, a superheater, a gas phase desulfurization tower, a desulfurization and sweetening unit, a third raw gas compressor, a cooler III, a liquid separator III, a crude hydrocarbon pump III, a shallow cooler I, a shallow cooler II, a liquid separator IV, an absorption tower, a demethanizer, a depropanizer, and a reabsorption tower;

[0041] Among them, the hydrofining sulfur-rich gas feed pipeline is connected to the first raw gas compressor, the cooler 1 and the separator 1 in sequence, and the separator 1 is provided with a separator 1 tank top discharge pipeline and a separator 1 tank bottom discharge pipeline;

[0042] The mixed naphtha feed pipeline, the separator tank 1 top discharge pipeline and the separator tank 1 bottom discharge pipeline are connected to the stabilization tower, the stabilization tower is provided with a stabilization tower top discharge pipeline and a stabilization tower bottom discharge pipeline, the stabilization tower bottom discharge pipeline is divided into two branches, one of which is used as a mixed petroleum naphtha product discharge pipeline, the upper part of the stabilization tower is also provided with a condenser and a stabilization tower reflux tank, the stabilization tower top discharge pipeline is sequentially connected to the condenser and the stabilization tower reflux tank, the stabilization tower reflux tank is provided with a stabilization tower reflux tank top discharge pipeline and a stabilization tower reflux tank bottom discharge pipeline;

[0043] The top discharge pipeline of the stabilization tower reflux tank is connected to the second raw gas compressor, cooler II and separator II in sequence, and the separator II is provided with a top discharge pipeline of the separator II tank and a bottom discharge pipeline of the separator II tank;

[0044] The discharge pipeline from the top of the separator tank II is connected to the superheater and the gas phase desulfurization tower in sequence, and the gas phase desulfurization tower is provided with a gas phase desulfurization tower discharge pipeline;

[0045] The discharging pipeline at the bottom of the stabilization tower reflux tank is connected to the stabilization tower reflux pump and is divided into two branches, one of which is connected to the desulfurization and sweetening tower. The discharging pipeline at the bottom of the separator tank II is connected to the crude hydrocarbon pump II and the desulfurization and sweetening tower in sequence. The desulfurization and sweetening tower is provided with a desulfurization and sweetening tower discharging pipeline.

[0046] The PSA tail gas feed pipeline is connected to the third raw gas compressor, cooler III and separator III in sequence, and the separator III is provided with a separator III tank top discharge pipeline and a separator III tank bottom discharge pipeline;

[0047] The top discharge pipeline of the liquid separator III, the hydrocracking membrane separation tail gas feed pipeline and the gas phase desulfurization tower discharge pipeline are sulfur-free rich gas pipelines, and then connected in sequence to the shallow cooler I and the liquid separator IV, and the liquid separator IV is provided with a top discharge pipeline of the liquid separator IV and a bottom discharge pipeline of the liquid separator IV;

[0048] The top discharge pipeline of the separator IV is connected to the absorption tower, the bottom discharge pipeline of the separator III is connected to the crude hydrocarbon pump III, and then merged with the discharge pipeline of the desulfurization and demercaptan tower, and then sequentially connected to the shallow cooler II and the middle part of the absorption tower. The absorption tower is provided with an absorption tower top discharge pipeline and an absorption tower bottom discharge pipeline, and the absorption tower bottom discharge pipeline merges with the sulfur-free rich gas pipeline;

[0049] The bottom discharge pipeline of the separator IV tank is connected to the demethanizer and the depropanizer in sequence, and the depropanizer is provided with a depropanizer top discharge pipeline and a depropanizer bottom discharge pipeline;

[0050] The top discharge pipeline of the absorption tower is connected to the reabsorption tower. The reabsorption tower is provided with a top discharge pipeline of the reabsorption tower and a bottom discharge pipeline of the reabsorption tower. The bottom discharge pipeline of the reabsorption tower is connected to the middle of the stabilization tower.

[0051] According to the present invention, preferably, the discharge line from the top of the liquid separator tank 1 is connected to the upper part of the stabilization tower, and the discharge line from the bottom of the liquid separator tank 1 is connected to the middle part of the stabilization tower; another discharge line from the bottom of the stabilization tower is connected to the reabsorption tower.

[0052] According to the present invention, preferably, the demethanizer is provided with a demethanizer top discharge pipeline and a demethanizer bottom discharge pipeline, the demethanizer top discharge pipeline merges with the PSA tail gas feed pipeline, the demethanizer bottom discharge pipeline is connected to the depropanizer, and the propane bottom discharge pipeline is divided into two branches, one as a mixed C4 product discharge pipeline, and the other connected to the upper part of the absorption tower.

[0053] According to the present invention, preferably, another stabilization tower reflux tank bottom discharge pipeline is connected to the upper part of the stabilization tower.

[0054] According to the present invention, preferably, the absorption tower is provided with 1 to 3 middle refluxes; the demethanizer is not provided with a condenser at the top, an intermediate reboiler is provided in the middle of the tower, and a reboiler is provided at the bottom of the tower.

[0055] Compared with the prior art, the present invention has the following advantages:

[0056] (1) In the present invention, the naphtha-containing liquid phase after the atmospheric and vacuum unit, each hydrorefining unit and the sulfur-containing gas phase are pressurized and cooled is centralized and stabilized, thereby reducing the content of heavy components in the sulfur-containing rich gas and reducing the foaming risk of the gas phase desulfurization tower.

[0057] (2) In the present invention, each hydrotreated sulfur-containing fuel gas, hydrotreated low-fraction gas PSA tail gas, reformed hydrogen PSA tail gas, disproportionated and post-hydrogenated fuel gas, and hydrocracking membrane separation tail gas are uniformly included in the recovery range for centralized recovery, thereby increasing the recovery range and reducing the loss of carbon dioxide and above components.

[0058] (3) The present invention no longer requires the atmospheric and vacuum unit and the hydrocracking unit to be equipped with a separate absorption stabilization system, thereby reducing the problem of secondary separation of key components.

[0059] (4) In the present invention, the crude hydrocarbons after desulfurization and demercaptanization and the crude hydrocarbons condensed by the cooler at the outlet of the third raw gas compressor are sent to the middle section of the absorption tower, and the C3 to C5 components contained in the raw materials themselves are used as absorbents, thereby reducing the amount of circulating C4 and helping to reduce energy consumption.

[0060] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0062] Figure 1 The process flow chart of comprehensive recovery of saturated light hydrocarbons in the whole plant in Example 1 of the present invention is shown.

[0063] Description of reference numerals:

[0064] 1. Stabilization tower; 2. Stabilization tower reflux tank; 3. Stabilization tower reflux pump; 4. Second raw gas compressor; 5. Cooler II; 6. Separator II; 7. Crude hydrocarbon pump II; 8. Superheater; 9. Gas phase desulfurization tower; 10. First raw gas compressor; 11. Cooler I; 12. Separator I; 13. Third raw gas compressor; 14. Cooler III; 15. Separator III; 16. Crude hydrocarbon pump III; 17. Shallow cooler I; 18. Shallow cooler II; 19. Desulfurization and sweetening tower; 23. Separator IV; 24. Absorption tower; 25. Demethanizer; 26. Depropanizer; 27. Reabsorption tower;

[0065] S-1, mixed naphtha; S-2, sulfur-containing and heavy component rich gas; S-3, sulfur-containing and heavy component crude hydrocarbons; S-4, hydrorefined sulfur-containing rich gas; S-5, PSA tail gas; S-6, sulfur-free rich gas; S-7, sulfur-free crude hydrocarbons; S-9, circulating C4-poor absorbent; S-10, mixed C4 product; S-11, ethane-rich gas product; S-12, dry gas; S-13, mixed naphtha absorbent; S-14, mixed naphtha product; S-15, hydrocracking membrane separation tail gas. DETAILED DESCRIPTION

[0066] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0067] Example 1

[0068] The plant's comprehensive saturated light hydrocarbon recovery unit includes: a mixed naphtha feed pipeline, a hydrotreating sulfur-rich gas feed pipeline, a PSA tail gas feed pipeline, a hydrocracking membrane separation tail gas feed pipeline, a stabilization tower 1, a first feed gas compressor 10, a cooler I11, a separator I12, a second feed gas compressor 4, a cooler II 5, a separator II 6, a crude hydrocarbon pump II 7, a superheater 8, a gas phase desulfurization tower 9, a desulfurization and sweetening unit 19, a third feed gas compressor 13, a cooler III 14, a separator III 15, a crude hydrocarbon pump III 16, a shallow cooler I17, a shallow cooler II 18, a separator IV 23, an absorption tower 24, a demethanizer 25, a depropanizer 26, and a reabsorption tower 27.

[0069] Among them, the hydrofining sulfur-rich gas feed pipeline is connected to the first raw gas compressor 10, the cooler I11 and the separator I12 in sequence, and the separator I12 is provided with a separator I tank top discharge pipeline and a separator I tank bottom discharge pipeline;

[0070] The mixed naphtha feed pipeline is connected to the stabilization tower, the separator 1 tank top discharge pipeline is connected to the upper part of the stabilization tower 1, the separator 1 tank bottom discharge pipeline is connected to the middle part of the stabilization tower, the stabilization tower is provided with a stabilization tower top discharge pipeline and a stabilization tower bottom discharge pipeline, the stabilization tower bottom discharge pipeline is divided into two branches, one of which is used as a mixed petroleum naphtha product discharge pipeline, and the other is connected to the reabsorption tower. The upper part of the stabilization tower is also provided with a condenser and a stabilization tower reflux tank, the stabilization tower top discharge pipeline is connected to the condenser and the stabilization tower reflux tank in sequence, and the stabilization tower reflux tank is provided with a stabilization tower reflux tank tank top discharge pipeline and a stabilization tower reflux tank tank bottom discharge pipeline;

[0071] The top discharge pipeline of the stabilization tower reflux tank is connected to the second raw gas compressor 4, the cooler II 5 and the separator II 6 in sequence. The separator II 6 is provided with a top discharge pipeline of the separator II tank and a bottom discharge pipeline of the separator II tank;

[0072] The discharge pipeline from the top of the separator tank II is connected to the superheater 8 and the gas phase desulfurization tower 9 in sequence, and the gas phase desulfurization tower is provided with a gas phase desulfurization tower discharge pipeline;

[0073] After the stabilization tower reflux tank bottom discharge pipeline is connected to the stabilization tower reflux pump 3, it is divided into two branches, one of which is connected to the desulfurization and demercaptan tower 19, and the separator tank II tank bottom discharge pipeline is sequentially connected to the crude hydrocarbon pump II and the desulfurization and demercaptan tower 19, and the desulfurization and demercaptan tower 19 is provided with a desulfurization and demercaptan tower discharge pipeline;

[0074] The PSA tail gas feed pipeline is connected to the third raw gas compressor 13, the cooler III 14 and the liquid separator III 15 in sequence. The liquid separator III 15 is provided with a discharge pipeline from the top of the liquid separator III and a discharge pipeline from the bottom of the liquid separator III.

[0075] The top discharge pipeline of the liquid separator III, the hydrocracking membrane separation tail gas feed pipeline and the gas phase desulfurization tower discharge pipeline are merged into a sulfur-free rich gas pipeline, which is then sequentially connected to the shallow cooler I17 and the liquid separator IV 23. The liquid separator IV 23 is provided with a top discharge pipeline of the liquid separator IV and a bottom discharge pipeline of the liquid separator IV.

[0076] The top discharge line of the separator IV is connected to the absorption tower 24, the bottom discharge line of the separator III is connected to the crude hydrocarbon pump III, and then merges with the discharge line of the desulfurization and demercaptan tower, and then sequentially connected to the shallow cooler II 18 and the middle part of the absorption tower. The absorption tower is provided with an absorption tower top discharge line and an absorption tower bottom discharge line, and the absorption tower bottom discharge line merges with the sulfur-free rich gas pipeline;

[0077] The bottom discharge pipeline of the separator tank IV is connected to the demethanizer 25, and the demethanizer 25 is provided with a demethanizer top discharge pipeline and a demethanizer bottom discharge pipeline. The demethanizer top discharge pipeline is merged with the PSA tail gas feed pipeline, and the demethanizer bottom discharge pipeline is connected to the depropanizer 26. The propane bottom discharge pipeline is divided into two branches, one as a mixed C4 product discharge pipeline, and the other is connected to the upper part of the absorption tower;

[0078] The top discharge pipeline of the absorption tower is connected to the reabsorption tower 27. The reabsorption tower 27 is provided with a top discharge pipeline of the reabsorption tower and a bottom discharge pipeline of the reabsorption tower. The bottom discharge pipeline of the reabsorption tower is connected to the middle of the stabilization tower.

[0079] The above device is used to carry out comprehensive recovery of saturated light hydrocarbons in the whole plant. The process flow chart is as follows: Figure 1 As shown:

[0080] (1) Gas phase pressurization I: The hydrotreated sulfur-rich gas is compressed and pressurized by the first raw gas compressor, cooled by cooler I, and separated by liquid separator I. The sulfur-rich and heavy component-rich gas is obtained at the top of the tank, and the sulfur-rich and heavy component crude hydrocarbons are obtained at the bottom of the tank; the outlet pressure of the first raw gas compressor is 3.0 MPag.

[0081] (2) Naphtha stabilization in the whole plant: mixed naphtha, sulfur-containing and heavy component rich gas and sulfur-containing and heavy component crude hydrocarbons are sent to the stabilization tower for stabilization treatment. Stabilized naphtha is obtained at the bottom of the tower and divided into two parts. One part is used as the mixed naphtha product, and the top gas phase of the stabilization tower is obtained at the top of the tower. After condensation in the condenser, it is sent to the stabilization tower reflux tank to obtain the rich gas at the top of the stabilization tower reflux tank and the liquid phase at the bottom of the stabilization tower reflux tank; the operating pressure of the stabilization tower is 1.0 MPag, the top temperature is 45°C, and the outlet pressure of the stabilization tower reflux pump is 3.5 MPag.

[0082] (3) Gas phase pressure boosting II: The rich gas at the top of the reflux tank of the stabilization tower is sent to the second raw gas compressor for compression and pressure boosting, cooled in the cooler II and separated in the liquid separator II to obtain the rich gas at the top of the liquid separator II and the liquid phase at the bottom of the liquid separator II; the outlet pressure of the second raw gas compressor is 3.0 MPag.

[0083] (4) Rich gas desulfurization: The rich gas from the top of separator II passes through the superheater and is sent to the gas phase desulfurization tower, where it comes into contact with the lean amine liquid in reverse to remove hydrogen sulfide and obtain the rich gas from the gas phase desulfurization tower; the superheater outlet temperature is 43°C, and the overheating is 3°C.

[0084] (5) Crude hydrocarbon desulfurization: The liquid phase at the bottom of the stabilization tower reflux tank is pressurized by the stabilization tower reflux pump and then divided into two parts. One part enters the desulfurization and demercaptan tower, and the liquid phase at the bottom of the separator tank II is pumped out by the crude hydrocarbon pump II and sent to the desulfurization and demercaptan tower. After removing hydrogen sulfide and mercaptan, crude hydrocarbon is obtained from the desulfurization and demercaptan tower.

[0085] (6) Gas phase pressurization III: The PSA tail gas is pressurized by the third raw gas compressor, cooled by cooler III, and separated by separator III to obtain a gas phase at the top of separator III and a liquid phase at the bottom of separator III;

[0086] (7) Gas-liquid balance: The rich gas from the gas phase desulfurization tower, the gas phase at the top of separator III and the tail gas separated by the hydrocracking membrane are mixed to obtain sulfur-free rich gas. The sulfur-free rich gas is cooled by the shallow cooler I and then enters the separator IV for separation to obtain the gas phase at the top of separator IV and the liquid phase at the bottom of liquid tank IV; the outlet temperature of the shallow cooler is 15°C.

[0087] (8) C1 / C2 separation: The gas phase at the top of the separator IV enters the absorption tower for C1 / C2 separation, wherein the liquid phase at the bottom of the separator III is extracted by the crude hydrocarbon pump III and mixed with the crude hydrocarbon of the desulfurization and demercaptan unit to obtain sulfur-free crude hydrocarbon, which is then cooled by the shallow cooler II and sent to the middle section of the absorption tower as the absorbent in the middle of the absorption tower. At least one of a mixture of C4, normal C4, isomeric C4 and liquefied gas is used as the absorbent at the top of the absorption tower to obtain the gas phase at the top of the absorption tower and the liquid phase at the bottom of the absorption tower. The liquid phase at the bottom of the absorption tower is returned to be mixed with the sulfur-free rich gas for gas-liquid equilibrium;

[0088] (9) C3 / C4 separation: The liquid phase at the bottom of the liquid tank IV enters the demethanizer, and the gas phase obtained at the top of the demethanizer is returned to mix with the PSA tail gas, and the gas phase is pressurized III. The liquid phase at the bottom of the demethanizer is sent to the depropanizer, and an ethane-rich gas product is obtained at the top of the tower, and a mixed C4 product is obtained at the bottom of the tower, a part of which is used as a C4-poor absorbent for circulation at the top of the absorption tower; the top pressure of the demethanizer is 1.0-1.5Mpag; the top pressure of the depropanizer is 1.4~2.0Mpag.

[0089] (10) Reabsorption: The gas phase at the top of the absorption tower is sent to the reabsorption tower to recover C3 and components above C3. Another part of the stabilized naphtha is used as the reabsorbent. The gas phase at the top of the reabsorption tower is produced as dry gas, and the liquid phase at the bottom of the reabsorption tower is returned to the stabilization tower.

[0090] The composition and properties of the products of dry gas, ethane-rich gas and mixed C4 separated from light hydrocarbons by the above method are shown in Tables 1 to 3.

[0091] Table 1 Dry gas properties

[0092]

[0093]

[0094] Table 2 Properties of ethane-rich gas

[0095] Temperature, °C 43 Pressure, MPag 1.45 composition v％ <![CDATA[CO2]]> 0.1949 <![CDATA[CH4]]> 0.7773 <![CDATA[C2H6]]> 41.3878 <![CDATA[C3H8]]> 32.6209 <![CDATA[IC4H 10 ]]> 17.8040 <![CDATA[NC4H 10 ]]> 7.1960 <![CDATA[H2S]]> 0.0010 <![CDATA[H2O]]> 0.0170 C5+ 0.0010

[0096] Table 3 Properties of mixed C4

[0097] Temperature, °C 40 Pressure, MPag 1.0 composition wt% <![CDATA[C3H8]]> 0.005 <![CDATA[IC4H 10 ]]> 0.337634 <![CDATA[NC4H 10 ]]> 0.390066 <![CDATA[H2O]]> 0.001895 C5+ 0.2655

[0098] While various embodiments of the present invention have been described above, the above description is intended to be illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A comprehensive recovery method for saturated light hydrocarbons, characterized in that: The recycling method includes: (1) Gas phase pressurization I: The hydrotreated sulfur-rich gas is compressed and pressurized by the first feed gas compressor, cooled by the cooler I, and separated by the liquid separator I. The sulfur-rich and heavy component-rich gas is obtained at the top of the tank, and the sulfur-rich and heavy component crude hydrocarbons are obtained at the bottom of the tank; (2) Naphtha stabilization in the whole plant: mixed naphtha, sulfur-containing and heavy component rich gas and sulfur-containing and heavy component crude hydrocarbon are sent to the stabilization tower for stabilization treatment. Stabilized naphtha is obtained at the bottom of the tower and divided into two parts. One part is used as the mixed naphtha product, and the top gas phase of the stabilization tower is obtained at the top of the tower. After condensation in the condenser, it is sent to the stabilization tower reflux tank to obtain the top rich gas of the stabilization tower reflux tank and the bottom liquid phase of the stabilization tower reflux tank; (3) Gas phase pressure boosting II: The rich gas at the top of the stabilization tower reflux tank is sent to the second raw gas compressor for compression and pressure boosting, cooled in cooler II, and separated in separator II to obtain the rich gas at the top of separator II and the liquid phase at the bottom of separator II; (4) Rich gas desulfurization: The rich gas at the top of the separator tank II passes through the superheater and is sent to the gas phase desulfurization tower, where it comes into contact with the lean amine liquid in reverse flow to remove hydrogen sulfide and obtain the rich gas from the gas phase desulfurization tower; (5) Crude hydrocarbon desulfurization: The liquid phase at the bottom of the stabilization tower reflux tank is pressurized by the stabilization tower reflux pump and then divided into two parts. One part enters the desulfurization and demercaptan tower, and the liquid phase at the bottom of the separator tank II is pumped out by the crude hydrocarbon pump II and sent to the desulfurization and demercaptan tower. After removing hydrogen sulfide and mercaptan, crude hydrocarbon is obtained from the desulfurization and demercaptan tower. (6) Gas phase pressurization III: The PSA tail gas is pressurized by the third raw gas compressor, cooled by cooler III, and separated by separator III to obtain a gas phase at the top of separator III and a liquid phase at the bottom of separator III; (7) Gas-liquid balance: The rich gas from the gas phase desulfurization tower, the gas phase at the top of the separator III tank, and the tail gas separated by the hydrocracking membrane are mixed to obtain sulfur-free rich gas. The sulfur-free rich gas is cooled by the shallow cooler I and then enters the separator IV for separation to obtain the gas phase at the top of the separator IV tank and the liquid phase at the bottom of the separator IV tank; (8) C1 / C2 separation: The gas phase at the top of the separator IV enters the absorption tower for C1 / C2 separation, wherein the liquid phase at the bottom of the separator III is extracted by the crude hydrocarbon pump III and mixed with the crude hydrocarbon of the desulfurization and demercaptan unit to obtain sulfur-free crude hydrocarbon, which is then cooled by the shallow cooler II and sent to the middle section of the absorption tower as the absorbent in the middle of the absorption tower. At least one of a mixture of C4, normal C4, isomeric C4 and liquefied gas is used as the absorbent at the top of the absorption tower to obtain the gas phase at the top of the absorption tower and the liquid phase at the bottom of the absorption tower. The liquid phase at the bottom of the absorption tower is returned to be mixed with the sulfur-free rich gas for gas-liquid equilibrium; (9) C3 / C4 separation: The liquid phase at the bottom of separator IV is further separated by a demethanizer and a depropanizer to obtain an ethane-rich gas product and a mixed C4 product; (10) Reabsorption: The gas phase at the top of the absorption tower is sent to the reabsorption tower to recover C3 and components above C3. The gas phase at the top of the reabsorption tower is produced as dry gas, and the liquid phase at the bottom of the reabsorption tower is returned to the stabilization tower.

2. The comprehensive recovery method of saturated light hydrocarbons according to claim 1, wherein: The operating temperature of the top of the stabilization tower is 40-60°C, and the operating pressure is 0.8-1.2 MPaG; The operating temperature of the stabilization tower reflux tank is 30-45°C; The operating temperature of the gas phase desulfurization tower is 40-45°C and the operating pressure is 2.5-4.5MPaG; The operating temperature of the desulfurization and demercaptan tower is 35-45° C., and the operating pressure is 3.0-5.0 MPaG.

3. The comprehensive recovery method of saturated light hydrocarbons according to claim 1, wherein: The outlet pressure of the first raw gas compressor is 2.5-4.5 MPaG, the crude hydrocarbon containing sulfur and heavy components is sent to the middle part of the stabilization tower, and the rich gas containing sulfur and heavy components is sent to the upper part of the stabilization tower; The outlet pressure of the second raw gas compressor is 2.5-4.5 MPaG; Another part of the liquid phase at the bottom of the stabilization tower reflux tank is sent to the upper part of the stabilization tower; Another portion of the stabilized naphtha was used as a reabsorbent (S-13).

4. The comprehensive recovery method of saturated light hydrocarbons according to claim 1, wherein: The temperature of the shallow cooler I is 15-20°C and the pressure is 2.0-4.0 MPag; The pressure of the absorption tower is 2.0-4.0 MPag.

5. The comprehensive recovery method of saturated light hydrocarbons according to claim 1, wherein: The liquid phase at the bottom of the liquid tank IV enters the demethanizer, and the gas phase at the top of the demethanizer is returned to mix with the PSA tail gas, and the gas phase is pressurized III. The liquid phase at the bottom of the demethanizer is sent to the depropanizer, and an ethane-rich gas product is obtained at the top of the tower, and a mixed C4 product is obtained at the bottom of the tower; The mixed C4 product is partially used as a C4-depleted absorbent circulating at the top of the absorption tower.

6. The comprehensive recovery method of saturated light hydrocarbons according to claim 5, wherein: The top pressure of the demethanizer is 1.0-1.5 MPag; The top pressure of the depropanizer is 1.4-2.0 MPag.

7. A comprehensive recovery device for saturated light hydrocarbons, characterized in that: The device comprises: a mixed naphtha feed pipeline, a hydrorefining sulfur-rich gas feed pipeline, a PSA tail gas feed pipeline, a hydrocracking membrane separation tail gas feed pipeline, a stabilizing tower, a first raw gas compressor, a cooler I, a liquid separator I, a second raw gas compressor, a cooler II, a liquid separator II, a crude hydrocarbon pump II, a superheater, a gas phase desulfurization tower, a desulfurization and mercaptan removal unit, a third raw gas compressor, a cooler III, a liquid separator III, a crude hydrocarbon pump III, a shallow cooler I, a shallow cooler II, a liquid separator IV, an absorption tower, a demethanizer, a depropanizer, and a reabsorption tower; Among them, the hydrofining sulfur-rich gas feed pipeline is connected to the first raw gas compressor, the cooler 1 and the separator 1 in sequence, and the separator 1 is provided with a separator 1 tank top discharge pipeline and a separator 1 tank bottom discharge pipeline; The mixed naphtha feed pipeline, the separator tank 1 top discharge pipeline and the separator tank 1 bottom discharge pipeline are connected to the stabilization tower, the stabilization tower is provided with a stabilization tower top discharge pipeline and a stabilization tower bottom discharge pipeline, the stabilization tower bottom discharge pipeline is divided into two branches, one of which is used as a mixed petroleum naphtha product discharge pipeline, the upper part of the stabilization tower is also provided with a condenser and a stabilization tower reflux tank, the stabilization tower top discharge pipeline is sequentially connected to the condenser and the stabilization tower reflux tank, the stabilization tower reflux tank is provided with a stabilization tower reflux tank top discharge pipeline and a stabilization tower reflux tank bottom discharge pipeline; The top discharge pipeline of the stabilization tower reflux tank is connected to the second raw gas compressor, cooler II and separator II in sequence, and the separator II is provided with a top discharge pipeline of the separator II tank and a bottom discharge pipeline of the separator II tank; The discharge pipeline from the top of the separator tank II is connected to the superheater and the gas phase desulfurization tower in sequence, and the gas phase desulfurization tower is provided with a gas phase desulfurization tower discharge pipeline; The discharging pipeline at the bottom of the stabilization tower reflux tank is connected to the stabilization tower reflux pump and is divided into two branches, one of which is connected to the desulfurization and sweetening tower. The discharging pipeline at the bottom of the separator tank II is connected to the crude hydrocarbon pump II and the desulfurization and sweetening tower in sequence. The desulfurization and sweetening tower is provided with a desulfurization and sweetening tower discharging pipeline. The PSA tail gas feed pipeline is connected to the third raw gas compressor, cooler III and separator III in sequence, and the separator III is provided with a separator III tank top discharge pipeline and a separator III tank bottom discharge pipeline; The top discharge pipeline of the liquid separator III, the hydrocracking membrane separation tail gas feed pipeline and the gas phase desulfurization tower discharge pipeline are merged into a sulfur-free rich gas pipeline, and then connected in sequence to the shallow cooler I and the liquid separator IV. The liquid separator IV is provided with a top discharge pipeline of the liquid separator IV and a bottom discharge pipeline of the liquid separator IV; The top discharge pipeline of the separator IV is connected to the absorption tower, the bottom discharge pipeline of the separator III is connected to the crude hydrocarbon pump III, and then merged with the discharge pipeline of the desulfurization and demercaptan tower, and then sequentially connected to the shallow cooler II and the middle part of the absorption tower. The absorption tower is provided with an absorption tower top discharge pipeline and an absorption tower bottom discharge pipeline, and the absorption tower bottom discharge pipeline merges with the sulfur-free rich gas pipeline; The bottom discharge pipeline of the separator IV tank is connected to the demethanizer and the depropanizer in sequence, and the depropanizer is provided with a depropanizer top discharge pipeline and a depropanizer bottom discharge pipeline; The top discharge pipeline of the absorption tower is connected to the reabsorption tower. The reabsorption tower is provided with a top discharge pipeline of the reabsorption tower and a bottom discharge pipeline of the reabsorption tower. The bottom discharge pipeline of the reabsorption tower is connected to the middle of the stabilization tower.

8. The comprehensive recovery device for saturated light hydrocarbons according to claim 7, wherein: The discharge line from the top of the liquid separator tank 1 is connected to the upper part of the stabilization tower, and the discharge line from the bottom of the liquid separator tank 1 is connected to the middle part of the stabilization tower; another discharge line from the bottom of the stabilization tower is connected to the reabsorption tower.

9. The comprehensive recovery device for saturated light hydrocarbons according to claim 7, wherein: The demethanizer is provided with a demethanizer top discharge pipeline and a demethanizer bottom discharge pipeline, the demethanizer top discharge pipeline is merged with the PSA tail gas feed pipeline, the demethanizer bottom discharge pipeline is connected to the depropanizer, and the propane bottom discharge pipeline is divided into two branches, one as a mixed C4 product discharge pipeline, and the other connected to the upper part of the absorption tower; Another discharge pipeline from the bottom of the stabilization tower reflux tank is connected to the upper part of the stabilization tower.

10. The comprehensive recovery device for saturated light hydrocarbons according to claim 7, wherein: The absorption tower is provided with 1 to 3 mid-section refluxes; The demethanizer tower has no condenser at the top, an intermediate reboiler at the middle of the tower, and a reboiler at the bottom of the tower.

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