A saturated light hydrocarbon comprehensive recovery method and device

Abstract

This invention belongs to the field of oil refining and chemical engineering, and relates to a method and apparatus for the comprehensive recovery of saturated light hydrocarbons. This invention has the following advantages: it centrally stabilizes the atmospheric and vacuum distillation unit, various hydrorefining units, and the naphtha-containing liquid phase after pressurization and cooling of the sulfur-containing gas phase, reducing the content of heavy components in the sulfur-rich gas and lowering the foaming risk of the gas phase desulfurization tower; it uniformly includes all plant tail gas in the recovery scope for centralized recovery, increasing the recovery range and reducing the loss of C2 and higher components; it eliminates the requirement for separate absorption stabilization systems in the atmospheric and vacuum distillation unit and hydrocracking unit, reducing the problem of secondary separation of key components; the crude hydrocarbons after desulfurization and desulfurization, and the crude hydrocarbons condensed in the outlet cooler of the third feed gas compressor, are all sent to the middle section of the absorption tower, utilizing the C3 to C5 components contained in the feedstock itself as absorbent, reducing the amount of recycled C4 and helping to reduce energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of oil refining and chemical industry, and more specifically, relates to a method and apparatus for the comprehensive recovery of saturated light hydrocarbons, and more specifically, to an apparatus and method for the recovery of saturated light hydrocarbons from the entire plant of units such as atmospheric and vacuum distillation, hydrocracking, hydrorefining, and aromatic reforming that produce rich saturated light hydrocarbons in a refinery. Background Technology

[0002] Saturated light hydrocarbons in refineries mainly originate from atmospheric and vacuum distillation unit (FCD) top gas and mixed naphtha, rich gas and crude hydrocarbons from the top of hydrogen sulfide stripping towers in various hydrocracking units, fuel gas from various hydrorefining units, disproportionation and isomerization tail gas and pre-hydrogenated fuel gas from aromatic reforming units, PSA tail gas from hydrocracking low-segment gas, PSA tail gas from reforming, and membrane separation tail gas from hydrocracking. The recovery of light hydrocarbons from these materials primarily involves recovering C3 and C4 liquefied petroleum gas (LPG) components through FCD light hydrocarbon recovery and absorption stabilization systems in various hydrocracking units. The C2 component is used as fuel gas in the dry gas. With the development of integrated refining and chemical production, further recovery of C2 components from dry gas to provide lighter ethylene feedstock for ethylene plants has gained importance. Chemical refineries with ethylene plants typically construct new C2 recovery units to recover C2 components from dry gas and send ethane-rich gas to the ethylene plant's cracking furnace as cracking feedstock, reducing the need for external ethylene feedstock purchases and further improving the refinery's economic efficiency.

[0003] The conventional process setup involves stabilizing and recovering liquefied petroleum gas (LPG) through absorption, followed by recovering C2 components using a C2 recovery unit employing shallow-cooled oil absorption technology. Since the C2 recovery unit uses C4 as the absorbent, absorbing the C2 components in the absorption tower, but the upstream absorption stabilization system pre-separates the C4 components from the C2 components, the C2 recovery unit needs to supplement with additional C4 as the absorbent to achieve C2 recovery. Therefore, a secondary separation of C2 / C4 components exists. Furthermore, in hydrocracking units, the butane stripping tower / hydrogen sulfide stripping tower separates the C4 components from the naphtha components. In the absorption stabilization system, to achieve the separation of C2 and C3 components, naphtha is used as the absorbent, and the components are mixed again in the absorption tower. To obtain the LPG product, further separation is required in the stabilization tower, resulting in a secondary separation of C4 components from naphtha. This secondary separation of key components increases separation energy consumption and the number of equipment required. Since C2, C3, and C4 components can all be used as feedstock for ethylene cracking, and C4 is also required as an absorbent for the recovery of C2 components, the necessity of setting up an absorption stabilization system is greatly reduced for chemical refineries that do not have integrated processing and utilization units for C3 and C4.

[0004] To achieve the complete recovery of saturated light hydrocarbons from all units in the plant, provide light ethylene feedstock for the ethylene unit, optimize the component separation sequence, simplify the separation process, and reduce investment and energy consumption, this invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a plant-wide saturated light hydrocarbon comprehensive recovery device and method with a reasonable component separation sequence, reduced energy consumption, and optimized equipment quantity. This method can achieve comprehensive recovery of saturated light hydrocarbons in atmospheric and vacuum distillation units, various hydrocracking units, various hydrogen refining units, and aromatic reforming units, optimize absorption tower operating conditions, and reduce energy consumption.

[0006] To achieve the above objectives, a first aspect of the present invention provides a method for the comprehensive recovery of saturated light hydrocarbons, the method comprising: (1) Gas phase pressurization I: The sulfur-rich gas from the hydrogenation refining process is compressed and pressurized by the first raw material gas compressor, cooled by the cooler I, and separated by the separator I. The top of the separator yields sulfur-rich gas containing heavy components, and the bottom of the separator yields crude hydrocarbons containing sulfur and heavy components. (2) Stabilization of naphtha throughout the plant: Mixed naphtha, rich gas containing sulfur and heavy components and crude hydrocarbon containing sulfur and heavy components 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 mixed naphtha product and the top of the tower is the top gas phase of the stabilization tower. After being condensed by 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. (3) Gas phase pressurization II: The rich gas at the top of the stabilizer tower reflux tank is sent to the second raw material gas compressor for compression and pressurization, cooled by cooler II and separated by 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 II tank passes through the superheater and is sent to the gas phase desulfurization tower, where it comes into countercurrent contact with the lean amine liquid to remove hydrogen sulfide and obtain rich gas for the gas phase desulfurization tower. (5) Crude hydrocarbon desulfurization: The liquid phase at the bottom of the stabilizer reflux tank is pressurized by the stabilizer reflux pump and divided into two parts. One part enters the desulfurization and desulfurization tower, and the liquid phase at the bottom of the separator II is pumped out by the crude hydrocarbon pump II and sent to the desulfurization and desulfurization tower. After removing hydrogen sulfide and mercaptan, crude hydrocarbons of the desulfurization and desulfurization tower are obtained. (6) Gas phase pressurization III: PSA tail gas is pressurized by the third raw material gas compressor, cooled by cooler III and separated by separator III to obtain the gas phase at the top of separator III and the liquid phase at the bottom of separator III; (7) Gas-liquid balance: The rich gas from the gas phase desulfurization tower, the top gas phase of the liquid separator III, and the tail gas from the hydrocracking membrane separation are mixed to obtain sulfur-free rich gas. After being cooled by the shallow cooler I, the sulfur-free rich gas enters the liquid separator IV for liquid separation to obtain the top gas phase of the liquid separator IV and the bottom liquid phase of the liquid separator IV. (8) C1 / C2 separation: The gas phase at the top of the separator IV enters the absorber for C1 / C2 separation. The liquid phase at the bottom of the separator III is pumped out by the crude hydrocarbon pump III and mixed with the crude hydrocarbon of the desulfurization and desulfurization tower to obtain sulfur-free crude hydrocarbon. After being cooled by the shallow cooler II, it is sent to the middle section of the absorber as the absorbent in the middle of the absorber. At least one of mixed C4, normal C4, iso-C4 and liquefied gas is used as the absorbent at the top of the absorber to obtain the gas phase at the top of the absorber and the liquid phase at the bottom of the absorber. The liquid phase at the bottom of the absorber is returned to be mixed with the sulfur-free rich gas to achieve gas-liquid balance. (9) C3 / C4 separation: The liquid phase at the bottom of the separator IV is further separated by a demethanizer and a depropanizer to obtain ethane-rich gas and mixed C4 products; (10) Reabsorption: The gas phase at the top of the absorber is sent to the reabsorption tower to recover C3 and above components. Another part of the stabilized naphtha is used as the reabsorbent. The gas phase at the top of the reabsorption tower is extracted as dry gas, and the liquid phase at the bottom of the reabsorption tower is returned to the stabilizer.

[0007] In this invention, the mixed naphtha comes from various hydrogen refining units, atmospheric and vacuum distillation units, and the gas and liquid phases of the hydrogen-refined sulfur-containing fuel gas after passing through a second feed gas compressor and cooling separation, thereby reducing the C5 and above components in the sulfur-containing fuel gas and lowering the risk of foaming in the gas phase desulfurization tower.

[0008] According to the present invention, gas phase desulfurization adopts medium and high pressure desulfurization, reduces the amount of lean amine solution and the diameter of the desulfurization tower, and a sulfur-rich gas superheater is installed in front of the gas phase desulfurization tower.

[0009] According to the present invention, the crude hydrocarbon in the stabilizer reflux tank is pressurized by the reflux pump and sent to the desulfurization and desulfurization stage after the subcooling is increased. After the gas phase in the stabilizer reflux tank is pressurized by the first raw material gas compressor, cooled by the cooler, and separated by the liquid separator, a portion of the C3 / C4 components in the gas phase will condense into the liquid phase, reducing the content of heavy components in the gas phase and reducing the risk of foaming in the gas phase desulfurization tower. The liquid phase is pressurized by the pump and sent to the desulfurization and desulfurization stage after the subcooling is increased.

[0010] According to the present invention, the tail gas of the low-saturation PSA and the tail gas of the reformed hydrogen are pressurized by the third raw material gas compressor, cooled by the cooler, and separated by the liquid separator. The gas phase and the gas phase desulfurization 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 hydrocarbon after desulfurization and desulfurization to be cooled to 15°C~20°C by the shallow cooler before being sent to the middle section of the absorption tower.

[0011] According to the present invention, the cooled raw material gas and the crude hydrocarbon at the bottom of the absorption tower are passed together through a shallow cooler and cooled to 15°C~20°C. During the mixed cooling process, the crude hydrocarbon at the bottom of the absorption tower will further absorb the C2 and above components in the raw material, reducing the load on the absorption tower. After mixed cooling, the gas phase enters the absorption tower again through a separator, and the liquid phase is sent to the demethanizer.

[0012] According to the present invention, the top of the absorption tower uses lean C4 as the absorbent and the middle part of the tower uses crude hydrocarbons of the raw material as the absorbent, so as to absorb C2 and above components in the raw gas and achieve C1 / C2 separation.

[0013] According to the present invention, the intermediate reboiler and the bottom reboiler of the demethanizer use the lean C4 at the bottom of the depropanizer as the heat source, and do not require the consumption of steam. The top of the tower does not have a cooling reflux, and the gas is directly returned to the inlet of the third feed gas compressor.

[0014] According to the present invention, the bottom of the propane dehydrogenator is C4 lean. Part of it is sent to the top of the absorber as a circulating absorbent after passing through the intermediate reboiler and bottom reboiler of the demethanizer. Part of it is sent out of the unit. The top of the tower is a mixture of C2, C3 and C4 components. C3 and C4 are no longer strictly separated. The top gas is sent to the ethylene unit for cracking.

[0015] According to the present invention, the dry gas at the top of the absorber is sent to the reabsorption tower, and the stabilized naphtha at the bottom of the stabilizer tower is used as the reabsorbent to recover the entrained C4 absorbent, reduce absorbent loss, and the mixed naphtha at the bottom of the tower is returned to the stabilizer tower.

[0016] According to the present invention, preferably, the operating temperature at the top of the stabilization tower is 40~60℃ and the operating pressure is 0.8~1.2MPaG.

[0017] According to the present invention, preferably, the operating temperature of the stabilizer reflux tank is 30~45°C.

[0018] According to the present invention, preferably, the operating temperature of the gas phase desulfurization tower is 40~45℃ and the operating pressure is 2.5~4.5MPaG.

[0019] According to the present invention, preferably, the operating temperature of the desulfurization and desulfurization tower is 35~45℃ and the operating pressure is 3.0~5.0MPaG.

[0020] According to the present invention, preferably, the outlet pressure of the first raw material gas compressor is 2.5~4.5 MPaG, the sulfur-containing and heavy component crude hydrocarbon is sent to the middle part of the stabilizer, and the sulfur-containing and heavy component rich gas is sent to the upper part of the stabilizer.

[0021] According to the present invention, preferably, the outlet pressure of the second raw material gas compressor is 2.5~4.5 MPaG.

[0022] According to the present invention, preferably, another portion of the liquid phase at the bottom of the stabilizer reflux tank is sent to the upper part of the stabilizer.

[0023] According to the present invention, preferably, another portion of stabilized naphtha is used as a reabsorbent.

[0024] 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.

[0025] According to the present invention, preferably, the pressure of the absorption tower is 2.0~4.0 MPaG.

[0026] According to the present invention, preferably, the liquid phase at the bottom of the liquid tank IV enters the demethanizer, the resulting gas phase at the top of the demethanizer is returned and mixed with the PSA tail gas for gas phase pressurization III, and the resulting liquid phase at the bottom of the demethanizer is sent to the depropanizer, where ethane-rich gas product is obtained at the top of the tower and mixed C4 product is obtained at the bottom of the tower.

[0027] According to the present invention, preferably, the mixed C4 product portion is used as a C4-lean absorbent circulating at the top of the absorber tower.

[0028] According to the present invention, preferably, the top pressure of the demethanizer is 1.0-1.5 MPaG.

[0029] According to the present invention, preferably, the top pressure of the propane removal column is 1.4~2.0 MPaG.

[0030] A second aspect of the present invention provides a saturated light hydrocarbon integrated recovery device, the device comprising: 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 stabilization tower, a first feed gas compressor, a cooler I, a liquid separator I, a second feed gas compressor, a cooler II, a liquid separator II, a crude hydrocarbon pump II, a superheater, a gas phase desulfurization tower, a desulfurization and desulfurization tower, a third feed 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 tower, a depropanizer tower, and a reabsorption tower; The hydrorefining sulfur-rich gas feed pipeline is connected in sequence to the first raw material gas compressor, cooler I and liquid separator I. The liquid separator I is equipped with a top discharge pipeline and a bottom discharge pipeline. The mixed naphtha feed pipeline, the top discharge pipeline of separator I, and the bottom discharge pipeline of separator I are connected to the stabilizer. The stabilizer is equipped with a top discharge pipeline and a bottom discharge pipeline. The bottom discharge pipeline is divided into two branches, one of which serves as the mixed naphtha product discharge pipeline. The upper part of the stabilizer is also equipped with a condenser and a stabilizer reflux tank. The top discharge pipeline of the stabilizer is connected to the condenser and the stabilizer reflux tank in sequence. The stabilizer reflux tank is equipped with a top discharge pipeline and a bottom discharge pipeline. The top discharge pipeline of the stabilizer tower reflux tank is connected in sequence to the second raw material gas compressor, cooler II and liquid separator II. The liquid separator II is equipped with a top discharge pipeline and a bottom discharge pipeline. The top discharge pipeline of the liquid separator II is connected in sequence to the superheater and the gas phase desulfurization tower, and the gas phase desulfurization tower is equipped with a gas phase desulfurization tower discharge pipeline. The bottom discharge pipeline of the stabilizer tower reflux tank is connected to the stabilizer tower reflux pump and then splits into two branches. One branch is connected to the desulfurization and desulfurization tower. The bottom discharge pipeline of the separator II is connected to the crude hydrocarbon pump II and the desulfurization and desulfurization tower in sequence. The desulfurization and desulfurization tower is equipped with a desulfurization and desulfurization tower discharge pipeline. The PSA exhaust gas feed line is connected in sequence to the third raw material gas compressor, cooler III and liquid separator III. The liquid separator III is equipped with a top discharge line and a bottom discharge line. The top discharge pipeline of the liquid separator III, the feed pipeline of the hydrocracking membrane separation tail gas and the discharge pipeline of the gas phase desulfurization tower are sulfur-free rich gas pipelines, which are then connected to the shallow cooler I and the liquid separator IV in sequence. The liquid separator IV is equipped 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 merges with the discharge pipeline of the desulfurization and desulfurization tower. It is then connected to the shallow cooler II and the middle part of the absorption tower in sequence. The absorption tower is equipped with a top discharge pipeline and a bottom discharge pipeline. The bottom discharge pipeline of the absorption tower merges with the sulfur-free rich gas pipeline. The bottom discharge pipeline of the separator IV is connected in sequence to the demethanizer and the depropanizer. The depropanizer is equipped with a top discharge pipeline and a bottom discharge pipeline. The top discharge pipeline of the absorption tower is connected to the reabsorption tower. The reabsorption tower is equipped with a top discharge pipeline and a bottom discharge pipeline. The bottom discharge pipeline of the reabsorption tower is connected to the middle of the stabilization tower.

[0031] According to the present invention, preferably, the top discharge pipeline of the separator I is connected to the upper part of the stabilizer, and the bottom discharge pipeline of the separator I is connected to the middle part of the stabilizer; the bottom discharge pipeline of the other stabilizer is connected to the reabsorption tower.

[0032] According to the present invention, preferably, the demethanizer is provided with a top discharge pipeline and a bottom discharge pipeline. The top discharge pipeline of the demethanizer merges with the PSA tail gas feed pipeline. The bottom discharge pipeline of the demethanizer is connected to the depropanizer. The bottom discharge pipeline of the propanizer is divided into two branches, one of which serves as the discharge pipeline for mixed C4 products, and the other is connected to the upper part of the absorption tower.

[0033] According to the present invention, preferably, the bottom discharge pipeline of another stabilizer tower reflux tank is connected to the upper part of the stabilizer tower.

[0034] According to the present invention, preferably, the absorption tower is provided with 1 to 3 intermediate reflux sections; the demethanizer is not provided at the top of the tower, an intermediate reboiler is provided in the middle of the tower, and a reboiler is provided at the bottom of the tower.

[0035] Compared with the prior art, the present invention has the following advantages: (1) In this invention, the atmospheric and vacuum distillation unit, each hydrorefining unit and the naphtha-containing liquid phase after the sulfur-containing gas phase is pressurized and cooled are concentrated and stabilized, reducing the content of heavy components in the sulfur-rich gas and reducing the foaming risk of the gas phase desulfurization tower.

[0036] (2) In this invention, the sulfur-containing fuel gas from hydrorefining, the tail gas of low-fraction PSA from hydrorefining, the tail gas of reformed hydrogen PSA, the disproportionated fuel gas, and the tail gas of hydrocracking membrane separation are all included in the recovery scope for centralized recovery, which improves the recovery scope and reduces the loss of C2 and above components.

[0037] (3) In this invention, it is no longer required that the atmospheric and vacuum distillation unit and the hydrocracking unit be equipped with separate absorption stabilization systems, which reduces the problem of secondary separation of key components.

[0038] (4) In this invention, the crude hydrocarbons after desulfurization and desulfurization, and the crude hydrocarbons condensed by the outlet cooler of the third raw material gas compressor are all sent to the middle section of the absorption tower. The C3 to C5 components contained in the raw material itself are used as absorbents, which reduces the amount of circulating C4 and helps to reduce energy consumption.

[0039] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0040] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the invention.

[0041] Figure 1 The process flow diagram of the comprehensive recovery of saturated light hydrocarbons in the whole plant in Embodiment 1 of the present invention is shown.

[0042] Explanation of reference numerals in the attached figures: 1. Stabilizer; 2. Stabilizer reflux tank; 3. Stabilizer reflux pump; 4. Second feed gas compressor; 5. Cooler II; 6. Separator II; 7. Crude hydrocarbon pump II; 8. Superheater; 9. Gas phase desulfurization tower; 10. First feed gas compressor; 11. Cooler I; 12. Separator I; 13. Third feed gas compressor; 14. Cooler III; 15. Separator III; 16. Crude hydrocarbon pump III; 17. Shallow cooler I; 18. Shallow cooler II; 19. Desulfurization and desulfurization tower; 23. Separator IV; 24. Absorber; 25. Demethanizer; 26. Depropanizer; 27. Reabsorption tower; S-1, Mixed naphtha; S-2, Rich gas containing sulfur and heavy components; S-3, Crude hydrocarbons containing sulfur and heavy components; S-4, Hydrorefined rich gas containing sulfur; S-5, PSA tail gas; S-6, Rich gas without sulfur; S-7, Crude hydrocarbons without sulfur; S-9, Circulating lean C4 absorbent; S-10, Mixed C4 products; S-11, Rich ethane gas products; S-12, Dry gas; S-13, Mixed naphtha absorbent; S-14, Mixed naphtha products; S-15, Hydrocracking membrane separation tail gas. Detailed Implementation

[0043] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0044] Example 1

[0045] The plant's saturated light hydrocarbon integrated recovery unit includes: 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 stabilizer tower 1, a first feed gas compressor 10, a cooler I 11, a liquid separator I 12, a second feed gas compressor 4, a cooler II 5, a liquid separator II 6, a crude hydrocarbon pump II 7, a superheater 8, a gas phase desulfurization tower 9, a desulfurization and desulfurization tower 19, a third feed gas compressor 13, a cooler III 14, a liquid separator III 15, a crude hydrocarbon pump III 16, a shallow cooler I 17, a shallow cooler II 18, a liquid separator IV 23, an absorption tower 24, a demethanizer tower 25, a depropanizer tower 26, and a reabsorption tower 27. The hydrogenation refining sulfur-rich gas feed pipeline is sequentially connected to the first raw material gas compressor 10, cooler I 11 and liquid separator I 12. The liquid separator I 12 is equipped with a top discharge pipeline and a bottom discharge pipeline. The mixed naphtha feed line is connected to the stabilizer tower. The top discharge line of the separator I is connected to the upper part of the stabilizer tower 1. The bottom discharge line of the separator I is connected to the middle part of the stabilizer tower. The stabilizer tower is equipped with a top discharge line and a bottom discharge line. The bottom discharge line is divided into two branches, one of which serves as the mixed naphtha product discharge line, and the other is connected to the reabsorption tower. The upper part of the stabilizer tower is also equipped with a condenser and a stabilizer tower reflux tank. The top discharge line of the stabilizer tower is connected to the condenser and the stabilizer tower reflux tank in sequence. The stabilizer tower reflux tank is equipped with a top discharge line and a bottom discharge line. The top discharge pipeline of the stabilizer tower reflux tank is connected in sequence to the second raw material gas compressor 4, cooler II 5 and liquid separator II 6. The liquid separator II 6 is equipped with a top discharge pipeline and a bottom discharge pipeline. The top discharge pipeline of the liquid separator II is connected in sequence to the superheater 8 and the gas phase desulfurization tower 9. The gas phase desulfurization tower is equipped with a gas phase desulfurization tower discharge pipeline. The bottom discharge pipeline of the stabilizer tower reflux tank is connected to the stabilizer tower reflux pump 3 and then splits into two branches. One branch is connected to the desulfurization and desulfurization tower 19. The bottom discharge pipeline of the separator II is connected to the crude hydrocarbon pump II and the desulfurization and desulfurization tower 19 in sequence. The desulfurization and desulfurization tower 19 is equipped with a desulfurization and desulfurization tower discharge pipeline. The PSA exhaust gas feed line is connected in sequence to the third raw material gas compressor 13, cooler III 14 and liquid separator III 15. The liquid separator III 15 is provided with a liquid separator III top discharge line and a liquid separator III bottom discharge line. The top discharge pipeline of the liquid separator III, the feed pipeline of the hydrocracking membrane separation tail gas and the discharge pipeline of the gas phase desulfurization tower are combined into a sulfur-free rich gas pipeline, which is then connected to the shallow cooler I 17 and the liquid separator IV 23 in sequence. The liquid separator IV 23 is equipped with the top discharge pipeline of the liquid separator IV and the bottom discharge pipeline of the liquid separator IV. The top discharge pipeline of the separator IV is connected to the absorption tower 24. The bottom discharge pipeline of the separator III is connected to the crude hydrocarbon pump III and then merges with the discharge pipeline of the desulfurization and desulfurization tower. It is then connected to the shallow cooler II 18 and the middle part of the absorption tower in sequence. The absorption tower is equipped with a top discharge pipeline and a bottom discharge pipeline. The bottom discharge pipeline of the absorption tower merges with the sulfur-free rich gas pipeline. The bottom discharge pipeline of the separator IV is connected to the demethanizer 25. The demethanizer 25 is equipped with a top discharge pipeline and a bottom discharge pipeline. The top discharge pipeline of the demethanizer merges with the PSA tail gas feed pipeline. The bottom discharge pipeline of the demethanizer is connected to the propane dehydrogenator 26. The bottom discharge pipeline of the propane dehydrogenator is divided into two branches, one of which serves as the discharge pipeline for mixed C4 products, and the other is connected to the upper part of the absorption tower. The top discharge pipeline of the absorption tower is connected to the reabsorption tower 27. The reabsorption tower 27 is equipped with a top discharge pipeline and a bottom discharge pipeline. The bottom discharge pipeline of the reabsorption tower is connected to the middle of the stabilization tower.

[0046] The process flow diagram for the comprehensive recovery of saturated light hydrocarbons throughout the plant using the above-mentioned equipment is as follows: Figure 1 As shown: (1) Gas phase pressurization I: The sulfur-rich gas refined by hydrogenation is compressed and pressurized by the first raw material gas compressor, cooled by the cooler I and separated by the separator I. The top of the separator is rich gas containing sulfur and heavy components, and the bottom of the separator is crude hydrocarbon containing sulfur and heavy components. The outlet pressure of the first raw material gas compressor is 3.0 MPaG.

[0047] (2) Stabilization of naphtha throughout the plant: Mixed naphtha, rich gas containing sulfur and heavy components and crude hydrocarbon containing sulfur and heavy components 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 mixed naphtha product, and the top of the tower is the top gas phase of the stabilization tower. After being condensed by the condenser, it is sent to the stabilization tower reflux tank to obtain the top gas phase of the stabilization tower reflux tank and the bottom liquid phase of the stabilization tower reflux tank. The operating pressure of the stabilization tower is 1.0 MPaG, the top temperature of the tower is 45℃, and the outlet pressure of the stabilization tower reflux pump is 3.5 MPaG.

[0048] (3) Gas phase pressure boosting II: The rich gas at the top of the stabilizer tower reflux tank is sent to the second raw material gas compressor for compression and pressure boosting, the cooler II for cooling, and the liquid separator II for liquid separation, resulting in 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 material gas compressor is 3.0 MPaG.

[0049] (4) Rich gas desulfurization: The rich gas at the top of the liquid separator II passes through the superheater and is sent to the gas phase desulfurization tower, where it comes into countercurrent contact with the lean amine liquid to remove hydrogen sulfide and obtain rich gas for the gas phase desulfurization tower; the superheater outlet temperature is 43℃ ​​and the superheat is 3℃.

[0050] (5) Crude hydrocarbon desulfurization: The liquid phase at the bottom of the stabilizer reflux tank is pressurized by the stabilizer reflux pump and divided into two parts. One part enters the desulfurization and desulfurization tower, and the liquid phase at the bottom of the separator II is pumped out by the crude hydrocarbon pump II and sent to the desulfurization and desulfurization tower. After removing hydrogen sulfide and mercaptan, crude hydrocarbons of the desulfurization and desulfurization tower are obtained. (6) Gas phase pressurization III: PSA tail gas is pressurized by the third raw material gas compressor, cooled by cooler III and separated by separator III to obtain the gas phase at the top of separator III and the 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 liquid separator III, and the tail gas from the hydrocracking membrane separation are mixed to obtain sulfur-free rich gas. After being cooled by the shallow cooler I, the sulfur-free rich gas enters the liquid separator IV for liquid separation to obtain the gas phase at the top of the liquid separator IV and the liquid phase at the bottom of the liquid separator IV. The outlet temperature of the shallow cooler is 15℃.

[0051] (8) C1 / C2 separation: The gas phase at the top of the separator IV enters the absorber for C1 / C2 separation. The liquid phase at the bottom of the separator III is pumped out by the crude hydrocarbon pump III and mixed with the crude hydrocarbon of the desulfurization and desulfurization tower to obtain sulfur-free crude hydrocarbon. After being cooled by the shallow cooler II, it is sent to the middle section of the absorber as the absorbent in the middle of the absorber. At least one of mixed C4, normal C4, iso-C4 and liquefied gas is used as the absorbent at the top of the absorber to obtain the gas phase at the top of the absorber and the liquid phase at the bottom of the absorber. The liquid phase at the bottom of the absorber is returned to be mixed with the sulfur-free rich gas to achieve gas-liquid balance. (9) C3 / C4 separation: 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 be mixed with the PSA tail gas for gas phase pressurization III. The liquid phase at the bottom of the demethanizer is sent to the depropanizer. Ethane-rich gas product is obtained at the top of the tower, and mixed C4 product is obtained at the bottom of the tower. A portion of the product is used as a C4-lean absorbent for the top circulation of the absorber. The pressure at the top of the demethanizer is 1.0-1.5 MPaG; the pressure at the top of the depropanizer is 1.4-2.0 MPaG.

[0052] (10) Reabsorption: The gas phase at the top of the absorber is sent to the reabsorption tower to recover C3 and above components. Another part of the stabilized naphtha is used as the reabsorbent. The gas phase at the top of the reabsorption tower is extracted as dry gas, and the liquid phase at the bottom of the reabsorption tower is returned to the stabilizer.

[0053] The composition and properties of the dry gas, ethane-rich gas, and mixed C4 gas separated from light hydrocarbons by the above method are shown in Tables 1-3.

[0054] Table 1 Properties of dry gas

[0055] Table 2 Properties of Ethane-Rich Gas

[0056] Table 3 Properties of mixed C4

[0057] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they 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 method for comprehensive recovery of saturated light hydrocarbons, characterized in that, The recycling method includes: (1) Gas phase pressurization I: The sulfur-rich gas from the hydrogenation refining process is compressed and pressurized by the first raw material gas compressor, cooled by the cooler I, and separated by the separator I. The top of the separator yields sulfur-rich gas containing heavy components, and the bottom of the separator yields crude hydrocarbons containing sulfur and heavy components. (2) Stabilization of naphtha throughout the plant: Mixed naphtha, rich gas containing sulfur and heavy components and crude hydrocarbon containing sulfur and heavy components 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 mixed naphtha product and the top of the tower is the top gas phase of the stabilization tower. After being condensed by 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. (3) Gas phase pressurization II: The rich gas at the top of the stabilizer tower reflux tank is sent to the second raw material gas compressor for compression and pressurization, cooled by cooler II and separated by 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 II tank passes through the superheater and is sent to the gas phase desulfurization tower, where it comes into countercurrent contact with the lean amine liquid to remove hydrogen sulfide and obtain rich gas for the gas phase desulfurization tower. (5) Crude hydrocarbon desulfurization: The liquid phase at the bottom of the stabilizer reflux tank is pressurized by the stabilizer reflux pump and divided into two parts. One part enters the desulfurization and desulfurization tower, and the liquid phase at the bottom of the separator II is pumped out by the crude hydrocarbon pump II and sent to the desulfurization and desulfurization tower. After removing hydrogen sulfide and mercaptan, crude hydrocarbons of the desulfurization and desulfurization tower are obtained. (6) Gas phase pressurization III: PSA tail gas is pressurized by the third raw material gas compressor, cooled by cooler III and separated by separator III to obtain the gas phase at the top of separator III and the liquid phase at the bottom of separator III; (7) Gas-liquid balance: The rich gas from the gas phase desulfurization tower, the top gas phase of the liquid separator III, and the tail gas from the hydrocracking membrane separation are mixed to obtain sulfur-free rich gas. After being cooled by the shallow cooler I, the sulfur-free rich gas enters the liquid separator IV for liquid separation to obtain the top gas phase of the liquid separator IV and the bottom liquid phase of the liquid separator IV. (8) C1 / C2 separation: The gas phase at the top of the separator IV enters the absorber for C1 / C2 separation. The liquid phase at the bottom of the separator III is pumped out by the crude hydrocarbon pump III and mixed with the crude hydrocarbon of the desulfurization and desulfurization tower to obtain sulfur-free crude hydrocarbon. After being cooled by the shallow cooler II, it is sent to the middle section of the absorber as the absorbent in the middle of the absorber. At least one of mixed C4, normal C4, iso-C4 and liquefied gas is used as the absorbent at the top of the absorber to obtain the gas phase at the top of the absorber and the liquid phase at the bottom of the absorber. The liquid phase at the bottom of the absorber is returned to be mixed with the sulfur-free rich gas to achieve gas-liquid balance. (9) C3 / C4 separation: The liquid phase at the bottom of the separator IV is further separated by a demethanizer and a depropanizer to obtain ethane-rich gas and mixed C4 products; (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 extracted as dry gas, and the liquid phase at the bottom of the reabsorption tower is returned to the stabilizer.

2. The method for comprehensive recovery of saturated light hydrocarbons according to claim 1, wherein, The operating temperature at the top of the stabilizer tower is 40~60℃, and the operating pressure is 0.8~1.2MPaG; The operating temperature of the stabilizer reflux tank is 30~45℃; The operating temperature of the gas phase desulfurization tower is 40~45℃, and the operating pressure is 2.5~4.5MPaG; The operating temperature of the desulfurization and desulfurization tower is 35~45℃, and the operating pressure is 3.0~5.0MPaG.

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

4. The method for comprehensive recovery of saturated light hydrocarbons according to claim 1, wherein, The temperature of the shallow cooler I is 15~20℃, and the pressure is 2.0~4.0MPaG; The pressure of the absorption tower is 2.0~4.0 MPaG.

5. The method for comprehensive recovery of saturated light hydrocarbons according to claim 1, wherein, The liquid phase at the bottom of the liquid tank IV enters the demethanizer. The gas phase at the top of the demethanizer is returned and mixed with the PSA tail gas for gas phase pressurization III. The liquid phase at the bottom of the demethanizer is sent to the depropanizer. The top of the tower yields ethane-rich gas product, and the bottom of the tower yields mixed C4 product. The mixed C4 product portion is used as a C4-lean absorbent circulating at the top of the absorber tower.

6. The method for comprehensive recovery 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 propane removal column is 1.4~2.0 MPaG.

7. A saturated light hydrocarbon comprehensive recovery device, characterized in that, The unit includes: 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 stabilizer tower, a first feed gas compressor, a cooler I, a separator I, a second feed gas compressor, a cooler II, a separator II, a crude hydrocarbon pump II, a superheater, a gas phase desulfurization tower, a desulfurization and desulfurization tower, a third feed gas compressor, a cooler III, a separator III, a crude hydrocarbon pump III, a shallow cooler I, a shallow cooler II, a separator IV, an absorption tower, a demethanizer tower, a depropanizer tower, and a reabsorption tower; The hydrorefining sulfur-rich gas feed pipeline is connected in sequence to the first raw material gas compressor, cooler I and liquid separator I. The liquid separator I is equipped with a top discharge pipeline and a bottom discharge pipeline. The mixed naphtha feed pipeline, the top discharge pipeline of separator I, and the bottom discharge pipeline of separator I are connected to the stabilizer. The stabilizer is equipped with a top discharge pipeline and a bottom discharge pipeline. The bottom discharge pipeline is divided into two branches, one of which serves as the mixed naphtha product discharge pipeline. The upper part of the stabilizer is also equipped with a condenser and a stabilizer reflux tank. The top discharge pipeline of the stabilizer is connected to the condenser and the stabilizer reflux tank in sequence. The stabilizer reflux tank is equipped with a top discharge pipeline and a bottom discharge pipeline. The top discharge pipeline of the stabilizer tower reflux tank is connected in sequence to the second raw material gas compressor, cooler II and liquid separator II. The liquid separator II is equipped with a top discharge pipeline and a bottom discharge pipeline. The top discharge pipeline of the liquid separator II is connected in sequence to the superheater and the gas phase desulfurization tower, and the gas phase desulfurization tower is equipped with a gas phase desulfurization tower discharge pipeline. The bottom discharge pipeline of the stabilizer tower reflux tank is connected to the stabilizer tower reflux pump and then splits into two branches. One branch is connected to the desulfurization and desulfurization tower. The bottom discharge pipeline of the separator II is connected to the crude hydrocarbon pump II and the desulfurization and desulfurization tower in sequence. The desulfurization and desulfurization tower is equipped with a desulfurization and desulfurization tower discharge pipeline. The PSA exhaust gas feed line is connected in sequence to the third raw material gas compressor, cooler III and liquid separator III. The liquid separator III is equipped with a top discharge line and a bottom discharge line. The top discharge pipeline of the liquid separator III, the feed pipeline of the hydrocracking membrane separation tail gas, and the discharge pipeline of the gas phase desulfurization tower are combined into a sulfur-free rich gas pipeline, which is then connected to the shallow cooler I and the liquid separator IV in sequence. The liquid separator IV is equipped 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 merges with the discharge pipeline of the desulfurization and desulfurization tower. It is then connected to the shallow cooler II and the middle part of the absorption tower in sequence. The absorption tower is equipped with a top discharge pipeline and a bottom discharge pipeline. The bottom discharge pipeline of the absorption tower merges with the sulfur-free rich gas pipeline. The bottom discharge pipeline of the separator IV is connected in sequence to the demethanizer and the depropanizer. The depropanizer is equipped with a top discharge pipeline and a bottom discharge pipeline. The top discharge pipeline of the absorption tower is connected to the reabsorption tower. The reabsorption tower is equipped with a top discharge pipeline and a bottom discharge pipeline. The bottom discharge pipeline of the reabsorption tower is connected to the middle of the stabilization tower.

8. The saturated light hydrocarbon comprehensive recovery device according to claim 7, wherein, The top discharge line of the separator I is connected to the upper part of the stabilizer tower, and the bottom discharge line of the separator I is connected to the middle of the stabilizer tower; the bottom discharge line of the other stabilizer tower is connected to the reabsorption tower.

9. The saturated light hydrocarbon comprehensive recovery device according to claim 7, wherein, The demethanizer is equipped with a top discharge pipeline and a bottom discharge pipeline. The top discharge pipeline of the demethanizer merges with the PSA tail gas feed pipeline. The bottom discharge pipeline of the demethanizer is connected to the depropanizer. The bottom discharge pipeline of the propanizer is divided into two branches, one of which serves as the discharge pipeline for mixed C4 products, and the other is connected to the upper part of the absorption tower. The bottom discharge pipeline of the other stabilizer tower reflux tank is connected to the upper part of the stabilizer tower.

10. The saturated light hydrocarbon comprehensive recovery device according to claim 7, wherein, The absorption tower is equipped with 1 to 3 intermediate reflux sections; The demethanizing tower has no condenser at the top, an intermediate reboiler in the middle, and a reboiler at the bottom.

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