Device and method for separating hydrogen sulfide by using LNG (Liquefied Natural Gas) cold energy

Abstract

The invention provides a device for separating hydrogen sulfide through LNG cold energy. The device comprises an LNG vaporizer, a first refrigerant assembly, an NG heat exchanger, a second refrigerant assembly, a first heat exchanger, a second heat exchanger, a first gas-liquid separation device and a second gas-liquid separation device. Wherein the LNG vaporizer for inputting LNG is communicated with the first refrigerant assembly, the NG heat exchanger and the first heat exchanger; the NG heat exchanger further communicates with a second refrigerant assembly and a second heat exchanger for inputting feed gas; the first heat exchanger further communicates with the first gas-liquid separation device, the first refrigerant assembly and the second gas-liquid separation device. The second heat exchanger further communicates with the second refrigerant assembly and the second gas-liquid separation device. According to the system, LNG cold energy utilization and hydrogen sulfide separation are coupled together, useless energy of an LNG receiving station is utilized, meanwhile, the problem of high energy consumption of an amine liquid system is avoided, and the system is very suitable for refinery enterprises close to the LNG receiving station.

Description

Technical Field

[0001] The present invention belongs to the technical field of using LNG cold energy for gas separation, and specifically relates to a device for using LNG cold energy for hydrogen sulfide separation, which is particularly suitable for removing hydrogen sulfide from dry gas, liquefied gas and gas produced by hydrocracking, coking, hydrofining and other devices in oil refineries. In addition, the present invention also relates to a method for using LNG cold energy for hydrogen sulfide separation. Background Art

[0002] LNG (liquefied natural gas) is a liquid obtained by compressing and cooling NG (natural gas) to -161.5℃. Its main component is methane, and its volume is about 1 / 625 of the volume of the same amount of gaseous NG, which is convenient for transportation and storage. After LNG is transported to the destination by LNG ship, it needs to be gasified into NG in the LNG receiving station before it can be used in the next step. Each ton of LNG gasification produces about 240KWh of cold energy. If this part of energy can be used reasonably, it will generate considerable economic benefits. At present, LNG cold energy is mainly used in power generation, air separation and seawater desalination. LNG power generation is limited by the unstable ship schedule, and the resulting electricity cannot be connected to the power grid, and can only be stored in energy storage devices; air separation first liquefies the air, and then uses the different boiling points of various substances to separate them in the distillation tower; seawater desalination uses LNG cold energy to freeze seawater, and then melts it after solid-liquid separation to obtain fresh water. However, the above applications are relatively unprofitable because they require new equipment and are limited by the acceptance capacity of LNG receiving stations.

[0003] H2S acid gas is widely present in natural gas, refinery gas and raw gas. Removing H2S gas is of great significance for hydrogen production, gas purification and environmental safety. There are two main methods for removing H2S: dry method and wet method. Dry desulfurization is a method that utilizes the reducibility and flammability of H2S to remove hydrogen sulfide or directly burn it with a solid oxidant or absorbent to oxidize hydrogen sulfide into elemental sulfur or sulfur oxides for removal. It mainly includes Claus method, iron method, iron oxide method, zinc oxide method, molecular sieve method, etc. Dry desulfurization is suitable for the treatment of low-sulfur gas with high desulfurization efficiency, but the adsorbent has low adsorption capacity and low selectivity. Wet desulfurization is a method of removing H2S using a solution, which is mainly divided into absorption method and wet oxidation method. The absorption method refers to releasing the absorbed H2S through the regeneration system and sending it to the Claus device to become elemental sulfur. The wet oxidation method refers to using a solution to absorb H2S and convert it into elemental sulfur, which is then separated and recycled. At present, the most widely used industrial desulfurization method at home and abroad is the wet flue gas desulfurization using alcohol amine solvents. The solvent used is methyl diethanolamine solution (MDEA), which has the advantages of large H2S absorption load and lower regeneration energy compared to traditional DGA. However, since the MDEA solution needs to be regenerated, the energy consumption of the device of this technology is extremely high, and it is urgent to develop new processes to separate hydrogen sulfide. Summary of the invention

[0004] The purpose of the present invention is to solve the above-mentioned problems existing in the prior art and provide a device for separating hydrogen sulfide in chemical plants using LNG cold energy, which is suitable for removing hydrogen sulfide from dry gas, liquefied gas and gas produced by hydrocracking, coking, hydrofining and other devices in refineries to meet the requirements of environmental emissions and subsequent processes. At present, the liquefied gas and dry gas produced by refineries mainly contain C2, C3, C4 and other components, and the hydrogen sulfide concentration is about 20000mg / Nm 3 Since the boiling points of each component are ethylene -103.9℃, ethane -88.6℃, propylene -47.7℃, propane -42.1℃, butane -0.5℃, isobutane -10.5℃, and the boiling point of hydrogen sulfide is -60.4℃, the LNG cold energy can be used to cool the liquefied gas to below -70℃, and then the liquefied components can be distilled to separate hydrogen sulfide, C3 and C4 components.

[0005] The present invention is achieved through the following technical solutions:

[0006] One of the objects of the present invention is to provide a device for separating hydrogen sulfide using LNG cold energy, comprising an LNG vaporizer, a first refrigerant component, an NG heat exchanger, a second refrigerant component, a first heat exchanger, a second heat exchanger, a first gas-liquid separation device and a second gas-liquid separation device; wherein the LNG vaporizer for inputting LNG is connected to the first refrigerant component, the NG heat exchanger and the first heat exchanger; the NG heat exchanger is also connected to the second refrigerant component and the second heat exchanger for inputting raw gas; the first heat exchanger is also connected to the first gas-liquid separation device, the first refrigerant component and the second gas-liquid separation device; the second heat exchanger is also connected to the second refrigerant component and the second gas-liquid separation device.

[0007] In a preferred embodiment of the present invention, the first refrigerant assembly includes a first refrigerant delivery pump, a first refrigerant storage tank and a first refrigerant pipeline; and / or,

[0008] The second refrigerant assembly includes a second refrigerant delivery pump, a second refrigerant storage tank and a second refrigerant pipeline.

[0009] In a preferred embodiment of the present invention,

[0010] The LNG vaporizer, the NG heat exchanger, the first heat exchanger and the second heat exchanger are respectively provided with a first inlet, a second inlet, a first outlet and a second outlet; the first gas-liquid separation device and the second gas-liquid separation device are respectively provided with a material inlet, a gas phase outlet and a liquid phase outlet; wherein:

[0011] The first inlet of the LNG vaporizer is used to input LNG, the second inlet is connected to the first outlet of the first heat exchanger, the first outlet is connected to the inlet of the first refrigerant storage tank, and the second outlet is connected to the first inlet of the NG heat exchanger;

[0012] The second inlet of the NG heat exchanger is connected to the first outlet of the second heat exchanger, the first outlet is connected to the inlet of the second refrigerant storage tank, and the second outlet outputs NG;

[0013] The first inlet of the second heat exchanger is used to input raw gas, the second inlet is connected to the outlet of the second refrigerant storage tank, and the second outlet is connected to the material inlet of the second gas-liquid separation device;

[0014] The gas phase outlet of the second gas-liquid separation device is connected to the first inlet of the first heat exchanger, and the liquid phase outlet discharges the liquefied component of the raw gas;

[0015] The second inlet of the first heat exchanger is connected to the outlet of the first refrigerant storage tank, and the second outlet is connected to the material inlet of the first gas-liquid separation device;

[0016] The liquid phase outlet of the first gas-liquid separation device is used to output hydrogen sulfide, and the gas phase outlet discharges the gaseous components of the raw gas.

[0017] In a preferred embodiment of the present invention,

[0018] A first refrigerant delivery pump is provided on the pipeline connecting the second inlet of the LNG vaporizer and the first outlet of the first heat exchanger; and / or,

[0019] A second refrigerant delivery pump is provided on the pipeline connecting the second inlet of the NG heat exchanger and the first outlet of the second heat exchanger; and / or,

[0020] A raw gas input pump is provided on the inlet pipeline of the first inlet of the second heat exchanger; and / or,

[0021] A condensing gas pump is provided on the pipeline connecting the gas phase outlet of the second gas-liquid separation device and the first inlet of the first heat exchanger.

[0022] In a preferred embodiment of the present invention,

[0023] The first refrigerant in the first refrigerant component is a fluorine-containing refrigerant, preferably monofluoromethane and / or difluoroethylene; and / or

[0024] The second refrigerant in the second refrigerant component is a fluorine-containing refrigerant, preferably difluoromethane and / or trifluoroethylene.

[0025] In a preferred embodiment of the present invention,

[0026] The temperature of the first heat exchanger is -81 to 75°C, preferably -80 to -75°C; and / or

[0027] The temperature of the second heat exchanger is -55 to -50°C, preferably -54 to -50°C; and / or

[0028] The temperature of the LNG vaporizer is -87 to -80°C, preferably -86 to -83°C; and / or

[0029] The temperature of the NG heat exchanger is -58 to -53°C, preferably -56 to -53°C; and / or,

[0030] The temperature of the first gas-liquid separation device is -81 to -62°C; and / or

[0031] The temperature of the second gas-liquid separation device is -55 to -50°C.

[0032] In a preferred embodiment of the present invention,

[0033] The second gas-liquid separation device is also provided with a spare refrigerant inlet, which is connected to the second refrigerant pipeline of the first outlet of the second heat exchanger through a spare pipeline;

[0034] Preferably, the second gas-liquid separation device is further provided with a refrigerant outlet, which is connected to the second refrigerant pipeline of the second inlet of the NG heat exchanger through a spare pipeline.

[0035] In a preferred embodiment of the present invention,

[0036] The first gas-liquid separation device is also provided with a spare refrigerant inlet, which is connected to the first refrigerant pipeline of the first outlet of the first heat exchanger through a spare pipeline;

[0037] Preferably, the first gas-liquid separation device is further provided with a refrigerant outlet, which is connected to the first refrigerant pipeline of the second inlet of the LNG vaporizer through a backup pipeline.

[0038] In a preferred embodiment of the present invention,

[0039] The LNG vaporizer, the NG heat exchanger, the first refrigerant assembly, the second refrigerant assembly, the first heat exchanger, the second heat exchanger, the first gas-liquid separation device, and the second gas-liquid separation device are all provided with a heat preservation layer; and / or,

[0040] The pipelines between the LNG vaporizer, the NG heat exchanger, the first refrigerant component, the second refrigerant component, the first heat exchanger, the second heat exchanger, the first gas-liquid separation device, and the second gas-liquid separation device are all provided with insulation layers.

[0041] The second object of the present invention is to provide a method for using LNG cold energy to separate hydrogen sulfide, which is carried out using the device described in one of the objects of the present invention and preferably includes the following steps:

[0042] S1: LNG is transported to the LNG vaporizer, and the gaseous first refrigerant is transported to the LNG vaporizer; LNG and the gaseous first refrigerant exchange heat to obtain a liquid first refrigerant and vaporized natural gas respectively; the liquid first refrigerant enters the first refrigerant storage tank of the first refrigerant assembly, and the vaporized natural gas enters the NG heat exchanger;

[0043] S2: The gaseous second refrigerant is transported to the NG heat exchanger; the vaporized natural gas exchanges heat with the gaseous second refrigerant to obtain the liquid second refrigerant and the NG with a further increased temperature; the liquid second refrigerant enters the second refrigerant storage tank of the second refrigerant assembly;

[0044] S3: The raw gas is transported to the second heat exchanger, and the liquid second refrigerant is transported from the second refrigerant storage tank to the second heat exchanger; the raw gas and the liquid second refrigerant exchange heat to obtain a gas-liquid mixture material; the second gas-liquid mixture material is transferred to the second gas-liquid separation device; the second refrigerant circulates to the second refrigerant pipeline;

[0045] S4: In the second gas-liquid separation device, the second gas-liquid mixed material is separated into a raw gas liquefied component and a gas phase component, and the gas phase component is input into the first heat exchanger;

[0046] S5: transporting the liquid first refrigerant from the first refrigerant storage tank to the first heat exchanger; the gas phase component from the second gas-liquid separation device exchanges heat with the liquid first refrigerant to obtain a first gas-liquid mixed material; the first gas-liquid mixed material enters the first gas-liquid separation device; the first refrigerant circulates to the second refrigerant pipeline;

[0047] S6: In the first gas-liquid separation device, the second gas-liquid mixed material is separated into a gaseous component of the raw gas and liquid hydrogen sulfide to obtain hydrogen sulfide;

[0048] Preferably, part of the second refrigerant discharged from the first outlet of the second heat exchanger enters the second gas-liquid separation device for heat preservation; more preferably, the second refrigerant entering the second gas-liquid separation device is then discharged from the refrigerant outlet and circulated back to the second refrigerant pipeline between the second inlet of the NG heat exchanger and the first outlet of the second heat exchanger; and / or,

[0049] Part of the first refrigerant discharged from the first outlet of the first heat exchanger enters the first gas-liquid separation device to be kept warm; more preferably, the first refrigerant entering the first gas-liquid distribution device is then discharged from the refrigerant outlet and circulated back to the first refrigerant pipeline between the second inlet of the LNG vaporizer and the first outlet of the first heat exchanger.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] 1. The present invention couples the utilization of LNG cold energy with the separation of hydrogen sulfide, and is very suitable for refineries close to LNG receiving stations. The process avoids the use of amine liquid for hydrogen sulfide absorption and separation and the regeneration of amine liquid, which not only utilizes the useless energy of the LNG receiving station but also avoids the high energy consumption problem of the amine liquid system, and can obtain higher purity hydrogen sulfide to achieve efficient desulfurization.

[0052] 2. The method of using LNG cold energy for hydrogen sulfide separation of the present invention has a simple process and high separation efficiency, and can effectively solve the problem of high energy consumption of the amine liquid system. At the same time, old equipment can be fully utilized without the need to build new equipment. It has good application value for integrated refining and chemical bases with LNG receiving stations.

[0053] 3. The device for separating hydrogen sulfide by using LNG cold energy of the present invention can be widely used for separating hydrogen sulfide from dry gas, liquefied gas and gas produced by hydrocracking, coking, hydrofining and other devices in refineries to meet the requirements of environmental emissions and subsequent processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is a schematic diagram of a device for using LNG cold energy to separate hydrogen sulfide according to the present invention.

[0055] In the figure, 1-LNG, 2-LNG vaporizer, 3-first refrigerant delivery pump, 4-first refrigerant storage tank, 5-first heat exchanger (of raw gas and first refrigerant), 6-NG heat exchanger, 7-NG, 8-second refrigerant delivery pump, 9-second refrigerant storage tank, 10-raw gas, 11-raw gas delivery pump, 12-second heat exchanger (of raw gas and second refrigerant), 13-second gas-liquid separation device, 14-liquefied component of raw gas, 15-condensing gas pump, 16-first gas-liquid separation device, 17-liquid hydrogen sulfide, 18-gaseous component of raw gas. DETAILED DESCRIPTION

[0056] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0057] like Figure 1 As shown, the present invention provides a device for using LNG cold energy to separate hydrogen sulfide, which includes: an LNG vaporizer 2, an NG heat exchanger 6, a first refrigerant component, a second refrigerant component, a first heat exchanger 5, a second heat exchanger 12, a second gas-liquid separation device 13, and a first gas-liquid separation device 16.

[0058] The LNG vaporizer 2 is provided with two outlets and two inlets. Liquid natural gas (i.e., LNG 1) can be input into the first inlet of the LNG vaporizer 2. For example, the first inlet of the LNG vaporizer 2 can be connected to the outlet of the liquefied natural gas storage tank, and the liquefied natural gas enters the LNG vaporizer 2 from the liquefied natural gas storage tank. In a preferred embodiment of the present invention, the temperature of the LNG vaporizer 2 is controlled to be -87 to -80°C, preferably -86 to -83°C. The liquefied natural gas and the first refrigerant exchange heat in the LNG vaporizer 2, and the temperature thereof directly affects the temperature of the liquid first refrigerant after the heat exchange, and further affects the separation of the subsequent gas-liquid separation device, so the temperature of the LNG vaporizer 2 is very important. The first refrigerant is liquefied in the LNG vaporizer 2, and a large amount of cold energy needs to be absorbed during the liquefaction process. If the temperature of LNG vaporizer 2 is higher than the temperature range, the first refrigerant can absorb less cold energy, so more first refrigerant is needed; if the temperature of LNG vaporizer 2 is lower than the temperature range, the temperature of the liquid first refrigerant after heat exchange is too low, which may cause the temperature to be lower than the boiling point of ethane (-88.6°C) in the subsequent separation process, causing it to liquefy, and ultimately no pure hydrogen sulfide can be obtained. The control of the temperature of LNG vaporizer 2 is achieved by adjusting the flow ratio of LNG 1 to the first refrigerant, and the control of the temperature of LNG vaporizer 2 will be described in detail later.

[0059] The LNG vaporizer 2 is connected to the first refrigerant assembly and the NG heat exchanger 6 respectively. Specifically, the first refrigerant from the first refrigerant assembly can enter the heat exchange coil in the LNG vaporizer 2, and the first refrigerant at this time is a gaseous first refrigerant. The boiling point of the first refrigerant is higher than the temperature of the LNG vaporizer 2. It is precisely because the boiling point of the first refrigerant is higher than the temperature of the LNG vaporizer 2 that the gaseous first refrigerant can no longer maintain its gaseous state in the LNG vaporizer 2, and it absorbs cold energy and is converted into a liquid first refrigerant (the cold energy is the cold energy released when the liquid natural gas is converted into the gaseous NG 7); at the same time, the liquid natural gas is converted into gaseous natural gas and releases cold energy. That is, LNG 1 exchanges heat with the gaseous first refrigerant from the first refrigerant assembly in the LNG vaporizer 2, LNG 1 is vaporized to become gaseous vaporized natural gas, and the gaseous first refrigerant is liquefied to become a liquid first refrigerant.

[0060] In a preferred embodiment of the present invention, the first refrigerant component includes a first refrigerant delivery pump 3, a first refrigerant storage tank 4 and a first refrigerant pipeline. Specifically, the second inlet of the LNG vaporizer 2 (the second inlet is connected to the heat exchange coil in the LNG vaporizer 2) is connected to the first refrigerant delivery pump 3, which is used to deliver the gaseous first refrigerant to the LNG vaporizer 2 through the first refrigerant delivery pump 3. The first outlet of the LNG vaporizer 2 (the first outlet is connected to the heat exchange coil in the LNG vaporizer 2) is connected to the first refrigerant storage tank 4, which is used to deliver the liquid first refrigerant from the LNG vaporizer 2 to the first refrigerant storage tank 4. Specifically, in the LNG vaporizer 2, the gaseous first refrigerant is converted into the liquid first refrigerant by heat exchange, and the liquid first refrigerant is delivered to the first refrigerant storage tank 4 under the combined action of gravity and the first refrigerant delivery pump 3.

[0061] The temperature control of LNG vaporizer 2 can be regulated in the following manner. A temperature detection device is provided at the first outlet of LNG vaporizer 2, which can detect the temperature of the liquid first refrigerant when it is output from LNG vaporizer 2, so as to control the temperature of LNG vaporizer 2 according to this temperature data. If the temperature at the first outlet of LNG vaporizer 2 is higher than -80°C, it is necessary to reduce the feed flow ratio of LNG 1 to the first refrigerant and increase the proportion of the first refrigerant in LNG vaporizer 2. As the feed flow ratio of LNG 1 to the first refrigerant gradually decreases, the proportion of the first refrigerant in LNG vaporizer 2 gradually increases, and the temperature of LNG vaporizer 2 gradually decreases until it drops to the range of -87 to -80°C, and the feed flow ratio of LNG 1 to the first refrigerant is stopped. Similarly, if the temperature at the first outlet of LNG vaporizer 2 is lower than -87°C, it is necessary to increase the feed flow ratio of LNG 1 to the first refrigerant and reduce the proportion of the first refrigerant in LNG vaporizer 2. As the feed flow ratio of LNG 1 to the first refrigerant gradually increases, the proportion of the first refrigerant in the LNG vaporizer 2 gradually decreases, and the temperature of the LNG vaporizer 2 gradually increases until it rises to a range of -87 to -80°C, and the feed flow ratio of LNG 1 to the first refrigerant is stopped from being adjusted. Specifically, the feed flow ratio of LNG 1 to the first refrigerant can be adjusted by a flow regulating valve.

[0062] In a more preferred embodiment of the present invention, the first refrigerant is a fluorine-containing refrigerant, preferably monofluoromethane and / or difluoroethylene. The boiling points of monofluoromethane and difluoroethylene are -78.2° C. and -85.7° C., respectively. The technicians can select a suitable first refrigerant according to actual needs.

[0063] The NG heat exchanger 6 is provided with two outlets and two inlets. The second outlet of the LNG vaporizer 2 is connected to the first inlet of the NG heat exchanger 6, and is used to transport the natural gas converted into gas after heat exchange in the LNG vaporizer 2 to the NG heat exchanger 6. The NG heat exchanger 6 is connected to the second refrigerant assembly, and the second refrigerant from the second refrigerant assembly can enter the heat exchange coil in the NG heat exchanger 6. At this time, the second refrigerant is a gaseous second refrigerant. It should be noted that the gaseous second refrigerant is stored in the second refrigerant pipeline, and the liquid second refrigerant is stored in the first refrigerant storage tank 9, which can be recycled. It should be noted that before entering the LNG vaporizer 2, the LNG 1 is pre-pressurized to 10MPa, thereby providing transportation power for the transportation of the LNG 1 and the vaporized natural gas. In a preferred embodiment of the present invention, the temperature of the NG heat exchanger 6 is controlled to be -58 to -53°C, preferably -56 to -53°C. Similar to the temperature control method of the LNG vaporizer 2, the temperature control of the NG heat exchanger 6 is also achieved by adjusting the flow ratio of the vaporized natural gas and the second refrigerant, so it will not be described here in detail.

[0064] The vaporized natural gas obtained by the LNG vaporizer 2 exchanges heat with the second refrigerant in the NG heat exchanger 6, and its temperature directly affects the temperature of the liquid second refrigerant after the heat exchange and further affects the separation of the subsequent gas-liquid separation device, so the temperature of the NG heat exchanger 6 is very important. The second refrigerant is liquefied in the NG heat exchanger 6, and a large amount of cold energy needs to be absorbed during the liquefaction process. If the temperature of the NG heat exchanger 6 is higher than the temperature range, the second refrigerant can absorb less cold energy, so more second refrigerant is needed; if the temperature of the NG heat exchanger 6 is lower than the temperature range, the temperature of the liquid second refrigerant after the heat exchange is too low, which can easily cause the temperature in the subsequent separation process to be lower than the boiling point of propylene (-47.7°C) and propane (-42.1°C), causing propylene and propane to liquefy, and ultimately no pure hydrogen sulfide can be obtained.

[0065] Specifically, the second refrigerant from the second refrigerant component enters the NG heat exchanger 6, and the second refrigerant at this time is a gaseous second refrigerant. In the NG heat exchanger 6, the material containing the vaporized natural gas and the gaseous second refrigerant are heat exchanged; wherein, the boiling point of the second refrigerant is higher than the temperature of the NG heat exchanger 6. It is precisely because the boiling point of the second refrigerant is higher than the temperature of the NG heat exchanger 6 that the gaseous second refrigerant can no longer maintain the gaseous state, and it absorbs cold energy and is converted into a liquid second refrigerant (the cold energy is the cold energy released when the temperature of the vaporized natural gas further increases); at the same time, the temperature of the vaporized natural gas further increases and releases cold energy. That is, the vaporized natural gas further exchanges heat with the gaseous second refrigerant from the second refrigerant component through the NG heat exchanger 6, and the temperature of the vaporized natural gas further increases. The NG 7 obtained after the vaporization and heat exchange of LNG1 is transported to the natural gas pipeline network through the second outlet of the NG heat exchanger 6 for users.

[0066] In a preferred embodiment of the present invention, the second refrigerant assembly includes a second refrigerant delivery pump 8, a second refrigerant storage tank 9 and a second refrigerant pipeline. Specifically, the second inlet of the NG heat exchanger 6 (the second inlet is connected to the heat exchange coil in the NG heat exchanger 6) is connected to the second refrigerant delivery pump 8, which is used to deliver the gaseous second refrigerant to the NG heat exchanger 6 through the second refrigerant delivery pump 8. The first outlet of the NG heat exchanger 6 (the first outlet is connected to the heat exchange coil in the NG heat exchanger 6) is connected to the second refrigerant storage tank 9, which is used to deliver the liquid second refrigerant from the NG heat exchanger 6 to the second refrigerant storage tank 9.

[0067] In a more preferred embodiment of the present invention, the second refrigerant is a fluorine-containing refrigerant, preferably difluoromethane and / or trifluoroethylene. The boiling points of difluoromethane and trifluoroethylene are -51.6° C. and -51° C., respectively. The technicians can select a suitable second refrigerant according to actual needs.

[0068] In summary, during the conversion of LNG 1 to NG 7, the gaseous first refrigerant and the gaseous second refrigerant are respectively converted into the liquid first refrigerant and the liquid second refrigerant maintained in a certain temperature range, and are respectively stored in the first refrigerant storage tank 4 and the second refrigerant storage tank 9. The following is coupled with the hydrogen sulfide separation device to achieve efficient separation of hydrogen sulfide.

[0069] The liquefied gas and dry gas (both belong to the raw gas 10) produced by the refinery mainly contain C2, C3, C4 and other components, among which C2 is mainly ethylene and ethane; C3 is mainly propylene and propane; C4 is mainly butane and isobutane; the concentration of hydrogen sulfide is about 20000mg / Nm 3 Such raw gas 10 produced in refineries must be subjected to hydrogen sulfide removal.

[0070] like Figure 1 As shown, a device for separating hydrogen sulfide using LNG cold energy of the present invention also includes a second heat exchanger 12. Specifically in this embodiment, the second heat exchanger 12 is actually a heat exchanger between raw gas and the second refrigerant. The second heat exchanger 12 is provided with two outlets and two inlets. The raw gas 10 produced by the refinery is input from the first inlet of the second heat exchanger 12. Specifically, the raw gas 10 can be transported to the second heat exchanger 12 by the raw gas delivery pump 11. In a preferred embodiment of the present invention, the temperature of the second heat exchanger 12 is controlled to be -55 to -50°C, preferably -54 to -50°C. Similar to the temperature control method of the LNG vaporizer 2, the temperature control of the second heat exchanger 12 is also achieved by adjusting the flow ratio of the raw gas 10 to the second refrigerant, so it will not be repeated here.

[0071] The raw gas 10 exchanges heat with the liquid second refrigerant in the second heat exchanger 12. This heat exchange process directly affects the separation of the subsequent gas-liquid separation device, so the temperature of the second heat exchanger 12 is very important. The second refrigerant vaporizes in the second heat exchanger 12, and a large amount of cold energy is released during the vaporization process. It should be noted that since the liquid second refrigerant of the feed is heat exchanged through the NG heat exchanger 6, its minimum temperature has been controlled at -58°C, so the temperature will not be too low. However, if the temperature of the second heat exchanger 12 is higher than this temperature range, it is easy to cause propylene with a boiling point of -47.7°C and propane with a boiling point of -42.1°C to be unable to liquefy, thereby bringing it into the next step of hydrogen sulfide separation process, and ultimately no pure hydrogen sulfide can be obtained.

[0072] The second heat exchanger 12 is connected to the second refrigerant assembly and the second gas-liquid separation device 13 respectively. The second refrigerant assembly includes a second refrigerant delivery pump 8, a second refrigerant storage tank 9 and a second refrigerant pipeline. The second inlet of the second heat exchanger 12 (the second inlet is connected to the heat exchange coil in the second heat exchanger 12) is connected to the second refrigerant storage tank 9, which is used to transfer the liquid second refrigerant from the second refrigerant storage tank 9 to the second heat exchanger 12; the first outlet of the second heat exchanger 12 (the first outlet is connected to the heat exchange coil in the second heat exchanger 12) is connected to the second refrigerant delivery pump 8, and then connected to the NG heat exchanger 6, which is used to deliver the second refrigerant after heat exchange to the second refrigerant pipeline through the second refrigerant delivery pump 8, and then to the NG heat exchanger 6, which can be recycled. In the second refrigerant storage tank 9, the liquid second refrigerant is delivered to the heat exchange coil in the second heat exchanger 12 under the combined action of gravity and the second refrigerant delivery pump 8.

[0073] In the second heat exchanger 12, the raw gas 10 and the liquid second refrigerant exchange heat. The second refrigerant releases cold energy; at the same time, the raw gas 10 absorbs cold energy, and some of its components are condensed and liquefied. That is, the raw gas 10 enters the second heat exchanger 12 through the raw gas delivery pump 11, exchanges heat with the liquid second refrigerant, and some of the components in the raw gas 10 are condensed and liquefied to form a second gas-liquid mixed material. The liquid second refrigerant releases cold energy and circulates to the second refrigerant pipeline through the second refrigerant delivery pump 8.

[0074] The second heat exchanger 12 is connected to the second gas-liquid separation device 13. The second gas-liquid separation device 13 is provided with a material inlet, a liquid phase outlet and a gas phase outlet. Specifically, the second outlet of the second heat exchanger 12 is connected to the material inlet of the second gas-liquid separation device 13, and is used to input the second gas-liquid mixture material from the second heat exchanger 12 to the second gas-liquid separation device 13. It should be noted that the raw gas 10 is pre-pressurized to 1.0-1.5Mpa before entering the second heat exchanger 12, thereby providing transportation power for the transportation of the raw gas 10 and the second gas-liquid mixture material after heat exchange.

[0075] The second gas-liquid mixture enters from the middle of the second gas-liquid separation device 13 and is separated into a raw gas-liquid component 14 and a gas phase component. The raw gas-liquid component 14 is extracted from the bottom of the second gas-liquid separation device 13, and the gas phase component is transferred out from the top gas phase outlet of the second gas-liquid separation device 13.

[0076] In a preferred embodiment of the present invention, the second gas-liquid separation device 13 has a heat exchange coil inside, and the second gas-liquid separation device 13 is also provided with a refrigerant inlet, which is connected to the heat exchange coil inside. The refrigerant inlet of the second gas-liquid separation device 13 is connected to the first outlet of the second cold heat exchanger 12 (the first outlet is connected to the heat exchange coil in the second heat exchanger 12), and a spare pipeline is provided between the two. Since the first outlet of the second cold heat exchanger 12 is connected to the second refrigerant delivery pump 8, the spare pipeline is also connected to the second refrigerant delivery pump 8. In this way, the temperature of the second gas-liquid separation device 13 can be maintained within -55 to -50°C, which is more conducive to separating the second gas-liquid mixed material and improving the desulfurization rate. When necessary, the second refrigerant can be partially input into the heat exchange coil of the second gas-liquid separation device 13 through the spare pipeline between the first outlet of the second heat exchanger 12 and the refrigerant inlet of the second gas-liquid separation device 13 to achieve heat exchange between the second refrigerant and the second gas-liquid mixed material. Specifically, if the temperature of the second gas-liquid separation device 13 is higher than -50°C, the second refrigerant can be transported to the second gas-liquid separation device 13 through the backup pipeline and the second refrigerant delivery pump 8 to lower the temperature of the second gas-liquid separation device 13 and maintain the temperature of the second gas-liquid separation device 13 within -55 to -50°C.

[0077] In a more preferred embodiment of the present invention, the second gas-liquid separation device 13 is provided with a refrigerant outlet, which is connected to the heat exchange coil inside the second gas-liquid separation device 13. The refrigerant outlet of the second gas-liquid separation device 13 is connected to the second refrigerant pipeline at the second inlet of the NG heat exchanger 6 through a spare pipeline, and the connecting position is preferably set before the second refrigerant delivery pump 8, so as to transport the second refrigerant after heat exchange back to the second refrigerant pipeline through the spare pipeline for recycling.

[0078] It should be noted that the gas-liquid separation device of this embodiment does not constitute a limitation to the present invention, and can be configured as a rectification tower or a fractionation tower.

[0079] As mentioned above, in the second heat exchanger 12, some components in the raw gas 10 are condensed and liquefied. This is because the temperature of the raw gas and the second refrigerant heat exchanger 12 is -55 to 50°C, which is lower than the boiling points of propylene, propane, butane and isobutane (propylene -47.7°C, propane -42.1°C, butane -0.5°C, isobutane -10.5°C). Therefore, under this condition, propylene, propane, butane and isobutane absorb cold energy and are converted into liquid phase, that is, the C3 and C4 components in the raw gas 10 are converted into liquid phase, and the raw gas 10 is heat-exchanged in the second heat exchanger 12 to obtain a second gas-liquid mixed material. After the second gas-liquid mixed material is subjected to gas-liquid separation in the second gas-liquid separation device 13, the raw gas liquefied component 14 is obtained, which is the C3 and C4 components, and the gas phase components are hydrogen sulfide and C2 components. The second gas-liquid separation device 13 is provided with a gas phase outlet at the top and a liquid phase outlet at the bottom. The liquid phase C3 and C4 components (i.e., the raw gas liquefied components 14) are extracted from the liquid phase outlet of the second gas-liquid separation device 13, and the gas phase hydrogen sulfide and C2 components are transferred out from the gas phase outlet of the second gas-liquid separation device 13.

[0080] The device for separating hydrogen sulfide by using LNG cold energy of the present invention further comprises a first heat exchanger 5. Specifically in this embodiment, the first heat exchanger 5 is actually a heat exchanger between raw gas and the first refrigerant. The first heat exchanger 5 is provided with two outlets and two inlets. The first inlet of the first heat exchanger 5 is connected to the gas phase outlet of the second gas-liquid separation device 13 to input the gas phase components (hydrogen sulfide, C2 component) from the second gas-liquid separation device 13 into the first heat exchanger 5. Specifically in this embodiment, the transportation of hydrogen sulfide and C2 components in the gas phase can be realized by the condensing gas pump 15.

[0081] In a preferred embodiment of the present invention, the temperature of the first heat exchanger 5 is controlled to be -81 to -75°C, preferably -80 to -75°C. Similar to the temperature control method of the LNG vaporizer 2, the temperature control of the first heat exchanger 5 is also achieved by adjusting the flow ratio of the gas phase component entering the first heat exchanger 5 to the first refrigerant, so it is not repeated here. It should be noted that the first refrigerant here refers to the liquid first refrigerant from the first refrigerant storage tank 4.

[0082] The gas phase components entering the first heat exchanger 5 exchange heat with the first refrigerant in the first heat exchanger 5. This heat exchange process directly affects the separation of the subsequent gas-liquid separation device, so the temperature of the first heat exchanger 5 is very important. It should be noted that since the first refrigerant fed is heat exchanged through the LNG vaporizer 2, its minimum temperature has been controlled at -87°C, so the temperature will not be too low. However, if the temperature of the first heat exchanger 5 is higher than -75°C, it is easy to cause incomplete liquefaction of hydrogen sulfide and poor desulfurization effect.

[0083] The first heat exchanger 5 is connected to the first refrigerant assembly and the first gas-liquid separation device 16 respectively. The first refrigerant assembly includes a first refrigerant delivery pump 3, a first refrigerant storage tank 4 and a first refrigerant pipeline. The second inlet of the first heat exchanger 5 (the second inlet is connected to the heat exchange coil in the first heat exchanger 5) is connected to the first refrigerant storage tank 4, which is used to transfer the liquid first refrigerant from the first refrigerant storage tank 4 to the first heat exchanger 5; the first outlet of the first heat exchanger 5 (the first outlet is connected to the heat exchange coil in the first heat exchanger 5) is connected to the first refrigerant delivery pump 3, and then connected to the LNG vaporizer 2, which is used to circulate the gaseous first refrigerant through the first refrigerant delivery pump 3, and then can be delivered to the LNG vaporizer 2. In the first refrigerant heat exchanger 5, the gaseous phase components including hydrogen sulfide and C2 components and the liquid first refrigerant exchange heat. The liquid first refrigerant releases cold energy; at the same time, the hydrogen sulfide component in the gas phase component absorbs cold energy and is condensed and liquefied, and finally the gas phase component forms a first gas-liquid mixed material through heat exchange. That is, the gas phase component from the second gas-liquid separation device 13 is transported to the first heat exchanger 5 through the condensing gas pump 15, and heat is exchanged with the liquid first refrigerant, and the hydrogen sulfide component therein is condensed and liquefied, thereby obtaining the first gas-liquid mixed material.

[0084] The first heat exchanger 5 is connected to the first gas-liquid separation device 16. The first gas-liquid separation device 16 is provided with a material inlet, a gas phase outlet and a liquid phase outlet. Specifically, the second outlet of the first heat exchanger 5 is connected to the material inlet of the first gas-liquid separation device 16, and is used to input the first gas-liquid mixture material from the first heat exchanger 5 to the first gas-liquid separation device 16. In the first gas-liquid separation device 16, the first gas-liquid mixture material is separated into a gaseous component 18 of the raw gas and liquid hydrogen sulfide 17, which are respectively extracted from the gas phase outlet and the liquid phase outlet.

[0085] In a preferred embodiment of the present invention, a heat exchange coil is provided inside the first gas-liquid separation device 16, and the first gas-liquid separation device 16 is also provided with a refrigerant inlet, which is communicated with the heat exchange coil inside it. The refrigerant inlet of the first gas-liquid separation device 16 is connected to the first outlet of the first heat exchanger 5 (the first outlet is connected to the heat exchange coil in the first heat exchanger 5), and a spare pipeline is provided between the two. Since the first outlet of the first heat exchanger 5 is connected to the first refrigerant delivery pump 3, the spare pipeline is also connected to the first refrigerant delivery pump 3. In this way, the temperature of the first gas-liquid separation device 16 can be maintained within -81 to -62°C, which is more conducive to separating the first gas-liquid mixed material and improving the desulfurization rate. When necessary, the first refrigerant can be partially input into the heat exchange coil of the first gas-liquid separation device 16 through the spare pipeline between the first outlet of the first heat exchanger 5 and the refrigerant inlet of the first gas-liquid separation device 16 to achieve heat exchange between the first refrigerant and the first gas-liquid mixed material. Specifically, if the temperature of the first gas-liquid separation device 16 is higher than -62°C, the first refrigerant can be transported to the first gas-liquid separation device 16 through the backup pipeline and the first refrigerant delivery pump 3 to lower the temperature of the first gas-liquid separation device 16 and maintain the temperature of the first gas-liquid separation device 16 within -81 to -62°C.

[0086] In another preferred embodiment of the present invention, the first gas-liquid separation device 16 is provided with a refrigerant outlet, which is connected to the heat exchange coil inside the first gas-liquid separation device 16. The refrigerant outlet of the first gas-liquid separation device 16 is connected to the first refrigerant pipeline of the second inlet of the LNG vaporizer 2 through a spare pipeline, and the connecting position is preferably set before the first refrigerant delivery pump 3 to deliver the first refrigerant to the first refrigerant pipeline for recycling.

[0087] As mentioned above, in the first heat exchanger 5, part of the gas phase components from the second gas-liquid separation device are condensed and liquefied. This is because the temperature of the raw gas and the first refrigerant heat exchanger 5 is -81 to 75°C, which is lower than the boiling point of hydrogen sulfide (-60.4°C). Therefore, under this condition, the hydrogen sulfide in the gas phase component absorbs cold energy and is converted into a liquid phase. The gas phase component is heat exchanged by the first heat exchanger 5 to obtain a first gas-liquid mixed material. After the first gas-liquid mixed material is subjected to gas-liquid separation in the first gas-liquid separation device 16, liquid hydrogen sulfide 17 and a gas phase C2 component (i.e., a gaseous component 18 of the raw gas) are obtained. The first gas-liquid separation device 16 is provided with a gas phase outlet at the top and a liquid phase outlet at the bottom. Liquid hydrogen sulfide 17 is extracted from the liquid phase outlet of the first gas-liquid separation device 16, and the gas phase C2 component is returned to the raw gas system from the gas phase outlet of the first gas-liquid separation device 16 for utilization. The desulfurized raw gas gaseous component 18 will be used as a hydrogen production raw material or a heating furnace fuel.

[0088] In a preferred embodiment of the present invention, all components in the device for using LNG cold energy to separate hydrogen sulfide need to be wrapped with an insulation layer, and the pipelines connecting two components also need to be wrapped with an insulation layer to reduce the loss of cold energy and ensure that the temperature of each component is controlled within the required range.

[0089] It should be noted that, in the present invention, the first refrigerant pipeline includes the pipeline between the first heat exchanger 5 and the LNG vaporizer 2, the pipeline between the LNG vaporizer 2 and the first refrigerant storage tank 4, the pipeline between the first refrigerant storage tank 4 and the raw gas and the first refrigerant heat exchanger 5, and the refrigerant standby pipeline between the first heat exchanger 5 and the LNG vaporizer 2 and the first gas-liquid separation device 16 respectively; the second refrigerant pipeline includes the pipeline between the raw gas and the second refrigerant heat exchanger 12 and the NG heat exchanger 6, the pipeline between the NG heat exchanger 6 and the second refrigerant storage tank 9, the pipeline between the second refrigerant storage tank 9 and the raw gas and the second refrigerant heat exchanger 12, and the refrigerant standby pipeline between the second heat exchanger 12 and the NG heat exchanger 6 and the second gas-liquid separation device 13 respectively. In addition, the positions of the first refrigerant delivery pump 3 and the second refrigerant delivery pump 8 of the present invention are not limited to the present embodiment, as long as they are respectively arranged in the first refrigerant pipeline and the second refrigerant pipeline.

[0090] It should be noted that the gaseous first refrigerant and the liquid first refrigerant can be recycled and reused; the recycling here specifically refers to the mutual conversion of the gaseous first refrigerant and the liquid first refrigerant (that is, the gaseous first refrigerant absorbs cold energy and is converted into the liquid first refrigerant, and the liquid first refrigerant releases cold energy and is converted into the gaseous first refrigerant) and then recycled and reused; the second refrigerant is also the same. After the first refrigerant is output from the first refrigerant pipeline or the first refrigerant storage tank 4, it will enter the heat exchange coils in the LNG vaporizer 2, the NG heat exchanger 6, the second heat exchanger 12, the second gas-liquid separation device 13, the first heat exchanger 5, and the first gas-liquid separation device 16, and will not come into contact with the LNG 1, NG 7, the raw gas 10, the first gas-liquid mixed material, and the second gas-liquid mixed material.

[0091] The LNG vaporizer 2, NG heat exchanger 6, second heat exchanger 12, second gas-liquid separation device 13, first heat exchanger 5, and first gas-liquid separation device 16 of the present invention all adopt tubular heat exchange, which does not constitute a limitation to the present invention, and can also be set as plate heat exchange. In addition, in the device for separating hydrogen sulfide using LNG cold energy of the present invention, the LNG vaporizer 2, first heat exchanger 5, NG heat exchanger 6, second heat exchanger 12, second gas-liquid separation device 13, first gas-liquid separation device 16 and other equipment can all be transformed using the old equipment of the existing hydrocracking, coking, hydrofining and other equipment in the factory, without the need to build new equipment, which has good application value for the integrated refining and chemical base with LNG receiving station.

[0092] The present invention also provides a method for using LNG cold energy to separate hydrogen sulfide. The method adopts the above-mentioned device for using LNG cold energy to separate hydrogen sulfide, and specifically comprises the following steps:

[0093] S1: LNG 1 is delivered to LNG vaporizer 2, and gaseous first refrigerant is delivered to LNG vaporizer 2 through first refrigerant delivery pump 3; the temperature of LNG vaporizer 2 is controlled to be -87 to -80°C; in LNG vaporizer 2, LNG 1 exchanges heat with gaseous first refrigerant to obtain liquid first refrigerant and vaporized natural gas respectively; liquid first refrigerant is transferred to first refrigerant storage tank 4 of first refrigerant assembly, and vaporized natural gas enters NG heat exchanger 6;

[0094] S2: The gaseous second refrigerant from the second refrigerant pipeline is delivered to the NG heat exchanger 6 through the second refrigerant delivery pump 8; the temperature of the NG heat exchanger 6 is controlled to be -58 to -53°C; in the NG heat exchanger 6, the vaporized natural gas exchanges heat with the gaseous second refrigerant to obtain the liquid second refrigerant and the NG 7 with a further increased temperature; the liquid second refrigerant is transferred to the second refrigerant storage tank 9 of the second refrigerant assembly;

[0095] S3: The raw gas 10 is delivered to the second heat exchanger 12 through the raw gas delivery pump 11, and the liquid second refrigerant is delivered to the second heat exchanger 12; the temperature of the second heat exchanger 12 is controlled to be -55 to -50°C; in the second heat exchanger 12, the raw gas 10 exchanges heat with the liquid second refrigerant to obtain a second gas-liquid mixed material; the second gas-liquid mixed material is transferred to the second gas-liquid separation device 13; the second refrigerant is circulated to the second refrigerant pipeline through the second refrigerant delivery pump 8; in this step, the second gas-liquid mixed material includes liquid C3 and C4 components, and gaseous hydrogen sulfide and C2 components;

[0096] S4: In the second gas-liquid separation device 13, the temperature is controlled to be -55 to -50°C, and the second gas-liquid mixture is separated into a gas phase component and a raw gas liquefied component 14; the raw gas liquefied component 14 can be extracted from the liquid phase outlet of the second gas-liquid separation device 13; under the action of the condenser pump 15, the gas phase component is transferred from the gas phase outlet of the second gas-liquid separation device 13 to the first heat exchanger 5;

[0097] S5: The liquid first refrigerant is transported from the first refrigerant storage tank 4 to the first heat exchanger 5; the temperature of the first heat exchanger 5 is controlled to be -81 to -75°C; in the first heat exchanger 5, the gas phase component from the second gas-liquid separation device 13 exchanges heat with the liquid first refrigerant to obtain a first gas-liquid mixed material; the first gas-liquid mixed material is transferred to the first gas-liquid separation device 16; the first refrigerant is circulated to the first refrigerant pipeline through the first refrigerant transport pump 3;

[0098] S6: In the first gas-liquid separation device 16, the temperature is controlled at -81 to -62°C, and the first gas-liquid mixture is separated into liquid hydrogen sulfide 17 and raw gas gaseous component 18; the liquid hydrogen sulfide 17 can be produced from the liquid phase outlet of the first gas-liquid separation device 16, and the raw gas gaseous component 18 is returned to the raw gas system from the gas phase outlet of the first gas-liquid separation device 16 for reuse.

[0099] Example 1

[0100] S1: LNG 1 is delivered to LNG vaporizer 2, and gaseous first refrigerant is delivered to LNG vaporizer 2 through first refrigerant delivery pump 3; the temperature of LNG heat exchanger 6 is controlled to be -80°C; in LNG vaporizer 2, LNG 1 exchanges heat with gaseous first refrigerant to obtain liquid first refrigerant and vaporized natural gas respectively; liquid first refrigerant is transferred to first refrigerant storage tank 4 of first refrigerant assembly, and vaporized natural gas enters NG heat exchanger 6; wherein, first refrigerant is monofluoromethane;

[0101] S2: The gaseous second refrigerant from the second refrigerant pipeline is delivered to the NG heat exchanger 6 through the second refrigerant delivery pump 8; the temperature of the NG heat exchanger 6 is controlled to be -53°C; in the NG heat exchanger 6, the vaporized natural gas exchanges heat with the gaseous second refrigerant to obtain the liquid second refrigerant and the NG 7 with a further increased temperature respectively; the liquid second refrigerant is transferred to the second refrigerant storage tank 9 of the second refrigerant assembly; wherein the second refrigerant is difluoromethane;

[0102] S3: The raw gas 10 is delivered to the second heat exchanger 12 through the raw gas delivery pump 11, and the liquid second refrigerant is delivered to the second heat exchanger 12; the temperature of the second heat exchanger 12 is controlled to be -50°C; in the second heat exchanger 12, the raw gas 10 exchanges heat with the liquid second refrigerant to obtain a second gas-liquid mixed material; the second gas-liquid mixed material is transferred to the second gas-liquid separation device 13; the second refrigerant is circulated to the second refrigerant pipeline through the second refrigerant delivery pump 8; in this step, the second gas-liquid mixed material includes liquid C3 and C4 components, and gaseous hydrogen sulfide and C2 components;

[0103] The embodiment uses the refinery raw gas 10 composed of the following:

[0104]

[0105] S4: In the second gas-liquid separation device 13, the temperature is controlled to be -50°C, and the second gas-liquid mixture is separated into a gas phase component and a raw gas liquefied component 14; the raw gas liquefied component 14 can be extracted from the liquid phase outlet of the second gas-liquid separation device 13; under the action of the condenser pump 15, the gas phase component is transferred from the gas phase outlet of the second gas-liquid separation device 13 to the first heat exchanger 5;

[0106] S5: The liquid first refrigerant is transported from the first refrigerant storage tank 4 to the first heat exchanger 5; the temperature of the first heat exchanger 5 is controlled to be -75°C; in the first heat exchanger 5, the gas phase component from the second gas-liquid separation device 13 exchanges heat with the liquid first refrigerant to obtain a first gas-liquid mixed material; the first gas-liquid mixed material is transferred to the first gas-liquid separation device 16; the first refrigerant is circulated to the first refrigerant pipeline through the first refrigerant transport pump 3;

[0107] S6: In the first gas-liquid separation device 16, the temperature is controlled at -70°C, and the first gas-liquid mixture is separated into liquid hydrogen sulfide 17 and raw gas gaseous component 18; the liquid hydrogen sulfide 17 can be produced from the liquid phase outlet of the first gas-liquid separation device 16, and the raw gas gaseous component 18 is returned to the raw gas system from the gas phase outlet of the first gas-liquid separation device 16 for reuse.

[0108] After the above treatment, liquid hydrogen sulfide is obtained, and the desulfurization rate reaches 99.5%.

[0109] The calculation method of the hydrogen sulfide removal rate is: the weight of the removed hydrogen sulfide / the content of hydrogen sulfide in the raw gas. The removed hydrogen sulfide is the liquid hydrogen sulfide component extracted from the first gas-liquid separation device 16; the content of hydrogen sulfide in the raw gas = the flow rate of the raw gas 10 × the feeding time of the raw gas 10 × the hydrogen sulfide concentration of the raw gas 10. It should be noted that the unit of "hydrogen sulfide concentration" here is kg / m3, and the hydrogen sulfide in the raw gas 10 of this embodiment is 9000mL / m 3 Before substituting into the calculation formula, it is necessary to 3 Multiply by the density of hydrogen sulfide.

[0110] Example 2

[0111] This embodiment is basically the same as Embodiment 1, with the only difference being that: the temperature of the LNG heat exchanger 6 is controlled to be -87°C, the temperature of the first heat exchanger 5 is controlled to be -81°C, the temperature of the NG heat exchanger 6 is controlled to be -58°C, and the temperature of the second heat exchanger 12 is controlled to be -55°C; the temperature of the first gas-liquid separation device 16 is controlled to be -75°C, and the temperature of the second gas-liquid separation device 13 is controlled to be -53°C.

[0112] After the above treatment, liquid hydrogen sulfide is obtained, and the desulfurization rate reaches 99.9%.

[0113] Example 3

[0114] This embodiment is basically the same as Embodiment 1, with the only difference being that: the temperature of the LNG heat exchanger 6 is controlled to be -87°C, the temperature of the first heat exchanger 5 is controlled to be -78°C, the temperature of the NG heat exchanger 6 is controlled to be -58°C, and the temperature of the second heat exchanger 12 is controlled to be -52°C; the temperature of the first gas-liquid separation device 16 is controlled to be -75°C, and the temperature of the second gas-liquid separation device 13 is controlled to be -50°C.

[0115] After the above treatment, liquid hydrogen sulfide was obtained, and the desulfurization rate reached 99.7%.

[0116] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0117] In the description of the present invention, unless otherwise specified, the terms "upper", "lower", "left", "right", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0118] The above technical solution is only one implementation mode of the present invention. For those skilled in the art, it is easy to make various types of improvements or modifications based on the principles disclosed in the present invention, and it is not limited to the technical solution described in the above specific embodiments of the present invention. Therefore, the above description is only preferred and does not have a restrictive meaning.

Claims

1. A device for separating hydrogen sulfide using LNG cold energy, characterized in that: It includes an LNG vaporizer, a first refrigerant component, an NG heat exchanger, a second refrigerant component, a first heat exchanger, a second heat exchanger, a first gas-liquid separation device and a second gas-liquid separation device; wherein the LNG vaporizer for inputting LNG is connected to the first refrigerant component, the NG heat exchanger and the first heat exchanger; the NG heat exchanger is also connected to the second refrigerant component and the second heat exchanger for inputting raw gas; the first heat exchanger is also connected to the first gas-liquid separation device, the first refrigerant component and the second gas-liquid separation device; the second heat exchanger is also connected to the second refrigerant component and the second gas-liquid separation device.

2. The device according to claim 1, characterized in that: The first refrigerant assembly includes a first refrigerant delivery pump, a first refrigerant storage tank and a first refrigerant pipeline; and / or, The second refrigerant assembly includes a second refrigerant delivery pump, a second refrigerant storage tank and a second refrigerant pipeline.

3. The device according to claim 2, characterized in that: The LNG vaporizer, the NG heat exchanger, the first heat exchanger and the second heat exchanger are respectively provided with a first inlet, a second inlet, a first outlet and a second outlet; the first gas-liquid separation device and the second gas-liquid separation device are respectively provided with a material inlet, a gas phase outlet and a liquid phase outlet; wherein: The first inlet of the LNG vaporizer is used to input LNG, the second inlet is connected to the first outlet of the first heat exchanger, the first outlet is connected to the inlet of the first refrigerant storage tank, and the second outlet is connected to the first inlet of the NG heat exchanger; The second inlet of the NG heat exchanger is connected to the first outlet of the second heat exchanger, the first outlet is connected to the inlet of the second refrigerant storage tank, and the second outlet outputs NG; The first inlet of the second heat exchanger is used to input raw gas, the second inlet is connected to the outlet of the second refrigerant storage tank, and the second outlet is connected to the material inlet of the second gas-liquid separation device; The gas phase outlet of the second gas-liquid separation device is connected to the first inlet of the first heat exchanger, and the liquid phase outlet discharges the liquefied component of the raw gas; The second inlet of the first heat exchanger is connected to the outlet of the first refrigerant storage tank, and the second outlet is connected to the material inlet of the first gas-liquid separation device; The liquid phase outlet of the first gas-liquid separation device is used to output hydrogen sulfide, and the gas phase outlet discharges the gaseous components of the raw gas.

4. The device according to claim 3, characterized in that: A first refrigerant delivery pump is provided on the pipeline connecting the second inlet of the LNG vaporizer and the first outlet of the first heat exchanger; and / or, A second refrigerant delivery pump is provided on the pipeline connecting the second inlet of the NG heat exchanger and the first outlet of the second heat exchanger; and / or, A raw gas input pump is provided on the inlet pipeline of the first inlet of the second heat exchanger; and / or, A condensing gas pump is provided on the pipeline connecting the gas phase outlet of the second gas-liquid separation device and the first inlet of the first heat exchanger.

5. The device according to claim 1, characterized in that: The first refrigerant in the first refrigerant component is a fluorine-containing refrigerant, preferably monofluoromethane and / or difluoroethylene; and / or The second refrigerant in the second refrigerant component is a fluorine-containing refrigerant, preferably difluoromethane and / or trifluoroethylene.

6. The device according to claim 1, characterized in that: The temperature of the first heat exchanger is -81 to 75°C, preferably -80 to -75°C; and / or The temperature of the second heat exchanger is -55 to -50°C, preferably -54 to -50°C; and / or The temperature of the LNG vaporizer is -87 to -80°C, preferably -86 to -83°C; and / or The temperature of the NG heat exchanger is -58 to -53°C, preferably -56 to -53°C; and / or, The temperature of the first gas-liquid separation device is -81 to -62°C; and / or The temperature of the second gas-liquid separation device is -55 to -50°C.

7. The device according to claim 1, characterized in that: The second gas-liquid separation device is also provided with a spare refrigerant inlet, which is connected to the second refrigerant pipeline of the first outlet of the second heat exchanger through a spare pipeline; Preferably, the second gas-liquid separation device is further provided with a refrigerant outlet, which is connected to the second refrigerant pipeline of the second inlet of the NG heat exchanger through a spare pipeline.

8. The device according to claim 1, characterized in that: The first gas-liquid separation device is also provided with a spare refrigerant inlet, which is connected to the first refrigerant pipeline of the first outlet of the first heat exchanger through a spare pipeline; Preferably, the first gas-liquid separation device is further provided with a refrigerant outlet, which is connected to the first refrigerant pipeline of the second inlet of the LNG vaporizer through a backup pipeline.

9. The device according to claim 1, characterized in that: The LNG vaporizer, the NG heat exchanger, the first refrigerant assembly, the second refrigerant assembly, the first heat exchanger, the second heat exchanger, the first gas-liquid separation device, and the second gas-liquid separation device are all provided with a heat preservation layer; and / or, The pipelines between the LNG vaporizer, the NG heat exchanger, the first refrigerant component, the second refrigerant component, the first heat exchanger, the second heat exchanger, the first gas-liquid separation device, and the second gas-liquid separation device are all provided with insulation layers.

10. A method for using LNG cold energy to separate hydrogen sulfide, characterized in that: The method is carried out using the device according to any one of claims 1 to 9, preferably comprising the following steps: S1: LNG is transported to the LNG vaporizer, and the gaseous first refrigerant is transported to the LNG vaporizer; LNG and the gaseous first refrigerant exchange heat to obtain a liquid first refrigerant and vaporized natural gas respectively; the liquid first refrigerant enters the first refrigerant storage tank of the first refrigerant assembly, and the vaporized natural gas enters the NG heat exchanger; S2: The gaseous second refrigerant is transported to the NG heat exchanger; the vaporized natural gas exchanges heat with the gaseous second refrigerant to obtain the liquid second refrigerant and the NG with a further increased temperature; the liquid second refrigerant enters the second refrigerant storage tank of the second refrigerant assembly; S3: transporting the raw gas to the second heat exchanger, and transporting the liquid second refrigerant from the second refrigerant storage tank to the second heat exchanger; the raw gas and the liquid second refrigerant exchange heat to obtain a second gas-liquid mixture material; the second gas-liquid mixture material is transferred to the second gas-liquid separation device; The second refrigerant circulates to the second refrigerant pipeline; S4: In the second gas-liquid separation device, the second gas-liquid mixed material is separated into a raw gas liquefied component and a gas phase component, and the gas phase component is input into the first heat exchanger; S5: transporting the liquid first refrigerant from the first refrigerant storage tank to the first heat exchanger; the gas phase component from the second gas-liquid separation device exchanges heat with the liquid first refrigerant to obtain a first gas-liquid mixed material; the first gas-liquid mixed material enters the first gas-liquid separation device; the first refrigerant circulates to the second refrigerant pipeline; S6: In the first gas-liquid separation device, the second gas-liquid mixed material is separated into a gaseous component of the raw gas and liquid hydrogen sulfide to obtain hydrogen sulfide; Preferably, part of the second refrigerant discharged from the first outlet of the second heat exchanger enters the second gas-liquid separation device for heat preservation; more preferably, the second refrigerant entering the second gas-liquid separation device is then discharged from the refrigerant outlet and circulated back to the second refrigerant pipeline between the second inlet of the NG heat exchanger and the first outlet of the second heat exchanger; and / or, Part of the first refrigerant discharged from the first outlet of the first heat exchanger enters the first gas-liquid separation device to be kept warm; more preferably, the first refrigerant entering the first gas-liquid distribution device is then discharged from the refrigerant outlet and circulated back to the first refrigerant pipeline between the second inlet of the LNG vaporizer and the first outlet of the first heat exchanger.

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