Device and process method for preparing LNG (liquefied natural gas) from coke oven gas

Abstract

The invention discloses a device for preparing liquefied natural gas (LNG) from coke oven gas, which comprises a compression section, a desulfurization section, a synthesis section, a drying section, a liquefaction section and a storage and transportation section, and a decarburization section is added between the synthesis section and the drying section. The invention further discloses a process method for preparing LNG from coke oven gas based on the device. By improving the device and the process for preparing the LNG from the coke oven gas, the decarburization section is added between the synthesis section and the drying section, the reactor of the synthesis section is further changed into two sections from three sections, and the drying section is changed into isobaric drying from variable-pressure drying, so that the economical efficiency and the stability of the operation of the device are greatly improved.

Description

Technical Field

[0001] The present invention relates to the field of liquefied natural gas, and in particular to a device and a process method for synthesizing and purifying liquefied natural gas (LNG) from coke oven gas. Background Art

[0002] The existing coke oven gas to LNG process mainly consists of compression section, desulfurization section, synthesis section, pressure swing drying section, liquefaction section, storage and transportation section and supporting public works. The flow diagram is as follows: Figure 1 As shown, where:

[0003] Compression section: After the raw coke oven gas from the gas holder is filtered by the raw gas filter and compressed to 0.45Mpag by the raw gas compressor, it enters the de-oiling and de-naphthalene tower and the rough desulfurization tower for pre-treatment to remove impurities such as tar, naphthalene, and inorganic sulfur. After that, it enters the synthesis gas compressor, and the pressure is raised to about 2.2Mpag again before entering the desulfurization section for fine desulfurization to protect the catalyst in the synthesis section.

[0004] Desulfurization section: The high-pressure coke oven gas from the compression section first enters the oil filter tank to prevent the compression section from bringing oil to damage the hydrogenation catalyst. Then, after hydrogenation conversion in the pre-hydrogenation converter and the first-stage hydrogenation converter, most of the organic sulfur in the coke oven gas is converted into inorganic sulfur. The inorganic sulfur is then removed through the medium-temperature desulfurization tank. After passing through the second-stage hydrogenation converter and the zinc oxide desulfurization tank, the organic sulfur is converted and removed again, and the total sulfur content in the product gas of the desulfurization unit is finally reduced to less than 0.1 ppm. Since the activity of the catalyst in this section has a very high temperature requirement, the medium temperature needs to be adjusted through multiple heat exchangers before entering each reactor to meet the requirements of the catalyst.

[0005] Synthesis section: The coke oven gas from the desulfurization section and after fine desulfurization first enters the CuO protection bed to prevent sulfur poisoning of the synthesis catalyst. Then the medium is divided into two parts, one of which is mixed with the circulating gas and enters a reactor. In the reactor, CO 2 , CO and H 2 The CH was synthesized under the action of catalyst 4 , while releasing heat; the synthesis gas after the reaction is mixed with another part of the coke oven gas after recovering heat through the first-stage waste heat boiler and then enters the second-stage reactor. After the synthesis gas after the reaction is recovered by the second-stage waste heat boiler, the temperature is adjusted by multiple heat exchangers, and one part enters the third-stage reactor, and the other part is used as circulating gas; CO in the synthesis gas synthesized by the three-stage reactor 2 The content is less than 300PPm; since the activity of the catalyst requires a high temperature, the medium needs to be regulated by one or more heat exchangers before entering each level of reactor;

[0006] Pressure swing drying section: The synthesis gas from the synthesis section enters the molecular sieve drying tower to remove water and CO 2 , making water and CO 2 The content is reduced to below 1PPm and 50PPm respectively, and the adsorption pressure is about 2.0MPag; after the molecular sieve is saturated with adsorption, the hydrogen-rich gas separated by the cold box is regenerated, and the regeneration pressure is about 1.0Mpag. The hydrogen-rich gas after the molecular sieve regeneration can be used as fuel or sent to the torch;

[0007] Liquefaction section: The dry synthesis gas from the pressure swing drying section enters the cold box for heat exchange with the mixed refrigerant and is distilled at different temperatures and pressures to separate the H 2 and N 2 The heat required by the distillation tower comes from the synthesis gas itself, and the cold is provided by the nitrogen cycle; the nitrogen-rich gas recovers the cold and is discharged into the flare, the hydrogen-rich gas recovers the cold and is used as the regeneration gas of the molecular sieve, and the LNG enters the LNG storage tank after throttling and pressure reduction;

[0008] Storage and transportation section: The LNG entering the LNG storage tank is pumped into the LNG tank truck through the LNG pump. The flash gas (BOG) generated in the storage tank is compressed by the BOG compressor and returned to the entrance of the drying section for re-liquefaction.

[0009] The above existing coke oven gas to LNG device and process flow have the following problems:

[0010] 1. Poor ability to resist load fluctuations. In the existing process flow, the drying process used in the drying section is a drying process for the depressurization and regeneration of molecular sieves, and the regenerated gas is the hydrogen-rich gas separated by cryogenic distillation. Since the molecular sieve loading capacity is designed according to 100% load, when the raw gas supply is insufficient, the hydrogen-rich gas produced by cryogenic distillation cannot meet the requirements of molecular sieve regeneration. At this time, a portion of the synthesis gas needs to be supplemented as regeneration gas to meet the requirements of molecular sieve regeneration. Therefore, the synthesis gas entering the cold box will be further reduced, resulting in a further reduction in LNG production and a further increase in production costs. The relationship between the coke oven gas intake and LNG production under different load conditions can be seen in Figure 2 shown.

[0011] 2. Poor ability to resist component fluctuations. The existing process flow has poor resistance to CO 2 The CO content in coke oven gas is sensitive to fluctuations. Since the composition of coke oven gas is related to factors such as coal quality, coal blending, and coke quenching process, the CO content in coke oven gas is 2 , CO fluctuates greatly. Once it exceeds the processing capacity of the synthesis catalyst, the intake volume needs to be reduced, otherwise it will cause CO in the synthesis gas. 2 The content exceeds the standard and thus cannot enter the liquefaction section. Summary of the invention

[0012] One of the technical problems to be solved by the present invention is to provide a device for producing LNG from coke oven gas, which has stable operation and can ensure the output of LNG under low-load operation.

[0013] To solve the above technical problems, the device for producing LNG from coke oven gas of the present invention mainly comprises: a compression section, a desulfurization section, a synthesis section, a decarbonization section, a drying section, a liquefaction section and a storage and transportation section, wherein the decarbonization section is arranged between the synthesis section and the drying section.

[0014] The main equipment of the decarbonization section includes an absorption tower, a rich liquid flash tank, a synthesis gas separator, a lean and rich liquid heat exchanger, a regeneration tower, a reboiler, a storage tank, and a carbon dioxide separator; wherein:

[0015] The synthesis gas inlet of the absorption tower is connected to the synthesis section, the top gas phase outlet pipeline leads to the inlet of the synthesis gas separator, and the bottom liquid phase outlet is connected to the rich liquid inlet of the rich liquid flash tank;

[0016] The top gas phase outlet pipeline of the synthesis gas separator goes to the drying section, and the bottom liquid phase outlet pipeline leads to the rich liquid flash tank or storage tank;

[0017] The gas phase outlet pipeline of the rich liquid flash tank returns to the inlet of the compression section;

[0018] The inlet and outlet of the rich liquid heat exchange channel of the lean-rich liquid heat exchanger are respectively connected to the rich liquid outlet of the rich liquid flash tank and the top inlet of the regeneration tower; the inlet of the lean liquid heat exchange channel is connected to the lean liquid outlet at the bottom of the regeneration tower, and the outlet pipeline of the lean liquid heat exchange channel leads to the lean liquid inlet at the top of the absorption tower;

[0019] The reboiler is connected to the regeneration tower; the top gas phase outlet pipeline of the regeneration tower leads to the inlet of the carbon dioxide separator; the top gas phase outlet pipeline of the carbon dioxide separator returns to the inlet of the compression section, and the bottom liquid phase outlet pipeline leads to the storage tank; there is a submersible pump in the storage tank, and the outlet pipeline of the submersible pump merges into the top inlet pipeline of the regeneration tower.

[0020] Preferably, a synthesis gas cooler can be installed on the pipeline between the top gas phase outlet of the absorption tower and the inlet of the synthesis gas separator; a lean liquid cooler and a lean liquid pump can be installed on the pipeline between the lean liquid outlet of the lean-rich liquid heat exchanger and the top inlet of the absorption tower; and a carbon dioxide cooler is installed on the pipeline between the top gas phase outlet of the regeneration tower and the inlet of the carbon dioxide separator.

[0021] Preferably, solution filters may be connected to both ends of the lean liquid pump.

[0022] The synthesis section preferably adopts a two-stage synthesis reaction system, in which the synthesis reactors in the two-stage synthesis reaction system are only provided with a first-stage reactor and a second-stage reactor, and no third-stage reactor is provided.

[0023] The drying section preferably adopts an isobaric drying system, and more preferably adopts a three-tower isobaric drying system.

[0024] The second technical problem to be solved by the present invention is to provide a process method for producing LNG from coke oven gas based on the above-mentioned device, which includes seven process steps: compression, desulfurization, synthesis, decarbonization, drying, liquefaction and storage and transportation, and the decarbonization step is between the synthesis step and the drying step.

[0025] The decarburization step further comprises the following steps:

[0026] The synthesis gas from the synthesis section and the lean amine liquid are transferred in the absorption tower to remove the CO contained in the synthesis gas. 2 , then cooled, gas-liquid separation is performed, and the separated gas phase is sent to the drying section as synthesis gas;

[0027] The bottom of the absorption tower absorbs CO 2 The rich amine liquid is sent to the rich liquid flash tank for flash evaporation, and the flashed gas phase is sent back to the compression section entrance for repeated use. 2 regeneration;

[0028] For the regenerated CO 2 Cooling and gas-liquid separation are performed to separate the CO 2 Sent back to the entrance of the compression section for reuse.

[0029] Preferably, the high-temperature lean liquid discharged from the bottom of the regeneration tower is first heat exchanged and cooled, and then a portion of the lean liquid is sent to the top of the absorption tower, and the other portion of the lean liquid is filtered and sent back to the inlet of the lean liquid pump.

[0030] The synthesis step preferably adopts a two-stage synthesis reaction process; the drying step preferably adopts an isobaric drying process, and more preferably adopts a three-tower isobaric drying process.

[0031] Compared with the existing coke oven gas to LNG device and process, the coke oven gas to LNG device and process of the present invention has the following advantages and beneficial effects:

[0032] 1. Able to better adapt to CO in raw gas 2 The present invention reduces the synthesis reactor of the synthesis section from 3 sections to 2 sections, which relaxes the synthesis effect of the synthesis section. 2 The content of CO can be relaxed from the existing process requirement of less than 300 ppm to 3000-5000 ppm, thereby improving the device's resistance to CO 2The ability to resist interference from content fluctuations improves the stability of device operation.

[0033] 2. The present invention adds a decarbonization section and uses the alcohol amine method to remove CO from the synthesis gas. 2 , so that it reaches the liquefaction standard of 50PPm, and the CO removed 2 Return to the compression section entrance for reuse, thus achieving CO 2 Zero emissions.

[0034] 3. It can better adapt to the production operation of the device under low load conditions. The present invention improves the process of the drying section from molecular sieve variable pressure regeneration to isobaric drying. The regeneration of the drying tower is not affected by the flow rate of hydrogen-rich gas, and a linear relationship between the intake volume and the output is achieved (for example, 30% of the intake volume can produce 30% of LNG). This avoids the situation where the output of the device is far less than the intake volume under low load operation, thereby improving the economy of the device operation. In addition, the drying section no longer emits regeneration gas, and can also avoid environmental pollution caused by the emission of coke oven gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the existing process flow of producing LNG from coke oven gas;

[0036] Figure 2 This is a graph showing the relationship between the coke oven gas intake and LNG production under different load conditions in the existing coke oven gas to LNG process;

[0037] Figure 3 1 is a schematic diagram of a process flow of producing LNG from coke oven gas according to Example 1 of the present invention;

[0038] Figure 4 yes Figure 3 Schematic diagram of the device and process flow of the compression section;

[0039] Figure 5 yes Figure 3 Schematic diagram of the device and process flow of the desulfurization section;

[0040] Figure 6 yes Figure 3 Schematic diagram of the device and process flow of the synthesis section;

[0041] Figure 7 yes Figure 3 Schematic diagram of the device and process flow of the decarburization section;

[0042] Figure 8 yes Figure 3 Schematic diagram of the device and process flow of the drying section;

[0043] Fig. 9 yes Figure 3Schematic diagram of the device and process flow of the liquefaction section;

[0044] Fig.10 yes Figure 3 Schematic diagram of the equipment and process flow of the storage and transportation section.

[0045] The reference numerals in the figures are described as follows:

[0046] 101: First raw gas filter

[0047] 102: Second raw gas filter

[0048] 103: First raw gas compressor

[0049] 104: Second raw gas compressor

[0050] 105: The first de-oiling and naphthalene removal tower

[0051] 106: Second de-oiling and naphthalene removal tower

[0052] 107: The first crude desulfurization tower

[0053] 108: Second crude desulfurization tower

[0054] 109: The first synthesis gas compressor

[0055] 110: Second Syngas Compressor

[0056] 111: The third synthesis gas compressor

[0057] 201: First oil filter tank

[0058] 202: Second oil filter tank

[0059] 203: First pre-hydrogenation converter

[0060] 204: Second pre-hydrogenation converter

[0061] 205: Primary Hydroconverter

[0062] 206: The first medium temperature desulfurization tank

[0063] 207: Second medium temperature desulfurization tank

[0064] 208: Secondary Hydroconverter

[0065] 209: The first zinc oxide desulfurization tank

[0066] 210: Second zinc oxide desulfurization tank

[0067] 211: Steam heat exchanger

[0068] 212: Thermostat for the first section

[0069] 213: Product Cooler

[0070] 214: Second stage thermostat

[0071] 215: Nitrogen Cooler

[0072] 301: Synthetic start-up furnace

[0073] 302: CuO guard bed

[0074] 303: One-stage reactor

[0075] 304: Second stage reactor

[0076] 305: Steam drum

[0077] 306: Circulating air compressor

[0078] 307: Condensate separator

[0079] 308: Product separator

[0080] 309: Purified air cooler

[0081] 310: Purified gas preheater

[0082] 311: One-stage inlet heat exchanger

[0083] 312: Primary waste heat boiler

[0084] 313: Secondary waste heat boiler

[0085] 314: Deaerated water heat exchanger

[0086] 315: Circulating hot water heat exchanger

[0087] 316: Circulating gas heat exchanger

[0088] 317: Product Cooler

[0089] 318: Condensate pump

[0090] 401: Absorption Tower

[0091] 402: First solution filter

[0092] 403: Second solution filter

[0093] 404: First lean liquid pump

[0094] 405: Second lean liquid pump

[0095] 406: Lean liquid cooler

[0096] 407: Rich liquid flash tank

[0097] 408: Syngas Cooler

[0098] 409: Syngas Separator

[0099] 410: Lean and Rich Liquid Heat Exchanger

[0100] 411: Regeneration Tower

[0101] 412: Reboiler

[0102] 413: Underground Storage Tanks

[0103] 414: Carbon dioxide cooler

[0104] 415: Carbon dioxide separator

[0105] 416: Submersible pump

[0106] 501: Syngas precooler

[0107] 502: Purified gas separator

[0108] 503: Mercury removal tower

[0109] 504: First drying tower

[0110] 505: Second drying tower

[0111] 506: The third drying tower

[0112] 507: Regeneration gas separator

[0113] 508: Regeneration gas heater

[0114] 509: Purified gas precooler

[0115] 510: Regeneration gas cooler

[0116] 601: High-pressure distillation tower

[0117] 602: High-pressure tower liquid separation tank

[0118] 603: High pressure tower condenser

[0119] 604: Low temperature gas-liquid separation tank

[0120] 605: Low pressure distillation tower

[0121] 606: Low pressure liquid separation tank

[0122] 607: Low pressure condenser

[0123] 608: Low pressure evaporator

[0124] 609: Refrigeration heat exchanger

[0125] 610: Cryogenic refrigerant separation tank

[0126] 611: High temperature refrigerant separation tank

[0127] 612: Refrigerant compressor

[0128] 613: Refrigerant precooler

[0129] 614: Refrigerant separator tank

[0130] 615: Nitrogen precooler

[0131] 616: Nitrogen compressor

[0132] 701: LNG storage tank

[0133] 702: BOG compressor

[0134] 703: BOG heater

[0135] 704: LNG pump

[0136] 705: LNG tanker

[0137] FIT: Flow Indicating Transmitter

[0138] FIC: Flow Indicating Controller

[0139] PIC: Pressure Indicating Controller DETAILED DESCRIPTION

[0140] In order to have a more specific understanding of the technical content, characteristics and effects of the present invention, the technical solution of the present invention is further described in detail in conjunction with the accompanying drawings and specific embodiments.

[0141] Example 1

[0142] The coke oven gas to LNG device of this embodiment is as follows: Figure 3 As shown, it mainly includes compression section, desulfurization section, synthesis section, decarbonization section, isobaric drying section, liquefaction section and storage and transportation section. The equipment and process flow of each section are as follows:

[0143] (1) Compression section

[0144] The main equipment of the compression section is the same as that of the existing coke oven gas to LNG plant, such as Figure 4As shown, it mainly includes two raw gas filters, two raw gas compressors, two de-oiling and de-naphthalene towers, two rough desulfurization towers and three synthesis gas compressors in parallel. Among them, the raw gas inlet pipeline is respectively connected to the inlet of the two raw gas filters, and the outlet of each raw gas filter is respectively connected to the inlet of the two raw gas compressors. After the outlet pipelines of the two raw gas compressors are merged, they are divided into two ways to connect the bottom inlet of the two de-oiling and de-naphthalene towers respectively. After the top gas phase outlet pipelines of the two de-oiling and de-naphthalene towers are merged, they are divided into two ways to connect the bottom inlet of the two rough desulfurization towers respectively. After the top gas phase outlet pipelines of the two rough desulfurization towers are merged, they are divided into two ways, one way goes to the synthesis start-up furnace 301 of the synthesis section, and the other way is further divided into three ways to connect the inlets of the three synthesis gas compressors respectively. After the outlet pipelines of the three synthesis gas compressors are merged, they are divided into two ways, one way goes to the oil filter tank of the desulfurization section, and the other way goes to the desulfurization start-up furnace (not drawn in the figure).

[0145] Different from the existing coke oven gas to LNG device, the compression section of the device of this embodiment also merges two pipelines from the decarbonization section into the raw gas inlet pipeline. These two pipelines are respectively connected to the top gas phase outlet of the carbon dioxide separator 415 and the rich liquid flash tank 407.

[0146] The process flow of the compression section is:

[0147] The coke oven gas raw gas from the gas holder is mixed with the gas from the carbon dioxide separator 415 and the rich liquid flash tank 407 of the decarbonization section, filtered by the raw gas filter and compressed to 0.45Mpag by the raw gas compressor, and then enters the de-oiling and de-naphthalene tower and the rough desulfurization tower for pretreatment. After removing impurities such as tar, naphthalene, and inorganic sulfur, a small part goes to the synthesis start-up furnace 301 of the synthesis section as fuel gas, and most of it goes to the synthesis gas compressor. After the pressure is raised to about 2.2Mpag again, most of it enters the oil filter tank of the desulfurization section for fine desulfurization, and a small part goes to the desulfurization start-up furnace.

[0148] (2) Desulfurization Section

[0149] The desulfurization section is the same as the existing coke oven gas to LNG plant, such as Figure 5 As shown, it mainly includes two oil filter tanks, two pre-hydrogenation converters, two medium-temperature desulfurization tanks and two zinc oxide desulfurization tanks connected in parallel, as well as one primary hydroconverter 205, one secondary hydroconverter 208 and multiple heat exchangers. Among them:

[0150] The bottom inlets of the two oil filter tanks are respectively connected to the outlets of the synthesis gas compressors of the compression section. The top outlet pipelines of the two oil filter tanks are merged and divided into two routes. One pipeline is connected to the upper inlet of the primary hydroconverter 205, and the other pipeline is connected to the inlet of the steam heat exchanger 211. The outlet of the steam heat exchanger 211 is connected to the top inlet of the first interstage thermostat 212. The first interstage thermostat 212 has two outlets, the middle outlet is connected to the top inlet of the primary hydroconverter 205, and the bottom outlet is connected to the middle inlet of the product cooler 213. The product cooler 213 has two outlets, the top outlet is connected to the inlet of the purified gas cooler 309 of the synthesis section, and the middle outlet is connected to the inlet of the second interstage thermostat 214. The second interstage thermostat 214 has two outlets, the top outlet pipeline is divided into two routes and connected to the top inlets of the two medium-temperature desulfurization tanks, respectively, and the middle outlet pipeline is divided into two routes and connected to the top inlets of the two pre-hydroconverters, respectively.

[0151] The bottom outlet pipelines of the two pre-hydrogenation converters are connected to the inlet of the middle of the first interstage thermostat 212 after merging. The bottom outlet of the primary hydroconverter 205 is connected to the bottom inlet of the second interstage thermostat 214. The bottom outlet pipelines of the two medium-temperature desulfurization tanks are connected to the top inlet of the secondary hydroconverter 208 after merging. The bottom outlet pipelines of the secondary hydroconverter 208 are divided into two routes and connected to the top inlets of the two zinc oxide desulfurization tanks respectively. The bottom outlet pipelines of the two zinc oxide desulfurization tanks are connected to the bottom inlet of the product cooler 213 after merging.

[0152] Since the activity of the catalyst in this section has very high temperature requirements, multiple heat exchangers are set after the oil filter tank so that the medium temperature can be adjusted through the heat exchanger before entering each reactor to meet the requirements of the catalyst.

[0153] The process flow of the desulfurization section is:

[0154] The high-pressure coke oven gas from the synthesis gas compressor of the compression section first enters the oil filter tank to prevent the compression section from carrying oil to damage the hydrogenation catalyst, and then after hydrogenation conversion in the pre-hydrogenation converter and the first-stage hydrogenation converter 205, most of the organic sulfur in the coke oven gas is converted into inorganic sulfur, and then the inorganic sulfur is removed through the medium-temperature desulfurization tank, and then the organic sulfur is converted and removed again through the second-stage hydrogenation converter 208 and the zinc oxide desulfurization tank, and finally the total sulfur content in the product gas of the desulfurization section is less than 0.1PPm. The heated gas from the desulfurization start-up furnace is collected and enters the nitrogen cooler 215 after passing through each reactor, and goes to the synthesis gas compressor of the compression section after heat exchange.

[0155] (3) Synthesis Section

[0156] The difference between the synthesis section and the synthesis section of the existing coke oven gas to LNG device is that the reactor is changed from three stages to two stages, and the equipment and pipelines related to the three-stage reactor are reduced accordingly. Figure 6 As shown, the synthesis section of the device of this embodiment mainly includes a synthesis start-up furnace 301, a CuO guard bed 302, a first-stage reactor 303, a second-stage reactor 304, a steam drum 305, a circulating gas compressor 306, a condensate separator 307, a product separator 308, a purified gas cooler 309, a purified gas preheater 310, a first-stage inlet heat exchanger 311, a first-stage waste heat boiler 312, a second-stage waste heat boiler 313, a deoxygenated water heat exchanger 314, a circulating hot water heat exchanger 315, a circulating gas heat exchanger 316, a product cooler 317 and a condensate pump 318. Among them:

[0157] The inlet of the purified gas cooler 309 is connected to the top outlet of the product cooler 213 of the compression section, and the outlet of the purified gas cooler 309 is connected to the top inlet of the CuO guard bed 302. The bottom outlet of the CuO guard bed 302 is connected to the middle inlet of the purified gas preheater 310. The purified gas preheater 310 has two outlets, and the middle outlet pipeline is divided into two routes, one route is connected to the middle inlet of the first-stage inlet heat exchanger 311, and the other route is connected to the top inlet of the second-stage reactor 304 after merging with the top outlet pipeline of the first-stage inlet heat exchanger 311; the bottom outlet of the purified gas preheater 310 is connected to the bottom inlet of the circulating gas heat exchanger 316. The middle outlet of the first-stage inlet heat exchanger 311 is connected to the top inlet of the first-stage reactor 303. The lower outlet of the first-stage reactor 303 is connected to the middle inlet of the primary waste heat boiler 312. The primary waste heat boiler 312 has two outlets, the top outlet is connected to an inlet at the bottom of the drum 305 , and the middle outlet is connected to the bottom inlet of a section inlet heat exchanger 311 .

[0158] The lower outlet of the second stage reactor 304 is connected to the middle inlet of the secondary waste heat boiler 313. The top outlet of the secondary waste heat boiler 313 is connected to another inlet at the bottom of the drum 305. The middle outlet of the secondary waste heat boiler 313 is connected to the bottom inlet of the deoxygenated water heat exchanger 314.

[0159] The two outlets at the bottom of the drum 5 are respectively connected to the bottom inlets of the primary waste heat boiler 312 and the secondary waste heat boiler 313. The outlet pipeline at the top of the drum 5 merges into the pipeline between the purified gas preheater 310 and a section of the inlet heat exchanger 311.

[0160] The top outlet of the deoxygenated water heat exchanger 314 is connected to the top inlet of the purified gas preheater 310 .

[0161] The middle outlet pipeline of the circulating gas heat exchanger 316 is divided into two routes, one route is connected to the pipeline between the purified gas preheater 310 and the first inlet heat exchanger 311, and the other route is connected to the synthesis start-up furnace 301. The top outlet of the circulating gas heat exchanger 316 is connected to the bottom inlet of the circulating hot water heat exchanger 315.

[0162] The top outlet of the circulating hot water heat exchanger 315 is connected to the top inlet of the condensate separator 307. The top of the condensate separator 307 has two outlets, one of which is connected to the top inlet of the circulating gas compressor 306, and the other is connected to the inlet of the product cooler 317. The bottom outlet pipeline of the condensate separator 307 is connected to the pipeline between the purified gas preheater 310 and the first inlet heat exchanger 311 after passing through the condensate pump 318.

[0163] The bottom outlet of the circulating gas compressor 306 is connected to the middle inlet of the circulating gas heat exchanger 316 .

[0164] The outlet of the product cooler 317 is connected to the inlet of the product separator 308. The top outlet pipeline of the product separator 308 goes to the absorption tower 401 of the decarbonization section, and the bottom outlet pipeline leads to the sewage system.

[0165] The heating gas outlet pipeline of the synthesis start-up furnace 301 is divided into three routes and respectively merged into the top inlet pipelines of the CuO guard bed 302, the first-stage reactor 303 and the second-stage reactor 304.

[0166] The process flow of the synthesis section is as follows:

[0167] The coke oven gas from the desulfurization section and after fine desulfurization first enters the purified gas cooler 309, where the temperature of the coke oven gas is reduced to about 180°C by circulating hot water, and then enters the CuO protection bed 302 to prevent sulfur poisoning of the synthesis catalyst, and then enters the purified gas preheater 310. After the temperature is heated to about 220°C, the medium is divided into two parts, one part (40% to 45%) is mixed with the circulating gas and then enters the first inlet heat exchanger 311. After heat exchange with the high-temperature gas from the first-stage waste heat boiler 312 in the first inlet heat exchanger 311, the temperature rises to about 300°C, and then enters the first reactor 303. In the first reactor 303, CO 2 , CO and H 2 The CH was synthesized under the action of catalyst 4 The syngas after the reaction, after recovering heat through the primary waste heat boiler 312 and the first inlet heat exchanger 311, is mixed with another part of the preheated coke oven gas (55% to 60%), and enters the second stage reactor 304 at a temperature of about 300°C. In the second stage reactor 304, CO 2 (content is 3000~5000PPm), CO and H 2 The CH was synthesized under the action of catalyst4 , and releases heat at the same time, and then recovers heat through the secondary waste heat boiler 313, deoxygenated water heat exchanger 314, purified gas preheater 310, circulating gas heat exchanger 316 and circulating hot water heat exchanger 315 in sequence, and after the temperature drops to about 110°C, it enters the condensate separator 307 to separate the water in the medium. Part of the gas phase is pressurized by the circulating gas compressor 306 and preheated by the circulating gas heat exchanger 316 as circulating gas, and then enters the first inlet heat exchanger 311; the other part is cooled to about 40°C by the product cooler 317, and then separated into gas and liquid by the product separator 308, and the gas phase enters the absorption tower 401 of the decarbonization section, and the liquid phase goes to the sewage system.

[0168] A portion of the liquid phase separated by the condensate separator 307 is sent to the first inlet heat exchanger 311 through the condensate pump 318 to ensure that the water content of the coke oven gas entering the first reactor 303 is about 6%. The excess portion is cooled by a condensate cooler (not shown in the figure) and then sent to the sewage system together with the liquid phase separated by the product separator 308.

[0169] (4) Decarburization section

[0170] The decarburization section is arranged between the synthesis section and the drying section, and is an additional section of the device of this embodiment. Its main equipment is as follows Figure 7 As shown, it mainly includes an absorption tower 401, two solution filters connected in series, two lean liquid pumps connected in parallel, a rich liquid flash tank 407, a synthesis gas separator 409, a lean and rich liquid heat exchanger 410, a regeneration tower 411, a reboiler 412, an underground storage tank 413, a carbon dioxide separator 415 and three coolers. Among them:

[0171] The lower inlet of the absorption tower 401 is connected to the top outlet of the product separator 308 of the synthesis section, the top gas phase outlet of the absorption tower 401 is connected to the inlet of the synthesis gas cooler 408, and the bottom liquid phase outlet is connected to the bottom inlet of the rich liquid flash tank 407.

[0172] The middle inlet of the synthesis gas separator 409 is connected to the outlet of the synthesis gas cooler 408 , the top gas phase outlet leads to the drying section, and the bottom liquid phase outlet is connected to the top inlet of the rich liquid flash tank 407 .

[0173] The top outlet pipeline of the rich liquid flash tank 407 leads to the raw gas filter of the compression section, and the bottom outlet is connected to the inlet of the rich liquid heat exchange channel at the bottom of the lean-rich liquid heat exchanger 410.

[0174] The top of the lean-rich liquid heat exchanger 410 has two outlets, one outlet is connected to the inlet of the lean liquid cooler 406 , and the other outlet is connected to the top inlet of the regeneration tower 411 .

[0175] The outlet pipeline of the lean liquid cooler 406 is divided into two routes, each of which is connected to the inlet of the two lean liquid pumps. The outlet pipelines of the two lean liquid pumps are merged and then divided into two routes, one of which is connected to the top inlet of the absorption tower 401, and the other is connected to the bottom inlet of the first solution filter 402. The top outlet of the first solution filter 402 is connected to the bottom inlet of the second solution filter 403. The top outlet pipeline of the second solution filter 403 merges into the inlet pipeline of the lean liquid cooler 406.

[0176] The gas phase outlet pipeline at the top of the regeneration tower 411 passes through the carbon dioxide cooler 414 and leads to the middle inlet of the carbon dioxide separator 415. There are two liquid phase outlets at the bottom of the regeneration tower 411, one outlet is connected to the bottom inlet of the reboiler 412, and the other outlet is connected to the lean liquid heat exchange channel inlet at the bottom of the lean-rich liquid heat exchanger 410. The top outlet of the reboiler 412 is connected to the lower inlet of the regeneration tower 411.

[0177] The top gas phase outlet pipeline of the carbon dioxide separator 415 leads to the raw gas filter of the compression section, and the bottom liquid phase outlet is connected to the inlet of the underground storage tank 413. A submersible pump 416 is arranged in the underground storage tank 413, and the outlet pipeline of the submersible pump 416 is connected to the top inlet pipeline of the regeneration tower 411.

[0178] The process flow of the decarburization section is as follows:

[0179] The synthesis gas from the product separator 308 of the synthesis section enters the absorption tower 401 from the bottom of the absorption tower 401, and performs mass and heat transfer with the lean amine liquid from top to bottom to remove the CO contained in the synthesis gas. 2 . Removal of CO 2 After the synthesis gas is cooled by the synthesis gas cooler 408 and separated by the synthesis gas separator 409, the gas phase enters the drying section and the liquid phase enters the rich liquid flash tank 407 (in other embodiments, it can also be discharged into the underground storage tank 413).

[0180] Absorbing CO 2 The amine liquid is transformed from lean liquid to rich liquid, and enters the rich liquid flash tank 407 from the bottom of the absorption tower 401 after throttling and pressure reduction. The flashed gas phase returns to the inlet of the raw gas filter of the compression section for reuse. The liquid phase is preheated by the lean and rich liquid heat exchanger 410 and enters the regeneration tower 411 from the top to perform mass and heat transfer with the high-temperature steam generated by the reboiler 412 from the bottom, thereby removing CO in the rich liquid. 2 The CO 2 After being cooled by the carbon dioxide cooler 414 and separated by the carbon dioxide separator 415, CO 2 The raw gas is returned to the inlet of the raw gas filter of the compression section for reuse, and the liquid phase is discharged into the underground storage tank 413.

[0181] After being cooled by the lean-rich liquid heat exchanger 410 and the lean liquid cooler 406, a part of the high-temperature lean liquid discharged from the bottom of the regeneration tower 411 is sent to the top of the absorption tower 401 by the lean liquid pump, and the other part is filtered by the solution filter and returned to the lean liquid pump inlet.

[0182] (5) Isobaric Drying Section

[0183] The drying process of the device of this embodiment adopts an isobaric drying process. The main equipment of the drying process is as follows: Figure 8 As shown, it mainly includes a synthesis gas precooler 501, a purified gas separator 502, a mercury removal tower 503, three drying towers, a regeneration gas separator 507, a regeneration gas heater 508, a purified gas precooler 509, and a regeneration gas cooler 510. Among them:

[0184] The inlet of the syngas precooler 501 is connected to the outlet of the decarbonization section syngas separator 409, and the outlet of the syngas precooler 501 is connected to the upper inlet of the purified gas separator 502. The bottom liquid phase outlet pipeline of the purified gas separator 502 leads to the sewage system, and the top gas phase outlet is connected to the bottom inlet of the demercuration tower 503. The top gas phase outlet pipeline of the demercuration tower 503 is divided into two routes, one of which is further divided into two routes respectively connected to the bottom inlets of the first drying tower 504 and the second drying tower 505, and the other route is further divided into multiple branches leading to the three drying towers and the regeneration gas cooler 510 respectively.

[0185] The gas phase outlet pipelines at the top of the first drying tower 504 and the second drying tower 505 are combined and then sent to the liquefaction section through the purified gas precooler 509.

[0186] The top gas phase outlet pipeline of the regeneration gas separator 507 is connected to the bottom inlet pipelines of the first drying tower 504 and the second drying tower 505. The bottom outlet pipeline of the regeneration gas separator 507 leads to the sewage system.

[0187] The process flow of the isobaric drying section is as follows:

[0188] The synthesis gas from the synthesis gas separator 409 of the decarbonization section is cooled by the synthesis gas precooler 501, and its temperature drops to about 35°C. It enters the purified gas separator 502 to separate the moisture in the synthesis gas, and the liquid phase is discharged into the sewage system. After the gas phase passes through the demercuration tower 503, most of it enters the first drying tower 504 and / or the second drying tower 505, and after the water content is reduced to 1PPm in the drying tower, it enters the purified gas precooler 509 to reduce the temperature to 12°C and is sent to the liquefaction section; a small part is used as regeneration gas, and firstly the drying tower is subjected to cold blowing and hot blowing operations, and then after being cooled by the regeneration gas cooler 510, it enters the regeneration gas separator 507 to separate the moisture in the regeneration gas, and the gas phase returns to the entrance of the first drying tower 504 and / or the second drying tower 505, and the liquid phase is discharged into the sewage system.

[0189] (6) Liquefaction Section

[0190] The main equipment of the liquefaction section is the same as the existing coke oven gas to LNG plant, such as Fig. 9 As shown, it mainly includes a high-pressure distillation tower 601, a high-pressure tower liquid separator 602, a low-temperature gas-liquid separator 604, a low-pressure distillation tower 605, a low-pressure tower liquid separator 606, a refrigeration heat exchanger 609, a low-temperature refrigerant separator 610, a high-temperature refrigerant separator 611, a refrigerant compressor 612, a refrigerant precooler 613, a refrigerant liquid separator 614, a nitrogen precooler 615, and a nitrogen compressor 616. Among them:

[0191] Condensers are respectively provided at the top of the high-pressure distillation tower 601 and the low-pressure distillation tower 605. An evaporator is provided at the bottom of the low-pressure distillation tower 605. The bottom liquid phase outlet of the high-pressure distillation tower 601 is connected to the middle inlet of the low-pressure distillation tower 605. The lower inlet of the high-pressure tower liquid separator 602 is connected to the bottom outlet of the high-pressure tower condenser 603; the bottom outlet of the high-pressure tower liquid separator 602 is connected to the inlet of the distillation section of the high-pressure distillation tower 601. The outlet at the top of the distillation section of the high-pressure distillation tower 601 is connected to the top inlet of the high-pressure tower condenser 603. The top gas phase outlet of the low-temperature gas-liquid separation tank 604 is connected to the lower inlet of the high-pressure distillation tower 601, and the bottom liquid phase outlet is connected to the bottom inlet of the distillation section of the low-pressure distillation tower 605.

[0192] The bottom liquid phase outlet of the low-pressure tower separator 606 is connected to the top inlet of the distillation section of the low-pressure distillation tower 605. The top outlet of the distillation section of the low-pressure distillation tower 605 is connected to the top inlet of the low-pressure tower condenser 607. The bottom outlet of the low-pressure tower condenser 607 is connected to the lower inlet of the low-pressure tower separator 606.

[0193] The cooling heat exchanger 609 is provided with 11 heat exchange channels. The inlets of the L1, L5, L6, and L8 channels are arranged at the top of the cooling heat exchanger 609; the inlets of the L2-L4 and L11 channels are arranged at the bottom of the cooling heat exchanger 609; the L7 channel has two inlet pipelines, and the two inlets are arranged at the upper part of the cooling heat exchanger 609; the inlets of the L9 and L10 channels are arranged at the lower part of the cooling heat exchanger 609. The outlet of the L1 channel is arranged in the middle part of the cooling heat exchanger 609; the outlets of the L2-L4 and L7 channels are arranged at the top of the cooling heat exchanger 609; the outlets of the L5, L6, L9, and L10 channels are arranged at the bottom of the cooling heat exchanger 609; the outlet of the L8 channel is arranged at the upper part of the cooling heat exchanger 609; and the outlet of the L11 channel is arranged in the middle part of the cooling heat exchanger 609.

[0194] The inlet of the L1 channel is connected to the outlet of the drying section purified gas precooler 509 ; the outlet of the L1 channel is connected to the top inlet of the low-pressure evaporator 608 .

[0195] The inlet of the L2 channel is connected to the top gas phase outlet of the high-pressure tower separator 602; the outlet pipeline of the L2 channel leads to the synthesis gas precooler 501.

[0196] The inlet of the L3 channel is connected to the top gas phase outlet of the low-pressure tower separator tank 606; the outlet pipeline of the L3 channel leads to the venting system.

[0197] The inlet pipeline of the L4 channel is divided into two routes, which are respectively connected to the top gas phase outlets of the high-pressure distillation tower 601 and the low-pressure distillation tower 605; the outlet of the L4 channel is connected to the inlet of the nitrogen compressor 616.

[0198] The inlet of the L5 channel is connected to the outlet of the nitrogen precooler 615; the outlet of the L5 channel is divided into two paths and connected to the top nitrogen inlets of the low-pressure distillation tower 605 and the high-pressure distillation tower 601 respectively.

[0199] The inlet of the L6 channel is connected to the top gas phase outlet of the refrigerant liquid separation tank 614 ; the outlet of the L6 channel is connected to the middle inlet of the low-temperature refrigerant separation tank 610 .

[0200] The L7 channel has two inlet pipelines, which are respectively connected to the top gas phase outlet and the bottom liquid phase outlet of the high-temperature refrigerant separation tank 611; the outlet of the L7 channel is connected to the inlet of the refrigerant compressor 612.

[0201] The inlet of the L8 channel is connected to the bottom liquid phase outlet of the refrigerant separation tank 614 ; the outlet pipeline of the L8 channel and the outlet pipeline of the L11 channel are merged and lead to the inlet of the high-temperature refrigerant separation tank 611 .

[0202] The inlet of the L9 channel is connected to the bottom liquid phase outlet of the low-pressure distillation tower 605 ; the outlet pipeline of the L9 channel leads to the LNG storage tank 701 .

[0203] The inlet of the L10 channel is connected to the bottom outlet of the low-pressure tower evaporator 608 ; the outlet of the L10 channel is connected to the top inlet of the low-temperature gas-liquid separation tank 604 .

[0204] The L11 channel has two inlet pipelines, which are respectively connected to the top gas phase outlet and the bottom liquid phase outlet of the cryogenic refrigerant separation tank 610 .

[0205] The outlet of the refrigerant compressor 612 is connected to the inlet of the refrigerant precooler 613. The outlet of the refrigerant precooler 613 is connected to the top inlet of the refrigerant liquid separation tank 614.

[0206] The inlet of the nitrogen precooler 615 is connected to the outlet of the nitrogen compressor 616 .

[0207] The process flow of the liquefaction section is as follows:

[0208] The dry synthesis gas from the drying section purified gas precooler 509 enters the L1 channel of the refrigeration heat exchanger 609 to exchange heat with the mixed refrigerant and is distilled at different temperatures and pressures to separate the H 2 and N 2 The heat required by the distillation tower comes from the synthesis gas itself, and the cold is provided by the nitrogen cycle (the nitrogen separated by distillation is sent from the top of the distillation tower to the L4 channel of the refrigeration heat exchanger 609, and after heat exchange, it passes through the nitrogen compressor 616 and the nitrogen precooler 615, and is sent to the L5 channel of the refrigeration heat exchanger 609 for heat exchange, and then returns to the distillation tower). The nitrogen-rich gas produced at the top of the low-pressure tower separator tank 606 is discharged into the flare after the cold is recovered by the refrigeration heat exchanger 609. The hydrogen-rich gas at the top of the high-pressure tower separator tank 602 is discharged into the flare after passing through the synthesis gas precooler 501. The LNG produced at the bottom of the low-pressure distillation tower 605 enters the LNG storage tank 701 of the storage and transportation section after throttling and pressure reduction.

[0209] (7) Storage and transportation section

[0210] The main equipment of the storage and transportation section is the same as the existing coke oven gas to LNG device, such as Fig.10 As shown, it mainly includes LNG storage tank 701, BOG compressor 702, BOG heater 703, LNG pump 704, and LNG tanker 705. Among them:

[0211] The inlet of the LNG storage tank 701 is connected to the bottom LNG outlet of the liquefaction section refrigeration heat exchanger 608. The bottom outlet of the LNG storage tank 701 is connected to the inlet of the LNG tanker 705 through the LNG pump 704, and the top outlet is connected to the inlet of the BOG heater 703.

[0212] The outlet pipeline of the LNG tanker 705 merges into the pipeline between the LNG storage tank 701 and the BOG heater 703 .

[0213] The outlet of the BOG heater 703 is connected to the inlet of the BOG compressor 702. The outlet of the BOG compressor 702 is connected to the pipeline between the syngas separator 409 and the syngas precooler 501.

[0214] The process flow of the storage and transportation section is as follows:

[0215] After the LNG from the liquefaction section refrigeration heat exchanger 608 enters the LNG storage tank 701, it is sent to the LNG tank truck 705 through the LNG pump 704. The BOG (flash gas) generated by the LNG storage tank 701 and the BOG generated by the LNG tank truck 705 are mixed, heated by the BOG heater 703 and compressed by the BOG compressor 702 in turn, and returned to the synthesis gas precooler 501 at the entrance of the drying section to be liquefied again.

[0216] The above embodiments are merely feasible or preferred embodiments of the present invention and are used to illustrate the present invention rather than to limit the scope of the patent application of the present invention. Therefore, all equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope covered by the patent of the present invention.

Claims

1. A coke oven gas to LNG device, comprising a compression section, a desulfurization section, a synthesis section, a drying section, a liquefaction section and a storage and transportation section, characterized in that: There is also a decarbonization section between the synthesis section and the drying section.

2. The device according to claim 1, characterized in that The decarbonization section includes an absorption tower, a rich liquid flash tank, a synthesis gas separator, a lean and rich liquid heat exchanger, a regeneration tower, a reboiler, a storage tank, and a carbon dioxide separator; wherein: The synthesis gas inlet of the absorption tower is connected to the synthesis section, the top gas phase outlet pipeline leads to the inlet of the synthesis gas separator, and the bottom liquid phase outlet is connected to the rich liquid inlet of the rich liquid flash tank; The top gas phase outlet pipeline of the synthesis gas separator goes to the drying section, and the bottom liquid phase outlet pipeline leads to the rich liquid flash tank or storage tank; The gas phase outlet pipeline of the rich liquid flash tank returns to the inlet of the compression section; The inlet and outlet of the rich liquid heat exchange channel of the lean-rich liquid heat exchanger are respectively connected to the rich liquid outlet of the rich liquid flash tank and the top inlet of the regeneration tower; the inlet of the lean liquid heat exchange channel is connected to the lean liquid outlet at the bottom of the regeneration tower, and the outlet pipeline of the lean liquid heat exchange channel leads to the lean liquid inlet at the top of the absorption tower; The reboiler is connected to the regeneration tower; the top gas phase outlet pipeline of the regeneration tower leads to the inlet of the carbon dioxide separator; the top gas phase outlet pipeline of the carbon dioxide separator returns to the inlet of the compression section, and the bottom liquid phase outlet pipeline leads to the storage tank; there is a submersible pump in the storage tank, and the outlet pipeline of the submersible pump merges into the top inlet pipeline of the regeneration tower.

3. The device according to claim 2, characterized in that A synthesis gas cooler is arranged on the pipeline between the top gas phase outlet of the absorption tower and the inlet of the synthesis gas separator; a lean liquid cooler and a lean liquid pump are arranged on the pipeline between the lean liquid outlet of the lean-rich liquid heat exchanger and the top inlet of the absorption tower; and a carbon dioxide cooler is arranged on the pipeline between the top gas phase outlet of the regeneration tower and the inlet of the carbon dioxide separator.

4. The device according to claim 3, characterized in that Solution filters are connected to both ends of the lean liquid pump.

5. The device according to claim 1, characterized in that The synthesis section adopts a two-stage synthesis reaction system, and the synthesis reactor in the two-stage synthesis reaction system is only provided with a first-stage reactor and a second-stage reactor.

6. The device according to claim 1, characterized in that The drying section adopts an isobaric drying system.

7. A process for producing LNG from coke oven gas based on the device according to any one of claims 1 to 6, the process comprising the steps of compression, desulfurization, synthesis, drying, liquefaction and storage and transportation, characterized in that: A decarburization step is also included between the synthesis step and the drying step.

8. The process according to claim 7, characterized in that: The decarburization step comprises: The synthesis gas from the synthesis section and the lean amine liquid are subjected to mass and heat transfer in the absorption tower to remove the CO2 contained in the synthesis gas, and then cooled and separated into gas and liquid. The separated gas phase is sent to the drying section as the synthesis gas; The rich amine liquid at the bottom of the absorption tower that has absorbed CO2 is sent to the rich liquid flash tank for flash evaporation, and the flashed gas phase is sent back to the inlet of the compression section for reuse, and the liquid phase is preheated for CO2 regeneration; The regenerated CO2 is cooled and separated into gas and liquid, and the separated CO2 is sent back to the entrance of the compression section for reuse.

9. The process according to claim 8, characterized in that: The high-temperature lean liquid discharged from the bottom of the regeneration tower is heat exchanged and cooled, and then a part of the lean liquid is sent to the top of the absorption tower, and the other part of the lean liquid is filtered and sent back to the inlet of the lean liquid pump.

10. The process according to claim 7, characterized in that: The synthesis step adopts a two-stage synthesis reaction process, and the drying step adopts an isobaric drying process.

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