Process for preparing liquefied natural gas from coke-oven gas with transformation methanation-free circulation loop

Abstract

The invention belongs to the field of efficient and clean utilization of coke-oven gas, and particularly relates to a process for preparing liquefied natural gas from coke-oven gas with a transformation methanation-free circulation loop. The process comprises the following steps: coke-oven gas is subjected to compression purification, hydrodesulfurization and wide temperature shift, then enters a methanation unit and passes through a plurality of methanation reactors connected in series, all carbon-containing compounds in shift gas are converted into methane, and methane-rich gas is subjected to cryogenic separation to obtain an LNG product. The process is simple, easy to operate, free of methanation recycle gas, good in process reliability, low in comprehensive energy consumption and large in operation flexibility, and the system is suitable for large-scale methanation production.

Description

Technical Field

[0001] The invention belongs to the field of efficient and clean utilization of coke oven gas, and specifically relates to a process for producing liquefied natural gas from coke oven gas with a conversion non-methanization circulation loop. Background Art

[0002] 1. Technology for producing liquefied natural gas from coke oven gas with a circulation loop

[0003] The conventional process of producing liquefied natural gas from coke oven gas is that the coke oven gas is directly fed into the methanation reactor after being pre-treated, compressed, purified and desulfurized. In order to control the temperature of the methanation reaction and ensure the depth of the methanation reaction, the methanated gas is pressurized and returned to the raw coke oven gas to dilute the CO+CO2 content in the gas entering the methanation reactor and reduce the outlet temperature of the methanation reactor. For example, the patent "A method for preparing synthetic natural gas using coke oven gas" (patent number CN1919985 A) and the patent "A methanation reaction process for preparing synthetic natural gas using coke oven gas" (patent number CN101508922 A) both return a portion of the methanated gas to the coke oven gas to control the CO+CO2 content entering the methanation reactor to ≤3.5%, and the gas temperature after methanation to ≤530°C.

[0004] 2. Technology for producing liquefied natural gas from coke oven gas without circulation loop

[0005] Among the existing technologies for producing liquefied natural gas from coke oven gas without a circulation loop, Patent ① "A methanogenic process for preparing SNG or LNG without circulation gas using coke oven gas" (Patent No. CN 103409187 A) is to divide the coke oven gas into several streams and enter several series-connected methanogenic main reactors respectively, dilute the coke oven gas entering the first methanogenic main reactor with by-product water vapor, cool the methanogenic gas after the last methanogenic main reactor, condense and separate water, and then enter a methanogenic secondary reactor to methanogenically react the residual CO and CO2, and then send them for separation or liquefaction to obtain SNG or LNG. The process described in this patent does not have a conversion unit to adjust the content of CO, CO2, and H2. It dilutes the concentration of coke oven gas by adding a large amount of water vapor (20% to 50% of the coke oven gas flow) to control the reaction temperature rise, which increases the water vapor supplement and increases the production cost.

[0006] Patent ② "Non-circulating complete methanation integrated process and system" (patent number CN 108774554 A), this patent is to divide the crude coal gas after oil removal and dust removal into two streams, one of which is subjected to conversion, sulfur-resistant methanation reaction and purification to obtain a reaction gas with a methane dry content of 10-20 mol%, which is then sent to a multi-stage methanation reaction unit in series for methanation reaction to obtain a synthetic natural gas with a methane dry content greater than 95 mol%; the other crude coal gas is purified to obtain purified gas, which is further divided into multiple streams and respectively mixed into the inlet reaction gas of the multi-stage methanation reaction unit to participate in the subsequent methanation reaction. The process described in this patent is to divide the purified crude coal gas into two streams after oil removal, one of which is subjected to sulfur-resistant conversion and sulfur-resistant methanation, and then mixed with another desulfurized coal gas, and then subjected to multi-stage methanation to obtain methane-rich gas. The core of this patent is the need for a sulfur-resistant methanation catalyst. However, the nickel-based methanation catalysts currently accepted in the market are susceptible to catalyst poisoning by impurities such as sulfur. From the current research progress on methanation catalysts, it is difficult to find an alternative element that is sulfur-resistant and can ensure a good methanation reaction. Summary of the invention

[0007] The object of the present invention is to provide a process for producing liquefied natural gas from coke oven gas with a conversion and non-methanization circulation loop. In the process, the coke oven gas is subjected to compression and purification, hydrodesulfurization, conversion, methanation, cryogenic separation and other process units to obtain a liquefied natural gas product. The process is simple, easy to operate, has no methanation circulation gas, has good process reliability, low comprehensive energy consumption, and high operational flexibility, and is suitable for large-scale methanation production.

[0008] In order to achieve the above invention object, the specific technical solution of the present invention is:

[0009] A process for producing liquefied natural gas from coke oven gas with a shift-free methanation circulation loop comprises the following steps:

[0010] 1) Purification: pre-treating the coke oven gas to obtain preliminarily purified coke oven gas;

[0011] 2) Hydrodesulfurization: The coke oven gas that has been initially purified is subjected to hydrodesulfurization treatment to remove sulfides in the coke oven gas;

[0012] 3) Conversion: Set up conversion and waste heat recovery units to adjust the ratio of H2, CO, and CO2 in the coke oven gas to obtain conversion gas;

[0013] 4) Methanation: multiple adiabatic methanation reactors are set up to convert all CO, CO2 and high-carbon hydrocarbons in the conversion gas into methane to obtain methane-rich gas;

[0014] 5) Cryogenic separation: Use mixed refrigerant to perform refrigeration separation process on methane-rich gas to obtain LNG product.

[0015] The specific steps are as follows:

[0016] 1) Compression and purification

[0017] The coke oven gas from coking is pre-treated, and the macromolecular impurities in the coke oven gas are initially removed by gas-liquid separation or adsorption. After entering the gas cabinet for buffering and storage, it enters the compressor for compression and is then sent to the purification process unit. The purification process unit mainly removes impurities such as tar, naphthalene, ammonia, and hydrogen cyanide in the coke oven gas to the process requirements by means of washing, gas-liquid separation, and adsorption. The purified coke oven gas is sent to the hydrodesulfurization unit.

[0018] As a preferred embodiment of the present application, the coke oven gas is compressed from normal pressure to 1.0-4.5 MPaG by means of a compressor.

[0019] 2) Hydrodesulfurization

[0020] After being preheated, the purified coke oven gas enters the pre-hydrogenation reactor and the primary hydrogenation reactor in sequence to remove oxygen from the coke oven gas and convert 90% of the organic sulfur into inorganic sulfur. It then enters the primary medium-temperature zinc oxide tank to remove hydrogen sulfide from the coke oven gas. The coke oven gas from the primary medium-temperature zinc oxide tank then enters the secondary hydrogenation reactor to further convert organic sulfur into inorganic sulfur. The sulfur in the coke oven gas is then removed through the secondary medium-temperature zinc oxide tank. The desulfurized gas is sent to the conversion unit.

[0021] As a preferred embodiment of the present application, after the hydrodesulfurization step, the sulfur content in the coke oven gas is removed to below 0.1 ppmv.

[0022] 3) Transformation

[0023] After waste heat recovery and the addition of appropriate water vapor, the desulfurized gas enters the sulfur-free adiabatic wide temperature shift reactor, with the inlet temperature shifted to 190-240°C and the outlet temperature shifted to 270-330°C, and all directly enters the downstream methanation reactor.

[0024] As a preferred embodiment of the present application, the dry basis content of carbon monoxide in the converted gas is 0.2V% to 1.5V%.

[0025] 4) Methanation

[0026] The conversion gas passes through 1 to 3 sulfur-free adiabatic methanation reactors (high-temperature section methanation reaction) at one time. A steam generator is arranged at the outlet of each methanation reactor to recover heat and produce by-product steam. After the last methanation reactor, the methanogenic gas is cooled to room temperature to separate water, and then enters 1 to 2 sulfur-free adiabatic methanation reactors (low-temperature section methanation reaction) to carry out methanation reaction on residual CO and CO2, and after heat recovery, cooling and water separation, methane-rich gas is obtained, whose main components are hydrogen, methane and nitrogen.

[0027] As a preferred embodiment of the present application, the methanation inlet temperature is 250-330° C., the high temperature section methanation outlet temperature is 500-650° C., and the low temperature section methanation outlet temperature is 270-450° C. The main components of the methane-rich gas are hydrogen, methane, and nitrogen, including 10V%-30V% hydrogen, 60V%-85V% methane, and 3V%-8V% nitrogen.

[0028] 5) Cryogenic separation

[0029] After cryogenic pretreatment, the methane-rich gas is removed of moisture, dust and other trace harmful impurities before entering the cold box. The cold box cooling capacity is provided by mixed refrigerant and compressor. After cryogenic separation, LNG products are obtained, and the by-product cryogenic tail gas is reheated and enters the downstream production device.

[0030] Compared with the existing mature coke oven gas to liquefied natural gas technology with a circulation loop, the present invention eliminates the methanation circulating gas compressor and adds a mature conversion process before the methanation process. In the conversion process, CO with a large unit heat release in the methanation reaction is converted into CO2, that is, ~20% of the methanation reaction heat is transferred to the conversion unit, and the temperature of the conversion outlet is increased to reach the required temperature at the inlet of the methanation reactor, eliminating the preheater at the methanation inlet in the conventional process; at the same time, in order to ensure that the CO2 content at the methanation outlet meets the index requirements of deep cold separation, one or more methanation reactors are added to convert as much CO2 in the coke oven gas as possible into methane.

[0031] Compared with the prior art, the present invention has the following positive effects:

[0032] (I) In this process, compared with the coke oven gas to liquefied natural gas technology with a circulation loop, the methanogenic circulating gas compression step is omitted, and a conversion process is added. The converted coke oven gas is directly passed through a multi-stage methanogenic reactor to obtain a high-methane-content methane-rich gas, saving 100KW to 160KW / (10000Nm 3 coke oven gas);

[0033] (II) In this process, due to the reduction of circulating gas, the gas volume entering the tower for the methanation reaction is reduced by 30-40%, thereby reducing the consumption of methanation catalyst by 0.5-0.8 cubic meters / (year·10000Nm 3 coke oven gas);

[0034] (III) In this process, the circulating gas compressor and related heat exchanger system are omitted, and the methanation reactor also reduces the solvent due to the reduction of gas inlet, thereby reducing the equipment investment by 2.5 million to 3.5 million / (10000Nm 3 coke oven gas);

[0035] (IV) Compared with the methanation process with circulation, the methanation reactor of the same volume can process about 60% more raw gas. For large-scale projects, the production capacity of a single production line is increased by 60%. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the process of producing liquefied natural gas from coke oven gas with a shift-type non-methanation circulation loop Figure 1 ;

[0037] Figure 2 Schematic diagram of the process of producing liquefied natural gas from coke oven gas with a shift-type non-methanation circulation loop Figure 2 ;

[0038] Figure 3 Detailed process flow diagram of hydrodesulfurization in step 2 of Example 1 and Example 2. DETAILED DESCRIPTION

[0039] A process for producing liquefied natural gas from coke oven gas with a shift-free methanation circulation loop comprises the following steps:

[0040] 1) Purification: pre-treating the coke oven gas to obtain preliminarily purified coke oven gas;

[0041] 2) Hydrodesulfurization: The coke oven gas that has been initially purified is subjected to hydrodesulfurization treatment to remove sulfides in the coke oven gas;

[0042] 3) Conversion: Set up conversion and waste heat recovery units to adjust the ratio of H2, CO, and CO2 in the coke oven gas to obtain conversion gas;

[0043] 4) Methanation: multiple adiabatic methanation reactors are set up to convert all CO, CO2 and high-carbon hydrocarbons in the conversion gas into methane to obtain methane-rich gas;

[0044] 5) Cryogenic separation: Use mixed refrigerant to perform refrigeration separation process on methane-rich gas to obtain LNG product.

[0045] Preferably, the purification step described in step 1) is: the coke oven gas from coking is preliminarily removed of large molecular impurities in the coke oven gas by gas-liquid separation or adsorption, and then enters the gas cabinet for buffering and storage, and then enters the compressor to compress the coke oven gas from normal pressure to 1.0-4.5MPaG, and then sends it to the purification process unit; the purification process unit mainly includes washing, gas-liquid separation and adsorption steps to remove impurities such as tar, naphthalene, ammonia, hydrogen cyanide, etc. in the coke oven gas to the process requirements.

[0046] Preferably, the specific steps of hydrodesulfurization in step 2) are: after the purified coke oven gas is preheated, it enters the pre-hydrogenation reactor and the primary hydrogenation reactor in sequence to remove oxygen in the coke oven gas and convert most of the organic sulfur into inorganic sulfur, and then enters the primary medium-temperature zinc oxide tank to remove hydrogen sulfide in the coke oven gas; the coke oven gas from the primary medium-temperature zinc oxide tank then enters the secondary hydrogenation reactor to further convert the organic sulfur into inorganic sulfur, and then passes through the secondary medium-temperature zinc oxide tank to remove sulfur from the coke oven gas.

[0047] Preferably, the total sulfur in the coke oven gas after desulfurization in step 2) is reduced to ≤0.1 ppmv.

[0048] Preferably, the specific steps of the conversion in step 3) are: the desulfurized gas is recovered through waste heat, and after adding appropriate water vapor, it enters the conversion reactor, and the conversion gas is directly sent to the methanation unit.

[0049] Preferably, the transformation in step 3) is a sulfur-free adiabatic wide temperature transformation, with a transformation inlet temperature of 190-240°C and a transformation outlet temperature of 270-330°C.

[0050] Preferably, the dry basis index of carbon monoxide in the conversion gas obtained in step 3) is 0.2V% to 1.5V%.

[0051] Preferably, the specific steps of methanation in step 4) are: the conversion gas passes through 1 to 3 adiabatic methanation reactors (high temperature section methanation reaction) at one time, a steam generator is arranged at the outlet of each methanation reactor to recover heat and produce by-product steam, after the last methanation reactor, the methanated gas is cooled and condensed to separate water, and then enters 1 to 2 adiabatic methanation reactors (low temperature section methanation reaction), the residual CO and CO2 are subjected to methanation reaction, and the heat is recovered, cooled and the water is separated to obtain methane-rich gas, the main components of which are hydrogen, methane and nitrogen, wherein 10V% to 30V% of hydrogen, 60V% to 85V% of methane, and 3V% to 8V% of nitrogen.

[0052] Preferably, the process steam required for the shift conversion and methanation in steps 3 and 4) is mainly added at the inlet of the shift reactor.

[0053] Preferably, the methanation in step 4) is a sulfur-free adiabatic methanation reactor, wherein the methanation inlet temperature is 250-330°C, the high temperature section methanation outlet temperature is 500-650°C, and the low temperature section methanation reaction outlet temperature is 270-450°C.

[0054] Preferably, the methanation in step 4) is a high-temperature methanation reaction, which is then cooled to room temperature after heat recovery and then enters a low-temperature methanation reaction.

[0055] Preferably, the specific steps of cryogenic separation in step 5) are: the methane-rich gas is cryogenically pretreated to remove moisture, dust and other trace harmful impurities before entering a cold box; after cryogenic separation, an LNG product is obtained.

[0056] In order to better explain the content of the present invention, the present invention is further described below through specific embodiments, but it should not be understood that the protection scope of the present invention is limited thereto. All features disclosed in the content of the present invention, or all steps in the disclosed methods or processes, except for mutually exclusive features and / or steps, can be combined in any way. Any feature disclosed in the present invention, unless otherwise described, can be replaced by other alternative features that are equivalent or have similar purposes. That is, unless otherwise described, each feature is just an example of a series of equivalent or similar features.

[0057] The % involved in this application, unless otherwise specified, represents V%.

[0058] Embodiment 1:

[0059] A process for producing liquefied natural gas from coke oven gas with a conversion non-methanization circulation loop, the process flow diagram of which is shown in Figure 1 :

[0060] Coke oven gas in the inlet area is 40℃, pressure 6kPaG, gas volume 30000Nm 3 / h (dry basis), dry basis composition (V%): hydrogen 56.93%, carbon monoxide 10.38%, carbon dioxide 3.21%, methane 20.68%, oxygen 0.77%, CnHm2.45%, nitrogen 5.58%, impurity composition (mg / Nm 3 ): Tar 50, naphthalene 200, ammonia 50, hydrogen sulfide 50, organic sulfur 250, hydrogen cyanide 80, C6 and above hydrocarbons 3000.

[0061] 1) Compression and purification

[0062] The coke oven gas from coking is pre-treated to remove tar from the coke oven gas to 10mg / Nm 3 Below, naphthalene is removed to 150mg / Nm 3 After entering the gas cabinet for buffering and storage, the pressure is about 3-4 kPaG, and then it enters multiple parallel screw compressors, initially pressurized to 0.6 MPaG. The compressed coke oven gas passes through the rough purification unit to further remove tar, naphthalene, ammonia, hydrocyanic acid, H2S and other impurities in the coke oven gas, and then further pressurized to 2.5 MPaG by multiple parallel reciprocating compressors. The rough purification unit can remove tar from the coke oven gas to 1 mg / Nm 3 Below, naphthalene is removed to 5mg / Nm 3Below, ammonia removal to 10mg / Nm 3 Below, H2S removal to 5mg / Nm 3 the following.

[0063] 2) Hydrodesulfurization (see Figure 3 )

[0064] The coke oven gas from the reciprocating compressor has a temperature of 110°C. It is preheated to about 240°C and enters the pre-hydrogenation reactor and the first-stage hydrogenation reactor in turn to remove oxygen and unsaturated hydrocarbons in the coke oven gas, and at the same time convert 90% of the organic sulfur into inorganic sulfur. It then enters the first-stage medium-temperature zinc oxide tank to remove hydrogen sulfide in the coke oven gas. The coke oven gas from the first-stage medium-temperature zinc oxide tank then enters the second-stage hydrogenation reactor to further convert organic sulfur into inorganic sulfur, and then passes through the second-stage medium-temperature zinc oxide tank to remove the total sulfur content in the coke oven gas to less than 0.1ppm.

[0065] 3) Transformation

[0066] After the desulfurized gas is recovered from waste heat and appropriate water vapor is added, the temperature drops to 210°C before entering the wide temperature shift reactor. The temperature of the shifted gas is about 290°C. At this time, the main gas components of the shifted gas are 53.234% hydrogen, 1.11% carbon monoxide, 10.254% carbon dioxide, and 17.299% methane.

[0067] 4) Methanation

[0068] The converted gas directly enters the methanation unit. It first passes through the first-stage methanation reactor, and the reactor outlet temperature is 620-630°C. After by-product steam and waste heat recovery, it enters the second-stage methanation reactor, and the outlet temperature of the second-stage methanation reactor is 490-520°C. After the by-product steam and waste heat recovery of the second-stage outlet gas, it is cooled to room temperature by a water cooler for water separation. The second-stage gas after water separation is preheated and then enters the third-stage methanation reactor. The outlet temperature of the third-stage methanation reactor is 410-450°C. After the heat exchange temperature is reduced to ~270°C, it enters the fourth-stage methanation reactor. The outlet temperature of the fourth-stage methanation reactor is 280-330°C, and the outlet CO+CO2 is ≤50ppm. After waste heat recovery, it is cooled to 40°C with circulating water, and then cooled to ~15°C by low-temperature water washing to obtain methane-rich gas, the main components of which are 12.47% hydrogen and 76.56% methane. The volume of methane-rich gas is about 15865Nm 3 / h.

[0069] 5) Cryogenic separation

[0070] The methane-rich gas enters the drying tower from the bottom, and the moisture in the dry gas coming out from the top is removed to below 1ppm for cryogenic separation. The regeneration gas of the drying tower uses the tail gas of cryogenic separation. Then the mixed refrigerant refrigeration separation process is used to obtain LNG products ~8.79t / h. The by-product cryogenic tail gas is divided into two streams. One hydrogen-rich gas is used as dry regeneration gas and can be sent to PSA for separation to obtain high-purity hydrogen. The other nitrogen-rich gas is returned to the coke oven as fuel.

[0071] Example 2

[0072] A process for producing liquefied natural gas from coke oven gas with a conversion non-methanization circulation loop, the process flow diagram of which is shown in Figure 2 :

[0073] The coke oven gas in the inlet area is 40℃, the pressure is 6kPaG, and the gas volume is 30000Nm 3 / h (dry basis), dry basis composition (V%): hydrogen 56.93%, carbon monoxide 10.38%, carbon dioxide 3.21%, methane 20.68%, oxygen 0.77%, CnHm2.45%, nitrogen 5.58%, impurity composition (mg / Nm 3 ): Tar 50, naphthalene 200, ammonia 50, hydrogen sulfide 50, organic sulfur 250, hydrogen cyanide 80, C6 and above hydrocarbons 3000.

[0074] 1) Compression purification (same as Example 1)

[0075] The coke oven gas from coking is pre-treated to remove tar from the coke oven gas to 10mg / Nm 3 Below, naphthalene is removed to 150mg / Nm 3 After entering the gas cabinet for buffering and storage, the pressure is about 3-4 kPaG, and then it enters multiple parallel screw compressors, initially pressurized to 0.6 MPaG. The compressed coke oven gas passes through the rough purification unit to further remove tar, naphthalene, ammonia, hydrocyanic acid, H2S and other impurities in the coke oven gas, and then further pressurized to 2.5 MPaG by multiple parallel reciprocating compressors. The rough purification unit can remove tar from the coke oven gas to 1 mg / Nm 3 Below, naphthalene is removed to 5mg / Nm 3 Below, ammonia removal to 10mg / Nm 3 Below, H2S removal to 5mg / Nm 3 the following.

[0076] 2) Hydrodesulfurization (same as Example 1)

[0077] The coke oven gas from the reciprocating compressor has a temperature of 110°C. It is preheated to about 240°C and enters the pre-hydrogenation reactor and the first-stage hydrogenation reactor in turn to remove oxygen and unsaturated hydrocarbons in the coke oven gas, and at the same time convert 90% of the organic sulfur into inorganic sulfur. It then enters the first-stage medium-temperature zinc oxide tank to remove hydrogen sulfide in the coke oven gas. The coke oven gas from the first-stage medium-temperature zinc oxide tank then enters the second-stage hydrogenation reactor to further convert organic sulfur into inorganic sulfur, and then passes through the second-stage medium-temperature zinc oxide tank to remove the total sulfur content in the coke oven gas to less than 0.1ppm.

[0078] 3) Conversion (same as Example 1)

[0079] After the desulfurized gas is recovered from waste heat and appropriate water vapor is added, the temperature drops to 210°C before entering the wide temperature shift reactor. The temperature of the shifted gas is about 290°C. At this time, the main gas components of the shifted gas are 53.234% hydrogen, 1.11% carbon monoxide, 10.254% carbon dioxide, and 17.299% methane.

[0080] 4) Methanation

[0081] The converted gas directly enters the methanation unit. It first passes through the first-stage methanation reactor, and the reactor outlet is 620-630°C. After by-product steam and waste heat recovery, it enters the second-stage methanation reactor, and the outlet temperature of the second-stage methanation reactor is 490-520°C. The second-stage outlet gas enters the third-stage methanation reactor after by-product steam and waste heat recovery, and the outlet temperature of the third-stage methanation reactor is 350-390°C. The third-stage outlet gas produces by-product steam and waste heat recovery, and then is cooled to room temperature by a water cooler for water separation. After water separation, the third-stage gas is preheated and then enters the fourth-stage methanation reactor. The outlet temperature of the fourth-stage methanation reactor is 300-330°C, and the outlet CO+CO2 is ≤30ppm. After waste heat recovery, it is cooled to 40°C with circulating water, and then cooled to ~15°C by low-temperature water washing to obtain methane-rich gas, the main components of which are 12.51% hydrogen and 76.89% methane. The volume of methane-rich gas is about 15796Nm 3 / h.

[0082] 5) Cryogenic separation (same as Example 1)

[0083] The methane-rich gas enters the drying tower from the bottom, and the moisture in the dry gas coming out from the top is removed to below 1ppm for cryogenic separation. The regeneration gas of the drying tower uses the tail gas of cryogenic separation. Then the mixed refrigerant refrigeration separation process is used to obtain LNG products ~8.79t / h. The by-product cryogenic tail gas is divided into two streams. One hydrogen-rich gas is used as dry regeneration gas and can be sent to PSA for separation to obtain high-purity hydrogen. The other nitrogen-rich gas is returned to the coke oven as fuel.

[0084] The above-mentioned embodiments only express the specific implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the protection scope of the present application. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the technical solution concept of the present application, and these all belong to the protection scope of the present application.

[0085] This background section is provided to generally present the context of the invention, and the work of the presently named inventors, the work to the extent described in this background section, and aspects of this section that did not constitute prior art at the time of application are neither explicitly nor implicitly admitted to be prior art to the present invention.

Claims

1. A process for producing liquefied natural gas from coke oven gas with a conversion non-methanation circulation loop, characterized in that The following steps are involved: 1) Purification: pre-treating the coke oven gas to obtain preliminarily purified coke oven gas; 2) Hydrodesulfurization: The coke oven gas that has been initially purified is subjected to hydrodesulfurization treatment to remove sulfides in the coke oven gas; 3) Conversion: Set up conversion and waste heat recovery units to adjust the ratio of H2, CO, and CO2 in the coke oven gas to obtain conversion gas; 4) Methanation: multiple adiabatic methanation reactors are set up to convert all CO, CO2 and high-carbon hydrocarbons in the conversion gas into methane to obtain methane-rich gas; 5) Cryogenic separation: Use mixed refrigerant to perform refrigeration separation process on methane-rich gas to obtain LNG product.

2. A process for producing liquefied natural gas from coke oven gas with a conversion non-methanation circulation loop according to claim 1, characterized in that The purification step described in step 1) is specifically as follows: the coke oven gas from the coking is preliminarily removed of macromolecular impurities in the coke oven gas by gas-liquid separation or adsorption, and then enters the gas cabinet for buffering and storage, and then enters the compressor to compress the coke oven gas from normal pressure to 1.0-4.5MPaG, and then sends it to the purification process unit; the purification process unit mainly includes washing, gas-liquid separation and adsorption steps to remove tar, naphthalene, ammonia and hydrogen cyanide impurities in the coke oven gas to the process requirements.

3. A process for producing liquefied natural gas from coke oven gas with a conversion non-methanation circulation loop according to claim 1, characterized in that The specific steps of the hydrodesulfurization in step 2) are as follows: the purified coke oven gas is preheated and then enters a pre-hydrogenation reactor and a primary hydrogenation reactor in sequence to remove oxygen from the coke oven gas and convert most of the organic sulfur into inorganic sulfur, and then enters a primary medium-temperature zinc oxide tank to remove hydrogen sulfide from the coke oven gas; the coke oven gas from the primary medium-temperature zinc oxide tank then enters a secondary hydrogenation reactor to further convert the organic sulfur into inorganic sulfur, and then passes through a secondary medium-temperature zinc oxide tank to remove sulfur from the coke oven gas.

4. A process for producing liquefied natural gas from coke oven gas with a conversion non-methanation circulation loop according to claim 1 or 3, characterized in that: After desulfurization in step 2), the total sulfur in the coke oven gas is reduced to ≤0.1 ppmv.

5. A process for producing liquefied natural gas from coke oven gas with a conversion non-methanization circulation loop according to claim 4, characterized in that The specific steps of the conversion described in step 3) are: the desulfurized gas is recovered through waste heat, and after adding appropriate water vapor, it enters the conversion reactor, and the conversion gas is directly sent to the methanation unit; the conversion is a sulfur-free adiabatic wide temperature conversion, the conversion inlet temperature is 190-240°C, and the conversion outlet temperature is 270-330°C; in the obtained conversion gas, the dry basis index of carbon monoxide is 0.2V%~1.5V%.

6. A process for producing liquefied natural gas from coke oven gas with a shift-type non-methanation circulation loop according to claim 1 or 5, characterized in that: The specific steps of methanation in step 4) are as follows: the conversion gas passes through 1 to 3 adiabatic methanation reactors at one time for a high-temperature methanation reaction, a steam generator is arranged at the outlet of each methanation reactor to recover heat and produce by-product steam, after the last methanation reactor, the methanation-rich gas is cooled, condensed and separated from water, and then enters 1 to 2 adiabatic methanation reactors for a low-temperature methanation reaction, the residual CO and CO2 are subjected to a methanation reaction, and after heat recovery, cooling and separation of water, a methane-rich gas is obtained, the main components of which are hydrogen, methane and nitrogen, wherein 10V% to 30V% of hydrogen, 60V% to 85V% of methane and 3V% to 8V% of nitrogen.

7. A process for producing liquefied natural gas from coke oven gas with a shift-type non-methanation circulation loop according to claim 6, characterized in that Water steam is mainly added at the inlet of the shift reactor.

8. A process for producing liquefied natural gas from coke oven gas with a shift-type non-methanation circulation loop according to claim 1 or 7, characterized in that: The methanation described in step 4) is a sulfur-free adiabatic methanation reaction, wherein the methanation inlet temperature is 250-330°C, the high temperature section methanation outlet temperature is 500-650°C, and the low temperature section methanation reaction outlet temperature is 270-450°C.

9. A process for producing liquefied natural gas from coke oven gas with a shift-type non-methanation circulation loop according to claim 8, characterized in that: The methanation in step 4) is a high-temperature methanation reaction gas, which is heat recovered, cooled to room temperature and separated into water before entering the low-temperature methanation reaction.

10. A process for producing liquefied natural gas from coke oven gas with a shift-type non-methanation circulation loop according to claim 1 or 9, characterized in that The specific steps of cryogenic separation in step 6) are as follows: the methane-rich gas is cryogenically pretreated to remove moisture, dust and other trace harmful impurities before entering a cold box; after cryogenic separation, an LNG product is obtained.

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