CN101538483B - Poly-generation technique for using coal gas and coke oven gas as raw materials - Google Patents

Abstract

A polygeneration process using coal-to-gas and coke oven gas as raw materials is to mix the purified water gas with coke oven gas through pressure swing adsorption _and the tail gas of Fischer-Tropsch synthesis for Fischer-Tropsch synthesis. Synthesis to obtain hydrocarbon mixture and tail gas. Tail gas is separated from _CO by the first pressure swing adsorption to synthesize urea unit for reaction; the remaining tail gas is separated by the second and third pressure swing adsorption to obtain CO and hydrogen respectively and recycled back to the Fischer-Tropsch synthesis unit for reaction; the residual tail gas can be used for power generation or through Secondary condensation yields SNG. After the coke oven gas is purified and desulfurized, it enters the pressure swing adsorption to separate H ₂ , a part of the H ₂ is supplemented as Fischer-Tropsch synthesis H ₂ , and the other part of the H ₂ is mixed with N ₂ to synthesize ammonia to obtain synthetic ammonia, and the synthetic ammonia is combined with the CO obtained from the first condensation. ₂ and CO ₂ separated in Fischer-Tropsch synthesis are mixed for urea synthesis to obtain urea. Coke oven gas pressure swing adsorption and desorption gas is condensed for the first time to separate CO ₂ to urea synthesis, and the remaining gas is condensed for the second time to obtain the product SNG and the mixed gas of CO and N ₂ . The invention has no emission of greenhouse gases, utilizes the carbon-rich hydrogen-deficient of coal gas and the hydrogen-rich and carbon-deficient coke oven gas to complement each other, realizes the structural adjustment of the Fischer-Tropsch synthesis product, and improves the economy of the Fischer-Tropsch synthesis process.

Description

A polygeneration process using coal gas and coke oven gas as raw materials

technical field

The invention belongs to a technology for cogeneration by using coke oven gas and coal gas as raw materials.

Background technique

As a fossil energy with high carbon emissions, coal's traditional direct combustion utilization and conversion technology can no longer meet the increasingly high economic and environmental requirements. Obtaining coal-based liquid fuels and high value-added chemicals through Fischer-Tropsch synthesis is a new industrial frontier in the field of coal chemical industry, with broad application prospects and economic benefits. Urea is currently the most used nitrogen fertilizer, and synthetic natural gas (SNG) is a relatively scarce clean fuel in my country (at present, domestic demand is strong and there is a large gap). This requires that economic benefits, environmental benefits and social benefits can be well coordinated in industrial planning and technology research and development, and product structure and corresponding technical routes can be optimized to achieve the healthy development of the modern coal chemical industry.

Coke oven gas is a by-product of coal dry distillation into coke, the main components are: H ₂ 58-66%; CH ₄ 21-25%; CO 5-8%; C _m H _n 1.6-2.0%; CO ₂ 1.9% -2.3%; _N2 2-6%. Using coke oven gas alone as a raw material, about 20% of the methane needs to be steam reformed _or partially oxidized to generate reformed gas. The H ₂ /CO molar ratio of the reformed gas is as high as 4, which is 2 times, which is manifested as hydrogen-rich and carbon-deficient, so it is used for Fischer-Tropsch synthesis reaction, and nearly half of the hydrogen cannot be effectively utilized due to lack of CO matching. If it is used to produce synthetic ammonia, it needs to be converted and transformed at the same time, the process is complicated and the investment is high.

The typical composition of water gas produced by coal gasification is: CO 47.14%; H ₂ 34.35%; CO ₂ 17.6%; CH ₄ 0.117%; others 0.793%. The molar ratio of H ₂ /CO in water gas is only 0.73, which is far lower than the requirement of Fischer-Tropsch synthesis gas for the molar ratio of H ₂ /CO, which is manifested as carbon-rich and hydrogen-deficient. This atmosphere composition cannot be satisfied in the Fischer-Tropsch synthesis process. For this reason, the water-gas shift process must be adopted to reduce the total amount of water-gas to nearly 50%. Further hydrogen production is carried out by transformation according to the following inversion: CO+H ₂ O=CO ₂ +H ₂ , the gas composition after partial transformation is: CO 21.24%; H ₂ 46.02%; CO 31.99%; CH ₄ 0.093%; others 0.657%. As a result, a large amount of carbon does not participate in the Fischer-Tropsch synthesis reaction, but is lost in the form of greenhouse gas CO ₂ emissions, resulting in a huge waste of coal resources.

Contents of the invention

The purpose of the present invention is to use the carbon-rich hydrogen deficiency of coal-based gas and the hydrogen-rich carbon deficiency of coke oven gas to complement each other to generate coal-based fuels and chemicals, and to produce urea and gas-fired power generation at the same time, so as to realize the process of polygeneration and carbon " zero emission".

Preparation method of the present invention comprises the steps:

(1) Raw coal, water vapor and oxygen are gasified to generate water gas, and the water gas is initially purified to obtain primary purified water gas;

(2) The water gas after primary purification enters deep purification to obtain products S, CO and H ₂ , and the purified CO and H ₂ are mixed with H ₂ from pressure swing adsorption and Fischer-Tropsch synthesis cycle tail gas (CO+H ₂ ) Become the raw material gas for Fischer-Tropsch synthesis. The raw material gas for Fischer-Tropsch synthesis undergoes Fischer-Tropsch synthesis reaction under the action of Fischer-Tropsch synthesis catalyst to obtain hydrocarbon mixture and tail gas. The hydrocarbon mixture can be separated by existing technology to obtain paraffin, gasoline, diesel oil, and solvent oil. And various products such as naphtha;

(3) The tail gas after the Fischer-Tropsch synthesis is separated by the first pressure swing adsorption _CO2 to synthesize the urea unit; the remaining tail gas is recycled to the Fischer-Tropsch synthesis by the CO and _H obtained by the second and third adsorption separation respectively; the residual tail gas The product SNG is obtained after secondary condensation, and can also be mixed with air to generate electricity through a gas turbine;

(4) The coke oven gas is purified and desulfurized after being compressed. The gas after purification and desulfurization is subjected to pressure swing adsorption to obtain _H2 and desorption mixed gas. The first condensation separates CO ₂ to urea synthesis, and the remaining gas after the separation of CO ₂ is condensed for the second time to obtain the residual mixed gas of synthetic natural gas (SNG) products, CO and N 2 ;

(5) A part of hydrogen separated by pressure swing adsorption and _N Carry out ammonia synthesis under the action of a synthetic ammonia catalyst to obtain synthetic ammonia;

(6) Synthetic ammonia is mixed with CO ₂ separated from the first condensation, CO ₂ separated from gasified water gas, and CO ₂ separated after Fischer-Tropsch synthesis, and then synthesized urea to obtain synthetic urea.

The coal gasification mentioned above is based on the American Texaco entrained flow coal water slurry gasification technology, the Holland Shell Shell pulverized coal pressurized gasification technology, and the ash fusion fluidized bed pulverized coal of the Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences. Pressurized gasification technology, etc.

The preliminary purification of the water gas as mentioned above is because the water gas contains a small amount of dust and impurities, which can be washed and dedusted by Venturi scrubbers and carbon scrubbers. When the pressure of raw coal, water vapor and oxygen to generate water gas through coal gasification is lower than the pressure required by Fischer-Tropsch synthesis, the initial purification of water gas requires preliminary desulfurization before gas compression. Improve the ADA method or complex iron method and other processes.

The processes adopted for the above-mentioned deep purification include: low-temperature methanol washing (Rectisol) process technology, polyethylene glycol dimethyl ether (NHD) method. The content of H ₂ S in the purified methanol synthesis gas is not higher than 0.1ppm.

The above-mentioned Fischer-Tropsch synthesis is at the molar ratio of hydrogen to carbon: (H ₂ -CO ₂ )/(CO+CO ₂ )=1.5-2.2, reaction pressure 1.5-5.0Mpa, reaction temperature 140-300°C, space velocity 300 The Fischer-Tropsch synthesis reaction was carried out under the condition of -5000h ^-1 . Arge process, SAS process, SSPD process of South African Sasol company, SMDS process of Shell company, MFT process and SMFT process of Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences can be used.

The above-mentioned Fischer-Tropsch synthesis catalyst includes the following catalysts: Patent No. 02140487.9 (catalyst composition: cobalt content 10-80%, zirconia 15-85%, metal oxide 0-5%), patent No. 00109594.3 (catalyst composition: cobalt content 10-35%, sodium-free silicon oxide 65-90%), patent number 01134919.0 (catalyst composition: first active component (Fe) content 4-40%, second active component (Group VIII metal element) content 0.01-10%, additive element (Group IB, IIIB, IA metal elements) content 0.01-20%, carrier is apricot kernel activated carbon or coconut shell activated carbon), patent No. 200610007543.1 (catalyst composition: cobalt content 5-35%, The content of zirconium element is 0.01-5%, and the rest is amorphous _SiO2 carrier), U.S. Patent US4585798 (catalyst composition: cobalt content 5-30%, ruthenium content is 1/200-1/3400 of cobalt content, and the rest is alumina carrier ), U.S. Patent US4719240 (catalyst metal atomic ratio: Fe is 0.8-1.2, Zn is 0.05-0.08, Ti/Mn is 0.25-0.35, Ce is 0.01-0.15, K is 0.01-0.15), patent No. 93106465.1 (catalyst composition : cobalt content 5-60%, the second metal (platinum, iridium, rhodium) content is 0.1-50% of cobalt content, all the other are alumina carrier), publication number CN101224425A (cobalt content 5-35%, others are inert carrier , including inert oxides, molecular sieves and carbon materials, etc.), etc.

As in the above step (3), the conditions for the first pressure swing adsorption separation of the Fischer-Tropsch synthesis tail gas are 0.5-3.0 MPa, and the temperature is less than 40°C.

As in the above step (3), the condition for the second pressure swing adsorption separation of the Fischer-Tropsch synthesis tail gas is 0.5-3.0 MPa, and the temperature is less than 40°C.

As in the above step (3), the condition for the third pressure swing adsorption separation of the Fischer-Tropsch synthesis tail gas is 0.5-3.0 MPa, and the temperature is less than 40°C.

The pressure of the above-mentioned coke oven gas compressed by the compressor is 1.5-5.0 MPa.

The purification and desulfurization process described in step (4) above includes: improved ADA method, rubber copying method, Fermax-Rodacus-Kumpakus method, etc.

The conditions for the pressure swing adsorption as described in the above step (4) are pressure 1.5-4.5 MPa and temperature less than 40°C.

The above-mentioned ammonia synthesis process conditions are that the ammonia synthesis reaction is carried out under the conditions of a hydrogen-to-nitrogen molar ratio of 2.9-3.2, a pressure of 10-35Mpa, a temperature of 400-500°C, and a space velocity of ^{10000-30000-1} ; the ammonia synthesis process includes : Kellogg process, Brown cryogenic purification process, ICI AM-V process, LCA process and KPK process.

The ammonia synthesis catalyst mentioned above is the A102 type, A106 type, A109 type iron catalyst of Nanjing Chemical Industry Company; the A110-2, A301 type ammonia synthesis catalyst of Zhejiang University of Technology; the IC174-1 of the iron-cobalt system developed by the British ICI company , ICI35-4, ICI73-1 ammonia synthesis catalysts; A201 catalysts from Fuzhou University; KMI, KMII, KMIII catalysts from Denmark; C73-1, C73-2 C73-3 catalysts from the United States, etc.

The above-mentioned urea synthesis is carried out under the production process conditions of temperature 160-210°C, pressure 13-24MPa, ammonia-carbon molar ratio 2.8-4.5, water-carbon molar ratio 0.4-0.8, and the synthesis process can be an aqueous solution Full circulation method, air stripping method, combined urine method, SRR method, UTI company HR method, etc.

The first condensation temperature as mentioned above is: -70～-85°C, the pressure is: 1.5-4.5MPa; the second condensation temperature is: -160～-175°C, the pressure is: 1.5-4.5MPa.

The above-mentioned power generation adopts a gas turbine, preheats the exhaust gas to 100-500°C, and the volume ratio of air and air is 1:2-4, the total pressure is 0.5MPa-2.0MPa, and the mixture is fed into the gas turbine for combustion at 800-1600°C generate electricity.

Advantages of the present invention:

1) This patent organically combines "carbon-rich and hydrogen-deficient" coal-based gas with "hydrogen-rich and carbon-deficient" coke oven gas, optimizes Fischer-Tropsch synthesis and urea synthesis gas by means of pressure swing adsorption, and prepares SNG by means of cryogenic cooling.

2) This patented process realizes coke oven gas non-conversion and coal-to-gas non-conversion operation, greatly simplifying the process flow.

3) The invention has the advantages of no greenhouse gas emission, energy saving, water saving, investment saving, simple technological process, and the coordinated development of economy, environment and energy. At the same time, it can realize the structural adjustment of Fischer-Tropsch synthesis products in combination with market needs, improve the economics of the Fischer-Tropsch synthesis process, and realize the maximization of the total process economy.

Description of drawings

Fig. 1 is a process flow diagram of the present invention

Detailed ways

Example 1:

In the coal gasification process, the coal is pre-treated and sprayed into the ash fusion gasification furnace to chemically react with water vapor and pure oxygen from air separation at a temperature of 1000 ° C and a pressure of 1.0 MPa to generate CO and H ₂ , CO ₂ , H ₂ O and a small amount of CH ₄ , H ₂ S, COS and other components of water gas. The water gas containing a small amount of dust and impurities is initially purified. Due to the dusty water gas from gasification, it still contains acid gas after being washed, dedusted and cooled by Venturi scrubber and carbon scrubber. In order to protect the compressor, the desulfurization method is also used. Make the H ₂ S content less than 30mg/Nm ³ , compress the water gas after preliminary purification to a pressure of 2.5MPa, and then carry out deep purification. Deep purification adopts polyethylene glycol dimethyl ether (NHD) method for desulfurization and decarburization. The removed H ₂ S gas is desulfurized by the recovery unit to recover sulfur; the removed CO ₂ is used for urea synthesis. Deeply purified water gas, coke oven gas pressure swing adsorption hydrogen compressed to 2.5MPa and tail gas recycled after Fischer-Tropsch synthesis are mixed to form fresh Fischer-Tropsch synthesis gas with H ₂ S content lower than 0.1 ppm, hydrogen-carbon molar ratio=(H ₂ -CO ₂ )/(CO+CO ₂ )=2.0. Qualified fresh synthesis gas enters the Fischer-Tropsch synthesis reactor, which is a fixed-bed reactor, with a reaction pressure of 2.5MPa, a reaction temperature of 220°C, and a space velocity of 2000h ^-1 , using Sasol's Arge process and a catalyst prepared according to patent CN1084153 , the hydrocarbon mixture and tail gas obtained after Fischer-Tropsch synthesis. Products such as paraffin, diesel oil, gasoline, lubricating oil and naphtha can be obtained by mixing and processing hydrocarbons using the prior art. The tail gas is separated in the first adsorption separator under the operating conditions of 40°C and 2.5MPa to obtain _CO2 to synthesize urea unit; the remaining tail gas is separated in the second and third adsorption separators in turn, operating at 40°C and 2.5MPa Conditions, respectively to obtain CO and hydrogen cycle will be Fischer-Tropsch synthesis front-stage and deeply purified coal gas, hydrogen from pressure swing adsorption mixed into Fischer-Tropsch synthesis raw material gas. The residual tail gas can be used for power generation or SNG can be obtained in the second stage of cryogenic cooling. The coke oven gas from the outside is compressed to a pressure of 2.15MPa by a coke oven gas compressor, and the operating temperature is 35°C. It is desulfurized by the rubber-coating method, and the gas after purification and desulfurization enters pressure swing adsorption. _H2 and desorption mixed gas are obtained through pressure swing adsorption, part of the hydrogen obtained by pressure swing adsorption is removed for Fischer-Tropsch synthesis, and part of ammonia is removed for synthesis; the desorption mixed gas is condensed for the first time to separate CO ₂ to urea synthesis, and the remaining CO ₂ is separated The gas is cooled to -175°C by a second condensation to obtain a synthetic natural gas (SNG) product mixed with CO and _N2 , which can be used as fuel _. The _H2 from the pressure swing adsorption and the _N2 from the air separation unit enter the ammonia synthesis process according to the _H2 : _N2 molar ratio of 2.95:1, and are compressed at a pressure of 15MPa, a temperature of 400°C, and a space velocity of 10000h ^- At ¹ h, the ammonia synthesis reaction was carried out on the A109 iron-based catalyst. The ammonia synthesized enters the urea synthesis. The CO ₂ separated by the first condensation, the CO ₂ separated by deep purification, and the CO ₂ separated from the tail gas after Fischer-Tropsch synthesis are combined with liquid ammonia, and respectively pressurized into the urea synthesis tower. Under the production process conditions of 13-14MPa, temperature 180-185°C, ammonia-carbon molar ratio 2.8-2.9, water-carbon ratio 0.4, the urea synthesis reaction is carried out. Synthetic urea is evaporated to obtain 99.7% urea melt, which is sent to a prilling tower for granulation to obtain urea products.

Example 2:

In the coal gasification process, the coal is pre-treated to make 65% coal water slurry and sprayed into the Texaco gasifier at a temperature of 1300 ° C and a pressure of 7.0 MPa to obtain pure oxygen with gasified water vapor and air separation. Carry out chemical reaction to generate water gas containing CO, H ₂ , CO ₂ , H ₂ O and a small amount of CH ₄ , H ₂ S, COS and other components. The gasified dusty water gas, after being washed, dedusted and cooled by Venturi scrubber and carbon washing tower, enters deep purification, in which low-temperature methanol washing process is used for desulfurization and decarbonization. The removed H ₂ S gas is desulfurized by the recovery unit to recover sulfur, and the removed CO ₂ is used for urea synthesis. Deeply purified water gas, coke oven gas pressure swing adsorption hydrogen compressed to 2.0MPa and tail gas recycled after Fischer-Tropsch synthesis are mixed to form fresh Fischer-Tropsch synthesis gas with H ₂ S content lower than 0.1 ppm, hydrogen-carbon molar ratio: (H ₂ -CO ₂ )/(CO+CO ₂ )=2.1. Qualified fresh synthesis gas enters the Fischer-Tropsch synthesis reactor. At a reaction pressure of 2.0MPa, a reaction temperature of 240°C, and a space velocity of 3000h ^-1 , the Fischer-Tropsch synthesis reaction is carried out by using Shell's SMDS process and the catalyst described in patent CN1418933 to obtain hydrocarbons mixtures and exhaust gases. Products such as paraffin, diesel oil, gasoline, lubricating oil and naphtha can be obtained by mixing and processing hydrocarbons using the prior art. The tail gas is separated in the first adsorption separator under the operating conditions of 40°C and 2.5MPa to obtain _CO2 to synthesize urea unit; the remaining tail gas is separated in the second and third adsorption separators in turn, operating at 40°C and 2.5MPa Conditions, respectively to obtain CO and hydrogen cycle will be Fischer-Tropsch synthesis front-stage and deeply purified coal gas, hydrogen from pressure swing adsorption mixed into Fischer-Tropsch synthesis raw material gas. The residual tail gas can be used for power generation or SNG can be obtained in the second stage of cryogenic cooling. The coke oven gas from the outside is compressed by the coke oven gas compressor to 2.0MPa pressure and desulfurized by the improved ADA method to purify the desulfurized gas. At 2.0MPa pressure and temperature 38°C, _H2 and desorption mixed gas are obtained through pressure swing adsorption , part of the hydrogen obtained by pressure swing adsorption goes to Fischer-Tropsch synthesis, and part of it goes to ammonia synthesis; the desorbed mixed gas is condensed for the first time to separate CO ₂ to urea synthesis, and the remaining gas separated from CO ₂ is condensed for the second time and cooled to -168 °C, a mixture of synthetic natural gas (SNG) products and CO and _N2 is obtained, and the mixture of CO and _N2 can be used as fuel. The _H2 from the pressure swing adsorption and the _N2 from the air separation unit enter the ammonia synthesis process according to the _H2 molar ratio of 3:1. After compression, under the conditions of pressure 30MPa and temperature 450℃, the air velocity of the gas entering the tower is 20000h ^-1 , Ammonia synthesis reaction under the action of A201 iron-based catalyst of Fuzhou University. The ammonia synthesized enters the urea synthesis. The CO ₂ separated by the first condensation, the CO ₂ separated by deep purification, the CO ₂ separated from the Fischer-Tropsch synthesis tail gas and liquid ammonia are respectively pressurized into the urea synthesis tower, using the HR method of UTI Company, at a pressure of 20.6 MPa and a temperature of 193 ℃, ammonia-to-carbon ratio 4.2, water-to-carbon ratio 0.4 production process conditions, carry out urea synthesis reaction. Synthetic urea is evaporated to obtain 99.7% urea melt, which is sent to the prilling tower for granulation.

Example 3:

In the coal gasification process, the coal is pre-treated to make 65% coal-water slurry and sprayed into the Texaco gasifier at a temperature of 1450 ° C and a pressure of 6.0 MPa to form pure oxygen with gasified water vapor and air separation. Carry out chemical reaction to generate water gas containing CO, H ₂ , CO ₂ , H ₂ O and a small amount of CH ₄ , H ₂ S, COS and other components. The gasified dusty water gas, after being washed, dedusted and cooled by Venturi scrubber and carbon washing tower, enters deep purification, in which low-temperature methanol washing process is used for desulfurization and decarbonization. The removed H ₂ S gas is desulfurized by the recovery unit to recover sulfur, and the removed CO ₂ is used for urea synthesis. Water gas after deep purification, coke oven gas pressure swing adsorption hydrogen compressed to 5.0MPa pressure and tail gas recycled after Fischer-Tropsch synthesis are mixed to form fresh Fischer-Tropsch synthesis gas with H ₂ S content lower than 0.1 ppm, hydrogen-carbon molar ratio: (H ₂ -CO ₂ )/(CO+CO ₂ )=1.9. Qualified fresh synthesis gas enters the Fischer-Tropsch synthesis reactor. At a reaction pressure of 5.0MPa, a reaction temperature of 300°C, and a space velocity of 5000h ^-1 , the synthesis gas is processed using the SMFT process of the Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences and the catalyst described in patent CN200510026968.2. Tropsch synthesis reaction to obtain hydrocarbon mixture and tail gas. Products such as paraffin, diesel oil, gasoline, lubricating oil and naphtha can be obtained by mixing and processing hydrocarbons using the prior art. The tail gas is separated in the first adsorption separator under the operating conditions of 40°C and 2.5MPa to obtain _CO2 to synthesize urea unit; the remaining tail gas is separated in the second and third adsorption separators in turn, operating at 40°C and 2.5MPa Conditions, respectively to obtain CO and hydrogen cycle will be Fischer-Tropsch synthesis front-stage and deeply purified coal gas, hydrogen from pressure swing adsorption mixed into Fischer-Tropsch synthesis raw material gas. The residual tail gas can be used for power generation or SNG can be obtained in the second stage of cryogenic cooling. The coke oven gas from the outside is compressed to a pressure of 5.0MPa by a coke oven gas compressor, desulfurized by the Fermax-Rodacos-Kumpakus method, and the desulfurized gas is purified at a pressure of 4.97MPa and a temperature of 45°C , through pressure swing adsorption to obtain _H2 and desorption mixed gas, the hydrogen obtained by pressure swing adsorption is partly de-methanol-synthesized, partly de-ammonia-synthesized; the desorbed mixed gas is condensed for the first time to separate _CO2 to urea-synthesized, and the remaining _CO2 is separated The gas is condensed a second time and cooled to -160°C to obtain a synthetic natural gas (SNG) product mixed with CO and _N2 , which can be used as fuel _. The _H2 from the pressure swing adsorption and the _N2 from the air separation unit enter the ammonia synthesis process according to the molar ratio of _H2 : _N2 = 3.05:1, and are compressed under the conditions of pressure 30MPa and temperature 450°C. It is 30000h ^-1 , and the ammonia synthesis reaction is carried out in the C73-1 iron catalyst in the United States. The ammonia synthesized enters the urea synthesis. The CO ₂ separated by the first condensation and the CO ₂ separated by the deep purification are combined with liquid ammonia and respectively pressurized into the urea synthesis tower. The traditional aqueous solution full circulation method is adopted. At a pressure of 20-22 MPa and a temperature of 185-190 ° C, the ammonia The carbon ratio is 4.5, and the water-to-carbon ratio is 0.6-0.7 under the production process conditions, and the urea synthesis reaction is carried out. The urea melt obtained by evaporating synthetic urea is sent to the prilling tower for granulation.

Claims (16)

1. A kind of technique that utilizes coal gas and coke oven gas to be raw material polygeneration, is characterized in that comprising the steps: (1) Raw coal, water vapor and oxygen are gasified to generate water gas, and the water gas is initially purified to obtain primary purified water gas; (2) The water gas after initial purification enters deep purification to obtain products S, CO and H ₂ , and the purified CO and H ₂ are mixed with H ₂ from pressure swing adsorption and the tail gas of Fischer-Tropsch synthesis cycle to become raw materials for Fischer-Tropsch synthesis Gas, Fischer-Tropsch synthesis feed gas undergoes Fischer-Tropsch synthesis reaction under the action of Fischer-Tropsch synthesis catalyst to obtain hydrocarbon mixture and tail gas, and the hydrocarbon mixture is separated to obtain various products of paraffin, gasoline, diesel oil, solvent oil and naphtha; (3), the tail gas after the Fischer-Tropsch synthesis is separated by the first pressure swing adsorption _CO2 to synthesize the urea unit; the remaining tail gas is passed through the second and third adsorption separation respectively CO and _H2 are recycled to the Fischer-Tropsch synthesis; The tail gas is condensed twice to obtain the product SNG, and it can also be mixed with air to generate electricity through the gas turbine to obtain the product electricity; (4) The coke oven gas is purified and desulfurized after being compressed, and the gas after purification and desulfurization is subjected to pressure swing adsorption to obtain _H2 and desorption mixed gas. After the first condensation, _CO2 is separated to urea synthesis, and the remaining gas after _CO2 is separated is condensed for the second time to obtain the residual mixed gas of synthetic natural gas products, CO and _N2 ; (5), a part of hydrogen separated by pressure swing adsorption and _N Carry out ammonia synthesis under the action of synthetic ammonia catalyst to obtain synthetic ammonia; (6) Synthetic ammonia is mixed with CO ₂ separated from the first condensation, CO ₂ separated from gasified water gas, and CO ₂ separated after Fischer-Tropsch synthesis, and then synthesized urea to obtain synthetic urea; The Fischer-Tropsch synthesis is at a hydrogen-carbon molar ratio: (H ₂ -CO ₂ )/(CO+CO ₂ )=1.5-2.2, a reaction pressure of 1.5-5.0 Mpa, a reaction temperature of 140-300°C, and a space velocity of 300- The Fischer-Tropsch synthesis reaction is carried out under the condition of 5000h ^-1 , using the Arge process, SAS process, SSPD process of South African Sasol Company, SMDS process of Shell Company, MFT process or SMFT process of Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences. 2. A kind of technology that utilizes coal-based gas and coke oven gas as raw material polygeneration as claimed in claim 1, is characterized in that described coal gasification adopts American Texaco entrained flow bed coal-water slurry gasification technology , Holland Shell Shell pulverized coal pressurized gasification technology or ash fusion fluidized bed pulverized coal pressurized gasification technology of Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences. 3. A kind of technique that utilizes coal gas and coke oven gas as raw material polygeneration as claimed in claim 1, it is characterized in that described water gas preliminary purification is that water gas contains a small amount of dust, impurity through Venturi scrubber, Carbon washing tower for washing and dust removal; when the pressure of raw coal, water vapor and oxygen to generate water gas through coal gasification is lower than the pressure required for Fischer-Tropsch synthesis, the initial purification of water gas requires preliminary desulfurization before gas compression. Use the glue desulfurization method, the improved ADA method or the complex iron method. 4. A kind of technology that utilizes coal gas and coke oven gas as raw material polygeneration as claimed in claim 1, it is characterized in that described deep purification adopts low-temperature methanol washing technology, polyethylene glycol dimethyl ether method , the content of H ₂ S in the purified methanol synthesis gas is not higher than 0.1ppm. 5. A kind of technology that utilizes coal gas and coke oven gas as raw material polygeneration as claimed in claim 1, is characterized in that described Fischer-Tropsch synthesis catalyst comprises following catalyst: catalyst composition: cobalt content 10-35% , sodium-free silica 65-90% or catalyst composition: the first active component Fe content is 4-40%, the second active component is Group VIII metal element content 0.01-10%, and the auxiliary element is IB, IIIB , The content of group IA metal elements is 0.01-20%, the carrier is apricot core activated carbon or coconut shell activated carbon or catalyst composition: the cobalt content is 5-35%, the zirconium element content is 0.01-5%, and the rest is amorphous _SiO2 carrier or catalyst composition: The cobalt content is 5-30%, the ruthenium content is 1/200-1/3400 of the cobalt content, and the rest is alumina carrier or catalyst Metal atomic ratio: Fe is 0.8-1.2, Zn is 0.05-0.08, Ti/Mn is 0.25- 0.35, Ce 0.01-0.15, K 0.01-0.15 or catalyst composition: cobalt content 5-35%, others are inert carriers, including inert oxides, molecular sieves and carbon materials. 6. a kind of utilization coal gas and coke oven gas as claimed in claim 1 is the technique of raw material polygeneration, it is characterized in that described step (3) Fischer-Tropsch synthesis tail gas first pressure swing adsorption separation condition is 0.5 ~ 3.0MPa, the temperature is less than 40 ℃. 7. a kind of utilization coal gas and coke oven gas as claimed in claim 1 is the technique of raw material polygeneration, it is characterized in that the condition of described step (3) Fischer-Tropsch synthesis tail gas second pressure swing adsorption separation is 0.5 ~ 3.0MPa, the temperature is less than 40 ℃. 8. a kind of utilization coal gas and coke oven gas as claimed in claim 1 is the technique of polygeneration of raw material, it is characterized in that the condition of described step (3) Fischer-Tropsch synthesis tail gas the 3rd pressure swing adsorption separation is 0.5 ~ 3.0MPa, the temperature is less than 40 ℃. 9. A process of utilizing coal-based gas and coke oven gas as raw materials for polygeneration as claimed in claim 1, characterized in that the pressure of the coke oven gas after being compressed by the compressor is 1.5-5.0 MPa. 10. A kind of technology that utilizes coal gas and coke oven gas as raw material polygeneration as claimed in claim 1, it is characterized in that the purification and desulfurization adopting process described in the (4) step includes: improved ADA method, copy Glue method or Fermax-Lodakos-Kumpakus method. 11. A kind of technology that utilizes coal-based gas and coke oven gas as raw material polygeneration as claimed in claim 1, it is characterized in that the condition of pressure swing adsorption described in step (4) is pressure 1.5-4.5MPa, temperature less than 40°C. 12. A kind of technology that utilizes coal gas and coke oven gas as raw material polygeneration as claimed in claim 1, it is characterized in that described ammonia synthesis process condition is that the pressure is at the hydrogen-nitrogen molar ratio of 2.9-3.2, and the pressure is 10 -35Mpa, temperature 400-500℃, space velocity between 10000-30000h-1 for ammonia synthesis reaction; ammonia synthesis process includes: Kellogg process, Brown cryogenic purification process, ICI AM-V process, LCA process or KPK process. 13. A process for polygeneration using coal-based gas and coke oven gas as raw material as claimed in claim 12, characterized in that said ammonia synthesis catalyst is A102, A106 or A109 iron from Nanjing Chemical Industry Company Catalyst; A110-2 or A301 ammonia synthesis catalyst of Zhejiang University of Technology; IC174-1, ICI35-4 or ICI73-1 ammonia synthesis catalyst of iron-cobalt system developed by British ICI company; A201 catalyst of Fuzhou University; Denmark KMI, KMII or KMIII catalysts or American C73-1, C73-2 or C73-3 catalysts. 14. A polygeneration process using coal-based gas and coke oven gas as raw materials as claimed in claim 1, characterized in that the synthesis of urea is at a temperature of 160-210°C, a pressure of 13-24MPa, ammonia carbon The molar ratio is 2.8-4.5, and the water-to-carbon molar ratio is 0.4-0.8, and the urea synthesis reaction is carried out. The synthesis process is the full circulation method of aqueous solution, gas stripping method, combined urea method, SRR method or HR method of UTI company. 15. A polygeneration process using coal-based gas and coke oven gas as raw materials as claimed in claim 1, characterized in that the first condensation temperature is: -70～-85°C, and the pressure is: 1.5-4.5MPa; second condensation temperature: -160～-175℃, pressure: 1.5-4.5MPa. 16. A polygeneration process using coal-based gas and coke oven gas as raw materials as claimed in claim 1, characterized in that the power generation uses a gas turbine, preheating the tail gas to 100-500°C, and air The volume ratio is 1:2~4, the total pressure is 0.5MPa~2.0MPa, and the mixture is fed into a gas turbine for combustion and power generation at 800~1600°C.

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