CN104152199B - Technology for preparing natural gas through sulfur resistant methanation by coal-prepared synthesis gases - Google Patents

Abstract

A process for preparing natural gas by sulfur-resistant methanation of coal-based synthesis gas. The invention is to simultaneously carry out secondary sulfur-resistant conversion and methanation reaction of coal-based synthesis gas on a molybdenum-based bifunctional catalyst, and then elute it with low-temperature methanol to remove Acid gas, and finally unreacted CO and _H2 are subjected to secondary methanation reaction through Ni-based methanation catalyst to obtain excellent natural gas products. The invention has the advantages of simple process flow, less equipment investment, low comprehensive energy consumption and excellent natural gas products.

Description

A process for preparing natural gas by sulfur-resistant methanation of coal-to-synthesis gas

technical field

The invention belongs to a process for producing natural gas from coal, in particular to a process for producing natural gas through sulfur-resistant methanation of synthetic gas produced from coal.

Background technique

my country is rich in coal, poor in oil and low in gas, and the proportion of natural gas consumption is far lower than the world average. In recent years, with the rapid increase of natural gas demand in my country, the gap between domestic natural gas supply and demand has gradually increased, which in turn has restricted the steady and rapid development of my country's national economy. Coal-to-natural gas is a process technology for producing natural gas from coal. It can convert coal into CH ₄ , a clean fuel that is convenient for long-distance transportation.

Methanation is the core technology of coal-to-natural gas, specifically the synthesis of methane from CO, CO ₂ and H ₂ in synthesis gas at a certain temperature, pressure and catalyst. At present, the industrial methanation technology is mainly mastered by a few companies such as Lurgi in Germany, Topsoe in Denmark and Davy in the UK. The above-mentioned technologies all use a supported nickel-based catalyst with excellent catalytic performance, but the catalyst has poor anti-coking ability and poor performance. Due to the disadvantage of sulfur resistance, it is necessary to adjust the H/C in the syngas to about 3 before methanation, and at the same time remove the sulfur to below 0.1ppm. In order to meet the requirements of nickel-based catalysts for synthesis gas, the industrial coal-to-natural gas process is equipped with a sulfur-tolerant conversion unit and an acid gas removal unit before methanation. The specific process flow is shown in Figure 1. Although coal-to-natural gas is the best choice for coal cleanliness and optimal utilization, there are still many problems in the above-mentioned industrial coal-to-natural gas technology due to the limitation of methanation nickel-based catalysts: (1) The low-temperature methanol washing makes the synthesis gas have to undergo "thermal (transformation) )-cold (methanol washing)-heat (methanation)-cold (cooling compression)", the temperature has been varied from 300 to 400°C to -40°C for many times, greatly increasing equipment investment, energy consumption and operating costs; ( 2) The separate sulfur-resistant conversion unit not only increases equipment investment and energy consumption, but also due to the low heat release of water vapor conversion, when the syngas temperature and water vapor content fluctuate, it often encounters the phenomenon that the conversion temperature is too low , so that the organic sulfur in the synthesis gas cannot be completely converted into inorganic sulfur, thereby affecting the subsequent sulfur recovery efficiency; (3) Methanation is a strong exothermic reaction. Dilution greatly increases the cycle equipment investment and cycle energy consumption. Therefore, in order to overcome the problems existing in the existing coal-to-natural gas technology and respond to the national call for energy conservation and emission reduction, it is of great significance to develop a new coal-to-natural gas technology with simple process flow, low equipment investment, low comprehensive energy consumption and excellent natural gas products. Significance.

The molybdenum-based sulfur _- tolerant methanation catalyst uses MoS2 as the active center, not only has no upper limit requirement for the sulfur content in the synthesis gas, but also has the same active components as the sulfur-tolerant shift catalyst, and has sulfur-tolerant shift and sulfur-tolerant methanation at the same time The dual function has become a research hotspot of many institutions and scientific research institutes at home and abroad. Patent CN103480362A discloses a preparation method of a supported sulfur-resistant methanation catalyst. _The invention uses Mo, W and V as active components, Co, Ni, La and K as auxiliary agents, and _Al2O3 or _ZrO2 as The carrier is used to prepare a sulfur-resistant methanation catalyst through a precipitation method, and the catalyst has the advantages of simple preparation process and good sulfur-resistant performance. Patent CN103495421A prepared a magnesium-aluminum spinel-supported cobalt-molybdenum sulfur-resistant methanation catalyst by kneading method or impregnation method. The catalyst can be used in the pressure range of 0-6 MPa, and the catalyst has good strength and stability. Patent CN10343326A discloses a highly stable sulfur-resistant methanation catalyst supported by ZrO ₂ , in which Y ₂ O ₃ and Mo ₂ O ₃ are successively supported on the ZrO ₂ carrier by a step-by-step impregnation method, wherein the Y ₂ O ₃ part can be Instead of MgO, CaO and/or Cr ₂ O ₃ , the catalyst exhibited high methanation activity and high stability in high hydrogen sulfide atmosphere.

Considering the problems existing in the existing methanation technology, if the Mo-based bifunctional catalyst can be applied to the coal-to-natural gas technology, the sulfur-tolerant shift and the methanation reaction can be completed in one step, and then the acid gas can be eluted with low-temperature methanol Obtaining natural gas products not only saves the equipment investment and energy consumption of the transformation unit, avoids the problem of "cold and heat disease" existing in the existing process, but also because the methanation reaction is a reaction of reduced volume, the processing capacity of the low-temperature methanol washing is greatly increased reduce. The above-mentioned patents optimize the composition of Mo-based catalysts, types of additives, types of supports, and preparation methods. Most of the purposes are to improve the thermal stability of the catalyst and reduce the preparation cost, but the activity and methane selectivity of the catalyst are still low. The inventors of this patent have further researched and found that when shift and methanation are carried out simultaneously under the dual-function catalyst, three reactions of methanation, water vapor shift and reverse water gas shift inevitably occur, while the syngas prepared by the existing coal gasification technology Both contain a large amount of CO ₂ , especially the CO ₂ volume content in the synthesis gas of crushed coal pressurized gasification used in coal-to-natural gas technology is as high as 28%, and the CO ₂ content will further increase after conversion and methanation, A large amount of _CO2 will lead to the occurrence of reverse water shift reaction, which greatly reduces the conversion rate of CO. After the acid gas is eluted with low-temperature methanol, there are still a large amount of unconverted CO and _H2 gas in the product gas, which affects the quality of natural gas. , limiting its industrial application.

Contents of the invention

The purpose of the present invention is to develop a process for preparing natural gas by sulfur-resistant methanation of coal-to-synthesis gas with simple process flow, low equipment investment, low comprehensive energy consumption and excellent natural gas products.

In the present invention, the coal-to-synthesis gas is carried out simultaneously on the molybdenum-based bifunctional catalyst for sulfur-tolerant shift and methanation reaction, then the acid gas is eluted by low-temperature methanol, and finally the unreacted CO and _H2 are depleted by the Ni-based methanation catalyst. Perform secondary methanation reaction to obtain excellent natural gas products.

In order to achieve the above purpose, the inventors of this patent have mastered the reaction rules of sulfur-resistant conversion and sulfur-resistant methanation of synthesis gas on molybdenum-based bifunctional catalysts through numerous catalyst preparations, activity evaluations, theoretical calculations and software simulations, and obtained Based on a large amount of basic data of gas composition and reaction conditions, combined with years of experience in coal-to-natural gas engineering design, it is proposed that the synthesis gas generated by gasification first undergoes a two-stage sulfur-tolerant methanation reaction, and by selecting appropriate reaction conditions such as temperature, Pressure, space velocity and water-gas ratio, etc. not only greatly increase the methane content in the sulfur-resistant methanation product gas, but also adjust the H ₂ /CO to between 3.0 and 3.3; the sulfur-resistant methanation product gas is washed with low-temperature methanol After removal of acid gas (CO ₂ +H ₂ S), a secondary methanation reaction is carried out under the action of a nickel-based catalyst. After cooling and gas-liquid separation, a natural gas product with a volume content of methane ≥ 96% is obtained. Compared with the existing industrial methanation process, the sulfur-tolerant methanation process proposed by the present invention does not require an independent conversion unit, the process is simpler, and the equipment investment and energy consumption of the conversion are reduced. The equipment investment and energy consumption of low-temperature methanol washing are also greatly reduced, which has great industrial value and potential.

The invention discloses a process for preparing natural gas through sulfur-resistant methanation of coal-based synthesis gas, and the specific process route is as follows:

(1) The synthetic gas after dedusting and oil removal first passes through the inlet and outlet heat exchanger II to exchange heat with the outlet gas of the sulfur-tolerant methanation reactor II, and then passes through the inlet and outlet heat exchanger I and the sulfur-tolerant methanation reactor I to exit After heat exchange, the gas is mixed with steam and then enters the sulfur-tolerant methanation reactor I from the top, and the first-stage sulfur-tolerant methanation and sulfur-tolerant shift reaction are carried out on the molybdenum-based bifunctional catalyst, and the outlet gas first passes through the high-pressure waste heat boiler I recover heat, and after exchanging heat with the synthesis gas through the inlet and outlet heat exchanger I, go to the sulfur-resistant methanation reactor II;

(2) The reaction gas from the sulfur-tolerant methanation reactor I enters the sulfur-tolerant methanation reactor II from the top, and the second-stage sulfur-tolerant methanation and sulfur-tolerant shift reaction are carried out on the molybdenum-based bifunctional catalyst. The heat is recovered through the high-pressure waste heat boiler II, and then heat exchanged with the synthesis gas through the inlet and outlet heat exchanger II, and further cooled by the air cooler I, and then enters the gas-liquid separation tank I for gas-liquid separation, and the condensate is discharged from the bottom of the separation tank I , and the gas phase enters the low-temperature methanol washing system after being discharged from the top of the separation tank, and after the carbon dioxide and hydrogen in the gas are eluted by low-temperature methanol, it is sent to the methanation reactor 1 where the Ni-based catalyst is housed;

(3) The gas washed from low-temperature methanol first exchanges heat with the outlet gas of the methanation reactor II through the inlet and outlet heat exchanger IV, and then exchanges heat with the outlet gas of the methanation reactor I through the inlet and outlet heat exchanger III , enters the methanation reactor I from the top, and carries out the first-stage methanation reaction under the catalysis of the Ni-based methanation catalyst. After heat exchange, the incoming gas enters the methanation reactor II from the top, and carries out the second-stage methanation reaction under the action of the Ni-based methanation catalyst. Since then, the CO in the synthesis gas is completely converted into _CH4 gas, and the methanation The outlet gas of the reactor II first passes through the inlet and outlet heat exchanger IV to exchange heat with the gas from the low-temperature methanol washing system, then after being cooled by the air cooling II and the water cooler, it enters the gas-liquid separation tank II for gas-liquid separation, and the condensate is self-separated The bottom of the tank II is discharged, and the natural gas product is discharged from the top of the separation tank II, which is sent to the natural gas pipeline after being dried and compressed.

The synthesis gas mentioned above is produced by Lurgi crushed coal pressurized gasification technology, and the composition of the synthesis gas is H ₂ 37-40%, CO 17-20%, CO ₂ 28-33%, CH ₄ 8%- 12%, N ₂ 0.1-0.4%.

The mass composition of the molybdenum-based bifunctional catalyst as described above is: active component MoO ₃ 10-35wt%, auxiliary agent oxide 2-20wt%, carrier 50-85wt%, wherein the auxiliary agent is Co, La, Ce, Zr, One or more of Fe, Ni and K, preferably Co, La, Ce, Zr; the carrier is γ-Al ₂ O ₃ , SiO ₂ , magnesium aluminum spinel, ZrO ₂ , CeO ₂ -Al ₂ O ₃ composite carrier and Al ₂ O ₃ -ZrO ₂ composite carrier, and preferably magnesium aluminum spinel, CeO ₂ -Al ₂ O ₃ composite carrier and Al ₂ O ₃ -ZrO ₂ composite carrier; Precipitation method or sol-gel method is used to load on the carrier. For the impregnation method, refer to patent 102463118A or CN103495421A. For the co-precipitation method, refer to patent CN103480362A. For the sol-gel method, refer to patent CN101733115A.

Both the sulfur-tolerant methanation reactor I and the sulfur-tolerant methanation reactor II mentioned above are fixed-bed adiabatic reactors.

The volume ratio of water vapor and synthesis gas in the inlet of the sulfur-resistant methanation reactor I mentioned above is 0.1-0.3, the inlet gas temperature after mixing is 270-300°C, the outlet gas temperature is 500-600°C, and the reaction pressure is 2.0-7.0 MPa, the reaction space velocity is 2000~8000h ^-1 .

The inlet gas temperature of the above-mentioned sulfur-tolerant methanation reactor II is 270-300°C, the outlet gas temperature is 450-550°C, the reaction pressure is 2.0-7.0MPa, and the reaction space velocity is 2000-8000h ^-1 .

The above-mentioned low-temperature methanol washing is composed of a desulfurization tower and a decarbonization tower. The operating temperature is -20~-60°C and the operating pressure is 2.0~7.0MPa. After the low-temperature methanol washing, the sulfur in the gas is removed to 0.01~0.1ppm, and the CO ₂ volume content off to 0.3 ~ 0.8V%.

The Ni-based catalyst used in the above-mentioned methanation reactors I and II is Topsoe's MCR-2X methanation catalyst, Davy's CEG-LH methanation catalyst or a wide-temperature catalyst developed by the Dalian Institute of Physical Chemistry. A type of methanation catalyst, wherein the mass composition of the catalyst developed by Dalian Institute of Physical Chemistry in terms of oxides is: active component NiO 10-75%, additive La ₂ O ₃ 0.1-15% and carrier Al ₂ The balance of O ₃ -ZrO ₂ , the auxiliary agent is lanthanum oxide or the combination of lanthanum oxide and nickel-lanthanum compound, and the carrier is the composition of alumina, nickel-aluminum compound and zirconia. The preparation steps and conditions are detailed in patent CN102029162.

As mentioned above, both the methanation reactor I and the methanation reactor II are fixed-bed adiabatic reactors.

The inlet gas temperature of the methanation reactor I is 270-300°C, the outlet gas temperature is 450-620°C, the reaction pressure is 2.0-7.0MPa, and the reaction space velocity is 2000-8000h ^-1 ;

The inlet gas temperature of the methanation reactor II is 250-300°C, the outlet gas temperature is 290-350°C, the reaction pressure is 2.0-7.0MPa, and the reaction space velocity is 2000-8000h ^-1 .

The volume composition of the above-mentioned syngas after the above process and reaction of natural gas is: CH ₄ 96-98%, CO ₂ 0.2-0.5, H ₂ 0.5-2%, N ₂ 0.6-1.2%, C _2-6 0.3-0.5%.

Compared with the prior art, the present invention has substantive features and remarkable progress in that:

(1) The coal-to-synthesis gas sulfur-resistant methanation process developed by the present invention combines sulfur-tolerant conversion and sulfur-resistant methanation. Compared with the existing industrial coal-to-natural gas process, it reduces the number of separate sulfur-resistant conversion units and saves conversion Equipment investment and operating costs.

(2) In the traditional coal-to-natural gas process, natural gas is finally produced from synthetic gas through sulfur-resistant conversion, low-temperature methanol washing and methanation, but in the present invention, low-temperature methanol elution is performed to remove acid gas after sulfur-resistant conversion and sulfur-resistant methanation. Since methanation is a molecular reduction reaction, the amount of gas after sulfur-tolerant methanation and sulfur-tolerant transformation is reduced by about 20%, which reduces the equipment size and energy consumption of low-temperature methanol washing.

(3) The present invention sets up two methanation reactors that are packed with nickel-based catalyst after washing with low-temperature methanol, so that due to _CO Excessive and inverse water-steam shift cause part of the unreacted _CO and H Conversion is complete, the product gas The methane content is as high as over 96%, fully utilizing the advantages of the sulfur-tolerant shift and methanation dual-function catalyst, and making up for the disadvantages of the catalyst.

(4) During sulfur-resistant methanation, because there are a large amount of CO ₂ with excellent heat capacity and supplementary water vapor in the gas, the reaction temperature of the sulfur-resistant methanation bed can be effectively controlled without dilution of the gas; After methanation and acid gas removal, since the gas contains a large amount of CH ₄ gas, and the proportion of effective gases such as CO and H ₂ is low, there is no need to circulate gas to remove heat during the methanation process. Therefore, compared with industrial coal-to-natural gas, the present invention significantly reduces cycle compressor investment and cycle energy consumption.

(5) The present invention combines sulfur-resistant change and sulfur-resistant methanation. Due to the strong exothermic reaction of methanation, the temperature of sulfur-resistant conversion is increased, which avoids the inability to realize organic sulfur conversion due to too low temperature in the process of sulfur-resistant conversion alone. The conversion of inorganic sulfur affects the problem of sulfur recovery.

Description of drawings

Fig. 1 is a prior art coal-to-synthesis gas methanation synthesis natural gas process.

Figure 2 is a new process for coal-to-synthesis gas synthesis of natural gas by sulfur-resistant methanation

As shown in the figure, 1 is sulfur-resistant methanation reactor I, 2 is sulfur-resistant methanation reactor II, 3 is methanation reactor I, 4 is methanation reactor II, 5 is low-temperature methanol washing system, and 6 is Gas-liquid separation tank I, 7 is gas-liquid separation tank II, 8 is air cooler I, 9 is air cooler II, 10 is waste heat boiler I, 11 is waste heat boiler II, 12 is waste heat boiler III, 13 is inlet and outlet materials Heat exchanger I, 14 is the inlet and outlet heat exchanger II, 15 is the inlet and outlet heat exchanger III, 16 is the inlet and outlet heat exchanger IV, and 17 is a water cooler.

detailed description

The present invention's process and conditions are proposed on the basis of screening numerous Mo-based sulfur-resistant catalysts and Ni-based methanation industrial catalysts. In the implementation process, if it is an industrial catalyst, the present invention will provide the catalyst model. If it is from other Invented catalyst, the present invention will give its composition or source.

The specific embodiments of the present invention will be further described in detail below through specific examples, but it should not be understood that the scope of the present invention is limited to the above-mentioned examples.

Example 1

In this example, the catalysts used in sulfur-tolerant methanation reactor I and sulfur-tolerant methanation reactor II are the same, and the mass composition of oxides is MoO ₃ 25wt%-Co ₂ O ₃ +ZrO ₂ 15wt%/CeO ₂ - Al ₂ O ₃ 60wt% catalyst, active component MoO ₃ and auxiliary agent Co ₂ O ₃ +ZrO ₂ are supported on the carrier CeO ₂ -Al ₂ O ₃ by means of impregnation, the specific preparation method and process are shown in Example 5 of CN102463118A ; The nickel-based catalyst in methanation reactor I and methanation reactor II adopts Topsoe's MCR-2X catalyst. Adopt above-mentioned catalyzer, its concrete technological process and condition are as follows:

(1) After dedusting and oil removal, the synthesis gas whose volume composition is H ₂ 39%, CO 19.6%, CO ₂ 31.5%, CH ₄ 9.5% and N ₂ 0.4% first passes through the inlet and outlet heat exchanger II and sulfur-resistant methanation The outlet gas of reactor II is heat-exchanged, and then through the inlet and outlet heat exchanger I and the outlet gas of sulfur-tolerant methanation reactor I, the heat exchange reaches 270°C, and it is mixed with water vapor and then enters sulfur-tolerant methanation reactor I from the top , the molar ratio of water vapor to synthesis gas is 0.30, under the reaction conditions of pressure 4.5MPa and space velocity 8000h ^-1 , in the supported MoO ₃ 25wt%-Co ₂ O ₃ +ZrO ₂ 15wt%/CeO ₂ -Al ₂ O ₃ 60wt% dual-function catalyst is used for the first-stage sulfur-tolerant methanation and sulfur-tolerant shift reactions. The outlet gas with a temperature of 600°C passes through the high-pressure waste heat boiler I successively to recover heat, and then passes through the inlet and outlet heat exchanger I to exchange heat with the synthesis gas. After reaching 270°C, go to sulfur-tolerant methanation reactor II;

(2) The reaction gas from sulfur-tolerant methanation reactor I enters sulfur ^- tolerant methanation reactor II from the top, under the reaction conditions _of pressure 4.5MPa and space velocity 8000h ₂ O ₃ +ZrO ₂ 15wt%/CeO ₂ -Al ₂ O ₃ 60wt% bifunctional catalyst for the second-stage sulfur-tolerant methanation and sulfur-tolerant shift reaction, the outlet gas at a temperature of 550 is first passed through the high-pressure waste heat boiler II to recover heat , and then exchange heat with the synthesis gas through the inlet and outlet heat exchanger II, and then enter the gas-liquid separation tank I for gas-liquid separation after further cooling by the air cooler I, the condensate is discharged from the bottom of the separation tank I, and the gas phase discharged from the top of the separation tank After entering the low-temperature methanol washing system, under the conditions of -40°C and 4.5Mpa, CO ₂ and H ₂ S are eluted by low-temperature methanol, in which H ₂ S is removed to 0.03ppm, and CO ₂ is removed to a volume content of 0.5% , is sent to the methanation reactor I that nickel-based catalyst is housed then;

(3) The gas washed from the low-temperature methanol is first exchanged with the outlet gas of the methanation reactor II through the inlet and outlet heat exchanger IV, and then through the inlet and outlet heat exchanger III and the outlet gas of the methanation reactor I. After 270°C, enter the methanation reactor I equipped with MCR ^- 2X catalyst from the top, and perform primary methanation reaction under the conditions of pressure 4.5MPa and space velocity 5000h Boiler III recovers heat, and after heat exchange with the gas washed by low-temperature methanol through inlet and outlet heat exchanger III to 250°C, it enters into MCR-2X methanation reactor II from the top, under pressure of 4.5MPa and space velocity of 5000h Under the condition of ^-1 , the secondary methanation reaction is carried out, since then the CO in the synthesis gas is completely converted into CH ₄ gas, and the gas with a temperature of 350 ° C first passes through the inlet and outlet heat exchanger IV to exchange heat with the gas from the low-temperature methanol washing system, After being cooled by the air cooler II and water cooler, it enters the gas-liquid separation tank II. The condensate is discharged from the bottom of the separation tank II, and the product discharged from the top of the separation tank II is the natural gas product, which is sent to the natural gas pipeline after being dried and compressed.

See attached table 1 for the composition of raw material gas and natural gas product synthesized under reaction conditions in this embodiment.

Example 2

In this example, the catalysts used in sulfur-tolerant methanation reactor I and sulfur-tolerant methanation reactor II are the same, and the mass composition of oxides is MoO ₃ 30wt%-Co ₂ O ₃ +Fe ₂ O ₃ +NiO 20wt% /CeO ₂ -Al ₂ O ₃ 50wt% catalyst, the active component MoO ₃ and the auxiliary agent Co ₂ O ₃ +Fe ₂ O ₃ +NiO are loaded on the carrier CeO ₂ -Al ₂ O ₃ by impregnation, and the specific preparation For the method and process, see Example 5 of CN102463118A; the nickel-based catalysts of Methanation Reactor I and Methanation Reactor II adopt Topsoe's MCR-2X catalyst. Adopt above-mentioned catalyzer, its concrete technological process and condition are as follows:

(1) After dedusting and oil removal, the synthesis gas whose volume composition is H ₂ 40%, CO 20%, CO ₂ 31.7%, CH ₄ 8.0% and N ₂ 0.3% first passes through the inlet and outlet heat exchanger II and sulfur-resistant methanation The outlet gas of reactor II is heat-exchanged, and then through the inlet and outlet heat exchanger I and the outlet gas of sulfur-tolerant methanation reactor I, the heat exchange reaches 275°C, and it is mixed with water vapor and then enters sulfur-tolerant methanation reactor I from the top , the molar ratio of water vapor to synthesis gas is 0.25, under the reaction conditions of pressure 4.0MPa and space velocity 7500h ^-1 , the supported MoO ₃ 30wt%-Co ₂ O ₃ +Fe ₂ O ₃ +NiO20wt%/CeO ₂ - Al ₂ O ₃ 50wt% dual-function catalyst is used to carry out the first-stage sulfur-tolerant methanation and sulfur-tolerant shift reaction, and the outlet gas with a temperature of 583°C passes through the high-pressure waste heat boiler I successively to recover heat, and passes through the inlet and outlet heat exchanger I and the raw material After the gas heat exchange reaches 275°C, go to the sulfur-tolerant methanation reactor II;

(2) The reaction gas from the sulfur-tolerant methanation reactor I enters the sulfur-tolerant methanation reactor II from the top, under the reaction conditions _of pressure 4.0MPa and space velocity ^7500h ₂ O ₃ +Fe ₂ O ₃ +NiO 20wt%/CeO ₂ -Al ₂ O ₃ 50wt% bifunctional catalyst for the second-stage sulfur-tolerant methanation and sulfur-tolerant shift reaction, the outlet gas at a temperature of 53°C first passes through high-pressure waste heat Boiler II recovers heat, and then exchanges heat with syngas through inlet and outlet heat exchanger II, and is further cooled by air cooler I, then enters gas-liquid separation tank I for gas-liquid separation, condensate is discharged from the bottom of separation tank I, and the separation tank The gas phase discharged from the top enters the low-temperature methanol washing system. After CO ₂ and H ₂ S are eluted by low-temperature methanol under the conditions of -35°C and 4.0Mpa, H ₂ S is removed to 0.04ppm, while CO ₂ is removed to Volume content 0.55%, then sent to the methanation reactor I that nickel-based catalyst is housed;

(3) The gas washed from the low-temperature methanol is first exchanged with the outlet gas of the methanation reactor II through the inlet and outlet heat exchanger IV, and then through the inlet and outlet heat exchanger III and the outlet gas of the methanation reactor I. After 275°C, enter the methanation reactor I equipped with MCR-2X catalyst from the top, and carry out the primary methanation reaction under the conditions of pressure 4.0MPa and space velocity ^6000h Boiler III recovers heat, and after heat exchange with the gas washed by low-temperature methanol through inlet and outlet heat exchanger III to reach 255°C, it enters into MCR-2X methanation reactor II from the top, at a pressure of 4.0MPa and a space velocity of 6000h The second-stage methanation reaction is carried out under the condition of ^-1 , since then the CO in the synthesis gas is completely converted into CH ₄ gas, and the gas at a temperature of 324°C first passes through the inlet and outlet heat exchanger IV to exchange heat with the gas from the low-temperature methanol washing system, After being cooled by the air cooler II and water cooler, it enters the gas-liquid separation tank II. The condensate is discharged from the bottom of the separation tank II, and the product discharged from the top of the separation tank II is the natural gas product, which is sent to the natural gas pipeline after being dried and compressed.

See attached table 1 for the composition of raw material gas and natural gas product synthesized under reaction conditions in this embodiment.

Example 3

In this example, the catalysts used in sulfur-tolerant methanation reactor I and sulfur-tolerant methanation reactor II are the same, and their mass composition is the catalyst of MoO ₃ 35wt%-Co ₂ O ₃ +KO ₂ 2wt%/ZrO ₂ 63wt% , the active component MoO ₃ and the auxiliary agent Co ₂ O ₃ +KO ₂ are loaded on the carrier ZrO ₂ by impregnation, and the specific preparation method and process are shown in Example 14 of CN103495421A; Methanation Reactor I and Methanation Reactor II The nickel-based catalyst is Davy's CEG-LH catalyst. Adopt above-mentioned catalyzer, its concrete technological process and condition are as follows:

(1) After dedusting and oil removal, the synthesis gas whose volume composition is H ₂ 40%, CO 20%, CO ₂ 30.3%, CH ₄ 9.5% and N ₂ 0.2% first passes through the inlet and outlet heat exchanger II and sulfur-resistant methanation The outlet gas of reactor II is heat-exchanged, and then through the inlet and outlet heat exchanger I and the outlet gas of sulfur-tolerant methanation reactor I, the heat exchange reaches 280°C, and it is mixed with water vapor and then enters sulfur-tolerant methanation reactor I from the top , the molar ratio of water vapor to synthesis gas is 0.20, under the reaction conditions of pressure 3.5MPa and space velocity 7000h ^-1 , the supported MoO ₃ 35wt%-Co ₂ O ₃ +KO ₂ 2wt%/ZrO ₂ 63wt% bis The first-level sulfur-tolerant methanation and sulfur-tolerant shift reactions are carried out on the functional catalyst. The outlet gas with a temperature of 583 °C passes through the high-pressure waste heat boiler I successively to recover heat, and after the heat exchange with the raw material gas reaches 280 °C through the inlet and outlet heat exchanger I, Desulfur-resistant methanation reactor II;

(2) The reaction gas from sulfur-tolerant methanation reactor I enters sulfur-tolerant methanation reactor II from the top, under the reaction conditions _of pressure 3.5MPa and space velocity ^7000h ₂ O ₃ +KO ₂ 2wt%/ZrO ₂ 63wt% bifunctional catalyst for the second-stage sulfur-tolerant methanation and sulfur-tolerant shift reaction. The outlet gas with a temperature of 521°C first passes through the high-pressure waste heat boiler II to recover heat, and then passes through the The material heat exchanger II exchanges heat with the synthesis gas, and is further cooled by the air cooler I before entering the gas-liquid separation tank I for gas-liquid separation. The condensate is discharged from the bottom of the separation tank I, and the gas phase discharged from the top of the separation tank enters the low-temperature methanol wash system, under the conditions of -45°C and 3.5Mpa, CO ₂ and H ₂ S are eluted by low-temperature methanol, in which H ₂ S is removed to 0.05ppm, and CO ₂ is removed to a volume content of 0.60%, and then sent to Methanation reactor I equipped with a nickel-based catalyst;

(3) The gas washed from the low-temperature methanol is first exchanged with the outlet gas of the methanation reactor II through the inlet and outlet heat exchanger IV, and then through the inlet and outlet heat exchanger III and the outlet gas of the methanation reactor I. After 280°C, it enters the methanation reactor I equipped with MCR-2X catalyst from the top, and performs primary methanation reaction under the conditions of pressure 3.5MPa and space velocity ^7000h Boiler III recovers heat, and after heat exchange with the gas washed by low-temperature methanol through inlet and outlet heat exchanger III to reach 260°C, it enters into MCR-2X methanation reactor II from the top, under the pressure of 3.5MPa and space velocity of 7000h Under the condition of ^-1 , the secondary methanation reaction is carried out, since then the CO in the synthesis gas is completely converted into CH ₄ gas, and the gas with a temperature of 319 ° C first passes through the inlet and outlet heat exchanger IV to exchange heat with the gas from the low-temperature methanol washing system, After being cooled by the air cooler II and water cooler, it enters the gas-liquid separation tank II. The condensate is discharged from the bottom of the separation tank II, and the product discharged from the top of the separation tank II is the natural gas product, which is sent to the natural gas pipeline after being dried and compressed.

See attached table 1 for the composition of raw material gas and natural gas product synthesized under reaction conditions in this embodiment.

Example 4

In this example, the catalysts used in sulfur-tolerant methanation reactor I and sulfur-tolerant methanation reactor II are the same, and their mass composition is MoO ₃ 13wt%-ZrO ₂ 14.5wt%/γ-Al ₂ O ₃ 72.5wt% Catalyst, active component MoO ₃ and auxiliary agent ZrO ₂ are supported on γ-Al ₂ O ₃ by co-precipitation, the specific preparation method and process are shown in Example 7 of CN103480362A; in methanation reactor I and methanation reactor II The mass composition of the nickel-based catalyst is NiO 40wt%-La ₂ O ₃ 7wt%-Al ₂ O ₃ 43wt%-ZrO ₂ 7wt%. The specific preparation method and steps are shown in Example 5 of CN102029162A. Adopt above-mentioned catalyzer, its concrete technological process and condition are as follows:

(1) After dedusting and oil removal, the synthesis gas whose volume composition is H ₂ 37%, CO 20%, CO ₂ 30.7%, CH ₄ 12% and N ₂ 0.3% first passes through the inlet and outlet heat exchanger II and sulfur-resistant methanation The outlet gas of reactor II is heat-exchanged, and then passes through the inlet and outlet heat exchanger I and the outlet gas of sulfur-tolerant methanation reactor I is heat-exchanged to 285°C, and is mixed with water vapor and then enters sulfur-tolerant methanation reactor I from the top , the molar ratio of water vapor to synthesis gas is 0.15, under the reaction conditions of pressure 3.0MPa and space velocity 6500h ^-1 , in supported MoO ₃ 13wt%-ZrO ₂ 14.5wt%/γ-Al ₂ O ₃ 72.5wt% The first-stage sulfur-tolerant methanation and sulfur-tolerant shift reactions are carried out on the dual-function catalyst. The outlet gas with a temperature of 571°C passes through the high-pressure waste heat boiler I successively to recover heat, and then exchanges heat with the raw material gas through the inlet and outlet heat exchanger I to reach 285°C. , to the sulfur-tolerant methanation reactor II;

(2) The reaction gas from the sulfur-tolerant methanation reactor I enters the sulfur-tolerant methanation reactor II from the top, under the reaction conditions _of pressure 3.0MPa and space velocity ^6500h ₂ 14.5wt%/γ-Al ₂ O ₃ 72.5wt% dual-function catalyst for the second-stage sulfur-tolerant methanation and sulfur-tolerant shift reaction, the outlet gas at a temperature of 507°C first passes through the high-pressure waste heat boiler II to recover heat, and then passes through The inlet and outlet heat exchanger II exchanges heat with the synthesis gas, and is further cooled by the air cooler I before entering the gas-liquid separation tank I for gas-liquid separation. The condensate is discharged from the bottom of the separation tank I, and the gas phase discharged from the top of the separation tank enters the low-temperature methanol Wash the system, and remove CO 2 and H 2 S by eluting CO ₂ and H ₂ S with low-temperature methanol under the conditions of -60°C and 3.0Mpa, wherein H ₂ S is removed to 0.02ppm, and CO ₂ is removed to a volume content of 0.40%, and then sent to To methanation reactor I equipped with nickel-based catalyst;

(3) The gas washed from the low-temperature methanol is first exchanged with the outlet gas of the methanation reactor II through the inlet and outlet heat exchanger IV, and then through the inlet and outlet heat exchanger III and the outlet gas of the methanation reactor I. After 285°C, enter the methanation reactor I equipped with NiO 40wt%-La ₂ O ₃ 7wt%-Al ₂ O ₃ 43wt%-ZrO ₂ 7wt% catalyst from the top, at a pressure of 3.0MPa and a space velocity of 6500h ^-1 The first-stage methanation reaction is carried out under the conditions. The outlet gas with a temperature of 569°C first passes through the waste heat boiler III to recover heat, and after the heat exchange with the gas washed by low-temperature methanol through the inlet and outlet heat exchanger III reaches 265°C, it enters the device from the top. There are _NiO40wt % _-La2O37wt % _-Al2O343wt % _-ZrO27wt % in methanation reactor _II , under the conditions of pressure 3.0MPa and space velocity 6500h ^-1 , carry out secondary methanation reaction, since then The CO in the synthesis gas is completely converted into _CH4 gas. The gas with a temperature of 312 °C first passes through the inlet and outlet heat exchanger IV to exchange heat with the gas from the low-temperature methanol washing system, and then enters the gas after being cooled by the air cooler II and water cooler. Liquid separation tank II, the condensate is discharged from the bottom of the separation tank II, and the discharge from the top of the separation tank II is the natural gas product, which is sent to the natural gas pipeline after being dried and compressed.

See attached table 1 for the composition of raw material gas and natural gas product synthesized under reaction conditions in this embodiment.

Example 5

In this example, the catalysts used in sulfur-tolerant methanation reactor I and sulfur-tolerant methanation reactor II are the same, and their mass composition is MoO ₃ 13wt%-Co ₂ O ₃ +CeO ₂ 14.5wt%/γ-Al ₂ O ₃ 72.5 wt% of the catalyst, the active component MoO ₃ and the additives Co ₂ O ₃ +ZrO ₂ +CeO ₂ are loaded on the carrier γ-Al ₂ O ₃ by co-precipitation, the specific preparation method and process are shown in the example of CN103480362A 5. The mass composition of nickel-based catalysts in methanation reactor I and methanation reactor _II is _NiO75wt % _-La2O37wt % _-Al2O315wt % _-ZrO23wt %, specific preparation methods and steps see CN102029162A Example 4. Adopt above-mentioned catalyzer, its concrete technological process and condition are as follows:

(1) After dedusting and oil removal, the synthesis gas whose volume composition is H ₂ 37.3%, CO 20%, CO ₂ 30.4%, CH ₄ 12% and N ₂ 0.3% first passes through the inlet and outlet heat exchanger II and sulfur-resistant methanation The outlet gas of reactor II is heat-exchanged, and then through the inlet and outlet heat exchanger I and the outlet gas of sulfur-tolerant methanation reactor I, the heat exchange reaches 290°C, and it is mixed with water vapor and then enters sulfur-tolerant methanation reactor I from the top , the molar ratio of water vapor to synthesis gas is 0.10, under the reaction conditions of pressure 2.0MPa and space velocity 6000h ^-1 , the supported MoO ₃ 13wt%-Co ₂ O ₃ +CeO ₂ 14.5wt%/γ-Al ₂ The first-stage sulfur-tolerant methanation and sulfur-tolerant shift reactions are carried out on the O ₃ 72.5wt% dual-function catalyst. The outlet gas with a temperature of 557°C passes through the high-pressure waste heat boiler I successively to recover heat, and passes through the inlet and outlet heat exchanger I to exchange with the raw material gas. After the heat reaches 290°C, go to the sulfur-resistant methanation reactor II;

(2) The reaction gas from sulfur-tolerant methanation reactor I enters sulfur-tolerant methanation reactor II from the top, under the reaction conditions _of pressure ^2.0MPa and space velocity 6000h ₂ O ₃ +CeO ₂ 14.5wt%/γ-Al ₂ O ₃ 72.5wt% bifunctional catalyst for the second-stage sulfur-tolerant methanation and sulfur-tolerant shift reaction, the outlet gas at 496°C first passes through the high-pressure waste heat boiler II Recover heat, then exchange heat with the synthesis gas through the inlet and outlet heat exchanger II, and then enter the gas-liquid separation tank I for gas-liquid separation after further cooling through the air cooler I, the condensate is discharged from the bottom of the separation tank I, and the top of the separation tank The gas phase of the gas enters the low-temperature methanol washing system, and the CO ₂ and H ₂ S are eluted by low-temperature methanol under the conditions of -50°C and 2.0Mpa, in which H ₂ S is removed to 0.06ppm, while CO ₂ is removed to the volume content 0.70%, then sent to the methanation reactor I equipped with nickel-based catalyst;

(3) The gas washed from the low-temperature methanol is first exchanged with the outlet gas of the methanation reactor II through the inlet and outlet heat exchanger IV, and then through the inlet and outlet heat exchanger III and the outlet gas of the methanation reactor I. After 290°C, enter the methanation reactor I equipped with NiO 75wt%-La ₂ O ₃ 7wt%-Al ₂ O ₃ 15wt%-ZrO ₂ 3wt% catalyst from the top, at a pressure of 2.0MPa and a space velocity of 6000h ^-1 The first-stage methanation reaction is carried out under the conditions. The outlet gas with a temperature of 569°C first passes through the waste heat boiler III to recover heat, and after the heat exchange with the gas washed by low-temperature methanol through the inlet and outlet heat exchanger III reaches 270°C, it enters the device from the top. There are _NiO75wt % _-La2O37wt % _-Al2O315wt % _-ZrO23wt % in methanation reactor _II , under the conditions of pressure 2.0MPa and space velocity 6000h ^-1 , carry out secondary methanation reaction, since then The CO in the synthesis gas is completely converted into CH ₄ gas. The gas with a temperature of 309 ° C first passes through the inlet and outlet heat exchanger IV to exchange heat with the gas from the low-temperature methanol washing system, and then enters the gas after being cooled by the air cooler II and water cooler. Liquid separation tank II, the condensate is discharged from the bottom of the separation tank II, and the discharge from the top of the separation tank II is the natural gas product, which is sent to the natural gas pipeline after being dried and compressed.

See attached table 1 for the composition of raw material gas and natural gas product synthesized under reaction conditions in this embodiment.

Example 6

In this example, the catalysts used in sulfur-tolerant methanation reactor I and sulfur-tolerant methanation reactor II are the same, and their mass composition is MoO ₃ 23wt%-Co ₂ O ₃ +ZrO ₂ +CeO ₂ 7wt%/γ-Al ₂ O ₃ 70wt% catalyst, the active component MoO ₃ and the auxiliary agent Co ₂ O ₃ +ZrO ₂ +CeO ₂ are loaded on the carrier γ-Al ₂ O ₃ by co-precipitation, the specific preparation method and process are implemented in CN103480362A Example 2: Davy's CEG-LH catalyst was used as the nickel-based catalyst for methanation reactor I and methanation reactor II. Adopt above-mentioned catalyzer, its concrete technological process and condition are as follows:

(1) After dedusting and oil removal, the synthesis gas whose volume composition is H ₂ 40%, CO 19.3%, CO ₂ 30.4%, CH ₄ 10% and N ₂ 0.3% first passes through the inlet and outlet heat exchanger II and sulfur-resistant methanation The outlet gas of reactor II is heat-exchanged, and then passes through the inlet and outlet heat exchanger I and the outlet gas of sulfur-tolerant methanation reactor I is heat-exchanged to 295°C, and is mixed with water vapor and then enters sulfur-tolerant methanation reactor I from the top , the molar ratio of water vapor to synthesis gas is 0.20, under the reaction conditions of pressure 7.0MPa and space velocity 5500h ^-1 , the supported MoO ₃ 23wt%-Co ₂ O ₃ +ZrO ₂ +CeO ₂ 7wt%/γ- The first-stage sulfur-tolerant methanation and sulfur-tolerant shift reactions are carried out on the Al ₂ O ₃ 70wt% dual-function catalyst. The outlet gas with a temperature of 542°C passes through the high-pressure waste heat boiler I to recover heat, and passes through the inlet and outlet heat exchanger I and the raw gas After the heat exchange reaches 295°C, go to the sulfur-tolerant methanation reactor II;

(2) The reaction gas from sulfur-tolerant methanation reactor I enters sulfur-tolerant methanation reactor II from the top, under the reaction conditions _of pressure ^7.0MPa and space velocity 5500h ₂ O ₃ +ZrO ₂ +CeO ₂ 7wt%/γ-Al ₂ O ₃ 70wt% bifunctional catalyst for the second-stage sulfur-tolerant methanation and sulfur-tolerant shift reaction, the outlet gas at 481°C first passes through the high-pressure waste heat boiler II recovers heat, and then exchanges heat with the synthesis gas through the inlet and outlet heat exchanger II, and further cools through the air cooler I, and then enters the gas-liquid separation tank I for gas-liquid separation. The condensate is discharged from the bottom of the separation tank I, and the top of the separation tank The discharged gas phase enters the low-temperature methanol washing system, and the CO ₂ and H ₂ S are eluted by low-temperature methanol under the conditions of -55°C and 7.0Mpa, in which H ₂ S is removed to 0.01ppm, while CO ₂ is removed to volume Content 0.3V%, then sent to the methanation reactor I that nickel-based catalyst is housed;

(3) The gas washed from the low-temperature methanol is first exchanged with the outlet gas of the methanation reactor II through the inlet and outlet heat exchanger IV, and then through the inlet and outlet heat exchanger III and the outlet gas of the methanation reactor I. After 295°C, it enters the methanation reactor I equipped with a CEG-LH catalyst from the top, and performs a primary methanation reaction under the conditions of a pressure of 7.0MPa and a space velocity of 5500h ^-1 . Boiler III recovers heat, and after heat exchange with the gas washed by low-temperature methanol through inlet and outlet heat exchanger III to reach 260°C, it enters into CEG-LH methanation reactor II from the top, at a pressure of 7.0MPa and a space velocity of 5500h Under the condition of ^-1 , the secondary methanation reaction is carried out, since then the CO in the synthesis gas is completely converted into CH ₄ gas, and the gas with a temperature of 304°C first passes through the inlet and outlet heat exchanger IV to exchange heat with the gas from the low-temperature methanol washing system, After being cooled by the air cooler II and water cooler, it enters the gas-liquid separation tank II. The condensate is discharged from the bottom of the separation tank II, and the product discharged from the top of the separation tank II is the natural gas product, which is sent to the natural gas pipeline after being dried and compressed.

See attached table 1 for the composition of raw material gas and natural gas product synthesized under reaction conditions in this embodiment.

Example 7

In this example, the catalysts used in sulfur-tolerant methanation reactor I and sulfur-tolerant methanation reactor II are the same, and their mass composition is MoO ₃ 27wt%-Co ₂ O ₃ +La ₂ O ₃ 8wt%/magnesium aluminum spinel A catalyst of 65 wt% ore, the active component MoO ₃ and the auxiliary agent Co ₂ O ₃ +La ₂ O ₃ are loaded on the carrier magnesium aluminum spinel by impregnation, the specific preparation method and process are shown in Example 14 of CN103495421A; methanation reaction The nickel-based catalyst in reactor I and methanation reactor II adopts Davy's CEG-LH catalyst. Adopt above-mentioned catalyzer, its concrete technological process and condition are as follows:

(1) After dedusting and oil removal, the synthesis gas whose volume composition is H ₂ 40%, CO 20%, CO ₂ 28%, CH ₄ 11.6% and N ₂ 0.4% first passes through the inlet and outlet heat exchanger II and sulfur-resistant methanation The outlet gas of reactor II is heat-exchanged, and then passes through the inlet and outlet heat exchanger I and the outlet gas of sulfur-tolerant methanation reactor I is heat-exchanged to 300°C, and is mixed with water vapor and then enters sulfur-tolerant methanation reactor I from the top , the molar ratio of water vapor to synthesis gas is 0.20, under the reaction conditions of pressure 6.0MPa and space velocity 5000h ^-1 , the supported MoO ₃ 27wt%-Co ₂ O ₃ +La ₂ O ₃ 8wt%/MgAl tip The first-stage sulfur-tolerant methanation and sulfur-tolerant shift reactions are carried out on the spar 65wt% dual-function catalyst. The outlet gas with a temperature of 527°C passes through the high-pressure waste heat boiler I successively to recover heat, and then passes through the inlet and outlet heat exchanger I to exchange heat with the raw material gas After reaching 300°C, go to sulfur-tolerant methanation reactor II;

(2) The reaction gas from sulfur-tolerant methanation reactor I enters sulfur-tolerant methanation reactor II from the top, under the reaction conditions of pressure ^6.0MPa and space velocity _{5000h 2} O ₃ +La ₂ O ₃ 8wt%/magnesia-aluminum spinel 65wt% dual-function catalyst for the second-stage sulfur-tolerant methanation and sulfur-tolerant shift reaction, the outlet gas at 467°C is first recovered through the high-pressure waste heat boiler II The heat is then exchanged with the synthesis gas through the inlet and outlet heat exchanger II, and further cooled by the air cooler I, and then enters the gas-liquid separation tank I for gas-liquid separation. The condensate is discharged from the bottom of the separation tank I, and the condensate is discharged from the top of the separation tank The gas phase enters the low-temperature methanol washing system, and the CO ₂ and H ₂ S are eluted by low-temperature methanol under the conditions of -45°C and 6.0Mpa, in which H ₂ S is removed to 0.02ppm, while CO ₂ is removed to a volume content of 0.6 V%, then sent to the methanation reactor I that nickel-based catalyst is housed;

(3) The gas washed from the low-temperature methanol is first exchanged with the outlet gas of the methanation reactor II through the inlet and outlet heat exchanger IV, and then through the inlet and outlet heat exchanger III and the outlet gas of the methanation reactor I. After 300°C, it enters the methanation reactor I equipped with CEG-LH catalyst from the top, and performs primary methanation under the conditions of pressure ^6.0MPa and space velocity 5000h Boiler III recovers heat, and after heat exchange with the gas washed by low-temperature methanol through inlet and outlet heat exchanger III up to 260°C, it enters into CEG-LH methanation reactor II from the top, at a pressure of 6.0MPa and a space velocity of 5000h Under the condition of ^-1 , the secondary methanation reaction is carried out, since then the CO in the synthesis gas is completely converted into CH ₄ gas, and the gas at a temperature of 300 ° C first passes through the inlet and outlet heat exchanger IV to exchange heat with the gas from the low-temperature methanol washing system, After being cooled by the air cooler II and water cooler, it enters the gas-liquid separation tank II. The condensate is discharged from the bottom of the separation tank II, and the product discharged from the top of the separation tank II is the natural gas product, which is sent to the natural gas pipeline after being dried and compressed.

See attached table 1 for the composition of raw material gas and natural gas product synthesized under reaction conditions in this embodiment.

Example 8

In this example, the catalysts used in sulfur-tolerant methanation reactor I and sulfur-tolerant methanation reactor II are the same, and the mass composition of oxides is MoO ₃ 20wt%-Co ₂ O ₃ +Ce ₂ O ₃ 12wt%/γ -Al ₂ O ₃ 68wt% catalyst, the active component Mo ₂ O ₃ and additives Co ₂ O ₃ +Ce ₂ O ₃ are loaded on the carrier γ-Al ₂ O ₃ by means of sol-gel, the specific preparation method and For the process, see Example 4 of CN101733115A; the nickel-based catalyst in methanation reactor I and methanation reactor II adopts Topsoe's MCR-2X catalyst. Adopt above-mentioned catalyzer, its concrete technological process and condition are as follows:

(1) After dedusting and oil removal, the synthesis gas whose volume composition is H ₂ 38%, CO 19%, CO ₂ 32.1%, CH ₄ 10.5% and N ₂ 0.4% first passes through the inlet and outlet heat exchanger II and sulfur-resistant methanation The outlet gas of reactor II is heat-exchanged, and then through the inlet and outlet heat exchanger I and the outlet gas of sulfur-tolerant methanation reactor I, the heat exchange reaches 280°C, and it is mixed with water vapor and then enters sulfur-tolerant methanation reactor I from the top , the molar ratio of water vapor to synthesis gas is 0.20, under the reaction conditions of pressure 5.5MPa and space velocity 4000h ^-1 , the supported MoO ₃ 20wt%-Co ₂ O ₃ +Ce ₂ O ₃ 12wt%/γ-Al The ₂ O ₃ 68wt% dual-function catalyst is used for the first-stage sulfur-tolerant methanation and sulfur-tolerant shift reactions. The outlet gas with a temperature of 516°C passes through the high-pressure waste heat boiler I successively to recover heat, and passes through the inlet and outlet heat exchanger I to exchange with the raw material gas. After the heat reaches 280°C, go to the sulfur-tolerant methanation reactor II;

(2) The reaction gas from sulfur-tolerant methanation reactor I enters sulfur-tolerant methanation reactor II from the top, under the reaction conditions _of pressure ^5.5MPa and space velocity 4000h ₂ O ₃ +Ce ₂ O ₃ 12wt%/γ-Al ₂ O ₃ 68wt% bifunctional catalyst for the second-stage sulfur-tolerant methanation and sulfur-tolerant shift reaction, the outlet gas with a temperature of 461°C first passes through the high-pressure waste heat boiler II Recover heat, then exchange heat with the synthesis gas through the inlet and outlet heat exchanger II, and then enter the gas-liquid separation tank I for gas-liquid separation after further cooling through the air cooler I, the condensate is discharged from the bottom of the separation tank I, and the top of the separation tank The gas phase of the gas enters the low-temperature methanol washing system. After the CO ₂ and H ₂ S are eluted by low-temperature methanol under the conditions of -60°C and 5.0Mpa, the H ₂ S is removed to 0.01ppm, and the CO ₂ is removed to the volume content. 0.7V%, after being sent to the methanation reactor I that nickel-based catalyst is housed;

(3) The gas washed from the low-temperature methanol is first exchanged with the outlet gas of the methanation reactor II through the inlet and outlet heat exchanger IV, and then through the inlet and outlet heat exchanger III and the outlet gas of the methanation reactor I. After 280°C, it enters the methanation reactor I equipped with a CEG-LH catalyst from the top, and performs a primary methanation reaction under the conditions of a pressure of 5.5MPa and a space velocity of 4000h ^-1 , and the outlet gas with a temperature of 481°C first passes through the waste heat Boiler III recovers heat, and after heat exchange with the gas washed by low-temperature methanol through inlet and outlet heat exchanger III to 260°C, it enters into CEG-LH methanation reactor II from the top, at a pressure of 5.5MPa and a space velocity of 4000h Under the condition of ^-1 , the secondary methanation reaction is carried out. Since then, the CO in the synthesis gas is completely converted into CH ₄ gas. The gas with a temperature of 302 ° C first passes through the inlet and outlet heat exchanger IV to exchange heat with the gas from the low-temperature methanol washing system. After being cooled by the air cooler II and water cooler, it enters the gas-liquid separation tank II. The condensate is discharged from the bottom of the separation tank II, and the product discharged from the top of the separation tank II is the natural gas product, which is sent to the natural gas pipeline after being dried and compressed.

See attached table 1 for the composition of raw material gas and natural gas product synthesized under reaction conditions in this embodiment.

Example 9

In this example, the catalysts used in sulfur-tolerant methanation reactor I and sulfur-tolerant methanation reactor II are the same, and the mass composition of oxides is MoO ₃ 15wt%-Co ₂ O ₃ +La ₂ O ₃ 10wt%/magnesium Aluminum spinel 75wt% catalyst, active component MoO ₃ and auxiliary agent Co ₂ O ₃ +La ₂ O ₃ are supported on the carrier Al ₂ O ₃ -ZrO ₂ by means of sol-gel, the specific preparation method and process see Example 6 of CN101733115A; the nickel-based catalyst in methanation reactor I and methanation reactor II adopts Topsoe's MCR-2X catalyst. Adopt above-mentioned catalyzer, its concrete technological process and condition are as follows:

(1) After dedusting and oil removal, the synthesis gas whose volume composition is H ₂ 38%, CO 18.4%, CO ₂ 32%, CH ₄ 11.5% and N ₂ 0.1% first passes through the inlet and outlet heat exchanger II and sulfur-resistant methanation The outlet gas of reactor II is heat-exchanged, and then through the inlet and outlet heat exchanger I and the outlet gas of sulfur-tolerant methanation reactor I, the heat exchange reaches 280°C, and it is mixed with water vapor and then enters sulfur-tolerant methanation reactor I from the top , the molar ratio of water vapor to syngas is 0.20, under the reaction conditions of pressure 5.0MPa and space velocity 3000h ^-1 , the supported MoO ₃ 15wt%-Co ₂ O ₃ +La ₂ O ₃ 10wt%/MgAl tip The primary sulfur-tolerant methanation and sulfur-tolerant shift reactions are carried out on the spar 75wt% dual-function catalyst. The outlet gas with a temperature of 508°C passes through the high-pressure waste heat boiler I successively to recover heat, and then passes through the inlet and outlet heat exchanger I to exchange heat with the raw material gas After reaching 280°C, go to sulfur-tolerant methanation reactor II;

(2) The reaction gas from sulfur-tolerant methanation reactor I enters sulfur ^- tolerant methanation reactor II from the top, under the reaction conditions _of pressure 5.0MPa and space velocity 3000h ₂ O ₃ +La ₂ O ₃ 10wt%/magnesia-aluminum spinel 75wt% bifunctional catalyst for the second-stage sulfur-tolerant methanation and sulfur-tolerant shift reaction, the outlet gas at 455°C is first recovered through the high-pressure waste heat boiler II The heat is then exchanged with the synthesis gas through the inlet and outlet heat exchanger II, and further cooled by the air cooler I, and then enters the gas-liquid separation tank I for gas-liquid separation. The condensate is discharged from the bottom of the separation tank I, and the condensate is discharged from the top of the separation tank The gas phase enters the low-temperature methanol washing system, and the CO ₂ and H ₂ S are eluted by low-temperature methanol under the conditions of -20°C and 5.0Mpa, in which H ₂ S is removed to 0.1ppm, and CO ₂ is removed to a volume content of 0.8 V%, then sent to the methanation reactor I that nickel-based catalyst is housed;

(3) The gas washed from the low-temperature methanol is first exchanged with the outlet gas of the methanation reactor II through the inlet and outlet heat exchanger IV, and then through the inlet and outlet heat exchanger III and the outlet gas of the methanation reactor I. After 280°C, it enters the methanation reactor I equipped with MCR-2X catalyst from the top, and performs primary methanation reaction under the conditions of pressure 5.0MPa and space velocity ^3000h Boiler III recovers heat, and after heat exchange with the gas washed by low-temperature methanol through inlet and outlet heat exchanger III to reach 260°C, it enters into MCR-2X methanation reactor II from the top, at a pressure of 5.0MPa and a space velocity of 3000h The second-stage methanation reaction is carried out under the condition of ^-1 , since then the CO in the synthesis gas is completely converted into CH ₄ gas, and the gas at a temperature of 305°C first passes through the inlet and outlet heat exchanger IV to exchange heat with the gas from the low-temperature methanol washing system, After being cooled by the air cooler II and water cooler, it enters the gas-liquid separation tank II. The condensate is discharged from the bottom of the separation tank II, and the product discharged from the top of the separation tank II is the natural gas product, which is sent to the natural gas pipeline after being dried and compressed.

See attached table 1 for the composition of raw material gas and natural gas product synthesized under reaction conditions in this embodiment.

Example 10

In this example, the catalysts used in sulfur-tolerant methanation reactor I and sulfur-tolerant methanation reactor II are the same, and the mass composition of oxides is MoO ₃ 10wt%-Co ₂ O ₃ 5wt%/Al ₂ O ₃ -ZrO ₂ 85 wt% of the catalyst, the active component MoO ₃ and the auxiliary agent Co ₂ O ₃ are loaded on the carrier Al ₂ O ₃ -ZrO ₂ by co-precipitation, the specific preparation method and process are shown in Example 3 of CN101733115A; Methanation Reactor The nickel-based catalyst in I and methanation reactor II adopts Topsoe's MCR-2X catalyst. Adopt above-mentioned catalyzer, its concrete technological process and condition are as follows:

(1) After dedusting and oil removal, the synthesis gas whose volume composition is H ₂ 37.6%, CO 17.3%, CO ₂ 33%, CH ₄ 12% and N ₂ 0.1% first passes through the inlet and outlet heat exchanger II and sulfur-resistant methanation The outlet gas of reactor II is heat-exchanged, and then through the inlet and outlet heat exchanger I and the outlet gas of sulfur-tolerant methanation reactor I, the heat exchange reaches 280°C, and it is mixed with water vapor and then enters sulfur-tolerant methanation reactor I from the top , the molar ratio of water vapor to synthesis gas is 0.20, under the reaction conditions of pressure 4.5MPa and space velocity 2000h ^-1 , in the supported MoO ₃ 10wt%-Co ₂ O ₃ 5wt%/Al ₂ O ₃ -ZrO ₂ 85wt % The first-level sulfur-tolerant methanation and sulfur-tolerant shift reactions are carried out on the dual-function catalyst. The outlet gas with a temperature of 500°C passes through the high-pressure waste heat boiler I successively to recover heat, and then exchanges heat with the raw material gas through the inlet and outlet heat exchanger I to reach 280°C After that, go to the sulfur-tolerant methanation reactor II;

(2) The reaction gas from sulfur-tolerant methanation reactor I enters sulfur ^- tolerant methanation reactor II from the top, under the reaction conditions _of pressure 4.5MPa and space velocity 2000h ₂ O ₃ 5wt%/Al ₂ O ₃ -ZrO ₂ 85wt% bifunctional catalyst for the second-stage sulfur-tolerant methanation and sulfur-tolerant shift reaction, the outlet gas at 450°C first passes through the high-pressure waste heat boiler II to recover heat, and then It exchanges heat with the synthesis gas through the inlet and outlet heat exchanger II, and is further cooled by the air cooler I before entering the gas-liquid separation tank I for gas-liquid separation. The condensate is discharged from the bottom of the separation tank I, and the gas phase discharged from the top of the separation tank enters the low temperature Methanol washing system, after CO ₂ and H ₂ S are eluted by low-temperature methanol under the conditions of -30°C and 2.0Mpa, H ₂ S is removed to 0.9ppm, while CO ₂ is removed to a volume content of 0.7V%, Then send to the methanation reactor I that nickel-based catalyst is housed;

(3) The gas washed from the low-temperature methanol is first exchanged with the outlet gas of the methanation reactor II through the inlet and outlet heat exchanger IV, and then through the inlet and outlet heat exchanger III and the outlet gas of the methanation reactor I. After 280°C, it enters the methanation reactor I equipped with MCR-2X catalyst from the top, and performs primary methanation reaction under the conditions of pressure ^2.0MPa and space velocity 2000h Boiler III recovers heat, and after heat exchange with the gas washed by low-temperature methanol through inlet and outlet heat exchanger III to 260°C, it enters into MCR-2X methanation reactor II from the top, at a pressure of 2.0MPa and a space velocity of 3000h Under the condition of ^-1 , the secondary methanation reaction is carried out, since then the CO in the synthesis gas is completely converted into CH ₄ gas, and the gas at a temperature of 300 ° C first passes through the inlet and outlet heat exchanger IV to exchange heat with the gas from the low-temperature methanol washing system, After being cooled by the air cooler II and water cooler, it enters the gas-liquid separation tank II. The condensate is discharged from the bottom of the separation tank II, and the product discharged from the top of the separation tank II is the natural gas product, which is sent to the natural gas pipeline after being dried and compressed.

See attached table 1 for the composition of raw material gas and natural gas product synthesized under reaction conditions in this embodiment.

Schedule 1

Claims (14)

1. A process for preparing natural gas by sulfur-resistant methanation of coal-based synthesis gas, characterized in that it comprises the steps: (1) The synthetic gas after dedusting and oil removal first passes through the inlet and outlet heat exchanger II to exchange heat with the outlet gas of the sulfur-tolerant methanation reactor II, and then passes through the inlet and outlet heat exchanger I and the sulfur-tolerant methanation reactor I to exit After heat exchange, the gas is mixed with steam and then enters the sulfur-tolerant methanation reactor I from the top, and the first-stage sulfur-tolerant methanation and sulfur-tolerant shift reaction are carried out on the molybdenum-based bifunctional catalyst, and the outlet gas first passes through the high-pressure waste heat boiler I recover heat, and after exchanging heat with the synthesis gas through the inlet and outlet heat exchanger I, go to the sulfur-resistant methanation reactor II; (2) The reaction gas from the sulfur-tolerant methanation reactor I enters the sulfur-tolerant methanation reactor II from the top, and the second-stage sulfur-tolerant methanation and sulfur-tolerant shift reaction are carried out on the molybdenum-based bifunctional catalyst. The heat is recovered through the high-pressure waste heat boiler II, and then heat exchanged with the synthesis gas through the inlet and outlet heat exchanger II, and further cooled by the air cooler I, and then enters the gas-liquid separation tank I for gas-liquid separation, and the condensate is discharged from the bottom of the separation tank I , and the gas phase enters the low-temperature methanol washing system after being discharged from the top of the separation tank, and after the carbon dioxide and hydrogen in the gas are removed by low-temperature methanol washing, it is sent to the methanation reactor 1 where the Ni-based catalyst is housed; (3) The gas washed from low-temperature methanol first exchanges heat with the outlet gas of the methanation reactor II through the inlet and outlet heat exchanger IV, and then exchanges heat with the outlet gas of the methanation reactor I through the inlet and outlet heat exchanger III , enters the methanation reactor I from the top, and carries out the first-stage methanation reaction under the catalysis of the Ni-based methanation catalyst. After heat exchange, the incoming gas enters the methanation reactor II from the top, and carries out the second-stage methanation reaction under the action of the Ni-based methanation catalyst. Since then, the CO in the synthesis gas is completely converted into _CH4 gas, and the methanation The outlet gas of the reactor II first passes through the inlet and outlet heat exchanger IV to exchange heat with the gas from the low-temperature methanol washing system, then after being cooled by the air cooling II and the water cooler, it enters the gas-liquid separation tank II for gas-liquid separation, and the condensate is self-separated The bottom of the tank II is discharged, and the natural gas product is discharged from the top of the separation tank II, which is sent to the natural gas pipeline after being dried and compressed; The synthesis gas is produced by Lurgi crushed coal pressurized gasification technology, and its composition is H ₂ 37-40%, CO 17-20%, CO ₂ 28-33%, CH ₄ 8%-12 %, N ₂ 0.1-0.4%. 2. A process for producing natural gas by sulfur-resistant methanation of coal-based syngas as claimed in claim 1, characterized in that the mass composition of the molybdenum-based bifunctional catalyst is: active component MoO ₃ 10-35wt%, Auxiliary oxide 2-20wt%, carrier 50-85wt%; the auxiliary agent is one or more of Co, La, Ce, Zr, Fe, Ni and K, and the carrier is γ-Al ₂ O ₃ , SiO _2. Magnesium aluminum spinel, ZrO ₂ , CeO ₂ -Al ₂ O ₃ composite carrier or Al ₂ O ₃ -ZrO ₂ composite carrier. 3. A process for producing natural gas by sulfur-resistant methanation of coal-to-synthesis gas as claimed in claim 2, characterized in that said auxiliary agent is Co, La, Ce or Zr. 4. A process for preparing natural gas by sulfur-resistant methanation of coal-based syngas as claimed in claim 2, characterized in that the carrier is magnesium aluminum spinel, CeO ₂ -Al ₂ O ₃ composite carrier or Al ₂ O ₃ -ZrO ₂ composite support. 5. A process for producing natural gas by sulfur-resistant methanation of coal-to-synthesis gas as claimed in claim 1, characterized in that both the sulfur-resistant methanation reactor I and the sulfur-resistant methanation reactor II are fixed beds Adiabatic reactor. 6. A kind of coal-to-synthesis gas as claimed in claim 1 carries out the technique of sulfur-resistant methanation to prepare natural gas, it is characterized in that the volume ratio of water vapor and synthesis gas in the inlet of described sulfur-resistant methanation reactor I is 0.1 ~0.3, the inlet gas temperature after mixing is 270~300°C, the outlet gas temperature is 500~600°C, the reaction pressure is 2.0~7.0MPa, and the reaction space velocity is 2000~8000h ^-1 . 7. A process for producing natural gas by sulfur-resistant methanation of coal-based synthesis gas as claimed in claim 1, characterized in that the inlet gas temperature of the sulfur-resistant methanation reactor II is 270-300°C, and the outlet gas temperature is The temperature is 450~550℃, the reaction pressure is 2.0~7.0MPa, and the reaction space velocity is 2000~8000h ^-1 . 8. A process for preparing natural gas by sulfur-resistant methanation of coal-to-synthesis gas as claimed in claim 1, characterized in that the low-temperature methanol washing is composed of a desulfurization tower and a decarbonization tower, and the operating temperature is -20 to - 60°C, operating pressure 2.0-7.0MPa. 9. A process for preparing natural gas by sulfur-resistant methanation of coal-based syngas as claimed in claim 1, characterized in that the sulfur in the gas is removed to 0.01-0.1ppm after being washed with low-temperature methanol, and the volume of _CO2 Content off to 0.3 ~ 0.8V%. 10. A kind of coal-to-synthesis gas as claimed in claim 1 carries out the process of sulfur-resistant methanation to prepare natural gas, it is characterized in that the Ni-based catalyst used in the described methanation reactor I or methanation reactor II is Topsoe's MCR-2X methanation catalyst, Davy's CEG-LH methanation catalyst or catalyst is based on the mass composition of oxides: active component NiO 10-75%, additive La ₂ O ₃ 0.1-15% and the balance of carrier Al ₂ O ₃ -ZrO ₂ , the auxiliary agent is a combination of lanthanum oxide or lanthanum oxide and nickel-lanthanum compound, and the carrier is a combination of aluminum oxide, nickel-aluminum compound and zirconia. 11. A process for producing natural gas by sulfur-resistant methanation of coal-to-synthesis gas according to claim 1, characterized in that both the methanation reactor I and the methanation reactor II are fixed-bed adiabatic reactors. 12. A process for preparing natural gas by sulfur-resistant methanation of coal-based synthesis gas as claimed in claim 1, characterized in that the inlet gas temperature of the methanation reactor I is 270-300° C., and the outlet gas temperature is 450-620° C. °C, the reaction pressure is 2.0-7.0MPa, and the reaction space velocity is 2000-8000h ^-1 . 13. A process for preparing natural gas by sulfur-resistant methanation of coal-to-synthesis gas as claimed in claim 1, characterized in that the inlet gas temperature of the methanation reactor II is 250-300°C, and the outlet gas temperature is 290-350°C °C, the reaction pressure is 2.0-7.0MPa, and the reaction space velocity is 2000-8000h ^-1 . 14. A process for preparing natural gas by sulfur-resistant methanation of coal-based synthesis gas according to any one of claims 1-13, characterized in that the volume composition of the natural gas after the synthesis gas undergoes the above-mentioned process and reaction is : CH ₄ 96-98%, CO ₂ 0.2-0.5, H ₂ 0.5-2%, N ₂ 0.6-1.2%, C _2-6 0.3-0.5%.