Non-sulfur-tolerant wide-temperature shift regulation and control process based on coal-based natural gas methanation process

Abstract

The invention relates to a non-sulfur-tolerant wide-temperature shift regulation and control process based on a coal natural gas methanation process, and belongs to the technical field of coal chemical industry. The process comprises the following specific steps: carrying out non-sulfur-tolerant wide-temperature shift reaction on purified raw materials for methanation reaction, namely carrying out adiabatic and / or isothermal CO shift reaction under the conditions that the temperature is 200-360 DEG C, the pressure is 1-10 MPa, the molar ratio of H2O to CO is 0.7-2 and the air speed is 3000-40000h <-1 >, reducing the CO concentration at the inlet of a methanation reactor by 30-70%, and then carrying out high-temperature reaction on the methanation reaction to obtain the high-sulfur-tolerant methanation reaction. The CO disproportionation reaction in the methanation reactor is avoided while the circulating gas is effectively reduced, the service life of the existing methanation catalyst is prolonged by more than 50%, and the shutdown frequency and the maintenance time are greatly reduced.

Description

[0001] TECHNICAL FIELD The present application belongs to the technical field of coal chemical industry, and particularly relates to a non-sulfur-tolerant wide-temperature shift regulation process based on a coal-to-natural gas methanation process.

[0002] BACKGROUND With the increasing demand for environmental protection, natural gas as a clean energy is attracting much attention. However, the proportion of primary energy consumption in China is far lower than the world average. China is rich in coal resources, and coal-to-natural gas is one of the methods for clean and efficient utilization of coal. Therefore, coal-to-natural gas can optimize the energy structure in China and effectively solve the dual problems of energy supply security and ecological environment protection.

[0003] The production process of coal-to-natural gas mainly includes coal gasification, sulfur-tolerant shift, purification, methanation, and drying and dehydration. In the methanation process of coal-to-natural gas, carbon deposition caused by CO disproportionation reaction (Boudouard reaction: 2CO → C + CO2) and catalyst deactivation due to carbon deposition are key problems affecting the stability of the process and the service life of the methanation catalyst.

[0004] At present, the methanation process is mainly achieved by connecting multiple fixed-bed methanation reactors in series and parallel, and diluting the CO concentration in the raw gas by using circulating gas (such as circulating gas and raw gas molar ratio of (0.5-2):1) to control the temperature rise of the methanation reaction. In this process, in order to efficiently recover the large amount of heat released by the methanation reaction, the outlet temperature of the main methanation reactor is usually 550-675℃, so the CO content at the inlet of the methanation reactor is still high, and the risk of CO disproportionation and carbon deposition is great, which easily causes the deactivation of the methanation catalyst due to carbon deposition and the shutdown of the catalyst bed due to the rapid increase of the bed resistance. SUMMARY

[0005] The present application mainly aims at the problems of excessive carbon deposition caused by CO disproportionation, catalyst pulverization, large bed resistance, and short service life of the main methanation catalyst in the coal-to-natural gas main methanation reactor, and provides a non-sulfur-tolerant wide-temperature shift regulation process based on a coal-to-natural gas methanation process. In this process, by optimizing the inlet temperature of the reactor and the steam content, CO is effectively converted into CO2, the occurrence of CO disproportionation reaction is avoided, and the service life of the methanation catalyst and the annual operation time of the methanation device are effectively increased.

[0006] In order to achieve the purpose of the present application, the technical solutions adopted are as follows: A non-sulfur-tolerant wide-temperature shift regulation process based on a coal-to-natural gas methanation process, which heats the methanation raw gas to a certain temperature and then enters a wide-temperature shift reactor, and under certain conditions, carries out adiabatic and / or isothermal CO shift reaction to reduce the CO content in the synthesis gas, and then heats or does not heat and sends to the methanation reactor.

[0007] Further, in the non-sulfur-tolerant wide-temperature-shift regulation process based on the coal-to-natural gas methanation process, the methanation raw gas is a mixed gas of synthesis gas and recycled gas and steam, or a mixed gas of synthesis gas and recycled gas or steam; each substance in the methanation raw gas is heated to a certain temperature by separate heating or mixed heating and then enters the wide-temperature-shift reactor.

[0008] Further, in the non-sulfur-tolerant wide-temperature-shift regulation process based on the coal-to-natural gas methanation process, the molar ratio of H2O to CO in the methanation raw gas is 0.7-2 (specifically, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, etc.).

[0009] Further, in the non-sulfur-tolerant wide-temperature-shift regulation process based on the coal-to-natural gas methanation process, the reaction space velocity for the adiabatic and / or isothermal CO shift reaction is 3000-40000 h -1 -1, the temperature is 200-360℃ (specifically, 200℃, 220℃, 240℃, 260℃, 280℃, 300℃, 320℃, 340℃, 360℃, etc.), and the pressure is 1-10 MPa (specifically, 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa, etc.).

[0010] Further, in the non-sulfur-tolerant wide-temperature-shift regulation process based on the coal-to-natural gas methanation process, the total sulfur content in the methanation raw gas is less than 0.1 ppm; more preferably, the total sulfur content in the methanation raw gas is less than 0.02 ppm.

[0011] Further, in the non-sulfur-tolerant wide-temperature-shift regulation process based on the coal-to-natural gas methanation process, the wide-temperature-shift reactor is an adiabatic reactor or an isothermal reactor.

[0012] Further, in the non-sulfur-tolerant wide-temperature-shift regulation process based on the coal-to-natural gas methanation process, the shape of the catalyst used in the wide-temperature-shift reactor is cylindrical, strip-shaped or porous cylindrical.

[0013] Further, in the non-sulfur-tolerant wide-temperature-shift regulation process based on the coal-to-natural gas methanation process, the isothermal reactor uses steam to remove the heat generated by the shift reaction.

[0014] Further, in the non-sulfur-tolerant wide-temperature shift regulation process based on the coal-to-natural gas methanation process, the active component of the catalyst used in the wide-temperature shift reactor is mainly copper oxide; more preferably, the wide-temperature shift catalyst of Southwest Research and Design Institute of Chemical Industry Co., Ltd.

[0015] Compared with the prior art, the main advantages of the present application are as follows: (1) By the process, the CO concentration at the inlet of the methanation reactor is effectively controlled, the CO concentration at the inlet of the methanation reactor is reduced by 30% to 70%, the circulating gas is effectively reduced, the CO disproportionation reaction in the methanation reactor is avoided, the service life of the existing methanation catalyst is prolonged by more than 50%, and the number of shutdowns and maintenance time are greatly reduced.

[0016] (2) Since the wide-temperature shift reactor requires a lower inlet temperature, the area of the heat exchanger can be reduced and a lower grade heat source can be used, reducing investment and improving energy utilization.

[0017] (3) The reduction of the inlet temperature of the wide-temperature shift reactor allows a larger adiabatic temperature rise, so the gas amount of the circulating gas can be reduced by about 23%, and the power consumption of the circulating compression is saved. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The present application is a non-sulfur-tolerant wide-temperature shift regulation process based on the coal-to-natural gas methanation process. DETAILED DESCRIPTION

[0019] The non-sulfur-tolerant wide-temperature shift regulation process based on the coal-to-natural gas methanation process includes the following process (for details, see Figure 1 ) is: after the desulfurization and purification of the synthesis gas, the synthesis gas is heated to 200-260℃ with the circulating gas and / or steam, the molar ratio of H2O and CO in the methanation raw gas after mixing of the synthesis gas with the circulating gas and / or steam is controlled to be 0.7-2, then the raw gas enters the wide-temperature shift reactor for CO wide-temperature shift reaction, the outlet temperature is raised to 280-360℃, and then enters the methanation reactor.

[0020] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application will be further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0021] In this application, all unmarked values represent molar percentage.

[0022] In the present application, some conventional operating equipment, devices and components are omitted or only described simply.

[0023] In the following examples, the wide temperature shift reactor used is an adiabatic reactor or an isothermal reactor, in which the shape of the catalyst is cylindrical, strip-shaped or porous cylindrical. The active component is mainly copper oxide. When the wide temperature shift reactor is an isothermal reactor, steam is used to remove the heat generated by the shift reaction.

[0024] Example 1 After the coal is crushed and pressurized, the hydrogen-carbon ratio is adjusted by sulfur-tolerant shift conversion, and the low-temperature methanol washing purification is performed, the required synthesis gas is obtained, the flow rate is 10000 kmol / h, the pressure is 3.3 MPa, and the total sulfur is less than 0.02 ppm, and the composition is shown in Table 1. The mixed gas after pressurization and heat exchange by the circulating compressor is used as the circulating gas, and the molar ratio of H2O and CO in the mixed gas after the synthesis gas and the circulating gas are mixed is controlled to be 1.242:1, then the flow rate of the circulating gas is 12057 kmol / h, and the composition is shown in Table 1; and the circulating gas outlet pressure is controlled to be 3.3 MPa by the circulating compressor. Then the synthesis gas and the circulating gas are heated to 245℃ and used as the raw material gas for the wide temperature shift reaction. The raw material gas enters the wide temperature shift reactor to perform the CO wide temperature shift reaction, the outlet temperature is increased to 312℃, the CO wet basis content in the synthesis gas is reduced to 2.64%, and then it is directly sent to the methanation reactor for further methanation reaction, and the specific process flow is shown in Figure 1 .

[0025] The wide temperature shift reactor used in this process is an adiabatic reactor, and the active component of the catalyst loaded is mainly copper oxide, such as the wide temperature shift catalyst of Southwest Chemical Research and Design Institute Co., Ltd. (CN202010430306.6).

[0026] Table 1 Composition of synthesis gas and circulating gas (wet basis, %)

[0027] Example 2 The coal is subjected to pressurized gasification, sulfur-tolerant shift conversion, and low-temperature methanol wash purification to obtain a synthesis gas with a flow rate of 10000 kmol / h, a pressure of 3.3 MPa, and a total sulfur content of less than 0.02 ppm, and the composition of the synthesis gas is shown in Table 2. The mixed gas after pressurization and heat exchange is used as the recycle gas, and the molar ratio of H2O to CO in the mixed gas is controlled to be 1.226:1, and the flow rate of the recycle gas is 11846 kmol / h, and the composition of the recycle gas is shown in Table 2. The outlet pressure of the recycle gas is controlled to be 3.3 MPa by using a recycle compressor. Then, the synthesis gas and the recycle gas are heated to 210°C to serve as the raw material gas for the wide-temperature shift reaction. The raw material gas enters the wide-temperature shift reactor to perform the CO wide-temperature shift reaction, and the outlet temperature is increased to 284°C, and the wet basis CO content in the synthesis gas is reduced to 2.17%. Then, the raw material gas is heated to 320°C and sent to the methanation reactor to continue the methanation reaction, and the specific process flow is shown in Figure 1 .

[0028] The wide-temperature shift reactor used in the process is an adiabatic reactor, and the active component of the catalyst loaded therein is mainly copper oxide, such as the wide-temperature shift catalyst (CN202010430306.6) of Southwest Chemical Research and Design Institute Co., Ltd.

[0029] Table 2 Composition of synthesis gas and recycle gas (wet basis, %)

[0030] Example 3 The coal is subjected to pressurized gasification, sulfur-tolerant shift conversion, and low-temperature methanol wash purification to obtain a synthesis gas with a flow rate of 10000 kmol / h, a pressure of 7.5 MPa, and a total sulfur content of less than 0.02 ppm, and the composition of the synthesis gas is shown in Table 3. The mixed gas after pressurization and heat exchange is used as the recycle gas, and the molar ratio of H2O to CO in the mixed gas is controlled to be 2.464:1, and the flow rate of the recycle gas is 18400 kmol / h, and the composition of the recycle gas is shown in Table 3. The outlet pressure of the recycle gas is controlled to be 7.5 MPa by using a recycle compressor. Then, the synthesis gas and the recycle gas are heated to 230°C to serve as the raw material gas for the wide-temperature shift reaction. The raw material gas enters the wide-temperature shift reactor to perform the CO wide-temperature shift reaction, and the outlet temperature is increased to 316°C, and the wet basis CO content in the synthesis gas is reduced to 1.16%. Then, the raw material gas is directly sent to the methanation reactor to continue the methanation reaction, and the specific process flow is shown in Figure 1 .

[0031] The wide-temperature shift reactor used in the process is an adiabatic reactor, and the active component of the catalyst loaded therein is mainly copper oxide, such as the wide-temperature shift catalyst (CN202010430306.6) of Southwest Chemical Research and Design Institute Co., Ltd.

[0032] Table 3 Composition of synthesis gas and recycle gas (wet basis, %)

[0033] Example 4 After the pulverized coal pressurized gasification, sulfur-tolerant shift adjustment of hydrogen-carbon ratio and low-temperature methanol wash purification, the required synthesis gas is obtained, with a flow rate of 10000 kmol / h, a pressure of 3.8 MPa and a total sulfur of less than 0.02 ppm, and its composition is shown in Table 4. The mixed gas after pressurization methanation and heat exchange by the recycle compressor is used as the recycle gas, the molar ratio of H2O and CO in the gas after mixing of the synthesis gas and the recycle gas is controlled to be 1.999:1, then the flow rate of the recycle gas is 17681 kmol / h, and its composition is shown in Table 4; and the outlet pressure of the recycle gas is controlled to be 3.8 MPa by the recycle compressor. Then the synthesis gas and the recycle gas are heated to 260℃ as the raw material gas for the wide-temperature shift reaction. The raw material gas enters the wide-temperature shift reactor to perform the CO wide-temperature shift reaction, the outlet temperature is increased to 342℃, the CO content in the synthesis gas is reduced to 2.11% (wet basis), and then it is directly sent to the methanation reactor for further methanation reaction. The specific process flow is shown in Figure 1 .

[0034] The wide-temperature shift reactor used in this process is an adiabatic reactor, and the active component of the catalyst loaded therein is mainly copper oxide, such as the wide-temperature shift catalyst of Southwest Chemical Research and Design Institute Co., Ltd. (CN202010430306.6).

[0035] Table 4 Composition of synthesis gas and recycle gas (wet basis, %)

[0036] Example 5 After the pulverized coal pressurized gasification, sulfur-tolerant shift adjustment of hydrogen-carbon ratio and low-temperature methanol wash purification, the required synthesis gas is obtained, with a flow rate of 10000 kmol / h, a pressure of 3.8 MPa and a total sulfur of less than 0.02 ppm, and its composition is shown in Table 4. The mixed gas after pressurization methanation and heat exchange by the recycle compressor is used as the recycle gas, the molar ratio of H2O and CO in the gas after mixing of the synthesis gas and the recycle gas is controlled to be 1.999:1, then the flow rate of the recycle gas is 17681 kmol / h, and its composition is shown in Table 4; and the outlet pressure of the recycle gas is controlled to be 3.8 MPa by the recycle compressor. Then the synthesis gas and the recycle gas are heated to 260℃ as the raw material gas for the wide-temperature shift reaction. The raw material gas enters the wide-temperature shift reactor to perform the CO wide-temperature shift reaction, the outlet temperature is increased to 342℃, the CO content in the synthesis gas is reduced to 2.11% (wet basis), and then it is directly sent to the methanation reactor for further methanation reaction. The specific process flow is shown in Figure 1 .

[0037] The wide-temperature shift reactor used in the process is an adiabatic reactor, and the active component of the loaded catalyst is mainly copper oxide, such as the wide-temperature shift catalyst of Southwest Chemical Research and Design Institute Co., Ltd. (CN202010430306.6).

[0038] Table 5 Composition of synthesis gas and recycle gas (wet basis, %)

[0039] The above examples only express the specific implementation of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the protection scope of the present application. It should be pointed out that for ordinary skilled persons in the art, without departing from the technical concept of the present application, a number of modifications and improvements can be made, which are within the protection scope of the present application.

[0040] This background section is provided to generally present the context of the application, the work of the current named inventors, the work described in this background section to the extent that it is described, and this section is neither expressly nor impliedly admitted to be prior art of the present application.

Claims

1. A non-sulfur-tolerant wide temperature shift regulation process based on coal-to-synthetic natural gas methanation process, characterized in that: The methanation raw gas is heated to a certain temperature and then enters the wide-temperature shift reactor, and the adiabatic and / or isothermal CO shift reaction is carried out under certain conditions to reduce the CO content in the synthesis gas, and then the synthesis gas is heated or not heated and sent to the methanation reactor.

2. The non-sulfur tolerant wide temperature shift process for coal to natural gas methanation process according to claim 1, characterized in that: The methanation raw gas is a mixture of synthesis gas, recycle gas and steam, or a mixture of synthesis gas, recycle gas or steam; and each substance in the methanation raw gas is heated to a certain temperature by separate heating or mixed heating and then enters the wide-temperature shift reactor.

3. The non-sulfur tolerant wide temperature shift process for coal to natural gas methanation process according to claim 1, characterized in that: The molar ratio of H2O to CO in the methanation raw gas is 0.7-2.

4. The non-sulfur tolerant wide temperature shift process for coal to natural gas methanation process according to claim 1, characterized in that: The reaction space velocity of the adiabatic and / or isothermal CO shift reaction is 3000-40000 h -1 , the temperature is 200-360℃, and the pressure is 1-10 MPa.

5. The non-sulfur tolerant wide temperature shift process for coal to natural gas methanation process according to claim 1, characterized in that: The wide-temperature shift reactor is an adiabatic reactor or an isothermal reactor.

6. The non-sulfur tolerant wide temperature shift process for coal to natural gas methanation process according to claim 5, characterized in that: The total sulfur content in the methanation raw gas is less than 0.02 ppm.

7. The non-sulfur tolerant wide temperature shift process for coal to natural gas methanation process according to claim 6, characterized in that: The shape of the catalyst used in the wide-temperature shift reactor is cylindrical, strip-shaped or porous cylindrical.

8. The non-sulfur tolerant wide temperature shift process for coal to natural gas methanation process according to claim 6, characterized in that: The isothermal reactor uses steam to remove the heat generated by the shift reaction.

9. The non-sulfur tolerant wide temperature shift process for coal to natural gas methanation process according to claim 7, characterized in that: The active component of the catalyst used in the wide-temperature shift reactor is mainly copper oxide.

10. The non-sulfur tolerant wide temperature shift process for coal to natural gas methanation process according to claim 9, characterized in that: The catalyst used in the wide-temperature shift reactor is the wide-temperature shift catalyst of Southwest Research and Design Institute of Chemical Industry Co., Ltd.

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