HPCO methanation treatment system and system isolation operation process

Abstract

The invention belongs to the field of chemical engineering, and particularly relates to an HPCO methanation treatment system and a system isolation operation technology, the HPCO methanation treatment system comprises a raw material supply unit, a first methanation reaction unit, a second methanation reaction unit, a heat recovery unit and a load isolation unit; according to the invention, the load isolation unit is matched with the first methanation reaction unit and the second methanation reaction unit, the second methanation reaction unit is isolated from the system when being overhauled, and the raw material supply unit, the first methanation reaction unit and the heat recovery unit in the system still continue to work at the moment, so that the overall shutdown of the HPCO methanation treatment system is avoided; in an isolated operation process based on the system, heat of a reaction product of the first methanation reaction unit is effectively exchanged by regulating and controlling the second inlet regulating valve, the first bypass valve, the second bypass valve and the sixth control valve, and the problem that heat is unbalanced during independent operation of the first methanation reaction unit is effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of chemical engineering, specifically relating to an HPCO methanation treatment system and a system isolation operation process. Background Technology

[0002] In the design of the methanation process, the methane synthesis reactor is set up as a multi-stage mass methanation reactor and a multi-stage supplementary methanation reactor. This is to increase the reaction rate by using the high reactant concentration and high reaction temperature of mass methanation, and to reduce the reaction temperature and increase the product concentration by using the multi-stage supplementary methanation reaction, thereby improving the methane synthesis efficiency and the quality of the methane synthesis product.

[0003] However, in the actual operation of the methanation unit, the first and second batch methanation reactors operate in series and parallel. Due to the inherent differences between the first and second batch methanation reactors, the second batch methanation reactor is generally more prone to overheating during operation. Therefore, it is necessary to regularly overhaul the second batch methanation reactor. However, when overhauling the second batch methanation reactor, the entire methanation unit must be shut down for a long period of time, resulting in a reduction in the effective operating time of the unit and seriously affecting the economic benefits of the enterprise. Therefore, how to achieve long-term continuous operation of the methanation unit is a major challenge currently facing coal chemical enterprises. Summary of the Invention

[0004] Therefore, the purpose of this invention is to provide an HPCO methanation system that separates the first methanation reaction unit and the second methanation reaction unit in parallel, and uses a blind plate to isolate the second methanation reaction unit while ensuring the continued operation of the HPCO methanation system.

[0005] Furthermore, another objective of this invention is to provide an isolated operation process for an HPCO methanation system. Based on the isolation of the second methanation reaction unit in the HPCO methanation system using a blind flange, the process involves controlling the second inlet regulating valve, the second bypass valve of the first bypass valve on the first methanation waste boiler and the steam superheater to close, and the sixth control valve to open, thereby enabling effective heat exchange of the reaction products of the first methanation reaction unit and effectively solving the problem of heat imbalance during the independent operation of the first methanation reaction unit.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] An HPCO methanation treatment system, comprising:

[0008] The raw material supply unit includes a desulfurization tank. The input end of the desulfurization tank is connected to a low-temperature methanol washing device via an external pipeline for introducing purified gas provided by the low-temperature methanol washing device into the desulfurization tank. The desulfurization tank performs fine desulfurization on the purified gas to generate raw material gas. The output end of the desulfurization tank is also provided with a first pipeline for exporting the raw material gas generated by fine desulfurization.

[0009] The first methanation reaction unit includes two first methanation reactors arranged in parallel. The input end of the first methanation reactor is connected to the first pipeline through a second pipeline for feeding the feed gas into the first methanation reactor to carry out the methanation reaction and obtain the first process gas. On this basis, the output end of the first methanation reactor is provided with a third pipeline for discharging the first process gas out of the first methanation reactor.

[0010] The second methanation reaction unit includes two second methanation reactors arranged in parallel. The input end of the second methanation reactor is connected to the first pipeline through a fourth pipeline for feeding the feed gas into the second methanation reactor and performing the methanation reaction to obtain the second process gas. On this basis, the output end of the second methanation reactor is provided with a fifth pipeline for discharging the second process gas out of the second methanation reactor.

[0011] The heat recovery unit includes a first methanation waste boiler, a second methanation waste boiler, a steam superheater, and a steam drum, wherein:

[0012] The input end of the first methanation waste pot is connected to the third pipeline, through which the first process gas is introduced to the first methanation waste pot for preliminary heat exchange and to generate the first saturated steam. The output end of the first methanation waste pot is provided with a sixth pipeline and a seventh pipeline. The sixth pipeline is connected to a steam superheater, through which the first process gas after preliminary heat exchange is introduced to the steam superheater for further heat exchange. The seventh pipeline is connected to a steam drum, through which the first saturated steam is introduced to the steam drum for further heat exchange to generate recovered steam.

[0013] The input end of the second methanation waste pot is connected to the fifth pipeline, through which the second process gas is introduced to the second methanation waste pot for preliminary heat exchange and to generate the second saturated steam. The output end of the second methanation waste pot is provided with an eighth pipeline and a ninth pipeline. The eighth pipeline is used to discharge the second process gas after preliminary heat exchange to the circulating heat exchange unit. The ninth pipeline is connected to the steam drum and is used to introduce the second saturated steam into the steam drum for further heat exchange to generate recovered steam.

[0014] The steam superheater is connected to the output end of the steam drum via an input pipeline. It is used to introduce the recovered steam from the steam drum into the steam superheater and use the recovered steam to further exchange heat with the first process gas. On this basis, the output end of the steam superheater is provided with a first output pipeline and a second output pipeline. The first output pipeline is connected to a steam utilization device to input the recovered steam after heat exchange into the steam utilization device for utilization. The second output pipeline is a three-way pipeline, one branch of which is connected to a fourth pipeline and the other branch is connected to a circulating heat exchange unit. The first process gas after heat exchange is partially introduced into the fourth pipeline as the first circulating gas through the second output pipeline, and the other part directly enters the circulating heat exchange unit.

[0015] The circulating heat exchange unit includes a circulating heat exchanger. The input end of the circulating heat exchanger is connected to the second output pipeline and the eighth pipeline through a three-way connector. The first process gas and the second process gas are mixed to form a mixed process gas, which then enters the circulating heat exchanger for circulating heat exchange. The mixed process gas after heat exchange is divided into two parts. One part is introduced into the supplementary methanation reaction unit through the first flow pipeline located at the output end of the circulating heat exchanger for supplementary methanation reaction, which finally produces product gas and is discharged and collected. The other part is circulated and processed by the circulating treatment component to produce a second circulating gas, which is then introduced into the second pipeline.

[0016] The load isolation unit includes a first blind plate and a second blind plate. The first blind plate is located on the fourth pipeline and the second blind plate is located on the eighth pipeline. When the passage between the fourth pipeline and the eighth pipeline is cut off by the first blind plate and the second blind plate, the second methanation reaction unit is isolated from the HPCO methanation treatment system.

[0017] Preferably, in the raw material supply unit, the composition of the purified gas is: CO: 17.93 mol%, CO2: 1.52 mol%, CH4: 18.86 mol%, H2: 60.75 mol%, O2: 0.41 mol%, C2H4: 0.04 mol%, C2H6: 0.16 mol%.

[0018] The composition of the feed gas is as follows: H2O: 1 mol%, H2: 60.14 mol%, CO: 17.75 mol%, CO2: 1.5 mol%, CH4: 18.67 mol%.

[0019] In the first methanation reaction unit and the second methanation reaction unit, the first process gas and the second process gas have the same composition: H2O: 20.32 mol%, H2: 19.74 mol%, CO: 1.61 mol%, CO2: 3.79 mol%, CH4: 54.03 mol%.

[0020] Preferably, in the raw material supply unit, the first pipeline is connected to the second and fourth pipelines via a tee connector;

[0021] Furthermore, in the first methanation reaction unit and the second methanation reaction unit, both the second pipeline and the fourth pipeline are three-way pipelines. One port of the second pipeline is connected to the first pipeline, and the other two ports are connected to the input ends of the two first methanation reactors, respectively. One port of the fourth pipeline is connected to the first pipeline, and the other two ports are connected to the input ends of the two second methanation reactors, respectively.

[0022] Preferably, in the first methanation reaction unit, the second pipeline is provided with a first inlet regulating valve, and the first inlet regulating valve is located upstream of the tee node of the second pipeline;

[0023] In the second methanation reaction unit, a second inlet regulating valve is provided on the fourth pipeline, and the second inlet regulating valve is located upstream of the tee node of the fourth pipeline;

[0024] Based on this, the first inlet regulating valve and the second inlet regulating valve distribute the raw material gas transported by the first pipeline in a 4:6 ratio, with 40% of the raw material gas being fed into the first methanation reaction unit and 60% of the raw material gas being fed into the second methanation reaction unit.

[0025] Preferably, in the heat recovery unit, the output end of the steam drum is provided with a first discharge pipeline and a second discharge pipeline, wherein the first discharge pipeline and the second discharge pipeline are respectively connected to the first methanation waste pot and the second methanation waste pot, and are used to provide saturated water to the first methanation waste pot and the second methanation waste pot respectively.

[0026] Preferably, in the circulating heat exchange unit, the circulating processing component includes a second flow pipeline located at the output end of the circulating heat exchanger. The second flow pipeline connects in series with the circulating boiler feedwater heater, the circulating demineralized water heater, the circulating separator, and the circulating compressor, and then returns to the circulating heat exchanger. After passing through the circulating heat exchanger, the second flow pipeline splits into two branches. The first branch is connected to the second pipeline, and the connection point is located upstream of the tee node of the second pipeline. The second branch is connected to the first pipeline, and a start-up heating furnace is also connected in series on the second branch.

[0027] Preferably, the supplementary methanation reaction unit includes a third methanation reactor and a fourth methanation reactor connected in series.

[0028] Preferably, the first methanation waste boiler and the steam superheater are respectively equipped with a first bypass valve and a second bypass valve, and the heat exchange of the first methanation waste boiler and the steam superheater are respectively regulated by the degree of closure of the first bypass valve and the second bypass valve.

[0029] Preferably, a first control valve is provided on the second pipeline, and the first control valve is located between the connection point of the first branch and the second pipeline and the tee node of the second pipeline, for controlling the on / off state of the second pipeline. In addition, the first inlet regulating valve is located between the connection point of the first pipeline and the second pipeline and the connection point of the second pipeline and the first branch.

[0030] A second control valve is provided on the branch connecting the second output pipeline to the circulating heat exchanger, which is used to control the opening and closing of the gas path between the steam superheater and the circulating heat exchanger; a third control valve is provided on the branch connecting the second output pipeline to the fourth pipeline, which is used to control the opening and closing of the gas path between the steam superheater and the second methanation reactor.

[0031] The input end of the circulating heat exchanger is equipped with a fourth control valve, which is used to control the opening and closing of the gas path entering the circulating heat exchanger.

[0032] A fifth control valve is provided on the first branch to control the on / off state of the first branch; a sixth control valve is provided on the second branch to control the on / off state of the second branch.

[0033] Furthermore, the present invention also provides an isolated operation process for an HPCO methanation treatment system, which employs the above-mentioned HPCO methanation treatment system and includes the following steps:

[0034] S1: When the second methanation reaction unit of the HPCO methanation treatment system needs to be repaired, the system should be shut down first, then the pressure of each pipeline in the system should be released, and then the fourth pipeline and the eighth pipeline should be cut off by plugging in the first blind plate and the second blind plate respectively, so as to isolate the second methanation reaction unit and the second methanation waste pot from the HPCO methanation treatment system.

[0035] S2: Adjust the opening status of the first inlet regulating valve and the second inlet regulating valve respectively to control the raw material gas transported by the first pipeline to enter the second pipeline and the fourth pipeline in a 4:6 ratio. At the same time, control the second bypass valve of the first bypass valve on the first methanation waste boiler and the steam superheater to close, so as to provide the maximum heat exchange for the first methanation waste boiler and the steam superheater. Then, control the sixth control valve to open, so that part of the second circulating gas obtained by the circulating processing component from the mixed process gas is introduced into the second pipeline, and the other part is introduced into the first pipeline after being cooled by the start-up heating furnace.

[0036] The beneficial effects of this invention are as follows:

[0037] (1) By optimizing the HPCO methanation system, the present invention uses a blind plate to isolate the second methanation reaction unit from the HPCO methanation system, so that when the second methanation reaction unit is under maintenance, the first methanation reaction unit can operate independently, thus avoiding the overall shutdown of the HPCO methanation system.

[0038] (2) The present invention utilizes the regulation of the second inlet regulating valve, the second bypass valve of the first methanation waste boiler and the steam superheater, and the sixth control valve to enable the heat of the reaction products of the first methanation reaction unit to be effectively exchanged, thus effectively solving the problem of heat imbalance during the operation of the first methanation reaction unit alone. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a schematic diagram illustrating the operating principle of the HPCO methanation system provided by the present invention. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0043] The HPCO methanation system provided in this technical solution is an improvement on the original HPCO methanation system. This improvement allows the first methanation unit to operate at full load when the second methanation unit requires isolation and maintenance, enabling long-term continuous operation of the methanation unit. The HPCO methanation system includes: a raw material supply unit, a first methanation unit, a second methanation unit, a heat recovery unit, a circulating heat exchange unit, a load isolation unit, and a supplementary methanation unit.

[0044] Specifically, such as Figure 1 As shown, the raw material supply unit includes a desulfurization tank 1. The input end of the desulfurization tank 1 is connected to a low-temperature methanol washing device via an external pipeline 2, which is used to introduce the purified gas provided by the low-temperature methanol washing device into the desulfurization tank 1. The desulfurization tank 1 performs fine desulfurization on the purified gas to generate raw material gas. The composition of the purified gas is: CO: 17.93 mol%, CO2: 1.52 mol%, CH4: 18.86 mol%, H2: 60.75 mol%, O2: 0.41 mol%, C2H4: 0.04 mol%, C2H6: 0.16 mol%, and unavoidable impurities containing sulfur: 0.33 mol%. The composition of the raw material gas is: H2O: 1 mol%, H2: 60.14 mol%, CO: 17.75 mol%, CO2: 1.5 mol%, CH4: 18.67 mol%, and unavoidable impurities: 0.94 mol%.

[0045] It should be noted that the desulfurization tank 1 is a commonly used device in the pretreatment unit for methanation reaction in the existing technology. The main function of this device is to perform fine desulfurization treatment on the purified gas to produce gaseous raw material for methanation reaction without sulfur element, thereby protecting the catalyst used in the first methanation reaction unit and the second methanation reaction unit. In addition, the output end of the desulfurization tank 1 is also equipped with a first pipeline 101 for exporting the raw material gas generated by fine desulfurization.

[0046] like Figure 1 As shown, the first methanation reaction unit includes two first methanation reactors 3 arranged in parallel. The input end of the first methanation reactor 3 is connected to the first pipeline 101 through the second pipeline 4, which is used to introduce the raw material gas into the first methanation reactor 3 for methanation reaction to obtain the first process gas. On this basis, the output end of the first methanation reactor 3 is provided with a third pipeline 5, which is used to export the first process gas from the first methanation reactor 3.

[0047] The second methanation reaction unit includes two second methanation reactors 6 arranged in parallel. The input end of the second methanation reactor 6 is connected to the first pipeline 101 through the fourth pipeline 7, which is used to introduce the raw material gas into the second methanation reactor 6 and carry out the methanation reaction to obtain the second process gas. On this basis, the output end of the second methanation reactor 6 is provided with a fifth pipeline 8, which is used to export the second process gas from the second methanation reactor 6.

[0048] In this embodiment, the methanation reactions carried out in the first methanation reactor 3 and the second methanation reactor 6 are exactly the same and are conventional reactions in the art. Therefore, the required conditions and reaction process will not be described in detail here. Based on this, the first process gas and the second process gas obtained by the first methanation reactor 3 and the second methanation reactor 6 have the same composition: H2O: 20.32 mol%, H2: 19.74 mol%, CO: 1.61 mol%, CO2: 3.79 mol%, CH4: 54.03 mol%, unavoidable impurities: 0.51 mol%. In addition, the temperature of the obtained first process gas and second process gas is about 620°C.

[0049] Based on the above embodiments, this technical solution configures the first pipeline 101 to be connected to the second pipeline 4 and the fourth pipeline 7 via a tee connector, and both the second pipeline 4 and the fourth pipeline 7 are tee pipelines; wherein, one port of the second pipeline 4 is connected to the first pipeline 101, and the other two ports are respectively connected to the input ends of the two first methanation reactors 3; one port of the fourth pipeline 7 is connected to the first pipeline 101, and the other two ports are respectively connected to the input ends of the two second methanation reactors 6.

[0050] In addition, a first inlet regulating valve 401 is provided on the second pipeline 4, and the first inlet regulating valve 401 is located upstream of the tee node of the second pipeline 4; a second inlet regulating valve 701 is provided on the fourth pipeline 7, and the second inlet regulating valve 701 is located upstream of the tee node of the fourth pipeline 7; based on this, the first inlet regulating valve 401 and the second inlet regulating valve 701 distribute the raw material gas transported by the first pipeline 101 in a 4:6 ratio, with 40% of the raw material gas being fed into the first methanation reaction unit and 60% of the raw material gas being fed into the second methanation reaction unit.

[0051] Thus, the HPCO methanation system provided by this technical solution can, under normal conditions, methanate the feed gas to obtain the first process gas and the second process gas. However, the HPCO methanation system obtained based on the above embodiments still has the following problems:

[0052] ① According to the existing process, the normal operation of the first methanation reactor 3 and the second methanation reactor 6 requires the mixing of circulating gas into the feed gas. The composition of the circulating gas is the same as that of the first process gas and the second process gas, and the temperature of the mixed gas should be lower than the rated feed gas input temperature of the first methanation reactor 3 and the second methanation reactor 6 by 280℃; ② The first process gas and the second process gas are not the final products of this processing system, and the temperature of the process gas prepared is relatively high, so heat exchange is required.

[0053] The following section will elaborate on the further processing of the first process gas and the second process gas.

[0054] like Figure 1 As shown, the heat recovery unit includes a first methanation waste boiler 9, a second methanation waste boiler 10, a steam superheater 11, and a steam drum 12, wherein:

[0055] The input end of the first methanation waste pot 9 is connected to the third pipeline 5, through which the first process gas is introduced into the first methanation waste pot 9 for preliminary heat exchange and to generate the first saturated steam. The temperature of the first process gas after preliminary heat exchange is about 460°C. In addition, the output end of the first methanation waste pot 9 is provided with a sixth pipeline 13 and a seventh pipeline 14. The sixth pipeline 13 is connected to the steam superheater 11, which is used to introduce the first process gas after preliminary heat exchange into the steam superheater 11 for further heat exchange. The seventh pipeline 14 is connected to the steam drum 12, which is used to introduce the first saturated steam into the steam drum 12 for further heat exchange to generate recovered steam.

[0056] The input end of the second methanation waste pot 10 is connected to the fifth pipeline 8, through which the second process gas is introduced to the second methanation waste pot 10 for preliminary heat exchange and to generate the second saturated steam. The temperature of the first process gas after preliminary heat exchange is about 364°C. The output end of the second methanation waste pot 10 is provided with an eighth pipeline 15 and a ninth pipeline 16. The eighth pipeline 15 is used to discharge the second process gas after preliminary heat exchange to the circulating heat exchange unit. The ninth pipeline 16 is connected to the steam drum 12 and is used to introduce the second saturated steam into the steam drum 12 for further heat exchange to generate recovered steam.

[0057] Based on the above embodiments, the output end of the steam drum 12 is provided with a first discharge pipeline 17 and a second discharge pipeline 18, wherein the first discharge pipeline 17 and the second discharge pipeline 18 are respectively connected to the first methanation waste pot 9 and the second methanation waste pot 10, and are used to provide saturated water to the first methanation waste pot 9 and the second methanation waste pot 10 respectively. This process is a common procedure for heat exchange operation in the art, so it is only briefly described here.

[0058] like Figure 1 As shown, the steam superheater 11 is connected to the output end of the steam drum 12 via the input pipeline 19, which is used to introduce the recovered steam in the steam drum 12 into the steam superheater 11, and to use the recovered steam to further heat exchange the first process gas. The temperature of the first process gas after heat exchange is about 320°C. Based on this, the output end of the steam superheater 11 is provided with a first output pipeline 20 and a second output pipeline 21. The first output pipeline 20 is connected to the steam utilization device 22, which is used to input the recovered steam after heat exchange into the steam utilization device 22 for utilization. The second output pipeline 21 is a three-way pipeline, one branch of which is connected to the fourth pipeline 7, and the other branch is connected to the circulating heat exchange unit. Part of the first process gas after heat exchange is introduced into the fourth pipeline 7 as the first circulating gas through the second output pipeline 21, which is used to mix with the raw material gas and enter the second methanation reactor 6 for methanation reaction. The other part directly enters the circulating heat exchange unit.

[0059] like Figure 1 As shown, the circulating heat exchange unit includes a circulating heat exchanger 23. The input end of the circulating heat exchanger 23 is connected to the second output pipeline 21 and the eighth pipeline 15 through a three-way connector. The first process gas and the second process gas are mixed to form a mixed process gas, which then enters the circulating heat exchanger 23 for circulating heat exchange. The temperature of the mixed process gas after heat exchange is about 280°C. The mixed process gas after heat exchange is divided into two parts. One part is introduced into the supplementary methanation reaction unit through the first flow pipeline 24 located at the output end of the circulating heat exchanger 23 for supplementary methanation reaction, and finally produces product gas which is discharged and collected. The other part is circulated by the circulating processing component to produce a second circulating gas, which is introduced into the second pipeline 4.

[0060] The supplementary methanation reaction unit includes a third methanation reactor 25 and a fourth methanation reactor 38 connected in series. The mixed process gas is sequentially subjected to methanation reactions in the third methanation reactor 25 and the fourth methanation reactor 38 to finally obtain a product gas with a CH4 content greater than 91.5 mol%. Since this application is not a system improvement for the final production of the product gas, the preparation of the final product gas still uses existing process parameters and will not be described in detail here.

[0061] Thus, the HPCO methanation system provided in this application can perform methanation treatment of the feed gas under normal conditions and finally produce product gas with a CH4 content greater than 91.5 mol%. However, the core objective of this application is that when the second methanation reaction unit needs to be isolated for maintenance, the first methanation reaction unit can work at full load. That is, the first methanation reaction unit can completely process 40% of the feed gas, realizing long-term continuous operation of the methanation unit.

[0062] Based on this objective, the following needs to be considered: First, how to ensure that the first methanation reaction unit can still operate when the second methanation reaction unit is isolated for maintenance; second, how to effectively handle the heat generated when the first methanation reaction unit is operating at full load to achieve thermal balance.

[0063] In view of this, this application further incorporates a circulating processing component and a load isolation unit into the aforementioned HPCO methanation system, wherein:

[0064] like Figure 1 As shown, the circulating treatment component includes a second flow line 26 located at the output end of the circulating heat exchanger 23. The second flow line 26 is connected in series with the circulating boiler feedwater heater 27, the circulating demineralized water heater 28, the circulating separator 29, and the circulating compressor 30, and then returns to the circulating heat exchanger 23. After passing through the circulating heat exchanger 23, the second flow line 26 is divided into two branches. The first branch 31 is connected to the second line 4, and the connection point is located upstream of the tee node of the second line 4. It is used to introduce the second circulating gas into the first methanation reactor 3. The second branch 32 is connected to the first line 101, and the start-up heating furnace 33 is also connected in series on the second branch 32.

[0065] Based on the above embodiments, the mixed process gas after heat exchange in the circulating heat exchanger 23 is divided into two parts. The mixed process gas entering the circulating processing assembly is continuously cooled to 152°C by the circulating boiler feedwater heater 27 and the circulating demineralized water heater 28. Then, the condensate in the mixed process gas is separated by the circulating separator 29. The remaining mixed process gas is pressurized by the circulating compressor 30 and sent to the circulating heat exchanger 23 to be heated to 326°C. The heated mixed process gas is again divided into two parts. One part serves as the second circulating gas and is introduced into the first methanation reactor 3 via the first branch 31. The other part is cooled to [temperature missing] by the start-up heater 33. After reaching approximately 180°C, the gas is introduced into the first pipeline 101 to mix and reduce the temperature of the raw material gas to below the rated raw material input temperature of the first methanation reactor 3 and the second methanation reactor 6. This prevents the reactor from overheating and maintains a certain carbon safety factor in the reactor, avoiding the possibility of carbon precipitation on the surface of the reactor catalyst. It should be noted that the circulating boiler feedwater heater 27 and the circulating demineralized water heater 28 are used to heat boiler water and demineralized water, respectively, in existing coal chemical processes. However, even when used for heating, their temperature is lower than that of the mixed process gas after heat exchange in the circulating heat exchanger 23. Therefore, in this application, they are directly used to exchange heat and cool the mixed process gas.

[0066] It should be noted that the application of cooling for the second branch 32 and the start-up heating furnace 33 is based on the fact that after isolating the second methanation reaction unit from the HPCO methanation treatment system, if the first methanation reaction unit is working at full load, the heat recovery unit cannot exchange the heat of the first process gas as required, that is, the temperature of the second circulating gas cannot reach the required level, which will cause the first methanation reaction unit to malfunction.

[0067] In addition to the application of the second branch 32 and the start-up heating furnace 33 for cooling, other parts of the HPCO methanation system also need to be configured in coordination. Specifically, the first methanation waste pot 9 and the steam superheater 11 are respectively equipped with a first bypass valve 34 and a second bypass valve 35. The degree of closure of the first bypass valve 34 and the second bypass valve 35 is used to regulate the heat exchange of the first methanation waste pot 9 and the steam superheater 11. In this embodiment, the first bypass valve 34 and the second bypass valve 35 are completely closed in order to achieve the maximum heat exchange of the first methanation waste pot 9 and the steam superheater 11. Finally, with the first bypass valve 34 and the second bypass valve 35 closed, in conjunction with the cooling application of the second branch 32 and the start-up heating furnace 33, the heat balance during the full-load operation of the first methanation reaction unit is achieved.

[0068] The above describes the solution for heat balance during the operation of the first methanation reaction unit at full load. Next, we will elaborate on how to isolate the second methanation reaction unit from the HPCO methanation system so that the first methanation reaction unit can operate independently.

[0069] like Figure 1 As shown, the load isolation unit includes a first blind plate 36 and a second blind plate 37. The first blind plate 36 is installed on the fourth pipeline 7, and the second blind plate 37 is installed on the eighth pipeline 15. When the passage between the fourth pipeline 7 and the eighth pipeline 15 is cut off by the first blind plate 36 and the second blind plate 37, the second methanation reaction unit is isolated from the HPCO methanation treatment system.

[0070] In addition, this application also includes control valves installed on each pipeline for the overall operation of the HPCO methanation treatment system, such as... Figure 1 As shown, specifically:

[0071] The second pipeline 4 is provided with a first control valve 402, which is located between the connection point of the first branch 31 and the second pipeline 4 and the tee node of the second pipeline 4, and is used to control the opening and closing of the second pipeline 4. In addition, the first inlet regulating valve 401 is located between the connection point of the first pipeline 101 and the second pipeline 4 and the connection point of the second pipeline 4 and the first branch 31.

[0072] A second control valve 211 is provided on the branch connecting the second output pipeline 21 and the circulating heat exchanger 23 to control the opening and closing of the gas passage between the steam superheater 11 and the circulating heat exchanger 23; a third control valve 212 is provided on the branch connecting the second output pipeline 21 and the fourth pipeline 7 to control the opening and closing of the gas passage between the steam superheater 11 and the second methanation reactor 6.

[0073] The input end of the circulating heat exchanger 23 is equipped with a fourth control valve 231, which is used to control the opening and closing of the gas path entering the circulating heat exchanger 23.

[0074] The first branch 31 is equipped with a fifth control valve 311, which is used to control the opening and closing of the first branch 31; the second branch 32 is equipped with a sixth control valve 321, which is used to control the opening and closing of the second branch 32.

[0075] Based on the HPCO methanation system described above, this application also provides an isolation operation process for the HPCO methanation system, used to isolate the second methanation reaction unit from the HPCO methanation system during maintenance, while the first methanation reaction unit can still operate at full load. The specific steps are as follows:

[0076] S1: When the second methanation reaction unit of the HPCO methanation treatment system needs to be inspected and repaired, the system is first shut down. Then, the control valves are used to depressurize and close the pipelines of the system. Subsequently, the fourth pipeline 7 and the eighth pipeline 15 are cut off by plugging in the first blind plate 36 and the second blind plate 37 respectively, thus isolating the second methanation reaction unit and the second methanation waste pot 10 from the HPCO methanation treatment system.

[0077] S2: Start the HPCO methanation system and adjust the opening state of the first inlet regulating valve 401 to control the raw material gas delivered by the first pipeline 101 to enter the second pipeline 4 at a ratio of 40%. At the same time, control the second bypass valve 35 of the first bypass valve 34 on the first methanation waste boiler 9 and the steam superheater 11 to close, so as to provide the first methanation waste boiler 9 and the steam superheater 11 with the maximum heat exchange. Then, control the sixth control valve 321 to open, so that part of the second circulating gas obtained by the circulating treatment component from the mixed process gas is introduced into the second pipeline 4, and the other part is introduced into the first pipeline 101 after being cooled by the start-up heating furnace 33.

[0078] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An HPCO methanation treatment system, characterized in that, include: The raw material supply unit includes a desulfurization tank. The input end of the desulfurization tank is connected to a low-temperature methanol washing device via an external pipeline for introducing purified gas provided by the low-temperature methanol washing device into the desulfurization tank. The desulfurization tank performs fine desulfurization on the purified gas to generate raw material gas. The output end of the desulfurization tank is also provided with a first pipeline for exporting the raw material gas generated by fine desulfurization. The first methanation reaction unit includes two first methanation reactors arranged in parallel. The input end of the first methanation reactor is connected to the first pipeline through a second pipeline for feeding the feed gas into the first methanation reactor to carry out the methanation reaction and obtain the first process gas. On this basis, the output end of the first methanation reactor is provided with a third pipeline for discharging the first process gas out of the first methanation reactor. The second methanation reaction unit includes two second methanation reactors arranged in parallel. The input end of the second methanation reactor is connected to the first pipeline through a fourth pipeline for feeding the feed gas into the second methanation reactor and performing the methanation reaction to obtain the second process gas. On this basis, the output end of the second methanation reactor is provided with a fifth pipeline for discharging the second process gas out of the second methanation reactor. The heat recovery unit includes a first methanation waste boiler, a second methanation waste boiler, a steam superheater, and a steam drum, wherein: The input end of the first methanation waste pot is connected to the third pipeline, through which the first process gas is introduced to the first methanation waste pot for preliminary heat exchange and to generate the first saturated steam. The output end of the first methanation waste pot is provided with a sixth pipeline and a seventh pipeline. The sixth pipeline is connected to a steam superheater, through which the first process gas after preliminary heat exchange is introduced to the steam superheater for further heat exchange. The seventh pipeline is connected to a steam drum, through which the first saturated steam is introduced to the steam drum for further heat exchange to generate recovered steam. The input end of the second methanation waste pot is connected to the fifth pipeline, through which the second process gas is introduced to the second methanation waste pot for preliminary heat exchange and to generate the second saturated steam. The output end of the second methanation waste pot is provided with an eighth pipeline and a ninth pipeline. The eighth pipeline is used to discharge the second process gas after preliminary heat exchange to the circulating heat exchange unit. The ninth pipeline is connected to the steam drum and is used to introduce the second saturated steam into the steam drum for further heat exchange to generate recovered steam. The steam superheater is connected to the output end of the steam drum via an input pipeline. It is used to introduce the recovered steam from the steam drum into the steam superheater and use the recovered steam to further exchange heat with the first process gas. On this basis, the output end of the steam superheater is provided with a first output pipeline and a second output pipeline. The first output pipeline is connected to a steam utilization device to input the recovered steam after heat exchange into the steam utilization device for utilization. The second output pipeline is a three-way pipeline, one branch of which is connected to a fourth pipeline and the other branch is connected to a circulating heat exchange unit. The first process gas after heat exchange is partially introduced into the fourth pipeline as the first circulating gas through the second output pipeline, and the other part directly enters the circulating heat exchange unit. The circulating heat exchange unit includes a circulating heat exchanger. The input end of the circulating heat exchanger is connected to the second output pipeline and the eighth pipeline through a three-way connector. The first process gas and the second process gas are mixed to form a mixed process gas, which then enters the circulating heat exchanger for circulating heat exchange. The mixed process gas after heat exchange is divided into two parts. One part is introduced into the supplementary methanation reaction unit through the first flow pipeline located at the output end of the circulating heat exchanger for supplementary methanation reaction, which finally produces product gas and is discharged and collected. The other part is circulated and processed by the circulating treatment component to produce a second circulating gas, which is then introduced into the second pipeline. The load isolation unit includes a first blind plate and a second blind plate. The first blind plate is located on the fourth pipeline and the second blind plate is located on the eighth pipeline. When the passage between the fourth pipeline and the eighth pipeline is cut off by the first blind plate and the second blind plate, the second methanation reaction unit is isolated from the HPCO methanation treatment system.

2. The HPCO methanation system according to claim 1, characterized in that: In the raw material supply unit, the composition of the purified gas is: CO: 17.93 mol%, CO2: 1.52 mol%, CH4: 18.86 mol%, H2: 60.75 mol%, O2: 0.41 mol%, C2H4: 0.04 mol%, C2H6: 0.16 mol%. The composition of the feed gas is as follows: H2O: 1 mol%, H2: 60.14 mol%, CO: 17.75 mol%, CO2: 1.5 mol%, CH4: 18.67 mol%. In the first methanation reaction unit and the second methanation reaction unit, the first process gas and the second process gas have the same composition: H2O: 20.32 mol%, H2: 19.74 mol%, CO: 1.61 mol%, CO2: 3.79 mol%, CH4: 54.03 mol%.

3. The HPCO methanation system according to claim 2, characterized in that: In the raw material supply unit, the first pipeline is connected to the second and fourth pipelines via a tee connector; Furthermore, in the first methanation reaction unit and the second methanation reaction unit, both the second pipeline and the fourth pipeline are three-way pipelines. One port of the second pipeline is connected to the first pipeline, and the other two ports are connected to the input ends of the two first methanation reactors, respectively. One port of the fourth pipeline is connected to the first pipeline, and the other two ports are connected to the input ends of the two second methanation reactors, respectively.

4. The HPCO methanation system according to claim 3, characterized in that: In the first methanation reaction unit, a first inlet regulating valve is provided on the second pipeline, and the first inlet regulating valve is located upstream of the tee node of the second pipeline; In the second methanation reaction unit, a second inlet regulating valve is provided on the fourth pipeline, and the second inlet regulating valve is located upstream of the tee node of the fourth pipeline; Based on this, the first inlet regulating valve and the second inlet regulating valve distribute the raw material gas transported by the first pipeline in a 4:6 ratio, with 40% of the raw material gas being fed into the first methanation reaction unit and 60% of the raw material gas being fed into the second methanation reaction unit.

5. The HPCO methanation system according to claim 4, characterized in that: In the heat recovery unit, the output end of the steam drum is provided with a first discharge pipeline and a second discharge pipeline, wherein the first discharge pipeline and the second discharge pipeline are respectively connected to the first methanation waste pot and the second methanation waste pot, and are used to provide saturated water to the first methanation waste pot and the second methanation waste pot respectively.

6. The HPCO methanation system according to claim 5, characterized in that: In the circulating heat exchange unit, the circulating processing component includes a second flow pipeline located at the output end of the circulating heat exchanger. The second flow pipeline connects in series with the circulating boiler feedwater heater, the circulating demineralized water heater, the circulating separator, and the circulating compressor, and then returns to the circulating heat exchanger. After passing through the circulating heat exchanger, the second flow pipeline splits into two branches. The first branch is connected to the second pipeline, and the connection point is located upstream of the tee node of the second pipeline. The second branch is connected to the first pipeline, and a start-up heating furnace is also connected in series on the second branch.

7. The HPCO methanation system according to claim 6, characterized in that: The supplementary methanation reaction unit includes a third methanation reactor and a fourth methanation reactor connected in series.

8. The HPCO methanation system according to claim 7, characterized in that: The first methanation waste boiler and the steam superheater are respectively equipped with a first bypass valve and a second bypass valve, and the heat exchange of the first methanation waste boiler and the steam superheater are respectively regulated by the degree of closure of the first bypass valve and the second bypass valve.

9. The HPCO methanation system according to claim 8, characterized in that: The second pipeline is equipped with a first control valve, which is located between the connection point of the first branch and the second pipeline and the tee node of the second pipeline, and is used to control the opening and closing of the second pipeline. In addition, the first inlet regulating valve is located between the connection point of the first pipeline and the second pipeline and the connection point of the second pipeline and the first branch. A second control valve is provided on the branch connecting the second output pipeline to the circulating heat exchanger, which is used to control the opening and closing of the gas path between the steam superheater and the circulating heat exchanger; a third control valve is provided on the branch connecting the second output pipeline to the fourth pipeline, which is used to control the opening and closing of the gas path between the steam superheater and the second methanation reactor. The input end of the circulating heat exchanger is equipped with a fourth control valve, which is used to control the opening and closing of the gas path entering the circulating heat exchanger. A fifth control valve is provided on the first branch to control the on / off state of the first branch; a sixth control valve is provided on the second branch to control the on / off state of the second branch.

10. An isolated operation process for an HPCO methanation treatment system, employing the HPCO methanation treatment system according to any one of claims 1-9, characterized in that, Includes the following steps: S1: When the second methanation reaction unit of the HPCO methanation treatment system needs to be repaired, the system should be shut down first, then the pressure of each pipeline in the system should be released, and then the fourth pipeline and the eighth pipeline should be cut off by plugging in the first blind plate and the second blind plate respectively, so as to isolate the second methanation reaction unit and the second methanation waste pot from the HPCO methanation treatment system. S2: Start the HPCO methanation treatment system and adjust the opening status of the first inlet regulating valve to control the raw material gas delivered by the first pipeline to enter the second pipeline at a ratio of 40%. At the same time, control the second bypass valve of the first bypass valve on the first methanation waste boiler and the steam superheater to close, so as to provide the first methanation waste boiler and the steam superheater with the maximum heat exchange. Then, control the sixth control valve to open, so that part of the second circulating gas obtained by the circulating treatment component from the mixed process gas is introduced into the second pipeline, and the other part is introduced into the first pipeline after being cooled by the start-up heating furnace.

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