Methanol synthesis gas precooling system

Abstract

The utility model relates to a precooling system for methanol synthesis gas, and belongs to the technical field of gas precooling. Comprising a compressor, a filter, a precooler, an emptying valve, a temperature sensor and a controller. One part of the nitrogen compressed by the compressor is conveyed to the filter, and the other part of the nitrogen is conveyed to the precooler, so that the amount of the nitrogen passing through the precooler is small, impurities in the precooler are few, blockage in the precooler is avoided, the amount of the conveyed nitrogen and the cooling effect on a dehydrogenation tower and a decarburization tower are ensured, and the service life of the dehydrogenation tower and the decarburization tower is prolonged. And the cleaning period of the precooler is prolonged. After the precooler runs for a certain time, the controller opens the emptying valve, the nitrogen in the dehydrogenation tower and the decarburization tower is used for back flushing the interior of the precooler, so that the nitrogen is used for purging impurities remained in the precooler, the cleaning of the precooler is completed, in the purging process, the nitrogen can still be conveyed to the dehydrogenation tower and the decarburization tower through the filter for cooling, and the cleaning efficiency of the precooler is improved. And the influence on the cooling effect of the condenser of the dehydrogenation tower and the condenser of the decarburization tower is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of gas precooling, in particular to a precooling system for methanol synthesis gas. Background Art

[0002] In the process of methanol production, nitrogen needs to be compressed and cooled, and then the condensers of the decarbonization tower and the dehydrogenation tower are cooled, so that methane in the rich-carbon gas tail gas of the decarbonization tower and the rich-hydrogen gas tail gas of the dehydrogenation tower is liquefied, so that hydrogen and carbon in the rich-carbon gas tail gas and the rich-hydrogen gas tail gas are separated, and part of the gas as methanol synthesis gas is transported to the methanol synthesis equipment for methanol preparation.

[0003] However, with the continuous transportation of nitrogen, the channels inside the precooler responsible for cooling nitrogen are easily blocked by impurities carried by nitrogen, resulting in an increase in channel resistance, poor circulation of nitrogen inside the precooler, a relatively small amount of nitrogen transported by the precooler, and thus a reduction in the cooling effect of nitrogen on the condensers of the decarbonization tower and the dehydrogenation tower. As a result, the temperatures of the rich-carbon gas tail gas and the rich-hydrogen gas tail gas are difficult to reach the process indicators, the liquefaction recovery rate of methane is low, and the purity of the separated hydrogen and carbon is poor, which easily affects the subsequent methanol preparation. Summary of the Utility Model

[0004] To solve the above technical problems, the utility model provides a precooling system for methanol synthesis gas. The technical solution of the utility model is as follows:

[0005] The utility model provides a pre-cooling system for methanol synthesis gas, which includes a liquid nitrogen storage tank, a vaporizer, a compressor, a filter, a pre-cooler, a first stop valve, a second stop valve, a third stop valve, a fourth stop valve, a fifth stop valve, a vent valve, a gas recovery device, a temperature sensor and a controller. The outlet of the liquid nitrogen storage tank is connected to the inlet of the vaporizer through a connecting pipe. The outlet of the vaporizer is connected to the first inlet of the compressor through a connecting pipe. The outlet of the compressor is connected to one end of a first main pipe. The other end of the first main pipe is connected to one end of a first branch pipe and a second branch pipe. The other end of the first branch pipe is connected to the inlet of the filter. The other end of the second branch pipe is connected to the inlet of the pre-cooler. The outlet of the filter is connected to one end of a second main pipe through a third branch pipe. The outlet of the pre-cooler is connected to one end of the second main pipe through a fourth branch pipe. The other end of the second main pipe is connected to the inlets of a decarbonization tower and a dehydrogenation tower. The first outlets of the decarbonization tower and the dehydrogenation tower are both connected to the second inlet of the compressor through connecting pipes. The second outlet of the decarbonization tower is connected to the inlet of a gas compression device through a connecting pipe. The second outlet of the dehydrogenation tower is connected to the first inlet of a methanol synthesis device through a connecting pipe. The outlet of the gas compression device is connected to the second inlet of the methanol synthesis device. The gas recovery device is connected to the second branch pipe through a fifth branch pipe. The temperature sensor is connected to the second main pipe;

[0006] The first stop valve is connected to the first branch pipe. The second stop valve is connected to the third branch pipe. The third stop valve is connected to the second branch pipe. The fourth stop valve is connected to the fourth branch pipe. The fifth stop valve is connected to the connecting pipe between the first outlets of the decarbonization tower and the dehydrogenation tower and the second inlet of the compressor. The vent valve is connected to the fifth branch pipe. The first stop valve, the second stop valve, the third stop valve, the fourth stop valve, the fifth stop valve, the vent valve and the temperature sensor are all electrically connected to the controller.

[0007] Optionally, a pre-cooling system for methanol synthesis gas further includes four pressure gauges. Two of the pressure gauges are respectively connected to the inlet and the outlet of the filter. The other two pressure gauges are respectively connected to the inlet and the outlet of the pre-cooler. The four pressure gauges are all electrically connected to the controller.

[0008] Optionally, a pre-cooling system for methanol synthesis gas further includes a flow control valve. The flow control valve is connected to the connecting pipe between the liquid nitrogen storage tank and the vaporizer. The flow control valve is electrically connected to the controller.

[0009] Optionally, a pre-cooling system for methanol synthesis gas further includes a sixth shut-off valve, which is connected to the connecting pipeline between the outlet of the vaporizer and the first inlet of the compressor.

[0010] All of the above optional technical solutions can be arbitrarily combined, and the present utility model does not elaborate on the structures after one-by-one combination.

[0011] By means of the above solutions, the beneficial effects of the present utility model are as follows:

[0012] By providing a vaporizer, a filter, a pre-cooler, a first shut-off valve, a second shut-off valve, a third shut-off valve, a fourth shut-off valve, a fifth shut-off valve, and a temperature sensor, liquid nitrogen in a liquid nitrogen storage tank is transported to the vaporizer for vaporization treatment to obtain nitrogen. The nitrogen is compressed by a compressor. At this time, the controller controls the opening of the first shut-off valve and the second shut-off valve, so that all the compressed nitrogen is transported to the filter for filtration treatment, and then transported to a dehydrogenation tower and a decarbonization tower to preliminarily cool the condensers of the decarbonization tower and the dehydrogenation tower. As nitrogen continues to be transported to the dehydrogenation tower and the decarbonization tower, the nitrogen that has been cooled first is transported to the compressor from the first outlets of the decarbonization tower and the dehydrogenation tower through a connecting pipeline and a fifth shut-off valve. At this time, the nitrogen that has been cooled first entering the compressor carries heat and is compressed by the compressor again and then transported to the dehydrogenation tower and the decarbonization tower, which is likely to reduce the cooling effect on the condensers of the decarbonization tower and the dehydrogenation tower. When the controller determines according to the temperature sensor that the temperatures of the condensers of the dehydrogenation tower and the decarbonization tower do not reach the temperature requirements for liquefying methane, the controller controls the opening of the third shut-off valve and the fourth shut-off valve, so that a part of the nitrogen transported by the compressor continues to be transported to the dehydrogenation tower and the decarbonization tower through the filter, and the other part of the nitrogen enters the pre-cooler for cooling treatment. The cooled nitrogen is then transported to the dehydrogenation tower and the decarbonization tower to further cool the condensers of the dehydrogenation tower and the decarbonization tower, so that the temperatures of the condensers of the dehydrogenation tower and the decarbonization tower reach the temperature requirements for liquefying methane. Since a part of the nitrogen transported by the compressor enters the filter and the other part enters the pre-cooler, the amount of nitrogen passing through the pre-cooler is small, and the impurities remaining inside the pre-cooler are few, avoiding the situation of blockage of the internal channels of the pre-cooler. Therefore, while ensuring the amount of nitrogen transported and the cooling effect on the condensers of the dehydrogenation tower and the decarbonization tower, the present utility model also extends the cleaning cycle of the pre-cooler.

[0013] By setting the vent valve, after the pre-cooler has been operating for a certain period of time, the controller opens the vent valve, closes the third stop valve and the fifth stop valve, and uses the nitrogen in the dehydrogenation tower and the decarbonization tower to backflush the inside of the pre-cooler, so that the nitrogen purges the impurities remaining in the pre-cooler, thus completing the cleaning of the pre-cooler. And during the purging process, the nitrogen can still be transported to the dehydrogenation tower and the decarbonization tower through the filter to cool the condensers of the dehydrogenation tower and the decarbonization tower, so as to reduce the influence on the cooling effect of the condensers of the dehydrogenation tower and the decarbonization tower.

[0014] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly and to be implemented in accordance with the content of the description, the following describes in detail with reference to the preferred embodiments of the present invention and the accompanying drawings. Brief Description of the Drawings

[0015] Figure 1 It is a schematic diagram of the system composition of the present invention.

[0016] Explanation of the Reference Numerals in the Drawings:

[0017] 1. Liquid nitrogen storage tank; 2. Vaporizer; 3. Compressor; 4. First main pipe; 5. First branch pipe; 6. Second branch pipe; 7. Third branch pipe; 8. Fourth branch pipe; 9. Fifth branch pipe; 10. Second main pipe; 11. Filter; 12. Pre-cooler; 13. Decarbonization tower; 14. Dehydrogenation tower; 15. Gas compression equipment; 16. Methanol synthesis equipment; 17. First stop valve; 18. Second stop valve; 19. Third stop valve; 20. Fourth stop valve; 21. Fifth stop valve; 22. Vent valve; 23. Gas recovery device; 24. Temperature sensor; 25. Pressure gauge; 26. Flow control valve; 27. Sixth stop valve. Detailed Embodiment

[0018] The following further describes in detail the specific embodiments of the present invention with reference to the drawings and embodiments. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0019] As Figure 1As shown in the figure, a pre-cooling system for methanol synthesis gas provided by the present utility model includes a liquid nitrogen storage tank 1, a vaporizer 2, a compressor 3, a filter 11, a pre-cooler 12, a first stop valve 17, a second stop valve 18, a third stop valve 19, a fourth stop valve 20, a fifth stop valve 21, a vent valve 22, a gas recovery device 23, a temperature sensor 24 and a controller. The outlet of the liquid nitrogen storage tank 1 is connected to the inlet of the vaporizer 2 through a connecting pipe. The outlet of the vaporizer 2 is connected to the first inlet of the compressor 3 through a connecting pipe. The outlet of the compressor 3 is connected to one end of a first main pipe 4. The other end of the first main pipe 4 is connected to one end of a first branch pipe 5 and a second branch pipe 6. The other end of the first branch pipe 5 is connected to the inlet of the filter 11. The other end of the second branch pipe 6 is connected to the inlet of the pre-cooler 12. The outlet of the filter 11 is connected to one end of a second main pipe 10 through a third branch pipe 7. The outlet of the pre-cooler 12 is connected to one end of the second main pipe 10 through a fourth branch pipe 8. The other end of the second main pipe 10 is connected to the inlets of a decarbonization tower 13 and a dehydrogenation tower 14. The first outlets of the decarbonization tower 13 and the dehydrogenation tower 14 are both connected to the second inlet of the compressor 3 through connecting pipes. The second outlet of the decarbonization tower 13 is connected to the inlet of a gas compression device 15 through a connecting pipe. The second outlet of the dehydrogenation tower 14 is connected to the first inlet of a methanol synthesis device 16 through a connecting pipe. The outlet of the gas compression device 15 is connected to the second inlet of the methanol synthesis device 16. The gas recovery device 23 is connected to the second branch pipe 6 through a fifth branch pipe 9. The temperature sensor 24 is connected to the second main pipe 10;

[0020] The first stop valve 17 is connected to the first branch pipe 5. The second stop valve 18 is connected to the third branch pipe 7. The third stop valve 19 is connected to the second branch pipe 6. The fourth stop valve 20 is connected to the fourth branch pipe 8. The fifth stop valve 21 is connected to the connecting pipe between the first outlets of the decarbonization tower 13 and the dehydrogenation tower 14 and the second inlet of the compressor 3. The vent valve 22 is connected to the fifth branch pipe 9;

[0021] The first stop valve 17, the second stop valve 18, the third stop valve 19, the fourth stop valve 20, the fifth stop valve 21, the vent valve 22 and the temperature sensor 24 are all electrically connected to the controller.

[0022] Specifically, in the present utility model, the filter 11 can be selected from filters commonly used in the prior art such as a Leslie filter.

[0023] In a specific embodiment, the liquid nitrogen storage tank 1 transports liquid nitrogen to the vaporizer 2 for vaporization treatment to obtain nitrogen. The nitrogen is compressed by the compressor 3. At this time, the controller controls the opening of the first stop valve 17 and the second stop valve 18, so that all the compressed nitrogen is transported to the filter 11 for filtration treatment, and then transported to the dehydrogenation tower 14 and the decarbonization tower 13 to preliminarily cool the condensers of the decarbonization tower 13 and the dehydrogenation tower 14. As the nitrogen continues to be transported to the dehydrogenation tower 14 and the decarbonization tower 13, the nitrogen that has been cooled first is transported from the first outlets of the decarbonization tower 13 and the dehydrogenation tower 14 to the compressor 3 through the connecting pipe and the fifth stop valve 21. At this time, the nitrogen that has been cooled first entering the compressor 3 carries heat and is compressed by the compressor 3 again and then transported to the dehydrogenation tower 14 and the decarbonization tower 13, which is likely to reduce the cooling effect on the condensers of the decarbonization tower 13 and the dehydrogenation tower 14. When the controller determines according to the temperature sensor 24 that the temperatures of the condensers of the dehydrogenation tower 14 and the decarbonization tower 13 do not reach the temperature requirements for liquefying methane, the controller controls the opening of the third stop valve 19 and the fourth stop valve 20, so that a part of the nitrogen transported by the compressor 3 continues to be transported to the dehydrogenation tower 14 and the decarbonization tower 13 through the filter 11, and the other part of the nitrogen enters the precooler 12 for cooling treatment. The cooled nitrogen is then transported to the dehydrogenation tower 14 and the decarbonization tower 13 to further cool the condensers of the dehydrogenation tower 14 and the decarbonization tower 13, so that the temperatures of the condensers of the dehydrogenation tower 14 and the decarbonization tower 13 reach the temperature requirements for liquefying methane.

[0024] In the present utility model, since a part of the nitrogen transported by the compressor 3 enters the filter 11 and the other part enters the precooler 12, the amount of nitrogen passing through the precooler 12 is small, and the impurities remaining inside the precooler 12 are few, which can avoid the situation of blockage of the internal channels of the precooler 12. Therefore, while ensuring the amount of nitrogen transported and the cooling effect on the condensers of the dehydrogenation tower 14 and the decarbonization tower 13, the present utility model also extends the cleaning cycle of the precooler 12.

[0025] The present utility model is provided with a vent valve 22. After the precooler 12 operates for a certain period of time, the controller opens the vent valve 22 and closes the third stop valve 19 and the fifth stop valve 21, so that the nitrogen that has been cooled in the dehydrogenation tower 14 and the decarbonization tower 13 no longer enters the compressor 3, but blows back the inside of the precooler 12, so that the nitrogen purges the impurities remaining in the precooler 12, thereby completing the cleaning of the precooler 12. And during the purging process, the nitrogen transported by the compressor 3 can still be transported to the dehydrogenation tower 14 and the decarbonization tower 13 through the filter 11 to cool the condensers of the dehydrogenation tower 14 and the decarbonization tower 13, so as to reduce the influence on the cooling effect of the condensers of the dehydrogenation tower 14 and the decarbonization tower 13.

[0026] Optionally, a pre-cooling system for methanol synthesis gas further includes four pressure gauges 25, two of which are respectively connected to the inlet and outlet of the filter 11, and the other two pressure gauges 25 are respectively connected to the inlet and outlet of the pre-cooler 12. All four pressure gauges 25 are electrically connected to the controller.

[0027] Specifically, the four pressure gauges 25 in the present utility model are all shock-resistant pressure gauges.

[0028] In a specific embodiment, two of the pressure gauges 25 are respectively connected to the inlet and outlet of the filter 11 for real-time detection of the pressure value of the nitrogen gas input at the inlet of the filter 11 and the pressure value of the nitrogen gas output at the outlet of the filter 11; the other two pressure gauges 25 are respectively connected to the inlet and outlet of the pre-cooler 12 for real-time detection of the pressure value of the nitrogen gas input at the inlet of the pre-cooler 12 and the pressure value of the nitrogen gas output at the outlet of the pre-cooler 12.

[0029] The four pressure gauges 25 transmit signals to the controller in real time. The controller determines whether the filter 11 and the pre-cooler 12 are blocked according to the signals transmitted by the pressure gauges 25. Specifically, when the controller analyzes that the pressure value of the pressure gauge 25 connected to the inlet of the filter 11 or the pre-cooler 12 is significantly higher than the pressure value of the pressure gauge 25 connected to the outlet of the filter 11 or the pre-cooler 12, it is determined that the inside of the filter 11 or the pre-cooler 12 is blocked; when the controller analyzes that the pressure value of the pressure gauge 25 connected to the inlet of the filter 11 or the pre-cooler 12 is the same as or differs little from the pressure value of the pressure gauge 25 connected to the outlet of the filter 11 or the pre-cooler 12, it is determined that the inside of the filter 11 or the pre-cooler 12 is not blocked.

[0030] Optionally, a pre-cooling system for methanol synthesis gas further includes a flow control valve 26. The flow control valve 26 is connected to the connecting pipe between the liquid nitrogen storage tank 1 and the vaporizer 2, and the flow control valve 26 is electrically connected to the controller.

[0031] According to different actual production situations, the controller can control the opening degree of the flow control valve 26, thereby controlling the output flow of liquid nitrogen, and thus controlling the gas volume of liquid nitrogen gasification.

[0032] Optionally, a pre-cooling system for methanol synthesis gas further includes a sixth stop valve 27. The sixth stop valve 27 is connected to the connecting pipe between the outlet of the vaporizer 2 and the first inlet of the compressor 3.

[0033] Specifically, the first stop valve 17, the second stop valve 18, the third stop valve 19, the fourth stop valve 20, the fifth stop valve 21 and the sixth stop valve 27 in the present utility model are all DN200 stop valves.

[0034] According to different actual production situations, the opening degree of the sixth cut-off valve 27 can be controlled by a controller, so as to control the amount of nitrogen gas output.

[0035] In summary, a pre-cooling system for methanol synthesis gas provided by the present utility model, by setting a filter 11 and a pre-cooler 12, enables the compressed nitrogen gas output by the compressor 3 to be transported to the dehydrogenation tower 14 and the decarbonization tower 13 through two paths, which can not only reduce the impurity content in the transported nitrogen gas, but also reduce the blockage phenomenon inside the pre-cooler 12 and extend the service life of the pre-cooler 12; by setting four pressure gauges 25, the pressure values at the inlets and outlets of the filter 11 and the pre-cooler 12 can be detected in real time, so as to judge whether there is a blockage phenomenon inside the filter 11 and the pre-cooler 12, and then clean in time to reduce the influence on the cooling effect of the condensers of the dehydrogenation tower 14 and the decarbonization tower 13.

[0036] The above are only the preferred embodiments of the present utility model and are not used to limit the present utility model. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the technical principle of the present utility model, several improvements and modifications can still be made, and these improvements and modifications should also be regarded as the protection scope of the present utility model.

Claims

1. A pre-cooling system for methanol synthesis gas, characterized in that, Including: A liquid nitrogen storage tank (1), a vaporizer (2), a compressor (3), a filter (11), a precooler (12), a first stop valve (17), a second stop valve (18), a third stop valve (19), a fourth stop valve (20), a fifth stop valve (21), a vent valve (22), a gas recovery unit (23), a temperature sensor (24), and a controller. The outlet of the liquid nitrogen storage tank (1) is connected to the inlet of the vaporizer (2) through a connecting pipe. The outlet of the vaporizer (2) is connected to the first inlet of the compressor (3) through a connecting pipe. The outlet of the compressor (3) is connected to one end of a first main pipe (4). The other end of the first main pipe (4) is connected to one end of a first branch pipe (5) and a second branch pipe (6). The other end of the first branch pipe (5) is connected to the inlet of the filter (11). The other end of the second branch pipe (6) is connected to the inlet of the precooler (12). The outlet of the filter (11) is connected to one end of a second main pipe (10) through a third branch pipe (7). The outlet of the precooler (12) is connected to one end of the second main pipe (10) through a fourth branch pipe (8). The other end of the second main pipe (10) is connected to the inlets of a decarbonization tower (13) and a dehydrogenation tower (14). The first outlets of the decarbonization tower (13) and the dehydrogenation tower (14) are both connected to the second inlet of the compressor (3) through connecting pipes. The second outlet of the decarbonization tower (13) is connected to the inlet of a gas compression device (15) through a connecting pipe. The second outlet of the dehydrogenation tower (14) is connected to the first inlet of a methanol synthesis device (16) through a connecting pipe. The outlet of the gas compression device (15) is connected to the second inlet of the methanol synthesis device (16). The gas recovery unit (23) is connected to the second branch pipe (6) through a fifth branch pipe (9). The temperature sensor (24) is connected to the second main pipe (10); The first stop valve (17) is connected to the first branch pipe (5). The second stop valve (18) is connected to the third branch pipe (7). The third stop valve (19) is connected to the second branch pipe (6). The fourth stop valve (20) is connected to the fourth branch pipe (8). The fifth stop valve (21) is connected to the connecting pipe between the first outlets of the decarbonization tower (13) and the dehydrogenation tower (14) and the second inlet of the compressor (3). The vent valve (22) is connected to the fifth branch pipe (9); The first stop valve (17), the second stop valve (18), the third stop valve (19), the fourth stop valve (20), the fifth stop valve (21), the vent valve (22), and the temperature sensor (24) are all electrically connected to the controller.

2. The pre-cooling system of a methanol synthesis gas according to claim 1, characterized in that, Also including: Four pressure gauges (25), two of which are respectively connected to the inlet and outlet of the filter (11), and the other two pressure gauges (25) are respectively connected to the inlet and outlet of the precooler (12). All four pressure gauges (25) are electrically connected to the controller.

3. The pre-cooling system for methanol synthesis gas according to claim 1 or 2, characterized in that, Further included is: A flow control valve (26), which is connected to the connecting pipeline between the liquid nitrogen storage tank (1) and the vaporizer (2), and the flow control valve (26) is electrically connected to the controller.

4. A pre-cooling system for methanol synthesis gas according to claim 1, characterized in that, Further included is: A sixth stop valve (27), which is connected to the connecting pipeline between the outlet of the vaporizer (2) and the first inlet of the compressor (3).

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