Rectification tail gas separation and recovery system

Abstract

The utility model relates to the technical field of tail gas separation and recovery, in particular to a rectification tail gas separation and recovery system. Comprising a rectification tail gas inlet pipeline, a first-stage cooler, a second-stage cooler, a pre-tower reflux tank washing tower and a torch pipe network, the first-stage cooler is connected with the rectification tail gas inlet pipeline containing methanol steam, and the first-stage cooler and the second-stage cooler are connected through a first-stage conveying pipeline containing non-condensable gas; the rectification tail gas recovery pipeline is additionally arranged, the liquid-sealed pipeline is dredged under the condition that the methanol synthesis production device is not stopped, and the rectification tail gas inlet valve can be opened after dredging is completed, so that the first-stage cooler and the second-stage cooler are continuously put into use, and the problem of liquid sealing of the pipeline caused by conveyed non-condensable gas is effectively relieved; economic losses caused by equipment shutdown are avoided, and economic benefits are improved.

Description

Technical Field

[0001] This utility model relates to the field of distillation tail gas separation and recovery technology, specifically to a distillation tail gas separation and recovery system. Background Technology

[0002] In the operation of chemical production plants, the gas exiting the top of the distillation pre-tower is condensed and cooled in a cooler. Most of the methanol vapor condenses and enters the pre-tower reflux tank for recovery, while a small portion of the methanol-containing non-condensable gas is sent to a scrubber. After being washed with water, the non-condensable gas is sent to the flare network for combustion. However, in the current technology, due to the excessive length of the pipelines during the non-condensable gas transportation process, some of the non-condensable gas condenses within the pipelines over a long period of time, easily causing liquid accumulation and forming a liquid seal. This leads to the inability of the primary and secondary coolers to function properly, resulting in untimely discharge of non-condensable gas. Furthermore, when clearing the pipelines, the methanol synthesis production equipment needs to be shut down, which affects the methanol synthesis process and causes certain economic losses. Utility Model Content

[0003] This invention addresses the shortcomings of existing technologies by providing a distillation tail gas separation and recovery system that can unclog pipelines without affecting non-condensable gas emissions and ensuring uninterrupted methanol synthesis.

[0004] To achieve the above technical objectives, this utility model proposes the following technical solution: a distillation tail gas separation and recovery system, comprising a distillation tail gas inlet pipeline, a primary cooler, a secondary cooler, a pre-tower reflux tank scrubbing tower, and a flare network. The primary cooler is connected to the distillation tail gas inlet pipeline containing methanol vapor. The primary cooler and the secondary cooler are connected by a primary conveying pipeline containing non-condensable gases. The methanol vapor condensed from the primary and secondary coolers is connected to the pre-tower reflux tank through the primary and secondary recovery pipelines, respectively. The inlet end of the scrubbing tower is connected to an inlet pipeline. The inlet pipeline is connected to the non-condensable gas outlet end of the secondary cooler and the distillation tail gas inlet pipeline through the secondary conveying pipeline and the distillation tail gas recovery pipeline, respectively. The non-condensable gas outlet end of the scrubbing tower is connected to the inlet end of the flare network through an exhaust pipeline.

[0005] Furthermore, the scrubbing tower includes a tower body, with liquid at the bottom of the tower body. An air distributor connected to the air inlet pipeline is installed in the liquid. At least one packing layer is installed in the tower body and above the liquid. A water distributor is installed on top of the packing layer. The water distributor is connected to the water outlet of the tower body through a water spray pipe. A circulation pump is installed on the water spray pipe. A demisting layer is installed in the tower body and above the water distributor. The air outlet at the top of the tower body is connected to the flare network through an exhaust pipeline.

[0006] Furthermore, a drain pipe is provided at the bottom of the tower body, and a drain valve is provided on the drain pipe.

[0007] Furthermore, the distillation tail gas inlet pipeline is equipped with a distillation tail gas inlet valve one on the side near the first-stage cooler, the distillation tail gas recovery pipeline is equipped with a distillation tail gas inlet valve two and a distillation tail gas outlet valve, and the first-stage conveying pipeline, the second-stage conveying pipeline and the exhaust pipeline are all equipped with non-condensable gas inlet valves and non-condensable gas outlet valves.

[0008] Furthermore, the primary and secondary recovery pipelines are respectively equipped with a first drain valve and a second drain valve.

[0009] Compared with the prior art, the beneficial effects of this utility model are as follows: By adding a distillation tail gas recovery pipeline, the condensation recovery is cut off while the methanol synthesis production unit is running continuously. The liquid-sealed pipeline is cleared, and after clearing, the distillation tail gas inlet valve can be opened, allowing the primary and secondary coolers to continue to be used. This effectively alleviates the problem of liquid sealing caused by the transported non-condensable gas in the pipeline, avoids economic losses caused by equipment downtime, and improves economic efficiency. The gas distributor can evenly distribute the non-condensable gas and methanol vapor in the distillation tail gas in the liquid, increasing the contact area with the liquid, improving the purification effect, and reducing the methanol vapor content in the distillation tail gas. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the overall structure of this utility model;

[0011] Figure 2 This is a schematic diagram of the structure of the washing tower of this utility model.

[0012] In the diagram, 1. Distillation tail gas inlet pipeline; 2. Primary cooler; 3. Secondary cooler; 4. Tower reflux trough; 5. Scrubber; 51. Tower body; 52. Liquid; 53. Gas distributor; 54. Packing layer; 55. Water distributor; 56. Water spray pipe; 57. Circulation pump; 58. Demisting layer; 59. Sewage pipe; 510. Sewage valve; 6. Flare network; 7. Primary conveying pipeline; 8. Primary recovery pipeline; 9. Secondary recovery pipeline; 10. Inlet pipeline; 11. Secondary conveying pipeline; 12. Distillation tail gas recovery pipeline; 13. Exhaust pipeline; 14. Distillation tail gas inlet valve one; 15. Distillation tail gas inlet valve two; 16. Distillation tail gas outlet valve; 17. Non-condensable gas inlet valve; 18. Non-condensable gas outlet valve; 19. First drain double valve; 20. Second drain double valve. Detailed Implementation

[0013] The following are specific embodiments of the present invention, and the technical solution of the present invention will be further described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0014] This utility model provides a distillation tail gas separation and recovery system, including a distillation tail gas inlet pipeline 1, a primary cooler 2, a secondary cooler 3, a pre-tower reflux tank 4, a scrubbing tower 5, and a flare network 6. The primary cooler 2 is connected to the distillation tail gas inlet pipeline 1 containing methanol vapor. The primary cooler 2 and the secondary cooler 3 are connected by a primary conveying pipeline 7 containing non-condensable gases. The methanol vapor condensed from the primary cooler 2 and the secondary cooler 3 is connected to the pre-tower reflux tank 4 through a primary recovery pipeline 8 and a secondary recovery pipeline 9, respectively. The inlet end of the scrubbing tower 5 is connected to an inlet pipeline 10. The inlet pipeline 10 is connected to the non-condensable gas outlet end of the secondary cooler 3 and the distillation tail gas inlet pipeline 1 through a secondary conveying pipeline 11 and a distillation tail gas recovery pipeline 12, respectively. The non-condensable gas outlet end of the scrubbing tower 5 is connected to the inlet end of the flare network 6 through an exhaust pipeline 13.

[0015] like Figure 1 As shown, under normal operating conditions without pipeline blockage, the gas exiting the top of the distillation pre-tower enters the primary cooler 2 and secondary cooler 3 sequentially from the distillation tail gas inlet pipeline 1 for cooling. Methanol vapor undergoes two stages of cooling in the primary cooler 2 and secondary cooler 3, which improves the cooling effect. The condensed vapor enters the pre-tower reflux tank 4 from the primary recovery pipeline 8 and secondary recovery pipeline 9 for recovery. After condensation, a small portion of the non-condensable gas containing methanol enters the scrubbing tower 5 through the secondary conveying pipeline 11 for scrubbing to remove pollutants from the tail gas. The scrubbed non-condensable gas then enters the flare network 6 through the exhaust pipeline 13 for combustion, preventing direct emission of non-condensable gas into the atmosphere and causing environmental pollution. When the primary coolant 2 and the secondary cooler 3 become blocked, the gas coming out of the top of the distillation pre-tower will directly enter the scrubbing tower 5 for washing along the distillation tail gas recovery pipeline 12. The distillation tail gas containing methanol vapor will come into contact with the liquid in the scrubbing tower, which will dissolve the methanol vapor in the liquid and remove the pollutants in the distillation tail gas. The non-condensable gas discharged after washing will be transported to the flare network 6 for combustion. This utility model cuts off the primary cooler 2 and the secondary cooler 3 by setting the distillation tail gas recovery pipeline 12, and performs pipeline unblocking treatment without stopping the operation. After unblocking, the primary cooler 2 and the secondary cooler 3 can be put back into use, which effectively alleviates the problem of pipeline liquid seal caused by the non-condensable gas carrying liquid.

[0016] The scrubbing tower 5 includes a tower body 51, with a liquid 52 at the bottom of the tower body 51. A gas distributor 53 connected to the air inlet pipeline 10 is installed in the liquid 52. The gas distributor 53 allows the gas to fully contact the liquid 52, increasing the purification effect. Two sets of packing layers 54 are installed inside the tower body 51 and above the liquid 52. A water distributor 55 is installed on the top of the packing layers 54. The water distributor 55 is connected to the water outlet of the tower body 51 through a water spray pipe 56. A circulation pump 57 is installed on the water spray pipe 56. A demisting layer 58 is installed inside the tower body 51 and above the water distributor 55. The air outlet at the top of the tower body 51 is connected to the flare network 6 through an exhaust pipeline 13.

[0017] like Figure 1 and Figure 2 As shown, the non-condensable gas or distillation tail gas containing methanol vapor is evenly distributed in the liquid 52 through the gas distributor 53. The non-condensable gas or distillation tail gas containing methanol vapor is fully in contact with the liquid 52, which increases the purification effect and facilitates the dissolution of methanol vapor in the tail gas into the liquid 52. The circulation pump 57 draws the liquid 52 to the water distributor 55, which allows the liquid 52 to be recycled. The gas and liquid are fully in contact through the water distributor 55 and the packing layer 54. The demister layer 58 is used to remove water mist or droplets from the gas to ensure that the gas discharged into the flare network 6 does not contain liquid.

[0018] The bottom of the tower body 51 is provided with a drain pipe 59, and a drain valve 510 is provided on the drain pipe 59.

[0019] like Figure 2 As shown, the liquid 52 inside the tower body 51 can be periodically discharged through the drain pipe 59 and the drain valve 510. A liquid inlet is also installed on one side of the tower body 51 to facilitate the injection of new liquid into the tower body 51.

[0020] The distillation tail gas inlet pipeline 1 is equipped with a distillation tail gas inlet valve 14 on the side near the first-stage cooler 2. The distillation tail gas recovery pipeline 12 is equipped with a distillation tail gas inlet valve 15 and a distillation tail gas outlet valve 16. The first-stage conveying pipeline 7, the second-stage conveying pipeline 11, and the exhaust pipeline 13 are all equipped with a non-condensable gas inlet valve 17 and a non-condensable gas outlet valve 18.

[0021] like Figure 1As shown, the first distillation tail gas inlet valve 14 controls the entry of tail gas into the distillation tail gas inlet pipeline 1, the second distillation tail gas inlet valve 15 and the distillation tail gas outlet valve 16 control the closure of the distillation tail gas recovery pipeline 12, the non-condensable gas inlet valve 17 and the non-condensable gas outlet valve 18 on the primary conveying pipeline 7 control the closure of the primary conveying pipeline 7, the non-condensable gas inlet valve 17 and the non-condensable gas outlet valve 18 on the secondary conveying pipeline 11 control the closure of the secondary conveying pipeline 11, and the non-condensable gas inlet valve 17 and the non-condensable gas outlet valve 18 on the exhaust pipeline 13 control the closure of the exhaust pipeline 13. In this embodiment, the use of two valves on one pipeline can increase the safety and reliability of the pipeline, and at the same time facilitate maintenance and repair.

[0022] The primary recovery pipeline 8 and the secondary recovery pipeline 9 are respectively equipped with a first drain double valve 19 and a second drain double valve 20.

[0023] like Figure 1 As shown, the first drain valve 19 and the second drain valve 20 are used to discharge the condensate in the primary recovery pipeline 8 and the secondary recovery pipeline 9, respectively.

[0024] Operating principle: During normal operation, open the distillation tail gas inlet valve 14, non-condensable gas inlet valve 17, non-condensable gas outlet valve 18, first drain double valve 19, and second drain double valve 20. Close the distillation tail gas inlet valve 15 and distillation tail gas outlet valve 16. The gas exiting from the top of the distillation pre-tower enters the primary cooler 2 and secondary cooler 3 sequentially from the distillation tail gas inlet pipeline 1 for cooling. Methanol vapor undergoes two stages of cooling in the primary cooler 2 and secondary cooler 3. The condensed vapor enters the pre-tower reflux tank 4 from the primary recovery pipeline 8 and secondary recovery pipeline 9 for recovery. After condensation, a small portion of the non-condensable gas containing methanol enters the scrubbing tower 5 through the secondary conveying pipeline 11 for scrubbing to remove pollutants from the tail gas. The scrubbed non-condensable gas then enters the flare network 6 through the exhaust pipeline 13 for combustion.

[0025] When a liquid seal occurs in the pipeline, the distillation tail gas inlet valve 15, the distillation tail gas outlet valve 16, the non-condensable gas inlet valve 17 and the non-condensable gas outlet valve 18 on the exhaust pipeline 13 can be opened, while the distillation tail gas inlet valve 14 can be closed. At this time, the staff can clear the primary conveying pipeline 7, the secondary conveying pipeline 11, and the exhaust pipeline 13. Simultaneously, the gas exiting from the top of the distillation pre-tower will directly enter the scrubbing tower 5 along the distillation tail gas recovery pipeline 12 for washing. The distillation tail gas containing methanol vapor comes into contact with the liquid 52 in the scrubbing tower. The alcohol vapor dissolves in liquid 52, which can remove both methanol vapor and pollutants from the distillation tail gas. The non-condensable gas discharged after washing will be transported to the flare network 6 for combustion. After the dredging is completed, the distillation tail gas inlet valve 15 and the distillation tail gas outlet valve 16 can be closed, and the distillation tail gas inlet valve 14 can be opened to switch the distillation tail gas to the pipeline of the first-stage cooler 2 and the second-stage cooler 3. The pipeline dredging work of this utility model does not affect the emission of distillation tail gas, thus ensuring the normal operation of the methanol synthesis unit.

[0026] The specific embodiments described herein are merely illustrative examples illustrating the spirit of this utility model. Those skilled in the art to which this utility model pertains may make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the spirit of this utility model or exceeding the scope defined by the appended claims.

Claims

1. A distillation tail gas separation and recovery system, characterized in that: The system includes a distillation tail gas inlet pipeline (1), a primary cooler (2), a secondary cooler (3), a pre-tower reflux tank (4), a scrubbing tower (5), and a flare network (6). The primary cooler (2) is connected to the distillation tail gas inlet pipeline (1) containing methanol vapor. The primary cooler (2) and the secondary cooler (3) are connected by a primary delivery pipeline (7) containing non-condensable gases. The methanol vapor condensed from the primary cooler (2) and the secondary cooler (3) is respectively transported through... The primary recovery pipeline (8) and the secondary recovery pipeline (9) are connected to the pre-tower reflux tank (4). The inlet end of the scrubbing tower (5) is connected to the inlet pipeline (10). The inlet pipeline (10) is connected to the non-condensable gas outlet end of the secondary cooler (3) and the distillation tail gas inlet pipeline (1) through the secondary transport pipeline (11) and the distillation tail gas recovery pipeline (12), respectively. The non-condensable gas outlet end of the scrubbing tower (5) is connected to the inlet end of the flare network (6) through the exhaust pipeline (13).

2. The distillation tail gas separation and recovery system according to claim 1, characterized in that: The scrubbing tower (5) includes a tower body (51), a liquid (52) at the bottom of the tower body (51), an air distributor (53) connected to the air inlet pipeline (10) in the liquid (52), at least one packing layer (54) in the tower body (51) and above the liquid (52), a water distributor (55) at the top of the packing layer (54), the water distributor (55) is connected to the outlet of the tower body (51) through a water spray pipe (56), a circulating pump (57) is provided on the water spray pipe (56), a demisting layer (58) is provided in the tower body (51) and above the water distributor (55), and the air outlet at the top of the tower body (51) is connected to the flare network (6) through an exhaust pipeline (13).

3. The distillation tail gas separation and recovery system according to claim 2, characterized in that: The bottom of the tower body (51) is provided with a drain pipe (59), and a drain valve (510) is provided on the drain pipe (59).

4. The distillation tail gas separation and recovery system according to claim 1, characterized in that: The distillation tail gas inlet pipeline (1) is provided with a distillation tail gas inlet valve one (14) on the side near the first-stage cooler (2), and a distillation tail gas inlet valve two (15) and a distillation tail gas outlet valve (16) are provided on the distillation tail gas recovery pipeline (12). The first-stage conveying pipeline (7), the second-stage conveying pipeline (11) and the exhaust pipeline (13) are all provided with a non-condensable gas inlet valve (17) and a non-condensable gas outlet valve (18).

5. The distillation tail gas separation and recovery system according to claim 1, characterized in that: The primary recovery pipeline (8) and the secondary recovery pipeline (9) are respectively equipped with a first drain double valve (19) and a second drain double valve (20).

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