Solvent circulating system of natural gas purification and desulfurization unit

Abstract

The utility model relates to the technical field of natural gas purification, in particular to a solvent circulating system of a natural gas purification and desulfurization unit, which comprises an absorption tower, a flash tank and a regeneration tower which are sequentially communicated through pipelines, the bottom of the regeneration tower is connected with a circulating pipe, the circulating pipe is communicated with the absorption tower, and the flash tank is communicated with the regeneration tower. A circulating pipe is arranged in the regeneration tower, a circulating pump and a booster pump are arranged on the circulating pipe, the booster pump is arranged close to the regeneration tower, the circulating pump is arranged close to the absorption tower, and a buffer tank is arranged between the circulating pump and the booster pump. According to the solvent circulating system of the natural gas purification and desulfurization unit, the buffer tank is arranged between the booster pump close to the regeneration tower and the circulating pump close to the absorption tower, and non-condensable gas can be finally discharged into the buffer tank even if exhaust is insufficient when the booster pump is switched, so that normal operation of the circulating pump is ensured.

Description

Technical Field

[0001] The utility model relates to the technical field of natural gas purification, in particular to a solvent circulation system for a natural gas purification and desulfurization unit. Background Art

[0002] The typical absorption amine liquid cycle of the alcohol amine method is as follows: the high-pressure rich amine liquid that has absorbed the acidic components flows out of the absorption tower and enters the flash tank to evaporate the hydrocarbons carried by the gas. After flash evaporation, the rich amine liquid enters the regeneration tower. A reboiler is set at the bottom of the regeneration tower. After regeneration, the high-temperature lean amine liquid is pressurized by the booster pump and then enters the absorption tower for recycling through the circulation pump.

[0003] At present, in the amine process, the booster pump and the circulation pump are directly connected, that is, the inlet pressure of the circulation pump is the outlet pressure of the booster pump. When the booster pump is switched, if the standby pump is not completely primed and vented, it is very easy to cause the circulation pump flow to decrease and the pump to be interlocked and stopped.

[0004] Therefore, a technical solution is currently needed to solve the technical problem that during the natural gas desulfurization process, the booster pump draws the lean amine liquid from the regeneration tower and directly introduces it into the absorption tower through the circulating pump, and the inlet pressure of the circulating pump is the outlet pressure of the booster pump, which easily affects the normal operation of the circulating pump when the booster pump is switched. Utility Model Content

[0005] The utility model aims to overcome the technical problem that in the process of natural gas desulfurization, the booster pump draws out the lean amine liquid in the regeneration tower and then directly introduces it into the absorption tower through the circulation pump, the inlet pressure of the circulation pump is the outlet pressure of the booster pump, and the normal operation of the circulation pump is easily affected when the booster pump is switched, and provides a natural gas desulfurization unit solvent circulation system.

[0006] The utility model provides a solvent circulation system for a natural gas purification and desulfurization unit, comprising an absorption tower, a flash tank and a regeneration tower, wherein the absorption tower, the flash tank and the regeneration tower are connected in sequence through pipelines, a circulation pipe is connected to the bottom of the regeneration tower, the circulation pipe is connected to the absorption tower, a circulation pump and a booster pump are arranged on the circulation pipe, the booster pump is arranged close to the regeneration tower, the circulation pump is arranged close to the absorption tower, and a buffer tank is arranged between the circulation pump and the booster pump.

[0007] The utility model discloses a solvent circulation system for a natural gas purification and desulfurization unit. When in use, the sulfur-containing natural gas enters an absorption tower and contacts with a lean amine liquid. The lean amine liquid that absorbs the sulfur-containing natural gas forms a rich amine liquid and enters a flash tank. The hydrocarbons carried by the rich amine liquid are evaporated in the flash tank. The flash steam is recovered through an absorption device connected to the flash tank. The rich amine liquid flowing out of the flash tank enters a regeneration tower. The released acidic components are drawn out from the top of the tower. The lean amine liquid formed at the bottom of the regeneration tower flows to a circulation pump through a booster pump and is introduced into the absorption tower again through the circulation pump. The amine liquid circulates back and forth in sequence. The application sets a buffer tank between the booster pump and the circulation pump. Even if the exhaust is insufficient when the booster pump is switched, the non-condensable gas is finally discharged into the buffer tank, thereby avoiding affecting the operation of the circulation pump.

[0008] Preferably, a heat exchanger is connected between the flash tank and the regeneration tower, the circulation pipe is in communication with the heat exchanger, and the heat exchanger is used for heat exchange between the rich amine liquid drawn out of the flash tank and the lean amine liquid drawn out of the regeneration tower.

[0009] A heat exchanger is arranged beside the regeneration tower. Heat exchange tubes are arranged in the heat exchanger. Rich amine liquid flows in the inner cavity of the heat exchanger and then enters the regeneration tower. Lean amine liquid flows in the heat exchange tubes and then flows to the absorption tower. The lean amine liquid and the rich amine liquid exchange heat in the heat exchanger. On the one hand, it preheats the rich amine liquid entering the regeneration tower, and on the other hand, it cools the lean amine liquid entering the absorption tower. At the same time, no external energy needs to be consumed for heat exchange, which saves costs.

[0010] Preferably, a cooler is connected between the buffer tank and the heat exchanger.

[0011] The cooler can reduce the temperature of the lean amine liquid drawn out from the regeneration tower, so that the lean amine liquid has a better absorption capacity for the acidic components of natural gas after entering the absorption tower.

[0012] Preferably, a filter is connected between the cooler and the buffer tank.

[0013] The filter can filter impurities in the amine solution and protect the pipelines and equipment of the desulfurization unit.

[0014] Preferably, a hydraulic turbine is connected between the absorption tower and the flash tank, and the hydraulic turbine is used to drive the circulation pump. The lean amine liquid in the absorption tower absorbs the acidic components in the natural gas to form a rich amine liquid, which then enters the flash tank. A hydraulic turbine is arranged between the flash tank and the absorption tower to recover the liquid energy in the rich amine liquid, which not only reduces the pressure of the rich amine liquid, but also converts the absorption capacity into kinetic energy to drive the circulation pump, thereby reducing the energy consumption of the production process.

[0015] Preferably, the buffer tank is connected to the flash tank through a pipeline, and a solvent pump is connected between the buffer tank and the flash tank.

[0016] The hydrocarbons flashed out from the flash tank carry acidic components. A portion of lean amine liquid is drawn out from the buffer tank and contacts with hydrocarbons containing acidic components in the flash steam absorption tower at the top of the flash tank to absorb the acidic components in the recovered hydrocarbons.

[0017] Preferably, the top of the regeneration tower is connected to a reflux tank, an air cooler is connected between the reflux tank and the regeneration tower, the bottom of the reflux tank is connected to a liquid return pipe, and the liquid return pipe is in communication with the regeneration tower.

[0018] The acidic components released from the rich amine liquid in the regeneration tower are drawn out from the top of the tower into the acid gas cooling and liquid separation system, and are connected to the top of the regeneration tower through a reflux tank. The volatilized acidic water is transported back to the regeneration tower through the return pipe in the reflux tank. The regenerated lean amine liquid flowing out of the bottom of the regeneration tower enters the booster pump and finally enters the absorption tower for recycling.

[0019] Preferably, the buffer tank is connected to a nitrogen charging pipe and a pressure relief pipe, and the nitrogen charging pipe and the pressure relief pipe are respectively provided with valves for controlling the on-off of the gas.

[0020] To ensure safe operation, the amine liquid in the buffer tank needs to avoid mixing with air and other impurity gases. Nitrogen is transported to the buffer tank by setting up a nitrogen charging pipe. The buffer tank is sealed with nitrogen. When nitrogen is partially dissolved in water under high pressure conditions or other losses occur, nitrogen can be replenished into the buffer tank through the nitrogen charging pipe. At the same time, when the pressure in the buffer tank increases, the buffer tank can be depressurized through the pressure relief pipe.

[0021] Preferably, the minimum reflux line of the circulation pump is connected to the buffer tank.

[0022] When the circulation pump is switched, when the standby circulation pump is started, the booster pump flow rate will increase by about 80-100t / h, which may easily cause the booster pump filter to be blocked and the outlet pressure to be greatly reduced, endangering the smooth operation of the device. The minimum return line of the circulation pump is connected to the buffer tank to avoid the risk of sudden increase in flow rate causing filter blockage and temperature drop in the regeneration tower.

[0023] Compared with the prior art, the utility model has the following beneficial effects:

[0024] 1. The utility model provides a solvent circulation system for a natural gas purification and desulfurization unit. By setting a buffer tank between a booster pump near a regeneration tower and a circulation pump near an absorption tower, even if the booster pump is not fully exhausted when switching, the non-condensable gas will eventually be discharged into the buffer tank, thereby ensuring the normal operation of the circulation pump;

[0025] 2. The lean amine liquid absorbs the acidic components in the sour natural gas to form rich amine liquid. The rich amine liquid is flashed to remove hydrocarbons, and then the acidic components are removed through the regeneration tower to form lean amine liquid. The lean amine liquid is sent to the absorption tower through the circulation pipe for secondary utilization, realizing the recycling of solvents in the desulfurization process and reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of a solvent circulation system for a natural gas purification and desulfurization unit of the utility model.

[0027] Markings in the figure:

[0028] 1-absorption tower, 2-flash tank, 3-regeneration tower, 301-reboiler, 4-circulation pipe, 5-boosting pump, 6-circulation pump, 601-minimum reflux line, 7-buffer tank, 701-nitrogen charging pipe, 702-pressure relief pipe, 8-heat exchanger, 9-cooler, 901-lean liquid cooler, 902-solvent aftercooler, 10-filter, 11-hydraulic turbine, 12-solvent pump, 13-reflux tank, 14-air cooler, 15-return liquid pipe, 16-reflux pump. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with specific embodiments. However, this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

[0030] Unless otherwise specified, in the description of the specific embodiments of the present utility model, the expression terms indicating the orientation or position relationship such as "upper", "lower", "left", "right", "center", "inside", "outside", etc. are all based on the expression of the orientation or position relationship shown in the drawings, or the orientation or position relationship when the product / equipment / device of the utility model is usually used. These terms of orientation or position relationship are only for the convenience of describing the scheme of the utility model or simplifying the description in the specific embodiments, so that technicians can quickly understand the scheme, rather than indicating or implying that a specific device / component / element must have a specific orientation, or be constructed and operated in a specific position relationship, and therefore cannot be understood as a limitation on the present utility model.

[0031] In addition, if the terms "horizontal", "vertical", "overhanging", "parallel" and the like appear, it does not mean that the corresponding devices / components / elements are required to be absolutely horizontal or vertical or overhanging or parallel, but may be slightly tilted or have deviations. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but may be slightly tilted. Alternatively, it can be simplified to mean that the corresponding devices / components / elements are set in directions such as "horizontal", "vertical", "overhanging", "parallel", etc., and can have an error / deviation of ±10% relative to the corresponding direction setting, more preferably an error / deviation within ±8%, more preferably an error / deviation within ±6%, more preferably an error / deviation within ±5%, and more preferably an error / deviation within ±4%. As long as the corresponding devices / components / elements are within the error / deviation range, they can still achieve their functions in the solution of the utility model.

[0032] In addition, the expressions “first”, “second”, “third”, etc., which appear in the terms, are merely used to distinguish the description of the same or similar components and should not be understood as emphasizing or implying the relative importance of specific components.

[0033] In addition, in the description of the embodiments of the present invention, "several", "multiple" and "a number" represent at least 2. It can be any number such as 2, 3, 4, 5, 6, 7, 8, 9, and even more than 9.

[0034] In addition, in the description of the technical solution of the utility model, unless otherwise clearly specified / defined / restricted, the terms "set", "install", "connect", "connected", "provided with", "laid", and "arranged" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection, and can be welding, riveting, bolting, threading, and other commonly used connection means in the field. This connection can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection, or an indirect connection through an intermediate medium, and it can be the internal communication of two components.

[0035] Example 1

[0036] like Figure 1As shown, the present embodiment is a solvent circulation system for a natural gas purification and desulfurization unit, comprising an absorption tower 1, a flash tank 2 and a regeneration tower 3, wherein a flash steam absorption tower is arranged on the top of the flash tank 2, and a reboiler 301 is arranged at the bottom of the regeneration tower 3, the absorption tower 1, the flash tank 2 and the regeneration tower 3 are connected in sequence through pipelines, a circulation pipe 4 is connected to the bottom of the regeneration tower 3, the circulation pipe 4 is connected to the absorption tower 1, a circulation pump 6 and a booster pump 5 are arranged on the circulation pipe 4, the booster pump 5 is arranged close to the regeneration tower 3, the circulation pump 6 is arranged close to the absorption tower 1, a buffer tank 7 is arranged between the circulation pump 6 and the booster pump 5, and a filter 10 is connected between the buffer tank 7 and the booster pump 5.

[0037] When in use, the sour natural gas enters the absorption tower 1 and contacts with the lean amine liquid. The lean amine liquid that absorbs the sour natural gas forms a rich amine liquid and enters the flash tank 2. The hydrocarbons it carries are evaporated in the flash tank 2. The flash steam is recovered through the flash steam absorption tower connected to the flash tank 2. The rich amine liquid flowing out of the flash tank 2 enters the regeneration tower 3. The released acidic components are drawn out from the top of the regeneration tower 3. The lean amine liquid formed at the bottom of the regeneration tower 3 flows to the circulation pump 6 through the booster pump 5, and is reintroduced into the absorption tower 1 through the circulation pump 6. The amine liquid circulates back and forth in sequence. The present application sets a buffer tank 7 between the booster pump 5 and the circulation pump 6. Even if the exhaust is insufficient when the booster pump 5 is switched, the non-condensable gas is finally discharged into the buffer tank 7 to avoid affecting the operation of the circulation pump 6.

[0038] In an optional embodiment, a hydraulic turbine 11 is connected between the absorption tower 1 and the flash tank 2. The hydraulic turbine 11 is used to drive the circulation pump 6. The lean amine liquid in the absorption tower 1 absorbs the acidic components in the natural gas to form a rich amine liquid, which then enters the flash tank 2. The hydraulic turbine 11 is arranged between the flash tank 2 and the absorption tower 1 to recover the liquid energy in the rich amine liquid, which not only reduces the pressure of the rich amine liquid, but also converts the absorption capacity into kinetic energy for driving the circulation pump 6, thereby reducing the energy consumption of the production process.

[0039] In an optional embodiment, the buffer tank 7 is connected to a nitrogen charging pipe 701 and a pressure relief pipe 702, and the nitrogen charging pipe 701 and the pressure relief pipe 702 are respectively provided with valves for controlling the on-off of the gas. To ensure safe operation, air and other impurity gases need to be avoided from mixing into the buffer 7. Nitrogen is transported into the buffer tank 7 by providing a nitrogen charging pipe 701, and the buffer tank 7 is sealed by nitrogen. When nitrogen is partially dissolved in water under high pressure conditions or other losses occur, nitrogen can be supplemented into the buffer tank 7 through the nitrogen charging pipe 701. At the same time, when the pressure in the buffer tank 7 increases, the buffer tank 7 can be depressurized through the pressure relief pipe 702.

[0040] Example 2

[0041] like Figure 1As shown, in this embodiment, the difference from Embodiment 1 is that a heat exchanger 8 is connected between the flash tank 2 and the regeneration tower 3, the circulation pipe 4 is connected to the heat exchanger 8, and the heat exchanger 8 is used for heat exchange between the rich amine liquid drawn out of the flash tank 2 and the lean amine liquid drawn out of the regeneration tower 3.

[0042] In this embodiment, a heat exchanger 8 is arranged next to the regeneration tower 3, and a heat exchange tube is arranged in the heat exchanger 8. The rich amine liquid flows in the inner cavity of the heat exchanger and then enters the regeneration tower 3. The lean amine liquid flows in the heat exchange tube and then flows to the absorption tower 1. The lean amine liquid and the rich amine liquid exchange heat in the heat exchanger. On the one hand, it preheats the rich amine liquid entering the regeneration tower 3, and on the other hand, it cools the lean amine liquid entering the absorption tower 1. At the same time, there is no need to consume external energy for heat exchange, which saves costs.

[0043] Furthermore, a cooler 9 is arranged between the buffer tank 7 and the heat exchanger 8, and a filter 10 is arranged between the cooler 9 and the buffer tank 7. The cooler 9 includes a lean liquid cooler 901 and a solvent after-cooler 902. The lean liquid cooler 901 and the solvent after-cooler 902 are connected in sequence along the direction from the booster pump 5 to the circulation pump 6. The cooler 9 can reduce the temperature of the lean amine liquid drawn out from the regeneration tower 3, so that the lean amine liquid has a better absorption capacity for the acidic components of natural gas after entering the absorption tower 1.

[0044] Example 3

[0045] like Figure 1 As shown, the difference between this embodiment and Embodiment 1 is that the buffer tank 7 is connected to the flash tank 2 through a pipeline, and a solvent pump 12 is connected between the buffer tank 7 and the flash tank 2.

[0046] In this embodiment, the hydrocarbons flashed out from the flash tank 2 carry acidic components, and a portion of the lean amine liquid is drawn out from the buffer tank 7 and contacts with the hydrocarbons containing acidic components in the flash steam absorption tower at the top of the flash tank 2 to absorb the acidic components in the recovered hydrocarbons.

[0047] Example 4

[0048] like Figure 1 As shown, in this embodiment, the difference from Embodiment 1 is that a reflux tank 13 is connected to the top of the regeneration tower 3, an air cooler 14 is connected between the reflux tank 13 and the regeneration tower 3, a liquid return pipe 15 is connected to the bottom of the reflux tank 13, the liquid return pipe 15 is communicated with the regeneration tower 3, and a reflux pump 16 is connected between the liquid return pipe 15 and the regeneration tower 3.

[0049] In this embodiment, the acidic components released from the rich amine liquid in the regeneration tower 3 are drawn out from the top of the tower into the acid gas cooling and liquid separation system, and are connected to the top of the regeneration tower 3 through the reflux tank 13. The volatilized water vapor is liquefied in the reflux tank 3 and then transported back to the regeneration tower 3 through the return liquid pipe to reduce the loss of the lean amine liquid.

[0050] Example 5

[0051] like Figure 1 As shown, in this embodiment, the difference from Embodiment 1 is that the minimum reflux line 601 of the circulation pump 6 is connected to the buffer tank 7 .

[0052] In this embodiment, when the circulation pump 6 is switched, when the standby circulation pump 6 is started, the flow rate of the boosting pump 5 will increase by about 80-100 t / h, which may easily cause the filter screen of the boosting pump 5 to be blocked and the outlet pressure to be greatly reduced, endangering the smooth operation of the device. The minimum return line 601 of the circulation pump 6 is connected to the buffer tank 7 to avoid the risk of sudden increase in flow rate causing blockage of the filter screen and a drop in the temperature of the regeneration tower 3.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A solvent circulation system for a natural gas purification and desulfurization unit, characterized in that: The invention comprises an absorption tower (1), a flash tank (2) and a regeneration tower (3), wherein the absorption tower (1), the flash tank (2) and the regeneration tower (3) are connected in sequence through pipelines, a circulation pipe (4) is connected to the bottom of the regeneration tower (3), the circulation pipe (4) is connected to the absorption tower (1), a circulation pump (6) and a booster pump (5) are provided on the circulation pipe (4), the booster pump (5) is arranged close to the regeneration tower (3), the circulation pump (6) is arranged close to the absorption tower (1), and a buffer tank (7) is provided between the circulation pump (6) and the booster pump (5).

2. A natural gas purification and desulfurization unit solvent circulation system according to claim 1, characterized in that: A heat exchanger (8) is connected between the flash tank (2) and the regeneration tower (3), and the circulation pipe (4) is in communication with the heat exchanger (8). The heat exchanger (8) is used for heat exchange between the rich amine liquid drawn out of the flash tank (2) and the lean amine liquid drawn out of the regeneration tower (3).

3. A natural gas purification and desulfurization unit solvent circulation system according to claim 2, characterized in that: A cooler (9) is connected between the buffer tank (7) and the heat exchanger (8).

4. A natural gas purification and desulfurization unit solvent circulation system according to claim 3, characterized in that: A filter (10) is connected between the cooler (9) and the buffer tank (7).

5. A natural gas purification and desulfurization unit solvent circulation system according to claim 1, characterized in that: A hydraulic turbine (11) is connected between the absorption tower (1) and the flash tank (2), and the hydraulic turbine (11) is used to drive the circulation pump (6).

6. A natural gas purification and desulfurization unit solvent circulation system according to claim 1, characterized in that: The buffer tank (7) is connected to the flash tank (2) via a pipeline, and a solvent pump (12) is connected between the buffer tank (7) and the flash tank (2).

7. A natural gas purification and desulfurization unit solvent circulation system according to claim 1, characterized in that: The top of the regeneration tower (3) is connected to a reflux tank (13), an air cooler (14) is connected between the reflux tank (13) and the regeneration tower (3), the bottom of the reflux tank (13) is connected to a liquid return pipe (15), and the liquid return pipe (15) is in communication with the regeneration tower (3).

8. A natural gas purification and desulfurization unit solvent circulation system according to claim 1, characterized in that: The buffer tank (7) is connected to a nitrogen pressure charging pipe (701) and a pressure relief pipe (702), and the nitrogen pressure charging pipe (701) and the pressure relief pipe (702) are respectively provided with valves for controlling the on-off of gas.

9. A natural gas purification and desulfurization unit solvent circulation system according to claim 1, characterized in that: The minimum return line (601) of the circulation pump (6) is in communication with the buffer tank (7).

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