Low-energy-consumption process system for removing acid gas from amine liquid

Abstract

The invention relates to the field of chemical equipment, and discloses a low-energy-consumption process system for removing acid gas from amine liquid, which comprises an absorption tower, a first flash tank, a second flash tank, a reboiler, a cooler and a regeneration tower, the absorption tower, the first flash tank and the regeneration tower are circularly connected, and a turbine booster pump is arranged between a tower bottom rich solution pipeline of the absorption tower and a tower bottom barren solution pipeline of the regeneration tower; one end of the turbo-booster pump is provided with a chamber which is used for accommodating a turbine and is communicated with a tower bottom rich liquor pipeline, and the other end of the turbo-booster pump is provided with a pump side communicated with a tower bottom barren liquor pipeline; a tower top steam outlet pipeline of the regeneration tower is communicated with a second flash tank after passing through a cooler; a reflux pipeline of the second flash tank is communicated with a reflux inlet of the regeneration tower; the bottom of the regeneration tower is communicated with the reboiler through a kettle liquid pipeline, and a steam outlet of the reboiler is communicated with a steam inlet of the regeneration tower. The low-energy-consumption process system for removing acid gas from amine liquid can greatly reduce the energy consumption of the original system, and has remarkable economic benefits.

Description

Technical Field

[0001] The invention relates to the field of chemical equipment, and in particular to a low-energy consumption amine liquid acid gas removal process system. Background Art

[0002] Amine liquid is a general term for a class of organic alkaline solutions with weak alkalinity. It is mainly used in chemical industries such as petroleum, natural gas, coal chemical industry, and synthetic ammonia to adsorb and remove impurities such as hydrogen sulfide or carbon dioxide in raw gas. Alcohol amines are more common. The rich amine solution after absorbing acid gas is regenerated by heating and distillation. The regenerated lean amine solution is returned to the adsorption tower for recycling.

[0003] Methyldiethanolamine (MDEA) was first used in industry as a selective desulfurization solvent in the early 1980s. In practice, MDEA has become the fastest-growing deacidification process in recent years due to its significant energy-saving effects, mild corrosion, and the solvent is not easily degraded.

[0004] The advantages of methyldiethanolamine (MDEA) include: 1) 2 S has good selectivity; 2) The solution concentration is high, the acid gas load is large, and the circulation volume is small; 3) The regeneration energy consumption is low and the operating cost is low; 4) The lean solution is weakly corrosive, the vapor pressure is low, and the evaporation loss is small.

[0005] Conventional alcohol amine liquid acid gas removal system mainly includes absorption tower, pressure reducing valve, flash tank, lean / rich solution heat exchanger, regeneration tower, booster pump, reboiler and condenser, etc. The pressure reducing valve is installed on the rich liquid pipeline at the bottom of the absorption tower to reduce the pressure of the rich liquid to ensure that it meets the pressure of analysis in the regeneration tower. The use of this pressure reducing valve causes the pressure in the rich liquid to be wasted; the function of the booster pump is to return the lean amine liquid from the regeneration tower to the absorption tower to continue absorbing the acid component gas. The booster pump here needs to use a large head booster pump with high energy consumption.

[0006] At present, the main ways to reduce energy consumption in amine acid gas removal systems include:

[0007] 1) Optimize the configuration of energy-saving equipment

[0008] The most critical point in optimizing the energy-saving design of the amine liquid circulation system is to optimize the energy-saving performance of each functional equipment in the system. With the advancement of science and technology, the application scale of artificial intelligence technology in various production links is getting larger and larger. Relevant enterprises can closely combine relevant technologies with the optimization design of the steam system in the regeneration tower, thereby reducing the energy consumption of the deacidification device. For example, Dalian Petrochemical Research Institute has developed an amine liquid system optimization technology-high-efficiency jet tray based on the energy consumption of the natural gas deacidification device. Installing this device in the regeneration tower can effectively alleviate the foaming of the amine liquid in the tower and greatly improve the operating efficiency of the device. Data show that this type of technology can reduce the energy consumption of the deacidification amine liquid circulation device by 8% to 10%.

[0009] At present, most enterprises use the "air + water cooling" method in the cooling link of the regeneration tower. In this method, the cooling system cannot reasonably control the cooling energy consumption according to the different temperatures of the regeneration tower. To address this energy consumption defect, designers can install an air cooler at the top of the regeneration tower to effectively reduce the use of cooling water, that is, use a separate air cooling method to cool the acid and lean amine liquid at the top of the tower. Studies have shown that this method can reduce energy consumption by about 25%

[0010] 2) Optimize the overall design of the purification plant

[0011] According to the principle and characteristics of electric energy consumption, designers can minimize the length of wires connecting various devices in the deacidification system while ensuring line safety, and reasonably optimize the wire network to keep the lines as straight as possible, thereby effectively reducing reactive power losses during power transportation.

[0012] For example, the circuits of the pumps, heat exchangers, regeneration tower reboilers, air coolers and other devices in the deacidification amine liquid regeneration system that consume a lot of power during system operation should be redesigned, the wiring plan should be optimized, and the line loss should be reduced; at the same time, the substation in the purification plant should be located as centrally as possible among the key energy-consuming equipment groups, the cable line distances should be evenly distributed, and the thermal oil boiler should be placed as close to the purification unit as possible to achieve the goal of reducing the energy consumption of the amine liquid deacidification regeneration system. Summary of the invention

[0013] The purpose of the present invention is to overcome the problem of high energy consumption of the amine liquid acid gas removal system in the prior art and provide a low-energy consumption amine liquid acid gas removal process system. The low-energy consumption amine liquid acid gas removal process system can greatly reduce the energy consumption of the original system and has significant economic benefits.

[0014] In order to achieve the above-mentioned object, the present invention provides a low-energy consumption amine liquid acid gas removal process system, which includes an absorption tower, a first flash tank, a second flash tank, a reboiler, a cooler and a regeneration tower;

[0015] The absorption tower, the first flash tank and the regeneration tower are cyclically connected, and a turbocharger pump is provided between the rich liquid pipeline at the bottom of the absorption tower and the lean liquid pipeline at the bottom of the regeneration tower;

[0016] One end of the turbocharger pump is provided with a chamber for accommodating a turbine and communicating with the tower bottom rich liquid pipeline, and the other end is provided with a pump side communicating with the tower bottom lean liquid pipeline;

[0017] The tower top steam outlet pipeline of the regeneration tower is connected to the second flash tank after passing through the cooler, and the reflux pipeline of the second flash tank is connected to the reflux inlet of the regeneration tower;

[0018] The bottom of the regeneration tower is connected to the reboiler through a kettle liquid pipeline, and the steam outlet of the reboiler is connected to the steam inlet of the regeneration tower.

[0019] Preferably, the rich liquid outlet pipeline and the tower bottom lean liquid pipeline are connected via a heat exchanger.

[0020] Preferably, a front booster pump is provided on the front end of the tower bottom lean liquid pipeline located on the pump side.

[0021] Preferably, a pressure reducing valve is provided on the bottom lean liquid pipeline of the tower at the rear end on the pump side.

[0022] Preferably, the cooler is an air cooler or a water cooler.

[0023] Preferably, a top condenser is provided at the front end of the cooler.

[0024] Preferably, the low-energy amine liquid acid gas removal process system further comprises a compressor;

[0025] The compressor, the working medium condensation chamber of the reboiler and the working medium evaporation side of the tower top condenser are connected in a circular manner in sequence;

[0026] The tower top steam outlet pipeline is connected to the material condensation side of the tower top condenser, and the material condensation side is connected to the working medium evaporation side for heat exchange.

[0027] Preferably, an expansion valve is also provided on the working medium transmission pipeline between the reboiler and the tower top condenser.

[0028] Preferably, a separation tank is provided between the top condenser and the compressor.

[0029] Preferably, the compressor is a centrifugal compressor.

[0030] Through the above technical scheme, on the basis of the existing amine liquid deacidification process system, the present invention arranges a turbocharger pump between the lean liquid pipeline at the bottom of the tower and the rich liquid pipeline at the bottom of the tower, removes the existing pressure reducing valve and replaces it with a turbocharger pump, one end of the turbocharger pump is provided with a chamber for accommodating a turbine and communicating with the rich liquid pipeline at the bottom of the tower, and the other end is provided with a pump side communicating with the lean liquid pipeline at the bottom of the tower, therefore, the pressure in the original absorption tower pressure reducing valve can be recovered and converted into mechanical energy of the turbine, the rotation of the turbine can drive the pump blades in the pump side to rotate so as to pump the lean liquid in the lean liquid pipeline at the bottom of the tower into the absorption tower, the turbocharger pump does not require external energy input, and the pressure energy that can be increased is about 50-70% of the original booster pump, which can reduce the energy consumption of the original booster pump by 50-70%. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural schematic diagram of a preferred implementation of a low-energy amine liquid acid gas removal process system.

[0032] Description of Reference Numerals

[0033] 1-absorption tower; 2-pressure reducing valve; 3-pump side; 4-turbine; 5-front booster pump; 6-lean liquid pipeline at the bottom of the tower; 7-rich liquid pipeline at the bottom of the tower; 8-first flash tank; 9-heat exchanger; 10-rich liquid outlet pipeline; 11-kettle liquid pipeline; 12-reboiler; 13-steam pipeline; 14-regeneration tower; 15-expansion valve; 16-tower top steam outlet pipeline; 17-circulation pipeline; 18-cooler; 19-separation tank; 20-second flash tank; 21-compressor; 22-reflux pipeline; 23-tower top condenser. DETAILED DESCRIPTION

[0034] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0035] In the present invention, unless otherwise stated, directional words contained in terms such as "up, down, left, right, front, back, inside, outside" merely represent the orientation of the terms in normal usage, or are common names understood by those skilled in the art, and should not be regarded as limitations on the terms.

[0036] See also Figure 1The low-energy amine liquid acid removal process system shown in the figure comprises an absorption tower 1, a first flash tank 8, a second flash tank 20, a reboiler 12, a cooler 18 and a regeneration tower 14; the absorption tower 1, the first flash tank 8 and the regeneration tower 14 are cyclically connected, and a turbocharger pump is arranged between the bottom rich liquid pipeline 7 of the absorption tower 1 and the bottom lean liquid pipeline 6 of the regeneration tower 14; one end of the turbocharger pump is provided with a turbine 4 and connected to the bottom rich liquid pipeline 6 of the regeneration tower 14; The chamber is connected to the pipeline 7, and the other end is provided with a pump side 3 connected to the bottom lean liquid pipeline 6; the top steam outlet pipeline 16 of the regeneration tower 14 is connected to the second flash tank 20 after passing through the cooler 18, and the reflux pipeline 22 of the second flash tank 20 is connected to the reflux inlet of the regeneration tower 14; the bottom of the regeneration tower 14 is connected to the reboiler 12 through the kettle liquid pipeline 11, and the steam outlet of the reboiler 12 is connected to the steam inlet of the regeneration tower 14.

[0037] Among them, the bottom rich liquid pipeline 7 of the absorption tower 1 is connected to the inlet of the first flash tank 8, and the rich liquid outlet pipeline 10 of the first flash tank 8 is connected to the rich liquid inlet of the regeneration tower 14; the bottom lean liquid pipeline 6 of the regeneration tower 14 is connected to the lean liquid inlet of the absorption tower 1, and a turbocharger pump is arranged between the bottom lean liquid pipeline 6 and the bottom rich liquid pipeline 7.

[0038] Through the implementation of the above technical solution, on the basis of the existing amine liquid deacidification process system, a turbocharger pump is arranged between the tower bottom lean liquid pipeline 6 and the tower bottom rich liquid pipeline 7, the existing pressure reducing valve 2 is removed and replaced with a turbocharger pump, one end of the turbocharger pump is provided with a chamber accommodating a turbine 4 and communicating with the tower bottom rich liquid pipeline 7, and the other end is provided with a pump side 3 communicating with the tower bottom lean liquid pipeline 6, therefore, the pressure in the tower bottom rich liquid pressure reducing valve of the original absorption tower 1 can be recovered and converted into mechanical energy of the turbine 4, the turbine 4 rotates under the pressure of the rich liquid, and then the rotation of the turbine can drive the pump blades in the pump side 3 to rotate so as to pump the lean liquid in the tower bottom lean liquid pipeline 6 into the absorption tower 1, the turbocharger pump does not require external energy input, and the pressure energy that can be increased is about 50-70% of the original booster pump, which can reduce the energy consumption of the original booster pump by 50-70%, and in addition, the turbine 4 and the pump blades are coaxially connected, which can reduce the problem of difficult synchronization caused by the original multi-stage pump, or the problem of easy damage caused by the coupling connection.

[0039] In the present invention:

[0040] Absorption tower 1 is a place for gas-liquid mass transfer, where the acidic components are transferred into the alcohol amine liquid. Absorption tower 1 can be a packed tower or a plate tower. Currently, a floating valve tower is mostly used. The pressure and temperature are related to the type of raw gas.

[0041] The first flash tank 8 is used to analyze the hydrocarbons dissolved in the rich liquid as much as possible, and a horizontal tank is usually used to ensure sufficient flash area;

[0042] The regeneration tower 14, also called the analytical tower, is used to regenerate the alcohol-rich amine solution and restore the purification capacity of the solvent. It has the same tower type as the absorption tower 1;

[0043] The second flash tank 20 is used for condensing the gas from the top of the regeneration tower, analyzing and discharging the acidic gas, and returning the solution, which is mainly water, to the regeneration tower.

[0044] The reboiler 12 heats part of the acidic alcoholamine solution back to the tower. Its heat load includes the heat for heating the acidic alcoholamine solution to boiling point, the heat for decomposing the compounds generated by alcoholamine and acid gas, the heat for vaporizing the reflux liquid, the heat for heating the make-up water and the tower heat loss, and a 15%-20% safety margin is taken into account.

[0045] In this embodiment, the rich liquid outlet pipeline 10 is connected to the tower bottom lean liquid pipeline 6 via a heat exchanger 9. The heat exchanger 9 is provided so that the rich liquid in the rich liquid outlet pipeline 10 and the lean liquid in the tower bottom lean liquid pipeline 6 can exchange heat, cooling the lean liquid while increasing the temperature of the rich liquid. The heat exchanger 9 is mostly of shell and tube type, in which the rich liquid runs through the tube path.

[0046] In this embodiment, a pre-boost pump 5 is provided at the front end of the pump side 3 on the tower bottom lean liquid pipeline 6. The pre-boost pump 5 is provided as a supplement to the pressure of the turbocharger pump. When the head of the turbocharger pump is insufficient, the pre-boost pump 5 is started. At this time, the pre-boost pump 5 does not need to use a booster pump with a large head, but only needs to use a booster pump with a small head, which significantly reduces energy consumption.

[0047] In this embodiment, as a supplement to make the system more complete, a pressure reducing valve 2 is provided on the bottom lean liquid pipeline 6 at the rear end of the pump side 3. The pressure reducing valve 2 is provided here to assist in adjusting the pressure in the bottom lean liquid pipeline 6, so that the pressure in the bottom lean liquid pipeline 6 can be adjusted, and the pressure of the lean liquid entering the absorption tower is maintained by adjusting the opening.

[0048] In this embodiment, the cooler 18 is an air cooler or a water cooler. The addition of the air cooler or the water cooler allows the tower top steam to be quickly cooled and condensed, and the condensed product is flashed in the second flash evaporator to finally flash out the acid gas.

[0049] In this embodiment, in order to further improve the condensation effect of the tower top steam, a tower top condenser 23 is provided at the front end of the cooler 18. A low temperature working medium is introduced into the tower top condenser 23, and the low temperature working medium exchanges heat with the tower top steam introduced into the tower top condenser 23, so that the tower top steam is quickly cooled and condensed. Then, the tower top steam is further fully condensed through the cooler 18.

[0050] In this embodiment, the low-energy amine liquid acid gas removal process system also includes a compressor 21; the compressor 21, the working fluid condensation chamber of the reboiler 12 and the working fluid evaporation side of the tower top condenser 23 are connected in a serial cycle; the tower top steam outlet pipeline 16 is connected to the material condensation side of the tower top condenser 23, and the material condensation side is connected to the working fluid evaporation side for heat exchange.

[0051] Through the implementation of this scheme, the heat at the top of the regeneration tower 14 is used as the heat source of the reboiler 12 after the energy quality is improved, so that the external steam required by the original reboiler 12 can be completely eliminated, and the load of the original top wind / water cooler can be greatly reduced. The working energy consumption of the regeneration tower 14 is greatly reduced. Specifically: the top steam enters the top condenser 23, and the tower kettle steam entering the top condenser 23 is rapidly cooled down and condensed under the heat exchange of the top condenser 23, and the heat of the top steam is converted into the working fluid of the circulation pipeline 17. The working fluid is compressed into a high-temperature and high-pressure state by the compressor 21, and then the kettle liquid is heated in the reboiler 12. After passing through the reboiler 12, the working fluid is cooled to a high-temperature and high-pressure liquid state. After the cooling working fluid enters the top condenser 23, it exchanges heat with the top steam again, so that the working fluid is rapidly heated and vaporized, and the vaporized working fluid enters the compressor 21 again for the next cycle.

[0052] Due to the above process, the low-energy amine liquid acid gas removal process system of the present invention has the following effects:

[0053] 1. A closed-loop connection of the compressor 21, the reboiler 12 and the tower top condenser 23 is adopted, and the waste heat inside the regeneration tower 14 is recovered through the tower top condenser 23, and the waste heat is transferred to the working fluid in the downstream pipeline through heat exchange between the material condensation side and the working fluid evaporation side for recycling. Since the waste heat inside the regeneration tower 14 is effectively utilized, energy consumption is reduced. Compared with the traditional process, the low-energy consumption amine liquid deacidification process system inputs 1 part of electric energy through the compressor 21, realizes the utilization of 4-7 parts of thermal energy, and saves the load of the original tower top air / water cooler in the prior art;

[0054] 2. The low-energy amine liquid acid gas removal process system does not require external steam supply to evaporate the kettle liquid, but uses an electrically driven compressor 21 to compress the working fluid and heat the kettle liquid. Compared with the external steam supply method, the low-energy amine liquid acid gas removal process system has the advantage of low energy consumption. Electric energy can be converted from solar energy, wind energy, etc., avoiding the emission of pollutants generated by traditional combustion energy, which is in line with the concept of environmental protection and sustainable development;

[0055] 3. The heat recovery cycle process of the heat pump system is adopted. The working medium with a certain amount of heat energy is compressed and heated by the compressor 21. The heated working medium is used as the heat source in the reboiler 12 to directly heat the kettle liquid, further improving the energy utilization rate and reducing energy waste.

[0056] That is, the high-temperature and high-pressure working fluid exchanges heat with the material to be heated, transferring the heat energy released by the material to be recovered, thereby realizing energy transfer and thermal energy recycling.

[0057] In this embodiment, in order to further improve the evaporation effect and heat exchange effect of the working medium when entering the tower top condenser 23, an expansion valve 15 is further provided on the working medium transmission pipeline between the reboiler 12 and the tower top condenser 23. By providing the expansion valve 15 on the working medium transmission pipeline, the high-temperature and high-pressure liquid working medium is depressurized and cooled through the expansion valve 15 to form a low-temperature and low-pressure working medium state, and then heat is exchanged with the tower top steam through the tower top condenser 23, and the heat energy in the tower top steam is transferred to the working medium, thereby realizing energy transfer.

[0058] For example, in the tower top condenser 23, the low-temperature and low-pressure working fluid exchanges heat with the vapor-state tower top steam, condenses the tower top steam generated inside the regeneration tower 14 into liquid to form condensate, and transfers the heat energy in the tower top steam to the working fluid, thereby realizing energy transfer and heat energy recycling.

[0059] In this embodiment, a separation tank 19 is provided between the tower top condenser 23 and the compressor 21. The separation tank 19 allows the vaporized working medium to be separated into gas and liquid before entering the compressor 21, ensuring that the compressor 21 does not absorb liquid and cause liquid hammer, thereby ensuring the safety of the compressor 21.

[0060] In this embodiment, in order to further obtain a better working medium compression effect, the compressor 21 is a centrifugal compressor 21 .

[0061] Combined with the recovery of the pressure energy of the rich liquid pressure reducing valve in the original absorption tower kettle and the recovery of the heat energy in the regeneration tower 14, the low-energy amine liquid acid gas removal system recovers sufficient pressure energy and heat energy compared to the original system, reducing the system energy consumption by more than 50%.

[0062] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0063] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0064] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A low-energy amine liquid acid gas removal process system, characterized in that: The low-energy amine liquid acid gas removal process system comprises an absorption tower (1), a first flash tank (8), a second flash tank (20), a reboiler (12), a cooler (18) and a regeneration tower (14); The absorption tower (1), the first flash tank (8) and the regeneration tower (14) are cyclically connected, and a turbocharger pump is provided between the tower bottom rich liquid pipeline (7) of the absorption tower (1) and the tower bottom lean liquid pipeline (6) of the regeneration tower (14); One end of the turbocharger pump is provided with a chamber that accommodates a turbine (4) and is connected to the tower bottom rich liquid pipeline (7), and the other end is provided with a pump side (3) that is connected to the tower bottom lean liquid pipeline (6); The tower top steam outlet pipeline (16) of the regeneration tower (14) is connected to the second flash tank (20) after passing through the cooler (18), and the reflux pipeline (22) of the second flash tank (20) is connected to the reflux inlet of the regeneration tower (14); The bottom of the regeneration tower (14) is connected to the reboiler (12) via a kettle liquid pipeline (11), and the steam outlet of the reboiler (12) is connected to the steam inlet of the regeneration tower (14).

2. The low-energy amine liquid acid gas removal process system according to claim 1 is characterized in that: The rich liquid outlet pipeline (10) is connected to the tower bottom lean liquid pipeline (6) via a heat exchanger (9).

3. The low-energy amine liquid acid gas removal process system according to claim 1 is characterized in that: A front booster pump (5) is provided on the tower bottom lean liquid pipeline (6) at the front end of the pump side (3).

4. The low-energy amine liquid acid gas removal process system according to claim 1 is characterized in that: A pressure reducing valve (2) is provided on the tower bottom lean liquid pipeline (6) at the rear end of the pump side (3).

5. The low-energy amine liquid acid gas removal process system according to any one of claims 1 to 4, characterized in that: The cooler (18) is an air cooler or a water cooler.

6. The low-energy amine liquid acid gas removal process system according to any one of claims 1 to 4, characterized in that: A tower top condenser (23) is provided at the front end of the cooler (18).

7. The low-energy amine liquid acid gas removal process system according to claim 6 is characterized in that: The low-energy consumption amine liquid acid gas removal process system also includes a compressor (21); The compressor (21), the working medium condensation chamber of the reboiler (12), and the working medium evaporation side of the tower top condenser (23) are connected in a circular manner in sequence; The tower top steam outlet pipeline (16) is connected to the material condensation side of the tower top condenser (23), and the material condensation side is connected to the working medium evaporation side in a heat exchange manner.

8. The low-energy amine liquid acid gas removal process system according to claim 7 is characterized in that: An expansion valve (15) is also provided on the working medium transmission pipeline between the reboiler (12) and the tower top condenser (23).

9. The low-energy amine liquid acid gas removal process system according to claim 7 is characterized in that: A separation tank (19) is provided between the tower top condenser (23) and the compressor (21).

10. The low-energy amine liquid acid gas removal process system according to claim 7 is characterized in that: The compressor (21) is a centrifugal compressor (21).

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