Low-energy-consumption MDEA decarburization device

Abstract

The utility model discloses a low energy consumption MDEA decarburization device, which comprises an absorption tower, a regeneration tower, a flash tank connected between the absorption tower and the regeneration tower, and a lean / rich liquid heat exchanger, the top end of the absorption tower is connected with an outlet separator, the top end of the regeneration tower is connected with an acid gas separation unit, and the top end of the regeneration tower is connected with an outlet separator. The semi-barren liquor circulating unit is connected between the absorption tower and the regeneration tower; the semi-lean solution circulating unit comprises a semi-lean / rich solution heat exchanger, a first inlet of the semi-lean / rich solution heat exchanger is connected with the middle part of the regeneration tower, and a first outlet of the semi-lean / rich solution heat exchanger is connected with the middle part of the absorption tower; according to the low-energy-consumption MDEA decarburization device provided by the utility model, the decarburization process flow of semi-barren liquor circulation is adopted, so that the CO2 removal effect is met, the circulation volume of semi-barren liquor is increased, and the circulation volume of system barren liquor is correspondingly reduced, and therefore, the steam quantity required by barren liquor regeneration and the water consumption of a barren liquor cooler and an acid gas reflux cooler can be reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to a gas separation technical field, concretely relates to a low energy consumption MDEA decarburization device. BACKGROUND

[0002] The original MDEA decarburization process flow is as follows: raw gas enters the absorption tower from the lower part, and is in countercurrent contact with MDEA solution in the tower, CO2 in the raw gas is absorbed into the liquid phase by MDEA, and the purified raw gas is led out from the top of the absorption tower, and is sent to the downstream after being separated into liquid drops.The MDEA rich liquid after absorbing CO2 is reduced in pressure by a pressure reducing valve, and then is heated by a lean / rich liquid heat exchanger before being introduced into a regeneration tower, and after being regenerated by stripping in the tower, the lean liquid from the bottom of the regeneration tower is cooled by a lean liquid cooler after being heat-exchanged by the lean / rich liquid heat exchanger, and is pumped back to the top of the absorption tower by a lean liquid circulating pump, thus completing the entire amine liquid circulation.The CO2 at the top of the regeneration tower is vented after being cooled and separated, and the condensed liquid separated is pumped back to the top of the regeneration tower by a reflux pump.In the above process, the reboiler at the bottom of the regeneration tower needs to consume more external heat energy for heating the regenerated MDEA solution, and the water consumption of the reflux cooler and the lean liquid cooler is increased due to the lean liquid regeneration circulation, thus consuming more energy; and moreover, the pressure energy of the rich liquid is not effectively recycled, which means that the original MDEA decarburization process flow has high energy consumption and poor economy. SUMMARY

[0003] In view of the deficiencies in the prior art, the utility model aims to provide a low energy consumption MDEA decarburization device to solve the problem of high energy consumption and poor economy of the device in the prior art.

[0004] To solve the above technical problems, the utility model adopts the following technical scheme: a low energy consumption MDEA decarburization device, an absorption tower, a regeneration tower, a flash tank connected between the absorption tower and the regeneration tower, and a lean / rich liquid heat exchanger, the top end of the absorption tower is connected with an outlet separator, the top end of the regeneration tower is connected with an acid gas separation unit, and further comprising a semi-lean liquid circulating unit connected between the absorption tower and the regeneration tower.

[0005] The semi-lean liquid circulating unit comprises a semi-lean / rich liquid heat exchanger, the first inlet of the semi-lean / rich liquid heat exchanger is connected with the middle part of the regeneration tower, and the first outlet of the semi-lean / rich liquid heat exchanger is connected with the middle part of the absorption tower.

[0006] The utility model further has the following technical features:

[0007] The semi-lean liquid circulating unit further comprises a semi-lean liquid circulating pump, the inlet of the semi-lean liquid circulating pump is connected with the first outlet of the semi-lean / rich liquid heat exchanger, and the outlet of the semi-lean liquid circulating pump is connected with the middle part of the absorption tower.

[0008] The second inlet of the semi-lean / rich liquid heat exchanger is connected with the liquid outlet of the flash tank, and the second outlet of the semi-lean / rich liquid heat exchanger is connected with the top of the regeneration tower.

[0009] The liquid force turbine is further connected between the flash tank and the absorption tower, and the output end of the liquid force turbine is connected with the semi-lean liquid circulating pump.

[0010] The bottom of the absorption tower is provided with a raw gas inlet, the bottom of the regeneration tower is connected with the inlet of the flash tank, the liquid outlet of the flash tank is connected with the first inlet of the lean / rich liquid heat exchanger, and the first outlet of the lean / rich liquid heat exchanger is connected with the top of the regeneration tower.

[0011] The second inlet of the lean / rich liquid heat exchanger is connected with the liquid outlet of the reboiler, the liquid inlet of the reboiler is connected with the bottom of the regeneration tower, and the gas outlet of the reboiler is connected with the middle part of the regeneration tower.

[0012] The second outlet of the lean / rich liquid heat exchanger is connected with the top of the absorption tower.

[0013] The acid gas separation unit comprises an acid gas separation tank, the inlet of the acid gas separation tank is connected with the top of the regeneration tower through an acid gas cooler, and the liquid outlet of the acid gas separation tank is connected with the top of the regeneration tower through a reflux pump.

[0014] The inlet of the outlet separator is connected with the top of the absorption tower.

[0015] The second outlet of the lean / rich liquid heat exchanger and the top of the absorption tower are further connected with a lean liquid circulating pump and a lean liquid cooler.

[0016] The liquid outlet of the reboiler and the second inlet of the lean / rich liquid heat exchanger are further connected with a booster pump.

[0017] The first outlet of the lean / rich liquid heat exchanger and the top of the regeneration tower are further connected with a pressure regulating valve.

[0018] Compared with the prior art, the utility model has the following technical effects:

[0019] (Ⅰ) the low energy consumption MDEA decarburization device of the utility model, adopt semi-lean liquid circulating decarburization technological process, in order to meet CO2 removal effect, increase the circulation of semi-lean liquid, correspondingly reduce the circulation of system lean liquid, thus can reduce the steam quantity required for lean liquid regeneration, and the water consumption of lean liquid cooler and acid gas reflux cooler.

[0020] (II) The low-energy-consumption MDEA decarburization device provided by the utility model replaces the liquid force turbine with the liquid pressure valve configured in the original process to recycle pressure energy, drags the semi-lean liquid circulating pump through the liquid force turbine output energy, and the energy consumption part of the increased semi-lean liquid circulation amount can be supplemented through the liquid force turbine output energy, so that the power consumption of driving the semi-lean liquid circulating pump can be saved.

[0021] (III) The low-energy-consumption MDEA decarburization device provided by the utility model has simple structure, convenient operation, safety and reliability, and strong adaptability. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a general structure schematic view of the low-energy-consumption MDEA decarburization device.

[0023] Meaning of each reference numeral in the drawing:

[0024] 1-absorption tower, 2-regeneration tower, 3-flash tank, 4-lean / rich liquid heat exchanger, 5-outlet separator, 6-acid gas separation unit, 7-semi-lean liquid circulating unit, 8-liquid force turbine, 9-reboiler, 10-lean liquid circulating pump, 11-lean liquid cooler, 12-boosting pump, 13-pressure regulating valve.

[0025] 6-1-acid gas separation tank, 6-2-acid gas cooler, 6-3-reflux pump.

[0026] 7-1 semi-lean / rich liquid heat exchanger, 7-2 semi-lean liquid circulating pump.

[0027] The specific content of the utility model is further explained and described in detail in combination with the following embodiments. DETAILED DESCRIPTION

[0028] All components in the utility model are known components in the prior art, unless otherwise specified.

[0029] Taking the project being executed as an example, in the coke oven gas synthetic ammonia process, the CO2 in the decarburization device outlet purification gas is required to be controlled to be ≤30ppm in the raw material gas CO2 removal link, so as to meet the requirement of the downstream ammonia synthesis.

[0030] Among numerous decarburization methods, the MDEA method has the advantages of high purification degree, small nitrogen and hydrogen gas loss, non-degradation of solution, small volatilization loss and adaptability to high acid raw material gas, and is widely used.

[0031] MDEA is also known as N-methyldiethanolamine, and the MDEA decarburization technology is to use activated MDEA aqueous solution to absorb carbon dioxide (CO2) in natural gas or synthetic gas at high pressure and normal temperature, and in the case of pressure reduction and temperature rise, the carbon dioxide (CO2) is desorbed from the solution again, and the solution is regenerated.

[0032] When the raw material gas treatment capacity is large and the content of CO2 and other acid gases is high, the original MDEA decarburization device system is adopted, the system residual pressure is not reasonably utilized, and the regeneration energy consumption of MDEA solution is high, and the economy is poor. In order to adapt to the trend of energy saving and emission reduction, it is necessary to put forward a kind of low energy consumption MDEA decarburization device.

[0033] The specific embodiments of the present application are given below, and it should be noted that the present application is not limited to the following specific embodiments, and any equivalent transformation based on the technical scheme of the present application falls within the protection scope of the present application.

[0034] Embodiment 1:

[0035] The embodiment gives a kind of low energy consumption MDEA decarburization device, as shown in 1, including absorption tower 1, regeneration tower 2 and the flash tank 3 connected between absorption tower 1 and regeneration tower 2 and lean / rich liquid heat exchanger 4, the top of the absorption tower 1 is connected with outlet separator 5, the top of the regeneration tower 2 is connected with acid gas separation unit 6, further including semi-lean liquid circulating unit 7 connected between absorption tower 1 and regeneration tower 2.

[0036] The semi-lean liquid circulating unit 7 includes semi-lean / rich liquid heat exchanger 7-1, the first inlet of the semi-lean / rich liquid heat exchanger 7-1 is connected to the middle part of the regeneration tower 2, and the first outlet of the semi-lean / rich liquid heat exchanger 7-1 is connected to the middle part of the absorption tower 1.

[0037] The decarburization process using semi-lean liquid circulation, in order to meet the CO2 removal effect, increase the circulation amount of semi-lean liquid, correspondingly reduce the circulation amount of lean liquid in the system, so as to reduce the steam amount required for lean liquid regeneration, and the water consumption of lean liquid cooler and acid gas reflux cooler.

[0038] As a preferred embodiment of the present application:

[0039] The semi-lean liquid circulating unit 7 further includes semi-lean liquid circulating pump 7-2, the inlet of the semi-lean liquid circulating pump 7-2 is connected to the first outlet of the semi-lean / rich liquid heat exchanger 7-1, and the outlet of the semi-lean liquid circulating pump 7-2 is connected to the middle part of the absorption tower 1.

[0040] The second inlet of the semi-lean / rich liquid heat exchanger 7-1 is connected to the liquid outlet of the flash tank 3, and the second outlet of the semi-lean / rich liquid heat exchanger 7-1 is connected to the top of the regeneration tower 2.

[0041] The liquid turbine 8 is connected between the flash tank 3 and the absorption tower 1, and the output end of the liquid turbine 8 is connected with the semi-lean liquid circulating pump 7-2.

[0042] The liquid turbine 8 driven by the recovered pressure energy drives the semi-lean liquid circulating pump 7-2, so that the power consumption of the semi-lean liquid circulating pump can be saved.

[0043] As a preferred embodiment of the present application:

[0044] The bottom side of the absorption tower 1 is connected with the raw gas inlet, the bottom of the regeneration tower 2 is connected with the inlet of the flash tank 3, the liquid outlet of the flash tank 3 is connected with the first inlet of the lean / rich liquid heat exchanger 4, and the first outlet of the lean / rich liquid heat exchanger 4 is connected with the top of the regeneration tower 2.

[0045] The second inlet of the lean / rich liquid heat exchanger 4 is connected with the liquid outlet of the reboiler 9, the liquid inlet of the reboiler 9 is connected with the bottom of the regeneration tower 2, and the gas outlet of the reboiler 9 is connected with the middle part of the regeneration tower 2.

[0046] The second outlet of the lean / rich liquid heat exchanger 4 is connected with the top of the absorption tower 1.

[0047] As a preferred embodiment of the present application:

[0048] The acid gas separation unit 6 comprises an acid gas separation tank 6-1, the inlet of the acid gas separation tank 6-1 is connected with the top of the regeneration tower 2 through the acid gas cooler 6-2, and the liquid outlet of the acid gas separation tank 6-1 is connected with the top of the regeneration tower 2 through the reflux pump 6-3.

[0049] As a preferred embodiment of the present application:

[0050] The inlet of the outlet separator 5 is connected with the top of the absorption tower 1.

[0051] As a preferred embodiment of the present application:

[0052] The second outlet of the lean / rich liquid heat exchanger 4 and the top of the absorption tower 1 are further connected with the lean liquid circulating pump 10 and the lean liquid cooler 11.

[0053] The liquid outlet of the reboiler 9 and the second inlet of the lean / rich liquid heat exchanger 4 are further connected with the booster pump 12.

[0054] The first outlet of the lean / rich liquid heat exchanger 4 and the top of the regeneration tower 2 are further connected with the pressure regulating valve 13.

[0055] The specific working process of the present application is as follows:

[0056] Lean liquid: MDEA solution without CO2 and other acid gases.

[0057] Half lean solution: MDEA solution containing a small amount of acid gas such as CO2 after partial regeneration.

[0058] Flash gas: A small amount of acid gas such as CO2 is released after the high-pressure rich solution is decompressed.

[0059] Purified gas: Raw material gas after removal of acid gas such as CO2 (after decarburization).

[0060] Condensate: Alcohol amine droplets separated from wet purified gas.

[0061] Raw material gas: Synthesis gas to be decarburized.

[0062] Heating steam: Steam as an external supplemental heat source.

[0063] The system comprises an absorption tower 1, an outlet separator 5, a flash tank 3, a regeneration tower 2, a reboiler 9, a liquid turbine 8, a booster pump 12 connected to the bottom of the regeneration tower 2, a lean / rich solution heat exchanger 4, a lean solution cooler 11, a lean solution circulating pump 10, the top of the absorption tower 1, a half-lean / rich solution heat exchanger 7-1 connected to the middle of the regeneration tower 2, and a half-lean solution circulating pump 7-2 connected to the upper part of the absorption tower 1. The top of the regeneration tower 2 is connected to an acid gas cooler 6-2 and an acid gas separator 6-1 in sequence, and a reflux pump 6-3 is connected to the top of the regeneration tower 2.

[0064] MDEA rich solution absorbing CO2 is discharged from the bottom of the absorption tower 1, connected to the liquid turbine 8, and the expanded and decompressed rich solution enters the flash tank 3. The rich solution flows into the upper liquid phase port of the regeneration tower 2 after passing through the lean / rich solution heat exchanger 4 and the half-lean / rich solution heat exchanger 7-1.

[0065] The lean solution from the bottom of the regeneration tower 2 passes through the booster pump 12, the lean / rich solution heat exchanger 4, the lean solution cooler 11, and the lean solution circulating pump 12 in sequence to return to the top of the absorption tower 1, completing the lean solution circulation process.

[0066] The half-lean solution from the middle of the regeneration tower 2 passes through the half-lean / rich solution heat exchanger 7-1 and the half-lean solution circulating pump 7-2 in sequence to return to the upper part of the absorption tower 1, completing the half-lean solution circulation process. In this process, the liquid turbine 8 used to recover pressure energy is used to drive the half-lean solution circulating pump 7-2, saving the electricity consumption required by the half-lean solution circulating pump 7-2.

[0067] The rich solution is heated and enters the upper part of the regeneration tower 2, where the solution is regenerated. The released acid components such as CO2 are discharged from the top of the regeneration tower 2, and the condensed liquid cooled by the acid gas cooler 6-2 is sent back to the top liquid phase port of the regeneration tower 2 by the reflux pump 6-3.

[0068] The lean / rich solution heat exchanger 4 and the half-lean / rich solution heat exchanger 7-1 are both plate heat exchangers. The lean solution cooler 11 and the acid gas cooler 6-2 are both shell-and-tube heat exchangers.

[0069] The hydraulic turbine 8 is arranged in a manner of hydraulic turbine + clutch + motor + semi-lean liquid circulating pump. The hydraulic turbine 8 adjusts the flow through the inlet regulating valve and bypass.

[0070] During the device startup process or part load operation, the rich liquid flow through the hydraulic turbine cannot reach full load, so that the power output is not enough to drive the semi-lean liquid circulating pump. Therefore, the motor is used to drive the semi-lean liquid circulating pump in the early stage. When the device load reaches the requirement, the hydraulic turbine is connected to the semi-lean liquid circulating pump through the clutch as the main driving machine. In addition, if the hydraulic turbine fails, it will be cut out of the system through the clutch to carry out maintenance, and the motor drives the semi-lean liquid circulating pump at this time, which does not affect the operation of the MDEA decarbonization system.

[0071] The rich liquid pressure reducing valve of the traditional configuration is replaced by the hydraulic turbine to recover pressure energy. The MDEA decarbonization system considers the recovery and utilization of the rich amine liquid surplus pressure in the design. The pressure energy of the rich liquid is recovered through the setting of the hydraulic turbine, and the semi-lean liquid circulating pump is driven to do work, which can save the power consumption of driving the semi-lean liquid circulating pump.

[0072] Due to the high CO2 content in the raw material gas, the circulation amount of amine liquid required by the MDEA decarbonization system is large. In order to reduce the energy consumption of the regeneration tower, that is, to reduce the steam consumption of the reboiler, the semi-lean liquid circulating absorption tower flow can be increased, and the lean liquid regeneration return absorption tower flow can be correspondingly reduced. The power consumption of increasing the semi-lean liquid circulation amount is balanced and compensated by the output energy of the hydraulic turbine.

[0073] The raw gas enters the bottom of the absorption tower 1 and is contacted with the MDEA lean liquid injected from the top of the tower in countercurrent to remove the CO2 and other acid gases in the raw gas, and the purified gas is discharged from the top of the tower. The wet purified gas is removed from the outlet separator 5 to remove the alcohol amine droplets carried, and then goes to the downstream device. The MDEA rich liquid after absorbing CO2 flows out from the bottom of the absorption tower 1 (about 2.5 MPa.G), and enters the flash tank 3 after recovering pressure energy by the liquid turbine 8. The rich liquid after flashing enters the semi-lean / rich liquid heat exchanger 7-1 and the lean / rich liquid heat exchanger 4 to recover heat, and then enters the upper part of the regeneration tower 2 (about 0.5 MPa.G) for further atmospheric resolution. The rich liquid along the regeneration tower 2 downwardly contacts with the steam from the stripping section in countercurrent, and most of the CO2 is resolved. The semi-lean liquid from the middle part of the regeneration tower 2 enters the semi-lean / rich liquid heat exchanger 7-1 through the semi-lean liquid circulating pump 7-2 to return to the upper part of the absorption tower 1, and the semi-lean liquid circulation is completed. The liquid turbine 8 driven by the recovery of pressure energy drives the semi-lean liquid circulating pump, so that the power consumption of the semi-lean liquid circulating pump 7-2 can be saved. The semi-lean liquid is heated in the reboiler 9, and the CO2 is further resolved under high temperature conditions, and the solution is completely regenerated. The MDEA lean liquid (about 120℃) after complete regeneration flows out from the bottom of the regeneration tower 2, and is heat-exchanged with the rich liquid in the lean / rich liquid heat exchanger 4. The temperature is reduced, and then the lean liquid is further cooled to 40℃ by the lean liquid cooler 11. Finally, the lean liquid is pumped back to the top of the absorption tower 1 by the lean liquid circulating pump 12 to complete the lean liquid circulation. The steam, CO2 and other acid gases discharged from the top of the regeneration tower 2 are cooled by the acid gas cooler 6-2, and the condensed liquid returns to the top of the regeneration tower 2 as reflux liquid. The separated tail gas is vented and treated.

[0074] The above technical solution is only a relatively preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any skilled person in the art can think of changes or replacements within the technical range disclosed by the present application without creative labor, which is covered by the protection scope of the present application.

Claims

1. A low energy consumption MDEA decarbonization device, comprising an absorption tower (1), a regeneration tower (2) and a flash tank (3) connected between the absorption tower (1) and the regeneration tower (2), and a lean / rich liquid heat exchanger (4), the top end of the absorption tower (1) is connected with an outlet separator (5), the top end of the regeneration tower (2) is connected with a sour gas separation unit (6), characterized in that, The semi-lean liquid circulation unit (7) is connected between the absorption tower (1) and the regeneration tower (2); The semi-lean / lean liquid heat exchanger (7-1) is connected to the middle part of the regeneration tower (2) at the first inlet, and the first outlet of the semi-lean / lean liquid heat exchanger (7-1) is connected to the middle part of the absorption tower (1).

2. A low energy MDEA decarbonization unit as claimed in claim 1, wherein, The semi-lean liquid circulation pump (7-2) is connected to the first outlet of the semi-lean / lean liquid heat exchanger (7-1) at the inlet, and the outlet of the semi-lean liquid circulation pump (7-2) is connected to the middle part of the absorption tower (1); The second inlet of the semi-lean / lean liquid heat exchanger (7-1) is connected to the liquid outlet of the flash tank (3), and the second outlet of the semi-lean / lean liquid heat exchanger (7-1) is connected to the top of the regeneration tower (2); The liquid force turbine (8) is connected between the flash tank (3) and the absorption tower (1), and the output end of the liquid force turbine (8) is connected to the semi-lean liquid circulation pump (7-2).

3. A low energy MDEA decarbonation unit as claimed in claim 2, wherein, The bottom side of the absorption tower (1) is connected to the raw material gas inlet, the bottom of the regeneration tower (2) is connected to the inlet of the flash tank (3), the liquid outlet of the flash tank (3) is connected to the first inlet of the lean / lean liquid heat exchanger (4), and the first outlet of the lean / lean liquid heat exchanger (4) is connected to the top of the regeneration tower (2); The second inlet of the lean / lean liquid heat exchanger (4) is connected to the liquid outlet of the reboiler (9), the liquid inlet of the reboiler (9) is connected to the bottom of the regeneration tower (2), and the gas outlet of the reboiler (9) is connected to the middle part of the regeneration tower (2); The second outlet of the lean / lean liquid heat exchanger (4) is connected to the top of the absorption tower (1).

4. A low energy MDEA decarbonation unit as claimed in claim 1, wherein, The acid gas separation unit (6) includes an acid gas separation tank (6-1), and the inlet of the acid gas separation tank (6-1) is connected to the top of the regeneration tower (2) through an acid gas cooler (6-2); the liquid outlet of the acid gas separation tank (6-1) is connected to the top of the regeneration tower (2) through a reflux pump (6-3).

5. A low energy MDEA decarbonization unit as claimed in claim 1, wherein, The inlet of the outlet separator (5) is connected to the top of the absorption tower (1).

6. A low energy MDEA decarbonation unit as claimed in claim 3, wherein, The second outlet of the lean / lean liquid heat exchanger (4) and the top of the absorption tower (1) are further connected to a lean liquid circulation pump (10) and a lean liquid cooler (11); The liquid outlet of the reboiler (9) and the second inlet of the lean / lean liquid heat exchanger (4) are further connected to a booster pump (12); The first outlet of the lean / lean liquid heat exchanger (4) and the top of the regeneration tower (2) are further connected to a pressure regulating valve (13).

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