Split-flow rectisol device

A low-temperature methanol washing and split-flow technology, which is applied in the field of gas purification, can solve the problems of large mutual influence on heat balance of heat exchangers, high interdependence of logistics, and complex heat exchange network, so as to reduce energy consumption and complexity , the effect of saving steam consumption

Active Publication Date: 2009-12-02

SHANGHAI INT ENG CONSULTING

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Problems solved by technology

[0016] (1) The heat exchange network is complex, the logistics are highly correlated, the whole device takes a long time to start, and the control stability is difficult

[0017] (2) Methanol used for absorption is all heat-regenerated lean methanol, and the regeneration energy consumption is high

[0018] (3) Multiple coiled tube heat exchangers are used, for example, the first multi-stre...

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Abstract

The invention discloses a split-flow rectisol device, which comprises an absorption tower, a medium pressure flash tower, a reabsorber, a hot regenerating tower, a methanol water tower, a tail gas washing tower, a plurality of heat exchangers, pumps and a circulation compressor; and the upper section of the reabsorber is provided with a flash distillation section. The split-flow rectisol device is not provided with a CO2 product tower, and reduces the complexity of the flow and the investment on the premise of ensuring that CO2 product gas is qualified. The split-flow rectisol device is provided with a novel split-flow rectisol (acid gas removal) flow for absorption from a semi-lean methanol liquid feeding absorption tower on the upper section of the reabsorber, reduces the dosage of lean methanol of the absorption tower, further can reduce the energy consumption of the hot regenerating tower for hot regeneration, and saves the dosage of gas stripping nitrogen, consumption of steam, and low level cold quantity used when the lean methanol is cooled.

Application Domain

Dispersed particle separation

Technology Topic

RectisolDistillation +11

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Examples

Experimental program(1)

Example Embodiment

[0035] Such as figure 2 The split-flow low-temperature methanol washing device shown includes absorption tower T1, medium pressure flash tower T2, reabsorption tower T4, thermal regeneration tower T5, methanol water tower T6, tail gas scrubber T7, several heat exchangers, pumps, and circulating compression The raw material gas is firstly washed by the raw gas scrubber (not shown in the figure), mixed with the circulating gas after being washed, and cooled by the first heat exchanger E1, and then enters the lower section of the absorption tower T1; the upper section of the absorption tower T1 For CO 2 Absorption section, the lower section is H 2 S absorption section.

[0036] The CO in the raw gas after passing through the absorption tower T1 2 The impurities with sulfide are effectively removed, and the purified gas from the top of the absorption tower T1 passes through the heat exchange in the first heat exchanger E1 and then exits the device.

[0037] The upper section of the absorption tower T1 is connected with the second heat exchanger E2 to condense and recover the methanol gas from the upper section of the absorption tower T1, and the recovered methanol liquid is returned to the upper section of the absorption tower T1.

[0038] Absorbed H 2 After S and COS, the sulfur-containing methanol rich liquid 5 from the bottom of the absorption tower T1 is directly sent to the lower section of the medium pressure flash tower T2 to flash out dissolved H 2 , CO and some CO 2 Gas; part of the sulfur-free methanol rich liquid from the lower section of the absorption tower T1 is directly sent to the upper section of the medium-pressure flash tower T2 to flash out dissolved H 2 , CO and some CO 2 After the other part of the gas passes through the third heat exchanger E3 to exchange heat, it returns to the lower section of the absorption tower T1; the two parts of the flash gas 7 are washed by the sulfur-rich methanol 19 pumped by the third pump P3, and then flowed from the medium pressure flash tower T2 After the upper stage comes out, it is pressurized by the circulating gas compressor C1 and then returned to the raw gas.

[0039] The sulfur-containing methanol 8 from the lower section of the medium-pressure flash tower T2 is decompressed and sent to the lower section of the reabsorption tower T4 to flash out dissolved CO 2 , While dissolved H 2 S is also partially flashed out. The sulfur-free methanol solution 9 from the upper section of the medium-pressure flash tower T2 undergoes heat exchange through the fourth heat exchanger E4 and the fifth heat exchanger E5, and then enters the flash section 30 of the reabsorption tower T4, where the dissolved CO is flashed out 2 gas.

[0040] Part of the semi-lean methanol liquid 29 from the flash section 30 of the reabsorption tower T4 is returned to the lower section of the reabsorption tower T4 to scrub the sulfur-containing gas, and the other part is boosted by the first pump P1 and then enters the absorption tower T1 as a semi-lean solution for absorption. liquid. Re-absorption tower T4 flash section 30 to obtain CO 2 Product gas, this CO2 product gas passes through the first heat exchanger E1 and leaves the system; the lower section of the absorption tower T4 is stripped with nitrogen, the upper section obtains sulfur-free tail gas 12, and the sulfur-free tail gas 12 undergoes the first heat exchange After heat exchange, the device E1 enters the lower section of the tail gas scrubber T7, where the tail gas is washed with desalinated water in the tail gas scrubber T7, the methanol is recovered, and the scrubbed tail gas leaves the system.

[0041] The sulfur-containing solution 13 from the middle of the lower section of the reabsorption tower T4 is pressurized by the pump P2, and the cold energy is recovered by the seventh heat exchanger E7, the fourth heat exchanger E4, and the third heat exchanger E3, and then returns to the re-absorption The bottom of tower T4 flashes out the dissolved gas.

[0042] Reabsorb CO from the bottom of T4 2 After the low-content sulfur-rich methanol liquid is boosted by the P3 pump, a part of it is sent to the lower section of the medium-pressure flash tower T2 to absorb the CO from the medium-pressure flash tower. 2 , The other part passes through the eighth heat exchanger E8 and the tenth heat exchanger E10 to exchange heat with the lean methanol 20 from the bottom of the thermal regeneration tower T5, and then enters the thermal regeneration tower T5 for thermal regeneration. The bottom of the thermal regeneration tower T5 is obtained Lean in methanol 20, sulfur-rich acid gas 21 is obtained at the top of the tower.

[0043] After the lean methanol 20 comes out from the bottom of the thermal regeneration tower T5, after being boosted by the fourth pump P4, a part of 20a is cooled by the tenth heat exchanger E10, the ninth heat exchanger E9, the eighth heat exchanger E8, and the lean methanol Reactor E16 and seventh heat exchanger E7 are sent to the top of absorption tower T1 as lean methanol for absorption after heat exchange and cooling, and the other part 21b is sent to the top of methanol water tower T6 as reflux.

[0044] After the sulfur-rich acid gas 21 is cooled by the eleventh heat exchanger E11, it is sent to the reflux tank 22 for reflux. The liquid 23 formed by the reflux is pressurized by the pump P7 and sent to the upper section of the thermal regeneration tower T5. The gas 24 formed by the reflux is passed through After the twelfth heat exchanger E12 is cooled, it is sent to the acid gas separation tank 25 for gas-liquid separation. A part of the acid gas separated by the acid gas separation tank 25 exits the device, and the other part 26 is returned to the lower section of the reabsorption tower T4.

[0045] The bottom of the thermal regeneration tower T5 is heated and rectified with steam through the thirteenth heat exchanger E13 to recover the lean methanol 20 in the water; the methanol aqueous solution 27 from the bottom of the tail gas scrubber T7 tower is pressurized by the pump P6 and undergoes the fifteenth heat exchange After the temperature of the heat exchanger E15 is cooled, the methanol liquid is sent to the middle of the methanol water tower T6. The water 28 from the bottom of the methanol water tower T6 whose methanol content reaches the discharge standard is boosted by the fifth pump P5 and the heat is recovered by the fifteenth heat exchanger E15, and then directly discharged from the device ; The bottom of the methanol water tower T6 is heated and rectified with steam through the fourteenth heat exchanger E14 to recover the methanol in the water.

[0046] The aforementioned third heat exchanger E3 and fourth heat exchanger E4 are shell and tube heat exchangers.

[0047] This embodiment adopts a split-flow washing process: that is, the semi-lean methanol solution 29 enters the middle of the absorption tower T1 for main absorption, and a part of the lean methanol 20a enters the top of the absorption tower T1 for fine washing, and the energy consumption of heat regeneration and cooling is reduced; When the sulfur-rich methanol liquid 19 washes the flash gas, the power consumption of the circulating compressor is reduced. A lean methanol cooler E16 is provided after the eighth heat exchanger E8 of lean/rich methanol. The lean methanol cooler E16 is only used during driving, which can effectively reduce the time used for system cooling during driving, and can compensate for the lack of cooling capacity during driving, thereby shortening the driving time.

[0048] For the raw material gas flow rate of 420,000 Nm3/h and the pressure of 5.0-6.0 MPa(G), the cold energy consumption of the invention at -40°C is 5.8 Gcal/h, the hot regeneration steam consumption is 21 t/h, and the start-up time is shortened. In the prior art, the cold energy consumption at -40°C is 6.1 Gcal/h, the steam consumption for thermal regeneration is 22t/h, and the start-up time is long. The comparison results show that the process of the embodiment can significantly reduce the investment, the process is simple, the control is simple and stable, the steam and cold consumption is reduced, and there is a greater advantage in shortening the start-up time.

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Description & Claims & Application Information

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Classification and recommendation of technical efficacy words

Reduce complexity
Less investment

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Reduce dosage Reduce energy consumption Reduce steam consumption Nitrogen gas Medium pressure Exhaust gas Process engineering Product gas Nitrogen

Split-flow rectisol device

AI-Extracted Technical Summary

Problems solved by technology

Abstract

Image

Examples

Example Embodiment

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Description & Claims & Application Information

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