CN-122006420-A - System and method for treating gas containing ethylene oxide and carbon dioxide

CN122006420ACN 122006420 ACN122006420 ACN 122006420ACN-122006420-A

Abstract

The invention relates to the field of ethylene oxide production, and discloses a treatment system and a treatment method for gas containing ethylene oxide and carbon dioxide. The treatment system comprises an ethylene oxide-carbon dioxide absorption tower, a flash tank and an ethylene oxide-carbon dioxide desorption tower which are communicated with each other, wherein the ethylene oxide-carbon dioxide absorption tower is used for synchronously absorbing ethylene oxide and carbon dioxide in reaction rich circulating gas to obtain a rich absorbent containing ethylene oxide and carbon dioxide and reaction lean circulating gas, the flash tank is used for carrying out flash evaporation treatment on the rich absorbent to obtain light component gas and a light component containing ethylene oxide and carbon dioxide, and the ethylene oxide-carbon dioxide desorption tower is used for synchronously desorbing the ethylene oxide and carbon dioxide in the light component to obtain the ethylene oxide, the carbon dioxide and the lean absorbent. The system can reduce the operation difficulty of ethylene oxide production and reduce the energy consumption and material consumption level of the device.

Inventors

WANG WEI
ZHAO JIANCHU
LI ZHUO
FENG LUJIA
ZHANG JIMIN
LIU ZIXIAO
SUN HAOYI
GU XIANG
SHAO LU

Assignees

中国石油化工股份有限公司
中国石化工程建设有限公司

Dates

Publication Date: 20260512
Application Date: 20241111

Claims (10)

1. A treatment system for ethylene oxide and carbon dioxide containing gas, characterized in that the system comprises an ethylene oxide-carbon dioxide absorption column (1), a flash tank (2) and an ethylene oxide-carbon dioxide desorption column (3) which are communicated with each other; the ethylene oxide-carbon dioxide absorption tower (1) is used for synchronously absorbing ethylene oxide and carbon dioxide in the reaction rich circulating gas (S1) to obtain a rich absorbent (S7) containing ethylene oxide and carbon dioxide and a reaction lean circulating gas (S2); The flash tank (2) is used for carrying out flash evaporation treatment on the rich absorbent (S7) to obtain light component gas (S3) and a light component containing ethylene oxide and carbon dioxide; The ethylene oxide-carbon dioxide desorption tower (3) is used for synchronously desorbing ethylene oxide and carbon dioxide in the light component to obtain ethylene oxide (S5), carbon dioxide (S4) and a lean absorbent (S6).
2. The system according to claim 1, wherein the system further comprises an ethylene oxide-carbon dioxide absorber feed/discharge heat exchanger (4), a first inlet of the ethylene oxide-carbon dioxide absorber feed/discharge heat exchanger (4) being in communication with the reaction rich recycle gas outlet of the upstream reaction unit, a first outlet of the ethylene oxide-carbon dioxide absorber feed/discharge heat exchanger (4) being in communication with the first inlet of the ethylene oxide-carbon dioxide absorber (1), a second inlet of the ethylene oxide-carbon dioxide absorber feed/discharge heat exchanger (4) being in communication with the first outlet of the ethylene oxide-carbon dioxide absorber (1), a second outlet of the ethylene oxide-carbon dioxide absorber feed/discharge heat exchanger (4) being in communication with the inlet of the flash tank (2).
3. The system according to claim 1 or 2, wherein the flash tank (2) is arranged vertically and/or horizontally, preferably horizontally; Preferably, a reabsorption section is arranged at the top of the flash tank (2) and is used for carrying out absorption treatment on flash gas rich in absorbent (S7) to obtain light component gas (S3).
4. A system according to any one of claims 1-3, wherein the system further comprises a desorption overhead condenser (6), a desorption column reflux drum (10) and a desorption column cryogenic (7), the inlet of the desorption overhead condenser (6) being in communication with the overhead gas phase outlet of the ethylene oxide-carbon dioxide desorption column (3), the outlet of the desorption overhead condenser (6) being in communication with the first inlet of the desorption column reflux drum (10); Preferably, the first outlet of the stripper reflux drum (10) is in communication with the first inlet of the ethylene oxide-carbon dioxide stripper column (3) and/or with a downstream ethylene oxide treatment device; preferably, the second outlet of the desorber reflux drum (10) is in communication with the inlet of the desorber overhead chiller (7); preferably, the first outlet of the desorption column top cryocooler (7) is in communication with a downstream carbon dioxide treatment device.
5. The system according to claim 4, wherein the system further comprises a carbon dioxide ejector (12), the suction side of the carbon dioxide ejector (12) being in communication with the second outlet of the desorption column top chiller (7), the exhaust side of the carbon dioxide ejector (12) being in communication with the second inlet of the ethylene oxide-carbon dioxide desorption column (3); Preferably, the system further comprises a lean/rich absorbent heat exchanger (5), a first inlet of the lean/rich absorbent heat exchanger (5) being in communication with a first outlet of the flash drum (2), a first outlet of the lean/rich absorbent heat exchanger (5) being in communication with a third inlet of the ethylene oxide-carbon dioxide desorber (3); Preferably, the system further comprises a lean absorbent injection flash tank (11), the inlet of the lean absorbent injection flash tank (11) being in communication with the bottom liquid phase outlet of the ethylene oxide-carbon dioxide desorption column (3), the liquid phase outlet of the lean absorbent injection flash tank (11) being in communication with the second inlet of the lean/rich absorbent heat exchanger (5), the gas phase outlet of the lean absorbent injection flash tank (11) being in communication with the exhaust side of the carbon dioxide injector (12); Preferably, the system further comprises a lean absorbent cooler (9), a first inlet of the lean absorbent cooler (9) being in communication with a second outlet of the lean/rich absorbent heat exchanger (5), a first outlet of the lean absorbent cooler (9) being in communication with a reabsorption section of the flash tank (2) and/or a second inlet of the ethylene oxide-carbon dioxide absorption column (1).
6. A process for the treatment of a gas containing ethylene oxide and carbon dioxide, wherein the process is carried out in a system according to any one of claims 1 to 5, the process comprising: (A) In the presence of a lean absorbent (S6), a reaction rich recycle gas (S1) containing ethylene oxide and carbon dioxide performs synchronous absorption of the ethylene oxide and the carbon dioxide in an ethylene oxide-carbon dioxide absorption tower (1) to obtain a rich absorbent (S7) containing the ethylene oxide and the carbon dioxide and a reaction lean recycle gas (S2), wherein the lean absorbent (S6) contains a composite absorbent; (B) The rich absorbent (S7) is subjected to flash evaporation treatment in a flash tank (2) to obtain light component gas S3 and a light component containing ethylene oxide and carbon dioxide; (C) And (3) synchronously desorbing the ethylene oxide and the carbon dioxide in an ethylene oxide-carbon dioxide desorber (3) to obtain ethylene oxide (S5), carbon dioxide (S4) and a lean absorbent (S6), and returning the lean absorbent (S6) to the step (A) for recycling.
7. The process according to claim 6, wherein in step (A), the concentration of ethylene oxide is 0.5 to 5mol/%, and the concentration of carbon dioxide is 0.5 to 9.5mol/%, based on the total amount in the reaction-rich recycle gas (S1); Preferably, in step (a), the reaction rich recycle gas (S1) has a temperature of 35-80 ℃ and a pressure of 1.2-3MPaG; preferably, in the step (a), the composite absorbent contains acrylic acid carbonate and/or polyethylene glycol dimethyl ether; Preferably, in the step (A), the content of acrylic acid carbonate and/or dimethyl polyethylene glycol in the lean absorbent (S6) is 30-100wt/%, based on the total amount of the lean absorbent; preferably, in step (a), the lean absorbent (S6) has a temperature of 5-50 ℃ and a pressure of 1.2-3MPaG; Preferably, in step (A), the conditions for simultaneous absorption include a pressure of 1.2-3MPaG.
8. The method of claim 6 or 7, wherein the pressure of step (a), step (B) and step (C) is reduced stepwise.
9. The process according to claim 6 or 7, wherein in step (B), the flash treatment conditions comprise a pressure of 0.1-1MPaG.
10. The process according to claim 6 or 7, wherein in step (C) the concentration of ethylene oxide is lower than 100ppm and the concentration of carbon dioxide is lower than 1.2mol/%; preferably, in step (C), the conditions for the simultaneous desorption include a pressure of-0.99 MPaG to 0.3MPaG and a temperature of 80-140 ℃.

Description

System and method for treating gas containing ethylene oxide and carbon dioxide Technical Field The invention relates to the technical field of ethylene oxide production, in particular to a treatment system and a treatment method for gas containing ethylene oxide and carbon dioxide. Background Ethylene Oxide (EO) is an important petrochemical product with excellent sterilization and disinfection effects. The method is mainly applied to the production of glycol, nonionic surfactant, water reducer, ethanolamine and the like. In recent years, the synthesis of EO and CO 2 to produce Ethylene Carbonate (EC) has also been applied because of the carbon dioxide (CO 2) which is a byproduct in the EO production process. EO is produced in the EO production industry mainly by the vapor phase reaction of ethylene and oxygen in the presence of a silver-containing catalyst, and due to the selective influence of the catalyst, the reaction also produces a large amount of CO 2 and a small amount of aldehyde impurities. Due to EO safety and catalyst conversion limitations, the reaction requires the use of large amounts of methane or nitrogen that are substantially stable and only a portion of the ethylene and oxygen are converted. Thus, the reaction product gas at the outlet of the EO reactor is a mixed gas containing EO, CO 2, methane or nitrogen, ethylene, oxygen, and aldehyde impurities. In order to further refine and separate EO later and ensure smooth reaction of the catalyst, EO, CO2 and the like generated by the reaction need to be removed in time. The prior art is realized by a two-step removal method, firstly, water is used as an absorbent, EO in the reaction rich recycle gas is removed in an EO absorption tower, then the recycle gas after EO removal is introduced into a CO 2 absorption tower, CO 2 is removed by a hot potash solution, and then the reaction lean recycle gas is returned to the inlet of the reactor by pressurization of a compressor. The two absorbents are required to consume a large amount of steam for desorption regeneration, and EO and CO 2 are removed respectively and recycled. The method has the problems of complex flow, high energy consumption, material loss (ethylene glycol is generated by hydration in the EO stripping process), difficult removal of aldehyde impurities and the like. Wherein, when absorbing CO 2 with hot potash solution, in order to promote absorption and meet the CO 2 concentration requirement at the inlet of the reactor, a decarbonization promoter of vanadate component prepared with high-toxic vanadium pentoxide (V 2O5) is also required to be added, which constitutes a potential risk for environmental and personnel safety. Therefore, development of a low-energy-consumption environment-friendly short-flow process capable of synchronously absorbing and synchronously desorbing and separating EO and CO 2 is needed. Patent application CN 115724819a discloses a process route for absorbing EO with EC (ethylene carbonate) instead of water as absorbent, although there is a certain reduction in material loss compared to water absorption, since the melting point of EC is as high as 39 ℃, the operation using an effective amount of absorbent is hindered, and thus it is difficult to achieve an effective reduction in heat recovery loss. According to the conventional method using water, the temperature of the absorption operation is 20-37 ℃, which is too low for EC. In order to perform the whole operation without any coagulation problems, the process should in practice be kept at least above 50 ℃. This means that the absorption operation using EC should be maintained at a temperature at least 13 ℃ higher than the operation using water. The absorption capacity of such an operation is correspondingly reduced, and therefore the amount of circulating absorbent must be increased, which greatly impairs the reduction of heat recovery losses between absorption and stripping. Second, the high freezing point of EC causes serious problems in operation, insulation and maintenance, such as the need to maintain heating of large amounts of absorbent even in the case of equipment not in operation, resulting in higher operating costs of the heating system. In addition, there is a tendency for pipe blockage or a decrease in heat exchange efficiency due to partial solidification caused by heat exchange contact between the EC and the cooling water. Because the absorption capacity of EC to CO 2 is weaker, the same absorption and water absorption processes of CO 2 still need to use hot potash solution, so the whole process flow of EO absorption and CO 2 absorption and desorption still belongs to respective absorption and two-step removal process of respective desorption, and the complexity is basically equivalent to that of the conventional water and hot potash absorption respectively. Patent application CN 110479037a discloses a composite absorbent comprising ionic liquid and EC instead of water for EO absorption, a