CN111995489A - System and method for treating tail gas of ethylbenzene oxidation reaction - Google Patents
System and method for treating tail gas of ethylbenzene oxidation reaction Download PDFInfo
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- CN111995489A CN111995489A CN202010876039.5A CN202010876039A CN111995489A CN 111995489 A CN111995489 A CN 111995489A CN 202010876039 A CN202010876039 A CN 202010876039A CN 111995489 A CN111995489 A CN 111995489A
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Abstract
The invention discloses a system and a method for treating tail gas of ethylbenzene oxidation reaction, belonging to the field of chemical industry. The system comprises a direct heat exchange tower, wherein the output end of oxidation tail gas is connected with the lower part of the direct heat exchange tower, the output end of the top of the direct heat exchange tower is connected with the lower part of a cooling washing tower, output pipelines of ethylbenzene are respectively connected with the middle part and the upper part of the cooling washing tower, an ethylbenzene water separator is arranged at the bottom of the cooling washing tower, and one output end of the ethylbenzene water separator is connected with the upper part of the direct heat exchange tower through a direct heat exchange tower feeding heater; the output end of the top of the cooling washing tower is connected with the lower part of the tail gas absorption tower. The light components and water in the circulating ethylbenzene are not easily brought into the oxidation reactor, the partial pressure of water vapor in an oxidation system is low, slagging is reduced, the operation period of the device is prolonged, the circulating ethylbenzene is directly mixed with the oxidation tail gas for heat exchange before entering the ethylbenzene oxidation reactor, and the heat of the oxidation tail gas is fully recovered.
Description
Technical Field
The invention relates to the field of chemical industry, in particular to a system and a method for treating tail gas of ethylbenzene oxidation reaction.
Background
At present, the industrial production technology of propylene oxide mainly comprises a chlorohydrin method and an indirect oxidation method.
The chlorohydrination method for producing the propylene oxide is characterized by short flow, mature process, larger operation load elasticity, good selectivity, high yield, safer production, low requirement on the purity of the raw material propylene and less construction investment; however, a large amount of waste water containing calcium chloride is generated in the process of producing propylene oxide by a chlorohydrin method, and the environmental pollution is serious, so that the examination and approval of a newly-built propylene oxide device by the chlorohydrin method are stopped in China since 2011.
In the technology for producing the propylene oxide by adopting the indirect oxidation method, the oxidant for oxidizing the propylene can be organic hydroperoxide, hydrogen peroxide and the like. At present, the organic hydroperoxide used for the oxidation of propylene can be produced technically from other organic hydroperoxides, such as cumene, isopentane, cyclohexane or other organic compounds, in addition to tert-butyl hydroperoxide (produced from isobutane) and ethylbenzene hydroperoxide (produced from ethylbenzene). The hydroperoxide corresponding to the organic matters is used for oxidizing propylene and can also be used for producing propylene oxide, but because the molecular weight of the propylene oxide is lower and the quantity of co-products is larger, the source of raw material hydrocarbon is reliable, the market sales of a large quantity of co-products and the price relationship between the co-products and the raw material hydrocarbon have direct influence on the economy of a device for producing the propylene oxide by an indirect oxidation method.
For an indirect oxidation method using isobutane as a raw material, C4 is rich in resource, tert-butyl alcohol which is a coproduct can be used as a gasoline additive, isobutene prepared by dehydration can also be used for a methyl methacrylate device, and the larger purpose is to produce methyl tert-butyl ether (MTBE) after dehydration and methanol etherification.
For indirect oxidation processes using ethylbenzene feedstock, the ethylbenzene is derived from the alkylation of ethylene and benzene; the co-product styrene has large market capacity, the current domestic self-sufficiency rate is only about 70 percent, the sale price is higher, and the economic efficiency is better.
Because isobutane and ethylbenzene have the above-mentioned conditions, and the hydrocarbons are low in cost and competitive in the production of propylene oxide, the rapid development has been achieved since the industrialization was realized in 1969, and the hydrocarbons are currently the main processes of indirect oxidation propylene oxide plants in the world.
The ethylbenzene co-oxidation process was developed by the company Ockran (ACRO) USA, now owned by the company Liander (Lyondell) USA. In addition to Lyondell's ethylbenzene co-oxidation process, the styrene-propylene oxide co-production process is also the Shell process. The Shell method was developed by Shell corporation of the Netherlands.
The co-oxidation of ethylbenzene to produce propylene oxide and co-produce styrene (POSM) generally involves the oxidation of ethylbenzene to ethylbenzene hydroperoxide (EBHP) at a temperature and pressure using air, followed by the epoxidation of propylene with ethylbenzene hydroperoxide (EBHP) to produce propylene oxide and co-produce styrene.
The ethylbenzene is oxidized into ethylbenzene hydroperoxide (EBHP), the reaction pressure is not high, the reaction is exothermic, and a large amount of heat can be released in the reaction process because the reaction conversion rate exceeds 10%. At low pressure, part of the ethylbenzene vaporizes and vaporizes, taking away part of the heat, and the remaining heat needs to be removed by heat exchange to maintain the reaction temperature in the reactor.
The ethylbenzene oxidation tail gas contains vaporized ethylbenzene, nitrogen, unreacted oxygen, water, light components and the like, the temperature of the ethylbenzene oxidation tail gas is usually 130-150 ℃, the pressure is 0.2-0.5MPa, the flow of the oxidation tail gas is large, the contained heat is high, and the significance of effectively recovering the heat of the oxidation tail gas is great.
The recycling of the ethylbenzene in the oxidation tail gas is beneficial to reducing consumption, and the removal of water carried in the recycled ethylbenzene is beneficial to reducing adverse effects of water on oxidation reaction.
Principle of ethylbenzene oxidation reaction
The liquid phase oxidation reaction of ethylbenzene usually adopts air as an oxidant, and oxygen in the air reacts with ethylbenzene to generate ethylbenzene hydroperoxide. The chemical reaction formula of the main reaction is as follows:
like other oxidation reactions, ethylbenzene oxidation is accompanied by a number of side reactions, the chemical equation for the main side reaction being:
in the process of using ethylbenzene oxidation product for producing propylene oxide by oxidizing propylene, it is desirable that the concentration of ethylbenzene hydroperoxide in the oxidation reaction product liquid is high, however, the decomposition reaction of ethylbenzene hydroperoxide is a secondary reaction, and the reaction rate is proportional to the square of the concentration of ethylbenzene hydroperoxide, so that a certain conversion rate needs to be strictly controlled. Since controlling the partial pressure of steam in the oxidation system has a direct effect on reducing slagging and prolonging the operating cycle. The water produced by the side reaction and the water carried in the ethylbenzene feed are required to be reduced as much as possible, on one hand, a proper conversion rate needs to be controlled, the conversion rate of the ethylbenzene oxidation reaction cannot be too high, the side reaction is reduced, and in addition, the water produced is removed as much as possible when the oxidation reaction materials are recycled. The water content in the oxidation reactor is reduced as much as possible. At present, the prior art has the following defects:
1) light components and water in the circulating ethylbenzene are easily brought into the oxidation reactor, and the partial pressure of water vapor in an oxidation system is high, so that slagging is easily caused, and the running period of the device is shortened;
2) before the circulating ethylbenzene enters the ethylbenzene oxidation reactor, the heat exchange is carried out between the circulating ethylbenzene and the oxidation tail gas, the temperature difference is about 20 ℃, and the heat of the oxidation tail gas is not fully utilized. Subsequent organic matters recovered by the condensation of the oxidized tail gas are cooled by circulating water and chilled water, so that the circulating water amount is large, and the heat recovery of the oxidized tail gas is insufficient.
3) The oxidation tail gas contains non-condensable gas such as N2 and the like, the heat transfer coefficient is small, and the area of a heat exchanger required by cooling is large. When the load of the oxidation reaction part fluctuates, particularly under the nitrogen purging working condition, the ethylbenzene loss is large.
4) The consumption of heating steam for circulating the ethylbenzene to the oxidation reactor is large.
5) The consumption of hot water for preheating ethylbenzene is large.
Disclosure of Invention
The invention provides a system and a method for treating tail gas of ethylbenzene oxidation reaction aiming at the existing technical problems.
A system for treating tail gas of ethylbenzene oxidation reaction comprises a direct heat exchange tower, wherein the output end of oxidation tail gas is connected with the lower part of the direct heat exchange tower, the output end of the top of the direct heat exchange tower is connected with the lower part of a cooling washing tower, output pipelines of ethylbenzene are respectively connected with the middle part and the upper part of the cooling washing tower, an ethylbenzene water separator is arranged at the bottom of the cooling washing tower, and one output end of the ethylbenzene water separator is connected with the upper part of the direct heat exchange tower through a direct heat exchange tower feeding heater; the output end of the top of the cooling washing tower is connected with the lower part of the tail gas absorption tower.
The technical scheme of the invention is as follows: the output pipeline of the ethylbenzene is connected with the upper part of the cooling washing tower through a circulating ethylbenzene deep cooler.
The technical scheme of the invention is as follows: the bottom of the direct heat exchange column was connected to the ethylbenzene feed to the oxidation reactor via an oxidation feed heater.
The technical scheme of the invention is as follows: the output end of the bottom of the tail gas absorption tower and the output end of the absorption liquid containing ethylbenzene are both connected with the absorption liquid cooler and the middle part of the tail gas absorption tower; the absorption liquid enters an absorption liquid cooler on the upper part of the tail gas absorption tower to be cooled and reduced in temperature, and the coolant can adopt liquid ammonia, propylene and the like, is gasified and evaporated to provide cold or adopts low-temperature chilled water and the like to provide cold. The supply amount of the controlled cooling capacity is adjusted according to the temperature of the absorption liquid at the outlet of the absorption liquid cooler, and the outlet temperature of the upper part of the tail gas absorption tower is maintained to be about 20 ℃. And monitoring the temperature of the middle part of the tail gas absorption tower. When the temperature is high, the absorption liquid cooler and the externally supplied cold quantity are increased, otherwise, the cold quantity is reduced.
A method for realizing the treatment of the tail gas of the ethylbenzene oxidation reaction by using the system comprises the following steps:
the first step is as follows: the ethylbenzene oxidation tail gas with the temperature of 130-150 ℃ enters the bottom of a direct heat exchange tower, countercurrent direct heat exchange is carried out on the ethylbenzene oxidation tail gas with the temperature of 70-90 ℃ entering the tower top, the temperature of the ethylbenzene is increased, the temperature of the oxidation tail gas is reduced, part of the ethylbenzene in the oxidation tail gas is condensed into a liquid phase, the liquid phase and the heated ethylbenzene reach the tower bottom together, the liquid phase is pressurized by an oxidation reaction feed pump and sent to an oxidation feed heater to be heated to about 145-155 ℃, and the ethylbenzene is discharged from the oxidation feed heater and fed into a first-stage ethylbenzene oxidation reactor;
the second step is that: reducing the temperature in a direct heat exchange tower, recovering heat and partial ethylbenzene to obtain oxidized tail gas at 70-90 ℃, and cooling the oxidized tail gas to the bottom of a washing tower; the ethylbenzene is a mixture of circulating ethylbenzene and new ethylbenzene, the temperature is 38-42 ℃, the ethylbenzene is divided into two streams, one stream is sent to the middle of a cooling washing tower, the other stream is cooled to 15-20 ℃ in a circulating ethylbenzene deep cooler and is sent to the top of the cooling washing tower to be used as a cooling washing medium of ethylbenzene oxidation tail gas, the ethylbenzene and water in the tail gas are condensed and liquefied due to temperature reduction and reach the bottom of the washing tower, the ethylbenzene and the water are separated by an ethylbenzene water separator, in the ethylbenzene water separator, the ethylbenzene is located at the upper layer and is located at the lower layer, the lower layer of water is used as wastewater to be treated, the upper layer of ethylbenzene is pressurized by a circulating ethylbenzene pump and is sent to a feeding heater of a direct heat exchange tower;
the third step: removing the bottom of a tail gas absorption tower, feeding fresh absorption liquid into an absorption liquid cooler to reduce the temperature to 15-20 ℃, feeding the fresh absorption liquid into the top of the tail gas absorption tower, and carrying out countercurrent absorption on the organic matters in the oxidized tail gas;
the absorption liquid at the bottom of the tail gas absorption tower contains organic matters, the organic matters are pressurized by an absorbent circulating pump and then are sent to an absorption liquid cooler to be cooled to the temperature of 15-20 ℃, the absorption liquid is sent to the middle part of the tail gas absorption tower, the absorbent circulating pump pumps out a pipeline which holds ethylbenzene absorption liquid to discharge part of the absorption liquid at the bottom of the absorption tower so as to maintain the absorption effect of the absorption tower, and the discharged tail gas 20 at the top of the absorption tower is removed to a tail gas treatment device.
The technical scheme of the invention is as follows: the fresh absorption liquid is phenethyl alcohol.
The invention has the beneficial effects that:
1) light components and water in the circulating ethylbenzene are not easy to bring into an oxidation reactor, the partial pressure of water vapor in an oxidation system is low, slagging is reduced, and the running period of the device is prolonged;
2) before the circulating ethylbenzene enters the ethylbenzene oxidation reactor, directly mixing the circulating ethylbenzene with the oxidized tail gas for heat exchange, and fully recovering the heat of the oxidized tail gas;
3) the consumption of the heating steam of the circulating ethylbenzene entering the oxidation reactor is low. The consumption of the heating hot water is small;
4) the adaptability of the load fluctuation of the oxidation device is strong;
5) the online rate of the device is high;
6) a tail gas heat exchanger is cancelled, most of the adopted heat exchangers exchange heat through liquid, the heat transfer coefficient is large, and the area of the heat exchangers is small;
7) the consumption of circulating cooling, freezing water and preheating hot water is low;
the method has the advantages of optimizing ethylbenzene oxidation conditions, high energy recovery efficiency of oxidized tail gas and low consumption of public works.
Drawings
FIG. 1 is a schematic view of the process flow of the system for treating tail gas from ethylbenzene oxidation reaction.
Wherein: 1-direct heat exchange tower, 2-cooling washing tower, 3-tail gas absorption tower, 4-direct heat exchange tower feeding heater, 5-circulating ethylbenzene deep cooler, 6-tower top tail, 7-first absorption liquid cooler, 8-second absorption liquid cooler, 9-oxidation feeding heater, 10-oxidation reaction feeding pump, 11-circulating ethylbenzene pump, 12-ethylbenzene water separator, 13-absorbent circulating pump, 14-fresh absorption liquid, 15-oxidation tail gas, 16-oxidation reactor ethylbenzene feeding, 17-waste water, 18-ethylbenzene, 19-ethylbenzene-containing absorption liquid, and 20-exhaust tail gas.
FIG. 2 is a schematic process flow diagram of a system for treating tail gas from an ethylbenzene oxidation reaction in a comparative example.
Wherein: 201-oxidized tail gas cooler, 202-oxidized tail gas water cooler, 203-oxidized tail gas salt cooler, 204-circulating ethylbenzene preheater, 205-circulating ethylbenzene heater, 206-oxidized tail gas, 207-circulating water, 208-chilled water, 209-discharged tail gas, 2010-circulating ethylbenzene, 2011-hot water, 2012-oxidized reactor ethylbenzene feed, 2013-steam, 2014-condensate, 2015-condensate
Detailed Description
The invention is further illustrated by the following examples, without limiting the scope of the invention:
referring to fig. 1, a system for treating tail gas of ethylbenzene oxidation reaction comprises a direct heat exchange tower 1, wherein an output end of an oxidation tail gas 15 is connected with the lower part of the direct heat exchange tower 1, an output end of the top of the direct heat exchange tower 1 is connected with the lower part of a cooling washing tower 2, output pipelines of ethylbenzene are respectively connected with the middle part and the upper part of the cooling washing tower 2, an ethylbenzene water separator 12 is arranged at the bottom of the cooling washing tower 2, and an output end of the ethylbenzene water separator is connected with the upper part of the direct heat exchange tower 1 through a direct heat exchange tower feeding heater 4; the output end of the top of the cooling washing tower 2 is connected with the lower part of the tail gas absorption tower 3. An output pipeline of the ethylbenzene is connected with the upper part of the cooling washing tower 2 through a circulating ethylbenzene deep cooler 5. The bottom of the direct heat exchange column 1 is connected to an oxidation reactor ethylbenzene feed 16 via oxidation feed heater 9. The output end of the bottom of the tail gas absorption tower 3 and the output end of the absorption liquid containing ethylbenzene are both connected with the absorption liquid cooler 8 and the middle part of the tail gas absorption tower 3.
The absorption liquid enters an absorption liquid cooler 7 at the upper part of the tail gas absorption tower 3 to be cooled, the coolant can adopt liquid ammonia, propylene and the like, the gasification and evaporation provide cold energy, and low-temperature chilled water and the like can also be adopted to provide cold energy. The supply amount of the controlled cooling capacity is adjusted according to the temperature of the absorption liquid at the outlet of the absorption liquid cooler 7, the supply amount of the controlled cooling capacity is adjusted according to the temperature of the absorption liquid at the outlet of the absorption liquid cooler 8, and the outlet temperature of the upper part of the tail gas absorption tower 3 is maintained to be about 20 ℃.
The temperature in the middle of the tail gas absorption tower 3 is monitored. When the temperature is high, the externally supplied cold capacity of the absorption liquid coolers 7 and 8 is increased, and conversely, the cold capacity is reduced.
The method for realizing the treatment of the tail gas of the ethylbenzene oxidation reaction by using the system comprises the following specific steps:
the oxidation tail gas process parameters were as follows (exactly the same as the comparative example):
| mainly comprising | Unit of | Ethylbenzene, nitrogen, water, etc |
| Fraction of gas phase | 1.0000 | |
| Phase state | Gas phase | |
| Temperature of | C | 147.73 |
| Pressure of | kPa | 365 |
| Molar flow rate | kgmole/h | 2170.88 |
| Mass flow rate | kg/h | 122857.35 |
The amount of the recycled ethylbenzene entering the oxidation reactor is 335t/h, and the ethylbenzene source is the sum of the ethylbenzene (85.1t/h) in the recycled oxidation tail gas and the recycled ethylbenzene (249.9 t/h).
The oxidized tail gas exchanges heat with circulating ethylbenzene at 70 ℃ in a direct heat exchange tower, the temperature of the oxidized tail gas discharged from the top of the direct heat exchange tower is reduced to 71.4 ℃, the temperature of the circulating ethylbenzene discharged from the bottom of the direct heat exchange tower is increased to 131 ℃, the flow of the circulating ethylbenzene discharged from a deoxidation reactor at the bottom of the direct heat exchange tower is 335t/h, the oxidized tail gas is heated to 155 ℃ by steam in an oxidation feed heater and enters a first-stage oxidation reactor, the heating steam amount of the oxidation feed heater is 8.953t/h, and the heat load is 4971 kW. About 79.52t/h of the liquid ethylbenzene recovered from the tail gas in the direct heat exchange column reached 131 ℃ without the temperature reduction and temperature increase process of the prior art.
Cooling a part of 71.7t/h of 40 ℃ circulating ethylbenzene in a circulating ethylbenzene deep cooler to 20 ℃ by using 7 ℃ chilled water, wherein the consumption of the chilled water is 163.2t/h, the heat load of the circulating ethylbenzene deep cooler is 682kW, and feeding the cooled water to the top of a cooling washing tower; the remaining 178.2t/h was passed directly into the middle of the cooling scrubber. The temperature of the oxidation tail gas at the tower top is controlled to be 22.3 ℃ by the tower top cold circulation ethylbenzene flow.
And (3) passing the tower bottom liquid of the cooling washing tower through an ethylbenzene-water separator, separating out a water phase, sending the water phase to sewage treatment, heating the separated circulating ethylbenzene to 70 ℃ by a direct heat exchange tower feeding heater through hot water, and sending the heated circulating ethylbenzene to the top of the direct heat exchange tower. The heat load of the direct heat exchange tower feeding heater is 3020kW, and the hot water consumption is 259.35 t/h.
Removing the bottom of a tail gas absorption tower, feeding fresh absorption liquid phenethyl alcohol into an absorption liquid cooler to reduce the temperature to 15-20 ℃, feeding the fresh absorption liquid phenethyl alcohol into the top of the tail gas absorption tower, and performing countercurrent absorption on the organic matters in the oxidized tail gas;
the absorption liquid at the bottom of the tail gas absorption tower contains organic matters, the organic matters are pressurized by an absorbent circulating pump and then are sent to an absorption liquid cooler to be cooled to the temperature of 15-20 ℃, the absorption liquid is sent to the middle part of the tail gas absorption tower, the absorbent circulating pump pumps out a pipeline which holds ethylbenzene absorption liquid to discharge part of the absorption liquid at the bottom of the absorption tower so as to maintain the absorption effect of the absorption tower, and the discharged tail gas 20 at the top of the absorption tower is removed to a tail gas treatment device.
Comparative example
The comparative example process is as follows:
as shown in fig. 2, the oxidized tail gas 206 enters the oxidized tail gas cooler 201 to exchange heat with the preheated circulating ethylbenzene, the temperature of the oxidized tail gas is reduced, the oxidized tail gas water cooler 202 is cooled by circulating cooling water 207, the oxidized tail gas salt cooler 203 is cooled by chilled water 208, condensate 2014 and condensate 2015 of the oxidized tail gas water cooler 202 and the oxidized tail gas salt cooler 203 are mainly ethylbenzene, and the discharged tail gas 209 is subjected to a subsequent treatment process (tail gas absorption tower).
The circulating ethylbenzene 2010 is firstly heated by hot water 2011 in a circulating ethylbenzene preheater 204, then the circulating ethylbenzene 2010 exchanges heat with the oxidation tail gas 206 through an oxidation tail gas cooler 201, and finally the circulating ethylbenzene 2010 is heated to 155 ℃ by steam in a circulating ethylbenzene heater 205 and enters an oxidation reactor
An apparatus was operated as follows according to the comparative example:
the technological parameters of the oxidation tail gas are as follows:
the 40 ℃ recycle ethylbenzene (335t/h) was first heated in a recycle ethylbenzene preheater to 70 ℃ with hot water at a heat duty of 5199kW and a hot water consumption of 445.62 t/h. Then circulating ethylbenzene at 70 ℃ exchanges heat with the oxidation tail gas through an oxidation tail gas cooler, the heat load is 10210kW, the temperature of the circulating ethylbenzene is heated to 125 ℃, finally the circulating ethylbenzene is heated to 155 ℃ by steam in a circulating ethylbenzene heater and enters an oxidation reactor, the steam consumption is 10.86t/h, and the heat load is 6024 kW.
And the oxidized tail gas passes through an oxidized tail gas cooler, the temperature is reduced to 89.3 ℃, then the oxidized tail gas enters an oxidized tail gas water cooler, the oxidized tail gas is cooled to 43 ℃ by using circulating water, and finally the oxidized tail gas passes through an oxidized tail gas salt cooler, is cooled to 22.3 ℃ by using frozen water at 7 ℃, and then is removed from a tail gas treatment device. The circulating water dosage is 166.55t/h, and the freezing water dosage is 142.5 t/h.
According to the method, the feeding ethylbenzene is heated to the same temperature as that of the comparative example and enters the oxidation reactor, the tail gas is cooled to the same temperature and enters the tail gas absorption tower, the recovery rate of the ethylbenzene in the tail gas is the same, but the difference of the heat recovery in the tail gas is larger, the technology can obtain obvious energy-saving effect, and the consumption of public works of the embodiment and the comparative example is compared as follows:
public work consumption comparison table
From the comparison, it can be seen that the economic benefit of the technology is more than 12491 ten thousand per year compared with the prior art according to the scale of tail gas treatment by the comparison device.
(calculated according to tax-bearing prices: 136 yuan/ton of steam, 2.5 yuan/ton of chilled water, 7 yuan/ton of hot water and 0.3 yuan/ton of circulating water).
If the temperature of liquid ethylbenzene recovered from tail gas reaches 131 ℃ at about 79.52t/h in the direct heat exchange tower, the energy-saving effect is more remarkable without the process of reducing the temperature and then increasing the temperature in the comparative process.
Claims (6)
1. A processing system of ethylbenzene oxidation reaction tail gas which characterized in that: the system comprises a direct heat exchange tower (1), wherein the output end of oxidation tail gas (15) is connected with the lower part of the direct heat exchange tower (1), the output end of the top of the direct heat exchange tower (1) is connected with the lower part of a cooling washing tower (2), the output pipeline of ethylbenzene is respectively connected with the middle part and the upper part of the cooling washing tower (2), an ethylbenzene water separator (12) is arranged at the bottom of the cooling washing tower (2), and one output end of the ethylbenzene water separator is connected with the upper part of the direct heat exchange tower (1) through a direct heat exchange tower feeding heater (4); the output end of the top of the cooling washing tower (2) is connected with the lower part of the tail gas absorption tower (3).
2. The system for processing an ethylbenzene oxidation reaction off-gas according to claim 1, wherein: the output pipeline of the ethylbenzene is connected with the upper part of the cooling washing tower (2) through a circulating ethylbenzene deep cooler (5).
3. The system for processing an ethylbenzene oxidation reaction off-gas according to claim 1, wherein: the bottom of the direct heat exchange column (1) is connected to the oxidation reactor ethylbenzene feed (16) via oxidation feed heater (9).
4. The system for processing an ethylbenzene oxidation reaction off-gas according to claim 1, wherein: the output end of the bottom of the tail gas absorption tower (3) and the output end of the absorption liquid containing ethylbenzene are both connected with the absorption liquid cooler (8) and the middle part of the tail gas absorption tower (3); the output pipeline of the absorption liquid is connected with the upper part of the tail gas absorption tower (3) through an absorption liquid cooler (7).
5. A method for processing tail gas of ethylbenzene oxidation reaction by using the system of claim 1, which is characterized by comprising the following steps: the method comprises the following steps:
the first step is as follows: the method comprises the following steps that ethylbenzene oxidation tail gas (15) with the temperature of 130-150 ℃ enters the bottom of a direct heat exchange tower (1), countercurrent direct heat exchange is carried out on the ethylbenzene oxidation tail gas with the temperature of 70-90 ℃ entering the tower top, the temperature of the ethylbenzene is increased, the temperature of the oxidation tail gas is reduced, part of the ethylbenzene in the oxidation tail gas is condensed into a liquid phase, the liquid phase and the heated ethylbenzene reach the tower bottom together, an oxidation reaction feed pump (10) is used for pressurizing and sending the liquid phase to an oxidation feed heater (9) to heat to 145-155 ℃, and the ethylbenzene feed (16) out of the oxidation feed heater (9) is sent to a first-;
the second step is that: reducing the temperature in the direct heat exchange tower (1), recovering heat and partial oxidation tail gas of ethylbenzene, cooling the oxidation tail gas at the bottom of the washing tower (2) at the temperature of 70-90 ℃; the ethylbenzene (18) is a mixture of circulating ethylbenzene and new ethylbenzene, the temperature is 38-42 ℃, the ethylbenzene is divided into two streams, one stream is sent to the middle of the cooling washing tower (2), the other stream is cooled to 15-20 ℃ in the circulating ethylbenzene deep cooler (5) and sent to the top of the cooling washing tower (2) to serve as a cooling washing medium of ethylbenzene oxidation tail gas, the ethylbenzene and water in the tail gas are condensed and liquefied due to temperature reduction and reach the bottom of the tower, the ethylbenzene and the water are separated in the ethylbenzene water separator (12), the ethylbenzene is located at the upper layer and water is located at the lower layer in the ethylbenzene water separator (12), the lower layer of water serves as waste water (17) to be treated, the upper layer of ethylbenzene is pressurized by a circulating ethylbenzene pump (11) and sent to a direct heat exchange tower feeding heater (4) to be heated to 70-90 ℃, and then is sent;
the third step: the oxidized tail gas discharged from the top of the cooling washing tower (2) also contains a small amount of organic matters, the bottom of the tail gas absorption tower (3) is removed, fresh absorption liquid (14) is firstly introduced into the absorption liquid cooler (7) to reduce the temperature to 15-20 ℃, and the oxidized tail gas enters the top of the tail gas absorption tower to reversely absorb the organic matters in the oxidized tail gas;
the absorption liquid at the bottom of the tail gas absorption tower (3) contains organic matters, the absorption liquid is pressurized by an absorbent circulating pump (13) and then is sent to an absorption liquid cooler (8) to be cooled to the temperature of 15-20 ℃, and then is sent to the middle part of the tail gas absorption tower (3), a pipeline containing ethylbenzene absorption liquid (19) at the outlet of the absorbent circulating pump (13) discharges part of the absorption liquid at the bottom of the absorption tower so as to maintain the absorption effect of the absorption tower, and the discharged tail gas 20 at the top of the absorption tower is removed to a tail gas treatment device.
6. The method of claim 5, wherein: the fresh absorption liquid is phenethyl alcohol.
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| CN202010876039.5A CN111995489B (en) | 2020-08-25 | 2020-08-25 | System and method for treating tail gas of ethylbenzene oxidation reaction |
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