CN113509811A - Method and system for treating tail gas containing chloropropene and oxygen - Google Patents
Method and system for treating tail gas containing chloropropene and oxygen Download PDFInfo
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- B01D53/228—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion characterised by specific membranes
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Abstract
The invention relates to the field of safe treatment of tail gas, and discloses a method for treating tail gas containing chloropropene and oxygen, which comprises the following steps: (1) carrying out first cooling on the tail gas to obtain a first cooling gas and a first cooling liquid, wherein the chloropropene content in the first cooling gas is 10-30% by volume; (2) mixing the first cooling gas with inert gas to obtain mixed gas; (3) and carrying out second cooling on the mixed gas to obtain a second cooling gas and a second cooling liquid, wherein the chloropropene content in the second cooling gas is not more than 0.3 volume percent. The tail gas contains chloropropene, oxygen, water vapor and optional epichlorohydrin. The method realizes resource recycling, reduces production cost, has the advantages of zero emission, no pollution and higher economic benefit, and is suitable for large-scale industrial application.
Description
Technical Field
The invention relates to the field of tail gas treatment containing chloropropene and oxygen, in particular to a tail gas treatment method containing chloropropene and oxygen and a system thereof.
Background
The current process routes for producing epichlorohydrin mainly comprise a propylene high-temperature chlorination method, an acetate propylene ester method, a glycerin method and other process routes. However, the conventional production process generates a large amount of organic pollutants, and is not environment-friendly. Meanwhile, with the gradual improvement of environmental protection requirements in recent years, the demand of people on green chemical industry is gradually enhanced, and hydrogen peroxide is applied to the chemical industry more and more widely as an environment-friendly oxidant.
The epoxy chloropropane can be prepared by oxidizing chloropropene with hydrogen peroxide, and the reaction steps are simple and environment-friendly. However, the method has certain defects, for example, the chloropropene content in the tail gas after the oxidation reaction is high, in the subsequent condensation process, the chloropropene is condensed, and then the oxygen in the tail gas is gradually enriched as the non-condensable gas, and if the tail gas composition enters the chloropropene-oxygen explosion limit area at a certain moment, the consequence is not reasonable.
CN109734589A discloses a method for improving safety of epichlorohydrin tail gas, which comprises the step of directly introducing the tail gas after reaction into a pressurized sodium phthalate aqueous solution to react with chloropropene in the tail gas. However, the method has complicated steps, needs to strictly control reaction conditions, and simultaneously needs to additionally arrange a reactor and separation equipment in industrial production, thereby having the problems of complicated operation and large equipment investment.
CN109867585A discloses a waste gas treatment method in the reaction process of preparing epichlorohydrin by chloropropene, which comprises introducing waste gas into an absorption tower, filling epichlorohydrin into a tower kettle in advance, enabling the epichlorohydrin to form low-temperature cyclic absorption of chloropropene, sending the mixture obtained after absorption to a rectification section for distillation, discharging the gas phase obtained after condensation through an emptying pipeline at the upper part of the tower top of the absorption tower, and continuously taking measures to recover chloropropene in the waste gas. Therefore, the method also has the problems of complicated operation steps and large equipment investment, and has low economic benefit in industrial application.
Therefore, in order to solve the potential safety hazard in the tail gas treatment of the process for preparing epoxy chloropropane and overcome the contradiction between the environmental protection pressure and the equipment investment in the method, the research and development of a novel process which is safe, effective, simple in treatment method and environment-friendly is urgently needed.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a tail gas treatment method containing chloropropene and oxygen and a system thereof.
In order to achieve the above object, a first aspect of the present invention provides a method for treating off-gas containing chloropropene and oxygen, comprising:
(1) carrying out first cooling on the tail gas to obtain a first cooling gas and a first cooling liquid, wherein the chloropropene content in the first cooling gas is 10-30% by volume;
(2) mixing the first cooling gas with inert gas to obtain mixed gas;
(3) carrying out second cooling on the mixed gas to obtain a second cooling gas and a second cooling liquid, wherein the chloropropene content in the second cooling gas is not more than 0.3 volume percent;
the tail gas contains chloropropene, oxygen, water vapor and optional epichlorohydrin.
Preferably, the chloropropene content of the tail gas is 50-80 vol%, and the oxygen content is 2-8 vol%.
In a second aspect, the present invention provides a tail gas treatment system containing chloropropene and oxygen, comprising:
the reactor, the first cooling device, the second cooling device and the gas-liquid separation device are sequentially communicated, and a gas phase outlet of the reactor is communicated with an inlet of the first cooling device;
the system also comprises an inert gas introducing pipeline arranged on a communication pipeline between the gas phase outlet of the first cooling device and the second cooling device, so that the first cooling gas obtained by the first cooling device is mixed with the inert gas.
According to the technical scheme, the method adopts two steps of control, wherein the explosion upper limit control is adopted, namely the chloropropene content in the tail gas is controlled to be higher than the explosion upper limit of chloropropene under the working condition through first cooling, and the limit oxygen content control is adopted, namely inert gas is introduced into the tail gas after the first cooling, so that the oxygen content is lower than the required explosion amount, and the safety of the tail gas treatment process is ensured. Compared with the method for directly mixing the tail gas with a large amount of inert gas for explosion suppression, the method disclosed by the invention saves the consumption of the inert gas, avoids filling a large amount of inert gas, reduces the energy consumption and reduces the environmental protection pressure. Meanwhile, under the optimal condition, the liquid inert gas obtained by the gas separation device is recycled, and the condensate containing chloropropene and epoxy chloropropane is returned to the reactor to be used as a raw material, so that the resource recycling is realized, and the method has the advantages of zero emission, no pollution and higher economic benefit, and is suitable for large-scale industrial application.
Drawings
FIG. 1 is a process flow diagram of a tail gas treatment process provided by the present invention in example 1;
FIG. 2 is a ternary diagram of the explosive limits of chloropropenes in example 1.
Description of the reference numerals
1. Reactor 4, liquid inert gas storage tank 5 and heat exchanger
7. The gas separation device 11 and the membrane separation devices 13 and 14 are both coolers
2. 3, 6, 8, 9, 10 and 12 are pipelines
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
In the present invention, the explosion limit refers to that under the test conditions, the combustible and the gaseous oxidant are uniformly mixed in a certain concentration range to form a homogeneous mixture, and the homogeneous mixture is exploded when meeting an ignition source, and the concentration range is called as the explosion limit. The upper explosive limit refers to the maximum combustible concentration that enables the flame to propagate in a homogeneous mixture of combustible and gaseous oxidant under the test conditions, and the lower explosive limit refers to the minimum combustible concentration that enables the flame to propagate in a homogeneous mixture of combustible and gaseous oxidant under the test conditions.
In the present invention, the limit oxygen content refers to the minimum oxygen content required for the flamed combustion of a combustible in an oxygen-containing gas mixture under the test conditions.
Unless otherwise specified, the pressure in the present invention refers to the absolute pressure. The normal pressure in the present invention means one atmospheric pressure.
The invention provides a method for treating tail gas containing chloropropene and oxygen, which comprises the following steps:
(1) carrying out first cooling on the tail gas to obtain a first cooling gas and a first cooling liquid, wherein the chloropropene content in the first cooling gas is 10-30% by volume;
(2) mixing the first cooling gas with inert gas to obtain mixed gas;
(3) carrying out second cooling on the mixed gas to obtain a second cooling gas and a second cooling liquid, wherein the chloropropene content in the second cooling gas is not more than 0.3 volume percent;
the tail gas contains chloropropene, oxygen, water vapor and optional epichlorohydrin.
According to the invention, by strictly controlling the chloropropene content in the step (1), not only is safe operation realized, but also energy conservation and consumption reduction are realized.
In the present invention, the optional epichlorohydrin means that the tail gas may or may not contain epichlorohydrin. The method of the invention is suitable for treating tail gas containing chloropropene and oxygen, including but not limited to tail gas generated in a process for preparing epoxy chloropropane by adopting chloropropene. When the treated tail gas comes from a process for preparing epichlorohydrin by chloropropene, the tail gas usually also contains epichlorohydrin.
According to the invention, the selection range of the content of chloropropene and oxygen in the tail gas is wide, preferably, the content of chloropropene in the tail gas is 50-80 volume percent, and the content of oxygen is 2-8 volume percent.
When the tail gas is generated in a process of preparing epoxy chloropropane from chloropropene, the content of the epoxy chloropropane in the tail gas is preferably 0.1-10 vol%.
According to the invention, said first cooling will remove part of the chloropropenes and water vapour in the off-gas.
According to the present invention, the temperature of the first cooling gas is preferably 3 to 30 ℃, more preferably 5 to 20 ℃. In this preferable case, after the first cooling, it is beneficial to ensure the safety of the process, so that the content of chloropropene in the first cooling gas is above the upper explosion limit.
According to the present invention, preferably, the pressure of the first cooling gas is 0.01 to 0.2 MPa.
The content of the chloropropene in the first cooling gas is selected in a wide range, and in a preferred embodiment, the content of the chloropropene in the first cooling gas is 10-20 vol%. Under the preferred embodiment, when the first cooling gas is mixed with the inert gas, the using amount of the inert gas is less, so that the safety of the tail gas treatment process is ensured, the energy consumption is reduced, and the economic benefit is improved.
According to the present invention, preferably, the content of oxygen in the first cooling gas is 10 to 30% by volume.
The first cooling is not particularly limited in the present invention, and in order to secure the cooling effect, the first cooling is preferably two-stage cooling or multi-stage cooling in series. The cooling apparatus of the present invention is not particularly limited, and specifically, it may be carried out using a cooler. The cooler is not particularly limited in the present invention, as long as the purpose of reducing the temperature of the tail gas to reduce the gas volume content of chloropropene in the tail gas can be achieved.
According to the invention, the cold source of the cooler is preferably selected from liquid inert gas and/or frozen brine, preferably frozen brine.
The frozen brine may be a conventional choice in the art, and preferably, the salt is selected from at least one of sodium chloride, sodium sulfate, potassium chloride, and potassium sulfate.
The method for providing the refrigeration capacity for the frozen brine is not particularly limited, and specifically, the lithium bromide refrigerant can be used for providing the refrigeration capacity for the frozen brine, and the refrigeration capacity can also be provided for the frozen brine by performing countercurrent heat exchange on the heat exchanger and the frozen brine. The heat exchanger is not particularly limited in the present invention, and may be a conventional one in the art, for example, a shell-and-tube heat exchanger.
In one embodiment, the series two-stage cooling in the first cooling is two coolers connected in series, and the series multi-stage cooling is a plurality of coolers connected in series.
In one embodiment, the series multistage cooling may also employ a plurality of coolers in series side by side for the first cooling.
According to the present invention, it is preferable that in the step (2), the content of oxygen in the mixed gas is not more than 10% by volume.
According to a preferred embodiment of the present invention, in the step (2), the content of oxygen in the mixed gas is 4 to 10% by volume. In this preferred embodiment, the inert gas is used in a smaller amount, and the process is more economically efficient while ensuring the safety of the tail gas treatment process.
According to the present invention, preferably, the inert gas is at least one of nitrogen, helium, neon and argon, preferably nitrogen.
In one embodiment, in the present invention, the amount of nitrogen gas mixed with said first cooling gas is determined with reference to the ternary diagram of the explosion limit of chloropropenes as shown in fig. 2, determined with reference to BS EN1839-2017 combustible gas and vapour explosion limit and Limiting Oxygen Concentration (LOC) standards.
As shown in fig. 2, the upper explosion limit and the lower explosion limit of chloropropene at different oxygen concentrations are obtained through testing, so that an explosion limit triangular region surrounded by the lower explosion limit and the upper explosion limit is obtained, and the gas composition in the region has an explosion risk. Specifically, in fig. 2, the abscissa represents the volume fraction of nitrogen, the left ordinate represents the volume fraction of oxygen, and the right ordinate represents the volume fraction of chloropropene. The chloropropene content in the tail gas far exceeds the upper explosion limit, but most of chloropropene and water vapor in the tail gas are removed along with the first cooling, the chloropropene content gradually decreases, oxygen as the non-condensable gas content gradually increases, and finally the chloropropene content can decrease to the upper explosion limit concentration, so that the chloropropene content enters the explosion limit range and is reflected in that the chloropropene content moves from a point A to a point B on an explosion limit ternary diagram.
In a specific embodiment, the test shows that the upper explosion limit (point B) of the chloropropene under the working condition is 12-30 vol%, in order to ensure that the tail gas composition does not enter an explosion limit region, the temperature of the first cooling gas is 20-30 ℃, the first cooling gas and nitrogen are mixed to obtain a mixed gas, and the test shows that the limit oxygen content of the system is 6-12 vol%, so that the consumption of the nitrogen is required to dilute the oxygen content in the mixed gas to 4-10 vol%, and the oxygen content is represented to move from the point B to the point D in an explosion limit ternary diagram.
According to the invention, preferably, the chloropropene content of the second cooling gas is not more than 0.1% by volume.
According to the present invention, preferably, the content of oxygen in the second cooling gas is not more than 10 vol%, and more preferably, 5 to 10 vol%.
The second cooling is not particularly limited in the present invention, and in order to secure the cooling effect, the second cooling is preferably two-stage cooling or multi-stage cooling in series.
In one embodiment, the series two-stage cooling in the second cooling is two coolers connected in series, and the series multi-stage cooling is a plurality of coolers connected in series.
In one embodiment, the series multi-stage cooling may further employ a plurality of coolers in series side by side for the second cooling.
The selection range of the equipment adopted by the second cooling is wider, and specifically, the equipment can be a cooler, and the selection of the cooler is as described above, and is not described again.
The selection range of the cold source in the second cooling can be as described above, and can be the same as the selection range of the cold source in the first cooler, and details are not repeated here.
In one embodiment, in order to further improve the economic efficiency while ensuring the cooling effect, the cold source in the second cooling is more preferably frozen brine. The choice of the chilled brine and the first cooling is not repeated here.
Preferably, the temperature of the second cooling gas is-10 ℃ to 5 ℃, and the pressure is 0.01 MPa to 0.2 MPa.
According to a preferred embodiment of the invention, the method further comprises: and sequentially carrying out membrane separation and gas separation on the second cooling gas to obtain liquid inert gas. According to the present invention, the apparatus for performing the membrane separation is not particularly limited, and the type of the membrane is selected from a wide range as long as the purpose of passing the inert gas and the oxygen in the second cooling gas without passing the chloropropene and/or the epichlorohydrin is achieved.
Preferably, the chloropropene and/or epichlorohydrin obtained by the membrane separation device is collected and recycled as a reaction raw material. Under the optimal condition, the method is beneficial to realizing resource recovery and realizing the purpose of zero emission.
The apparatus for separating the gas is not particularly limited in the present invention, as long as the inert gas in the second cooling gas can be converted into a liquid state to obtain a liquid inert gas.
According to the invention, preferably, the inert gas is nitrogen. In this preferred case, it is more advantageous to reduce the cost of the tail gas treatment.
In one embodiment, the method further comprises: and exchanging heat between the liquid inert gas and the cold source for the second cooling to obtain the inert gas after heat exchange and the cold source after heat exchange.
According to the present invention, preferably, in the step (2), at least a part of the inert gas is provided by the inert gas after heat exchange. Under the preferable condition, the liquid inert gas obtained by air separation of the inert gas in the second cooling gas is recycled, so that the resource recycling is realized, and the environment-friendly purposes of zero emission and no pollution are realized.
In one embodiment, when the cooling capacity is provided to the frozen brine by performing counter-current heat exchange with the frozen brine in the heat exchanger, the medium for providing the cooling capacity is liquid inert gas. The liquid inert gas is preferably the liquid inert gas obtained by the gas separation device. Under the optimal condition, the liquid inert gas is used as a cold source to provide cold for the frozen brine, and simultaneously, the liquid inert gas is heated and converted into the inert gas, and the inert gas is mixed with the first mixed gas, so that the energy consumption in the tail gas treatment process is reduced, and the resource recycling is realized.
According to the invention, preferably, the first cooling liquid and the second cooling liquid are mixed to obtain a condensate, wherein the content of chloropropene in the condensate is 70-80 wt%, and the content of epichlorohydrin is 5-20 wt%. Under the preferable condition, the content of chloropropene and epoxy chloropropane in the condensate accords with the recycling standard, and the condensate is returned to the reactor to be used as a reaction raw material for production, so that the resource recovery is favorably realized, the economic benefit is improved, and the environmental protection aims of zero emission and no pollution are realized.
In a second aspect, the present invention provides a tail gas treatment system containing chloropropene and oxygen, comprising:
the reactor, the first cooling device and the second cooling device are sequentially communicated, and a gas-phase outlet of the reactor is communicated with an inlet of the first cooling device;
the system also comprises an inert gas introducing pipeline arranged on a communication pipeline between the gas phase outlet of the first cooling device and the second cooling device, so that the first cooling gas obtained by the first cooling device is mixed with the inert gas.
According to the invention, in a particular embodiment, the first cooling device and the second cooling device each independently comprise at least two coolers in series. Specifically, there may be two coolers in series, or there may be three or more coolers in series. In the present invention, the selection of the cooler is as described above and will not be described in detail.
According to the present invention, preferably, the system further comprises a gas separation device and a membrane separation device, the gas phase inlet of the membrane separation device is communicated with the gas phase outlet of the second cooling device, and the gas phase outlet of the membrane separation device is communicated with the inlet of the gas separation device.
According to the invention, preferably, the system further comprises a heat exchanger, and the outlet of the gas separation device is communicated with the heat exchanger to provide liquid inert gas for a cold source of the heat exchanger; and the outlet of the heat exchanger is communicated with an inert gas introducing pipeline so as to introduce the inert gas obtained after the liquid inert gas is heated.
The invention is not particularly limited in the way of recycling the liquid inert gas, and in a specific embodiment, the outlet of the gas separation device is communicated with a liquid inert gas storage tank, and the liquid inert gas storage tank provides the liquid inert gas for a cold source of the heat exchanger.
In another embodiment, the outlet of the gas separation device is in direct communication with the heat exchanger to provide refrigeration to the chilled brine in the heat exchanger.
According to a preferred embodiment of the present invention, the method for treating off-gas containing chloropropene and oxygen according to the present invention is carried out according to the process flow diagram shown in fig. 1, and specifically:
tail gas enters a cooler 13 and a cooler 14 which are connected in series from a top gas phase outlet of the reactor 1 through a pipeline 2, and is subjected to first cooling and second cooling respectively, and the tail gas is mixed with the inert gas conveyed through a pipeline 3 after being subjected to the first cooling to obtain mixed gas; the frozen brine enters a heat exchanger 5, exchanges heat with liquid inert gas from a liquid inert gas storage tank 4 to reduce the temperature, and then enters a cooler 14 through a pipeline 12; carrying out second cooling on the mixed gas to obtain second cooling gas; the liquid inert gas is changed into inert gas after passing through a heat exchanger 5 and enters a pipeline 3; the second cooling gas enters a gas separation device 7 from the top of a membrane separation device 11 through a pipeline 10, and the liquid inert gas obtained after air separation enters a liquid inert gas storage tank 4 through a pipeline 8 for recycling; the first cooling liquid from the cooler 13 and the second cooling liquid from the cooler 14 are mixed to obtain a condensate, and the condensate is used as a reaction raw material and is returned to the reactor 1 through a pipeline 9 for reaction.
From the aspects of safety, environmental protection and economic benefit, the invention provides a tail gas treatment method for preparing epoxy chloropropane by using a hydrogen peroxide method, wherein the gas separation device can use the existing equipment in the process flow without increasing new equipment investment. The invention recovers all the materials in the tail gas, realizes the recycling of the materials and has the characteristics of zero emission and no pollution.
The present invention will be described in detail below by way of examples.
In the following examples, the pressure is absolute pressure unless otherwise specified.
Example 1
The tail gas treatment method containing chloropropene and oxygen provided by the invention is adopted to carry out tail gas treatment. The tail gas comprises the following specific components in percentage by weight: chloropropene 78.1 vol%, water vapor 14.9 vol%, and oxygen 5.8 vol%Volume percent, epichlorohydrin is 1.1 volume percent; the temperature of the tail gas in the pipeline 2 is 60 ℃, the pressure is 0.1MPa, and the flow is 1000Nm3/h。
The specific process is carried out according to the process flow provided in fig. 1, and the specific process is as follows:
tail gas enters a cooler 13 and a cooler 14 which are connected in series from a top gas phase outlet of the reactor 1 through a pipeline 2, and is subjected to first cooling and second cooling respectively, and the tail gas is mixed with nitrogen conveyed through a pipeline 3 after being subjected to the first cooling to obtain mixed gas; the frozen brine enters a heat exchanger 5, exchanges heat with liquid nitrogen from a liquid nitrogen storage tank 4 for cooling, and then enters a cooler 14 through a pipeline 12; carrying out second cooling on the mixed gas to obtain second cooling gas; the liquid nitrogen is changed into nitrogen after passing through a heat exchanger 5 and enters a pipeline 3; the second cooling gas enters a gas separation device 7 from the top of a membrane separation device 11 through a pipeline 10, and liquid nitrogen obtained after air separation enters a liquid inert gas storage tank 4 through a pipeline 8 for recycling; the first cooling liquid from the cooler 13 and the second cooling liquid from the cooler 14 are mixed to obtain a condensate, and the condensate is used as a reaction raw material and is returned to the reactor 1 through a pipeline 9 for reaction.
Wherein the temperature of the first cooling gas at the outlet of the cooler 13 is 15 ℃, the chloropropene content in the first cooling gas is 15.5 vol%, the oxygen content is 20 vol%, and the flow rate of the nitrogen mixed with the first cooling gas at the pipeline 3 is 522Nm3H; the oxygen content of the mixed gas was 7.2 vol%; the temperature of the second cooling gas was-2 ℃.
The results of tail gas treatment by the method provided by the invention are as follows:
the chloropropene content in the second cooling gas is 0.1 volume percent, and the oxygen content is 8 volume percent;
the content of chloropropene in the condensate is 75.2 weight percent, and the content of epichlorohydrin is 6.3 weight percent.
Example 2
The same raw materials and the same treatment method as in example 1 were used to treat the off gas.
Wherein the temperature of the first cooling gas at the outlet of the cooler 13 is 15 ℃, and the chlorine in the first cooling gasThe propylene content was 15.5% by volume, the oxygen content was 20% by volume, and the flow rate of nitrogen mixed with the first cooling gas at line 3 was 667Nm3H; the oxygen content of the mixed gas was 8.9% by volume; the temperature of the second cooling gas was-3 ℃.
The results of tail gas treatment by the method provided by the invention are as follows:
the chloropropene content in the second cooling gas is 0.3 volume percent, and the oxygen content is 10 volume percent;
the content of chloropropene in the condensate is 75.4 wt%, and the content of epichlorohydrin is 6.1 wt%.
Comparative example 1
The tail gas treatment was carried out according to the method of example 1 in CN109867585A, and the specific results are shown in table 1 below.
TABLE 1
As can be seen from the results in table 1, in the method for treating tail gas provided in comparative example 1, in order to ensure the safety of the treatment process, a large amount of nitrogen was directly mixed with the tail gas, so that the oxygen content in the tail gas was reduced to a large amount below the limit oxygen content, and the oxygen content before and after adsorption was maintained at about 1.3% by volume. Although the method can ensure safety, the use amount of nitrogen is too large, so that the oxygen content is far lower than the limit oxygen content. Therefore, the process is energy intensive and the process is not cost effective for industrial applications.
As can be seen by comparison, the oxygen content at the vent line in comparative example 1 was 1.3% by volume, whereas the oxygen content in the second cooling gas of the invention was 8%, and if the oxygen content was controlled to 1.3% by volume as in comparative example 1, the flow rate of nitrogen mixed with the first cooling gas at line 3 would increase to about 4400Nm3The amount of nitrogen used was about 8.4 times that of the present invention, i.e., according to the method of comparative example 1.
In the embodiment 1 of the invention, the content of chloropropene in the tail gas is controlled to be above the upper explosion limit of chloropropene under the working condition through the first cooling, and the content of chloropropene gas after the first cooling is obviously reduced, so that the safety of the tail gas treatment process can be ensured only by introducing a small amount of nitrogen into the tail gas after the first cooling, and the content of oxygen is lower than the required explosion amount. Meanwhile, the invention adopts a mode of mixing nitrogen after the first cooling, which is beneficial to reducing the energy consumption of the device. Compared with the method of using a large amount of nitrogen to directly mix with the tail gas in the comparative example 1, the method of the invention has the advantage that the use amount of the nitrogen is greatly reduced. Under the condition of achieving a considerable treatment effect, the tail gas treatment method provided by the invention is more energy-saving and consumption-reducing, and has higher economic benefit.
From the results, the method for treating the tail gas containing the chloropropene and the oxygen, provided by the invention, has the advantages of low consumption of the inert gas, reduction in treatment cost, realization of resource recycling, zero emission and no pollution.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (15)
1. A method for treating tail gas containing chloropropene and oxygen, which comprises the following steps:
(1) carrying out first cooling on the tail gas to obtain a first cooling gas and a first cooling liquid, wherein the chloropropene content in the first cooling gas is 10-30% by volume;
(2) mixing the first cooling gas with inert gas to obtain mixed gas;
(3) and carrying out second cooling on the mixed gas to obtain a second cooling gas and a second cooling liquid, wherein the chloropropene content in the second cooling gas is not more than 0.3 volume percent.
The tail gas contains chloropropene, oxygen, water vapor and optional epichlorohydrin.
2. The process of claim 1, wherein the off-gas has a chloropropene content of 50-80 vol% and an oxygen content of 2-8 vol%.
3. A process according to claim 1 or 2, wherein the chloropropene content of the first cooling gas is from 10 to 20% by volume.
4. A method according to any one of claims 1-3, wherein the temperature of the first cooling gas is 3-30 ℃, preferably 5-20 ℃;
preferably, the first cooling is a two-stage cooling or a multi-stage cooling in series.
5. The process according to any one of claims 1 to 4, wherein the inert gas is at least one of nitrogen, helium, neon and argon, preferably nitrogen;
preferably, in step (2), the oxygen content in the mixed gas is not more than 10% by volume, preferably 4-10% by volume.
6. The process of any of claims 1-5, wherein the chloropropene content of the second cooling gas is not more than 0.1 vol%;
preferably, the oxygen content of the second cooling gas is not more than 10% by volume, preferably 5-10% by volume;
preferably, the second cooling is a two-stage cooling or a multi-stage cooling in series.
7. The method according to any one of claims 1 to 6, wherein the cold source in the first cooling and the second cooling is each independently selected from a liquid inert gas and/or a chilled brine, preferably a chilled brine.
8. The method of any of claims 1-7, wherein the method further comprises: and sequentially carrying out membrane separation and gas separation on the second cooling gas to obtain liquid inert gas.
9. The method of claim 8, wherein the method further comprises: exchanging heat between the liquid inert gas and the cold source used for the second cooling to obtain the inert gas after heat exchange and the cold source after heat exchange;
preferably, in step (2), at least part of the inert gas is provided by the inert gas after heat exchange.
10. Process according to any one of claims 1 to 9, wherein the first cooling liquid and the second cooling liquid are mixed to obtain a condensate having a content of chloropropene of from 70 to 80% by weight and a content of epichlorohydrin of from 5 to 20% by weight.
11. The method of claim 10, wherein the method further comprises: the condensate is used as a reaction raw material for the reaction of preparing the epichlorohydrin.
12. A tail gas treatment system containing chloropropene and oxygen, which comprises:
the reactor, the first cooling device and the second cooling device are sequentially communicated, and a gas-phase outlet of the reactor is communicated with an inlet of the first cooling device;
the system also comprises an inert gas introducing pipeline arranged on a communication pipeline between the gas phase outlet of the first cooling device and the second cooling device, so that the first cooling gas obtained by the first cooling device is mixed with the inert gas.
13. The system of claim 12, wherein the first and second cooling devices each independently comprise at least two coolers in series.
14. The system of claim 12 or 13, wherein the system further comprises a membrane separation device and a gas separation device; and the gas phase inlet of the membrane separation device is communicated with the gas phase outlet of the second cooling device, and the gas phase outlet of the membrane separation device is communicated with the inlet of the gas separation device.
15. The system of any one of claims 12-14, further comprising a heat exchanger, wherein the outlet of the gas separation device is in communication with the heat exchanger to provide a liquid inert gas for a heat sink of the heat exchanger; and the outlet of the heat exchanger is communicated with an inert gas introducing pipeline so as to introduce the inert gas obtained after the liquid inert gas is heated.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113856407A (en) * | 2021-10-28 | 2021-12-31 | 山东新龙集团有限公司 | Method for treating tail gas in process of preparing epoxy chloropropane by oxidation method |
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