A method for producing ethylene using a chlorinated organic waste

Abstract

The present application belongs to the field of chemical industry and environmental protection technology, and particularly relates to a method for preparing ethylene by using chlorine-containing organic waste. The present application adopts high-efficiency and environmentally-friendly thermal plasma technology, uses a gas containing hydrogen and carbon elements as a working gas to treat chlorine-containing organic waste, and converts the chlorine-containing organic waste into high-value chemicals such as ethylene and acetylene, thereby realizing the resourceful treatment of the chlorine-containing organic waste. On one hand, the working gas can provide a hydrogen-rich reaction atmosphere, and on the other hand, the working gas can provide a carbon source, thereby improving the yield of ethylene and acetylene. Meanwhile, by using a staged quenching technology and by regulating the quenching rate in different temperature ranges during the quenching process, the selectivity and yield of ethylene can be greatly improved, the problem of low ethylene yield in the cracking gas phase product in the prior art can be solved, and the effective regulation of the composition of the cracking gas phase product of the chlorine-containing organic waste can be realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of chemical industry and environmental protection, and particularly relates to a method for preparing ethylene by using chlorine-containing organic waste. BACKGROUND

[0002] A large amount of chlorine-containing waste is generated in the existing chemical industry, pharmaceutical industry, pesticide industry and the like, and main organic components include chlorine-containing alkanes, chlorine-containing alkenes, chlorine-containing benzene series and the like. The chlorine-containing organic waste is a kind of dangerous waste, and generally has high toxicity, infectivity and high accumulation residual property, which has great harm to the ecological environment and human health, and thus the treatment technology must have a treatment efficiency close to 100%. With the rapid development of the chlor-alkali industry in China, the amount of chlorine-containing organic waste also increases sharply, and whether the chlorine-containing organic waste can be disposed in time and effectively becomes an important factor restricting the development of the industry. Meanwhile, if the chlorine-containing organic waste can be recycled and treated to prepare high-value-added chemicals, a large amount of resources can be saved, and on the basis of realizing waste reduction and harmlessness, further resource utilization is realized.

[0003] At present, the traditional chlorine-containing organic waste treatment methods include incineration and landfill. The incineration can greatly reduce the volume, amount and harmlessness, but on the one hand, the organic chlorine in the chlorine-containing organic waste has an inhibitory effect on combustion, which reduces the combustion efficiency, and the heat value of the waste is low, and fuel needs to be added for mixed combustion, which increases the cost of the incineration. On the other hand, if the operation is not proper, toxic substances dioxin are easily generated in the incineration process, causing secondary pollution. The landfill method is simple and easy to implement, but the presence of chlorine increases the difficulty of waste treatment, and when directly landfilled, plasticizers and stabilizers will leach out to pollute the soil and groundwater. Moreover, the landfill occupies a large amount of space, and when the land resources gradually become scarce, the cost of safe landfill is also greatly increased.

[0004] Therefore, a technology capable of realizing harmlessness and resource utilization of the chlorine-containing organic waste is urgently needed. SUMMARY

[0005] The present application aims to provide a method for preparing ethylene by using chlorine-containing organic waste, and the present application can realize harmlessness and resource utilization of the chlorine-containing organic waste.

[0006] In order to achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0007] The present application provides a method for preparing ethylene by using chlorine-containing organic waste, comprising the following steps:

[0008] forming a plasma atmosphere with a working gas, and sequentially performing a cracking reaction and a fractional quenching on the chlorinated organic waste in the plasma atmosphere to obtain a cracking product; the fractional quenching comprises sequentially performing a first quenching and a second quenching, the quenching rate of the first quenching being greater than the quenching rate of the second quenching; the working gas contains hydrogen and carbon elements; the molar ratio of hydrogen to carbon in the plasma atmosphere is greater than 2:1.

[0009] performing gas-solid separation on the cracking product to obtain a gas phase product and a solid phase product, the gas phase product comprising ethylene.

[0010] Preferably, the quenching rate of the first quenching is greater than or equal to 1×10 4 K / s, and the temperature of the product after the first quenching is 1100-1300K.

[0011] Preferably, the quenching rate of the second quenching is 300-1000K / s, and the temperature of the cracking product is lower than 600K.

[0012] Preferably, the working gas comprises one or more of dry gas, coke oven gas and natural gas.

[0013] Preferably, the chlorinated organic waste comprises carbon and chlorine elements.

[0014] Preferably, the temperature of the cracking reaction is 1800-3500K.

[0015] Preferably, the fractional quenching comprises wall-type quenching and / or direct quenching.

[0016] The direct quenching comprises physical quenching and / or chemical quenching.

[0017] The cooling medium for the wall-type quenching comprises water, liquid nitrogen, cooling oil or refrigerant.

[0018] The cooling medium for the direct quenching comprises one or more of argon, nitrogen, propane and the working gas.

[0019] Preferably, the cracking reaction is performed in a plasma reactor.

[0020] The plasma reactor comprises a radio frequency plasma reactor, a microwave plasma reactor or an arc plasma reactor.

[0021] Preferably, the flow rate of the working gas is 0.5-1500Nm 3 / h.

[0022] The processing amount of the chlorinated organic waste is 0.5-1000kg / h.

[0023] Preferably, the chlorine-containing organic waste is introduced into the plasma reactor using a carrier gas, and the carrier gas includes one or more of dry gas, coke oven gas, hydrogen and argon.

[0024] The present invention provides a method for preparing ethylene by utilizing chlorine-containing organic waste, comprising the following steps: forming a plasma atmosphere with a working gas, sequentially subjecting the chlorine-containing organic waste to a cracking reaction and graded quenching in the plasma atmosphere to obtain a cracking product; the graded quenching comprises sequentially performing a first quenching and a second quenching, wherein the quenching rate of the first quenching is greater than the quenching rate of the second quenching; the working gas contains hydrogen and carbon elements; the molar ratio of hydrogen to carbon elements in the plasma atmosphere is greater than 2:1; and performing gas-solid separation on the cracking product to obtain a gas phase product and a solid phase product, wherein the gas phase product comprises ethylene.

[0025] The present invention adopts efficient and environmentally friendly thermal plasma technology, utilizing a gas containing hydrogen and carbon as a working gas to treat chlorine-containing organic waste, converting it into high-value chemicals such as ethylene and acetylene, thereby realizing resource-based treatment of chlorine-containing organic waste. The working gas can provide a hydrogen-rich reaction atmosphere on the one hand, and a carbon source on the other, thereby increasing the production of ethylene and acetylene. Simultaneously, the use of a graded quenching technology greatly improves the selectivity and yield of ethylene by regulating the quenching rate within different temperature ranges during the quenching process, thereby resolving the problem of low ethylene production in the cracking gas phase products under existing technologies and achieving effective regulation of the composition of the cracking gas phase products of chlorine-containing organic waste.

[0026] Furthermore, the present invention has good adaptability to raw materials, has no special requirements for the state and composition of chlorine-containing organic waste, has good applicability, and does not require pretreatment; has no special requirements for the type and specific composition of the working gas; has a high raw material utilization rate, a chlorine-containing organic waste conversion rate of greater than 98%, and significantly increases the ethylene content in the cracking gas; the equipment is simple, easy to operate, does not require a catalyst, is green and environmentally friendly, does not produce harmful substances such as dioxins, and achieves zero pollutant emissions.

[0027] The method provided by the present invention has the advantages of short reaction time, high conversion rate, no secondary pollution and controllable products, etc., realizes the comprehensive resource utilization of chlorine-containing organic waste and greatly increases the output of ethylene in the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The present invention provides a schematic flow chart of the method. DETAILED DESCRIPTION

[0029] The present invention provides a method for preparing ethylene from chlorine-containing organic waste, comprising the following steps:

[0030] The working gas is formed into a plasma atmosphere, and the chlorinated organic waste is subjected to a pyrolysis reaction and a graded quenching in the plasma atmosphere in sequence to obtain a pyrolysis product; the graded quenching includes first quenching and second quenching in sequence, and the quenching rate of the first quenching is greater than that of the second quenching; the working gas contains hydrogen and carbon; and the molar ratio of hydrogen to carbon in the plasma atmosphere is greater than 2:1.

[0031] The pyrolysis product is subjected to gas-solid separation to obtain a gas phase product and a solid phase product, and the gas phase product includes ethylene.

[0032] The working gas is formed into a plasma atmosphere, and the chlorinated organic waste is subjected to a pyrolysis reaction and a graded quenching in the plasma atmosphere in sequence to obtain a pyrolysis product.

[0033] In the present application, the working gas contains hydrogen and carbon. In the present application, the molar ratio of hydrogen to carbon in the plasma atmosphere is greater than 2:1, and is preferably 4-20:1, and can be 4.9:1, 5.2:1, 5.6:1 or 6.5:1. In the present application, the working gas preferably includes one or more of dry gas, coke oven gas and natural gas; and the dry gas preferably includes one or more of reforming dry gas, hydrocracking dry gas, catalytic cracking dry gas and coking dry gas.

[0034] The process of forming the plasma atmosphere is not particularly limited in the present application, and any process known to those skilled in the art can be used.

[0035] In the present application, the chlorinated organic waste preferably contains carbon and chlorine, and can also contain hydrogen. The source and state of the chlorinated organic waste and the ratio of the elements are not particularly limited in the present application, and any process known to those skilled in the art can be used. In the specific embodiments of the present application, the chlorinated organic waste is preferably solid hexachlorobenzene waste or liquid tetrachloroethylene waste provided by a chemical plant.

[0036] In the present application, the pyrolysis reaction is preferably carried out in a plasma reactor; the plasma reactor preferably includes a radio frequency plasma reactor, a microwave plasma reactor or an electric arc plasma reactor; the electric arc plasma reactor is preferably a direct current electric arc plasma reactor; and the direct current electric arc plasma reactor is further preferably a magnetic rotating electric arc thermal plasma reactor. In the present application, a magnetic rotating electric arc thermal plasma reactor is used, in which the electric arc rotates at a high speed, which is beneficial to prolonging the service life of the anode, and at the same time, the mixing of the raw material with the plasma is more sufficient, and the pyrolysis reaction efficiency is improved.

[0037] In the present application, when the chlorine-containing organic waste is solid hexachlorobenzene waste, it is preferably fed into the plasma reactor through a solid feeding system; when the chlorine-containing organic waste is liquid tetrachloroethylene waste, it is preferably fed into the plasma reactor through a pumping method, which preferably uses a peristaltic pump for pumping.

[0038] In the present application, the flow rate of the working gas is preferably 0.5-1500 Nm 3 / h. In the present application, the processing capacity of the chlorine-containing organic waste is preferably 0.5-1000 kg / h. In the present application, the chlorine-containing organic waste is preferably fed into the plasma reactor using a carrier gas, which preferably includes one or more of dry gas, coke oven gas, hydrogen, and argon. In the present application, the working gas and the carrier gas flow rate are selected according to the feed amount of the chlorine-containing organic waste and the required hydrogen / carbon element ratio; the carrier gas flow rate is not particularly limited, as long as it can ensure that the chlorine-containing organic waste is fluidized and fed into the plasma reactor.

[0039] In the present application, when the arc plasma reactor is used to treat the chlorine-containing organic waste, the chlorine-containing organic waste is preferably fed into the arc plasma reactor from above or below the arc; more preferably, it is fed into the arc plasma reactor from above the arc, so as to fully utilize the heat of the arc region, fully mix the raw material with the hot plasma, and ensure that the cracking reaction proceeds rapidly and sufficiently.

[0040] In the present application, the temperature of the cracking reaction is preferably 1800-3500 K, and can be specifically 1800 K, 2000 K, 2200 K, 2400 K, 2500 K, 2800 K, 3000 K, 3200 K, or 3500 K.

[0041] In the present application, the quenching rate of the first quenching is preferably greater than or equal to 1x10 4 K / s, and the temperature of the product after the first quenching is preferably 1100-1300 K. In the present application, the quenching rate of the second quenching is preferably 300-1000 K / s, and the temperature of the cracking product is preferably lower than 600 K. In the present application, the quenching rate is adjusted by changing the inner structure of the quenching section, the type of the cooling medium, and / or the flow rate. The quenching rate has a great influence on the composition of the cracking gas; if the quenching rate of the high-temperature quenching section (i.e., the first quenching) is too low, acetylene will rapidly decompose into solid carbon and hydrogen at high temperature, greatly reducing the total yield of hydrocarbons in the gas phase product; if the quenching rate of the low-temperature quenching section (i.e., the second quenching) is too high, the reaction of acetylene hydrogenation to form ethylene cannot proceed sufficiently, reducing the yield of ethylene in the gas phase product.

[0042] In the present application, the way of the graded quenching preferably comprises barrier quenching and / or direct quenching; the direct quenching preferably comprises physical quenching and / or chemical quenching; the cooling medium used in the barrier quenching preferably comprises water, liquid nitrogen, cooling oil or refrigerant; the cooling medium used in the direct quenching preferably comprises one or more of argon, nitrogen, propane and the working gas. In the present application, the direction of the cooling medium sprayed into the quenching zone of the plasma reactor is preferably radial or tangential.

[0043] After obtaining the cracking product, the present application carries out gas-solid separation on the cracking product to obtain a gas phase product and a solid phase product, and the gas phase product comprises ethylene.

[0044] The present application does not have special requirements for the way of the gas-solid separation, and the conventional gas-solid separation technology in the art can be used, which is preferably a cyclone separator, a bag filter or a ceramic separator, and specifically can be a ceramic separator.

[0045] In the present application, the gas phase product comprises ethylene, and also preferably comprises acetylene and hydrogen chloride. In the present application, after obtaining the gas phase product, it is also preferable to transport the gas phase product to an ethylene production section by the acetylene method, or after absorption, rectification and other conventional separation and purification operations, to obtain product ethylene and acetylene, and the separated hydrogen, argon and the like can be returned to the plasma device to participate in the transportation and cracking of the chlorinated organic waste again as the carrier gas and / or quenching medium, thereby improving the utilization rate of the gas.

[0046] In the present application, the solid phase product is preferably elemental carbon, which preferably exists in the form of nano-carbon black particles and / or graphene.

[0047] In the present application, the conversion rate of the chlorinated organic waste is preferably greater than 98%, and the ethylene yield in the cracking gas is preferably greater than 40%.

[0048] The flowchart of the method provided by the present application is shown in Figure 1 The working gas is dry gas, the high-temperature quenching zone is the first quenching, and the low-temperature quenching zone is the second quenching.

[0049] Unless otherwise specified, the materials and equipment used in the present application are commercially available in the art.

[0050] The technical solutions in the present application will be clearly and completely described below by combining with the embodiments in the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0051] Example 1

[0052] The solid feed system is used to transport the solid waste (solid hexachlorobenzene waste provided by a chemical plant) into the microwave plasma reactor by using carrier gas. The feeding amount of hexachlorobenzene is 2.8 kg / h, the working gas is dry gas, the flow rate is 5 Nm 3 / h, the flow rate of carrier gas argon is 3.3 Nm 3 / h, the temperature in the plasma reactor is 2000 K, the molar ratio of hydrogen element to carbon element in the plasma atmosphere is 4.9; the produced cracking products are subjected to first quenching and second quenching in sequence until the temperature of the cracking products is below 600 K, wherein the quenching rate of the first quenching is 1×10 4 K / s, the temperature of the products after the first quenching is 1200 K, the quenching rate of the second quenching is 500 K / s, and the quenching mode is wall heat exchange by using deionized water as the cooling medium;

[0053] The produced cracking products after the quenching are subjected to gas-solid separation by using a ceramic separator to obtain gas phase products and solid phase products respectively.

[0054] It is determined by gas chromatography that the main components (except the working gas and the carrier gas) in the gas phase products are ethylene, acetylene and hydrogen chloride, and the volume fractions thereof are 19.66%, 19.26% and 48.13% respectively. The ethylene yield is 40.64%, and the acetylene yield is 39.82%. It is obtained by TEM-EDS element analysis that the solid products are mainly composed of C, O and Cl elements, wherein the C element accounts for 96.7%, and the Cl element accounts for 0.33%. The solid products are mainly nano carbon black particles.

[0055] Example 2

[0056] The solid feed system is used to transport the solid waste (solid hexachlorobenzene waste provided by a chemical plant) into the microwave plasma reactor by using carrier gas. The feeding amount of hexachlorobenzene is 2.8 kg / h, the working gas is dry gas, the flow rate is 5 Nm 3 / h, the flow rate of carrier gas argon is 3.3 Nm 3 / h, the temperature in the plasma reactor is 2000 K, the molar ratio of hydrogen element to carbon element in the plasma atmosphere is 4.9; the produced cracking products are subjected to first quenching and second quenching in sequence until the temperature of the cracking products is below 600 K, wherein the quenching rate of the first quenching is 1×10 4 K / s, the temperature of the products after the first quenching is 1200 K, the quenching rate of the second quenching is 500 K / s, and the quenching mode is wall heat exchange by using deionized water as the cooling medium;

[0057] The produced cracking products after the quenching are subjected to gas-solid separation by using a ceramic separator to obtain gas phase products and solid phase products respectively.

[0058] The main components (except working gas and carrier gas) in the gas phase product were ethylene, acetylene and hydrogen chloride, and their volume fractions were 20.59%, 18.16% and 46.92% respectively, the ethylene yield was 42.11%, and the acetylene yield was 37.15% as determined by gas chromatography. The solid phase product was mainly a mixture of nano carbon black particles and graphene.

[0059] Example 3

[0060] The chlorinated organic waste (solid hexachlorobenzene waste provided by a chemical plant) was transported into the magnetic rotating arc thermal plasma reactor by the carrier gas through the solid feeding system, the hexachlorobenzene feeding amount was 100 kg / h, the working gas was dry gas, the flow rate was 175 Nm 3 / h, the carrier gas dry gas flow rate was 75 Nm 3 / h, the temperature in the plasma reactor was 3000 K, and the molar ratio of hydrogen element to carbon element in the plasma atmosphere was 5.6; after the millisecond cracking reaction, the cracking products were sequentially subjected to first quenching and second quenching until the temperature of the cracking products was below 600 K, wherein the quenching rate of the first quenching was 1.5 x 10 4 K / s, the temperature of the products after the first quenching was 1200 K, the quenching rate of the second quenching was 400 K / s, and the quenching method was direct heat exchange by radial injection of argon gas as the cooling medium into the plasma reactor;

[0061] The obtained cracking products were subjected to gas-solid separation by a ceramic separator to obtain gas phase products and solid phase products respectively;

[0062] The main components (except working gas and carrier gas) in the gas phase product were ethylene, acetylene and hydrogen chloride, and their volume fractions were 20.59%, 18.16% and 46.92% respectively, the ethylene yield was 42.11%, and the acetylene yield was 37.15% as determined by gas chromatography. The solid phase product was mainly a mixture of nano carbon black particles and graphene.

[0063] Example 4

[0064] The chlorinated organic waste (liquid tetrachloroethylene waste provided by a chemical plant) was transported into the magnetic rotating arc thermal plasma reactor by the carrier gas through the peristaltic pump, the tetrachloroethylene feeding amount was 1000 kg / h, the working gas was dry gas, the flow rate was 2000 Nm 3 / h, the carrier gas argon flow rate was 550 Nm 3 / h, the temperature in the plasma reactor was 2500 K, and the molar ratio of hydrogen element to carbon element in the plasma atmosphere was 6.5; after the millisecond cracking reaction, the cracking products were sequentially subjected to first quenching and second quenching until the temperature of the cracking products was below 600 K, wherein the quenching rate of the first quenching was 1.5 x 104 K / s, the temperature of the first quenched product is 1200K, the quenching rate of the second quenching is 400K / s, and the quenching mode is direct heat exchange by spraying argon into the plasma reactor as a cooling medium;

[0065] The obtained cracking product is subjected to gas-solid separation by using a ceramic separator to obtain gas phase product and solid phase product respectively.

[0066] According to the gas chromatography, the main components (except working gas and carrier gas) in the gas phase product are ethylene, acetylene and hydrogen chloride, the volume fractions of which are 15.92%, 15.84% and 54.14% respectively, the ethylene yield is 41.24%, and the acetylene yield is 41.01%; the flow rates of ethylene and acetylene in the gas phase product are 158.75 and 157.88Nm 3 / h respectively. The solid phase product is mainly a mixture of nano carbon black particles and graphene.

[0067] Comparative Example 1

[0068] The ethylene is prepared in the manner of Example 3, except that the quenching process is different, specifically: the generated cracking product is quenched at a quenching rate of 1.5x10 4 K / s until the temperature of the cracking product is below 600K, wherein the quenching mode is direct heat exchange by spraying argon into the plasma reactor as a cooling medium;

[0069] According to the gas chromatography, the main components (except working gas and carrier gas) in the gas phase product are ethylene, acetylene and hydrogen chloride, the volume fractions of which are 7.41%, 41.71% and 47.08% respectively, the ethylene yield is reduced to 12.91%, and the acetylene yield is 72.58%.

[0070] Comparative Example 2

[0071] The ethylene is prepared in the manner of Example 4, except that hydrogen is used as the working gas instead of dry gas.

[0072] According to the gas chromatography, the main components (except working gas and carrier gas) in the gas phase product are ethylene, acetylene and hydrogen chloride, the volume fractions of which are 8.09%, 7.50% and 78.16% respectively, the ethylene yield is 41.38%, and the acetylene yield is 38.39%, but the flow rates of ethylene and acetylene in the gas phase product are 55.84 and 51.80Nm 3 / h, which is much lower than the flow rates of ethylene and acetylene in Example 4, thus it can be seen that the method provided by the present application can further improve the yield of ethylene and acetylene.

[0073] Although the above embodiments have been described in detail, it should be understood that these are only some embodiments of the present application, but not all embodiments, and other embodiments can be obtained without creativity on the basis of the above embodiments, and these embodiments all belong to the protection scope of the present application.

Claims

1. A method for preparing ethylene using chlorine-containing organic waste, characterized in that: The following steps are involved: The working gas is formed into a plasma atmosphere, and the chlorine-containing organic waste is subjected to a cracking reaction and graded quenching in the plasma atmosphere in sequence to obtain a cracking product; the graded quenching includes a first quenching and a second quenching in sequence, and the quenching rate of the first quenching is greater than the quenching rate of the second quenching; the working gas contains hydrogen and carbon elements; and the molar ratio of hydrogen to carbon elements in the plasma atmosphere is greater than 2:1; performing gas-solid separation on the cracking product to obtain a gas phase product and a solid phase product, wherein the gas phase product includes ethylene; The quenching rate of the first quenching is greater than or equal to 1×10 4 K / s, the temperature of the product after the first quenching is 1100~1300K; The quenching rate of the second quenching is 300-1000K / s, and the temperature of the pyrolysis product is lower than 600K; The working gas includes one or more of dry gas, coke oven gas and natural gas.

2. The method according to claim 1, characterized in that The chlorine-containing organic waste includes carbon elements and chlorine elements.

3. The method according to claim 1, characterized in that The temperature of the cracking reaction is 1800~3500K.

4. The method according to claim 1, wherein The stepwise quenching method includes partition quenching and / or direct quenching; The direct quenching includes physical quenching and / or chemical quenching; The cooling medium used in the partition quenching includes water, liquid nitrogen, cooling oil or freezing liquid; The cooling medium used in the direct quenching includes one or more of argon, nitrogen, propane and the working gas.

5. The method according to claim 1, characterized in that The cracking reaction is carried out in a plasma reactor; The plasma reactor includes a radio frequency plasma reactor, a microwave plasma reactor or an arc plasma reactor.

6. The method according to claim 1 or 5, characterized in that The flow rate of the working gas is 0.5~1500Nm 3 / h; The processing capacity of the chlorine-containing organic waste is 0.5~1000kg / h.

7. The method according to claim 1 or 5, characterized in that The chlorine-containing organic waste is introduced into the plasma reactor by using a carrier gas, wherein the carrier gas comprises one or more of dry gas, coke oven gas, hydrogen and argon.

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