Method for preparing ethylene from chlorine-containing organic waste

Abstract

The invention belongs to the technical field of chemical engineering and environmental protection, and particularly relates to a method for preparing ethylene from chlorine-containing organic waste. According to the method, the efficient and environment-friendly thermal plasma technology is adopted, the chlorine-containing organic waste is treated by using the gas containing the hydrogen element and the carbon element as the working gas and converted into high-value chemicals such as ethylene and acetylene, and resourceful treatment of the chlorine-containing organic waste is achieved. The working gas can provide a hydrogen-rich reaction atmosphere on one hand, and provides a carbon source on the other hand, so that the yield of ethylene and acetylene is increased. Meanwhile, by adopting a graded quenching technology and regulating and controlling the quenching rates in different temperature ranges in the quenching process, the selectivity and yield of ethylene are greatly improved, the problem that the yield of ethylene in the pyrolysis gas-phase product in the prior art is not high is solved, and effective regulation and control of the composition of the chlorine-containing organic waste pyrolysis gas-phase product are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry and environmental protection, and specifically relates to a method for preparing ethylene by utilizing chlorine-containing organic waste. Background Art

[0002] The existing chemical, pharmaceutical, pesticide and other industries produce a large amount of chlorine-containing wastes, the main organic components of which include chlorine-containing alkanes, chlorine-containing alkenes, chlorine-containing benzene series, etc. Chlorine-containing organic wastes are a type of hazardous wastes, which are generally highly toxic, infectious, and highly accumulated and residual, and have great harm to the ecological environment and human health. Therefore, the treatment technology must have a treatment efficiency close to 100%. With the rapid development of my country's chlorination industry, the amount of corresponding chlorine-containing organic wastes has also increased dramatically. Whether the chlorine-containing organic wastes can be disposed of in a timely and effective manner has become an important factor restricting the development of the industry. At the same time, if the chlorine-containing organic wastes can be recycled and processed into high-value-added chemicals, a large amount of resources can be saved, and resource utilization can be further realized on the basis of achieving waste reduction and harmlessness.

[0003] At present, the traditional methods for treating chlorine-containing organic wastes include incineration and landfill. Incineration can significantly reduce volume, quantity and harmlessness, but on the one hand, the organic chlorine in chlorine-containing organic wastes has an inhibitory effect on combustion, reducing combustion efficiency, and this type of waste has a low calorific value, so it is necessary to add fuel for mixed combustion, which increases the cost of the incineration method. On the other hand, if the operation is improper, highly toxic dioxins are easily produced during the incineration process, causing secondary pollution. Although the landfill method is simple and easy, the presence of chlorine increases the difficulty of waste treatment. When directly landfilled, plasticizers and stabilizers will leach and pollute the soil and groundwater. In addition, landfill takes up a lot of space. When land resources gradually become tight, the cost of safe landfill is also greatly increased.

[0004] Therefore, there is an urgent need for a technology that can achieve the harmlessness and resource utilization of chlorine-containing organic waste. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing ethylene by utilizing chlorine-containing organic wastes. The method provided by the present invention can achieve harmlessness and resource utilization of chlorine-containing organic wastes.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

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

[0008] The working gas forms a plasma atmosphere, and the chlorine-containing organic waste is subjected to cracking reaction and graded quenching in the plasma atmosphere in sequence to obtain cracking products; the graded quenching includes sequentially performing a first quenching and a second quenching, 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; the molar ratio of hydrogen to carbon in the plasma atmosphere is greater than 2:1;

[0009] The cracking product is subjected to gas-solid separation to obtain a gas phase product and a solid phase product, wherein the gas phase product includes 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 includes one or more of dry gas, coke oven gas and natural gas.

[0013] Preferably, the chlorine-containing organic waste includes carbon and chlorine.

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

[0015] Preferably, the stepwise quenching method includes partition quenching and / or direct quenching;

[0016] The direct quenching includes physical quenching and / or chemical quenching;

[0017] The cooling medium used in the partition quenching includes water, liquid nitrogen, cooling oil or freezing liquid;

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

[0019] Preferably, the cracking reaction is carried out in a plasma reactor;

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

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

[0022] The processing capacity of the chlorine-containing organic waste is 0.5 to 1000 kg / 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 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, subjecting the chlorine-containing organic waste to cracking reaction and graded quenching in the plasma atmosphere in sequence to obtain cracking products; 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 and carbon elements in the plasma atmosphere is greater than 2:1; and the cracking products are subjected to gas-solid separation to obtain gas phase products and solid phase products, wherein the gas phase products comprise ethylene.

[0025] The present invention adopts efficient and environmentally friendly thermal plasma technology, and uses a gas containing hydrogen and carbon elements as a working gas to treat chlorine-containing organic wastes, converting them into high-value chemicals such as ethylene and acetylene, thereby realizing resource processing of chlorine-containing organic wastes. The working gas can provide a hydrogen-rich reaction atmosphere on the one hand, and a carbon source on the other hand, thereby increasing the yield of ethylene and acetylene. At the same time, by adopting a graded quenching technology, the selectivity and yield of ethylene are greatly improved by regulating the quenching rate within different temperature ranges during the quenching process, thereby solving the problem of low ethylene yield in the cracking gas phase product under the prior art, and realizing effective regulation of the composition of the cracking gas phase product of chlorine-containing organic wastes.

[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 more than 98%, and significantly improves 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 adjustable products, etc., realizes the comprehensive resource utilization of chlorine-containing organic wastes, 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 by utilizing chlorine-containing organic waste, comprising the following steps:

[0030] The working gas forms a plasma atmosphere, and the chlorine-containing organic waste is subjected to cracking reaction and graded quenching in the plasma atmosphere in sequence to obtain cracking products; the graded quenching includes sequentially performing a first quenching and a second quenching, 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; the molar ratio of hydrogen to carbon in the plasma atmosphere is greater than 2:1;

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

[0032] The invention forms a plasma atmosphere with working gas, and performs cracking reaction and graded quenching in the plasma atmosphere in sequence on chlorine-containing organic waste to obtain cracking products.

[0033] In the present invention, the working gas contains hydrogen and carbon. In the present invention, the molar ratio of hydrogen to carbon in the plasma atmosphere is greater than 2:1, more preferably 4 to 20:1, specifically 4.9:1, 5.2:1, 5.6:1, 6.5:1. In the present invention, the working gas preferably includes one or more of dry gas, coke oven gas and natural gas; 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 present invention has no particular limitation on the process of forming the plasma atmosphere, and any method known to those skilled in the art may be adopted.

[0035] In the present invention, the chlorine-containing organic waste preferably includes carbon and chlorine, and may also include hydrogen. The present invention has no special requirements on the source and state of the chlorine-containing organic waste and the ratio between the elements, and those familiar to those skilled in the art can be used. In a specific embodiment of the present invention, the chlorine-containing organic waste is preferably solid hexachlorobenzene waste or liquid tetrachloroethylene waste provided by a chemical plant.

[0036] In the present invention, the cracking 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 arc plasma reactor; the arc plasma reactor is preferably a DC arc plasma reactor; the DC arc plasma reactor is further preferably a magnetic rotating arc thermal plasma reactor. In the present invention, a magnetic rotating arc thermal plasma reactor is used, in which the arc rotates at a high speed, which is beneficial to prolonging the service life of the anode, while making the raw material and the plasma mix more fully, thereby improving the efficiency of the cracking reaction.

[0037] In the present invention, when the chlorine-containing organic waste is solid hexachlorobenzene waste, it is preferably introduced into the plasma reactor through a solid feeding system; when the chlorine-containing organic waste is liquid tetrachloroethylene waste, it is preferably introduced into the plasma reactor by pumping, and the pumping method is preferably a peristaltic pump.

[0038] In the present invention, the flow rate of the working gas is preferably 0.5 to 1500 Nm 3 / h. In the present invention, the processing capacity of the chlorine-containing organic waste is preferably 0.5 to 1000 kg / h. In the present invention, the chlorine-containing organic waste is preferably introduced into the plasma reactor using a carrier gas, and the carrier gas preferably includes one or more of dry gas, coke oven gas, hydrogen and argon. In the present invention, an appropriate working gas and carrier gas flow rate are selected according to the feed amount of the chlorine-containing organic waste and the required hydrogen / carbon element ratio; there is no special requirement for the carrier gas flow rate, as long as it can satisfy the requirement of fluidizing the chlorine-containing organic waste into the plasma reactor.

[0039] In the present invention, when an arc plasma reactor is used to treat chlorine-containing organic waste, the chlorine-containing organic waste is preferably introduced into the arc plasma reactor from above or below the arc; more preferably, it enters the arc plasma reactor from above the arc, thereby fully utilizing the heat in the arc region, fully mixing the raw material with the hot plasma, and ensuring that the cracking reaction proceeds quickly and fully.

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

[0041] In the present invention, the quenching rate of the first quenching is preferably greater than or equal to 1×10 4 K / s, and the temperature of the product after the first quenching is preferably 1100-1300K. In the present invention, the quenching rate of the second quenching is preferably 300-1000K / s, and the temperature of the cracking product is preferably lower than 600K. The present invention adjusts the quenching rate by changing the internal structure of the partition wall of the quenching section, the type and / or flow rate of the cooling medium. 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 quickly 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 produce ethylene cannot be fully carried out, reducing the yield of ethylene in the gas phase product.

[0042] In the present invention, the step-wise quenching method preferably includes partition quenching and / or direct quenching; the direct quenching preferably includes physical quenching and / or chemical quenching; the cooling medium used in the partition quenching preferably includes water, liquid nitrogen, cooling oil or freezing liquid; the cooling medium used in the direct quenching preferably includes one or more of argon, nitrogen, propane and the working gas. In the present invention, the direction in which the cooling medium is sprayed into the quenching zone of the plasma reactor is preferably radial or tangential.

[0043] After obtaining the cracking product, the present invention performs 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.

[0044] The present invention has no special requirements for the gas-solid separation method, and conventional gas-solid separation technology in the art can be used, preferably a cyclone separator, a bag filter or a ceramic separator, specifically a ceramic separator.

[0045] In the present invention, the gas phase product includes ethylene, and preferably also includes acetylene and hydrogen chloride. In the present invention, after obtaining the gas phase product, it is also preferred to transport the gas phase product to the vinyl chloride production section of the ethylene-acetylene process, or obtain product ethylene and acetylene after conventional separation and purification operations such as absorption and distillation, and the separated hydrogen, argon, etc. can be returned to the plasma device and used as a carrier gas and / or quenching medium again to participate in the transportation and cracking of chlorine-containing organic wastes, thereby improving the utilization rate of the gas.

[0046] In the present invention, the solid phase product is preferably a carbon single substance, and the carbon single substance is preferably present in the form of nano carbon black particles and / or graphene.

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

[0048] The schematic flow diagram of the method provided by the present invention is as follows Figure 1 As shown, 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 invention are all commercially available products in the art.

[0050] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] Example 1

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

[0053] The pyrolysis products obtained after quenching are separated into gas and solid by using a ceramic separator to obtain gas phase products and solid phase products respectively;

[0054] According to gas chromatography, the main components of the gas phase product (except the working gas and the carrier gas) are ethylene, acetylene and hydrogen chloride, with volume fractions of 19.66%, 19.26% and 48.13% respectively, the ethylene yield is 40.64%, and the acetylene yield is 39.82%. TEM-EDS elemental analysis shows that the solid product is mainly composed of C, O and Cl elements, of which C element accounts for 96.7% and Cl element accounts for 0.33%. The solid product is mainly nano carbon black particles.

[0055] Example 2

[0056] The chlorine-containing organic waste (solid hexachlorobenzene waste provided by a chemical plant) is transported into the RF plasma reactor by carrier gas through the solid feeding system. The hexachlorobenzene feed rate is 10 kg / h, and the working gas is dry gas with a flow rate of 20 Nm 3 / h, the carrier gas argon flow rate is 8Nm 3 / h, the temperature in the plasma reactor is 2400K, and the molar ratio of hydrogen to carbon in the plasma atmosphere is 5.2; after millisecond cracking reaction, the cracking products produced are subjected to first quenching and second quenching in sequence until the temperature of the cracking products is below 600K, wherein the quenching rate of the first quenching is 1.2×10 4 K / s, the temperature of the product after the first quenching is 1100K, the quenching rate of the second quenching is 500K / s, and the quenching method is to use argon as the cooling medium to radially spray into the plasma reactor for direct heat exchange;

[0057] The pyrolysis products obtained after quenching are separated into gas and solid by using a ceramic separator to obtain gas phase products and solid phase products respectively;

[0058] According to gas chromatography, the main components of the gas phase product (excluding working gas and carrier gas) are ethylene, acetylene and hydrogen chloride, with volume fractions of 20.59%, 18.16% and 46.92% respectively, ethylene yield is 42.11%, acetylene yield is 37.15%. The solid phase product is mainly a mixture of nano carbon black particles and graphene.

[0059] Example 3

[0060] The chlorine-containing organic waste (solid hexachlorobenzene waste provided by a chemical plant) is transported into the magnetic rotating arc thermal plasma reactor by carrier gas through the solid feeding system. The hexachlorobenzene feed rate is 100 kg / h, and the working gas is dry gas with a flow rate of 175 Nm 3 / h, the carrier gas flow rate is 75Nm 3 / h, the temperature in the plasma reactor is 3000K, and the molar ratio of hydrogen to carbon in the plasma atmosphere is 5.6; after millisecond cracking reaction, the cracking products produced are subjected to first quenching and second quenching in sequence until the temperature of the cracking products is below 600K, wherein the quenching rate of the first quenching is 1.5×10 4 K / s, the temperature of the product after the first quenching is 1200K, the quenching rate of the second quenching is 400K / s, and the quenching method is to use argon as the cooling medium to radially spray into the plasma reactor for direct heat exchange;

[0061] The obtained cracking products are separated into gas and solid by using a ceramic separator to obtain gas phase products and solid phase products respectively;

[0062] According to gas chromatography, the main components of the gas phase product (except working gas and carrier gas) are ethylene, acetylene and hydrogen chloride, with volume fractions of 21.81%, 14.43% and 41.51% respectively, ethylene yield is 43.05%, acetylene yield is 28.49%. The solid phase product is mainly a mixture of nano carbon black particles and graphene.

[0063] Example 4

[0064] The chlorine-containing organic waste (liquid tetrachloroethylene waste provided by a chemical plant) is transported into the magnetic rotating arc thermal plasma reactor by a carrier gas through a peristaltic pump. The tetrachloroethylene feed rate is 1000kg / h, the working gas is dry gas, and the flow rate is 2000Nm 3 / h, the carrier gas argon flow rate is 550Nm 3 / h, the temperature in the plasma reactor is 2500K, and the molar ratio of hydrogen to carbon in the plasma atmosphere is 6.5; after millisecond cracking reaction, the cracking products produced are subjected to first quenching and second quenching in sequence until the temperature of the cracking products is below 600K, wherein the quenching rate of the first quenching is 1.5×104 K / s, the temperature of the product after the first quenching is 1200K, the quenching rate of the second quenching is 400K / s, and the quenching method is to use argon as the cooling medium to radially spray into the plasma reactor for direct heat exchange;

[0065] The obtained cracking products are separated into gas and solid by using a ceramic separator to obtain gas phase products and solid phase products respectively;

[0066] According to gas chromatography, the main components of the gas phase product (except working gas and carrier gas) are ethylene, acetylene and hydrogen chloride, with volume fractions of 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 157.88 Nm 3 / h. The solid phase product is mainly a mixture of nano carbon black particles and graphene.

[0067] Comparative Example 1

[0068] Ethylene was prepared in the same manner as in Example 3, except that the quenching process was different. Specifically, the generated cracking product was quenched at 1.5×10 4 K / s quenching rate until the temperature of the cracking product is below 600K, wherein the quenching method is to use argon as a cooling medium and radially inject it into the plasma reactor for direct heat exchange;

[0069] Gas chromatography showed that the main components of the gas phase product (except working gas and carrier gas) were ethylene, acetylene and hydrogen chloride, with volume fractions of 7.41%, 41.71% and 47.08% respectively. The ethylene yield dropped to 12.91% and the acetylene yield was 72.58%.

[0070] Comparative Example 2

[0071] Ethylene was prepared in the same manner as in Example 4, except that hydrogen was used as the working gas instead of the dry gas.

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

[0073] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing ethylene using chlorine-containing organic waste, characterized in that: The following steps are involved: The working gas forms a plasma atmosphere, and the chlorine-containing organic waste is subjected to cracking reaction and graded quenching in the plasma atmosphere in sequence to obtain cracking products; the graded quenching includes sequentially performing a first quenching and a second quenching, 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; the molar ratio of hydrogen to carbon in the plasma atmosphere is greater than 2:1; The cracking product is subjected to gas-solid separation to obtain a gas phase product and a solid phase product, wherein the gas phase product includes ethylene.

2. The method according to claim 1, characterized in that 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.

3. The method according to claim 2, characterized in that The quenching rate of the second quenching is 300-1000K / s, and the temperature of the cracking product is lower than 600K.

4. The method according to claim 1, characterized in that: The working gas includes one or more of dry gas, coke oven gas and natural gas.

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

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

7. The method according to claim 1, characterized in that 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.

8. 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.

9. The method according to claim 1 or 8, 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 to 1000 kg / h.

10. The method according to claim 1 or 8, characterized in that: The chlorine-containing organic waste is introduced into the plasma reactor by using a carrier gas, and the carrier gas includes one or more of dry gas, coke oven gas, hydrogen and argon.

Images