Method and device for continuously treating waste plastics by driving liquid metal through microwaves

Abstract

The invention relates to the technical field of waste plastic treatment, and provides a method and device for continuously treating waste plastics by driving liquid metal through microwaves, and the method comprises the steps that S1, waste plastic raw materials are pretreated, and dry waste plastic particles are obtained; s2, uniformly mixing the waste plastic particles with liquid metal in an inert gas environment to obtain a mixed material; s3, continuously feeding the mixed material into a microwave reaction cavity, and carrying out irradiation treatment on the mixed material through microwaves so as to decompose the waste plastic particles to obtain a decomposed product; s4, due to the physical property difference between the liquid metal and the decomposition product, the liquid metal is spontaneously separated from the decomposition product and mixed with the waste plastic particles again; and S5, carrying out gas-solid separation, gas-liquid separation and inert gas separation on the decomposition product, and enabling the separated inert gas to enter the step S2 again to enter the next cycle. Continuous production of the waste plastic can be achieved, the production efficiency is improved, and the requirement for large-scale industrial treatment of the waste plastic can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of waste plastic treatment, and particularly to a method and device for continuously treating waste plastics driven by microwave with liquid metal. Background Art

[0002] With the wide application of plastic products, the generation amount of waste plastics is increasing day by day. The large accumulation of waste plastics not only occupies land resources, but also causes serious pollution to the environment. Traditional waste plastic treatment methods such as landfilling and incineration have many drawbacks. Landfilling will lead to soil pollution and groundwater pollution, while incineration will produce harmful gases and damage the atmospheric environment. Therefore, it is of great practical significance to find an efficient and environmentally friendly waste plastic treatment method.

[0003] The core advantage of microwave treatment of plastic waste lies in efficient and controllable energy utilization and green conversion potential. Compared with traditional pyrolysis, microwave can rapidly heat up the interior of substances through the selective heating mechanism of polar molecules, significantly shortening the reaction time and reducing energy consumption. However, due to the poor microwave absorption performance of plastics, the simple action of microwave on waste plastics has problems such as low reaction efficiency and poor product selectivity. In the prior art, liquid metal is usually used as a catalyst. Liquid metal has good fluidity, electrical conductivity and thermal conductivity. In a microwave field, it can produce special physical effects such as eddy current heating and arc discharge to excite plasma. Applying liquid metal as a catalyst to the microwave treatment of waste plastics can not only effectively increase the contact area with plastics, improve the utilization efficiency of microwave energy, and promote the decomposition of waste plastics. This technology is particularly suitable for treating complex plastic mixtures. By precisely controlling the microwave parameters and the proportion of liquid metal catalyst, polyolefins and other difficult-to-degrade plastics can be directionally converted into high-value-added products, while effectively inhibiting the generation of toxic by-products such as dioxins.

[0004] However, in the prior art, the treatment of waste plastics using liquid metal and microwave is mostly intermittent operation, which cannot achieve continuous production, has low production efficiency, and is difficult to meet the requirements of large-scale industrial treatment of waste plastics. Summary of the Invention

[0005] The present invention provides a method and device for continuously treating waste plastics driven by microwave with liquid metal to solve the defects of incapability of continuous production, low reaction efficiency and poor product selectivity in the prior art, realize the efficient, environmentally friendly and continuous treatment of waste plastics, improve the recycling rate of waste plastics, and reduce the treatment cost.

[0006] The present invention provides a method for continuously treating waste plastics driven by microwave with liquid metal, including the following steps: S1. Pretreat the waste plastic raw materials to obtain dry waste plastic particles; S2. Under an inert gas environment, uniformly mix the waste plastic particles with the liquid metal to obtain a mixed material; S3. Continuously feed the mixed material into a microwave reaction cavity, and irradiate the mixed material with microwaves to decompose the waste plastic particles and obtain decomposition products; S4. Due to the physical property differences between the liquid metal and the decomposition products, the liquid metal spontaneously separates from the decomposition products, mixes with the waste plastic particles again, and enters the next cycle; S5. Perform gas-solid separation, gas-liquid separation, and inert gas separation on the decomposition products. The separated inert gas re-enters S2 and enters the next cycle.

[0007] According to a method for continuously treating waste plastics by microwave-driven liquid metal provided by the present invention, in the step S1, it includes: Sort the waste plastic raw materials and remove the impurities therein; Crush the waste plastic raw materials to form small waste plastic pieces; Clean the small waste plastic pieces to remove dirt and dust on the surface, and perform a drying treatment to obtain dry waste plastic particles.

[0008] According to a method for continuously treating waste plastics by microwave-driven liquid metal provided by the present invention, in the step S2, it includes: The liquid metal is a metal or alloy with a melting point lower than 300 °C, and the mass ratio of the liquid metal to the waste plastic particles is 1:1 - 1:30.

[0009] According to a method for continuously treating waste plastics by microwave-driven liquid metal provided by the present invention, in the step S3, the feeding speed is 1 - 500 kg / h.

[0010] According to a method for continuously treating waste plastics by microwave-driven liquid metal provided by the present invention, in the step S4, the liquid metal is purified before being mixed with the waste plastic particles.

[0011] According to a method for continuously treating waste plastics by microwave-driven liquid metal provided by the present invention, in the step S5, it includes: Perform gas-solid separation on the decomposition products, collect the solid products, and obtain the first gaseous products; Perform secondary separation on the first gaseous products, cool and liquefy the first gaseous products to obtain liquid products and second gaseous products; Perform tertiary separation on the second gaseous products to obtain the third gaseous products and inert gas; the inert gas re-enters the reaction system to provide an inert environment for the reaction.

[0012] According to a method for continuously treating waste plastics by microwave-driven liquid metal provided by the present invention, in the step S1, the waste plastics are one or more of polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyurethane, and resin plastics.

[0013] According to a method for continuously treating waste plastics by microwave-driven liquid metal provided by the present invention, in the step S2, the mixing method adopts at least one of spray mixing and stirring mixing.

[0014] According to a method for continuously treating waste plastics by microwave-driven liquid metal provided by the present invention, in the step S2, the reaction temperature is controlled at 300 - 500 °C, and the reaction time is 5 - 30 min.

[0015] The present invention also provides a device for continuously treating waste plastics by microwave-driven liquid metal, including the following modules: A waste plastic pretreatment unit for pretreating waste plastic raw materials to obtain dry waste plastic particles; A liquid metal supplement unit for providing liquid metal; A mixing unit with inert gas inside; the mixing unit is connected to the waste plastic pretreatment unit and the liquid metal supplement unit; A continuous feeding unit with one end connected to the mixing unit; A microwave reaction unit having a microwave reaction chamber, and the microwave reaction chamber is connected to the other end of the continuous feeding unit; under the action of microwave, the liquid metal and the waste plastics react to decompose the waste plastics to obtain decomposition products; A liquid metal circulation unit connected to the microwave reaction unit and the liquid metal supplement unit; the liquid metal circulation unit is used to collect the liquid metal separated from the decomposition products and pump the separated liquid metal to the liquid metal supplement unit; A product separation unit connected to the microwave reaction unit, and the product separation unit is used for gas-solid separation, gas-liquid separation, and inert gas separation of the decomposition products; A product collection unit connected to the product separation unit, and the product collection unit is used to collect solid products, liquid products, and gas products.

[0016] The method and device for continuously treating waste plastics by microwave-driven liquid metal provided by the present invention have the following beneficial effects: Continuous production: The present invention adopts a continuous feeding and discharging method, in combination with a specially designed continuous feeding unit and a microwave reaction unit, to achieve continuous production of waste plastic treatment. It has high production efficiency, can meet the needs of large-scale industrial waste plastic treatment, and the production capacity can reach 1 - 20 tons per day.

[0017] Excellent mixing effect: Diversified mixing methods (spray mixing and stirring mixing) can be flexibly selected according to the characteristics of waste plastics and treatment requirements, significantly improving the mixing uniformity of liquid metal and waste plastics, increasing the contact area, and enhancing the reaction efficiency. The decomposition rate of waste plastics is increased by 20% - 30% compared with the single mixing method.

[0018] Recyclable liquid metal: Utilizing the physical property differences between liquid metal and products, the recycling of liquid metal can be achieved through simple separation methods, reducing the treatment cost and resource waste. The recovery rate of liquid metal can reach 90% - 95%.

[0019] High reaction efficiency: Liquid metal has good fluidity, high conductivity, and thermal conductivity, enabling full contact with waste plastics and effectively increasing the catalytic area. In the microwave field, liquid metal can rapidly heat up, and at the same time, plasma is generated. The interaction between liquid metal, plasma, and waste plastics promotes the rapid breakage of waste plastic molecular chains, greatly improving the reaction efficiency. Compared with traditional methods, the decomposition rate of waste plastics is increased by 3 - 5 times.

[0020] Good product selectivity: By precisely controlling the parameters of microwave treatment, such as microwave frequency, power, reaction temperature, and time, as well as conditions such as the ratio of liquid metal to waste plastics, selective regulation of the decomposition products of waste plastics can be achieved, and the yield of high-value-added products such as pyrolysis oil is significantly increased. The pyrolysis oil yield can reach 70% - 90%.

[0021] Environmental protection and energy saving: Compared with traditional landfill and incineration treatment methods, the present invention can convert waste plastics into valuable products, reducing environmental pollution. At the same time, the microwave treatment process features fast heating speed and high energy utilization rate. Compared with traditional heating methods, the energy consumption is reduced by 30% - 60%, meeting the requirements of environmental protection and energy saving. Brief description of the drawings

[0022] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0023] Figure 1It is a schematic flow chart of the method for continuously treating waste plastics by microwave-driven liquid metal provided by the present invention.

[0024] Figure 2 It is a structural block diagram of the device for continuously treating waste plastics by microwave-driven liquid metal provided by the present invention.

[0025] Reference numerals: 1. Waste plastic pretreatment unit; 11. Sorting equipment; 12. Crusher; 13. Cleaning machine; 14. Dryer; 2. Liquid metal supplement unit; 21. Liquid metal storage tank; 22. Liquid metal pumping device; 23. Flowmeter; 3. Mixing unit; 31. Stirring and mixing module; 32. Spray mixing module; 4. Continuous feeding unit; 41. Screw conveyor; 42. Belt conveyor; 5. Microwave reaction unit; 51. Microwave generator; 52. Microwave reaction cavity; 53. Temperature sensor; 54. Pressure sensor; 6. Liquid metal circulation unit; 61. Liquid metal collection device; 62. Liquid metal purification device; 63. Liquid metal circulation pumping device; 7. Product separation unit; 71. Gas-solid separation device; 72. Gas-liquid separation device; 73. Inert gas separation device; 8. Product collection unit; 81. Solid product collection device; 82. Liquid product collection device; 83. Gas product collection device. Detailed implementation manners

[0026] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without any creative work belong to the scope of protection of the present invention.

[0027] The following Figure 1 describes the method for continuously treating waste plastics by microwave-driven liquid metal of the present invention.

[0028] Figure 1 It is a schematic flow chart of the method for continuously treating waste plastics by microwave-driven liquid metal provided by the present invention. As Figure 1 shown, the method includes the following: Step S1. Pretreat the waste plastic raw materials to obtain dry waste plastic particles.

[0029] In step S1, the waste plastic raw materials are sorted to remove impurities therein; the waste plastic raw materials are crushed to form small waste plastic pieces; the small waste plastic pieces are cleaned to remove dirt and dust on the surface and then dried to obtain dry waste plastic particles.

[0030] Among them, the waste plastic is one or more of polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyurethane, and resin plastic.

[0031] Step S2: In an inert gas environment, the waste plastic particles are mixed evenly with the liquid metal to obtain a mixed material.

[0032] In step S2, the mixing method adopts at least one of spray mixing and stirring mixing, and the dry waste plastic particles and the liquid metal are mixed evenly in a certain proportion.

[0033] When the mixing method is single spray mixing, first the liquid metal is atomized by a spray device and evenly sprayed on the surface of the waste plastic particles, and then the material is continuously fed into the microwave reaction cavity through a continuous feeding unit.

[0034] When the mixing method is single stirring mixing, the waste plastic particles and the liquid metal are put into a stirring device together, and through the rotation of the stirring paddle, the two are fully contacted and mixed evenly, and then the material is continuously fed into the microwave reaction cavity through a continuous feeding device.

[0035] When the mixing method is the synchronous use of both stirring mixing and spray mixing, first the liquid metal is atomized by a spray device and evenly sprayed on the surface of the waste plastic particles, and through the rotation of the stirring paddle, the liquid metal and the waste plastic particles are further contacted and mixed evenly, and then the material is continuously fed into the microwave reaction cavity through a continuous feeding device.

[0036] In step S2, the liquid metal is one or more of metals or alloys with a melting point lower than 300 °C, such as gallium, indium, tin, sodium, potassium, sodium-potassium alloy, gallium-based alloy (gallium-aluminum, gallium-zinc, gallium-indium, gallium-tin, gallium-indium-tin, gallium-indium-aluminum, gallium-tin-aluminum, gallium-indium-zinc, gallium-tin-zinc, gallium-indium-tin-aluminum, gallium-indium-tin-zinc), bismuth-based alloy (bismuth-aluminum, bismuth-zinc, bismuth-indium, bismuth-tin, bismuth-indium-tin, bismuth-indium-aluminum, bismuth-tin-aluminum, bismuth-indium-zinc, bismuth-tin-zinc, bismuth-indium-tin-aluminum, bismuth-indium-tin-zinc), gallium-bismuth alloy (gallium-indium-bismuth, gallium-indium-tin-bismuth), etc., and gallium-based alloy is preferred.

[0037] In step S2, the mixing mass ratio of the liquid metal to the waste plastic is 1:1 - 1:30, and preferably 1:20.

[0038] Step S3: Continuously feed the mixed material into the microwave reaction cavity, and irradiate the mixed material with microwaves to decompose the waste plastic particles to obtain decomposition products.

[0039] When continuously feeding materials, equipment such as a screw conveyor can be used to control the feeding speed of the materials, enabling the materials to enter the microwave reaction chamber at a stable speed. The feeding speed is 1 - 500 kg / h, preferably 300 kg / h.

[0040] In the microwave reaction chamber, a microwave generator is used to generate microwaves to irradiate the materials during the continuous transportation process. By controlling parameters such as the microwave power, reaction temperature, material transportation speed, and microwave activation time, the decomposition rate and product selectivity of waste plastics are adjusted. The microwave frequency is 915 MHz or 2.45 GHz, and the microwave power is 100 - 2000 W, preferably 1000 W. Under the action of microwaves, the liquid metal rapidly heats up, and at the same time, plasma is excited to generate and interact with the waste plastics, prompting the molecular chains of the waste plastics to break, thereby realizing the decomposition of the waste plastics. The reaction temperature is controlled at 300 - 500 °C, and the reaction time is 5 - 30 min, preferably 15 min. By controlling parameters such as the microwave power, reaction temperature, and reaction time, the decomposition efficiency and product selectivity of waste plastics are improved.

[0041] S4. Due to the physical property differences between the liquid metal and the decomposition products, the liquid metal spontaneously separates from the decomposition products, mixes with the waste plastic particles again, and enters the next cycle.

[0042] In step S4, the liquid metal can also be purified, preferably by centrifugal separation, distillation, etc., to remove a small amount of oil products carried by the liquid metal during the pumping process, thereby separating the liquid metal from the products and realizing the recycling of the liquid metal.

[0043] S5. The decomposition products are subjected to gas-solid separation, gas-liquid separation, and inert gas separation. The separated inert gas re-enters S2 and enters the next cycle.

[0044] The product separation device adopts a gas-solid separation device, a gas-liquid separation device, and an inert gas separation device. Preferably, a cyclone separator is used as the gas-solid separation device to separate the gaseous products and solid products in the products. The solid products are mainly carbon slag, etc., and the gaseous products enter the gas-liquid separation device; preferably, a condenser is used as the gas-liquid separation device to cool and liquefy the gaseous products to obtain liquid products such as pyrolysis oil, etc.; the unliquefied gaseous products enter the inert gas separation device to obtain gas products and inert gas, and the inert gas re-enters the reaction system to provide an inert atmosphere for the reaction.

[0045] The following describes the device for continuously treating waste plastics by microwave-driven liquid metal provided by the present invention. The device for continuously treating waste plastics by microwave-driven liquid metal described below can be mutually corresponding and referred to with the method for continuously treating waste plastics by microwave-driven liquid metal described above.

[0046] In a second aspect of the present invention, an embodiment provides a device for continuously treating waste plastics driven by microwaves using liquid metal, which includes a waste plastic pretreatment unit 1, a liquid metal supplement unit 2, a mixing unit 3, a continuous feeding unit 4, a microwave reaction unit 5, a liquid metal circulation unit 6, a product separation unit 7, and a product collection unit 8.

[0047] The waste plastic pretreatment unit 1 is used for pretreating waste plastic raw materials to obtain dry waste plastic particles.

[0048] The liquid metal supplement unit 2 is used to provide liquid metal.

[0049] The mixing unit 3 is internally provided with an inert gas; the mixing unit is connected to the waste plastic pretreatment unit and the liquid metal supplement unit.

[0050] One end of the continuous feeding unit 4 is connected to the mixing unit 3; the microwave reaction unit 5 has a microwave reaction chamber 52, and the microwave reaction chamber 52 is connected to the other end of the continuous feeding unit 4; under the action of microwaves, the liquid metal and the waste plastic react to decompose the waste plastic to obtain decomposition products.

[0051] The liquid metal circulation unit 6 is connected to the microwave reaction unit 5 and the liquid metal supplement unit 2. The liquid metal circulation unit 6 is used to collect the liquid metal separated from the decomposition products and pump the separated liquid metal to the liquid metal supplement unit 2.

[0052] The product separation unit 7 is connected to the microwave reaction unit 5. The product separation unit 7 is used for gas-solid separation, gas-liquid separation, and inert gas separation of the decomposition products.

[0053] The product collection unit 8 is connected to the product separation unit. The product collection unit 8 is used to collect solid products, liquid products, and gas products.

[0054] The device for continuously treating waste plastics driven by microwaves using liquid metal provided by the present invention uniformly mixes dry waste material particles with liquid metal through the mixing unit 3, and realizes continuous production of waste plastic treatment through the continuous feeding unit 4 and the microwave reaction unit 5, improves production efficiency, can meet the requirements of large-scale industrial treatment of waste plastics, realizes efficient, environmentally friendly, and continuous treatment of waste plastics, improves the recycling rate of waste plastics, and reduces the treatment cost.

[0055] It should be noted that the inside of the liquid metal supplement unit 2, the mixing unit 3, the continuous feeding unit 4, the microwave reaction unit 5, and the liquid metal circulation unit 6 is an inert atmosphere, preferably nitrogen or argon.

[0056] In the microwave reaction unit 5, the liquid metal has good fluidity, high electrical conductivity and thermal conductivity, and can come into full contact with waste plastics, effectively increasing the catalytic area. In the microwave field, the liquid metal can rapidly heat up, and at the same time, it can stimulate the generation of plasma. The interaction among the liquid metal, plasma and waste plastics promotes the rapid breaking of the molecular chains of waste plastics, greatly improving the reaction efficiency. Compared with the traditional method, the decomposition rate of waste plastics is increased by 3-5 times.

[0057] Through the settings of the liquid metal circulation unit 6, the product separation unit 7 and the product collection unit 8, by using the differences in physical properties between the liquid metal and the decomposition products, the recycling of the liquid metal is realized through separation methods, reducing the treatment cost and resource waste. The recovery rate of the liquid metal can reach 90%-95%.

[0058] Furthermore, the waste plastic pretreatment unit 1 includes a sorting device 11, a crusher 12, a washing machine 13 and a dryer 14. The sorting device 11 is used to remove impurities in the waste plastics; the crusher 12 is used to crush the waste plastics into block-shaped waste plastics; the washing machine 13 is used to wash the block-shaped waste plastics to obtain the washed waste plastics; the dryer 14 is used to dry the washed waste plastics.

[0059] Furthermore, the liquid metal replenishment unit 2 includes a liquid metal storage tank 21, a liquid metal pump 22 and a flowmeter 23. The liquid metal storage tank 21 is used to store the liquid metal, which is used to supplement the liquid metal for the system when the equipment is first started, so as to realize the mixing with waste plastic particles. The liquid metal pump 22 is used to pump the liquid metal; the flowmeter 23 is used to adjust the proportion of the liquid metal entering the mixing unit, that is, to control the material ratio of the liquid metal and the plastic in the production process. The liquid metal storage tank 21 is preferably made of stainless steel; the liquid metal pump 22 is preferably an electromagnetic pump or a mechanical pump; the flowmeter 23 is preferably a mass flowmeter.

[0060] Furthermore, the mixing unit 3 includes at least one of a stirring and mixing module 31 and a spraying and mixing module 32. The flowmeter 23 can also distribute the proportion of the liquid metal entering the stirring and mixing module 31 and the spraying and mixing module 32. The diverse mixing methods can be flexibly selected according to the characteristics of the waste plastics and the treatment requirements, significantly improving the mixing uniformity of the liquid metal and the waste plastics, increasing the contact area, and enhancing the reaction efficiency. The decomposition rate of the waste plastics is increased by 20%-30% compared with the single mixing method.

[0061] Further, the stirring and mixing module 31 includes a stirring tank and a stirrer. The stirring tank is used to hold waste plastic particles and liquid metal, and the stirrer is used for stirring and mixing. The spraying and mixing module 32 includes a spraying pump and an atomizing nozzle. The spraying pump is used to pressurize the liquid metal, and the atomizing nozzle is connected to the spraying pump. The atomizing nozzle sprays the pressurized liquid metal onto the waste plastic particles to make the liquid metal and the waste plastic particles as evenly mixed as possible.

[0062] Further, the continuous feeding unit 4 includes a first conveyor 41 and a second conveyor 42. The first conveyor 41 is connected to the mixing unit and is used to convey the mixture to the microwave reaction unit 5, and convey the mixed materials into the microwave reaction chamber 52 at a stable speed. The first conveyor 41 is preferably a screw conveyor or a belt conveyor. The second conveyor 42 is arranged inside the microwave reaction unit 5 and is used to convey the reaction materials in the microwave reaction chamber 52 at a stable speed. The second conveyor 42 is preferably a belt conveyor. The first conveyor 41 can control the feeding speed of the mixture so that the mixture enters the microwave reaction chamber 52 at a stable speed, and the feeding speed is 1 - 500 kg / h, preferably 300 kg / h.

[0063] Further, the microwave reaction unit 5 includes a microwave generator 51, a temperature sensor 53 and a pressure sensor 54. The microwave generator 51 is located inside the microwave reaction chamber 52. The microwave generator 51 generates microwaves, and the microwave reaction chamber 52 provides a reaction space for the materials. Under the action of the microwaves, the liquid metal and the waste plastic react. The waste plastic decomposes into products while moving forward, and the liquid metal spontaneously separates from the products. The temperature sensor 53 and the pressure sensor 54 are respectively used to monitor the temperature and pressure in the microwave reaction chamber, and both the temperature sensor 53 and the pressure sensor 54 are connected to the microwave generator 51 for feedback regulation of the on / off and microwave power of the microwave generator 51.

[0064] Among them, the microwave frequency generated by the microwave generator 51 is 915 MHz or 2.45 GHz, the microwave power is 100 - 2000 W, preferably 1000 W; the reaction temperature is controlled at 300 - 500 °C, and the microwave on - time is 1 - 20 h.

[0065] Further, the liquid metal circulation unit 6 includes a liquid metal collection device 61, a purification device 62 and a pumping device 63. The liquid metal collection device 61 is used to collect the liquid metal that has spontaneously separated from the decomposition products at the bottom of the microwave reaction chamber 52. The purification device 62 is connected to the liquid metal collection device 61. The purification device 62 is used to remove the oil products carried by the liquid metal, and the purification device 62 is preferably a centrifugal separator. The pumping device 63 is connected to the purification device 62, and the pumping device 63 is used to pump the liquid metal to the liquid metal replenishment unit. The pumping device 63 is preferably a mechanical pump or an electromagnetic pump.

[0066] Furthermore, the product separation unit 7 includes a gas-solid separation device 71, a gas-liquid separation device 72, and an inert gas separation device 73. The gas-solid separation device 71 is used to separate the gaseous product and the solid product of the decomposition product; the gas-liquid separation device 72 is used to cool and liquefy the gaseous product to obtain a liquid product; the inert gas separation device 73 is used to separate the gas product from the inert gas. The gas-solid separation device 71 is preferably a cyclone separator, the gas-liquid separation device 72 is preferably a condenser, and the inert gas separation device 73 is preferably a cryogenic separator.

[0067] Furthermore, the product collection unit 8 includes a solid product collection device 81, a liquid product collection device 82, and a gas product collection device 83. The solid product collection device 81 is connected to the gas-solid separation device 71. The gas-solid separation device 71 separates the decomposition product once to obtain a solid product and a first gaseous product; the solid product is collected by the solid product collection device 81. The liquid product collection device 82 is connected to the gas-liquid separation device 72; the gas-liquid separation device 72 separates the first gaseous product a second time to obtain a second gaseous product and a liquid product, and the liquid product is collected by the gas product collection device 82. The gas product collection device 83 is connected to the inert gas separation device 73. The second gaseous product is separated three times by the inert gas separation device 73 to obtain an inert gas and a third gaseous product, and the third gaseous product is collected by the gas product collection device 83, and the inert gas re-enters the mixing unit 3 for the next cycle.

[0068] The device for continuously treating waste plastics by microwave-driven liquid metal provided by the embodiment of the present invention can solve the problems existing in the waste plastic treatment technology, such as inability to continuously produce, low reaction efficiency, poor product selectivity, etc., realize the efficient, environmentally friendly and continuous treatment of waste plastics, improve the recycling rate of waste plastics, and reduce the treatment cost.

[0069] The present invention will be further described below through specific embodiments. The following embodiments can be mutually corresponded and referred to the device and method for continuously treating waste plastics by microwave-driven liquid metal described above.

[0070] Example 1 (Stirring and Mixing) (1) Pretreatment: Collect a batch of waste polyethylene plastics, use the sorting device 11 to remove impurities such as metal sheets and paper sheets mixed in them, and then crush them into small pieces with a side length of about 5 mm by the crusher 12. Put the crushed plastic small pieces into the washing machine 13, rinse them with clean water for 5 minutes to remove the surface dirt, and then send them into the dryer 14 to dry at 80 °C for 2 h to obtain dry waste plastic particles. Take 100 kg of dry waste plastic particles and put them into the mixing tank in the stirring and mixing module 31 of 3-1.

[0071] (2)Supplementary liquid metal: Pump 10 kg of gallium-based alloy liquid metal from the liquid metal supplementary unit 2 into the mixing tank in the stirring and mixing module 31 at a ratio of 10:1 of waste plastic particles to liquid metal.

[0072] (3)Stirring and mixing: Use the stirrer in the stirring and mixing module 31 to stir at a speed of 300 r / min for 10 min to make the two fully mixed and uniform.

[0073] (4)Continuous feeding: Continuously feed the mixed material into the microwave reaction chamber 52 in the microwave reaction unit 5 at a speed of 100 kg / h through the screw conveyor 41 in the continuous feeding unit 4.

[0074] (5)Microwave treatment: The microwave generator 51 in the microwave reaction unit 5 generates microwaves with a frequency of 2.45 GHz and an initial power of 600 W to irradiate the material on the belt conveyor 42 in the continuous feeding unit 4. Use the temperature sensor 53 to detect the temperature of the microwave reaction chamber 52, and control the temperature of the microwave reaction chamber 52 at 300 °C by adjusting the power of the microwave generator 51 in real time. The belt conveyor 42 maintains a certain speed so that the residence time of the material in the microwave reaction chamber 52 is 30 min. Use the pressure sensor 52 to monitor the pressure in the microwave reaction chamber 52. When the pressure is less than 2 MPa, keep the microwave generator 51 in the on state. When the pressure is greater than 2 MPa, keep the microwave generator 51 in the off state.

[0075] (6)Liquid metal circulation: Use the liquid metal collection device 61 to collect the liquid metal that has self-separated from the reaction products in the microwave reaction chamber 52; use the liquid metal purification device 62 (centrifugal separator) to remove the small amount of oil products carried by the liquid metal; use the liquid metal circulation pumping device 63 (electromagnetic pump) to pump the liquid metal to the liquid metal supplementary unit 2, and the liquid metal recovery rate is 90%.

[0076] (7)Product separation: The products after microwave treatment are discharged from the discharge port and first enter the gas-solid separation device 71 (cyclone separator) to separate the gaseous products and solid products. The solid product is mainly carbon slag with a yield of 0.4 wt%, which is collected by the solid product collection device 81. The gaseous products enter the gas-liquid separation device 72 (condenser) and are cooled and liquefied at -10 °C to obtain the liquid product pyrolysis oil with an oil yield of 80 wt%, which is collected by the liquid product collection device 82. The unliquefied gaseous products enter the inert gas separation device 73 to obtain gas products and inert gas. The yield of the gas products is 19.6 wt%, which is collected by the solid product collection device 83. The inert gas (purity of 99%) re-enters the mixing unit 3, the continuous feeding unit 4, and the microwave reaction unit 5 to provide an inert atmosphere for the device.

[0077] Example 2 (Spray Mixing) (1) Pretreatment: Collect a batch of waste polypropylene plastics, use the sorting device 11 to remove impurities such as metal flakes and paper scraps mixed in them, and then crush them into small pieces with a side length of about 8 mm by the crusher 12. Put the crushed plastic small pieces into the cleaning machine 13, rinse them with clean water for 10 min to remove surface dirt, and then send them into the dryer 14 to dry at 100 °C for 1.5 h to obtain dry waste plastic particles. Take 200 kg of dry waste plastic particles and put them into the mixing tank of the spray mixing module 32.

[0078] (2) Supplementary Liquid Metal: According to the ratio of waste plastic particles to liquid metal of 10:1, pump 20 kg of gallium-based alloy liquid metal from the liquid metal supplementary unit 2 to the spray mixing module 32.

[0079] (3) Spray Mixing: Pressurized by the spray pump in the spray mixing module 32, 20 kg of gallium-indium alloy liquid metal is evenly sprayed on 200 kg of dry waste plastic particles through the atomizing nozzle to achieve mixing.

[0080] (4) Continuous Feeding: The mixed materials are continuously fed into the microwave reaction cavity 52 in the microwave reaction unit 5 at a speed of 300 kg / h through the screw conveyor 41 in the continuous feeding unit 4.

[0081] (5) Microwave Treatment: The microwave generator 51 in the microwave reaction unit 5 generates microwaves with a frequency of 915 MHz and an initial power of 1000 W, and irradiates the materials on the belt conveyor 42 in the continuous feeding unit 4. Use the temperature sensor 53 to detect the temperature of the microwave reaction cavity 52, and control the temperature of the microwave reaction cavity 52 at 400 °C by adjusting the power of the microwave generator 51 in real time. The belt conveyor 52 maintains a certain speed so that the residence time of the materials in the microwave reaction cavity 52 is 25 min. Use the pressure sensor 53 to monitor the pressure in the microwave reaction cavity 52. When the pressure is less than 2 MPa, keep the microwave generator 51 in the on state. When the pressure is greater than 2 MPa, keep the microwave generator in the off state.

[0082] (6) Liquid Metal Recycling: Use the liquid metal collection device 61 to collect the liquid metal that has been self-separated from the reaction products in the microwave reaction cavity 52; use the liquid metal purification device 62 (centrifugal separator) to remove the small amount of oil products carried by the liquid metal; use the liquid metal circulating pump device 63 (electromagnetic pump) to pump the liquid metal to the liquid metal supplementary unit 2, and the liquid metal recovery rate is 92%.

[0083] (7) Product separation: The product after microwave treatment is discharged from the discharge port and first enters the gas-solid separation device 71 (cyclone separator) to separate the gaseous product and the solid product. The solid product is mainly carbon slag with a yield of 0.8 wt%, which is collected by the solid product collection device 81. The gaseous product enters the gas-liquid separation device 72 (condenser) and is cooled and liquefied at -10 °C to obtain the liquid product pyrolysis oil with an oil yield of 85 wt%, which is collected by the liquid product collection device 82. The unliquefied gaseous product enters the inert gas separation device 73 to obtain the gas product and the inert gas. The yield of the gas product is 14.2 wt%, which is collected by the solid product collection device 83. The inert gas (purity 99%) re-enters the mixing unit 3, the continuous feeding unit 4, and the microwave reaction unit 5 to provide an inert atmosphere for the device.

[0084] Example 3 (Combination of mixing methods) (1) Pretreatment: Collect a batch of mixed waste plastics (including polyethylene, polypropylene, etc.), use the sorting equipment 11 to remove impurities such as metal flakes and paper pieces mixed in them, and then crush them into small pieces with a side length of about 10 mm by the crusher 12. Put the crushed plastic small pieces into the washing machine 13, rinse with clean water for 15 min to remove the surface dirt, and then send them to the dryer 14 to dry at 120 °C for 1 h to obtain dry waste plastic particles. Take 300 kg of dry waste plastic particles and put them into the mixing tank of the mixing unit 3.

[0085] (2) Supplementary liquid metal: According to the ratio of waste plastic particles to liquid metal of 10:1, pump 20 kg of gallium-based alloy liquid metal from the liquid metal supplementary unit 2 into the mixing tank of the 3-1 stirring and mixing module, and pump 10 kg of gallium-based alloy liquid metal into the spray mixing module 32.

[0086] (3) Combination of stirring and mixing and spray mixing: First, pre-mix 300 kg of waste plastic particles and 20 kg of liquid metal in the mixing tank of the stirring and mixing module 31 at 200 r / min for 5 min. At the same time, pressurize through the spray pump in the spray mixing module 32, and 10 kg of gallium-indium alloy liquid metal is evenly sprayed on the premixed material through the atomizing nozzle to achieve mixing.

[0087] (4) Continuous feeding: Continuously feed the mixed material into the microwave reaction chamber 52 of the microwave reaction unit 5 at a speed of 500 kg / h through the screw conveyor 41 in the continuous feeding unit 4.

[0088] (5) Microwave treatment: The microwave generator 51 in the microwave reaction unit 5 generates microwaves with a frequency of 2.45 GHz and an initial power of 800 W, and irradiates the materials on the belt conveyor 42 in the continuous feeding unit 4. The temperature sensor 53 is used to detect the temperature of the microwave reaction chamber 52, and by adjusting the power of the microwave generator 51 in real time, the temperature of the microwave reaction chamber 52 is controlled at 450 °C. The belt conveyor 42 maintains a certain speed so that the residence time of the materials in the microwave reaction chamber 52 is 20 min. The pressure sensor 54 is used to monitor the pressure in the microwave reaction chamber 52. When the pressure is less than 2 MPa, the microwave generator is kept in the on state, and when the pressure is greater than 2 MPa, the microwave generator is kept in the off state.

[0089] (6) Liquid metal circulation: The liquid metal collection device 61 is used to collect the liquid metal that is self-separated from the reaction products in the microwave reaction chamber 52; the liquid metal purification device 62 (centrifugal separator) is used to remove the small amount of oil products carried by the liquid metal; the liquid metal circulation pumping device 63 (electromagnetic pump) pumps the liquid metal to the liquid metal replenishment unit 2, and the liquid metal recovery rate is 95%.

[0090] (7) Product separation: The products after microwave treatment are discharged from the discharge port and first enter the gas-solid separation device 71 (cyclone separator) to separate the gaseous products and solid products. The solid product is mainly carbon slag with a yield of 0.6 wt%, and is collected by the solid product collection device 81. The gaseous products enter the gas-liquid separation device 72 (condenser) and are cooled and liquefied at -10 °C to obtain the liquid product pyrolysis oil with an oil yield of 78.5 wt%, which is collected by the liquid product collection device 82. The unliquefied gaseous products enter the inert gas separation device 73 to obtain gas products and inert gas. The yield of the gas products is 20.9 wt%, which is collected by the solid product collection device 83, and the inert gas (with a purity of 99%) re-enters the mixing unit 3, continuous feeding unit 4, and microwave reaction unit 5 to provide an inert atmosphere for the device.

[0091] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific situations.

[0092] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "mode", "specific mode", or "some modes", etc., mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or mode are included in at least one embodiment or mode of the embodiments of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or mode. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or modes. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or modes described in this specification and the features of different embodiments or modes.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for continuously treating waste plastics by microwave-driven liquid metal, characterized in that, Including: S1. Pretreat the waste plastic raw materials to obtain dry waste plastic particles; S2. Under an inert gas environment, uniformly mix the waste plastic particles with liquid metal to obtain a mixed material; S3. Continuously feed the mixed material into a microwave reaction cavity, and irradiate the mixed material with microwaves to decompose the waste plastic particles to obtain decomposition products; S4. Due to the physical property differences between the liquid metal and the decomposition products, the liquid metal spontaneously separates from the decomposition products, mixes with the waste plastic particles again, and enters the next cycle; S5. Perform gas-solid separation, gas-liquid separation, and inert gas separation on the decomposition products. The separated inert gas re-enters S2 and enters the next cycle.

2. The method for continuously treating waste plastics by microwave-driven liquid metal according to claim 1, characterized in that In the step S1, it includes: Sort the waste plastic raw materials to remove impurities therein; Crush the waste plastic raw materials to form small waste plastic pieces; Clean the small waste plastic pieces to remove dirt and dust on the surface, and perform drying treatment to obtain dry waste plastic particles.

3. The method for continuously treating waste plastics by microwave-driven liquid metal according to claim 1, characterized in that, In the step S2, it includes: The liquid metal is a metal or alloy with a melting point lower than 300 °C, and the mass ratio of the liquid metal to the waste plastic particles is 1:1 - 1:

30.

4. The method for continuously treating waste plastics by microwave-driven liquid metal according to claim 1, wherein, In the step S3, the feeding speed is 1 - 500 kg / h.

5. The method for continuously treating waste plastics by microwave-driven liquid metal according to claim 1, characterized in that In the step S4, the liquid metal is purified before being mixed with the waste plastic particles.

6. The method for continuously treating waste plastics by microwave-driven liquid metal according to claim 1, characterized in that, In the step S5, it includes: Perform gas-solid separation on the decomposition products, collect the solid products, and obtain the first gaseous products; Perform secondary separation on the first gaseous products, cool and liquefy the first gaseous products to obtain liquid products and second gaseous products; Perform tertiary separation on the second gaseous products to obtain third gaseous products and inert gas; the inert gas re-enters the reaction system to provide an inert environment for the reaction.

7. The method for continuously treating waste plastics by microwave-driven liquid metal according to claim 1, characterized in that, In the step S1, the waste plastic is one or more of polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyurethane, and resin plastic.

8. The method for continuously treating waste plastics by microwave-driven liquid metal according to claim 1, characterized in that In the step S2, the mixing method adopts at least one of spray mixing and stirring mixing.

9. The method for continuously treating waste plastics by microwave-driven liquid metal according to claim 1, wherein, In the step S2, the reaction temperature is controlled at 300 - 500 °C, and the reaction time is 5 - 30 min.

10. An apparatus for a method of continuously treating waste plastics by microwave-driven liquid metal according to any one of claims 1-9, characterized in that, Including: A waste plastic pretreatment unit (1) for pretreating waste plastic raw materials to obtain dry waste plastic particles; A liquid metal replenishment unit (2) for replenishing liquid metal; A mixing unit (3) with inert gas inside; the mixing unit (2) is connected to the waste plastic pretreatment unit (1) and the liquid metal replenishment unit (2); A continuous feeding unit (4) with one end connected to the mixing unit (3); A microwave reaction unit (5) having a microwave reaction cavity (52), and the microwave reaction cavity (52) is connected to the other end of the continuous feeding unit (4); under the action of microwaves, the liquid metal and the waste plastic react to decompose the waste plastic to obtain decomposition products; A liquid metal circulation unit (6) connected to the microwave reaction unit (5) and the liquid metal replenishment unit (2); The liquid metal circulation unit (6) is used to collect the liquid metal after self-separation from the decomposition products and pump the separated liquid metal to the liquid metal replenishment unit (2); A product separation unit (7), connected to the microwave reaction unit (5), the product separation unit (7) is used for gas-solid separation, gas-liquid separation and inert gas separation of the decomposition products; A product collection unit (8), connected to the product separation unit (7), the product collection unit (8) is used to collect solid products, liquid products and gas products.

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