Forced dechlorination system for plastic pyrolysis

Abstract

The utility model relates to the technical field of plastic pyrolysis dechlorination, in particular to a plastic pyrolysis forced dechlorination system which comprises a dechlorination tower, a pyrolysis unit, a dechlorination agent bin and a desalted water unit are all communicated with the dechlorination tower through pipelines, and an air outlet of the dechlorination tower is communicated with a first high-temperature membrane dust remover. A discharge port of the 1 # high-temperature membrane dust remover is respectively communicated with the dechlorination tower and the dechlorination agent waste bin, a gas outlet of the dechlorination agent waste bin is communicated with the 2 # high-temperature membrane dust remover, and a discharge port of the 2 # high-temperature membrane dust remover is communicated with the dechlorination agent waste bin. According to the utility model, the pyrolysis gas is forcibly extracted, so that the hydrogen chloride conversion rate in the pyrolysis process of the chlorine-containing waste plastics is improved, the converted hydrogen chloride is quickly absorbed through the dechlorination tower, and the unreacted dechlorination agent is recycled, so that the absorption efficiency of the hydrogen chloride is improved, and the generation of a large amount of chlorinated hydrocarbons in the pyrolysis process of the chlorine-containing waste plastics is effectively inhibited; the overhigh total chlorine content of the pyrolysis product is avoided, and meanwhile, the utilization rate of the dechlorinating agent is also improved.

Description

Technical Field

[0001] The utility model relates to the technical field of plastic pyrolysis dechlorination, in particular to a plastic pyrolysis forced dechlorination system. Background Art

[0002] Since its invention, plastic has rapidly become one of the indispensable materials in people's lives due to its stable properties, low cost and easy portability. While bringing convenience to people, plastic has also caused serious damage to the environment. The existing methods for treating plastic waste mainly include landfill, incineration and recycling. Landfill and incineration will cause serious environmental pollution and waste a lot of land and energy. High-value recycling has become a hot topic in recent years. High-value recycling can be divided into energy recovery, mechanical recovery and chemical recovery. Among them, energy recovery is incineration, which not only pollutes the environment but also increases carbon emissions; mechanical recovery, also known as physical recovery, reshapes and reuses waste plastics. The recycled plastics it produces will not only have poor performance, but can only be downgraded for use, and it is difficult to make up for the cost of recycling and treatment; chemical recovery refers to the method of decomposing waste plastics into small molecules or monomers, and then preparing fuel oil, chemicals, etc. from small molecules. This method can convert waste plastics into higher-value products and can handle mixed and contaminated low-end waste plastics, becoming the focus of research in various fields in recent years. Among them, pyrolysis of plastics is the core technology of chemical recycling.

[0003] Chlorine is very common in waste plastics, mainly from PVC products and various chlorine-containing additives. The chlorine content in PVC alone exceeds 50%. These chlorine elements form organic chlorine (such as chloroform, dichloroethane, trichloroethane) and inorganic chlorine (in the form of hydrogen chloride) during the pyrolysis process. Hydrogen chloride and organic chlorine enter the pyrolysis product, which will cause catalyst poisoning and serious equipment corrosion during the product utilization process, resulting in a huge increase in product utilization investment and operating costs.

[0004] The control of chlorine mainly focuses on the following three aspects:

[0005] First, we need to control the source of waste plastic raw materials, limit the recycling of chlorine-containing plastics, and reduce the introduction of chlorine; this method greatly increases the cost of chemical recycling raw materials due to limited raw materials, and at the same time makes many chlorine-containing plastics unrecyclable.

[0006] Secondly, under the premise of source control, chlorine is removed during the pyrolysis process to reduce the amount of chlorine entering the pyrolysis product.

[0007] Finally, after taking the first two measures, chlorine is removed during subsequent product processing to reduce catalyst poisoning and equipment corrosion.

[0008] From the above, it can be seen that in the pyrolysis process, improving the pyrolysis dechlorination efficiency becomes the key. If the dechlorination efficiency of the pyrolysis process can be improved, raw materials with high chlorine content can be used, the source of waste plastics can be increased, the cost of chemical recycling can be reduced, and the application scope of chemical recycling can be increased; the chlorine in the pyrolysis product can be removed to the existing fuel oil and chemical chlorine index of <10ppm during the pyrolysis process, which can greatly reduce the investment and operating costs of pyrolysis product processing.

[0009] The basic rules for the conversion of chlorine during the pyrolysis of chlorine-containing waste plastics are as follows. Taking PVC as an example, the following is an explanation:

[0010] The pyrolysis of PVC resin starts at 200-220℃ and can be divided into three stages: the first weightless stage (200-320℃), the stable stage (320-420℃) and the second weightless stage (420-600℃). The pyrolysis reaction is a first-order reaction. HCl is produced in the first weightless stage. Since the binding energy of the C-Cl bond in the PVC structure is lower than that of the C-C and C-H bonds, the C-Cl bond will first break to produce chlorine free radicals, which will further generate HCl. The second weightless stage is characterized by the reformation of some structures. In this stage, HCl may undergo secondary reactions with other olefins, aromatics, etc., and eventually produce various chlorinated hydrocarbons.

[0011] The reaction chemical formula in the first weightlessness stage is as follows:

[0012] CnHmCLx——CnH(mx)+xHCL

[0013] From the above process and reaction, we can know that 1. During the pyrolysis of plastic, chlorine is preferentially released and forms HCl in the gas phase. 2. The HCl precipitation process is a chemical reaction with increased volume; 2. The HCl formed in the gas phase will repolymerize with the organic matter generated in the pyrolysis process to form chlorinated hydrocarbons as the temperature rises and the residence time increases.

[0014] Based on the above characteristics, in order to reduce the entry of chlorine into the pyrolysis product, a well-known and commonly used method is to react the generated HCl with one or more alkaline solid substances to form alkaline chlorides, and fix the chlorine in the gaseous HCl in the alkaline dechlorination agent.

[0015] The existing plastic dechlorination technology has the following defects: 1. The chlorine element cannot be quickly converted into HCl during the pyrolysis of chlorine-containing waste plastics. 2. The converted HCl cannot be quickly absorbed by the dechlorination agent and is inhibited from repolymerizing to generate chlorinated hydrocarbons, and the total chlorine in the pyrolysis product is higher than 10 ppm. Utility Model Content

[0016] In order to solve at least one of the above technical problems, the utility model proposes a plastic pyrolysis forced dechlorination system, the purpose of which is to increase the rate of conversion of chlorine-containing waste plastics into hydrogen chloride during pyrolysis, quickly absorb the converted hydrogen chloride through a dechlorination tower, and recycle the unreacted dechlorinating agent, thereby solving the problems of the generation of a large amount of chlorinated hydrocarbons during pyrolysis of chlorine-containing waste plastics, excessively high total chlorine content of pyrolysis products, and low utilization rate of dechlorinating agents.

[0017] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0018] A plastic pyrolysis forced dechlorination system, comprising a pyrolysis unit for pyrolyzing plastics, a dechlorinating agent bin for storing dechlorinating agents, a desalted water unit, a dechlorinating tower, a No. 1 high-temperature membrane dust collector, a dechlorinating agent waste bin and a No. 2 high-temperature membrane dust collector;

[0019] The pyrolysis unit is connected to the air inlet of the dechlorination tower through a first pyrolysis gas pipeline provided with a first high-temperature fan, so as to pump the high-chlorine pyrolysis gas in the pyrolysis unit into the dechlorination tower and maintain the pressure in the pyrolysis unit at a preset pressure value; and pump the low-chlorine pyrolysis gas to a subsequent process through a second pyrolysis gas pipeline provided with a second high-temperature fan;

[0020] The dechlorinating agent bin is connected to the dechlorinating tower through a pipeline, and is used to transport the dechlorinating agent into the dechlorinating tower to dechlorinate the high-chlorine pyrolysis gas to form dechlorinated pyrolysis gas;

[0021] The desalted water unit is connected to the dechlorination tower through a desalted water pipeline, and is used to spray desalted water onto the surface of the dechlorinating agent in the dechlorination tower;

[0022] The gas outlet of the dechlorination tower is connected to the gas inlet of the 1# high-temperature membrane dust collector through a pipeline, and the 1# high-temperature membrane dust collector is used to perform gas-solid separation on the dechlorination pyrolysis gas to form primary dust removal pyrolysis gas and primary dechlorination agent ash; the gas outlet of the 1# high-temperature membrane dust collector is connected to the third high-temperature fan and the subsequent process through pipelines, and the primary dust removal pyrolysis gas is pressurized by the third high-temperature fan to form a conveying gas source;

[0023] The discharge port of the 1# high-temperature membrane dust collector is connected to the feed port of the dechlorination tower through the first dust removal discharge pipeline, so as to transport the primary dechlorination agent ash having a dechlorination agent content higher than the preset content to the dechlorination tower under the action of the conveying gas source; and is connected to the feed port of the dechlorination agent waste bin through the second dust removal discharge pipeline, so as to transport the primary dechlorination agent ash having a dechlorination agent content lower than the preset content to the dechlorination agent waste bin under the action of the conveying gas source;

[0024] The gas outlet of the dechlorinating agent waste bin is connected to the 2# high-temperature membrane dust collector, and the 2# high-temperature membrane dust collector is used to perform gas-solid separation on the primary dust removal pyrolysis gas serving as the conveying gas source to form secondary dust removal pyrolysis gas and secondary dechlorinating agent ash; the secondary dust removal pyrolysis gas is transported to the post-process through the fourth high-temperature fan, and the secondary dechlorinating agent ash is discharged to the dechlorinating agent waste bin through the discharge port of the 2# high-temperature membrane dust collector.

[0025] Preferably, the pyrolysis unit includes a pyrolyzer, which is provided with a plurality of 1# exhaust pipes connected to the first pyrolysis gas pipeline and a plurality of 2# exhaust pipes connected to the second pyrolysis gas pipeline; the 1# exhaust pipe and the 2# exhaust pipe are both provided with a pyrolysis gas pressure gauge and a pyrolysis gas thermometer for measuring the pyrolysis gas pressure and gas temperature in the pipe, and a 1# gas analyzer is provided on the first pyrolysis gas pipeline.

[0026] Preferably, it also includes a dechlorinating agent preparation unit for preparing the dechlorinating agent, the discharge port of the dechlorinating agent preparation unit is connected to the 3# rotary feeding valve, the dechlorinating agent 1# bin, the 2# rotary feeding valve, the dechlorinating agent 2# bin and the 1# rotary feeding valve in sequence through pipelines along the flow direction of the dechlorinating agent; the discharge port of the 1# rotary feeding valve is connected to the feed port of the 1# pneumatic conveying valve, the air inlet of the 1# pneumatic conveying valve is connected to the air outlet of the third high-temperature fan through a pipeline provided with a 1# conveying gas control valve, and the discharge port of the 1# pneumatic conveying valve is connected to the dechlorinating tower.

[0027] Preferably, it also includes a nitrogen gas storage tank, the gas outlet of which is connected to the discharge port of the 3# rotary feeding valve through a pipeline provided with a 1# nitrogen control valve, and is connected to the feed port of the 2# rotary feeding valve through a pipeline provided with a 2# nitrogen control valve; the dechlorinating agent 1# bin is provided with a 1# material level meter and a 2# gas analyzer, and the dechlorinating agent 2# bin is provided with a 2# material level meter.

[0028] Preferably, a 4# rotary feeding valve is provided on the first dust removal discharge pipeline, the discharge port of the 4# rotary feeding valve is connected with the feed port of the 2# pneumatic conveying valve, the discharge port of the 2# pneumatic conveying valve is connected with the feed port of the dechlorination tower, and the 2# pneumatic conveying valve is connected with the air outlet of the third high-temperature fan through the 2# conveying gas control valve.

[0029] Preferably, a 5# rotary feeding valve is provided on the second dust removal pipeline, the outlet of the 5# rotary feeding valve is connected with the inlet of the 3# pneumatic conveying valve, the outlet of the 3# pneumatic conveying valve is connected with the dechlorination agent waste bin, and the air inlet of the 3# pneumatic conveying valve is connected with the air outlet of the third high-temperature fan through the 3# conveying air control valve.

[0030] Preferably, the gas outlet of the nitrogen storage tank is connected to the gas inlet of the 3# pneumatic conveying valve through the 3# nitrogen control valve.

[0031] Preferably, a temperature regulating water control valve is provided on the desalted water pipeline, and a high chlorine control valve and a low chlorine control valve are provided on the 1# exhaust pipe and the 2# exhaust pipe respectively; a dechlorination tower thermometer is provided in the dechlorination tower; and the dechlorination agent waste bin is provided with a 4# material level meter, a 4# gas analyzer and a waste bin pressure gauge.

[0032] Preferably, a funnel-shaped ash storage bin for storing primary dechlorinating agent ash is provided at the lower part of the 1# high-temperature membrane dust collector, and the ash storage bin is provided with a 3# material level meter and a sampling analyzer; a 3# gas analyzer and a 1# shut-off valve are provided respectively between the air outlet of the 2# high-temperature membrane dust collector and the air inlet of the fourth high-temperature fan; the discharge port of the dechlorinating agent waste bin is connected to the solid waste bin through a pipeline provided with a 6# rotary feeding valve.

[0033] Preferably, the preset pressure range is 0-1 Kpa, and the preset content range is 5%-10%.

[0034] Compared with the prior art, the utility model has the following beneficial effects:

[0035] 1. The utility model utilizes the characteristic that low pressure is conducive to the generation of hydrogen chloride, and quickly extracts the high-content hydrogen chloride pyrolysis gas generated during the pyrolysis process, thereby reducing the concentration of hydrogen chloride in the gas phase, and controlling the pressure in the pyrolyzer to be 0-1Kpa, thereby reducing the contact time between the high-chlorine pyrolysis gas and the molten waste plastic. At the same time, with 320°C as the critical temperature, the high-chlorine pyrolysis gas and the low-chlorine pyrolysis gas are extracted separately, effectively reducing the back-mixing of the two and reducing the chance of re-polymerization to generate chlorinated hydrocarbons.

[0036] 2. The utility model uses nitrogen as the protective gas source of the dechlorination agent bin and uses the clean primary dust removal pyrolysis gas pressurized by the third high-temperature fan as the conveying power to convey the dechlorination agent to the dechlorination tower, thereby reducing the amount of other impurity gases that are easy to react with the dechlorination agent in the dechlorination tower during the conveying process. The operation is simple, safe and easy to control.

[0037] 3. The utility model sprays dechlorinated water onto the dechlorinating agent in the dechlorinating tower to form an instantaneous liquid film on the surface of the alkaline dechlorinating agent, which is conducive to the rapid reaction of hydrogen chloride with it and improves the efficiency of dechlorination; by adding excess dechlorinating agent, the full absorption of hydrogen chloride is guaranteed, so that the total chlorine after dechlorination is less than 10ppm, reducing the investment and operating costs of dechlorination required in the refined oil process to avoid catalyst poisoning, and reducing the serious corrosion of high chlorine to oil refining equipment, thereby reducing the investment and operating costs of subsequent refining of pyrolysis products. At the same time, efficient dechlorination enables high-chlorine plastics to achieve high-value recovery through chemical recovery, broadening the variety of chemically recycled plastic raw materials.

[0038] 4. The utility model measures the dechlorinating agent content in the primary dechlorinating agent ash by a sampling analyzer, and transports the primary dechlorinating agent ash with a dechlorinating agent content higher than a predetermined content to the dechlorinating agent tower for recycling through a transporting gas source, thereby improving the utilization rate of the dechlorinating agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a structural schematic diagram of a plastic pyrolysis forced dechlorination system;

[0040] In the figure: 1, pyrolysis unit; 1-1, high chlorine control valve; 1-2, low chlorine control valve; 1-3, pyrolysis gas pressure gauge; 1-4, pyrolysis gas temperature gauge; 1-5, first high temperature fan; 1-6, second high temperature fan; 1-7, 1# exhaust pipe; 1-8, 2# exhaust pipe; 1-9, first pyrolysis gas pipeline; 1-9-1, 1# gas analyzer; 1-10, second pyrolysis gas pipeline;

[0041] 2. Dechlorinating agent preparation unit; 2-1, 3# rotary feeder valve; 2-2, dechlorinating agent 1# bin; 2-2-1, 1# material level meter; 2-2-2, 2# gas analyzer; 2-2-3, 1# nitrogen control valve; 2-2-4, 2# nitrogen control valve; 2-3, 2# rotary feeder valve; 2-4, dechlorinating agent 2# bin; 2-4-1, 2# material level meter; 2-5, 1# rotary feeder valve; 2-6, 1# pneumatic conveying valve; 2-6-1, 1# conveying gas control valve;

[0042] 3. Dechlorination tower; 3-1. Dechlorination tower thermometer; 3-2. Temperature-adjusting water control valve; 3-3. 1# high-temperature membrane dust collector; 3-3-1. 3# material level meter; 3-3-2. Sampling analyzer; 3-3-3. 4# rotary feed valve; 3-3-4. 2# pneumatic conveying valve; 3-3-4-1. 2# conveying gas control valve; 3-4. The third high-temperature fan;

[0043] 4. Dechlorinating agent waste bin; 4-1, 4# material level meter; 4-2, 6# rotary feeding valve; 4-3, 5# rotary feeding valve; 4-4, 3# pneumatic conveying valve; 4-4-1, 3# conveying gas control valve; 4-5, 3# nitrogen control valve; 4-6, 1# shut-off valve; 4-7, 2# high-temperature membrane dust collector; 4-7-1, 3# gas analyzer; 4-7-2, the fourth high-temperature fan; 4-8, 4# gas analyzer; 4-9, waste bin pressure gauge. DETAILED DESCRIPTION

[0044] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. It is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments of the present invention.

[0045] Please refer to Figure 1 As shown, a plastic pyrolysis forced dechlorination system includes a pyrolysis unit 1 for pyrolysis reaction of plastic, a dechlorination agent bin for storing dechlorination agent, a desalted water unit, a dechlorination tower 3, a 1# high temperature membrane dust collector 3-3, a dechlorination agent waste bin 4 and a 2# high temperature membrane dust collector 4-7.

[0046] It can be seen that the main part of the dechlorination work of this system is roughly: dechlorination agent preparation and dechlorination agent warehouse feeding, plastic pyrolysis, pyrolysis gas dechlorination, pyrolysis gas gas-solid separation and dechlorination agent waste recovery. Figure 1 Detailed description.

[0047] (1) Plastic pyrolysis

[0048] The pyrolysis unit 1 is connected to the air inlet of the dechlorination tower 3 through a first pyrolysis gas pipeline 1-9 provided with a first high-temperature fan 1-5, so as to pump the high-chlorine pyrolysis gas in the pyrolysis unit 1 into the dechlorination tower 3; and pump the low-chlorine pyrolysis gas to the subsequent process through a second pyrolysis gas pipeline 1-10 provided with a second high-temperature fan 1-6.

[0049] The above-mentioned pyrolysis unit 1 includes a pyrolyzer, which is provided with a plurality of 1# exhaust pipes 1-7 connected to the first pyrolysis gas pipeline 1-9 and a plurality of 2# exhaust pipes 1-8 connected to the second pyrolysis gas pipeline 1-10, wherein the number of 1# exhaust pipes 1-7 and 2# exhaust pipes 1-8 can be determined according to the size of the pyrolyzer itself. The spacing between the 1# exhaust pipe 1-7 and the 2# exhaust pipe 1-8 in the present application is 300mm-500mm, and the pipe diameter is 150mm-200mm.

[0050] Both the 1# exhaust pipe 1-7 and the 2# exhaust pipe 1-8 are provided with a pyrolysis gas pressure gauge 1-3 and a pyrolysis gas thermometer 1-4 for measuring the pyrolysis gas pressure and gas temperature in the pipe, and the first pyrolysis gas pipeline 1-9 is provided with a 1# gas analyzer 1-9-1. And the 1# exhaust pipe 1-7 and the 2# exhaust pipe 1-8 are respectively provided with a high chlorine control valve 1-1 and a low chlorine control valve 1-2. For ease of control, the above-mentioned pyrolysis gas thermometer 1-4, pyrolysis gas pressure gauge 1-3, high chlorine control valve 1-1 and low chlorine control valve 1-2 are all connected to the control system. The following pipeline valves and measuring devices are also connected to the control system.

[0051] As mentioned above, after the plastic enters the pyrolyzer, pyrolysis starts at 200-220℃ and can be divided into three stages: the first weightlessness stage (200-320℃), the stable stage (320-420℃) and the second weightlessness stage (420-600℃). The pyrolysis reaction is a first-order reaction. From the pyrolysis reaction formula, it can be seen that the gas volume increases during the pyrolysis reaction. Therefore, reducing the pressure is conducive to the pyrolysis reaction. Therefore, the pressure in the pyrolyzer can be reduced by forcibly sucking the pyrolysis gas generated by pyrolysis.

[0052] Combined with the reaction temperatures and reaction products of the three stages of pyrolysis, this embodiment takes 320°C as the critical temperature, and extracts high-chlorine pyrolysis gas and low-chlorine pyrolysis gas from the gas in the pyrolyzer. It should be noted that the high-chlorine pyrolysis gas here refers to the pyrolysis gas with a high hydrogen chloride content, and similarly, the low-chlorine pyrolysis gas refers to the pyrolysis gas with a low hydrogen chloride content.

[0053] Specifically, the temperature in the pyrolyzer is measured by the pyrolysis gas thermometer 1-4 of the 1# exhaust pipe 1-7 and the 2# exhaust pipe 1-8. When the temperature is 200-320°C, the content of hydrogen chloride in the pyrolysis gas is relatively high. At this time, the low-chlorine control valve 1-2 is closed by the control system, and the high-chlorine pyrolysis gas is pumped into the dechlorination tower 3. Similarly, when the temperature is above 320°C, the high-chlorine control valve 1-1 is closed by the control system, and the low-chlorine pyrolysis gas is pumped into the dechlorination tower 3.

[0054] At the same time, the pressure in the pyrolysis gas is measured by the pyrolysis gas pressure gauge 1-3. When the pressure value is close to 0Kpa, the channel volume of the high chlorine control valve 1-1 or the low chlorine control valve 1-2 is reduced to increase the pressure in the pyrolyzer; when the pressure value is 1Kpa, the channel volume of the high chlorine control valve 1-1 or the low chlorine control valve 1-2 is increased through the control system to reduce the pressure in the pyrolyzer.

[0055] Through the above operation, the contact time between high-chlorine pyrolysis gas and molten waste plastic can be significantly reduced. At the same time, with 320℃ as the critical temperature, high-chlorine pyrolysis gas and low-chlorine pyrolysis gas are extracted separately, which effectively reduces the back-mixing of the two and reduces the chance of re-polymerization to generate chlorinated hydrocarbons.

[0056] (2) Preparation of dechlorinating agent and feeding of dechlorinating agent bin

[0057] In this embodiment, the dechlorinating agent is provided by the dechlorinating agent preparation unit 2, and the discharge port of the dechlorinating agent preparation unit 2 is connected to the 3# rotary feeding valve 2-1, the dechlorinating agent 1# bin 2-2, the 2# rotary feeding valve 2-3, the dechlorinating agent 2# bin 2-4 and the 1# rotary feeding valve 2-5 in sequence along the flow direction of the dechlorinating agent through the pipeline; the discharge port of the 1# rotary feeding valve 2-5 is connected to the feed port of the 1# pneumatic conveying valve 2-6, and the air inlet of the 1# pneumatic conveying valve 2-6 is connected to the conveying gas source through the pipeline provided with the 1# conveying gas control valve 2-6-1, and the discharge port of the 1# pneumatic conveying valve 2-6 is connected to the dechlorinating tower 3. Among them, the dechlorinating agent 1# bin 2-2 is provided with a 1# material level meter 2-2-1 and a 2# gas analyzer 2-2-2, and the dechlorinating agent 2# bin 2-4 is provided with a 2# material level meter 2-4-1.

[0058] It should be noted that the dechlorinating agent in the present application can be one or more of metal oxides, such as oxides of potassium, sodium, calcium, magnesium, iron, etc., metal hydroxides, such as sodium hydroxide, and metal carbonates, which are mixed in a certain proportion and then processed into particles with a particle size of 1-100um by the dechlorinating agent preparation unit 2. The preparation of the dechlorinating agent belongs to the prior art and is not the focus of protection of this application, and this application will not be repeated here.

[0059] In this embodiment, the feed of the dechlorinating agent uses nitrogen as the protective gas source, wherein the gas outlet of the nitrogen gas storage tank is connected to the outlet of the 3# rotary feeding valve 2-1 through a pipeline provided with a 1# nitrogen control valve 2-2-3, and is connected to the feed port of the 2# rotary feeding valve 2-3 through a pipeline provided with a 2# nitrogen control valve 2-2-4;

[0060] The feeding process of the above dechlorinating agent 1# warehouse 2-2 and dechlorinating agent 2# warehouse 2-4 is as follows:

[0061] When the 1# material level meter 2-2-1 of the dechlorinating agent 1# bin 2-2 shows that the material level is in the range of 1 / 4-1 / 3, it is necessary to feed it, and the 3# rotary feeding valve 2-1 and the 2# nitrogen control valve 2-2-4 are closed through the control system, and the 1# nitrogen control valve 2-2-3 and the 2# rotary feeding valve 2-3 are opened, and the pyrolysis gas in the dechlorinating agent 1# bin 2-2 is pressed into the dechlorinating agent 2# bin 2-4 from the top of the dechlorinating agent 1# bin 2-2 with nitrogen. When the 2# gas analyzer 2-2-2 measures that the nitrogen content is above 95%, the 2# rotary feeding valve 2-3 and the 1# nitrogen control valve 2-2-3 are closed, and the 3# rotary feeding valve 2-1 is opened, and the dechlorinating agent processed in the dechlorinating agent preparation unit 2 enters the dechlorinating agent 1# bin 2-2.

[0062] When the 1# material level meter 2-2-1 of the dechlorinating agent 1# bin 2-2 shows that the material level is in the range of 2 / 4-3 / 4, open the 2# nitrogen control valve 2-2-4, and use nitrogen to press the air in the dechlorinating agent 1# bin 2-2 into the dechlorinating agent preparation unit 2 from the bottom of the dechlorinating agent 1# bin 2-2. When the 2# gas analyzer 2-2-2 measures that the nitrogen content is more than 95%, close the 3# rotary feeding valve 2-1 and the 2# nitrogen control valve 2-2-4, open the 2# rotary feeding valve 2-3, and the dechlorinating agent in the dechlorinating agent 1# bin 2-2 enters the dechlorinating agent 2# bin 2-4.

[0063] When the 2# material level meter 2-4-1 of the dechlorinating agent 2# bin 2-4 shows that the material level is in the range of 2 / 4-3 / 4, close the 2# rotary feeding valve 2-3, and repeat the above operation to replenish the dechlorinating agent in the dechlorinating agent 1# bin 2-2 according to the material level situation.

[0064] In this embodiment, nitrogen is used as the protective gas source of the dechlorination agent bin, and the clean primary dust removal pyrolysis gas pressurized by the third high-temperature fan 3-4 is used as the conveying power to convey the dechlorination agent to the dechlorination tower 3, thereby reducing the impurity gas carried during the conveying process that is easy to react with the dechlorination agent in the dechlorination tower 3. This operation is simple, safe, and easy to control.

[0065] (3) Dechlorination of pyrolysis gas

[0066] The prepared dechlorinating agent and the high-chlorine pyrolysis gas in the pyrolysis gas are transported to the dechlorination tower 3 to undergo a dechlorination reaction, as follows:

[0067] Open the high chlorine control valve 1-1, and transport the pyrolysis gas with a high hydrogen chloride content to the dechlorination tower 3 under the action of the first high-temperature fan 1-5, and measure the hydrogen chloride content in the first pyrolysis gas pipeline 1-9 according to the 1# gas analyzer 1-9-1.

[0068] In order to remove the hydrogen chloride in the high-chlorine pyrolysis gas to the greatest extent, an excess of dechlorinating agent is used to react with hydrogen chloride. In this embodiment, the molar ratio of the dechlorinating agent to hydrogen chloride is 3.5-7.

[0069] The control system opens the 1# rotary feeding valve 2-5, and controls the opening of the 1# rotary feeding valve 2-5 according to the above ratio, and transports the dechlorinating agent to the dechlorination tower 3 under the action of the conveying gas source and the 1# pneumatic conveying valve 2-6.

[0070] The gas velocity of the high-chlorine thermal decomposition gas can be specifically determined according to the density and particle size of the dechlorinating agent particles and the temperature and density of the gas. In this embodiment, the gas velocity of the high-chlorine thermal decomposition gas is 40-50 m / s.

[0071] It can be understood that the high-speed high-chlorine pyrolysis gas collides violently with the high-chlorine pyrolysis gas, so that the dechlorinating agent and the high-chlorine pyrolysis gas fully contact and react. Taking the calcium-based alkaline dechlorinating agent as an example, the reaction is as follows: Ca(OH) 2+HCl——CaCl 2 +H 2 O.

[0072] As is known to all, in the double-membrane theory of gas-liquid mass transfer reaction, gas absorption is the process of transferring the absorbent in the gas phase to the liquid phase through the phase interface. When the gas and liquid are in contact with each other, even if the main body of the fluid is already turbulent, there are still stable gas stagnation layers (gas films) and liquid retention layers (liquid films) on both sides of the gas-liquid phase interface. Since the absorption process is that the absorbent molecules move from the main body of the gas phase to the surface of the gas film, and then reach the gas-liquid interface through the gas film in the form of molecular diffusion, the absorbent dissolves into the liquid phase at the interface, and then enters the main body of the liquid phase through the liquid film in the form of molecular diffusion from the liquid phase interface. In the absence of liquid, the reaction between hydrogen chloride and alkaline dechlorinating agent is a gas-solid phase, and can only pass through the micropores on the surface of the dechlorinating agent to provide sufficient specific surface area to create a reaction that is conducive to the absorption of hydrogen chloride. After the desalted water is sprayed, although it will evaporate rapidly during the spraying process, it can still come into brief contact with the dechlorinating agent, forming a liquid film on the surface of the dechlorinating agent, creating conditions for the formation of a double membrane, which is beneficial to the absorption of hydrogen chloride, thereby promoting the chemical absorption reaction of hydrogen chloride and the alkaline solid dechlorinating agent.

[0073] Based on the above principle, in order to further improve the reaction efficiency of high-chlorine pyrolysis gas and dechlorinating agent, in this embodiment, desalted water from the desalted water unit is sprayed into the dechlorination tower 3 through the desalted water pipeline. At the same time, in order to ensure that the desalted water can fully contact with the dechlorinating agent, the injection port of the desalted water and the delivery port of the dechlorinating agent in this embodiment are at the same horizontal plane. The desalted water is sprayed into the dechlorination tower 3, and the gas temperature in the dechlorination tower 3 is reduced by about 5-10°C. The temperature drop can be specifically calculated by the difference between the temperature value measured by the dechlorination tower 3 thermometer set in the dechlorination tower 3 and the temperature value of the high-chlorine pyrolysis gas.

[0074] In order to facilitate the control of the injection amount of desalted water, a temperature regulating water control valve 3-2 is provided on the desalted water pipeline.

[0075] In this embodiment, by spraying the desalted water after temperature adjustment into the dechlorination tower 3 and adding an excessive amount of dechlorinating agent, the hydrogen chloride is fully absorbed, so that the total chlorine after dechlorination is less than 10ppm, reducing the investment and operating costs of dechlorination required for the refined oil process to avoid catalyst poisoning, and reducing the serious corrosion of high chlorine to the oil refining equipment, thereby reducing the investment and operating costs of the subsequent refining of the pyrolysis product. At the same time, efficient dechlorination enables high-chlorine plastics to achieve high-value recovery through chemical recovery, broadening the variety of chemically recycled plastic raw materials.

[0076] (4) Gas-solid separation of pyrolysis gas

[0077] The mixed gas discharged from the outlet of the dechlorination tower 3 will carry a certain amount of reacted and unreacted dechlorination agent into the 1# high-temperature membrane dust collector 3-3, and gas-solid separation will be carried out in the 1# high-temperature membrane dust collector 3-3.

[0078] The primary dust removal pyrolysis gas separated by the 1# high temperature membrane dust collector 3-3 has dust less than 10mg / Nm3 and hydrogen chloride less than 10ppm / Nm3. Among them, a part of the primary dust removal pyrolysis gas enters the third high temperature fan 3-4 through the outlet of the 1# high temperature membrane dust collector 3-3 and is pressurized to 30Kpa as a conveying gas source, and the remaining clean primary dust removal pyrolysis gas is mixed with the low-chlorine pyrolysis gas from the second high temperature fan 1-6 to go to the post-process.

[0079] The separated solid reaction and unreacted dechlorination agent fall into the funnel-shaped ash storage bin at the bottom of the 1# high temperature membrane dust collector 3-3. In order to facilitate timely adjustment of the material level in the ash storage bin, the above ash storage bin is provided with a 3# material level meter 3-3-1.

[0080] Specifically, in this embodiment, the material level of the 3# material level meter 3-3-1 in the ash storage bin of the 1# high temperature membrane dust collector 3-3 is controlled between 1 / 2 and 2 / 3. When the material level is lower than 1 / 2, the 4# rotary feed valve 3-3-3 reduces the opening, and when the material level is greater than 2 / 3, the 4# rotary feed valve 3-3-3 increases the opening.

[0081] At the same time, in order to improve the utilization rate of the dechlorination agent, a sampling analyzer 3-3-2 is provided in the above-mentioned ash storage bin. The discharge port of the 1# high-temperature membrane dust collector 3-3 is connected with the feed port of the dechlorination tower 3 through the first dust removal discharge pipeline, and the first dust removal discharge pipeline is provided with a 4# rotary feeding valve 3-3-3, and the discharge port of the 4# rotary feeding valve 3-3-3 is connected with the feed port of the 2# pneumatic conveying valve 3-3-4, and the discharge port of the 2# pneumatic conveying valve 3-3-4 is connected with the feed port of the dechlorination tower 3, and the 2# pneumatic conveying valve 3-3-4 is connected with the air outlet of the third high-temperature fan 3-4 through the 2# conveying gas control valve 3-3-4-1.

[0082] The discharge port of 1# high-temperature membrane dust collector 3-3 is connected with the feed port of dechlorinating agent waste bin 4 through the second dust removal discharge pipeline, and a 5# rotary feeding valve 4-3 is arranged on the second dust removal pipeline, and the discharge port of 5# rotary feeding valve 4-3 is connected with the feed port of 3# pneumatic conveying valve 4-4, and the discharge port of 3# pneumatic conveying valve 4-4 is connected with dechlorinating agent waste bin 4, and the air inlet of 3# pneumatic conveying valve 4-4 is connected with the air outlet of the third high-temperature fan 3-4 through 3# conveying air control valve 4-4-1.

[0083] Specifically, the preset content of the dechlorinating agent in the primary dechlorinating agent ash in this embodiment is in the range of 5%-10%. However, the specific value of the preset content needs to be determined in combination with the pressure difference of the dechlorinating tower 3 and the content of hydrogen chloride in the pyrolysis gas out of the dechlorinating tower 3. The following specifically describes the ash discharge path of the primary dechlorinating agent ash with a preset content of 8%.

[0084] When the sampling analyzer 3-3-2 measures that the effective dechlorinating agent content in the primary dechlorinating agent ash is less than 8%, open the 5# rotary feeding valve 4-3 and the 3# conveying gas control valve 4-4-1, and the primary dechlorinating agent ash of the unreacted alkaline dechlorinating agent and the reacted dechlorinating agent in the ash storage bin at the bottom of the 1# high-temperature membrane dust collector 3-3 enters the dechlorinating agent waste bin 4 through the 3# pneumatic conveying valve 4-4 under the action of the conveying gas source and is taken out.

[0085] During the discharge process of the primary dechlorinating agent ash containing less than 8% of effective dechlorinating agent, the effective dechlorinating agent content in the primary dechlorinating agent ash in the dechlorinating tower 3 will gradually increase.

[0086] When the sampling analyzer 3-3-2 measures that the effective dechlorinating agent content in the primary dechlorinating agent ash is greater than 10%, close the 5# rotary feeding valve 4-3, stop taking out the primary dechlorinating agent ash, wait for the 5# rotary feeding valve 4-3 to be closed, delay 30 seconds and then close the 3# conveying gas control valve 4-4-1, in order to blow away the residual unreacted alkaline dechlorinating agent and the reacted dechlorinating agent mixed material ash.

[0087] Open 4# rotary feeding valve 3-3-3 and 2# conveying gas control valve 3-3-4-1, and the unreacted alkaline dechlorinating agent and the primary dechlorinating agent ash of the reacted dechlorinating agent in the ash storage bin at the bottom of 1# high-temperature membrane dust collector 3-3 enter the dechlorinating tower 3 for recycling through 2# pneumatic conveying valve 3-3-4 under the action of conveying gas source.

[0088] In this embodiment, the dechlorinating agent content in the primary dechlorinating agent ash is determined by sampling analyzer 3-3-2, and the primary dechlorinating agent ash with a dechlorinating agent content higher than the predetermined content is transported to the dechlorinating agent tower for recycling through the transporting gas source, thereby improving the utilization rate of the dechlorinating agent.

[0089] (5) Recovery of dechlorination agent waste

[0090] The primary dechlorinating agent ash with a dechlorinating agent content lower than the preset content enters the dechlorinating agent waste bin 4 through the 3# pneumatic conveying valve 4-4 under the action of the conveying gas source. The gas outlet of the dechlorinating agent waste bin 4 is connected to the middle and upper part of the 2# high-temperature membrane dust collector 4-7, and the 2# high-temperature membrane dust collector 4-7 is used to perform gas-solid separation on the primary dust removal pyrolysis gas as the conveying gas source to form secondary dust removal pyrolysis gas and secondary dechlorinating agent ash.

[0091] A 3# gas analyzer 4-7-1 and a 1# shut-off valve 4-6 are provided between the outlet of the 2# high-temperature membrane dust collector 4-7 and the inlet of the fourth high-temperature fan 4-7-2, and the secondary dust removal pyrolysis gas is transported to the subsequent process through the fourth high-temperature fan 4-7-2.

[0092] The secondary dechlorinating agent ash separated by the 2# high temperature membrane dust collector 4-7 is discharged to the dechlorinating agent waste bin 4 through the funnel-shaped ash storage bin at the bottom of the 2# high temperature membrane dust collector 4-7. The discharge port of the dechlorinating agent waste bin 4 is connected to the solid waste bin through a pipeline provided with a 6# rotary feed valve 4-2.

[0093] Specifically, when the dechlorinating agent waste bin 4 is fed, the 1# shutoff valve 4-6 is opened and the fourth high-temperature fan 4-7-2 is started. The primary dechlorinating agent ash with low effective dechlorinating agent content entrained by the primary dechlorinating agent pyrolysis gas as the conveying gas enters the 2# high-temperature membrane dust collector 4-7.

[0094] The secondary dust removal pyrolysis gas after dust removal enters the fourth high-temperature fan 4-7-2 from the outlet of the 2# high-temperature membrane dust collector 4-7 through the 1# shut-off valve 4-6. Under the suction action of the fourth high-temperature fan 4-7-2, the secondary dust removal pyrolysis gas and the low-chlorine pyrolysis gas are mixed and enter the subsequent process.

[0095] The unreacted alkaline dechlorinating agent and the reacted dechlorinating agent mixture separated by gas-solid separation in the 2# high-temperature membrane dust collector 4-7 enter the dechlorinating agent waste bin 4 through the discharge port of the funnel-shaped ash storage bin at the lower part of the 2# high-temperature membrane dust collector 4-7.

[0096] When the chlorine waste bin 4 stops feeding, the fourth high-temperature blower 4-7-2 is turned off through the control system.

[0097] In order to facilitate the control of the material level of the dechlorinating agent waste bin 4, the dechlorinating agent waste bin 4 in this embodiment is provided with a 4# material level meter 4-1, a 4# gas analyzer 4-8 and a waste bin pressure gauge 4-9, and the gas outlet of the nitrogen storage tank is connected with the gas inlet of the 3# pneumatic conveying valve 4-4 through the 3# nitrogen control valve 4-5.

[0098] Specifically, when the 4# material level meter 4-1 detects that the material level of the dechlorination agent waste bin 4 is at 1 / 2-2 / 3, the 3# nitrogen control valve 4-5 is opened through the control system to purge the ash removal system, and the purged exhaust gas and the secondary dust removal pyrolysis gas are mixed with the low-chlorine pyrolysis gas through the same path and then enter the subsequent process.

[0099] When the nitrogen content displayed by 3# gas analyzer 4-7-1 and 4# gas analyzer 4-8 is greater than 95%, the 3# nitrogen control valve 4-5 is closed, and the pressure in the dechlorinating agent waste bin 4 is maintained at a slight positive pressure through the waste bin pressure gauge 4-9. In this embodiment, the slight positive pressure range is 0.1-1Kpa. At this time, the 1# shut-off valve 4-6 is closed, the 6# rotary feeding valve 4-2 is opened, and the secondary dechlorinating agent ash in the dechlorinating agent waste bin 4 is discharged to the solid waste warehouse. It should be noted that during the discharge of the secondary dechlorinating agent ash, the chlorinating agent waste bin is maintained in a slight positive pressure state, and the nitrogen content analyzed by 3# gas analyzer 4-7-1 and 4# gas analyzer 4-8 is more than 95%. When the 4# material level meter 4-1 detects that the material level of the dechlorinating agent waste bin 4 is less than 1 / 3, the control system closes the 6# rotary feeding valve 4-2 and the 3# nitrogen control valve 4-5.

[0100] The utility model utilizes the characteristic that low pressure is conducive to the generation of hydrogen chloride, and quickly extracts the hydrogen chloride pyrolysis gas with a high content generated during the pyrolysis process, thereby reducing the concentration of hydrogen chloride in the gas phase, and controlling the pressure in the pyrolyzer to be 0-1Kpa, thereby reducing the contact time between the high-chlorine pyrolysis gas and the molten waste plastic. At the same time, with 320°C as the critical temperature, the high-chlorine pyrolysis gas and the low-chlorine pyrolysis gas are extracted separately, effectively reducing the back-mixing of the two and reducing the chance of re-polymerization to generate chlorinated hydrocarbons.

[0101] By using nitrogen as the protective gas source of the dechlorination agent bin and the clean primary dust removal pyrolysis gas pressurized by the third high-temperature fan 3-4 as the conveying power, the dechlorination agent is conveyed to the dechlorination tower 3, thereby reducing the impurity gases carried during the conveying process that are easy to react with the dechlorination agent in the dechlorination tower 3. This operation is simple, safe and easy to control.

[0102] By spraying the dechlorinating agent in the dechlorination tower 3 with the desalted water after temperature adjustment, an instantaneous liquid film is formed on the surface of the alkaline dechlorinating agent, which is conducive to the rapid reaction of hydrogen chloride with it and improves the efficiency of dechlorination; by adding an excess of dechlorinating agent, the full absorption of hydrogen chloride is guaranteed, so that the total chlorine after dechlorination is less than 10ppm, the investment and operating costs of dechlorination required to avoid catalyst poisoning in the refined oil process are reduced, and the serious corrosion of high chlorine to oil refining equipment is reduced, thereby reducing the investment and operating costs of subsequent refining of pyrolysis products. At the same time, efficient dechlorination enables high-chlorine plastics to achieve high-value recovery through chemical recovery, broadening the variety of chemically recycled plastic raw materials.

[0103] The dechlorinating agent content in the primary dechlorinating agent ash is determined by the sampling analyzer 3-3-2, and the primary dechlorinating agent ash with a dechlorinating agent content higher than the predetermined content is transported to the dechlorinating agent tower for recycling through the transporting gas source, thereby improving the utilization rate of the dechlorinating agent.

[0104] The above is a specific implementation of the embodiment of the utility model. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the utility model. These improvements and modifications should also be regarded as the scope of protection of this application.

Claims

1. A plastic pyrolysis forced dechlorination system, characterized in that: It comprises a pyrolysis unit (1) for performing pyrolysis reaction on plastic, a dechlorinating agent bin for storing a dechlorinating agent, a desalted water unit, a dechlorinating tower (3), a 1# high-temperature membrane dust collector (3-3), a dechlorinating agent waste bin (4) and a 2# high-temperature membrane dust collector (4-7); The pyrolysis unit (1) is connected to the air inlet of the dechlorination tower (3) via a first pyrolysis gas pipeline (1-9) provided with a first high-temperature fan (1-5), and is used to pump high-chlorine pyrolysis gas in the pyrolysis unit (1) into the dechlorination tower (3) and maintain the pressure in the pyrolysis unit (1) at a preset pressure value; and pump low-chlorine pyrolysis gas to a subsequent process via a second pyrolysis gas pipeline (1-10) provided with a second high-temperature fan (1-6); The dechlorinating agent bin is connected to the dechlorinating tower (3) through a pipeline, and is used to transport the dechlorinating agent into the dechlorinating tower (3) to dechlorinate the high-chlorine pyrolysis gas to form dechlorinated pyrolysis gas; The desalted water unit is connected to the dechlorination tower (3) through a desalted water pipeline, and is used to spray the desalted water onto the surface of the dechlorination agent in the dechlorination tower (3); The gas outlet of the dechlorination tower (3) is connected to the gas inlet of the 1# high-temperature membrane dust collector (3-3) through a pipeline, and the 1# high-temperature membrane dust collector (3-3) is used to perform gas-solid separation on the dechlorination pyrolysis gas to form primary dust removal pyrolysis gas and primary dechlorination agent ash; the gas outlet of the 1# high-temperature membrane dust collector (3-3) is connected to the third high-temperature fan (3-4) and the subsequent process through pipelines, and the primary dust removal pyrolysis gas is pressurized by the third high-temperature fan (3-4) to form a conveying gas source; The discharge port of the 1# high-temperature membrane dust collector (3-3) is connected to the feed port of the dechlorination tower (3) through a first dust removal discharge pipeline, and is used to transport the primary dechlorination agent ash with a dechlorination agent content higher than a preset content to the dechlorination tower (3) under the action of the transport gas source; and is connected to the feed port of the dechlorination agent waste bin (4) through a second dust removal discharge pipeline, and is used to transport the primary dechlorination agent ash with a dechlorination agent content lower than the preset content to the dechlorination agent waste bin (4) under the action of the transport gas source; The gas outlet of the dechlorinating agent waste bin (4) is connected to the No. 2 high-temperature membrane dust collector (4-7), and the No. 2 high-temperature membrane dust collector (4-7) is used to perform gas-solid separation on the primary dust removal pyrolysis gas serving as the conveying gas source to form secondary dust removal pyrolysis gas and secondary dechlorinating agent ash; the secondary dust removal pyrolysis gas is conveyed to the post-process through the fourth high-temperature fan (4-7-2), and the secondary dechlorinating agent ash is discharged to the dechlorinating agent waste bin (4) through the discharge port of the No. 2 high-temperature membrane dust collector (4-7).

2. The plastic pyrolysis forced dechlorination system according to claim 1, characterized in that: The pyrolysis unit (1) comprises a pyrolyzer, wherein the pyrolyzer is provided with a plurality of No. 1 exhaust pipes (1-7) connected to the first pyrolysis gas pipeline (1-9) and a plurality of No. 2 exhaust pipes (1-8) connected to the second pyrolysis gas pipeline (1-10); the No. 1 exhaust pipe (1-7) and the No. 2 exhaust pipe (1-8) are both provided with a pyrolysis gas pressure gauge (1-3) and a pyrolysis gas thermometer (1-4) for measuring the pyrolysis gas pressure and gas temperature in the pipe, and the first pyrolysis gas pipeline (1-9) is provided with a No. 1 gas analyzer (1-9-1).

3. The plastic pyrolysis forced dechlorination system according to claim 1, characterized in that: The invention also comprises a dechlorinating agent preparation unit (2) for preparing a dechlorinating agent, wherein the discharge port of the dechlorinating agent preparation unit (2) is connected in sequence to a 3# rotary feeding valve (2-1), a 1# dechlorinating agent bin (2-2), a 2# rotary feeding valve (2-3), a 2# dechlorinating agent bin (2-4) and a 1# rotary feeding valve (2-5) through a pipeline along the flow direction of the dechlorinating agent; the discharge port of the 1# rotary feeding valve (2-5) is connected to the feed port of a 1# pneumatic conveying valve (2-6); the air inlet of the 1# pneumatic conveying valve (2-6) is connected to the air outlet of the third high-temperature fan (3-4) through a pipeline provided with a 1# conveying gas control valve (2-6-1); and the discharge port of the 1# pneumatic conveying valve (2-6) is connected to the dechlorinating tower (3).

4. The plastic pyrolysis forced dechlorination system according to claim 3, characterized in that: It also comprises a nitrogen gas storage tank, the gas outlet of which is connected to the discharge port of the 3# rotary feed valve (2-1) through a pipeline provided with a 1# nitrogen control valve (2-2-3), and is connected to the feed port of the 2# rotary feed valve (2-3) through a pipeline provided with a 2# nitrogen control valve (2-2-4); the 1# material level meter (2-2-1) and the 2# gas analyzer (2-2-2) are provided in the 1# dechlorination agent bin (2-2), and the 2# material level meter (2-4-1) is provided in the 2# dechlorination agent bin (2-4).

5. The plastic pyrolysis forced dechlorination system according to claim 3, characterized in that: A 4# rotary feeding valve (3-3-3) is provided on the first dust removal and discharge pipeline, the discharge port of the 4# rotary feeding valve (3-3-3) is communicated with the feed port of the 2# pneumatic conveying valve (3-3-4), the discharge port of the 2# pneumatic conveying valve (3-3-4) is communicated with the feed port of the dechlorination tower (3), and the 2# pneumatic conveying valve (3-3-4) is communicated with the air outlet of the third high-temperature fan (3-4) via a 2# conveying gas control valve (3-3-4-1).

6. The plastic pyrolysis forced dechlorination system according to claim 4, characterized in that: A 5# rotary feeding valve (4-3) is provided on the second dust removal and discharge pipeline, the discharge port of the 5# rotary feeding valve (4-3) is communicated with the feed port of the 3# pneumatic conveying valve (4-4), the discharge port of the 3# pneumatic conveying valve (4-4) is communicated with the dechlorination agent waste bin (4), and the air inlet of the 3# pneumatic conveying valve (4-4) is communicated with the air outlet of the third high-temperature fan (3-4) through the 3# conveying air control valve (4-4-1).

7. The plastic pyrolysis forced dechlorination system according to claim 6, characterized in that: The gas outlet of the nitrogen gas storage tank is connected to the gas inlet of the 3# pneumatic conveying valve (4-4) through the 3# nitrogen control valve (4-5).

8. The plastic pyrolysis forced dechlorination system according to claim 2, characterized in that: The desalted water pipeline is provided with a temperature regulating water control valve (3-2); the No. 1 exhaust pipe (1-7) and the No. 2 exhaust pipe (1-8) are provided with a high chlorine control valve (1-1) and a low chlorine control valve (1-2) respectively; the dechlorination tower (3) is provided with a dechlorination tower (3) thermometer; the dechlorination agent waste bin (4) is provided with a No. 4 material level meter (4-1), a No. 4 gas analyzer (4-8) and a waste bin pressure gauge (4-9).

9. The plastic pyrolysis forced dechlorination system according to claim 1, characterized in that: A funnel-shaped ash storage bin for storing primary dechlorinating agent ash is provided at the lower part of the 1# high-temperature membrane dust collector (3-3), and the ash storage bin is provided with a 3# material level meter (3-3-1) and a sampling analyzer (3-3-2); a 3# gas analyzer (4-7-1) and a 1# shut-off valve (4-6) are provided in sequence between the air outlet of the 2# high-temperature membrane dust collector (4-7) and the air inlet of the fourth high-temperature fan (4-7-2); the discharge port of the dechlorinating agent waste bin (4) is connected to the solid waste bin through a pipeline provided with a 6# rotary feeding valve (4-2).

10. The plastic pyrolysis forced dechlorination system according to claim 1, characterized in that: The preset pressure value range is 0-1Kpa, and the preset content range is 5%-10%.

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