A method and device for coupling chlorine-containing plastics with red mud to produce added value and fix chlorine

Abstract

The present invention belongs to the technical field related to solid waste treatment, and discloses a method for coupling chlorine-containing plastics with red mud for value-added co-production and chlorine fixation, comprising: (i) a coupled pyrolysis step, wherein the chlorine-containing plastics and red mud are co-pyrolyzed, and the reaction obtains a solid residue and a dechlorinated volatile matter; (ii) the synthesis of a chlorine-resistant catalyst, wherein the solid residue is used as a catalyst carrier, and a catalyst with a chlorine-resistant effect is synthesized; (iii) a value-added co-production step, wherein the dechlorinated volatile matter and the chlorine-resistant catalyst are jointly sent to a fluidized bed reactor, fully reacted and subjected to gas-solid separation, thereby achieving a final product comprising carbon nanotubes, hydrogen-rich gas, pyrolysis oil and ferric chloride. The present invention also discloses a corresponding device. Through the present invention, it is possible to effectively solve the problems of incomplete plastic degradation, low red mud resource utilization efficiency, chlorine and chloride pollution, high catalyst cost, easy deactivation, and low product added value, and achieve coordinated degradation and continuous value-added co-production.

Description

Technical Field

[0001] The present invention belongs to the technical field related to solid waste treatment, and more specifically, relates to a method and device for coupling chlorine-containing plastics with red mud for value-added co-production and chlorine fixation. Background Art

[0002] The rapid development of human society and the acceleration of urbanization have generated a vast amount of solid waste. This has a serious impact on the environment and threatens human health and quality of life. Taking plastics as an example, the world generates over 100 million tons of plastic waste annually, and at least 60% of this waste is not effectively treated. Catalytic pyrolysis can completely degrade this solid waste while also producing high-value-added products such as carbon materials, gaseous fuels, liquid fuels, and industrial chemicals, making it an excellent development direction for solid waste treatment. However, in real waste plastics, in addition to polyolefin plastics such as polyethylene and polypropylene, approximately 10% is polyvinyl chloride, with a chlorine content of approximately 51%-57%. This results in problems such as difficulty controlling pollutants during the pyrolysis of real plastics and low recycling value.

[0003] The search found that only a small number of solutions involving the pyrolysis of chlorine-containing plastics have been proposed in the prior art. For example, CN202111232910.9 discloses a pyrolysis treatment method and system for waste plastics. This method mainly focuses on the dechlorination pretreatment of chlorine-containing plastics before pyrolysis, but ignores the low conversion efficiency and benefits of the industrialization of catalytic pyrolysis of chlorine-containing plastics. In addition, there are still many technical difficulties in the existing solutions, such as the complex dechlorination process during the catalytic pyrolysis of chlorine-containing plastics, the single pyrolysis product, the low added value, the high cost of the catalyst, the easy deactivation, etc., which greatly restrict the further development of the industrialization of waste plastic recycling.

[0004] Accordingly, this field urgently needs further research and improvement to better meet the cleaning and subsequent application requirements of chlorine-containing plastics under various complex working conditions. Summary of the Invention

[0005] In response to the above defects or needs of the prior art, the purpose of the present invention is to provide a method and device for coupling chlorine-containing plastics with red mud for value-added co-production and chlorine fixation, wherein red mud and chlorine-containing plastics are introduced for joint treatment, and targeted improvements are made to their specific process flow and key indicators of key steps. Accordingly, not only can green coordinated treatment of two types of large-volume solid wastes, chlorine-containing plastics and red mud, be achieved, but also, compared with the prior art, difficult problems such as incomplete degradation of chlorine plastics and diffusion of chlorine-containing gas pollutants during the treatment process can be better solved. At the same time, it has the advantages of high treatment efficiency, good economic feasibility and strong environmental adaptability.

[0006] To achieve the above object, according to one aspect of the present invention, a method for coupling chlorine-containing plastics with red mud for value-added co-production and chlorine fixation is provided, characterized in that the method comprises the following steps:

[0007] (i) Coupled pyrolysis step

[0008] In this step, the chlorine-containing plastic is co-pyrolyzed with red mud, wherein the metal oxides in the red mud catalyze the reaction while also reacting with the chlorides released by the pyrolysis of the chlorine-containing plastic, and after the reaction is complete, a solid residue and dechlorinated volatiles are obtained;

[0009] (ii) Synthesis steps of chlorine-resistant catalyst

[0010] In this step, the solid residue obtained in step (i) is used as a catalyst carrier, which is washed through a spray tower to remove soluble chloride salts, and then mixed with an iron salt solution and calcined to form a eutectic catalyst, which is then reduced in a hydrogen-rich atmosphere to synthesize a chlorine-resistant catalyst;

[0011] (iii) Value-added co-production steps

[0012] In this step, the dechlorinated volatiles obtained in step (i) and the chlorine-resistant catalyst synthesized in step (ii) are sent to a fluidized bed reactor for full reaction and gas-solid separation, thereby achieving the co-production of the final product comprising carbon nanotubes, hydrogen-rich gas, pyrolysis oil and ferric chloride.

[0013] Further preferably, in step (i), the components of the red mud include Fe2O3, Al2O3, SiO2, Na2O, CaO, and TiO2, and Fe2O3, Na2O, and CaO are used as the main chlorine-fixing components.

[0014] Further preferably, in step (i), when the PVC content in the chlorine-containing plastic is greater than 15%, the mass ratio between the red mud and the chlorine-containing plastic is preferably 5:3 to 2:1, and the mass proportion of Fe2O3 as the main solid chlorine component in the red mud is not less than 60%.

[0015] Further preferably, in step (ii), the synthesis process of the chlorine-resistant catalyst is preferably designed as follows:

[0016] S1: The solid residue is transferred to a spray tower through a solid collection channel to wash the soluble chloride salts. The remaining metal oxides Al2O3, SiO2, and TiO2 serve as catalyst supports.

[0017] S2: sending the catalyst carrier into the mixing chamber, adding the prepared iron salt solution and stirring and mixing;

[0018] S3: After being thoroughly stirred and mixed, the impregnation mixture is sent to the catalyst calcination chamber and calcined in an air atmosphere to form a eutectic catalyst. At this time, a small amount of coke contained in the impregnation mixture provides part of the heat for the calcination process;

[0019] S4: The eutectic catalyst is then fed into a reduction chamber, and the iron oxide forms iron spinel with the catalyst support during the reduction process, thereby completing the synthesis of the chlorine-resistant catalyst while also achieving efficient utilization of the solid residue.

[0020] Further preferably, in sub-step S2, the Fe mass fraction in the impregnation mixture is preferably 10% to 20%; in sub-step S3, the calcination temperature of the impregnation mixture is preferably 800° C. to 850° C., and the calcination time is about 3 hours.

[0021] Further preferably, in step (iii), the dechlorinated volatiles and the chlorine-resistant catalyst are preferably sent together to a fluidized bed reactor and placed in a carbon nanotube growth section, thereby enhancing the heat and mass transfer process of the gas-solid reaction by setting the fluidizing wind speed of the fluidized bed; in addition, the FeCl3 vapor generated by the dechlorinated volatiles can strengthen the active metal sites of the chlorine-resistant catalyst, thereby further improving the yield and quality of the carbon nanotubes.

[0022] Further preferably, in step (iii), the temperature of the fluidized bed reactor is preferably set to 750° C. to 850° C., and the fluidizing wind speed thereof is preferably set to 1.2 m / s to 1.5 m / s.

[0023] Further preferably, in step (iii), the condensable mixed gas obtained by the gas-solid separation is preferably introduced into a stepped condensation tower and subjected to stepped cooling with a certain temperature gradient.

[0024] Further preferably, in step (iii), when Fe2O3 is used as the main solid chlorine component, a three-level temperature gradient is preferably used to separate the liquid phase product, wherein the three-level temperature gradient is: heavy pyrolysis oil is separated at 316°C to 380°C, liquid FeCl3 is separated at 306°C to 316°C, and light pyrolysis oil is separated at above 306°C to room temperature.

[0025] According to another aspect of the present invention, there is also provided a device for coupling chlorine-containing plastics with red mud for value-added co-production and chlorine fixation, characterized in that the device comprises a pyrolysis unit, a chlorine-resistant catalyst synthesis unit and a value-added co-production unit connected in sequence, wherein:

[0026] The pyrolysis unit comprises a coupled pyrolysis reactor, which includes a mixed raw material feed inlet, a feeding auger, a pyrolysis furnace, a directional guide, a baffle, a solid product outlet, a volatile matter pressure chamber, and a pressure-stabilizing valve connected in sequence, wherein the mixed raw material feed inlet is used to feed a mixed raw material of red mud and chlorine-containing plastic; the feeding auger is used to move the mixed raw material upward in the pyrolysis furnace until the reaction is complete; the directional guide and the baffle are used to feed the pyrolysis reaction product into the solid product outlet; the volatile matter pressure chamber and the pressure-stabilizing valve enable the dechlorinated volatile matter to be supplied to the fluidized bed reactor at a certain pressure;

[0027] The chlorine-resistant catalyst synthesis unit includes a mixture inlet, a calcination chamber, a sealed transfer channel, a reduction chamber, a partition, and a catalyst outlet, which are connected in sequence. The mixture inlet is used to send the solid residue into the calcination chamber and calcine it under an air atmosphere; the sealed transfer channel is used to draw the calcined product into the reduction chamber and convert part of the iron oxide crystals into iron spinels under a reducing atmosphere; the partition is used to prolong the residence time of the eutectic catalyst in the reduction chamber so that it is sent to the catalyst outlet after being fully reduced;

[0028] The value-added co-production unit is used to fully react the dechlorinated volatiles with the chlorine-resistant catalyst, and then perform gas-solid separation, thereby achieving value-added co-production of final products including carbon nanotubes, hydrogen-rich gas, pyrolysis oil and ferric chloride.

[0029] In general, the above technical solutions conceived by the present invention have the following technical advantages compared with the existing technology:

[0030] (1) The present invention fully combines the cleaning treatment and subsequent application needs of chlorine-containing plastics under various complex working conditions, introduces red mud and chlorine-containing plastics to perform joint treatment, and further makes targeted improvements to its specific process flow and key indicators of key steps. Accordingly, it can effectively solve the problems of incomplete degradation of chlorine-containing plastics, low efficiency of red mud resource utilization, chlorine and chloride pollution, high catalyst cost, easy deactivation, and low product added value;

[0031] (2) The present invention further realizes synergistic degradation and continuous value-added co-production through reasonable structural device design of its supporting working device; in particular, by optimizing the specific structure of the coupled pyrolysis link, the coupled pyrolysis reactor can be used to enhance the interactive reaction process between chlorine-containing plastics and red mud, optimize the pyrolysis volatiles and eliminate the influence of chlorine on the subsequent catalytic quality improvement process. At the same time, the volatile pressurization cabin can provide a certain fluidization power for the pyrolysis volatiles to enter the fluidized bed;

[0032] (3) Through the present invention, many practical tests have shown that not only can the solid residue after red mud pyrolysis be screened to extract suitable metal oxides for use as catalyst supports, but also a catalyst with high chlorine resistance can be prepared by adopting appropriate mixing, impregnation, calcination and reduction processes;

[0033] (4) The present invention further optimizes the design of the value-added co-production link, thereby realizing the online modification of the chlorine-resistant catalyst. For example, the FeCl3 vapor generated by the coupled pyrolysis link has no inhibitory effect on the carbon nanotube growth process, but can further enhance the Fe loading of the active sites, thereby effectively improving the yield and quality of the carbon nanotubes.

[0034] (5) In addition, the present invention also optimizes the parameters in the coupled value-added co-production process of chlorine-containing plastics and red mud. By optimizing the mixing ratio of chlorine-containing plastics and red mud, the raw materials can be fully utilized, the product quality can be improved, and the comprehensive economic benefits of the system can be maximized; by optimizing the pyrolysis temperature and the diameter-to-height ratio of the coupled pyrolysis reactor, the quality of the carbon source obtained by the pyrolysis of plastics can be improved, thereby regulating the product yield and quality; by optimizing the outlet flow rate of the dechlorinated volatile matter and the hydrogen-rich gas flow rate at the catalyst nozzle, the catalyst can be fluidized, thereby enhancing heat and mass transfer. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a flow chart of the method for coupling chlorine-containing plastics with red mud for value-added co-production and chlorine fixation according to the present invention;

[0036] Figure 2 This is a system diagram of a device for coupling chlorine-containing plastics with red mud for value-added co-production and chlorine fixation according to a preferred embodiment of the present invention;

[0037] Figure 3 is a schematic diagram for more specifically showing the structure of the coupled pyrolysis reactor;

[0038] Figure 4 It is a schematic diagram for showing the structure of the calcining chamber and the reduction chamber in more detail;

[0039] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0040] 1-mixed raw material feed inlet, 2-feeding auger, 3-pyrolysis furnace, 4-volatile matter pressure cabin, 5-directional guide, 6-baffle, 7-solid product outlet, 8-pressure regulating valve, 9-volatile matter nozzle, 10-catalyst nozzle, 11-fluidized bed, 12-mixed gas channel, 13-gas-solid separator, 14-carbon nanotube storage bin, 15-condensable gas channel, 16-circulating hydrogen-rich gas inlet, 17-solenoid valve, 18-chlorine-resistant catalyst inlet, 19-mixture inlet, 20-calcination chamber, 21-air inlet, 22-air outlet, 23-sealed transfer channel, 24-hydrogen-rich gas inlet, 25-reduction chamber, 26-partition, 27-catalyst outlet. DETAILED DESCRIPTION

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0042] Figure 1 The flow chart of the method for coupling chlorine-containing plastics with red mud to produce added value and fix chlorine is shown below. Figure 1 Provide specific explanations.

[0043] First, there is a coupled pyrolysis step.

[0044] In this step, the chlorine-containing plastic is co-pyrolyzed with red mud, wherein the metal oxides in the red mud catalyze the reaction while also reacting with the chloride released by the pyrolysis of the chlorine-containing plastic. After the reaction is complete, a solid residue and dechlorinated volatiles are obtained.

[0045] More specifically, chlorine-containing plastics are pretreated and mixed with red mud, then heated to a high temperature. The chlorine-containing plastics then pyrolyze under high temperatures, producing hydrocarbon-rich gases and large amounts of hydrogen chloride. As the gases from the chlorine-containing plastics come into contact with the red mud, the red mud's primary dechlorination components, such as Fe₂O₃, react with the generated hydrogen chloride at high temperatures, fixing the chlorine in the hydrogen chloride into a controllable component, FeCl₃ vapor. The resulting mixed volatiles are then fed into the subsequent value-added co-production process, while the remaining solid products from the red mud and hydrogen chloride reaction are fed into the synthesis of a chlorine-resistant catalyst.

[0046] Next, there is the step of synthesizing the chlorine-resistant catalyst.

[0047] In this step, the solid residue obtained above is used as a catalyst carrier, and is washed through a spray tower to remove soluble chloride salts. It is then mixed with an iron salt solution and calcined to form a eutectic catalyst, which is then reduced in a hydrogen-rich atmosphere to synthesize a chlorine-resistant catalyst.

[0048] More specifically, considering the relatively complex composition of red mud, the solid residue after the complete reaction of the red mud in the previous steps contains a large amount of components, of which only about 50% are good catalyst supports. The soluble chloride salts are separated by water washing, the solid residue is collected, and a quantitative iron salt solution is added. The solid residue and the iron salt solution are evenly mixed by mechanical stirring. The resulting mixture slurry is calcined in an air atmosphere to uniformly load the iron atoms on the catalyst support. Finally, the calcined catalyst is reduced with rich hydrogen to convert the iron oxide crystals into iron spinel, thereby enhancing its chlorine resistance and obtaining a chlorine-resistant catalyst, leading to the value-added co-production link.

[0049] Finally, there is the value-added co-production step.

[0050] In this step, the dechlorinated volatiles and chlorine-resistant catalyst obtained above are sent to a fluidized bed reactor for full reaction and gas-solid separation, thereby achieving the co-production of the final product comprising carbon nanotubes, hydrogen-rich gas, pyrolysis oil and ferric chloride.

[0051] More specifically, the dechlorinated volatiles and the chlorine-resistant catalyst are sent together to a fluidized bed reactor, where carbon nanotubes are deposited on the surface of the chlorine-resistant catalyst by chemical vapor deposition. The fluidized carbon nanotube and catalyst mixture is passed through a separator under the action of a mixed gas to collect solid residual particles. The remaining mixed gas still contains non-condensable gas and condensable gas, and these mixed gases are all introduced into the subsequent links of value-added co-production.

[0052] According to a preferred embodiment of the present invention, the residual mixed gas obtained above can be passed into a stepped cooling device. Since the liquefaction temperatures of the condensable gases in the mixed gas are significantly different, they can be separated by temperature stepped cooling, thereby ultimately achieving stepped separation of pyrolysis heavy oil, ferric chloride, and pyrolysis light oil. After cooling, the main remaining component of the mixed gas is high-purity hydrogen, which is passed into the subsequent links of value-added co-production.

[0053] According to another preferred embodiment of the present invention, the hydrogen-rich gas obtained above can be introduced into the reduction link in the synthesis of the chlorine-resistant catalyst as a reducing atmosphere through the cooperation of subsequent devices, and then introduced into the fluidized bed as a reducing atmosphere to optimize the environment for the deposition and growth of carbon nanotubes, ultimately forming a complete cycle.

[0054] In addition, according to another preferred embodiment of the present invention, when the PVC content in the chlorine-containing plastic is greater than 15%, the mass ratio between the red mud and the chlorine-containing plastic is preferably 5:3 to 2:1, and the mass proportion of Fe2O3 as the main solid chlorine component in the red mud is not less than 60%.

[0055] The FeCl3 vapor produced by the dechlorination of the volatile matter can strengthen the active metal sites of the chlorine-resistant catalyst, thereby further improving the yield and quality of carbon nanotubes. The temperature of the fluidized bed reactor is preferably set to 750℃~850℃, and its fluidizing wind speed is preferably set to 1.2m / s~1.5m / s

[0056] Figure 2 This is a system diagram of a device for coupling chlorine-containing plastics with red mud for value-added co-production and chlorine fixation according to a preferred embodiment of the present invention.

[0057] like Figure 2 As shown, the device includes a pyrolysis unit, a chlorine-resistant catalyst synthesis unit and a value-added co-production unit connected in sequence, wherein:

[0058] The pyrolysis unit comprises a coupled pyrolysis reactor, which includes a mixed raw material feed inlet, a feeding auger, a pyrolysis furnace, a directional guide, a baffle, a solid product outlet, a volatile matter pressure chamber, and a pressure-stabilizing valve connected in sequence, wherein the mixed raw material feed inlet is used to feed a mixed raw material of red mud and chlorine-containing plastic; the feeding auger is used to move the mixed raw material upward in the pyrolysis furnace until the reaction is complete; the directional guide and the baffle are used to feed the pyrolysis reaction product into the solid product outlet; the volatile matter pressure chamber and the pressure-stabilizing valve enable the dechlorinated volatile matter to be supplied to the fluidized bed reactor at a certain pressure;

[0059] The chlorine-resistant catalyst synthesis unit includes a mixture inlet, a calcination chamber, a sealed transfer channel, a reduction chamber, a partition, and a catalyst outlet, which are connected in sequence. The mixture inlet is used to send the solid residue into the calcination chamber and calcine it under an air atmosphere; the sealed transfer channel is used to draw the calcined product into the reduction chamber and convert the iron oxide crystals into iron spinel under a reducing atmosphere; the partition is used to prolong the residence time of the eutectic catalyst in the reduction chamber so that it is sent to the catalyst outlet after being fully reduced;

[0060] The value-added co-production unit is used to fully react the dechlorinated volatiles with the chlorine-resistant catalyst, and then perform gas-solid separation, thereby achieving value-added co-production of final products including carbon nanotubes, hydrogen-rich gas, pyrolysis oil and ferric chloride.

[0061] More specifically, if Figure 3As shown, the coupled pyrolysis reactor of the coupled pyrolysis unit comprises a mixed raw material feed inlet 1 connected to a feeding auger 2; a pyrolysis furnace 3, a directional guide 5, a volatile matter pressure chamber 4, a baffle 6, a solid product outlet 7, and a pressure regulating valve 8 at the connection with the fluidized bed reactor. The mixed raw material feed inlet 1 feeds a mixture of red mud and chlorine-containing plastic into the feeding auger 2. The pyrolysis furnace 3 is arranged concentrically with the feeding auger 2 to move the mixed raw material upward in the pyrolysis furnace 3 until the reaction is complete. The directional guide 5 is located at the outlet of the pyrolysis furnace 3 and, together with the baffle 6 outside the pyrolysis furnace 3, feeds the solid red mud reaction product into the solid product outlet 7. The solid product outlet 7 is connected to the spray tower inlet of the chlorine-resistant catalyst synthesis unit. The volatile matter pressure chamber 4 and the pressure regulating valve 8 form a sandwich structure with the pyrolysis furnace 3, which together create a high-pressure environment within the sandwich structure, allowing the generated volatile matter to be supplied to the fluidized bed reactor at a certain pressure.

[0062] During operation, red mud and chlorine-containing plastics in a mixing ratio of 5:3 enter the pyrolysis furnace 3 through the mixed raw material feed port 1. The height-to-diameter ratio of the coupled pyrolysis reactor is set to 3:1, and are transported upward via the feeding auger 2. The temperature in the pyrolysis furnace 3 is set to 800°C. At this time, the hydrogen chloride produced by the pyrolysis of the chlorine-containing plastic can fully react with the red mud. The produced pyrolysis volatile phase is pressurized by the volatile pressure chamber 4 and then passed into the fluidized bed reactor of the value-added co-production unit through the pressure-stabilizing valve 8; the solid residue after the red mud is completely reacted is sent out of the pyrolysis furnace 3 by the feeding auger 2 through the directional guide port 5, then slides into the baffle 6, and is sent to the solid product outlet 7, and finally leads to the chlorine-resistant catalyst synthesis unit.

[0063] like Figure 3 As shown, the fluidized bed reactor and gas-solid separator of the value-added co-production unit include a volatile matter nozzle 9 at the bottom, a catalyst nozzle 10, a main fluidized bed 11, a mixed gas channel 12 connected to the upper part, a gas-solid separator 13, a carbon nanotube storage bin 14, a condensable gas channel 15; a chlorine-resistant catalyst inlet 18 connected to the catalyst nozzle, a circulating hydrogen-rich gas inlet 16 and a solenoid valve 17. The volatile matter nozzle 9 is connected to the pressure-stabilizing valve 8 of the coupled pyrolysis unit, which mainly provides fluidizing air with a certain flow rate; the circulating hydrogen-rich gas inlet 16 and the solenoid valve 17 at its inlet provide high-flow circulating hydrogen-rich gas at a certain pressure, and the catalyst powder brought into the channel by the chlorine-resistant catalyst inlet 18 connected to the gas-powder channel is blown into the fluidized bed 11 through the catalyst nozzle 10; the lower part of the fluidized bed 11 is connected to the volatile matter nozzle 9, and the catalyst nozzles 10 are distributed on both sides. The fluidizing air provided by the two together form a strong heat and mass transfer flow field; the upper part of the fluidized bed 11 is connected to the mixed gas channel 12. The gas-solid mixture after the reaction in the fluidized bed 11 enters the gas-solid separator 13 through the mixed gas channel 12, and the solid product falls into the carbon nanotube storage bin 14. The remaining mixed gas passes through the condensable gas channel 15 and leads to the cascade condensation tower.

[0064] During operation, the pyrolysis volatiles provided by the coupled pyrolysis unit enter the fluidized bed 11 through the volatile nozzle 9 at a certain flow rate of 1.2-1.5m / s. The high-flow-rate hydrogen-rich gas at the circulating hydrogen-rich gas inlet 16 mixes the chlorine-resistant catalyst powder provided by the chlorine-resistant catalyst inlet 18 and blows it to the catalyst nozzle 10 through the solenoid valve 17, and then sprays it into the fluidized bed 11. The temperature of the fluidized bed 11 is set to 800°C. The catalyst is fluidized under the action of the pyrolysis volatiles and the high-flow-rate hydrogen-rich gas to form a mixture of carbon nanotubes and catalyst particles. The mixed gas and the particle mixture enter the gas-solid separator 13 along the mixed gas channel 12, and the carbon nanotubes enter the carbon nanotube storage bin 14 after screening. After screening, the mixed gas passes through the condensable condensation channel 15 to the stepped condensation tower. The cascade condensation tower separates condensable gases from the mixed gas through three temperature steps, separating heavy pyrolysis oil at 316°C to 380°C, liquid FeCl3 at 306°C to 316°C, and light pyrolysis oil at temperatures above 306°C to room temperature. Non-condensable gases are fed into a surge tank and a hydrogen-rich gas storage tank. Solenoid valves coordinate to provide high-flow hydrogen-rich gas as transport gas to the fluidized bed reactor and low-flow hydrogen-rich gas as reducing gas to the reduction chamber.

[0065] like Figure 4 As shown, the calcination chamber and reduction chamber of the chlorine-resistant catalyst synthesis unit include a mixture inlet 19, a calcination chamber 20, an air inlet 21, an air outlet 22, a sealed transfer channel 23, a hydrogen-rich gas inlet 24, a reduction chamber 25, a partition 26, and a catalyst outlet 27, which are connected in sequence. The calcination chamber 20 and the reduction chamber 25 are arranged in an upper and lower position and connected by the sealed transfer channel 23. The calcination chamber 20 is connected to the air inlet 21 and the air outlet 22 to provide an air atmosphere. The reduction chamber 25 is connected to the hydrogen-rich gas inlet 24 to provide a reducing atmosphere. At the same time, partitions 26 are staggered inside the reduction chamber 25 to extend the residence time of the eutectic catalyst and form a higher quality chlorine-resistant catalyst.

[0066] During operation, the solid residue provided by the coupled pyrolysis unit is passed into the spray tower to screen the soluble chloride salts and metal oxides. The metal oxides are then transported to the mixing chamber and stirred and mixed with the ferric nitrate solution as catalyst carriers to keep the mass fraction of Fe in the impregnation mixture at 10%-20%. The impregnation mixture is passed into the calcination chamber 20 and calcined at 800°C for 3 hours. It is then sent to the reduction chamber through the sealed transfer channel 23 and reduced to a chlorine-resistant catalyst under the reducing atmosphere provided by the circulating hydrogen-rich gas. The catalyst is then sent to the chlorine-resistant catalyst inlet 18 to realize the recycling of the solid residue of the red mud reaction.

[0067] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for coupling chlorine-containing plastics with red mud to produce added value and fix chlorine, characterized in that: The method comprises the following steps: (i) Coupled pyrolysis step In this step, the chlorine-containing plastic is co-pyrolyzed with red mud, wherein the metal oxides in the red mud catalyze the reaction while also reacting with the chlorides released by the pyrolysis of the chlorine-containing plastic, and after the reaction is complete, a solid residue and dechlorinated volatiles are obtained; (ii) Synthesis steps of chlorine-resistant catalysts In this step, the solid residue obtained in step (i) is used as a catalyst carrier, which is washed away from soluble chloride salts through a spray tower, and then mixed with an iron salt solution and calcined to form a eutectic catalyst, which is then reduced in a hydrogen-rich atmosphere to synthesize a chlorine-resistant catalyst; (iii) Value-added co-production steps In this step, the dechlorinated volatiles obtained in step (i) and the chlorine-resistant catalyst synthesized in step (ii) are sent to a fluidized bed reactor for full reaction and gas-solid separation, thereby achieving the co-production of the final product comprising carbon nanotubes, hydrogen-rich gas, pyrolysis oil and ferric chloride.

2. The method according to claim 1, wherein In step (i), the components of the red mud include Fe2O3, Al2O3, SiO2, Na2O, CaO, and TiO2, and Fe2O3, Na2O, and CaO are used as main chlorine-fixing components.

3. The method according to claim 2, wherein In step (i), when the PVC content in the chlorine-containing plastic is greater than 15%, the mass ratio of the red mud to the chlorine-containing plastic is 5:3 to 2:1, and the mass proportion of Fe2O3 as the main solid chlorine component in the red mud is not less than 60%.

4. The method according to any one of claims 1 to 3, wherein: In step (ii), the synthesis process of the chlorine-resistant catalyst is designed as follows: S1: The solid residue is transported to a spray tower through a solid collection channel to wash the soluble chloride salts. The remaining metal oxides Al2O3, SiO2, and TiO2 serve as catalyst supports. S2: The catalyst carrier is placed into a mixing chamber, and the prepared iron salt solution is added and stirred; S3: After being thoroughly stirred and mixed, the impregnation mixture is sent to the catalyst calcination chamber and calcined in an air atmosphere to form a eutectic catalyst. At this time, a small amount of coke contained in the impregnation mixture provides part of the heat for the calcination process; S4: The eutectic catalyst is then fed into a reduction chamber, and the iron oxide forms iron spinel with the catalyst support during the reduction process, thereby completing the synthesis of the chlorine-resistant catalyst while also achieving efficient utilization of the solid residue.

5. The method according to claim 4, wherein In sub-step S3, the Fe mass fraction in the impregnation mixture is 10% to 20%; in sub-step S3, the calcination temperature of the impregnation mixture is 800° C. to 850° C., and the calcination time is 3 hours.

6. The method according to claim 5, wherein In step (iii), the dechlorinated volatiles and the chlorine-resistant catalyst are jointly fed to a fluidized bed reactor and placed in a carbon nanotube growth section, thereby enhancing the heat and mass transfer process of the gas-solid reaction by setting the fluidizing air velocity of the fluidized bed. In addition, the FeCl3 vapor generated by the dechlorinated volatiles is used to strengthen the active metal sites of the chlorine-resistant catalyst, thereby further improving the yield and quality of the carbon nanotubes.

7. The method according to claim 6, wherein In step (iii), the temperature of the fluidized bed reactor is set to 750° C. to 850° C., and the fluidizing air velocity thereof is set to 1.2 m / s to 1.5 m / s.

8. The method according to claim 7, wherein In step (iii), the condensable mixed gas obtained by the gas-solid separation is introduced into a stepped condensation tower and subjected to stepped cooling with a certain temperature gradient.

9. The method according to claim 8, wherein In step (iii), when Fe2O3 is used as the main solid chlorine component, a three-level temperature gradient is used to separate the liquid phase product, wherein the three-level temperature gradient is: heavy pyrolysis oil is separated at 316°C to 380°C, liquid FeCl3 is separated at 306°C to 316°C, and light pyrolysis oil is separated at below 306°C to room temperature.

10. A device for executing the method according to any one of claims 1 to 9, characterized in that: The device comprises a pyrolysis unit, a chlorine-resistant catalyst synthesis unit and a value-added co-production unit connected in sequence, wherein: The pyrolysis unit comprises a coupled pyrolysis reactor, which includes a mixed raw material feed inlet, a feeding auger, a pyrolysis furnace, a directional guide, a baffle, a solid product outlet, a volatile matter pressure chamber, and a pressure-stabilizing valve connected in sequence, wherein the mixed raw material feed inlet is used to feed a mixed raw material of red mud and chlorine-containing plastic; the feeding auger is used to move the mixed raw material upward in the pyrolysis furnace until the reaction is complete; the directional guide and the baffle are used to feed the pyrolysis reaction product into the solid product outlet; the volatile matter pressure chamber and the pressure-stabilizing valve enable the dechlorinated volatile matter to be supplied to the fluidized bed reactor at a certain pressure; The chlorine-resistant catalyst synthesis unit includes a mixture inlet, a calcination chamber, a sealed transfer channel, a reduction chamber, a partition, and a catalyst outlet, which are connected in sequence. The mixture inlet is used to send the solid residue into the calcination chamber and calcine it under an air atmosphere; the sealed transfer channel is used to draw the calcined product into the reduction chamber and convert part of the iron oxide crystals into iron spinels under a reducing atmosphere; the partition is used to prolong the residence time of the eutectic catalyst in the reduction chamber so that it is sent to the catalyst outlet after being fully reduced; The value-added co-production unit is used to fully react the dechlorinated volatiles with the chlorine-resistant catalyst, and then perform gas-solid separation, thereby achieving value-added co-production of final products including carbon nanotubes, hydrogen-rich gas, pyrolysis oil and ferric chloride.

Images