A method and system for processing chlorinated waste plastics in a multi-phase hydrocracking unit

Abstract

The application discloses a method and system for processing chloroplast waste plastics by a multiphase flow hydrocracking device, S1: chloroplast waste plastics, a dechlorination agent, a solid catalyst and heavy oil are prepared in a raw material tank to form a uniform mixed slurry; S2: the mixed slurry is pumped to a multiphase flow hydrocracking reactor by a high-pressure feeding pump, under high-temperature hydrogen conditions, chlorine elements in the plastics react with the dechlorination agent to generate chlorinated salt, which is adsorbed on the surface of the catalyst and enters a hot high-pressure separator together with reaction products; S3: the reaction products are separated by the hot high-pressure separator to obtain light distillate oil and solid-containing heavy distillate oil; S4: the solid-containing heavy distillate oil is subjected to a vacuum tower and a hot solvent extraction device to respectively obtain vacuum gas oil, vacuum residue and solid waste catalyst, and the vacuum residue can be returned to the raw material tank for use as raw material. The application realizes deep removal of chlorine in chloroplast waste plastics, and through the synergistic conversion of various substances, the reaction severity is reduced, the resource utilization efficiency is improved, and high-value-added products are obtained.

Description

Technical Field

[0001] This invention relates to the field of waste plastic resource recycling technology, specifically to a method and system for processing chlorine-containing waste plastics using a multiphase flow hydrocracking unit. Background Technology

[0002] The high-value utilization of waste plastics is one of the effective ways to reduce environmental pollution and improve resource utilization efficiency. Chemically recycled fuel is regarded as an "upgraded" method of waste plastic utilization that can achieve closed-loop recycling, mainly through technologies such as thermal cracking, thermal pyrolysis, catalytic cracking, and catalytic pyrolysis to convert waste plastics.

[0003] In the prior art, CN10461030B discloses a coking method for producing fuel oil from waste plastics. This method involves preheating high-aromatic components and waste plastics or plastic oils in a raw material buffer tank before introducing them into a tubular heater for further heating, and then injecting them into a delayed coking tower for coking. The waste plastics mentioned in this patent are one or more of polyethylene, polypropylene, and polystyrene, but do not contain polyvinyl chloride (PVC), therefore it cannot process waste plastic raw materials mixed with PVC.

[0004] CN108410490B discloses a pyrolysis treatment process and system for chlorine-containing waste plastics. The process involves low-temperature pyrolysis of the chlorine-containing waste plastics, generating a mixed gas consisting of tar, hydrogen chloride, and combustible gas. This mixed gas, after tar removal via tar reforming, reacts with a dechlorinating agent to remove hydrogen chloride. While this patent converts chlorine-containing waste plastics into hydrogen chloride through low-temperature pyrolysis and then removes the hydrogen chloride from the mixed gas through tar reforming and a dechlorinating agent reaction, equipment corrosion is a concern throughout the entire process.

[0005] In summary, existing waste plastic pyrolysis technologies have several drawbacks when treating waste plastics with high chlorine content, including the inability to process chlorine-containing waste plastics, difficulty in removing chlorine contaminants, poor quality of liquid products, and severe equipment corrosion. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method and system for processing chlorine-containing waste plastics in a multiphase flow hydrocracking unit. This method can not only achieve deep removal of chlorine from chlorine-containing waste plastics, thus avoiding equipment corrosion and environmental pollution caused by the processing of chlorine-containing waste plastics from the source, but also reduce the severity of the reaction through the synergistic transformation of multiple substances, obtain higher quality liquid products, improve resource utilization efficiency, and obtain high value-added products.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for processing chlorinated waste plastics using a multiphase flow hydrocracking unit includes the following steps; S1: Chlorine-containing waste plastics, dechlorination agent, solid catalyst and heavy oil are mixed in raw material tank 5 to form a uniform slurry; S2: The mixed slurry is pumped to the multiphase flow hydrocracking reactor 10 by the high-pressure feed pump 7. Under high temperature and hydrogen conditions, the chlorine in the plastic reacts with the dechlorinating agent to generate chloride salt, which is adsorbed on the catalyst surface and enters the hot high-pressure separator 11 together with the reaction products. S3: The reaction products are separated by a hot high-pressure separator 11 to obtain light distillate oil and heavy distillate oil containing solids; S4: The heavy distillate oil containing solids is processed through a vacuum tower 16 and a hot melt extraction device 18 to obtain vacuum wax oil, vacuum residue oil and solid waste catalyst, respectively. The vacuum residue oil can be returned to the raw material tank for use as a raw material.

[0008] The chlorine-containing waste plastic mentioned in S1 is a mixed plastic containing PVC, and the mixed plastic is one or more of PP, PE, PS, and PET.

[0009] The chlorine-containing waste plastics mentioned in S1 are in granular form with a maximum particle size not exceeding 150μm. The addition amount is calculated based on the mass fraction of the total feed amount, ranging from 0% to 50%. The chlorine-containing waste plastics mentioned in S1 are calculated based on the total feed mass fraction, with PVC accounting for no more than 10%.

[0010] The dechlorinating agent described in S1 is in powder form and is one or more of sodium sulfide, sodium thiosulfate, sodium carbonate, sodium bicarbonate, calcium oxide, and calcium carbonate. The dechlorinating agent mentioned in S1 is calculated based on the total feed mass fraction, and the addition amount is 0-5%.

[0011] The solid catalyst active group described in S1 includes one or more of iron hydroxyl oxide, nickel oxide, cobalt oxide, tungsten oxide and molybdenum oxide. The support is a porous carbon-based material, such as activated carbon, pulverized coal and coke. The catalyst addition amount is calculated based on the total feed mass fraction and is 0.5-2.0%.

[0012] The solid catalyst, by weight calculation, comprises 15-49% iron hydroxyoxide, 1-20% nickel oxide, cobalt oxide, molybdenum oxide, or tungsten oxide (the active components can be loaded with multiple metal active components; the content range of each active component is given here), and has a bulk density of 0.6-0.8 g / cm³. 3 Average particle size 65-75μm, specific surface area 400-600m² 2 / g.

[0013] The heavy oil in S1 is one or more of atmospheric residue, vacuum residue, coal tar, catalytic slurry, steam cracking tar, or other secondary processed distillate oils, or is an oil-coal slurry containing coal powder.

[0014] The ratio of chlorinated waste plastics, dechlorination agent, solid catalyst and heavy oil in S1 is (0-50):(0-5):(0.5-2.0):(50-100).

[0015] The operating conditions of the multiphase flow hydrocracking reactor in S2 are as follows: reaction temperature 370-470℃, reaction pressure 4-15MPa, and liquid hourly space velocity 0.3-2.0h. -1 The hydrogen-to-oil ratio is 800-1500 NL / kg. Waste plastics, heavy oil, or coal powder, among other substances, react in a multiphase flow hydrocracking reactor. The operating conditions are set to ensure that both waste plastics and heavy oil can be converted.

[0016] The multiphase flow hydrocracking reactor in S2 consists of 1-3 reactors in series or parallel combination mode, and the reactor type is one or a combination of several of the following: suspension bed, fluidized bed, and bubbling bed.

[0017] The reaction products in S3 are separated by a hot high-pressure separator to obtain light distillate oil and heavy distillate oil containing solids, wherein the final boiling point of the light distillate oil is not higher than 450°C.

[0018] The solid-containing heavy distillate oil in S4 is subjected to vacuum distillation in a vacuum tower to obtain vacuum wax oil and solid-containing oil residue. The vacuum wax oil can be used as feedstock for catalytic cracking or hydrocracking. The distillate has a distillation range of 350-500℃.

[0019] The solid oil residue in S4 is separated by a thermal extraction device to obtain vacuum residue and solid waste catalyst. All or part of the vacuum residue is used as circulating oil, and the waste catalyst, which adsorbs chloride salts and coke, is treated as solid waste or recycled for secondary use.

[0020] The extraction solvent in the S4 thermal extraction device is one or more hydrocarbon mixtures selected from n-heptane, benzene, toluene, and xylene, or coal liquefaction light oil.

[0021] The process parameters controlled by the hot melt extraction device in S4 are: pressure 0.1-0.5MPa, extraction temperature 90-150℃, agent-to-oil ratio (1-20):1, and extraction time 0.5-2 hours.

[0022] A system for processing chlorinated waste plastics in a multiphase flow hydrocracking unit includes a feed tank 5. The input end of the feed tank 5 is connected to the input ends of pipelines for conveying chlorinated waste plastics 1, dechlorinating agent 2, solid catalyst 3 and heavy oil 4. The chlorinated waste plastics 1, dechlorinating agent 2, solid catalyst 3 and heavy oil 4 are mixed in the feed tank 5 to form a uniform slurry. The mixed slurry is fed into the mixer 8 through the high-pressure feed pump 7 and mixed with hydrogen 6. After being preheated by the heater 9, it enters the multiphase flow hydrocracking reactor 10. The output of the multiphase flow hydrocracking reactor 10 is connected to a hot high-pressure separator 11. The gaseous products of the hot high-pressure separator 11 enter the hot low-pressure separator 12, where gaseous hydrocarbons are separated and enter the circulating hydrogen compressor 13. Liquid light distillate oil 14 exits the unit. Solid heavy distillate oil is cooled and depressurized by a pressure reducing valve 15 and then enters a pressure reducing tower 16 and a hot melt extraction unit 18 to obtain vacuum wax oil 17, vacuum residue oil 19, and solid waste catalyst 20, respectively. Vacuum residue oil 19 is returned to the feed tank for use as feedstock, while solid waste catalyst exits the unit for solid waste treatment or secondary processing.

[0023] The beneficial effects of this invention are: 1. The method provided by the present invention can not only promote the reaction between elemental chlorine and dechlorinating agent through multiphase flow hydrocracking reaction to achieve the purpose of deep dechlorination, but also play a role in hydrogenation and upgrading of waste plastic liquid hydrocarbons to obtain high-value-added chemical raw materials or chemicals.

[0024] 2. The method provided by this invention makes full use of the metal active components loaded on the surface of the solid catalyst, which can not only promote the removal of elemental chlorine from waste plastics, but also adsorb particulate matter such as chloride salts, coking precursors, and impurity elements formed during the reaction process onto the catalyst surface and carry them out of the reaction system, effectively avoiding equipment corrosion and blockage problems.

[0025] 3. The method provided by this invention fully utilizes the synergistic and complementary effect between waste plastics and heavy oil to achieve the synergistic conversion of the two materials. This not only provides a new technical path for the high-value utilization of waste plastics and reduces environmental pollution from waste plastics, but also reduces the severity of the reaction and improves resource utilization efficiency. Attached image description: Figure 1 This is a schematic diagram of the process flow for processing chlorine-containing waste plastics using a multiphase flow hydrocracking device according to the present invention.

[0026] 1-Chlorine-containing waste plastics; 2-Dechlorination agent; 3-Solid catalyst; 4-Heavy oil; 5-Feed tank; 6-Hydrogen; 7-High-pressure feed pump; 8-Mixer; 9-Heating furnace; 10-Multiphase flow hydrocracking reactor; 11-Hot high-pressure separator; 12-Hot low-pressure separator; 13-Circulating hydrogen compressor; 14-Light distillate oil; 15-Pressure reducing valve; 16-Pressure reducing tower; 17-Pressure reducing wax oil; 18-Hot melt extraction device; 19-Pressure reducing residue oil; 20-Solid waste catalyst. Detailed Implementation

[0027] The present invention will be further described below with reference to embodiments: This invention discloses a method for multiphase flow hydrocracking to treat chlorine-containing waste plastics, such as... Figure 1As shown, chlorine-containing waste plastic 1, dechlorination agent 2, solid catalyst 3, and heavy oil 4 are mixed in a raw material tank 5 to form a homogeneous slurry. The slurry is then mixed with hydrogen 6 in a mixer 8 via a high-pressure feed pump 7. After preheating in a heater 9, it enters a multiphase flow hydrocracking reactor 10. Under the conditions of a reaction temperature of 380-450℃, a reaction pressure of 8-15MPa, and a hydrogen-to-oil ratio of 800-1200NL / kg (the reaction involves multiple substances such as waste plastic, heavy oil, or coal powder, and the operating conditions are set to ensure that both waste plastic and heavy oil can be converted), the chlorine in the plastic reacts with the dechlorination agent to generate chlorine. Salts are adsorbed onto the catalyst surface and enter the hot high-pressure separator 11 along with the reaction products. The reaction products are separated by the hot high-pressure separator 11 to obtain gaseous products and heavy distillate oil containing solids. The gaseous products enter the hot low-pressure separator 12, where gaseous hydrocarbons are separated and enter the circulating hydrogen compressor 13. Liquid light distillate oil 14 exits the unit. The heavy distillate oil containing solids is cooled and depressurized by the pressure reducing valve 15 and then enters the pressure reducing tower 16 and the hot melt extraction unit 18 to obtain vacuum wax oil 17, vacuum residue oil 19 and solid waste catalyst 20, respectively. Vacuum residue oil 19 can be returned to the feed tank for use as a raw material. Solid waste catalyst exits the unit for solid waste treatment or secondary processing.

[0028] The technical solutions and effects of the present invention will be further illustrated below with reference to the embodiments, but the invention is not limited to the following embodiments.

[0029] The properties of the raw material oil slurry are shown in Table 1, the physicochemical properties of the catalyst are shown in Table 2, and the multiphase flow hydrogenation reaction conditions and chlorine content of the liquid products are shown in Table 3.

[0030] Example 1 In this embodiment, PVC and preheated oil slurry were mixed uniformly at a mass ratio of 2:98. 2% dechlorination agent and 1% carbon-based catalyst were added to form a homogeneous slurry. The multiphase flow hydrocracking reaction conditions were: reaction temperature 430℃, reaction pressure 8MPa, and space velocity 0.5h⁻¹. -1 Hydrogen-to-oil ratio 1000 NL / kg.

[0031] Example 2 In this embodiment, PVC and preheated oil slurry were mixed uniformly at a mass ratio of 2:98. 2% dechlorination agent and 1% carbon-based catalyst were added to form a homogeneous slurry. The multiphase flow hydrocracking reaction conditions were: reaction temperature 430℃, reaction pressure 8MPa, and space velocity 0.5h⁻¹. -1 Hydrogen-to-oil ratio 1000 NL / kg.

[0032] Example 3 In this embodiment, PVC and preheated oil slurry are mixed uniformly at a mass ratio of 5:95. 4% dechlorination agent and 2% carbon-based catalyst are added to form a homogeneous slurry. The multiphase flow hydrocracking reaction conditions are: reaction temperature 450℃, reaction pressure 10MPa, and space velocity 0.5h. -1 Hydrogen-to-oil ratio 1000 NL / kg.

[0033] Example 4 In this embodiment, PVC and preheated oil slurry are mixed uniformly at a mass ratio of 5:95. 4% dechlorination agent and 2% carbon-based catalyst are added to form a homogeneous slurry. The multiphase flow hydrocracking reaction conditions are: reaction temperature 450℃, reaction pressure 12MPa, and space velocity 0.5h. -1 Hydrogen-to-oil ratio 1000 NL / kg.

[0034] Example 5 In this embodiment, PVC and preheated oil slurry are mixed uniformly at a mass ratio of 5:95. 4% dechlorination agent and 2% carbon-based catalyst are added to form a homogeneous slurry. The multiphase flow hydrocracking reaction conditions are: reaction temperature 450℃, reaction pressure 14MPa, and space velocity 0.5h⁻¹. -1 Hydrogen-to-oil ratio 1000 NL / kg.

[0035] Example 6 In this embodiment, PP, PE, PS, and PVC were selected to prepare a mixed waste plastic containing 20% ​​PVC. This mixture was then mixed with preheated oil slurry at a mass ratio of 30:70. 4% dechlorination agent and 2% carbon-based catalyst were added to form a homogeneous slurry. The multiphase flow hydrocracking reaction conditions were: reaction temperature 450℃, reaction pressure 12MPa, and space velocity 0.5h⁻¹. -1 Hydrogen-to-oil ratio 1200 NL / kg.

[0036] Comparative Example 7 In this embodiment, PP, PE, PS, and PVC were selected to prepare a mixed waste plastic containing 20% ​​PVC. This mixture was then mixed with a preheated oil slurry at a ratio of 30:70 until homogeneous. 2% carbon-based catalyst was added to form a homogeneous slurry. The multiphase flow hydrocracking reaction conditions were: reaction temperature 450℃, reaction pressure 12MPa, and space velocity 0.5h⁻¹. -1 Hydrogen-to-oil ratio 1200 NL / kg.

[0037] Table 1 Properties of Catalytic Slurry Feedstock Density (20℃), g / cm3 0.952 Elemental analysis, wt% C 88.68 H 9.57 S 0.36 N 0.41 Residual charcoal, wt% 13.69 Metallic elements, ppm Ni 5.9 Fe 21.6 V 6.0 Four components, wt% Saturated fraction 41.18 Aromatic components 51.0 gelatinous 4.31 Asphalt 3.51 Table 2 Physicochemical properties of carbon-based catalysts 0.65 450 11%Fe, 0.5%Ni 70 Table 3. Reaction conditions and chlorine content of products in multiphase flow hydrocracking.

[0038] As shown in Table 3, the comparative example, without the addition of a dechlorinating agent, exhibited a high chlorine content in the liquid oil, primarily affecting the quality of the light oil and limiting its utilization. In contrast, the method of this invention adds a certain amount of dechlorinating agent to chlorine-containing waste plastics. Through multiphase flow hydrocracking, it not only achieves complete conversion of the chlorine-containing waste plastics and deep removal of chlorine, transferring chlorine to the catalyst surface for removal and reducing chlorine corrosion of equipment, but also yields liquid oil products with lower chlorine content, providing favorable conditions for the secondary processing and utilization of the liquid oil.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for processing chlorine-containing waste plastics using a multiphase flow hydrocracking unit, characterized in that, Includes the following steps; S1: Chlorine-containing waste plastic (1), dechlorination agent (2), solid catalyst (3) and heavy oil are mixed in a raw material tank (5) to form a uniform slurry; S2: The mixed slurry is pumped to the multiphase flow hydrocracking reactor (10) by the high pressure feed pump (7). Under high temperature and hydrogen conditions, the chlorine element in the plastic reacts with the dechlorination agent to generate chloride salt, which is adsorbed on the catalyst surface and enters the hot high pressure separator (11) together with the reaction products. S3: The reaction products are separated by a hot high-pressure separator (11) to obtain light distillate oil and heavy distillate oil containing solids; S4: The heavy distillate oil containing solids is processed by a vacuum tower (16) and a hot melt extraction device (18) to obtain vacuum wax oil (17), vacuum residue oil (19) and solid waste catalyst (20), respectively. The vacuum residue oil (19) is returned to the raw material tank (5) for use as raw material. The chlorine-containing waste plastic (1) mentioned in S1 is in granular form with a maximum particle size not exceeding 150 μm. The addition amount is calculated based on the mass fraction of the total feed amount, ranging from 0 to 50%. The chlorine-containing waste plastics (1) are calculated based on the total feed mass fraction, with PVC accounting for no more than 10%; The dechlorination agent (2) is in powder form and is one or more of sodium sulfide, sodium thiosulfate, sodium carbonate, sodium bicarbonate, calcium oxide, and calcium carbonate. The amount of the dechlorinating agent (2) added is calculated based on the total feed mass fraction and is 0-5%. The active components of the solid catalyst (3) include one or more of iron hydroxyl oxide, nickel oxide, cobalt oxide, tungsten oxide and molybdenum oxide. The support is a porous carbon-based material, which may be activated carbon, pulverized coal or coke. The catalyst addition amount is calculated based on the total feed mass fraction and is 0.5-2.0%. The solid catalyst (3) comprises, by weight, 15-49% iron hydroxyl oxide, 1-20% nickel oxide, cobalt oxide, molybdenum oxide, or tungsten oxide, and has a bulk density of 0.6-0.8 g / cm³. 3 Average particle size 65-75μm, specific surface area 400-600m² 2 / g; The heavy oil (4) is one or more of atmospheric residue, vacuum residue, coal tar, catalytic slurry, steam cracking tar or other secondary processed distillate oils, or is an oil-coal slurry containing coal powder.

2. The method for processing chlorine-containing waste plastics in a multiphase flow hydrocracking unit according to claim 1, characterized in that, The chlorine-containing waste plastic (1) in S1 is a mixed plastic containing PVC, and the mixed plastic is one or more of PP, PE, PS and PET.

3. The method for processing chlorine-containing waste plastics in a multiphase flow hydrocracking unit according to claim 1, characterized in that, The ratio of chlorine-containing waste plastic (1), dechlorination agent (2), solid catalyst (3) and heavy oil (4) in S1 is (0-50):(0-5):(0.5-2.0):(50-100).

4. The method for processing chlorinated waste plastics in a multiphase flow hydrocracking unit according to claim 1, characterized in that, The operating conditions of the multiphase flow hydrocracking reactor (10) in S2 are as follows: reaction temperature 370-470℃, reaction pressure 4-15MPa, and liquid hourly space velocity 0.3-2.0h. -1 Hydrogen-to-oil ratio 800-1500 NL / kg; The multiphase flow hydrocracking reactor (10) consists of 1-3 reactors in series or parallel combination mode, and the reactor type is one or a combination of several of the following: suspension bed, fluidized bed, and bubbling bed.

5. The method for processing chlorine-containing waste plastics in a multiphase flow hydrocracking unit according to claim 1, characterized in that, The reaction products in S3 are separated by a hot high-pressure separator (11) to obtain light distillate oil and heavy distillate oil containing solids, wherein the final boiling point of the light distillate oil is not higher than 450℃.

6. The method for processing chlorine-containing waste plastics in a multiphase flow hydrocracking unit according to claim 1, characterized in that, The solid heavy distillate oil in S4 is subjected to vacuum distillation in a vacuum tower (16) to obtain vacuum wax oil and solid oil residue, wherein the vacuum wax oil is used as feedstock for catalytic cracking or hydrocracking. The solid oil residue is separated by a hot melt extraction device (18) to obtain vacuum residue and solid waste catalyst. All or part of the vacuum residue is used as circulating oil, and the waste catalyst is adsorbed with chloride salts and coke and is treated as solid waste or recycled for secondary use. The extraction solvent of the hot melt extraction device (18) is one or more hydrocarbon mixtures of n-heptane, benzene, toluene, and xylene, or coal liquefaction light oil.

7. A method for processing chlorinated waste plastics in a multiphase flow hydrocracking unit according to claim 6, characterized in that, The hot melt extraction device (18) controls the process parameters as follows: pressure 0.1-0.5MPa, extraction temperature 90-150℃, agent-to-oil ratio (1-20):1, and extraction time 0.5-2 hours.

8. A system for processing chlorinated waste plastics in a multiphase flow hydrocracking unit for implementing the method according to any one of claims 1-7, characterized in that, Includes a raw material tank (5), the input end of which is connected to the input end of the conveying pipelines for chlorine-containing waste plastic (1), dechlorinating agent (2), solid catalyst (3) and heavy oil (4), respectively. The chlorine-containing waste plastic (1), dechlorinating agent (2), solid catalyst (3) and heavy oil (4) are mixed in the raw material tank (5) to form a uniform slurry. The mixed slurry is fed into the mixer (8) through a high-pressure feed pump (7) and mixed with hydrogen (6). After being preheated by a heating furnace (9), it enters the multiphase flow hydrocracking reactor (10). The output end of the multiphase flow hydrocracking reactor (10) is connected to a hot high-pressure separator (11). The gaseous products of the hot high-pressure separator (11) enter the hot low-pressure separator (12), and the separated gaseous hydrocarbons enter the circulating hydrogen compressor (13). The liquid light distillate oil (14) exits the device, and the solid heavy distillate oil is cooled and depressurized by the pressure reducing valve (15) and enters the pressure reducing tower (16) and the hot melt extraction device (18) to obtain vacuum wax oil (17), vacuum residue oil (19) and solid waste catalyst (20) respectively. The vacuum residue oil (19) is returned to the feed tank as a raw material, and the solid waste catalyst exits the device for solid waste treatment or secondary processing.

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