A method and system for dechlorinating pyrolysis oil from chlorinated plastics

Abstract

This disclosure relates to a method and system for dechlorinating pyrolysis oil containing chlorinated plastics, comprising the following steps: S1, heating and vaporizing the pyrolysis oil containing chlorinated plastics in a heating unit to obtain a chlorinated gas phase; S2, introducing the chlorinated gas phase into a dechlorination reaction unit to contact with a dechlorinating agent for a dechlorination reaction to obtain a dechlorinated gas phase; S3, introducing the dechlorinated gas phase into a separation unit for gas-liquid separation to obtain a dechlorinated plastic oil liquid phase. This disclosure offers excellent dechlorination performance and a simple process, suitable for the dechlorination treatment of pyrolysis oil containing chlorinated plastics, and can effectively solve the problems of equipment corrosion and environmental pollution caused by pyrolysis oil containing chlorinated plastics during subsequent processing and utilization.

Description

Technical Field

[0001] This disclosure relates to the fields of waste plastic resource utilization and green environmental protection technology, specifically, to a method and system for dechlorinating pyrolysis oil from chlorinated plastics. Background Technology

[0002] Plastics are widely used in households and industries, and are considered an indispensable part of our modern lives. However, traditional methods of plastic waste disposal, such as incineration, mechanical recycling, and waste-to-fuel conversion, are often limited or insufficient from the perspective of energy efficiency and resource utilization. Thermochemical conversion has become a realistic alternative to traditional plastic waste treatment, with the pyrolysis recycling of waste plastics becoming a viable path to a circular plastics economy. Pyrolysis oil can be cracked and further refined for use in the production of new plastics. Due to the widespread use of polyvinyl chloride (PVC) plastics, PVC plastics inevitably mix into the raw materials used in waste plastic pyrolysis processes. When these PVC-containing plastics are thermally degraded, the resulting pyrolysis oil has a high chlorine content, mostly in the form of organochlorides. The chlorine content in the pyrolysis oil far exceeds the standard of no more than 10 μg / g for chloride content in oil products, significantly affecting the quality of the oil.

[0003] Existing dechlorination technologies for plastic pyrolysis oil mainly include adsorption dechlorination, catalytic hydrodechlorination, electrochemical dechlorination, and biological dechlorination. Among these, research on electrochemical and biological dechlorination is limited, immature, and has a narrow application range. Currently, adsorption dechlorination agents are more commonly used, employing both physical and chemical adsorption principles. However, adsorption dechlorination agents generally have low chlorine capacity, making them only suitable for removing feedstock oils with low chlorine content. Waste plastic pyrolysis oil, on the other hand, contains chlorine levels as high as several thousand μg / g and many heteroatoms that can competitively adsorb. Direct adsorption can easily lead to rapid saturation of the adsorption dechlorination agent, reducing its dechlorination efficiency. Catalytic hydrodechlorination can treat feedstock oils with high chlorine content, but hydrotreating alone may not reduce the chlorine content to meet the control requirements for chlorine content in oil products. Much research focuses on chlorinated model compounds rather than actual oils, and research on catalysts for hydrodechlorination is limited. Existing hydrotreating catalysts are prone to deactivation, thus affecting the overall dechlorination effect. Summary of the Invention

[0004] The purpose of this disclosure is to provide a method and system for dechlorinating pyrolysis oil containing chlorinated plastics. The dechlorination effect is excellent and the process is simple. It is suitable for the dechlorination treatment of pyrolysis oil containing chlorinated plastics and can effectively solve the problems of corrosion damage to equipment and environmental pollution caused by pyrolysis oil containing chlorinated plastics in subsequent processing and utilization.

[0005] To achieve the above objectives, the first aspect of this disclosure provides a method for dechlorinating pyrolysis oil from chlorinated plastics, comprising the following steps:

[0006] S1. The chlorine-containing plastic pyrolysis oil is heated and vaporized in a heating unit to obtain a chlorine-containing gas phase;

[0007] S2. The chlorine-containing gas phase is introduced into the dechlorination reaction unit to contact the dechlorination agent and carry out the dechlorination reaction to obtain a dechlorinated gas phase;

[0008] S3. The dechlorinated gas phase is introduced into the separation unit for gas-liquid separation to obtain the dechlorinated plastic oil phase.

[0009] Optionally, the chlorinated plastic pyrolysis oil is derived from non-catalytic pyrolysis reaction of chlorinated plastic raw materials, catalytic pyrolysis reaction of chlorinated plastic raw materials, fluidized bed pyrolysis of chlorinated plastic raw materials, rotary kiln pyrolysis of chlorinated plastic raw materials, oil-plastic co-processing of chlorinated plastic raw materials, and screw extrusion pyrolysis of chlorinated plastic raw materials.

[0010] Optionally, the chlorinated plastic raw material includes polyvinyl chloride; the chlorinated plastic raw material also includes one or more selected from low-density polyethylene, high-density polyethylene, polypropylene and polystyrene;

[0011] Preferably, the chlorine content in the chlorine-containing plastic pyrolysis oil is 10–4000 μg / g, more preferably 10–2500 μg / g; optionally, the chlorine-containing plastic pyrolysis oil further includes 20–500 μg / g of silicon.

[0012] Optionally, the initial boiling point of the chlorine-containing plastic pyrolysis oil is any value between 10 and 100°C, and the final boiling point is any value between 400 and 500°C.

[0013] Optionally, the chlorine-containing plastic pyrolysis oil is prepared by a method comprising the following steps:

[0014] The chlorine-containing waste plastic raw material is fed into a pyrolysis reactor and pyrolyzed at 460-500℃ for 1-3 hours. Preferably, the heating rate of the chlorine-containing waste plastic raw material in the pyrolysis reactor is 5-10℃ / min. During the reaction, nitrogen gas may be continuously purged or not.

[0015] The obtained pyrolysis products were separated to obtain chlorine-containing plastic pyrolysis oil, coke and pyrolysis gas;

[0016] Optionally, the chlorine-containing waste plastic raw material includes 1 to 6% by weight of polyvinyl chloride.

[0017] Optionally, in step S1, the heating and vaporization conditions include: a temperature of 100–600°C, a pressure of 0.1–1.5 MPa, and a time of 0.1–2 h; preferably, a temperature of 300–520°C, a pressure of 0.1–1 MPa, and a time of 0.3–1 h; optionally, the heating rate is 5–30°C / min, preferably 10–25°C / min.

[0018] Preferably, the outlet temperature of the chlorine-containing gas phase at the outlet of the heating unit is 200–550°C, more preferably 300–500°C, and the outlet pressure is 0.1–1.5 MPa, more preferably 0.1–1 MPa;

[0019] Preferably, the chlorine content in the chlorine-containing gas phase is 10–4000 μg / g, more preferably 10–2500 μg / g;

[0020] Preferably, the liquid phase content carried by the chlorine-containing gas phase drawn out from the outlet of the heating unit is less than 10% by weight, and more preferably less than 5% by weight.

[0021] Optionally, in step S2, the conditions for the dechlorination reaction include: a weight hourly space velocity (WHSV) of 5–100 h⁻¹ for the chlorine-containing gas phase. -1 Preferably 10-50h -1 The reaction temperature is 200–500℃, preferably 300–450℃; the pressure is 0.1–1 MPa, preferably 0.1–0.5 MPa.

[0022] Preferably, the inlet temperature of the chlorine-containing gas phase in the dechlorination reaction unit is 250–480°C, more preferably 300–450°C, and the inlet pressure is 0.1–1 MPa, more preferably 0.1–0.5 MPa.

[0023] Preferably, the chlorine content in the obtained dechlorinated plastic oil phase is less than 50 μg / g, and more preferably less than 10 μg / g.

[0024] Optionally, in step S2, the dechlorinating agent is selected from one or more of metal oxides, metal hydroxides, and carbonates; preferably, the metal oxide is selected from one or more of calcium oxide, aluminum oxide, iron oxide, magnesium oxide, zinc oxide, nickel oxide, and copper oxide; the metal hydroxide is selected from one or more of calcium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, iron hydroxide, and aluminum hydroxide; and the carbonate is selected from one or more of calcium carbonate, sodium carbonate, potassium carbonate, magnesium carbonate, zinc carbonate, barium carbonate, magnesium carbonate, copper carbonate, and ammonium carbonate.

[0025] Preferably, the dechlorinating agent is selected from one or more of calcium oxide, zinc oxide, calcium carbonate, sodium carbonate, magnesium carbonate, calcium hydroxide, and magnesium hydroxide.

[0026] Optionally, the conditions for gas-liquid separation in step S3 include: a gas-liquid separation temperature of 0 to 100°C, preferably 10 to 50°C, and a pressure of 0.1 to 0.7 MPa, preferably 0.1 to 0.3 MPa.

[0027] Optionally, the method further includes:

[0028] The gaseous material obtained from gas-liquid separation in step S3 is introduced into the hydrogen chloride absorption unit and contacted with the hydrogen chloride absorbent for hydrogen chloride absorption treatment to obtain non-condensable pyrolysis gas; the non-condensable pyrolysis gas is then introduced into the gas storage unit.

[0029] Optionally, the hydrogen chloride absorbent is selected from one or more of water and alkaline solutions with a pH greater than 7; optionally, the alkaline solution is selected from one or more of sodium hydroxide solution, potassium hydroxide solution, calcium hydroxide suspension, sodium bicarbonate solution, sodium carbonate solution, and ammonia water.

[0030] A second aspect of this disclosure provides a system for dechlorinating pyrolysis oil of chlorinated plastics. The system includes a heating unit, a dechlorination reaction unit, and a separation unit. The heating unit includes a chlorinated plastic pyrolysis oil inlet and a chlorinated gas phase outlet. The heating unit is configured to heat and vaporize the chlorinated plastic pyrolysis oil in the heating unit to obtain a chlorinated gas phase.

[0031] The dechlorination reaction unit includes a chlorine-containing gas phase inlet, a dechlorinating agent, and a dechlorination gas phase outlet; the chlorine-containing gas phase inlet is connected to the chlorine-containing gas phase outlet of the heating unit; the dechlorination reaction unit is configured to allow the chlorine-containing gas phase from the heating unit to contact the dechlorinating agent in the dechlorination reaction unit to carry out a dechlorination reaction and obtain a dechlorinated gas phase;

[0032] The separation unit includes a dechlorination gas phase inlet and a dechlorination plastic oil liquid phase outlet; the dechlorination gas phase inlet is connected to the dechlorination gas phase outlet of the dechlorination reaction unit; the separation unit is configured to perform gas-liquid separation of the dechlorination gas phase in the separation unit to obtain the dechlorination plastic oil liquid phase.

[0033] Optionally, the system further includes a hydrogen chloride absorption unit and a gas storage unit; the hydrogen chloride absorption unit includes a gaseous material inlet, a hydrogen chloride absorbent, and a non-condensable pyrolysis gas outlet;

[0034] The separation unit also includes a gaseous material outlet, which is connected to the gaseous material inlet of the hydrogen chloride absorption unit;

[0035] The hydrogen chloride absorption unit is configured to contact the gaseous material obtained from the gas-liquid separation of the separation unit with the hydrogen chloride absorbent in the hydrogen chloride absorption unit to perform hydrogen chloride absorption treatment and obtain non-condensable pyrolysis gas.

[0036] The non-condensable pyrolysis gas outlet of the hydrogen chloride absorption unit is connected to the inlet of the gas storage unit.

[0037] Through the above technical solution, this disclosure provides a method and system for dechlorinating chlorinated plastic pyrolysis oil. By directly heating and vaporizing the chlorinated plastic pyrolysis oil with high chlorine content, and then using a dechlorinating agent to effectively dechlorinate the vaporized chlorine-containing gas phase, the chlorine content in the oil can be reduced to below 10 μg / g. Moreover, the process is simple, the equipment investment is low, and the dechlorination effect is excellent, which has significant economic benefits and good industrial application prospects.

[0038] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0039] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0040] Figure 1 This is a schematic diagram of a system for dechlorinating pyrolysis oil from chlorinated plastics, as disclosed in this publication.

[0041] Explanation of reference numerals in the attached figures

[0042] 1-Chlorine-containing plastic pyrolysis oil, 2-Heating unit, 3-Dechlorination reaction unit, 4-Separation unit, 5-Pyrolysis oil storage unit, 6-Hydrogen chloride absorption unit, 7-Gas storage unit. Detailed Implementation

[0043] The following provides a detailed description of specific embodiments of this disclosure. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit this disclosure.

[0044] The first aspect of this disclosure provides a method for dechlorinating pyrolysis oil from chlorinated plastics, comprising the following steps:

[0045] S1. The chlorine-containing plastic pyrolysis oil is heated and vaporized in a heating unit to obtain a chlorine-containing gas phase;

[0046] S2. The chlorine-containing gas phase is introduced into the dechlorination reaction unit to contact the dechlorination agent and carry out the dechlorination reaction to obtain a dechlorinated gas phase;

[0047] S3. The dechlorinated gas phase is introduced into the separation unit for gas-liquid separation to obtain the dechlorinated plastic oil phase.

[0048] This disclosure provides a method for dechlorinating pyrolysis oil containing chlorine. The method involves directly heating and vaporizing the pyrolysis oil containing chlorine with high chlorine content, and then effectively dechlorinating the vaporized chlorine-containing gas phase using a dechlorinating agent. The chlorine content in the oil can be reduced to below 10 μg / g. Furthermore, the process is simple, requires low equipment investment, and has excellent dechlorination effect, resulting in significant economic benefits and promising prospects for industrial application.

[0049] In one embodiment, the chlorinated plastic pyrolysis oil is derived from non-catalytic pyrolysis of chlorinated plastic raw materials, catalytic pyrolysis of chlorinated plastic raw materials, fluidized bed pyrolysis of chlorinated plastic raw materials, rotary kiln pyrolysis of chlorinated plastic raw materials, oil-plastic co-processing of chlorinated plastic raw materials, and screw extrusion pyrolysis of chlorinated plastic raw materials. The method provided in this disclosure is applicable to chlorinated plastic pyrolysis oil from various sources, has a wide range of applications, and can achieve efficient dechlorination for chlorinated plastic pyrolysis oil from different sources.

[0050] In one specific embodiment, the chlorine-containing plastic raw material includes polyvinyl chloride; the chlorine-containing plastic raw material also includes one or more selected from low-density polyethylene, high-density polyethylene, polypropylene, and polystyrene;

[0051] Preferably, the chlorine content in the chlorine-containing plastic pyrolysis oil is 10–4000 μg / g, more preferably 10–2500 μg / g; optionally, the chlorine-containing plastic pyrolysis oil further includes 20–500 μg / g of silicon.

[0052] In one specific embodiment, the initial boiling point of the chlorine-containing plastic pyrolysis oil is any value between 10 and 100°C; the final boiling point is any value between 400 and 500°C.

[0053] In a preferred embodiment, the chlorine-containing plastic pyrolysis oil is prepared by a method comprising the following steps: feeding chlorine-containing waste plastic raw materials into a pyrolysis reactor and pyrolyzing them at 460–500°C for 1–3 hours; preferably, the heating rate of the chlorine-containing waste plastic raw materials in the pyrolysis reactor is 5–10°C / min; and optionally, nitrogen gas is continuously purged or not purged during the reaction.

[0054] The obtained pyrolysis products were separated to obtain chlorine-containing plastic pyrolysis oil, coke and pyrolysis gas;

[0055] Optionally, the chlorine-containing waste plastic raw material includes polyvinyl chloride; the chlorine-containing waste plastic raw material also includes one or more selected from low-density polyethylene, high-density polyethylene, polypropylene and polystyrene, wherein the chlorine-containing waste plastic raw material includes 1 to 6% by weight of polyvinyl chloride.

[0056] In one specific embodiment, before pyrolyzing the chlorine-containing waste plastic raw material, the method further includes: crushing and removing impurities from the chlorine-containing waste plastic raw material to obtain chlorine-containing waste plastic particles, which are then fed into the pyrolysis reaction device.

[0057] In a more specific embodiment, the chlorinated plastic pyrolysis oil is prepared by a method comprising the following steps: pulverizing and removing impurities from a mixed plastic containing vinyl chloride, low-density polyethylene, high-density polyethylene, polypropylene, and polystyrene to obtain chlorinated waste plastic particles, wherein the polyvinyl chloride content is 3% by weight; then, the chlorinated waste plastic is fed into a pyrolysis reactor and pyrolyzed at 480°C for 2 hours at a heating rate of 5°C / min; during the reaction, nitrogen gas can be continuously purged; the obtained pyrolysis products are separated by a separation unit to obtain chlorinated plastic pyrolysis oil, coke, and pyrolysis gas, etc.

[0058] In one embodiment, the heating and vaporization conditions in step S1 include: a temperature of 100–600°C, a pressure of 0.1–1.5 MPa, and a time of 0.1–2 h; optionally, the heating rate is 5–30°C / min. In this disclosure, conventionally structured devices, such as heating furnaces, can be used for heating and vaporization.

[0059] In a preferred embodiment, in step S1, the heating and vaporization conditions include: a temperature of 300–520°C, a pressure of 0.1–1 MPa, and a time of 0.3–1 h; optionally, the heating rate is 10–25°C / min. Heating and vaporizing plastic pyrolysis oil according to the optimized heating and vaporization conditions provided in this embodiment can achieve better vaporization efficiency and improve the overall dechlorination effect of the process.

[0060] In one specific embodiment, the temperature of the chlorine-containing gas phase at the outlet of the heating unit is 200–550°C, preferably 300–500°C, and the outlet pressure is 0.1–1.5 MPa, preferably 0.1–1 MPa.

[0061] Preferably, the liquid phase content carried by the chlorine-containing gas phase drawn out from the outlet of the heating unit is less than 10% by weight, and more preferably less than 5% by weight.

[0062] In one specific embodiment, the chlorine content in the chlorine-containing gas phase obtained in step S2 is 10–4000 μg / g, preferably 10–2500 μg / g.

[0063] In one embodiment, in step S2, the conditions for the dechlorination reaction include: a weight hourly space velocity (WHSV) of 5–100 h⁻¹ for the chlorine-containing gas phase. -1 The reaction temperature is 200–500℃; the pressure is 0.1–1 MPa.

[0064] Preferably, the inlet temperature of the chlorine-containing gas phase in the dechlorination reaction unit is 250–480°C, and the inlet pressure is 0.1–1 MPa.

[0065] In a preferred embodiment, in step S2, the conditions for the dechlorination reaction include: a space velocity of 10–50 h⁻¹ for the chlorine-containing gas phase.-1 The reaction temperature is 300–450℃; the pressure is 0.1–0.5 MPa.

[0066] Preferably, the inlet temperature of the chlorine-containing gas phase in the dechlorination reaction unit is 300–450°C, and the inlet pressure is 0.1–0.5 MPa. According to the optimized dechlorination conditions provided in this embodiment, a better dechlorination effect can be obtained.

[0067] In one specific embodiment, the chlorine content in the dechlorinated plastic oil phase obtained by the method provided in this disclosure is less than 50 g / g, preferably less than 10 μg / g.

[0068] In this disclosure, the chlorine content in the material was determined using the method Q / SH 3360 270-2018.

[0069] In one embodiment, in step S2, the dechlorinating agent is selected from one or more of metal oxides, metal hydroxides, and carbonates; preferably, the metal oxide is selected from one or more of calcium oxide, aluminum oxide, iron oxide, magnesium oxide, zinc oxide, nickel oxide, and copper oxide; the metal hydroxide is selected from one or more of calcium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, iron hydroxide, and aluminum hydroxide; and the carbonate is selected from one or more of calcium carbonate, sodium carbonate, potassium carbonate, magnesium carbonate, zinc carbonate, barium carbonate, magnesium carbonate, copper carbonate, and ammonium carbonate. This disclosure uses the above-mentioned types of dechlorinating agents, which can promote the decomposition of organochlorines while simultaneously adsorbing hydrogen chloride produced by the decomposition of organochlorines in situ, thereby effectively removing chlorine from the chlorine-containing gas phase.

[0070] In a preferred embodiment, the dechlorinating agent is selected from one or more of calcium oxide, zinc oxide, calcium carbonate, sodium carbonate, magnesium carbonate, calcium hydroxide, and magnesium hydroxide. Using the dechlorinating agent provided in this embodiment can achieve a better dechlorination effect.

[0071] In this disclosure, the dechlorination reaction unit can be a device with a conventional structure in the art, such as a fixed-bed reactor, a moving-bed reactor, or a fluidized-bed reactor.

[0072] In one specific embodiment, the conditions for gas-liquid separation in step S3 include: a gas-liquid separation temperature of 0–100°C, preferably 10–50°C, and a pressure of 0.1–0.7 MPa, preferably 0.1–0.3 MPa.

[0073] In one embodiment, the method further includes:

[0074] The gaseous material obtained from gas-liquid separation in step S3 is introduced into a hydrogen chloride absorption unit and contacted with a hydrogen chloride absorbent for hydrogen chloride absorption treatment to obtain non-condensable pyrolysis gas; the non-condensable pyrolysis gas is then introduced into a gas storage unit. The obtained non-condensable pyrolysis gas can be used as a gaseous fuel or as a raw material for the chemical industry.

[0075] In one specific embodiment, the hydrogen chloride absorbent is selected from one or more of water and alkaline solutions with a pH greater than 7; optionally, the alkaline solution is selected from one or more of sodium hydroxide solution, potassium hydroxide solution, calcium hydroxide suspension, sodium bicarbonate solution, sodium carbonate solution, and ammonia water.

[0076] A second aspect of this disclosure provides a system for dechlorinating pyrolysis oil of chlorinated plastics. The system includes a heating unit, a dechlorination reaction unit, and a separation unit. The heating unit includes a chlorinated plastic pyrolysis oil inlet and a chlorinated gas phase outlet. The heating unit is configured to heat and vaporize the chlorinated plastic pyrolysis oil in the heating unit to obtain a chlorinated gas phase.

[0077] The dechlorination reaction unit includes a chlorine-containing gas phase inlet, a dechlorinating agent, and a dechlorination gas phase outlet; the chlorine-containing gas phase inlet is connected to the chlorine-containing gas phase outlet of the heating unit; the dechlorination reaction unit is configured to allow the chlorine-containing gas phase from the heating unit to contact the dechlorinating agent in the dechlorination reaction unit to carry out the dechlorination reaction and obtain a dechlorinated gas phase;

[0078] The separation unit includes a dechlorination gas phase inlet and a dechlorination plastic oil liquid phase outlet; the dechlorination gas phase inlet is connected to the dechlorination gas phase outlet of the dechlorination reaction unit; the separation unit is configured to perform gas-liquid separation of the dechlorination gas phase in the separation unit to obtain the dechlorination plastic oil liquid phase.

[0079] In a preferred embodiment, the system further includes a hydrogen chloride absorption unit and a gas storage unit; the hydrogen chloride absorption unit includes a gaseous material inlet, a hydrogen chloride absorbent, and a non-condensable pyrolysis gas outlet;

[0080] The separation unit also includes a gaseous material outlet, which is connected to the gaseous material inlet of the hydrogen chloride absorption unit;

[0081] The hydrogen chloride absorption unit is configured to contact the gaseous material obtained from the gas-liquid separation of the separation unit with the hydrogen chloride absorbent in the hydrogen chloride absorption unit to perform hydrogen chloride absorption treatment and obtain non-condensable pyrolysis gas.

[0082] The non-condensable pyrolysis gas outlet of the hydrogen chloride absorption unit is connected to the inlet of the gas storage unit.

[0083] In one specific implementation, such as Figure 1As shown, the dechlorination system for pyrolysis oil of chlorinated plastics includes a heating unit 2, a dechlorination reaction unit 3, a separation unit 4, a pyrolysis oil storage unit 5, a hydrogen chloride absorption unit 6, and a gas storage unit 7. The heating unit 2 includes a chlorinated plastic pyrolysis oil inlet and a chlorinated gas phase outlet. The dechlorination reaction unit 3 includes a chlorinated gas phase inlet, a dechlorinating agent, and a dechlorinated gas phase outlet; the chlorinated gas phase inlet is connected to the chlorinated gas phase outlet of the heating unit 2. The separation unit 4 includes a dechlorinated gas phase inlet, a dechlorinated plastic oil liquid phase outlet, and a gas phase material outlet; the dechlorinated gas phase inlet is connected to the dechlorinated gas phase outlet of the dechlorination reaction unit 3, and the dechlorinated plastic oil liquid phase outlet is connected to the inlet of the pyrolysis oil storage unit 5. The hydrogen chloride absorption unit 6 includes a gas phase material inlet, a hydrogen chloride absorbent, and a non-condensable pyrolysis gas outlet; the gas phase material outlet of the separation unit 4 is connected to the gas phase material inlet of the hydrogen chloride absorption unit 6; and the non-condensable pyrolysis gas outlet of the hydrogen chloride absorption unit 6 is connected to the inlet of the gas storage unit 7.

[0084] Adopt this disclosure Figure 1 The specific process flow for dechlorinating pyrolysis oil of chlorinated plastics, as shown in the system, includes:

[0085] The chlorinated plastic pyrolysis oil 1 is heated and vaporized in heating unit 2 to obtain a chlorinated gas phase. Then, the chlorinated gas phase is introduced into dechlorination reaction unit 3 to contact with a dechlorinating agent and undergo a dechlorination reaction to obtain a dechlorinated gas phase. The dechlorinated gas phase is introduced into separation unit 4 for gas-liquid separation to obtain a dechlorinated plastic oil liquid phase and a gas phase material containing non-condensable pyrolysis gas and hydrogen chloride. The dechlorinated plastic oil liquid phase is introduced into pyrolysis oil storage unit 5, and the obtained gas phase material is introduced into hydrogen chloride absorption unit 6 to contact with a hydrogen chloride absorbent for hydrogen chloride absorption treatment to obtain non-condensable pyrolysis gas. The non-condensable pyrolysis gas is introduced into gas storage unit 7.

[0086] The present disclosure is further described in detail below through examples. All raw materials used in the examples are commercially available.

[0087] In the following embodiments, chlorinated plastic pyrolysis oil A is derived from the non-catalytic pyrolysis reaction of PVC plastics, with a chlorine content of 1520 μg / g and also including 50 μg / g of silicon; the distillation range is 24–495°C. This chlorinated plastic pyrolysis oil A is prepared by the following method: the chlorinated plastic raw materials include polyvinyl chloride, low-density polyethylene, high-density polyethylene, polypropylene, and polystyrene, with a polyvinyl chloride content of 3% by weight. Then, the chlorinated waste plastics are fed into a pyrolysis reactor and pyrolyzed at 480°C for 2 hours at a heating rate of 5°C / min. During the reaction, nitrogen can be continuously purged. The resulting pyrolysis products are separated by a separation unit to obtain chlorinated plastic pyrolysis oil, coke, and pyrolysis gas.

[0088] Chlorine-containing plastic pyrolysis oil B is derived from the pyrolysis of PVC-containing plastics in a rotary kiln. It contains 2160 μg / g of chlorine and 200 μg / g of silicon, with a distillation range of 35–507℃. This chlorine-containing plastic pyrolysis oil B is prepared by the following method: the chlorine-containing plastic raw materials include polyvinyl chloride (PVC), low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), and polystyrene, with PVC content at 3% by weight. The chlorine-containing waste plastics are then fed into a pyrolysis reactor and pyrolyzed at 470℃ for 2 hours at a heating rate of 10℃ / min. Nitrogen purging may not be necessary during the reaction. The resulting pyrolysis products are separated by a separation unit to obtain chlorine-containing plastic pyrolysis oil, coke, and pyrolysis gas.

[0089] In the following embodiments, the conditions for gas-liquid separation are: temperature of 10–50°C and pressure of 0.1–0.3 MPa.

[0090] Example 1

[0091] according to Figure 1 The process flow shown involves adding chlorine-containing plastic pyrolysis oil A with a chlorine content of 1520 μg / g to a heating furnace for high-temperature heating and vaporization. The heating furnace temperature is 490℃. In a fixed-bed reactor, calcium carbonate is used as the dechlorinating agent, with a loading of 10 mL and a heating temperature of 400℃. The dechlorinated vapor is then separated into liquid phase products by a condenser. HCl is then separated from the non-condensable pyrolysis gas in a hydrogen chloride absorption unit and absorbed. The byproduct non-condensable pyrolysis gas enters a gas storage tank, ultimately yielding low-chlorine plastic pyrolysis oil. Specific process parameters are listed in Table 1, and the chlorine content of the obtained low-chlorine plastic pyrolysis oil is listed in Table 2.

[0092] Comparative Example 1

[0093] Referring to the method shown in Example 1, the difference between this comparative example and Example 1 is that the chlorine-containing plastic pyrolysis oil A is not heated and vaporized, but directly enters the dechlorination reaction unit for dechlorination reaction. The specific process parameters are listed in Table 1, and the chlorine content of the resulting low-chlorine plastic pyrolysis oil is listed in Table 2.

[0094] Comparative Example 2

[0095] This comparative example follows the method disclosed in Example 1 of patent CN111662732A to dechlorinate waste plastics during pyrolysis. The chlorine content of the resulting low-chlorine plastic pyrolysis oil is listed in Table 2.

[0096] Example 2

[0097] according to Figure 1The process flow shown involves adding chlorinated plastic pyrolysis oil A with a chlorine content of 1520 μg / g to a heating furnace for high-temperature heating and vaporization at 490℃. In a fixed-bed reactor, sodium carbonate is used as the dechlorinating agent, with a loading of 10 mL and a heating temperature of 400℃. The dechlorinated vapor is then separated into liquid phase products by a condenser. HCl is then separated from the non-condensable pyrolysis gas in a hydrogen chloride absorption unit and absorbed. The byproduct non-condensable pyrolysis gas enters a gas storage tank, ultimately yielding low-chlorinated plastic pyrolysis oil. Specific process parameters are listed in Table 1, and the chlorine content of the obtained low-chlorinated plastic pyrolysis oil is listed in Table 2.

[0098] Example 3

[0099] according to Figure 1 The process flow shown involves adding chlorinated plastic pyrolysis oil A with a chlorine content of 1520 μg / g to a heating furnace for high-temperature heating and vaporization at 490℃. In a fixed-bed reactor, calcium oxide is used as the dechlorinating agent, with a loading of 10 mL and a heating temperature of 400℃. The dechlorinated vapor is then separated into liquid phase products by a condenser. HCl is then separated from the non-condensable pyrolysis gas in a hydrogen chloride absorption unit and absorbed. The byproduct non-condensable pyrolysis gas enters a gas storage tank, ultimately yielding low-chlorinated plastic pyrolysis oil. Specific process parameters are listed in Table 1, and the chlorine content of the obtained low-chlorinated plastic pyrolysis oil is listed in Table 2.

[0100] Example 4

[0101] according to Figure 1 The process flow shown involves adding chlorine-containing plastic pyrolysis oil A with a chlorine content of 1520 μg / g to a heating furnace for high-temperature heating and vaporization. The heating furnace temperature is 490℃. In a fixed-bed reactor, calcium carbonate is used as the dechlorinating agent, with a loading of 10 mL and a heating temperature of 450℃. The dechlorinated vapor is then separated into liquid phase products by a condenser. HCl is then separated from the non-condensable pyrolysis gas in a hydrogen chloride absorption unit and absorbed. The byproduct non-condensable pyrolysis gas enters a gas storage tank, ultimately yielding low-chlorine pyrolysis oil. Specific process parameters are listed in Table 1, and the chlorine content of the obtained low-chlorine pyrolysis oil is listed in Table 2.

[0102] Example 5

[0103] according to Figure 1 The process flow shown involves adding chlorinated plastic pyrolysis oil A with a chlorine content of 1520 μg / g to a heating furnace for high-temperature heating and vaporization at 460℃. In a fixed-bed reactor, calcium carbonate is used as the dechlorinating agent, with a loading of 10 mL and a heating temperature of 400℃. The dechlorinated vapor is then separated into liquid phase products by a condenser. HCl is then separated from the non-condensable pyrolysis gas in a hydrogen chloride absorption unit and absorbed. The byproduct non-condensable pyrolysis gas enters a gas storage tank, ultimately yielding low-chlorinated plastic pyrolysis oil. Specific process parameters are listed in Table 1, and the chlorine content of the obtained low-chlorinated plastic pyrolysis oil is listed in Table 2.

[0104] Example 6

[0105] according to Figure 1 The process flow shown involves adding chlorine-containing plastic pyrolysis oil B with a chlorine content of 2160 μg / g to a heating furnace for high-temperature heating and vaporization at 490℃. In a fixed-bed reactor, calcium carbonate is used as the dechlorinating agent, with a loading of 10 mL and a heating temperature of 400℃. The dechlorinated vapor is then separated into liquid phase products by a condenser. HCl is then separated from the non-condensable pyrolysis gas in a hydrogen chloride absorption unit and absorbed. The byproduct non-condensable pyrolysis gas enters a gas storage tank, ultimately yielding low-chlorine plastic pyrolysis oil. Specific process parameters are listed in Table 1, and the chlorine content of the obtained low-chlorine plastic pyrolysis oil is listed in Table 2.

[0106] Example 7

[0107] Referring to the method shown in Example 1, the difference between this example and Example 1 is that the dechlorinating agent is replaced with sodium carbonate, and the rest of the process is the same as in Example 1. The specific process parameters are listed in Table 1, and the chlorine content of the resulting low-chlorinated plastic pyrolysis oil is listed in Table 2.

[0108] Example 8

[0109] Referring to the method shown in Example 1, the difference between this example and Example 1 is that the dechlorinating agent is replaced with activated carbon (purchased from Maclean's Reagent, MDL No.: MFCD00133992). The rest of the process is the same as in Example 1. The specific process parameters are listed in Table 1, and the chlorine content of the resulting low-chlorinated plastic pyrolysis oil is listed in Table 2.

[0110] Example 9

[0111] Referring to the method shown in Example 1, the difference between this example and Example 1 is that the chlorine-containing plastic pyrolysis oil is dechlorinated according to the conditions listed in Table 1 below, and the chlorine content of the resulting low-chlorine plastic pyrolysis oil is listed in Table 2.

[0112] Example 10

[0113] Referring to the method shown in Example 1, the difference between this example and Example 1 is that the dechlorinating agent is replaced with alumina, and the rest of the process is the same as in Example 1. The specific process parameters are listed in Table 1, and the chlorine content of the resulting low-chlorinated plastic pyrolysis oil is listed in Table 2.

[0114] Table 1

[0115]

[0116] The test method for the content of liquid phase carried by chlorine gas includes: ASTM D 7169 test.

[0117] Table 2

[0118]

[0119] The dechlorination rate is calculated as follows: (chlorine content of chlorinated plastic pyrolysis oil - chlorine content of treated low-chlorinated plastic pyrolysis oil) / chlorine content of chlorinated plastic pyrolysis oil × 100%.

[0120] According to the data in Tables 1 and 2:

[0121] Compared with Comparative Example 1 (the pyrolysis oil containing chlorine was not heated and vaporized) and Comparative Example 2 (dechlorination was performed during the pyrolysis of waste plastics), the low-chlorine pyrolysis oil treated according to the method provided in this disclosure has a lower chlorine content.

[0122] Comparing Examples 1-7 with Example 8, it can be seen that in Examples 1-7, metal oxides, metal hydroxides, and carbonates were used as dechlorination agents. The chlorine content of the low-chlorine plastic pyrolysis oil treated in Examples 1-7 can reach 10.0 μg / g or less, and the dechlorination rate can reach more than 99% by weight. This shows that the dechlorination agent provided in this disclosure can achieve better dechlorination effect.

[0123] Comparing Examples 1-7 with Example 9, it can be seen that Examples 1-7 dechlorinated pyrolysis oil of chlorine-containing plastics according to the optimized reaction conditions in the embodiments of this disclosure, and the low-chlorine pyrolysis oil of chlorine-containing plastics treated in Examples 1-7 has a lower chlorine content and a higher dechlorination rate.

[0124] Comparing Example 1 with Example 10, it can be seen that Example 1 uses a preferred type of dechlorination agent, and the low-chlorine plastic pyrolysis oil treated in Example 1 has a lower chlorine content and a higher dechlorination rate.

[0125] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0126] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0127] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for dechlorinating pyrolysis oil from chlorinated plastics, characterized in that, Includes the following steps: S1. The chlorine-containing plastic pyrolysis oil is heated and vaporized in a heating unit to obtain a chlorine-containing gas phase; the liquid phase content carried by the chlorine-containing gas phase drawn out from the outlet of the heating unit is less than 10% by weight. S2. The chlorine-containing gas phase is introduced into the dechlorination reaction unit to contact the dechlorination agent and carry out the dechlorination reaction to obtain a dechlorinated gas phase; S3. The dechlorinated gas phase is introduced into the separation unit for gas-liquid separation to obtain the dechlorinated plastic oil phase; In step S1, the heating and vaporization conditions include: a temperature of 300~490℃, a pressure of 0.1~1MPa, and a time of 0.3~1h; the outlet temperature of the chlorine-containing gas phase at the outlet of the heating unit is 300~470℃, and the outlet pressure is 0.1~1MPa. In step S2, the conditions for the dechlorination reaction include: a weight hourly space velocity (WHSV) of 10–50 h⁻¹ for the chlorine-containing gas phase. -1 The reaction temperature is 300~450℃; the pressure is 0.1~0.5MPa; the inlet temperature of the chlorine-containing gas phase in the dechlorination reaction unit is 300~450℃, and the inlet pressure is 0.1~0.5MPa; the dechlorination agent is selected from one or more of metal oxides, metal hydroxides, and carbonates. In step S3, the chlorine content in the dechlorinated plastic oil phase obtained is less than 10 μg / g.

2. The method according to claim 1, characterized in that, The chlorinated plastic pyrolysis oil comes from the non-catalytic pyrolysis reaction of chlorinated plastic raw materials and / or the catalytic pyrolysis reaction of chlorinated plastic raw materials.

3. The method according to claim 1, characterized in that, The chlorinated plastic pyrolysis oil is derived from one or more of the following: fluidized bed pyrolysis of chlorinated plastic raw materials, rotary kiln pyrolysis of chlorinated plastic raw materials, oil-plastic co-processing of chlorinated plastic raw materials, and screw extrusion pyrolysis of chlorinated plastic raw materials.

4. The method according to claim 2 or 3, characterized in that, The chlorine-containing plastic raw material includes polyvinyl chloride; the chlorine-containing plastic raw material also includes one or more selected from low-density polyethylene, high-density polyethylene, polypropylene and polystyrene.

5. The method according to claim 1, characterized in that, The chlorine content in the chlorine-containing plastic pyrolysis oil is 10~4000μg / g.

6. The method according to claim 5, characterized in that, The chlorine content in the chlorine-containing plastic pyrolysis oil is 10~2500μg / g.

7. The method according to claim 5, characterized in that, The chlorine-containing plastic pyrolysis oil also contains 20~500μg / g of silicon.

8. The method according to claim 1, characterized in that, The initial boiling point of the chlorine-containing plastic pyrolysis oil is any value between 10 and 100°C, and the final boiling point is any value between 400 and 500°C.

9. The method according to claim 1, characterized in that, The chlorine-containing plastic pyrolysis oil is prepared by a method comprising the following steps: Chlorine-containing waste plastic raw materials are fed into a pyrolysis reactor and pyrolyzed at 460~500℃ for 1~3 hours; nitrogen gas can be continuously purged or not purged during the reaction. The obtained pyrolysis products were separated to obtain chlorine-containing plastic pyrolysis oil, coke, and pyrolysis gas.

10. The method according to claim 9, characterized in that, The chlorine-containing waste plastic raw material is heated at a rate of 5~10℃ / min in the pyrolysis reactor.

11. The method according to claim 9, characterized in that, The chlorine-containing waste plastic raw material includes 1-6% by weight of polyvinyl chloride.

12. The method according to claim 1, characterized in that, In step S1, the conditions for heating and vaporization include a heating rate of 5~30℃ / min.

13. The method according to claim 12, characterized in that, In step S1, the conditions for heating and vaporization include a heating rate of 10~25℃ / min.

14. The method according to claim 1, characterized in that, In step S1, the chlorine content in the chlorine-containing gas phase is 10~4000μg / g.

15. The method according to claim 14, characterized in that, In step S1, the chlorine content in the chlorine-containing gas phase is 10~2500μg / g.

16. The method according to claim 1, characterized in that, In step S1, the liquid phase content carried by the chlorine-containing gas phase drawn out from the outlet of the heating unit is less than 5% by weight.

17. The method according to claim 1, characterized in that, In step S2, the metal oxide is selected from one or more of calcium oxide, aluminum oxide, iron oxide, magnesium oxide, zinc oxide, nickel oxide, and copper oxide; the metal hydroxide is selected from one or more of calcium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, iron hydroxide, and aluminum hydroxide; and the carbonate is selected from one or more of calcium carbonate, sodium carbonate, potassium carbonate, magnesium carbonate, zinc carbonate, barium carbonate, copper carbonate, and ammonium carbonate.

18. The method according to claim 17, characterized in that, In step S2, the dechlorination agent is selected from one or more of calcium oxide, zinc oxide, calcium carbonate, sodium carbonate, magnesium carbonate, calcium hydroxide, and magnesium hydroxide.

19. The method according to claim 1, characterized in that, The conditions for gas-liquid separation in step S3 include: a gas-liquid separation temperature of 0~100℃ and a pressure of 0.1~0.7MPa.

20. The method according to claim 19, characterized in that, The conditions for gas-liquid separation in step S3 include: a gas-liquid separation temperature of 10~50℃ and a pressure of 0.1~0.3MPa.

21. The method according to claim 1, characterized in that, The method also includes: The gaseous material obtained from gas-liquid separation in step S3 is introduced into the hydrogen chloride absorption unit and comes into contact with the hydrogen chloride absorbent for hydrogen chloride absorption treatment to obtain non-condensable pyrolysis gas; the non-condensable pyrolysis gas is then introduced into the gas storage unit.

22. The method according to claim 21, characterized in that, The hydrogen chloride absorbent is selected from one or more of water and alkaline solutions with a pH greater than 7.

23. The method according to claim 22, characterized in that, The alkaline solution is selected from one or more of sodium hydroxide solution, potassium hydroxide solution, calcium hydroxide suspension, sodium bicarbonate solution, sodium carbonate solution, and ammonia water.

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