Production unit for producing wax-based chemicals and α-olefins by downer catalytic pyrolysis of waste plastics

Abstract

The invention relates to a device for producing wax-based chemicals and α-olefins by catalytic pyrolysis of waste plastics in a descending bed. After the clean waste plastics are crushed, they are connected to a water-cooled feed pipe through a controllable feeder. The top of the water-cooled feed pipe is provided with a pyrolysis dry gas injection port, and the bottom end is introduced into a hot melt dechlorination reactor. One path of the bottom of the hot melt dechlorination reactor returns to the upper part of the hot melt dechlorination reactor, and the other path is connected to an atomizing feed nozzle. The gas extraction port at the top of the hot melt dechlorination reactor is connected to the desulfurization and dechlorination reactor and the bottom of the riser regenerator; the atomizing feed nozzle is symmetrically installed in the upper part of the descending bed catalytic pyrolysis reactor, and the bottom is connected to an oil-gas-solid separator; the gas phase outlet of the oil-gas-solid separator is connected to a fractionating tower, and the solid phase outlet is connected to the bottom of the riser regenerator; the first-stage and second-stage gas-solid separators are sequentially installed on the top of the riser regenerator and are connected to the top of the descending bed catalytic pyrolysis reactor and the bottom of the riser regenerator; the top of the fractionating tower is connected to the water-cooled feed pipe, and the bottom of the tower is connected to the upper part of the hot melt dechlorination reactor.

Description

Technical Field

[0001] The invention provides a device for producing wax-based chemicals and alpha-olefins by catalytic pyrolysis of waste plastics in a descending bed, belonging to the field of environmental engineering. Background Art

[0002] While the widespread use of plastics has brought significant convenience to people's lives, it has also led to significant levels of white pollution. Plastics have a very short lifespan. A large number of plastic products, especially packaging, are discarded after approximately 6-12 months, and 40% of plastic is discarded after only 1-2 years. Globally, the annual production of plastic waste has reached 50 million tons. For decades, waste plastics have been included as part of municipal solid waste (MSW). According to surveys, waste plastics account for 4%-10% (wt%) or 10%-20% (v%) of MSW in industrialized countries, primarily from packaging waste, automobile waste, and processing waste. The percentages of various types of waste plastics are as follows: low-density polyethylene (LDPE) 27%; high-density polyethylene (HDPE) 21%; polypropylene (PP) 18%; polystyrene (PS) 16%; and polyvinyl chloride (PVC) 7%. Due to the lack of efficient, clean, and scalable technologies, waste plastics have become a pressing environmental challenge worldwide.

[0003] Landfill, incineration, and recycling are the three main methods used to treat urban plastic solid waste. Currently, rapid pyrolysis / catalytic pyrolysis of waste plastics to liquefy or produce chemicals has become a hot topic both domestically and internationally, and is also the most promising waste plastics treatment technology for industrialization.

[0004] Rapid pyrolysis / catalytic pyrolysis of waste plastics is an effective recycling method that involves heating waste plastics at high temperatures under oxygen-free or low-oxygen conditions to decompose them and produce valuable products. This includes the pyrolysis and liquefaction of waste plastics to produce gasoline, diesel, petroleum wax, and other chemical raw materials. However, due to the bulky, lightweight nature of waste plastics, their difficulty in compression, airtightness, easy expansion, easy melting and bonding, and poor thermal conductivity, it is difficult to address the challenges of continuous feeding and rapid heating. Currently, most waste plastic pyrolysis and liquefaction processes use reactor-type batch reactions and horizontal rotary kiln reactions, resulting in slow heating rates, severe feed adhesion and coking, low liquid product yields and added value, difficulty in increasing processing capacity, difficulty in scaling up pyrolysis equipment, and significant difficulty in subsequent processing of chlorine-containing liquid products. This restricts the efficient, clean, and large-scale utilization of waste plastics. Currently, there are no large-scale commercial waste plastic pyrolysis units, and there is an urgent need to develop equipment and technology for the production of wax-based chemicals and α-olefins using down-flowing bed catalytic pyrolysis of waste plastics. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of existing waste plastic pyrolysis and liquefaction technologies and provide a waste plastic descending bed catalytic pyrolysis production device for wax-based chemicals and α-olefins. The device utilizes pyrolysis dry gas and high-temperature oil slurry circulation to carry out waste plastic hot melt dechlorination and sulfur removal pretreatment and atomization feeding, solving the problems of pyrolysis feeding and removal of chlorine and sulfur heteroatoms; catalytic pyrolysis regulates C-C bond breakage, inhibits condensation and coking, and achieves controllable cracking of waste plastics; adopts a descending bed reactor to inhibit secondary cracking, eliminate the amplification effect, maximize the production of wax-based chemicals and α-olefins, and improve the catalytic pyrolysis heating rate. It solves five common industry problems: adhesion and coking of waste plastic feed, difficulty in mixing with heat carriers, low yield and added value of liquid products, difficulty in removing chlorine and sulfur heteroatoms in liquid products, which affects subsequent processing, and difficulty in scaling up pyrolysis equipment, thereby achieving efficient, clean, and high-value large-scale utilization of waste plastics.

[0006] The technical solution of the present invention:

[0007] The present invention provides a device for producing wax-based chemicals and α-olefins by catalytic pyrolysis of waste plastics in a descending bed. The clean PE and PP waste plastic crushers that have been sorted are connected to a water-cooled feed pipe through a controllable feeder. The top of the water-cooled feed pipe is provided with a pyrolysis dry gas injection port, and the bottom end is introduced into a hot melt dechlorination reactor with stirring. The bottom of the hot melt dechlorination reactor is connected to a high-speed circulation pipe with heating through a delivery pump on one side and returns to the upper part of the hot melt dechlorination reactor, and the other side is connected to an atomizing feed nozzle in the middle and upper part of the descending bed catalytic pyrolysis reactor. The gas extraction outlet at the top of the hot melt dechlorination reactor is connected to the desulfurization and dechlorination reactor and the bottom of the riser regenerator in turn. The temperature of the water-cooled feed pipe is 20-95°C, the temperature of the slurry melt is 240-320°C, the temperature of the molten plastic liquid high-speed circulation pipe after heating is 20-60°C higher than the temperature of the slurry melt, the flow rate of the high-speed circulation pipe is 2-30m / s, and the ratio of the circulating material to the raw material of the molten plastic liquid is 1-10:1; the atomizing feed nozzle is symmetrically installed on the upper part of the descending bed catalytic pyrolysis reactor. The bottom is connected to the oil-gas-solid separator, the gas phase outlet of the oil-gas-solid separator is connected to the fractionation tower, and the solid phase outlet is connected to the bottom of the riser regenerator through the catalyst return device to be regenerated. The steam dosage of the atomizing feed nozzle is 4%~12% of the raw material amount, the reaction temperature is 410~550℃, the pressure is slightly negative, and the reaction time is 200 milliseconds~2 seconds; the first-stage gas-solid separator and the second-stage gas-solid separator are installed in sequence on the top of the riser regenerator. The first-stage gas-solid separator is connected to the fractionation tower through the first-stage crude catalyst return device. The top of the descending bed catalytic pyrolysis reactor is connected, and the second-stage gas-solid separator is connected to the bottom of the riser regenerator through a secondary fine catalyst return device, and the regeneration temperature is 500-750°C; the distillation tower is equipped with a heavy wax oil outlet, a light wax oil outlet, an α-olefin fraction outlet, and a pyrolysis dry gas outlet. The top of the distillation tower is connected to the water-cooled feed pipe through an induced draft fan, and the oil slurry outlet at the bottom of the tower is connected to the upper part of the hot melt dechlorination reactor, realizing a clean and efficient production device for self-thermal melt dechlorination of waste plastics and wax and α-olefin production by descending bed catalytic pyrolysis.

[0008] The outer wall of the water-cooled feed pipe is provided with a water-cooling jacket, which has a shape of a forward cone, a straight tube or an inverted cone, preferably a forward cone.

[0009] The controllable feeder is a rotary feeder, a double-shaft screw feeder or a single-shaft screw feeder.

[0010] The high-speed circulation tube is heated by electromagnetic induction heating, thermal oil heating, steam heating or resistance heating, preferably electromagnetic induction heating.

[0011] The riser regenerator consists of a turbulent fluidized bed at the bottom and an entrained reactor at the top. The turbulent fluidized bed has a larger equivalent diameter, while the entrained reactor has a smaller equivalent diameter, with a diameter ratio of 2 to 3:1. The entrained reactor can be a straight tube reactor with a uniform equivalent diameter, or it can be composed of large and small straight tubes with diameters of different multiples of the equivalent diameter connected by large and small head pipe fittings, with a diameter ratio of 1.2 to 2:1. The equivalent diameter of the entrained bed is only 10%-50% of the equivalent diameter of the turbulent fluidized bed.

[0012] The present invention will be described in detail with reference to embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Attachment Figure 1 The present invention is a schematic diagram of the process flow of a device for producing wax-based chemicals and α-olefins by catalytic pyrolysis of waste plastics in a descending bed.

[0014] Attachment Figure 1 The drawing settings are as follows:

[0015] 1. Waste plastic pulverizer 2. Controllable feeder 3. Water-cooled feed pipe 4. Hot melt dechlorination reactor 5. Transfer pump 6. High-speed circulation pipe 7. Oil-gas solid separator 8. Desulfurization and dechlorination reactor 9. Fractionator 10. Heavy wax oil outlet 11. Light wax oil outlet 12. α-olefin fraction outlet 13. Pyrolysis dry gas outlet 14. Induced draft fan 15. Waste heat boiler 16. Flue gas outlet 17. Regenerated catalyst return 18. Riser regenerator 19. Gas distributor 20. Inlet pipe 21. Ash discharge port 22. First-stage gas-solid separator 23. First-stage coarse catalyst return 24. Second-stage gas-solid separator 25. Second-stage fine catalyst return

[0016] The process characteristics of the present invention are described in detail below with reference to the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0017] The present invention provides a device for producing wax-based chemicals and α-olefins by catalytic pyrolysis of waste plastics in a descending bed. The clean PE and PP waste plastics crusher 1 is connected to a water-cooled feed pipe 3 through a controllable feeder 2. The top of the water-cooled feed pipe 3 is provided with a pyrolysis dry gas injection port, and the bottom end is connected to a hot melt dechlorination reactor 4 with stirring. The bottom of the hot melt dechlorination reactor 4 is connected to a high-speed circulation pipe 6 with heating through a delivery pump 5 and returns to the upper part of the hot melt dechlorination reactor 4. The other part is connected to the atomizing feed nozzle in the upper part of the descending bed catalytic pyrolysis reactor. The gas extraction port at the top of the hot melt dechlorination reactor 4 is connected to the desulfurization and dechlorination reactor 8 and the bottom of the riser regenerator 18 in sequence. The temperature of the water-cooled feed pipe 3 is 20-95°C, the oil slurry melt is 240-320°C, the temperature of the molten plastic liquid high-speed circulation pipe 6 after heating is 20-60°C higher than the oil slurry melt, the flow rate of the high-speed circulation pipe 6 is 2-30m / s, and the circulation ratio of the molten plastic liquid to the raw material is 1-10:1; atomizing feed nozzles are symmetrically installed at the upper part of the downer catalytic pyrolysis reactor, and the bottom is connected to the oil-gas solid separator 7. The liquid phase outlet of the oil-gas gas-solid separator 7 is connected to the fractionation tower 9, and the solid phase outlet is connected to the bottom of the riser regenerator 18 through the catalyst return device 17 to be produced. The steam dosage of the atomizing feed nozzle is 4% to 12% of the raw material amount, the reaction temperature is 410 to 550 ° C, the pressure is slightly negative, and the reaction time is 200 milliseconds to 2 seconds. The first-stage gas-solid separator 22 and the second-stage gas-solid separator 24 are installed in sequence on the top of the riser regenerator 18. The first-stage gas-solid separator 22 is connected to the downer catalytic pyrolysis reactor through the first-stage crude catalyst return device 23. The top of the fractionating tower 9 is connected to the top of the reactor, and the second-stage gas-solid separator 24 is connected to the bottom of the riser regenerator 18 through the secondary fine catalyst return device 25, and the regeneration temperature is 500-750°C; the fractionating tower 9 is provided with a heavy wax oil outlet 10, a light wax oil outlet 11, an α-olefin fraction outlet 12, and a pyrolysis dry gas outlet 13. The top of the fractionating tower 9 is connected to the water-cooled feed pipe 3 through the induced draft fan 14, and the oil slurry outlet at the bottom of the tower is connected to the upper part of the hot melt dechlorination reactor 4, realizing a clean and efficient production device for self-thermal melt dechlorination of waste plastics and catalytic pyrolysis of wax and α-olefins.

[0018] The outer wall of the water-cooled feed pipe 3 is provided with a water-cooling jacket, which has a shape of a forward cone, a straight tube or an inverted cone, preferably a forward cone.

[0019] The controllable feeder 2 is a rotary feeder, a double-shaft screw feeder or a single-shaft screw feeder.

[0020] The high-speed circulation pipe 6 is heated by electromagnetic induction heating, thermal oil heating, steam heating or resistance heating, preferably electromagnetic induction heating.

[0021] The riser regenerator 18 is composed of a turbulent fluidized bed at the bottom and an entrained reactor at the top. The turbulent fluidized bed has a larger equivalent diameter, while the entrained reactor has a smaller equivalent diameter, with a diameter ratio of 2 to 3:1. The entrained reactor can be a straight tube reactor with a uniform equivalent diameter, or can be composed of large and small straight tubes with diameters of different multiples of the equivalent diameter connected by large and small head pipe fittings, with a diameter ratio of 1.2 to 2:1. The equivalent diameter of the fluidized bed is only 10% to 50% of the equivalent diameter of the turbulent fluidized bed.

[0022] During the specific operation, the clean PE and PP waste plastics that have been sorted are fed into the water-cooled feed pipe 3 at 20-95°C through the waste plastic crusher 1 and the waste plastic fragments are fed into the water-cooled feed pipe 3 at 20-95°C through the controllable feeder 2. The waste plastic fragments are carried by the pyrolysis dry gas and fall into the 240-320°C oil slurry melt of the hot melt dechlorination reactor 4 with stirring. The melt dechlorination and desulfurization pretreatment is carried out by stirring and mixing. The molten plastic liquid extracted from the bottom of the hot melt dechlorination reactor 4 is pressurized and transported by the delivery pump 5. A part of the molten plastic liquid is heated to 20-60°C higher than the temperature of the oil slurry melt through the high-speed circulation pipe 6 with external heating and then returned to the upper part of the hot melt dechlorination reactor 4. The other part is sent to the upper part of the descending bed catalytic pyrolysis reactor as raw material through the atomizing feed nozzle. The gas extracted from the top of the hot melt dechlorination reactor 4 is treated by the desulfurization and dechlorination reactor 8 and then used as the raw material. The fuel gas of the riser regenerator 18 has a flow rate of 2-30 m / s in the high-speed circulation pipe 6, a circulation ratio of the molten plastic liquid to the raw material of 1-10:1, and a steam dosage of 4%-12% of the raw material. The atomized particle feed of the molten plastic liquid and the 600-800°C regenerated catalyst falling from the top of the down-flowing bed catalytic pyrolysis reactor undergo rapid mixing, vaporization, and controllable cracking reaction. The reaction temperature is 410-550°C, the pressure is slightly negative, and the reaction time is 200 milliseconds-2 seconds, maximizing the production of wax-based chemicals and α-olefins. Oil-gas-solid separation is performed at the bottom of the down-flowing bed catalytic pyrolysis reactor. The separated regenerated catalyst flows through the regenerated catalyst return device 17 to the bottom of the riser regenerator 18 for air fluidization char regeneration at 500-750°C and fuel gas combustion-assisted heating. At the top of the riser regenerator 18, the coarse particles of regenerated catalyst separated by the first-stage gas-solid separator 22 are circulated back to the top of the down-bed catalytic pyrolysis reactor through the first-stage solid heat carrier return feeder 23 to catalytically pyrolyze the waste plastics. The fine ash separated by the second-stage gas-solid separator 24 is circulated back to the bottom of the riser regenerator 18 through the second-stage fine catalyst return feeder 25 to continue fluidized coking regeneration. The flue gas is discharged after recovering the waste heat through the waste heat boiler 15. The 410-550°C pyrolysis oil and gas flows into the distillation tower 9 and is separated into α-olefin fraction, light wax oil, heavy wax oil, pyrolysis dry gas and high-temperature oil slurry through the heavy wax oil outlet 10, the light wax oil outlet 11, the α-olefin fraction outlet 12 and the pyrolysis dry gas outlet 13. 3%-20% of the pyrolysis dry gas is circulated back to the water-cooled feed pipe 3 as a carrier gas, and the high-temperature oil slurry with a temperature of ≥350°C is directly circulated back to the upper part of the hot melt dechlorination reactor 4 as a melting heat source.

[0023] The downward-flowing bed catalytic pyrolysis device for producing wax-based chemicals and α-olefins of waste plastics can continuously, on a large scale, efficiently, cleanly and with high value by pyrolysis and utilization of waste plastics. It has solved five common problems in the industry: adhesion and coking of waste plastic feed, difficulty in mixing with high-temperature catalysts, low yield and added value of liquid products, difficulty in scaling up the pyrolysis device, and difficulty in subsequent processing of chlorine-containing liquid products. The yield of liquefied gas is ≥10%, the yield of α-olefin fraction is ≥20%, the light wax oil fraction is 40%, the heavy wax oil fraction is 25%, and the total yield of liquid products is more than 95%, which is more than 25 percentage points higher than that of traditional waste plastic pyrolysis technology. It has high pyrolysis intensity, small equipment size, low steel consumption, greatly reduced fixed investment, simple ash removal process, and realizes stable, long-term and optimal operation of the device.

Claims

1. A device for producing wax-based chemicals and α-olefins by catalytic pyrolysis of waste plastics in a downward bed, characterized in that: The sorted clean PE and PP waste plastics are put into the waste plastic crusher and connected to the water-cooled feed pipe through a controllable feeder. The top of the water-cooled feed pipe is provided with a pyrolysis dry gas injection port, and the bottom is introduced into the hot melt dechlorination reactor with stirring. The bottom of the hot melt dechlorination reactor is connected to a high-speed circulation pipe with heating through a delivery pump and returns to the top of the hot melt dechlorination reactor, and the other is connected to the atomizing feed nozzle in the upper part of the descending bed catalytic pyrolysis reactor. The gas extraction port at the top of the hot melt dechlorination reactor is connected to the desulfurization and dechlorination reactor and the bottom of the riser regenerator in turn. The water-cooled feed pipe The temperature of the molten plastic is 20-95°C, the temperature of the slurry melt is 240-320°C, the temperature of the molten plastic high-speed circulation pipe after heating is 20-60°C higher than the temperature of the slurry melt, the flow rate of the high-speed circulation pipe is 2-30m / s, and the ratio of the circulating material to the raw material of the molten plastic is 1-10:1; the atomizing feed nozzle is symmetrically installed on the upper part of the down-bed catalytic pyrolysis reactor, the bottom is connected to the oil-gas-solid separator, the liquid phase outlet of the oil-gas-solid separator is connected to the distillation tower, and the solid phase outlet is connected to the bottom of the riser regenerator through the catalyst return device to be generated, and the atomizing feed nozzle is symmetrically installed on the upper part of the down-bed catalytic pyrolysis reactor. The steam dosage is 4wt%~12wt% of the raw material amount, the reaction temperature is 410~550℃, the absolute pressure is 80~100Kpa, and the reaction time is 200 milliseconds~2 seconds; the first-stage gas-solid separator and the second-stage gas-solid separator are installed in sequence on the top of the riser regenerator. The first-stage gas-solid separator is connected to the top of the down-bed catalytic pyrolysis reactor through a first-stage coarse catalyst return feeder, and the second-stage gas-solid separator is connected to the bottom of the riser regenerator through a second-stage fine catalyst return feeder. The regeneration temperature is 500-750℃; the distillation tower is equipped with a heavy wax oil outlet , light wax oil outlet, α-olefin fraction outlet, pyrolysis dry gas outlet, the top of the distillation tower is connected to the water-cooled feed pipe through the induced draft fan, and the oil slurry outlet at the bottom of the tower is connected to the upper part of the hot melt dechlorination reactor; the riser regenerator is composed of a turbulent fluidized bed at the bottom and an entrained reactor at the top, and the ratio of the equivalent diameter of the turbulent fluidized bed to the equivalent diameter of the entrained reactor is 2~3:1; the entrained reactor is a straight tube reactor with uniform equivalent diameter, or is composed of large and small straight tubes with diameters of different multiples of the equivalent diameter connected by large and small head pipe fittings, and the diameter ratio of large and small straight tubes is 1.2~2:

1.

2. The device for producing wax-based chemicals and α-olefins by catalytic pyrolysis of waste plastics in a down-flow bed according to claim 1, characterized in that: The outer wall of the water-cooled feed pipe is provided with a water-cooling jacket, which has a shape of a positive cone, a straight pipe or an inverted cone.

3. The device for producing wax-based chemicals and α-olefins by catalytic pyrolysis of waste plastics in a down-flow bed according to claim 1, characterized in that: The controllable feeder is a rotary feeder, a double-shaft screw feeder or a single-shaft screw feeder.

4. The device for producing wax-based chemicals and α-olefins by catalytic pyrolysis of waste plastics in a down-flow bed according to claim 1, characterized in that: The high-speed circulation tube is heated by electromagnetic induction heating, thermal oil heating, steam heating or resistance heating.

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