Process for producing oil products by rapid pyrolysis of waste plastics using dual-carrier cycles

Abstract

The invention provides a process for producing oil products by dual-carrier cyclic rapid pyrolysis of waste plastics. The waste plastic fragments are added to a dual-heat-carrier descending pyrolysis reactor; high-temperature pyrolysis dry gas is ejected from a porous plate with an opening rate of 0.1%-15%, heating the plastic fragments while preventing the plastic fragments from adhering and coking; the hot plastic fragments are then collided and mixed with a primary solid heat carrier; after multiple enhanced mixing and pyrolysis reactions in the mixing internal components of the dual-heat-carrier descending pyrolysis reactor, they flow into a moving bed reactor, where the heat carrier containing the waste plastic melt further undergoes pyrolysis reaction in the moving bed, and the pyrolysis oil vapor flows into a distillation tower and is separated into wax oil, diesel, gasoline and pyrolysis dry gas; the char-containing heat carrier at the bottom of the moving bed reactor is fluidized and burned at the bottom of a riser heating regenerator; large and medium-sized particle heat carriers are separated by a first-stage gas-solid separator at the top of the riser heating regenerator and participate in the rapid pyrolysis of the waste plastics, and fine ash is separated by a second-stage gas-solid separator and circulated back to the bottom of the riser heating regenerator.

Description

Technical Field

[0001] The invention provides a process for preparing oil products by dual-carrier cyclic rapid pyrolysis of waste plastics, and belongs to the field of environmental engineering. Background Art

[0002] In terms of urban plastic solid waste treatment, the three main methods currently used are landfill, incineration and recycling.

[0003] (1) Landfill treatment is adopted because plastic products are large and light (65kg / m 3 ), difficult to compress, airtight, easy to expand and not easy to rot, which will cause the landfill to become a soft foundation, causing water pollution, occupying land, and sewer blockage.

[0004] (2) Incineration for heating or power generation. Plastic waste is a chemical substance extracted from petroleum with a high calorific value. It has the highest average calorific value among domestic waste. In order to make plastic waste energy-efficient and economical, burning plastic waste in an incinerator can provide heat for heating or power generation, which is a solution.

[0005] (3) The recycling and reuse method is labor-intensive, has high recycling costs, and lacks corresponding recycling channels.

[0006] The thermal decomposition 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 products with utility value. This includes the pyrolysis and liquefaction of waste plastics to produce gasoline, diesel, petroleum wax, and other chemical raw materials. However, due to the characteristics of waste plastics, such as being bulky and light, difficult to compress, airtight, easily expandable, easily melted and bonded, and having poor thermal conductivity, it is difficult to solve the problems of continuous feeding and rapid heating. Currently, most of the pyrolysis and liquefaction of waste plastics use reactor-type batch reactions and horizontal rotary kiln reactions, which have slow heating rates, severe feed adhesion and coking, low liquid product yields, difficulty in increasing processing capacity, and difficulty in scaling up pyrolysis equipment. These factors restrict the efficient, clean, and large-scale utilization of waste plastics. Currently, there are no large-scale commercial pyrolysis equipment, and there is an urgent need to develop continuous and rapid pyrolysis and liquefaction processes and equipment technologies for waste plastics. Summary of the Invention

[0007] The purpose of the present invention is to overcome the shortcomings of existing waste plastic pyrolysis and liquefaction technology and provide a process for producing oil-based products by dual-carrier circulation rapid pyrolysis of waste plastic. By classifying the pyrolysis dry gas and rationally utilizing it at different temperatures and combining gas and solid heat carriers in a two-stage manner, the pyrolysis heating rate is improved, solving four common industry problems: adhesion and coking of waste plastic feed, difficulty in mixing with heat carriers, low yield of liquid products, and difficulty in scaling up the pyrolysis device.

[0008] The technical solution of the present invention:

[0009] The process for producing oil-based products by dual-carrier circulating rapid pyrolysis of waste plastics is as follows: the waste plastics are first crushed by a waste plastic crusher, and then the waste plastic fragments of 0 to 30 mm are added to the water-cooled feed pipe with a water-cooled jacket on the top of the dual-heat carrier descending pyrolysis reactor by a controllable feeder. The waste plastic fragments are carried downward by the pyrolysis dry gas into the high-temperature gas hot melting section of the dual-heat carrier descending pyrolysis reactor; the 300°C-600°C pyrolysis dry gas pressurized by the pressurized fan and the pyrolysis dry gas heat exchanger is injected into the high-temperature pyrolysis dry gas inner jacket and evenly sprayed out from the porous plate with an opening rate of 0.1%-15%, heating and melting the waste plastic fragments while preventing the plastic fragments from adhering to the dual-heat carrier descending pyrolysis reactor. Coke forms on the inner wall of the reactor; the mixed pyrolysis dry gas carries the waste plastic melt and flows downward to the high-temperature gas hot melting section at the top of the dual heat carrier descending pyrolysis reactor, collides and mixes with the primary solid heat carrier that enters obliquely from the side, and a pyrolysis reaction occurs; the downward-flowing pyrolysis gas, heat carrier and waste plastic melt pass through the mixing internal components composed of the guide plates in the inner cavity of the dual heat carrier descending pyrolysis reactor for multiple enhanced mixing and pyrolysis reactions, and then flow into the moving bed reactor from one side of the top of the moving bed reactor for initial gas-solid separation; the separated heat carrier containing the waste plastic melt further undergoes a pyrolysis reaction in the moving bed, and the pyrolysis oil vapor is further separated and purified through the oil-gas separator before flowing into the moving bed reactor The pyrolysis oil vapor is separated into wax oil, diesel, gasoline and pyrolysis dry gas in the distillation tower; an induced draft fan is set at the pyrolysis dry gas outlet on the top of the distillation tower, one dry gas is connected to the water-cooled feed pipe as the carrying air, and the other dry gas is pressurized and heated by the booster fan and the pyrolysis dry gas heat exchanger and then returns to the high-temperature pyrolysis dry gas inner jacket of the high-temperature gas hot melt section at the top of the dual heat carrier descending pyrolysis reactor, and the remaining dry gas is sent out as the product; the char-containing heat carrier at the bottom of the moving bed reactor is added to the turbulent bed at the bottom of the riser heating regenerator through the return device of the heat carrier to be generated, and is fluidized and burned by the air added through the air inlet pipe and the gas distributor; the generated flue gas and the carried heat carrier to be generated are passed through the riser The entrained bed at the top of the riser heating regenerator is further burned and heated. The large and medium-sized particles of heat carrier are separated by the first-stage gas-solid separator at the top of the riser heating regenerator, and then the fine ash is separated by the second-stage gas-solid separator. The flue gas recovers heat through the pyrolysis dry gas heat exchanger and the waste heat boiler before being discharged. The large and medium-sized particles of heat carrier separated by the first-stage gas-solid separator are circulated back to the solid heat carrier inlet at the top of the dual-heat carrier descending pyrolysis reactor through the first-stage solid heat carrier return feeder to participate in the rapid pyrolysis of waste plastics. The fine ash separated by the second-stage gas-solid separator is circulated back to the turbulent bed at the bottom of the riser heating regenerator through the hot ash circulation pipe and the hot ash circulation return feeder to maintain fluidized combustion.

[0010] A feed pipe with a water-cooled jacket is provided at the top of the dual-heat-carrier downward pyrolysis reactor, the size of which is 0-100 mm smaller than the reactor inner cavity. A high-temperature pyrolysis dry gas inner jacket with a thickness of 10 mm to 100 mm is formed by the inner cavity and a porous plate with an opening rate of 0.1% to 15% at the upper part of the reactor. The jacket height is 0.5 to 4 times the equivalent diameter of the inner cavity. An inclined solid heat carrier inlet is provided on the side of the upper part of the reactor, located 100 to 1500 mm downward from the top of the reactor and at a horizontal downward angle of 0 to 85 degrees. The reactor inner cavity is provided with a mixed internal component consisting of 1 to 10 guide plates with a horizontal downward inclination of 25 to 85 degrees. Adjacent guide plates are staggered at 180 degrees, and the distance between the bottom end of the guide plate and the opposite inner cavity wall is 100 to 400 mm.

[0011] The controllable feeder is a rotary feeder, a double-shaft screw feeder or a single-shaft screw feeder.

[0012] The equivalent diameter of the upper part of the moving bed reactor is 1.2-4.0 times larger than that of the dual-heat carrier descending pyrolysis reactor. The outlet and oil and gas outlet of the dual-heat carrier descending pyrolysis reactor are respectively installed on both sides of the top of the moving bed reactor; the bottom of the moving bed reactor is conical and directly connected to the return feeder of the heat carrier to be generated with a crushing function.

[0013] The riser heating 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 or a combination of large and small straight tubes with diameters of different multiples of the equivalent diameter connected by large and small head 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.

[0014] The outlet temperature of the dual heat carrier descending pyrolysis reactor is 400-600℃, the reaction temperature at the bottom of the riser heating regenerator is 600-1000℃, and the reaction temperature at the top outlet is 650-1200℃.

[0015] The present invention will be described in detail with reference to embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Attachment Figure 1 This is a schematic flow chart of the process for producing oil products by dual-carrier cyclic rapid pyrolysis of waste plastics according to the present invention.

[0017] 1. Waste Plastics Crusher 2. Controllable Feeder 3. Water-Cooled Feed Pipe 4. High-Temperature Gas Melting Section 5. Dual Heat Carrier Downstream Pyrolysis Reactor 6. Moving Bed Reactor 7. Oil / Gas Separator 8. Fractionation Tower 9. Wax Oil Outlet 10. Diesel Outlet 11. Gasoline Outlet 12. Induced Draft Fan 13. Pyrolysis Dry Gas Outlet 14. Pyrolysis Dry Gas Heat Exchanger 15. Waste Heat Boiler 16. Flue Gas Outlet 17. Heat Carrier Return Feeder 18. Riser Heating Regenerator 19. Gas Distributor 20. Inlet Pipe 21. Ash Discharge Port 22. First-Stage Gas-Solid Separator 23. First-Stage Solid Heat Carrier Return Feeder 24. Second-Stage Gas-Solid Separator 25. Hot Ash Recirculation Return Feeder 26. Pressurized Fan

[0018] The process characteristics of the present invention are described in detail below with reference to the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0019] The invention relates to a process for producing oil products by dual-carrier cycle rapid pyrolysis of waste plastics. The waste plastics are first crushed by a waste plastic crusher (1). Then, the waste plastic fragments with a size of 0 to 30 mm are fed into a water-cooled feed pipe with a water-cooled jacket on the top of a dual-heat carrier descending pyrolysis reactor (5) by a controllable feeder (2). The waste plastic fragments are carried by pyrolysis dry gas and flow downward into a high-temperature gas melting section (4) of the dual-heat carrier descending pyrolysis reactor (5). The high-temperature pyrolysis dry gas of 300°C to 600°C, which is pressurized by a pressurized fan (26) and a pyrolysis dry gas heat exchanger (14), is injected into the high-temperature pyrolysis dry gas inner jacket. The opening rate is 0.1%-15% of the waste plastic fragments are uniformly sprayed out from the porous plate, heating and melting the waste plastic fragments while preventing the plastic fragments from adhering to the inner wall of the dual heat carrier downward pyrolysis reactor (5) to form coke; the mixed pyrolysis dry gas carries the waste plastic melt and flows downward to the high-temperature gas hot melting section (4) at the upper part of the dual heat carrier downward pyrolysis reactor (5), collides and mixes with the first-level solid heat carrier that enters obliquely from the side, and a pyrolysis reaction occurs; the downward-flowing pyrolysis gas, heat carrier and waste plastic melt pass through the mixing internal component composed of the inner cavity guide plate of the dual heat carrier downward pyrolysis reactor (5) for multiple intensified mixing and pyrolysis reactions, and then flows out of the moving bed reactor (6 ) flows into the moving bed reactor (6) on one side of the top, and the vapor and solid are initially separated; the separated heat carrier containing the waste plastic melt further undergoes a pyrolysis reaction in the moving bed, and the pyrolysis oil and gas are further separated and purified through the oil and gas separator (7) and then flow into the fractionation tower (8); the pyrolysis oil and gas are separated into wax oil, diesel, gasoline and pyrolysis dry gas in the fractionation tower (8); an induced draft fan (12) is set at the pyrolysis dry gas outlet on the top of the fractionation tower (8), one path of dry gas is connected to the water-cooled feed pipe (3) as a carrying air, and the other path of dry gas is pressurized and heated by the pressurized fan (26) and the pyrolysis dry gas heat exchanger (14) and then returns to the dual heat carrier downward heat exchanger The high-temperature pyrolysis dry gas inner jacket and the remaining dry gas of the high-temperature gas hot melt section (4) at the top of the decomposition reactor (5) are sent out as products; the coke-containing heat carrier at the bottom of the moving bed reactor (6) is added to the turbulent bed at the bottom of the riser heating regenerator (18) through the heat carrier return device (17) to be generated, and is fluidized and burned by the air added through the air inlet pipe (20) and the gas distributor (19); the generated flue gas and the heat carrier carried are further burned and heated by the carrying bed at the top of the riser heating regenerator (18), and are separated into large and medium particles by the first-stage gas-solid separator (22) at the top of the riser heating regenerator (18). The heat carrier is then separated into fine ash by the second-stage gas-solid separator (24). The flue gas is discharged after the heat is recovered through the pyrolysis dry gas heat exchanger (14) and the waste heat boiler (15). The large and medium-sized heat carrier separated by the first-stage gas-solid separator (22) is circulated back to the solid heat carrier inlet at the top of the dual-heat carrier descending pyrolysis reactor (5) through the first-stage solid heat carrier return feeder (23) to participate in the rapid pyrolysis of waste plastics. The fine ash separated by the second-stage gas-solid separator (24) is circulated back to the turbulent bed at the bottom of the riser heating regenerator (18) through the hot ash circulation pipe and the hot ash circulation return feeder (25) to maintain fluidized combustion.

[0020] The top of the dual heat carrier descending pyrolysis reactor (5) is provided with a feed pipe with a water-cooling jacket, the size of which is 0-100 mm smaller than the reactor cavity; the upper part of the reactor is provided with a high-temperature pyrolysis dry gas inner jacket with a thickness of 10 mm-100 mm formed by the inner cavity and a porous plate with an opening rate of 0.1%-15%, and the jacket height is 0.5-4 times the equivalent diameter of the inner cavity; the side of the upper part of the reactor is provided with an inclined solid heat carrier inlet, which is located 100-1500 mm downward from the top of the reactor and has a horizontal angle of 45°-85°; the inner cavity of the reactor is provided with a mixed internal component consisting of 1-10 guide plates with a horizontal inclination of 25°-85°, and adjacent guide plates are staggered at 180°, and the distance between the bottom end of the guide plate and the inner cavity wall is 100-400 mm.

[0021] The controllable feeder (2) is a rotary feeder, a double-shaft screw feeder or a single-shaft screw feeder.

[0022] The equivalent diameter of the upper portion of the moving bed reactor (6) is 1.2-4.0 times greater than that of the dual-heat carrier descending pyrolysis reactor (5). The outlet and the oil and gas outlet of the dual-heat carrier descending pyrolysis reactor (5) are respectively installed on both sides of the top of the moving bed reactor (6); the bottom of the moving bed reactor (6) is conical and directly connected to the heat carrier return device (17) to be generated with a crushing function.

[0023] The riser heating regenerator (18) is composed of a turbulent fluidized bed at the bottom and a carrying reactor at the top. The turbulent fluidized bed has a larger equivalent diameter and the carrying reactor has a smaller equivalent diameter, with a diameter ratio of 2 to 3:1. The carrying 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.

[0024] The outlet temperature of the dual heat carrier descending pyrolysis reactor (5) is 400-600°C; the reaction temperature at the bottom of the riser heating regenerator (18) is 600-1000°C, and the reaction temperature at the top outlet is 650-1200°C.

[0025] The process of producing oil-chemical products by rapid pyrolysis of waste plastics with dual carrier circulation can continuously and efficiently pyrolyze waste plastics on a large scale. It solves the four common problems in the industry: adhesion and coking of waste plastic feed, difficulty in mixing with heat carriers, low yield of liquid products, and difficulty in scaling up pyrolysis equipment. The liquid yield is over 88% (including liquefied gas), which is more than 15 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 equipment.

Claims

1. The process of producing oil products by dual-carrier rapid pyrolysis of waste plastics is characterized by The waste plastics are first crushed by a waste plastic crusher, and then the waste plastic fragments of 0-30mm are added to the water-cooled feed pipe with a water-cooled jacket on the top of the dual heat carrier descending pyrolysis reactor through a controllable feeder, and flow downward into the high-temperature gas hot melting section of the dual heat carrier descending pyrolysis reactor under the influence of pyrolysis dry gas; the 300℃-600℃ pyrolysis dry gas pressurized by the pressurized fan and the pyrolysis dry gas heat exchanger is injected into the high-temperature pyrolysis dry gas inner jacket, and is evenly sprayed out from the porous plate with an opening rate of 0.1%-15%, heating and melting the waste plastic fragments while preventing the plastic fragments from adhering to the inner wall of the dual heat carrier descending pyrolysis reactor to form coke; the mixed pyrolysis dry gas carries The waste plastic melt flows downward to the high-temperature gas hot melt section at the top of the dual heat carrier descending pyrolysis reactor, collides and mixes with the primary solid heat carrier that enters obliquely from the side, and a pyrolysis reaction occurs; the downward-flowing pyrolysis gas, heat carrier and waste plastic melt pass through the mixing internal components composed of the inner cavity guide plates of the dual heat carrier descending pyrolysis reactor for multiple enhanced mixing and pyrolysis reactions, and then flow into the moving bed reactor from one side of the top of the moving bed reactor for preliminary gas-solid separation; the separated heat carrier containing the waste plastic melt further undergoes a pyrolysis reaction in the moving bed, and the pyrolysis oil vapor is further separated and purified by the oil-gas separator and then flows into the fractionating tower; the pyrolysis oil vapor is separated and purified by the oil-gas separator and then flows into the fractionating tower; The pyrolysis dry gas is separated into wax oil, diesel, gasoline and pyrolysis dry gas in the distillation tower; an induced draft fan is set at the pyrolysis dry gas outlet on the top of the distillation tower, one dry gas is connected to the water-cooled feed pipe as carrying air, and the other dry gas is pressurized and heated by the pressurized fan and the pyrolysis dry gas heat exchanger and then returns to the high-temperature pyrolysis dry gas inner jacket of the high-temperature gas hot melt section at the top of the dual heat carrier descending pyrolysis reactor, and the remaining dry gas is sent out as the product; the char-containing heat carrier at the bottom of the moving bed reactor is added to the turbulent bed at the bottom of the riser heating regenerator through the return device of the heat carrier to be generated, and is fluidized and burned by the air added through the air inlet pipe and the gas distributor; the generated flue gas and the carried heat carrier to be generated are heated and regenerated by the riser The entrained bed at the top of the regenerator is further burned and heated, and the large and medium-sized particle heat carriers are separated by the first-stage gas-solid separator at the top of the riser heating regenerator, and then the fine ash is separated by the second-stage gas-solid separator. After the flue gas recovers heat through the pyrolysis dry gas heat exchanger and the waste heat boiler, the flue gas is discharged; the large and medium-sized particle heat carriers separated by the first-stage gas-solid separator are circulated back to the solid heat carrier inlet at the top of the dual heat carrier descending pyrolysis reactor through the first-stage solid heat carrier return feeder to participate in the rapid pyrolysis of waste plastics; the fine ash separated by the second-stage gas-solid separator is circulated back to the turbulent bed at the bottom of the riser heating regenerator through the hot ash circulation pipe and the hot ash circulation return feeder to maintain fluidized combustion.

2. The process for producing oil products by dual-carrier cyclic rapid pyrolysis of waste plastics according to claim 1 is characterized in that A feed pipe with a water-cooled jacket is provided at the top of the dual-heat-carrier downward pyrolysis reactor, the size of which is 0-100 mm smaller than the reactor inner cavity. A high-temperature pyrolysis dry gas inner jacket with a thickness of 10 mm to 100 mm is formed at the upper part of the reactor by the inner cavity and a porous plate with an opening rate of 0.1% to 15%. The jacket height is 0.5 to 4 times the equivalent diameter of the inner cavity. An inclined solid heat carrier inlet is provided on the side of the upper part of the reactor, located 100 to 1500 mm downward from the top of the reactor and at a horizontal downward angle of 0 to 85 degrees. The reactor inner cavity is provided with a mixed internal component consisting of 1 to 10 guide plates with a horizontal downward inclination of 25 to 85 degrees. Adjacent guide plates are staggered at 180 degrees, and the distance between the bottom end of the guide plate and the opposite inner cavity wall is 100 to 400 mm.

3. The process for producing oil products by dual-carrier cyclic rapid pyrolysis of waste plastics according to claim 1 is characterized in that The controllable feeder is a rotary feeder, a double-shaft screw feeder or a single-shaft screw feeder.

4. The process for producing oil products by dual-carrier cyclic rapid pyrolysis of waste plastics according to claim 1 is characterized in that The riser heating regenerator consists of a turbulent fluidized bed at the bottom and an entrained reactor at the top. 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 composed of large and small straight pipes with diameters of different multiples of the equivalent diameter connected by large and small head pipe fittings, and the diameter ratio of the large and small straight pipes is 1.2~2:1; the equivalent diameter of the fluidized bed is 10%-50% of the equivalent diameter of the turbulent fluidized bed.

5. The process for producing oil products by dual-carrier cyclic rapid pyrolysis of waste plastics according to claim 1 is characterized in that The outlet temperature of the dual heat carrier descending pyrolysis reactor (5) is 400-600°C; the reaction temperature at the bottom of the riser heating regenerator (18) is 600-1000°C, and the reaction temperature at the top outlet is 650-1200°C.

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