A device for fluidized bed waste plastic graded gasification preparation of chemicals and a method for preparing chemicals thereof

Abstract

This invention belongs to the field of solid waste resource utilization technology. To address the problems of inconsistent temperature during existing fluidized bed waste plastic gasification processes, which prevent graded conversion and result in products primarily consisting of hydrogen and carbon monoxide with low added value and low energy efficiency, this invention provides a device and method for graded gasification of waste plastics to prepare chemicals. The fluidized bed reactor has a top section connected to a silo. The middle section of the reactor is connected to air / oxygen tanks, carbon dioxide tanks, hydrogen tanks, and carbon monoxide tanks. A gas-liquid separator and column chromatography are connected at the top of the reactor, and a liquid pump connects it to a preheater at the bottom. An outlet is located at the bottom. Graded conversion of waste plastics is achieved within the fluidized bed, increasing the added value of the waste plastics and facilitating their graded conversion and high-value utilization. The invention features high production efficiency, continuous production capability, and applicability to other solid waste resource utilization processes.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization technology, specifically relating to an apparatus for preparing chemicals by fluidized bed graded gasification of waste plastics and a method for preparing chemicals. Background Technology

[0002] Fluidized bed gasification is an effective solution and has yielded some significant research results. However, current fluidized bed gasification methods suffer from limitations such as inconsistent temperature, inability to achieve staged conversion of waste plastics, and the resulting products are primarily hydrogen and carbon monoxide, with low added value and low energy efficiency. Furthermore, the design of chemical preparations from staged gasification of waste plastics using fluidized bed gasification remains a gap in research. Summary of the Invention

[0003] To address the problems of inconsistent temperature during existing fluidized bed waste plastic gasification processes, which prevent the achievement of staged conversion and result in products primarily consisting of hydrogen and carbon monoxide with low added value and low energy efficiency, this invention provides an apparatus and method for staged gasification of fluidized bed waste plastics to prepare chemicals. The method employs a three-stage separate gas supply approach to regulate product quality, thereby improving energy efficiency and product added value.

[0004] The present invention is achieved by the following technical solution: a device for preparing chemicals by graded gasification of waste plastics in a fluidized bed, comprising a fluidized bed reactor with a silo connected to the top section, wherein an air / oxygen tank, a carbon dioxide tank, a hydrogen tank, and a carbon monoxide tank are respectively connected inside the fluidized bed reactor; a gas-liquid separator and a chromatography column are connected to the top of the fluidized bed reactor, and the lower part of the fluidized bed reactor is connected to a preheater through a liquid pump; an outlet is provided at the bottom of the fluidized bed reactor.

[0005] A central tube is installed at the center of the fluidized bed reactor. Several oxygen passages are arranged at intervals from top to bottom on the outer wall of the central tube. The central tube is cylindrical, and its diameter is 1 / 40 to 1 / 4 of the diameter of the fluidized bed. The diameter of the oxygen passages is 1 / 20 to 1 / 500 of the diameter of the fluidized bed. The oxygen passages are arranged in concentric circles, triangles or squares, and the opening rate is 1% to 5%.

[0006] The fluidized bed reactor is equipped with baffles, and the baffles are provided with through holes at intervals. The diameter of the through holes is 1 / 20 to 1 / 500 of the diameter of the fluidized bed. The through holes are arranged in concentric circles, triangles or squares, and the opening rate is 1% to 5%.

[0007] The baffle divides the upper region of the fluidized bed reactor into an inverted cone shape. Its top diameter is the same as the diameter of the fluidized bed, and its bottom diameter is 1 / 10 to 1 / 2 of the diameter of the fluidized bed. The through holes on the inverted cone baffle are for gasifying agent.

[0008] The baffle separates the central region of the fluidized bed reactor into a cylindrical gasification zone along the outer side of the central tube. The diameter of the cylindrical gasification zone is the same as the diameter of the cone bottom of the upper region, and the height is 1 / 2 to 1 / 5 of the height of the fluidized bed reactor. The through holes on the baffle of the cylindrical gasification zone are gasification agent through holes.

[0009] The baffle divides the lower part of the fluidized bed reactor into a cone shape, with the top diameter being the same as the diameter of the central cylindrical gasification zone; the through holes on the sides and bottom of the cone baffle are for the gasifying agent.

[0010] A screw feeder is installed between the silo and the fluidized bed reactor.

[0011] The method for preparing chemicals using the aforementioned fluidized bed waste plastic staged gasification apparatus involves waste plastic entering the fluidized bed reactor from the top via a screw feeder from a silo. A metered gasifying agent from a gas holder, along with preheated steam, enters the fluidized bed reactor. The waste plastic reacts from top to bottom with the gasifying agent entering through the central tube and from each side, completing a three-stage depolymerization process. After separation by a gas-liquid separator and chromatography column, high-value-added chemicals are obtained. The temperature of each zone within the fluidized bed reactor is individually controlled.

[0012] The waste plastics are any one or more of polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), polyvinyl chloride (PVC), polyurethane (PU), plastic PC, and polyamide (PA).

[0013] The vaporizing agent is any one or more of air, oxygen, water vapor, carbon dioxide, hydrogen, and carbon monoxide, with a temperature of 323-1273K and a pressure of 0.1-4MPa;

[0014] The ratio of gasifying agent to waste plastic is 1-5 Nm. 3 / kg.

[0015] The high-value-added chemicals produced mainly include olefins, alkanes, and aromatics.

[0016] The gasifying agent enters from the inverted conical side at the top. A flow meter regulates the gas ratio and flow rate, thereby controlling the reaction rate, reaction temperature, and residence time for initial depolymerization of the waste plastics. In the central cylindrical gasification zone, the gasifying agent is added from the side for secondary depolymerization. Gasifying agents are introduced from the bottom conical zone and sides to complete the tertiary depolymerization of the waste plastics. Oxygen is introduced through the central tube to regulate the temperature distribution within the fluidized bed. The size and arrangement of the orifices, as well as the type of gasifying agent, are flexibly adjusted according to the different gasification properties of the waste plastics.

[0017] The gasifying agent reacts with waste plastic at a concentration of 1-5 Nm 3The waste plastic is fed into the upper zone of a fluidized bed reactor at a ratio of [amount] kg / m³ for low-temperature gasification, breaking down the waste plastic into long-chain molecules and gaseous small molecules. The gasification temperature is controlled by the flow rate and ratio of the gasifying agent. This process mainly involves the primary depolymerization of the waste plastic. Subsequently, the waste plastic enters the middle zone, where it undergoes further secondary depolymerization and breakdown under the action of the gasifying agent. The remaining recalcitrant long-chain molecules undergo further depolymerization in the lower zone. Finally, high-value-added chemicals are obtained through a gas-liquid separator and chromatography column. In this process, the waste plastic undergoes a three-stage depolymerization process, enabling the production of chemicals such as aromatics, olefins, and alkanes.

[0018] Fluidized beds possess high heat transfer rates and backmixing capabilities, enabling efficient and continuous conversion of waste plastics. Through segmented gas supply, different gasifying agents and waste plastics can be effectively coupled, achieving graded conversion without the need for physical screening. Furthermore, the size of the upper, middle, and lower gasification zones, the central tube, the conical sidewalls, and the location and size of the openings are controllable, effectively meeting the gasification performance requirements of different waste plastics. This solves the problems of traditional fluidized bed chemical preparation, such as limited composition and low added value, while also avoiding the physical screening process for waste plastics.

[0019] Compared with existing technologies, this invention has the following characteristics: it achieves graded conversion of waste plastics within a fluidized bed, thereby increasing the added value of waste plastics. The size of the upper, middle, and lower gasification zones, the central tube, the conical side surface, and the position and size of the openings are controllable, which is beneficial for the graded conversion and high-value utilization of waste plastics. It has high preparation efficiency, can be continuously produced, and can also be used in other solid waste resource utilization processes. Attached Figure Description

[0020] Figure 1 This is a process flow diagram of the fluidized bed waste plastic preparation of chemicals according to the present invention; Figure 2 This is a diagram of the internal structure of a fluidized bed.

[0021] In the diagram: 1-Air / Oxygen tank; 2-Carbon dioxide tank; 3-Hydrogen tank; 4-Carbon monoxide tank; 5-Valve; 6-Flow meter; 7-Hopper; 8-Fluidized bed reactor; 9-Gas-liquid separator; 10-Preheater; 11-Pump; 12-Chromatography column. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and all materials publicly cited herein and cited by them are incorporated herein by reference.

[0024] Equivalent technologies of the specific embodiments described herein that are readily apparent to those skilled in the art through routine experimentation are included in this application.

[0025] Example 1: An apparatus for preparing chemicals by staged gasification of waste plastics in a fluidized bed, such as... Figure 1 As shown, the fluidized bed reactor 8 includes a top section connected to a material hopper 7. The fluidized bed reactor 8 is connected to an air / oxygen tank 1, a carbon dioxide tank 2, a hydrogen tank 3, and a carbon monoxide tank 4, respectively. The top of the fluidized bed reactor 8 is connected to a gas-liquid separator 9 and a chromatography column 12. The lower part of the fluidized bed reactor 8 is connected to a preheater 10 via a liquid pump 11. An outlet is provided at the bottom of the fluidized bed reactor 8.

[0026] like Figure 2 As shown, a central tube is installed at the center of the fluidized bed reactor 8, and several oxygen passages are spaced from top to bottom on the outer wall of the central tube; the central tube is cylindrical, and its diameter is 1 / 40-1 / 4 of the fluidized bed diameter, while the diameter of the oxygen passages is 1 / 20-1 / 500 of the fluidized bed diameter. The oxygen passages are arranged in concentric circles, triangles, or squares, with an opening rate of 1%-5%.

[0027] The fluidized bed reactor 8 is equipped with baffles, and the baffles are spaced out with through holes. The diameter of the through holes is 1 / 20 to 1 / 500 of the diameter of the fluidized bed. The through holes are arranged in concentric circles, triangles or squares, and the opening rate is 1% to 5%.

[0028] The baffle plate divides the upper region of the fluidized bed reactor 8 into an inverted cone shape. Its top diameter is the same as the fluidized bed diameter, and its bottom diameter is 1 / 10 to 1 / 2 of the fluidized bed diameter. The through holes on the inverted cone baffle plate are for gasifying agent.

[0029] The baffle separates the central area of ​​the fluidized bed reactor 8 into a cylindrical gasification zone along the outer side of the central tube. The diameter of the cylindrical gasification zone is the same as the diameter of the cone bottom of the upper zone, and the height is 1 / 2 to 1 / 5 of the height of the fluidized bed reactor. The through holes on the baffle of the cylindrical gasification zone are gasification agent through holes.

[0030] The baffle plate divides the lower part of the fluidized bed reactor 8 into a cone shape, with the top diameter being the same as the diameter of the central cylindrical gasification zone; the through holes on the sides and bottom of the cone-shaped baffle plate are gasification agent through holes.

[0031] A screw feeder is installed between the silo 7 and the fluidized bed reactor 8.

[0032] The method for preparing chemicals using the aforementioned apparatus involves feeding waste plastics and a gasifying agent into the upper zone of a fluidized bed reactor at a specific ratio for low-temperature gasification. This process breaks down the waste plastics into long-chain molecules and gaseous small molecules. The gasification temperature is controlled by the flow rate of the gasifying agent. This process primarily involves the primary depolymerization of the waste plastics. Subsequently, the waste plastics enter the middle zone, where they undergo further secondary depolymerization and breakdown under the action of the gasifying agent. The remaining recalcitrant long-chain molecules undergo further depolymerization in the lower zone. Finally, the process is carried out by a gas-liquid separator and a chromatography column to obtain high-value-added chemicals. Through this three-stage depolymerization process, waste plastics can be used to produce chemicals such as aromatics, olefins, and alkanes.

[0033] Example 2: Fluidized bed polyethylene (PE) gasification process at atmospheric pressure. The gasification temperatures in the three zones were 473 K in the upper zone, 773 K in the middle zone, and 973 K in the lower zone. Polyethylene was fed into the fluidized bed at a rate of 15 kg / h, and the gasifying agents were oxygen and water vapor at a flow rate of 30 Nm³. 3 The fluidized bed has a flow rate of [number] / h, with segmented gas supply. The inner diameter is 200 mm, and the height is 800 mm. The upper region exhibits an inverted conical shape, with a top diameter of 200 mm, a bottom diameter of 40 mm, and a height of 100 mm. The cone surface has concentric openings with a diameter of 4 mm, resulting in an opening ratio of 2%. The gasifying agents are water vapor and oxygen, each at 2 Nm³. 3 The reaction begins with water vapor entering from the conical side, controlled at a temperature of 473 K and a residence time of 5 s, to initiate the initial depolymerization of polyethylene. A cylindrical vaporization zone with a diameter of 40 mm and a height of 200 mm is positioned in the center. Side openings with a diameter of 4 mm are arranged concentrically, resulting in an opening ratio of 2%. The vaporizing agents are 4 Nm³ of water vapor and 4 Nm³ of oxygen. 3 The reaction is initiated from the side of a cone, with the reaction temperature controlled at 773 K and the residence time at 10 s, for the secondary depolymerization of polyethylene. The bottom region has a cone-shaped distribution, with a top diameter of 40 mm, a bottom diameter of 200 mm, and a height of 500 mm. The cone and bottom surfaces have concentric 4 mm orifices, resulting in an orifice ratio of 2%. 6 Nm³ of vaporizing agent (water vapor) is introduced into the bottom of the cone. 3 / h, 4 Nm³ of vaporizing agent water vapor is introduced from the side. 3 The reaction temperature was controlled at 973 K and the residence time at 20 s per hour to complete the three-stage depolymerization of polyethylene. The central tube was cylindrical with a diameter of 10 mm and side openings with a diameter of 4 mm, arranged concentrically, with an opening ratio of 2%. Oxygen was introduced into the central tube at a flow rate of 8 Nm³. 3 / h is used to adjust the temperature distribution of polyethylene gasification in the fluidized bed. Subsequently, the gaseous product ethylene (30%) is separated by a gas-liquid separator, and the liquid product is separated by a chromatography column with ethyl acetate as the solvent. After chromatography, benzene (50%) and ethanol (20%) are obtained.

[0034] Example 3: Fluidized bed polypropylene (PP) gasification process, pressure 0.3 MPa, gasification temperatures in three zones: upper zone 423 K, middle zone 573 K, and lower zone 673 K. Polypropylene was fed into the fluidized bed at a feed rate of 20 kg / h, and the gasifying agents were oxygen, water vapor, and carbon dioxide at a flow rate of 50 Nm³. 3 The fluidized bed has a flow rate of [number] / h, with segmented gas supply. The inner diameter is 240 mm, and the height is 1000 mm. The upper region exhibits an inverted conical shape, with a top diameter of 240 mm, a bottom diameter of 60 mm, and a height of 200 mm. The cone surface has 2 mm diameter orifices arranged in a triangular pattern, resulting in an orifice rate of 1%. The gasifying agents are water vapor, oxygen, and carbon dioxide, each at 2 Nm³. 3 The reaction begins with a cone-shaped inlet, controlled at a temperature of 423 K and a residence time of 12 s, to initiate the initial depolymerization of polypropylene. A cylindrical vaporization zone with a diameter of 60 mm and a height of 300 mm is positioned in the center. Side openings with a diameter of 2 mm are arranged in a triangular pattern, resulting in an opening ratio of 1%. The vaporizing agents are 4 Nm³ each of water vapor, oxygen, and carbon dioxide. 3 The reaction is initiated from the side of a cone, with the reaction temperature controlled at 573 K and the residence time at 20 s, for the secondary depolymerization of polypropylene. The bottom region has a cone-shaped distribution, with a top diameter of 60 mm, a bottom diameter of 240 mm, and a height of 500 mm. The cone and bottom surfaces have 2 mm diameter openings arranged in a triangular pattern, with an opening ratio of 1%. 4 Nm³ of water vapor and 4 Nm³ of carbon dioxide are introduced into the bottom of the cone. 3 / h, with 8 Nm³ each of water vapor and carbon dioxide as vaporizing agents introduced from the side. 3 The reaction temperature was controlled at 673 K and the residence time at 50 s per hour to complete the three-stage depolymerization of polypropylene. The central tube was cylindrical with a diameter of 20 mm and side openings with a diameter of 2 mm, arranged in a triangular pattern with an opening ratio of 1%. Oxygen was introduced into the central tube at a flow rate of 8 Nm³. 3 / h is used to adjust the temperature distribution of polypropylene gasification in the fluidized bed. Subsequently, liquid aromatics (60%) are obtained through a gas-liquid separator. The gas-phase mixture is separated by a chromatography column using hexane as the solvent. After separation, propylene (15%) and propane (25%) are obtained, etc.

[0035] Example 4: Fluidized bed gasification process of polyethylene terephthalate (PET) at a pressure of 1 MPa. The gasification temperatures in the three zones were 473 K in the upper zone, 573 K in the middle zone, and 673 K in the lower zone. Polypropylene was fed into the fluidized bed at a feed rate of 30 kg / h. The gasifying agents were oxygen, water vapor, and hydrogen, with a flow rate of 90 Nm³. 3The fluidized bed has an inner diameter of 300 mm and a height of 1200 mm per hour. The upper region exhibits an inverted conical shape, with a top diameter of 300 mm, a bottom diameter of 80 mm, and a height of 200 mm. The cone surface has 1.5 mm diameter openings arranged in a square pattern, resulting in an opening ratio of 3%. The gasifying agent, oxygen (2 Nm³), enters from the side of the cone. 3 / h and water vapor 3 Nm 3 The reaction begins at a rate of / h, entering from the conical side, with the reaction temperature controlled at 473 K and the residence time at 20 s, to initiate the initial depolymerization of polyethylene terephthalate. A cylindrical vaporization zone with a diameter of 80 mm and a height of 500 mm is set in the center, with side openings of 1.5 mm diameter arranged in a square pattern, resulting in an opening ratio of 3%. The vaporization agent is 6 Nm³ of oxygen. 3 / h, water vapor 6 Nm 3 / h and hydrogen 8 Nm 3 The reaction mixture is added from the side at a rate of / h, with the reaction temperature controlled at 573 K and the residence time at 35 s, for the secondary depolymerization of polyethylene terephthalate. The bottom region has a conical distribution, with a top diameter of 80 mm, a bottom diameter of 300 mm, and a height of 500 mm. The cone and bottom surfaces have 1.5 mm diameter openings arranged in a square pattern, resulting in an opening rate of 3%. 15 Nm³ each of water vapor and hydrogen gas are introduced into the conical bottom as vaporizing agents. 3 / h, 10Nm each of water vapor and hydrogen gas, acting as vaporizing agents, are introduced from the side. 3 The reaction was carried out at a controlled temperature of 673 K and a residence time of 120 s per hour to complete the three-stage depolymerization of polyethylene terephthalate. The central tube was cylindrical with a diameter of 24 mm and side openings of 1.5 mm diameter arranged in a square pattern, resulting in an opening ratio of 3%. Oxygen was introduced into the central tube at a flow rate of 15 Nm³. 3 / h is used to adjust the temperature distribution of polyethylene terephthalate vaporization in the fluidized bed. Subsequently, liquid terephthalic acid (10%) is obtained by gas-liquid separator (473 K). The gas mixture is separated by chromatography column using ethyl acetate as solvent. After separation, benzene (70%) and ethylene glycol (20%) are obtained.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An apparatus for preparing chemicals by staged gasification of waste plastics in a fluidized bed, characterized in that: The fluidized bed reactor (8) includes a top section connected to a silo (7), and the middle section of the fluidized bed reactor (8) is connected to an air / oxygen tank (1), a carbon dioxide tank (2), a hydrogen tank (3), and a carbon monoxide tank (4); the top of the fluidized bed reactor (8) is connected to a gas-liquid separator (9) and a chromatography column (12), the lower part of the fluidized bed reactor (8) is connected to a preheater (10) through a liquid pump (11), and an outlet is provided at the bottom of the fluidized bed reactor (8); A central tube is installed at the center of the fluidized bed reactor (8), and several air / oxygen through holes are arranged at intervals from top to bottom on the outer wall of the central tube; the central tube is cylindrical, and its diameter is 1 / 40-1 / 4 of the diameter of the fluidized bed. The diameter of the air / oxygen through holes is 1 / 20-1 / 500 of the diameter of the fluidized bed. The air / oxygen through holes are arranged in concentric circles, triangles or squares, and the opening rate is 1%-5%. The fluidized bed reactor (8) is equipped with baffles, and through holes are arranged at intervals on the baffles. The diameter of the through holes is 1 / 20-1 / 500 of the diameter of the fluidized bed. The through holes are arranged in concentric circles, triangles or squares, and the opening rate is 1%-5%. The baffle divides the upper part of the fluidized bed reactor (8) into an inverted cone shape. Its top diameter is the same as the fluidized bed diameter, and its bottom diameter is 1 / 10-1 / 2 of the fluidized bed diameter. The through holes on the inverted cone baffle are gasification agent through holes. The baffle separates the central region of the fluidized bed reactor (8) into a cylindrical gasification zone along the outside of the central tube. The diameter of the cylindrical gasification zone is the same as the diameter of the cone bottom of the upper region, and the height is 1 / 2 to 1 / 5 of the height of the fluidized bed reactor. The through holes on the baffle of the cylindrical gasification zone are gasification agent through holes. The baffle divides the lower part of the fluidized bed reactor (8) into a cone shape, with the top diameter being the same as the diameter of the cylindrical gasification area in the middle; the through holes on the side and bottom of the cone baffle are gasification agent through holes.

2. The apparatus for preparing chemicals by staged gasification of waste plastics in a fluidized bed according to claim 1, characterized in that: A screw feeder is installed between the silo (7) and the fluidized bed reactor (8).

3. A method for preparing chemicals using the apparatus for fluidized bed waste plastic staged gasification as described in claim 1, characterized in that: Waste plastics are fed from the silo into the fluidized bed reactor from the top via a screw feeder. The gasifying agent in the gas holder is metered and then enters the fluidized bed reactor together with preheated steam. The waste plastics react with the gasifying agent entering from the central tube and various sides from top to bottom, completing the three-stage depolymerization process of the waste plastics. After separation by a gas-liquid separator and a chromatography column, high-value-added chemicals are obtained. The temperature of each zone within the fluidized bed reactor is controlled individually. The waste plastics are any one or more of polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), polyvinyl chloride (PVC), polyurethane (PU), plastic PC, and polyamide (PA). The vaporizing agent is any one or more of air, oxygen, water vapor, carbon dioxide, hydrogen, and carbon monoxide, with a temperature of 323-1273K and a pressure of 0.1-4MPa; The ratio of gasifying agent to waste plastic is 1-5 Nm. 3 / kg.

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