System and method for completely utilizing waste plastic pyrolysis product

Abstract

A system and a method for completely utilizing waste plastic pyrolysis products relate to the field of comprehensive utilization of waste plastic pyrolysis products, and the method comprises the following steps: S1, pyrolyzing waste plastics to generate pyrolysis gas, pyrolysis oil and pyrolysis carbon; s2, carrying out carbon dioxide capture on the pyrolysis gas obtained in S1 to obtain high-purity carbon dioxide; performing supercritical preparation on the high-purity carbon dioxide to obtain supercritical carbon dioxide fluid; s3, feeding the pyrolytic carbon obtained in the step S1 into a gasification furnace, and converting to obtain synthesis gas; s4, methanol is synthesized through the synthesis gas; s5, distilling the pyrolytic oil obtained in the step S1 to obtain light oil and heavy oil; s6, the light oil is subjected to hydrogenation and fractionation, and naphtha and fuel oil are obtained; s7, heating and cracking the heavy oil and the methanol obtained in the step S4 to obtain a cracking product; and S8, hydrogenating the cracking product obtained in the step S7, and fractionating to obtain naphtha and fuel oil. The problem of circulation of pyrolysis oil as a product is solved, economic maximization of pyrolysis products is achieved, and the method is an important link of chemical circulation of waste plastics.

Description

Technical Field

[0001] The invention belongs to the technical field of comprehensive utilization of waste plastic pyrolysis products, and specifically relates to a system and method for fully utilizing waste plastic pyrolysis products. Background Art

[0002] With the advancement of science and technology and industrial development, plastics are widely used as packaging materials in people's daily lives. Used waste plastics cannot be decomposed by themselves in nature. Only a few types of waste plastics can be reprocessed and reused through specific recycling channels. A large amount of waste plastics enters landfills in the form of domestic garbage. Since waste plastics are not easy to decompose, they occupy a lot of space. Recycling waste plastics quickly and greenly has become an urgent task.

[0003] The green resource treatment of waste plastics is the main research direction at home and abroad. The pyrolysis oil technology of waste plastics can convert waste plastics that cannot be recycled into pyrolysis gas, pyrolysis carbon and petroleum products. There is no secondary pollution in the treatment process. It can not only effectively reduce environmental pollution, but also realize the resource utilization of waste plastics and create considerable benefits. It can provide the final solution for the harmless treatment and resource utilization of waste plastics. It is the main technology for chemical recycling of waste plastics. The pyrolysis oil technology of waste plastics includes thermal cracking, catalytic cracking, thermal cracking-catalytic modification and catalytic cracking-catalytic modification.

[0004] The pyrolysis oil products of waste plastics are divided into pyrolysis gas, pyrolysis carbon and pyrolysis oil. The pyrolysis gas and pyrolysis carbon produced by different plastics have basically the same composition. At present, they are generally burned as pyrolysis fuels. It is worth noting that due to the wide variety of waste plastics, the properties of pyrolysis oils produced by different types of plastics are different. In general, pyrolysis oil is a mixture of alkanes, olefins, and aromatics with a wide distillation range. The presence of olefins causes the instability of pyrolysis oil. Olefins easily react with oxygen and other components in the air, resulting in polymerization reactions to generate colloidal substances. When pyrolysis oil is used as fuel oil, these colloidal substances are easily deposited in filters and distribution lines of engines. Therefore, plastic pyrolysis oil must undergo quality improvement treatments, such as hydrogenation, to reduce the level of olefins. At the same time, pyrolysis oil contains solid impurities, Cl, Si and other polluting elements, which are also undesirable for pyrolysis oil.

[0005] The use of product pyrolysis oil as fuel oil is the main business model for the current chemical recycling of waste plastics. From a higher goal perspective, achieving the recycling of waste plastics into new plastics and reducing the consumption of fossil energy is a more valuable way to recycle waste plastics. To achieve this goal, the pioneering and innovation of plastic pyrolysis oil quality improvement technology is an inevitable requirement. With the development of the waste plastic chemical recycling industry, different routes have been developed and cultivated for the quality improvement of waste plastic pyrolysis oil, and domestic and foreign companies have gradually begun to try to lay out. Summary of the invention

[0006] The technical problem solved by the present application is: to overcome the deficiencies of the prior art, to provide a system and method for comprehensive utilization of waste plastic pyrolysis products, to solve the problem of pyrolysis oil as a product circulation, to achieve economic maximization of pyrolysis products, and to be an important part of the chemical cycle of waste plastics.

[0007] This patent provides a new method for comprehensive utilization of waste plastic pyrolysis products:

[0008] First, the pyrolysis gas is not used directly as fuel. The carbon dioxide content of 10-15% in the pyrolysis gas is captured and used as a carrier in the process of pyrolysis oil upgrading. The remaining pyrolysis gas components are C1-C4 hydrocarbons. Second, the high-temperature pyrolysis carbon is used as the raw material of synthesis gas, and then the synthesized methanol is used as a viscosity reducer, hydrogen donor, etc. in the process of pyrolysis oil upgrading. Third, the pyrolysis oil is upgraded and can eventually be circulated as a product, finally realizing the comprehensive utilization of all pyrolysis products.

[0009] The technical solutions provided by this application are as follows:

[0010] A method for completely utilizing waste plastic pyrolysis products, comprising:

[0011] S1: Pyrolysis of waste plastics produces pyrolysis gas, pyrolysis oil and pyrolysis carbon;

[0012] S2: Capturing carbon dioxide from the pyrolysis gas obtained in S1 to obtain high-purity carbon dioxide; performing supercritical preparation on the high-purity carbon dioxide to obtain supercritical carbon dioxide fluid;

[0013] S3: The pyrolysis carbon obtained in S1 enters the gasifier and is converted into synthesis gas;

[0014] S4: methanol synthesis from syngas;

[0015] S5: distilling the pyrolysis oil obtained in S1 to obtain light oil and heavy oil;

[0016] S6: light oil is hydrogenated and fractionated to obtain naphtha and fuel oil;

[0017] S7: heating and cracking the heavy oil and the methanol obtained in S4 to obtain a cracking product;

[0018] S8: The cracking products of S7 are hydrogenated and fractionated to obtain naphtha and fuel oil.

[0019] The heat source of the heating device in S7 is the supercritical carbon dioxide fluid obtained in S2.

[0020] The supercritical carbon dioxide fluid obtained in S2 has a temperature of 350-420° C. and a pressure of 8-10 MPa.

[0021] In S7, the mass ratio of the heavy oil to be heated and cracked to methanol is 1:1.

[0022] The mixing ratio of the heavy oil to the supercritical carbon dioxide is 1:(1-10) by weight.

[0023] The heavy oil and methanol are mixed and atomized and then enter the heating device for contact heating with supercritical carbon dioxide.

[0024] In S6, the light oil is hydrogenated in a fixed bed hydrogenation reactor; in S8, the cracking product of S7 is hydrogenated in an ebullating bed hydrogenation reactor.

[0025] In S6, the hydrogen-to-oil volume ratio of the hydrogenation reaction is 100-500.

[0026] In the S8, the hydrogenation reaction temperature is greater than 350°C to 400°C, and the pressure is 8-11 MPa.

[0027] A system for completely utilizing pyrolysis products of waste plastics, for carrying out any of the above-mentioned methods for completely utilizing pyrolysis products of waste plastics, comprising: a pyrolysis device, a carbon dioxide absorption tower, a carbon dioxide absorption tower, a supercritical carbon dioxide preparation device, a gasifier, a methanol preparation device, a first fractionation tower, a fixed bed hydrogenation reactor, a second fractionation tower, a heater, a hydrogenation reactor and a third fractionation tower;

[0028] The pyrolysis device is connected to the carbon dioxide absorption tower, the first fractionation tower and the gasifier, the top of the first fractionation tower is connected to the fixed bed hydrogenation reactor and the second fractionation tower in sequence, and the bottom of the first fractionation tower is connected to the heater, the hydrogenation reactor and the third fractionation tower in sequence; the carbon dioxide absorption tower is connected to the carbon dioxide absorption tower and the supercritical carbon dioxide preparation device in sequence, and the output end of the supercritical carbon dioxide preparation device is connected to the heater to provide a heat source for the heater; the gasifier is connected to the methanol preparation device, and the output end of the methanol preparation device is connected to the output end of the bottom of the first fractionation tower;

[0029] The pyrolysis device is used for pyrolysis of waste plastics. The pyrolysis of waste plastics produces pyrolysis gas, pyrolysis oil and pyrolysis carbon. The pyrolysis gas passes through a carbon dioxide absorption tower, a carbon dioxide absorption tower and a supercritical carbon dioxide preparation device in sequence to obtain a supercritical carbon dioxide fluid; the pyrolysis carbon passes through a gasifier and a methanol preparation device in sequence to obtain methanol; the pyrolysis oil enters a first fractionation tower for distillation to obtain a low-boiling light oil and a high-boiling heavy oil, and the light oil enters a fixed-bed hydrogenation reactor and a second fractionation tower in sequence to obtain naphtha and fuel oil; the heavy oil and methanol are mixed and then enter a heater for heating and cracking to obtain cracking products, and the cracking products enter a hydrogenation reactor for catalytic hydrogenation to obtain hydrogenation products, and the hydrogenation products enter a third fractionation tower for fractionation to obtain naphtha and fuel oil

[0030] The pyrolysis gas pipeline coming out of the pyrolysis device is connected to the carbon dioxide absorption tower, and then connected to the carbon dioxide absorption tower and the supercritical carbon dioxide preparation device in sequence;

[0031] The pyrolysis oil pipeline of the pyrolysis device is connected to the first fractionation tower, the heavy oil pipeline fractionated by the fractionation tower is sequentially connected to the heater, the hydrogenation reactor, and the third fractionation tower; the light oil pipeline is sequentially connected to the fixed bed hydrogenation reactor / the second fractionation tower;

[0032] The pyrolysis carbon pipeline of the pyrolysis device is connected in sequence to the gasification furnace / methanol preparation device.

[0033] The raw oil in the heater is a mixture of heavy oil and methanol synthesized by a methanol preparation device, and the heating heat source is supercritical carbon dioxide from a supercritical carbon dioxide preparation device.

[0034] In summary, this application at least includes the following beneficial technical effects:

[0035] (1) The invention uses supercritical carbon dioxide to heat heavy oil, which eliminates the problem of coking in the heating furnace tube. At the same time, the use of supercritical carbon dioxide can be flexibly adjusted by controlling the pressure, and the supercritical material is easy to separate, and the operation process is flexible.

[0036] (2) The invention realizes the comprehensive utilization of pyrolysis products, wherein the carbon dioxide in the pyrolysis gas is captured and used as a heating source for heavy oil upgrading, thereby reducing greenhouse gas emissions. The pyrolysis carbon is gasified to synthesize methanol, which is used as a viscosity reducer and hydrogen donor for heavy oil upgrading. The pyrolysis oil is finally upgraded into naphtha and fuel oil, thereby realizing the circulation of oil products. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A schematic diagram of a method for comprehensive utilization of waste plastic pyrolysis products according to the present invention;

[0038] In the figure: 1. pyrolysis device; 2. carbon dioxide absorption tower; 3. carbon dioxide absorption tower; 4. supercritical carbon dioxide preparation device; 5. gasification furnace; 6. methanol preparation device; 7. first distillation tower; 8. fixed bed hydrogenation reactor; 9. second distillation tower; 10. heater; 11. fluidized bed hydrogenation reactor; 12. third distillation tower. DETAILED DESCRIPTION

[0039] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments disclosed in the present invention will be further described in detail below with reference to the accompanying drawings.

[0040] The present application embodiment discloses a system for comprehensive utilization of waste plastic pyrolysis products, such as Figure 1As shown, it includes a pyrolysis device 1, a carbon dioxide absorption tower 2, a carbon dioxide analysis tower 3, a supercritical carbon dioxide preparation device 4, a gasification furnace 5, a methanol preparation device 6, a first distillation tower 7, a fixed bed hydrogenation reactor 8, a second distillation tower 9, a heater 10, a hydrogenation reactor 11 and a third distillation tower 12.

[0041] In a specific embodiment, the pyrolysis device 1 pyrolyzes waste plastic into pyrolysis gas, pyrolysis oil and pyrolysis carbon. The carbon dioxide absorption tower 2, the carbon dioxide analysis tower 3 and the supercritical carbon dioxide preparation device 4 are used as equipment for purifying the pyrolysis gas and obtaining supercritical carbon dioxide; the gasifier 5 and the methanol preparation device 6 are used to process the pyrolysis carbon and obtain methanol. The first distillation tower 7, the fixed bed hydrogenation reactor 8, the second distillation tower 9, the heater 10, the hydrogenation reactor 11 and the third distillation tower 12 are used as equipment for upgrading the pyrolysis oil, and the supercritical carbon dioxide obtained by purifying the pyrolysis gas and the methanol obtained by processing the pyrolysis carbon are used in the upgrading process.

[0042] In a specific embodiment, pyrolysis gas, one of the pyrolysis products generated by pyrolysis of waste plastics, enters the carbon dioxide absorption tower 2. The pyrolysis gas generally contains 10-15% CO2. After chemical absorption in the carbon dioxide absorption tower 2, the CO2 enters the carbon dioxide analysis tower 3 for analysis to obtain high-purity carbon dioxide. The pyrolysis gas components from which CO2 is removed are low-carbon hydrocarbons of C-C4, which are obtained from the top of the carbon dioxide absorption tower 2. In a specific embodiment, the removal of carbon dioxide from the pyrolysis gas can be carried out in different forms such as membrane separation method and physical capture method, which will not affect the implementation of the entire scheme.

[0043] In a specific embodiment, the high-purity carbon dioxide obtained from the carbon dioxide analysis tower 3 enters the supercritical carbon dioxide preparation device 4. The supercritical preparation device is a conventional and mature equipment, which generally includes a heating system, a pressurizing system, a heat exchange system, a purification system, a control system, etc., and can prepare supercritical carbon dioxide.

[0044] In a specific embodiment, pyrolytic carbon, one of the pyrolysis products generated by pyrolysis of waste plastics, enters the gasifier 5 and reacts with introduced water vapor to obtain synthesis gas, which enters the methanol preparation device 6 and is converted into methanol.

[0045] In a specific embodiment, the pyrolysis oil, one of the pyrolysis products produced by pyrolysis of waste plastics, enters the first fractionation tower 7 for atmospheric distillation to obtain light oil with low boiling point and heavy oil with high boiling point. Generally, the oil in the distillation range of initial boiling point (IBP) to 300°C is taken as light oil, and the oil in the distillation range of 300°C to final boiling point (FBP) is taken as heavy oil. The light oil enters the fixed bed hydrogenation reactor 8 for hydrogenation reaction, and the hydrogenated oil and gas enter the second fractionation tower 9 for separation to obtain non-condensable, naphtha and fuel oil. The hydrogenation reaction conditions of light oil are pressure 3-7MPa, temperature 300-350°C, and hydrogen-oil ratio 100-500.

[0046] In a specific embodiment, the heavy oil in the first fractionation tower 7 is first mixed with methanol from the methanol preparation device 6 to obtain a heavy oil and methanol mixture, the mass ratio of heavy oil to methanol is 1:1, and the heavy oil and methanol mixture enters the upper part of the heater 10 in the form of droplets through an atomizing nozzle. The number of atomizing nozzles is determined according to the processing capacity, which is well known to those skilled in the art and will not be described in detail here. The supercritical carbon dioxide from the supercritical carbon dioxide preparation device 4 enters the heater 10 as a heat source, and the preferred supercritical carbon dioxide has a temperature of 350-420°C and a pressure of 8-10MPa. The mixing ratio of heavy oil and supercritical carbon dioxide is 1:(1-10) by weight. The heavy oil and methanol mixture are heat exchanged with supercritical carbon dioxide, and the oil outlet temperature is controlled at 350-400°C, wherein the heavy oil is partially cracked, enters the ebullated bed hydrogenation reactor 11, and a catalytic hydrogenation reaction is carried out therein. The pyrolysis oil after hydrogenation enters the third fractionation tower 12 for fractionation to obtain non-condensable, naphtha and fuel oil.

[0047] A method for completely utilizing waste plastic pyrolysis products, comprising:

[0048] S1: Pyrolysis of waste plastics produces pyrolysis gas, pyrolysis oil and pyrolysis carbon;

[0049] S2: Capturing carbon dioxide from the pyrolysis gas obtained in S1 to obtain high-purity carbon dioxide; performing supercritical preparation on the high-purity carbon dioxide to obtain supercritical carbon dioxide fluid;

[0050] S3: The pyrolysis carbon obtained in S1 enters the gasifier and is converted into synthesis gas;

[0051] S4: methanol synthesis from syngas;

[0052] S5: distilling the pyrolysis oil obtained in S1 to obtain light oil and heavy oil;

[0053] S6: light oil is hydrogenated and fractionated to obtain naphtha and fuel oil;

[0054] S7: heating and cracking the heavy oil and the methanol obtained in S4 to obtain a cracking product;

[0055] S8: The cracking products of S7 are hydrogenated and fractionated to obtain naphtha and fuel oil.

[0056] The above is a preferred embodiment of the present invention. It should be pointed out that in this field, many technicians can make other extraction schemes through appropriate deformation and improvement on the basis of the present invention. These deformation and improved schemes should also be regarded as the protection scope of the invention.

[0057] The contents not described in detail in this application specification belong to the common knowledge of those skilled in the art.

[0058] The present application is described in detail above in conjunction with specific implementation methods and exemplary examples, but these descriptions cannot be understood as limiting the present application. Those skilled in the art understand that, without departing from the spirit and scope of the present application, a variety of equivalent replacements, modifications or improvements can be made to the technical solution of the present application and its implementation methods, all of which fall within the scope of the present application. The scope of protection of the present application shall be subject to the attached claims.

Claims

1. A method for fully utilizing waste plastic pyrolysis products, characterized in that: include: S1: Pyrolysis of waste plastics produces pyrolysis gas, pyrolysis oil and pyrolysis carbon; S2: Capturing carbon dioxide from the pyrolysis gas obtained in S1 to obtain high-purity carbon dioxide; performing supercritical preparation on the high-purity carbon dioxide to obtain supercritical carbon dioxide fluid; S3: The pyrolysis carbon obtained in S1 enters the gasifier and is converted into synthesis gas; S4: methanol synthesis from syngas; S5: distilling the pyrolysis oil obtained in S1 to obtain light oil and heavy oil; S6: light oil is hydrogenated and fractionated to obtain naphtha and fuel oil; S7: heating and cracking the heavy oil and the methanol obtained in S4 to obtain a cracking product; S8: The cracking products of S7 are hydrogenated and fractionated to obtain naphtha and fuel oil.

2. The method for fully utilizing waste plastic pyrolysis products according to claim 1, characterized in that: The heat source of the heating device in S7 is the supercritical carbon dioxide fluid obtained in S2.

3. The method for fully utilizing waste plastic pyrolysis products according to claim 1, characterized in that: The supercritical carbon dioxide fluid obtained in S2 has a temperature of 350-420° C. and a pressure of 8-10 MPa.

4. The method for completely utilizing waste plastic pyrolysis products according to claim 1, characterized in that: In S7, the mass ratio of the heavy oil to be heated and cracked to methanol is 1:

1.

5. The method for fully utilizing waste plastic pyrolysis products according to claim 1, characterized in that: The mixing ratio of the heavy oil to the supercritical carbon dioxide is 1:(1-10) by weight.

6. The method for completely utilizing waste plastic pyrolysis products according to claim 1, characterized in that: The heavy oil and methanol are mixed and atomized and then enter the heating device for contact heating with supercritical carbon dioxide.

7. The method for completely utilizing waste plastic pyrolysis products according to claim 1, characterized in that: In S6, the light oil is hydrogenated in a fixed bed hydrogenation reactor; in S8, the cracking product of S7 is hydrogenated in an ebullating bed hydrogenation reactor.

8. The method for completely utilizing waste plastic pyrolysis products according to claim 1, characterized in that: In S6, the hydrogen-to-oil volume ratio of the hydrogenation reaction is 100-500.

9. The method for completely utilizing waste plastic pyrolysis products according to claim 1, characterized in that: In the S8, the hydrogenation reaction temperature is greater than 350°C to 400°C, and the pressure is 8-11 MPa.

10. A system for fully utilizing waste plastic pyrolysis products, characterized in that: A method for completely utilizing the pyrolysis products of waste plastics as claimed in any one of claims 1 to 9, comprising: a pyrolysis device (1), a carbon dioxide absorption tower (2), a carbon dioxide absorption tower (3), a supercritical carbon dioxide production device (4), a gasifier (5), a methanol production device (6), a first fractionation tower (7), a fixed bed hydrogenation reactor (8), a second fractionation tower (9), a heater (10), a hydrogenation reactor (11) and a third fractionation tower (12); The pyrolysis device (1) is connected to a carbon dioxide absorption tower (2), a first fractionation tower (7) and a gasifier (5); the top of the first fractionation tower (7) is connected to a fixed bed hydrogenation reactor (8) and a second fractionation tower (9) in sequence; the bottom of the first fractionation tower (7) is connected to a heater (10), a hydrogenation reactor (11) and a third fractionation tower (12) in sequence; the carbon dioxide absorption tower (2) is connected to a carbon dioxide absorption tower (3) and a supercritical carbon dioxide preparation device (4) in sequence, and the output end of the supercritical carbon dioxide preparation device (4) is connected to the heater (10) to provide a heat source for the heater (10); the gasifier (5) is connected to a methanol preparation device (6), and the output end of the methanol preparation device (6) is connected to the output end of the bottom of the first fractionation tower (7); The pyrolysis device (1) is used for pyrolysis of waste plastics. The pyrolysis of waste plastics produces pyrolysis gas, pyrolysis oil and pyrolysis carbon. The pyrolysis gas passes through a carbon dioxide absorption tower (2), a carbon dioxide absorption tower (3) and a supercritical carbon dioxide preparation device (4) in sequence to obtain a supercritical carbon dioxide fluid. The pyrolysis carbon passes through a gasifier (5) and a methanol preparation device (6) in sequence to obtain methanol. The pyrolysis oil enters a first fractionation tower (7) for distillation to obtain a light oil with a low boiling point and a heavy oil with a high boiling point. The light oil enters a fixed bed hydrogenation reactor (8) and a second fractionation tower (9) in sequence to obtain naphtha and fuel oil. The heavy oil and methanol are mixed and then enter a heater (10) for heating and cracking to obtain cracking products. The cracking products enter a hydrogenation reactor (11) for catalytic hydrogenation to obtain hydrogenation products. The hydrogenation products enter a third fractionation tower (12) for fractionation to obtain naphtha and fuel oil.

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