Method and device for hydrotreating waste plastics in a slurry of poor quality oil

Abstract

The application discloses a method and device for slurry bed hydroprocessing of waste plastics by using inferior oil, and the method comprises the following steps: S1, the inferior oil is mixed with hydrogen and preheated, and then is transported to a slurry bed reactor for reaction, and the product is subjected to gas-liquid separation by using a hot high-pressure separator to obtain a gas phase component and a liquid phase component; S2, the gas phase component is mixed with waste plastics, and the waste plastics are subjected to thermal cracking by using gas phase waste heat, gas phase products in the thermal cracking products are collected after being washed by water, the liquid phase products are mixed with the liquid phase component in the step S1, and are subjected to fractionation in a fractionation device to obtain a light fraction and a heavy fraction, the heavy fraction is separated again by using a centrifugal separation device to obtain a lower heavy component and an upper light component, the heavy component is recycled to the slurry bed reactor for reaction, and the light fraction and the light component are products obtained after treatment.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology, specifically relating to a method and apparatus for hydrogenating waste plastics using a slurry bed of inferior oil. Background Technology

[0002] Plastic is one of humanity's major inventions of the 20th century. With the rise of the plastics industry in the mid-20th century, humanity entered the plastics era. The application of plastic products has permeated every corner of society, from industrial production to clothing, food, housing, and transportation; plastic products are ubiquitous. The rapid development of the plastics industry has also brought about a series of social problems caused by discarded and waste plastics, which are undesirable to people. Every year, countries around the world accumulate large amounts of waste plastic, placing enormous environmental pressure on human society.

[0003] Slurry bed hydrocracking is one of the ideal methods to achieve the lightening of heavy oil. The use of heavy oil slurry bed hydrocracking technology is a suitable process technology that is technically and economically feasible and conforms to the development trend of improving resource utilization.

[0004] The amount of waste plastics is increasing year by year, which has seriously affected the safety of my country's atmosphere, soil, and water resources. Traditional methods of treating waste plastics, such as landfill and incineration, bring about environmental problems. Waste plastic pyrolysis technology can turn "waste" into "treasure," with good environmental optimization effects and socio-economic benefits.

[0005] In response to the pain points and difficulties encountered in the utilization or treatment of plastics, there is an urgent need to develop a slurry bed process for the thermal pyrolysis of waste plastics.

[0006] Chinese patent CN101074385A describes a continuous pyrolysis process and equipment for waste plastics. It utilizes a solid heat carrier that mixes with and moves in the same direction as the raw material within the pyrolyzer to heat the material, achieving continuous pyrolysis. The pyrolysis temperature is 380-500℃, and the amount of heat-conducting balls added is approximately 40 times the amount of waste plastic. These heat-conducting balls require continuous recycling and regeneration. The pyrolysis gas needs to undergo secondary pyrolysis, cooling, and fractionation in a fixed bed to obtain gasoline and diesel. The recycling and carbon burning regeneration of a large number of high-temperature heat-conducting balls results in a complex production unit structure, high energy consumption, difficult operation, and a large volume of waste gas and solid waste emissions.

[0007] Patent CN102260515A describes a waste plastic pyrolysis treatment device, in which the reactor contains a low-melting-point metal or salt that can be heated to a molten state. The metal or salt is lead, potassium chloride, sodium chloride, or a mixture thereof; the feeding device presses the waste plastic into the molten metal or salt. Because the density of plastic differs significantly from that of the metal or molten salt, uniform mixing and contact between the two at high temperatures will be difficult.

[0008] Patent CN109355099A discloses a method for co-processing solid waste and coal tar to produce fuel oil. First, the light components of coal tar are treated to extract phenols. Then, the heavy distillate of coal tar is pre-hydrogenated to promote the conversion of gums and asphaltenes in the heavy distillate into partially hydrogenated polycyclic aromatic hydrocarbons, improving the hydrogen supply performance of the heavy distillate. Finally, the liquid products from different distillation ranges in the hydrotreating separator are mixed with solid waste and fed into a co-processing reactor to obtain gasoline, diesel, and phenolic products, thus achieving the co-processing of solid waste and coal. This invention combines the processes of phenol extraction from coal tar, hydrotreating heavy distillates, and co-processing solid waste, providing a large amount of solvent oil with good hydrogen supply performance for the liquefaction of solid waste. It realizes the molecular utilization of coal tar and the large-scale, clean, and efficient utilization of solid waste, significantly improving the conversion efficiency of coal tar and solid waste. It has advantages such as low hydrogen consumption, high oil yield, good economic benefits, and suitability for long-term, large-scale operation of the equipment. However, the process flow is relatively complex. Summary of the Invention

[0009] The purpose of this invention is to provide a method and apparatus for hydrogenating waste plastics in a low-quality oil slurry bed, so as to solve the problems of easy coking and complex equipment and processes in the prior art.

[0010] To achieve the above objectives, the present invention provides a method for hydrogenating waste plastics using a low-quality oil slurry bed, comprising the following steps:

[0011] S1, inferior oil is mixed with hydrogen, preheated and then transported to a slurry bed reactor for reaction. The product is separated into gas phase and liquid phase components by a hot high-pressure separator.

[0012] S2, the gaseous component is mixed with waste plastic and the waste plastic is thermally pyrolyzed using the waste heat of the gas phase. The gaseous product in the pyrolysis product is collected and discharged after being washed with water. The liquid product is mixed with the liquid component in step S1 and fractionated in a fractionating device to obtain light and heavy fractions. The heavy fraction is separated again by a centrifugal separator to obtain the lower heavy component and the upper light component. The heavy component is recycled to a slurry bed reactor for reaction. The light fraction and light component are the products obtained after treatment.

[0013] The method for hydrogenating waste plastics using inferior oil in a slurry bed reactor, as described in this invention, involves a reaction temperature of 440-480℃, a reaction pressure of 8-20 MPa, and a liquid hourly space velocity of 0.3-1.0 h⁻¹. -1 The hydrogen-to-oil ratio is 600-1000.

[0014] The method for hydrogenating waste plastics in a slurry bed of inferior oil according to the present invention has a reaction temperature of 440-480℃ and a reaction pressure of 8-20MPa in the hot high-pressure separator.

[0015] The method for hydrogenating waste plastics using inferior oil slurry bed according to the present invention has a thermal cracking reaction temperature of 420-500℃ and a reaction pressure of 8-20MPa in step S2.

[0016] In the method for hydrogenating waste plastics in a slurry bed of inferior oil according to the present invention, the mass ratio of waste plastics to gas phase components added in the thermal cracking reaction in step S2 is between 1:5 and 1:10.

[0017] In the method for processing waste plastics by hydrogenation of inferior oil slurry bed according to the present invention, during fractionation in step S2, the cutting temperature is 400-420℃, the top temperature of the fractionation column is 150-180℃, the bottom temperature is 380-420℃, and the top pressure is 0.05-0.2 MPa.

[0018] The method for hydrogenating waste plastics using inferior oil in a slurry bed according to the present invention, wherein the inferior oil is at least one of coal tar, catalytic slurry oil, high-sulfur and high-metal residue oil, atmospheric residue oil, vacuum residue oil, extra-thick heavy crude oil, and oil sands asphalt.

[0019] The method for hydrogenating waste plastics using inferior oil in a slurry bed according to the present invention requires the addition of an oil-soluble catalyst with hydrogenation function in step S1 when the reaction is carried out in the slurry bed reactor. The active component of the oil-soluble catalyst is one or more of Mu, Ni, Co and Fe, and the catalyst concentration is 10-1000 ppm based on metal content.

[0020] The present invention describes a method for hydrogenating waste plastics using a slurry bed in a low-quality oil medium. The waste plastics are pretreated by crushing, screening, and metal removal. The source and type of waste plastics are not specifically limited; for example, they can be one or more of polyethylene (PE), polypropylene (PP), polystyrene (PS), polystyrene foam (PSF), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polyurethane (PU), and ABS plastics.

[0021] To achieve the above objectives, the present invention also provides an apparatus for the hydrogenation of waste plastics using low-quality oil in a slurry bed, comprising a low-quality oil feeding system, a slurry bed reactor, a high-pressure thermal separator, a waste plastic pyrolysis furnace, a gas-liquid separation device, a fractionation device, a separation device, and a product tank; the low-quality oil feeding system includes a raw material tank, a raw material pump, and a preheater connected in sequence; the inlet of the slurry bed reactor is connected to the outlet of the preheater, and the outlet of the slurry bed reactor is connected to the inlet of the high-pressure thermal separator; the high-pressure thermal separator is equipped with a gas phase component pipeline and a liquid phase component pipeline, and the gas phase component pipeline is connected to the inlet of the waste plastic pyrolysis furnace. The outlet of the waste plastic pyrolysis furnace is connected to the inlet of the gas-liquid separation device. The gas-liquid separation device is equipped with a gas phase pipeline and a liquid phase pipeline. The liquid phase pipeline is connected to the inlet of the fractionation device. The inlet of the fractionation device is also connected to the liquid phase component pipeline. The fractionation device includes a top outlet and a bottom outlet. The top outlet is connected to the product tank, and the bottom outlet is connected to the separation device. The separation device is equipped with a heavy component pipeline and a light component pipeline. The heavy distillate pipeline is connected to the inferior oil feed system or directly to the slurry bed reactor, and the light distillate pipeline is connected to the product tank.

[0022] Beneficial effects of this invention:

[0023] 1. While processing low-quality heavy oil using a slurry bed process, the waste heat from the gas phase separated by a thermal high-pressure separator is used to process waste plastics. Thermal pyrolysis requires high temperature and pressure, but this invention can process waste plastics while saving energy, increasing liquid product yield, and achieving the goals of environmental protection and recycling waste plastic resources.

[0024] 2. A gas-liquid separation unit and a fractionation unit are installed after the waste plastic pyrolysis furnace to fractionate the oil produced by pyrolysis and the liquid oil from the high-pressure thermal separator. The heavier fraction is recycled to the slurry bed reactor for further feeding via a downstream separation unit, while the lighter fraction is stored in a product tank or used in subsequent processes. This improves oil conversion rate while reducing catalyst consumption. Simultaneously, the separation unit effectively extends the operating cycle of the entire unit without clogging, ensuring stable reaction operation. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the apparatus for hydrogenating waste plastics in a low-quality oil slurry bed according to the present invention.

[0026] In the attached figures, the following labels are used:

[0027] 1. Raw material tank; 2. Raw material pump; 3. Preheater; 4. Slurry bed reactor; 5. High-pressure thermal separator; 6. Waste plastic pyrolysis furnace; 7. Gas-liquid separation device; 8. Fractionation device; 9. Separation device; 10. Product tank. Detailed Implementation

[0028] The present invention will now be described in detail through embodiments. It should be noted that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0029] Please refer to Figure 1 This invention provides an apparatus for hydrogenating waste plastics using a slurry bed reactor with low-quality oil. The apparatus includes a raw material tank 1 connected to a raw material pump 2, which pumps the material from the tank into a slurry bed reactor 4. This invention does not specifically limit the types of the raw material tank 1 and the pump 2; the pump 2 can be a volumetric plunger pump. The pump 2 is connected to a preheater 3, which is connected to the slurry bed reactor 4. The slurry bed reactor 4 has a discharge port at its top, which can be an arc-shaped side discharge port to ensure smooth discharge. The slurry bed reactor 4 also has a feed inlet at its bottom, which can be a conical inlet to prevent material accumulation. However, this invention does not specifically limit the shape of the discharge and feed inlets of the slurry bed reactor; in other embodiments, different shapes can be used depending on actual production needs. The preheater 3 is connected to the bottom feed inlet of the slurry bed reactor 4. This invention preferably uses an empty-tank slurry bed reactor to reduce coking and clogging. The outlet of the slurry bed reactor 4 is connected to a thermal high-pressure separator 5. The thermal high-pressure separator 5 is equipped with gas phase component pipelines and liquid phase component pipelines. The gas phase component pipelines are connected to a waste plastic pyrolysis furnace 6. The waste plastic pyrolysis furnace 6 is connected to a gas-liquid separation device 7. The gas-liquid separation device 7 is equipped with gas phase pipelines and liquid phase pipelines. The liquid phase pipelines are connected to a fractionation device 8. The fractionation device 8 is also connected to the thermal high-pressure separator 5 through the liquid phase component pipelines. The fractionation device 8 includes a top outlet and a bottom outlet. The top outlet is connected to a product tank 10, and the bottom outlet is connected to a separator 9. The separator 9 is equipped with heavy component pipelines and light component pipelines. The heavy component pipeline is connected to the feed pump 2 and, after mixing with inferior oil, re-enters the slurry bed reactor 4. In another embodiment, the heavy component pipeline can also be directly connected to the slurry bed reactor 4 as an independent feed system; the light component pipeline is connected to the product tank 10.

[0030] The separator 9 can be a combination of one or more separation devices such as a hot high-pressure separator, a hot low-pressure separator, a cold high-pressure separator, a cold low-pressure separator, a hydrocyclone separator, a flash distillation tower, an atmospheric distillation tower, a vacuum distillation tower, and an extraction tower. Preferably, the device described in this invention is a hot high-pressure separator.

[0031] The fractionation apparatus 8 can be a combination of one or more separation devices such as a hot high-pressure separator, a hot low-pressure separator, a cold high-pressure separator, a cold low-pressure separator, a cyclone separator, a flash distillation tower, an atmospheric distillation tower, a vacuum distillation tower, and a distillation tower. Preferably, the apparatus described in this invention is an atmospheric distillation tower.

[0032] The present invention is further illustrated by the following embodiments, but the following embodiments do not limit the scope of protection claimed by the present invention.

[0033] Examples 1-3

[0034] Examples 1-3 employ the following methods: Figure 1 The process flow shown is as follows: after hydrogen and raw materials are preheated in preheater 3, they are fed into slurry bed reactor 4 for reaction. The resulting product is separated into gas and liquid by thermal high-pressure separator 5. The liquid phase after gas-liquid separation enters fractionation unit 8, and the gas phase after gas-liquid separation enters waste plastic pyrolysis furnace 6. The waste plastic (added in a certain proportion to the gas phase material) undergoes pyrolysis reaction using the residual heat of the gas phase and after crushing, screening and metal removal pretreatment. After the reaction, it enters gas-liquid separation unit 7. The gas phase after pyrolysis reaction can be discharged or collected for subsequent processes after being washed with water in the gas-liquid separation unit. The liquid phase oil after the reaction enters fractionation unit 8. The liquid phase from thermal high-pressure separator 5 and the liquid phase from gas-liquid separation unit 7 are fractionated by fractionation unit 8. The light fraction obtained by fractionation enters product tank 10, and the heavy fraction is separated into two materials by separation unit 9. The light oil enters product tank 10 for storage or for subsequent processes, and the heavier oil is recycled to the feed unit to form a reaction feed with fresh raw materials.

[0035] The properties of the feedstock oils used are shown in Table 1, and the process operating conditions are shown in Table 2.

[0036] Table 1. Properties of vacuum residue

[0037]

[0038]

[0039] Table 2. Process conditions for the examples

[0040]

[0041]

[0042] Table 3. Evaluation Results of Examples

[0043]

[0044]

[0045] As can be seen from the operation of the embodiments, the method of the present invention has a high conversion rate, low toluene insoluble content, realizes the resource utilization of waste, and reduces the overall energy consumption of the device by using gas phase waste heat pyrolysis. Furthermore, as the pressure decreases, the conversion rate and liquid product yield also increase further.

[0046] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for hydrogenating waste plastics using a low-quality oil slurry bed, characterized in that, Includes the following steps: S1, inferior oil is mixed with hydrogen, preheated and then transported to a slurry bed reactor for reaction. The product is separated into gas phase and liquid phase components by a hot high-pressure separator. S2, the gaseous components are mixed with waste plastics and the waste plastics are thermally pyrolyzed using the waste heat of the gas phase. The gaseous products in the pyrolysis products are collected and discharged after being washed with water. The liquid products are mixed with the liquid components in step S1 and fractionated in a fractionating device to obtain light and heavy fractions. The heavy fraction is separated again by a centrifugal separator to obtain the lower layer heavy components and the upper layer light components. The heavy components are recycled to a slurry bed reactor for reaction. The light fraction and light components are the products obtained after treatment.

2. The method for hydrogenating waste plastics using a slurry bed of inferior oil according to claim 1, characterized in that, The reaction temperature in the slurry bed reactor is 440-480℃, the reaction pressure is 8-20 MPa, and the liquid hourly space velocity is 0.3-1.0 h⁻¹. -1 The hydrogen-to-oil ratio is 600-1000.

3. The method for hydrogenating waste plastics using a slurry bed of inferior oil as described in claim 1, characterized in that, The reaction temperature inside the hot high-pressure separator is 440-480℃, and the reaction pressure is 8-20MPa.

4. The method for hydrogenating waste plastics using a slurry bed of inferior oil according to claim 1, characterized in that, In step S2, the thermal decomposition reaction temperature is 420-500℃ and the reaction pressure is 8-20 MPa.

5. The method for hydrogenating waste plastics in a slurry bed of inferior oil according to claim 1, characterized in that, In step S2, the mass ratio of waste plastic to gas phase components added in the thermal decomposition reaction is between 1:5 and 1:

10.

6. The method for hydrogenating waste plastics in a slurry bed of inferior oil according to claim 1, characterized in that, During fractionation in step S2, the cutting temperature is 400~420℃, the top temperature of the fractionation column is 150-180℃, the bottom temperature is 380-420℃, and the top pressure is 0.05-0.2MPa.

7. The method for hydrogenating waste plastics in a slurry bed of inferior oil according to claim 1, characterized in that, The waste plastics are waste plastics that have undergone crushing, screening, and metal removal pretreatment.

8. A device for hydrogenating waste plastics using a low-quality oil slurry bed, characterized in that, The system includes a low-quality oil feeding system, a slurry bed reactor, a high-pressure thermal separator, a waste plastic pyrolysis furnace, a gas-liquid separation unit, a fractionation unit, a separation unit, and a product tank. The low-quality oil feeding system comprises a raw material tank, a raw material pump, and a preheater connected in sequence. The inlet of the slurry bed reactor is connected to the outlet of the preheater, and the outlet of the slurry bed reactor is connected to the inlet of the high-pressure thermal separator. The high-pressure thermal separator is equipped with gas phase component pipelines and liquid phase component pipelines. The gas phase component pipeline is connected to the inlet of the waste plastic pyrolysis furnace, and the outlet of the waste plastic pyrolysis furnace is connected to the gas-liquid separation unit. The gas-liquid separation device has a feed inlet connected to the gas-liquid separation device, which is equipped with a gas phase pipeline and a liquid phase pipeline. The liquid phase pipeline is connected to the feed inlet of the fractionation device, which is also connected to the liquid phase component pipeline. The fractionation device includes a top outlet and a bottom outlet. The top outlet is connected to the product tank, and the bottom outlet is connected to the separation device. The separation device is equipped with a heavy component pipeline and a light component pipeline. The heavy component pipeline is connected to the inferior oil feed system or directly to the slurry bed reactor, and the light component pipeline is connected to the product tank.

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