CN116023962A - Method and system for pyrolyzing waste plastic tube furnace - Google Patents

Abstract

The invention relates to a method and a system for pyrolyzing a waste plastic tube furnace. Waste plastics enter a waste plastics pretreatment unit, contact with a pretreatment agent and solvent oil for impurity removal treatment, the obtained effluent is subjected to solid-liquid separation to obtain insoluble matters and impurity-removed plastic-containing solution, and the impurity-removed plastic-containing solution is sent into a tubular furnace pyrolysis reactor in a spray form for pyrolysis to obtain pyrolysis oil. The obtained pyrolysis oil has low metal content, chlorine content and silicon content, and effectively reduces the influence of impurities in waste plastics on subsequent treatment units. The invention has the advantages of small pollution discharge, good environmental protection, reduced carbon emission and good environmental benefit, social benefit and economic benefit in the production process.

Description

Method and system for pyrolyzing waste plastic tube furnace

Technical Field

The invention relates to the technical field of solid waste plastic treatment, in particular to a method and a system for pyrolysis of a waste plastic tube furnace.

Background

The development of the plastic industry makes a great contribution to the social development, and the annual plastic production of China is up to about 1.2 hundred million tons at present, and most of the plastic is discarded into the environment after one-time use. According to statistics, the yield of waste plastics in China is about 240-480 ten thousand tons/year; by 2035, about 80 hundred million tons of waste plastics exist in the natural environment, and the continuous accumulation of waste plastics not only causes serious environmental pollution, but even affects the ecological balance in the natural environment because the plastic needs 200 to 500 years to be completely degraded.

The existing waste plastic treatment technology mainly comprises two modes of landfill and incineration, wherein the landfill occupies a large amount of land, is extremely easy to cause secondary pollution and cannot essentially solve the problem; however, at present, only about 400 waste incineration power plants capable of disposing waste plastics exist in China, for example, all waste plastics are solved by adopting a waste incineration power generation mode, and more than 1000 waste plastics are expected to be constructed, which is obviously not feasible. In addition, the physical recovery process of waste plastics has high cost and low economic value, enterprises have insufficient profit and secondary pollution is easy to cause in the recovery process, and the recovery development of waste plastic resources is slower.

The chemical conversion of waste plastics is an effective means for realizing the rapid recovery and conversion of waste plastics, particularly, the thermoplastic waste plastics can obtain oil products and gases through a pyrolysis process, so the pyrolysis process is one of the main process paths of the chemical conversion of the waste plastics at present.

CN106635115B discloses a method for efficiently cleaning and preparing oil by using mixed waste plastic garbage and a hydrothermal reaction system, wherein the method comprises the steps of carrying out thermal hydrolysis treatment on the mixed waste plastic garbage by using an alkaline aqueous solution under the conditions of 160-300 ℃ and 20-220 bar of pressure; the mixed waste plastic garbage contains one or more of Polyethylene (PE), polypropylene (PP) and Polystyrene (PS) and PET, and optionally the mixed waste plastic garbage can also comprise polyvinyl chloride (PVC); separating the water phase from the solid phase in the material after the hydrothermal treatment, and preparing oil from the separated solid phase. The method not only avoids the adverse effect of PET and PVC in the mixed waste plastics on the quality of oil, but also can clean the oil production efficiently, and can produce products with high added value, such as TA powder or particles and PS reclaimed plastics.

CN108456328A discloses a method for treating waste plastics, comprising: waste plastics, a modified catalyst and a reaction solvent are added into a catalytic cracking reactor to be uniformly mixed, and then catalytic cracking reaction is carried out, and the method is characterized in that: the modified catalyst is a modified HZSM-5 and HY composite molecular sieve catalyst modified by a modifier oxide, the modifier is one or more selected from Sn, fe, ti and Zn, the reaction solvent is a mixture of tetrahydronaphthalene and n-hexadecane, and the catalytic cracking reaction conditions are as follows: the reaction temperature is 150-300 ℃, the reaction time is 120-240 minutes, the reaction is carried out under stirring, the stirring speed is 600-1000 rpm, hydrogen is introduced into the reaction, and the hydrogen partial pressure is 4-7MPa.

Due to the complex composition of waste plastics, the waste plastics contain a large number of heteroatoms; a large amount of organic or inorganic various additives can be added in the plastic production process to improve the plastic performance; the pyrolysis process in the prior art mainly has the problems that the quality of pyrolysis oil does not reach the standard due to the fact that a large amount of impurities are easy to adhere in the discarding process of plastics, and the like, and particularly the content of Cl and Si impurities is high. The Cl in the pyrolysis oil mainly comes from PVC decomposition in waste plastics, most of the Cl is micromolecular organic chlorine, and HCl is easily decomposed to form in the subsequent oil processing process, so that serious corrosion is caused. In the prior art, the organic chlorine is converted into HCl and then is neutralized with alkaline substances in a hydrogenation mode aiming at dechlorination of pyrolysis oil, but a large amount of solid waste is generated on the one hand, a large amount of hydrogen resources are consumed on the other hand, and the catalyst cost is increased. Si in the pyrolysis oil mainly comes from the decomposition of high molecular additives such as silicone oil, silicone resin, silicone rubber powder and the like, and inorganic additives such as SiO2 and the like, mainly alkyl epoxy silane, is a poison of a catalyst in a subsequent processing technology, and can cause permanent deactivation of the catalyst.

Therefore, a new waste plastic treatment technology is still needed urgently to solve the problems that in the prior art, the waste plastic pyrolysis oil has high content of harmful elements Cl and Si, so that pipelines and equipment in the subsequent process are easy to corrode and the catalyst is easy to deactivate.

Disclosure of Invention

The invention aims to solve the problems of easy corrosion of pipelines and equipment and easy deactivation of catalysts in the follow-up process caused by high content of harmful elements Cl and Si in waste plastic pyrolysis oil in the prior art. Thereby providing a recycling treatment method and system for waste plastics.

A first aspect of the present invention provides a method of pyrolysis of waste plastic tubing ovens, comprising the steps of:

(1) Waste plastics enter a waste plastics pretreatment unit, contact with a pretreatment agent and solvent oil for impurity removal treatment, and the obtained effluent is subjected to solid-liquid separation to obtain insoluble matters and impurity-removed plastic-containing solution, wherein the metal content of the impurity-removed plastic-containing solution is less than 5 mug/g, the chlorine content is less than 20 mug/g and the silicon content is less than 3 mug/g; the pretreatment agent is one or more selected from humus soil, red mud, dead catalyst of oil refining device, kaolin, semicoke, activated carbon and gasified ash, and optionally alkaline oxide,

(2) The impurity-removed plastic-containing solution is sent into a tubular furnace pyrolysis reactor in a spray mode and pyrolyzed at 400-650 ℃ to obtain pyrolysis oil gas and semicoke; and carrying out oil-gas separation on the obtained pyrolysis oil gas to obtain pyrolysis oil and pyrolysis gas.

In one embodiment of the present invention, the method further comprises step (3):

(3) The insoluble matter obtained in the step (1) enters an extraction unit, contacts with an organic solvent to perform solvent extraction, and the obtained product is separated to obtain a solid phase material and a liquid phase material,

after the obtained solid-phase material is treated by a pretreatment agent recovery unit, at least part of the solid-phase material is used as a circulating pretreatment agent to return to the step (1);

and separating out and separating the liquid phase material in a solvent recovery unit to obtain solid plastic particles and recovered organic solvent.

In the invention, the waste plastic is one or more of waste plastic in fresh household garbage, waste plastic in industrial and agricultural production and waste plastic in aged garbage, and can be one or more of waste plastic rods, waste plastic particles, waste plastic sheets and the like formed by preliminary processing of the waste plastic, preferably poor-quality waste plastic which cannot be physically recycled, and the waste plastic is one or more of PE, PP, PS, PVC.

In one embodiment of the present invention, the waste plastics are washed, dried and crushed before entering the waste plastics pretreatment unit, and the crushed waste plastics have a particle size of 1 to 200mm, preferably 1 to 50mm.

In one embodiment of the present invention, in the step (1), the treatment conditions of the waste plastic pretreatment unit are: the pretreatment temperature is 250-410 ℃, the pressure is 0.1-5 MPa, and the retention time of the waste plastics is 10-60 min. In a preferred case, the treatment conditions of the waste plastic pretreatment unit are: the pretreatment temperature is 280-390 ℃, the pressure is 0.5-4.0 MPa, and the retention time of the waste plastics is 15-45 min.

In one embodiment of the invention, the particle size of the pretreatment agent ranges from 75 to 150 μm; the weight ratio of the pretreatment agent to the waste plastic is 1:10-2:1, preferably 1:7-1:5.

In a preferred embodiment of the present invention, the pretreatment agent is one or more of waste catalytic cracking catalyst, humus soil, semicoke, activated carbon, and optionally alkaline oxide.

In a preferred case, the semicoke is the semicoke obtained in the step (2) of the invention.

In the present invention, "optional" means that the optional component means. In one embodiment of the present invention, the pretreatment agent contains a basic oxide in addition to other components.

In the present invention, the term "humus" refers to a mixture of plant matter and various organic wastes, which is entrained by waste plastics excavated from a landfill, after decay.

In the present invention, the term "semicoke" refers to a solid product generated by pyrolysis of carbonaceous materials such as coal, biomass, waste plastics, etc. at 350-600 ℃.

In the present invention, the term "gasification ash" refers to a solid product remaining after carbonaceous materials such as coal, semicoke, coke, biomass, petroleum coke, waste plastics and the like react with a gasifying agent at a temperature higher than 600 ℃ under normal pressure or under a pressurized condition.

In the present invention, the term "red mud", also called "red mud", refers to industrial solid waste discharged after alumina is refined from bauxite.

In the present invention, the term "solvent oil" has a meaning well known in the art, which is typically a complex mixture of hydrocarbons. Preferably, the "solvent oil" is an aromatic-rich distillate, which may be one of petroleum processing, coal pyrolysis, direct coal liquefaction, biomass and/or waste plastic pyrolysis, or a mixture of more than one thereof.

In one embodiment of the invention, the distillation range of the solvent oil is 80-550 ℃, the total aromatic hydrocarbon content in the solvent oil is higher than 50 mass percent, and the monocyclic aromatic hydrocarbon content is higher than 20 mass percent; in a preferred case, the content of monocyclic aromatic hydrocarbon in the solvent oil is higher than 40 mass%. The weight ratio of the solvent oil to the waste plastic is 1:10-10:1, and in a preferred case, the weight ratio of the solvent oil to the waste plastic is 1:1-7:1.

In the waste plastic pretreatment unit, most plastics are dissolved in solvent oil and subjected to desilication and demetallization reactions under the action of a pretreatment agent. And (3) carrying out solid-liquid separation on the effluent after impurity removal, and separating the effluent into insoluble matters and impurity-removed plastic-containing solution. In the method of the present application, by employing the carefully selected pretreatment agent and solvent oil type, as well as the treatment conditions, the impurity content in the resulting de-contaminated plastic-containing solution can be controlled within a desired range to facilitate subsequent further processing and treatment.

The specific mode of solid-liquid separation is not limited in the present invention, and may be one or more of various types of filters and centrifuges. In one embodiment of the invention, the solid-liquid separation device is provided with a heating and heat preserving device, the heating device is one or more of external heating type and internal heating type, and the operation temperature of the solid-liquid separation is 250-410 ℃. When the solid-liquid separation device is a filter, the pore diameter of the filter screen is 0.1-75 μm, preferably 0.1-10 μm.

In a preferred embodiment of the invention, the resulting de-hybridization plastic-containing solution has a total metal content of less than 5. Mu.g/g, a chlorine content of less than 10. Mu.g/g, and a silicon content of less than 2. Mu.g/g. The silicon impurities are removed in the original form of the organic silicon polymer added in the plastic processing process, so that the influence of the silicon impurities on the catalyst of a subsequent processing unit is effectively avoided.

In one embodiment of the present invention, in step (3), the insoluble material obtained in step (1) enters an extraction unit, and is contacted with an organic solvent to perform solvent extraction, and the obtained product is separated to obtain a solid phase material and a liquid phase material. One or more of a solvent extraction tower and a static mixing extractor are arranged in the extraction unit, the specific operation condition of the extraction unit is matched with the selected organic solvent, the extraction aim is to remove solvent oil adhered on the discharged solid phase material, the total amount of the discharged solid phase material is reduced, and finally the aim of reducing the emission is achieved.

In a preferred case, the organic solvent is selected from one or more of benzene, toluene, chloroform, cyclohexanone, ethyl acetate, butyl acetate, carbon disulfide, tetrahydrofuran and gasoline.

In one embodiment of the invention, the solid phase material obtained by the extraction unit is treated in a pretreatment agent recovery unit, part or all of the solid phase material is returned to the step (1) as a circulating pretreatment agent, and the pretreatment agent recovery unit comprises one or more of screening and regeneration treatment modes.

In one embodiment of the invention, the liquid phase material obtained from the extraction unit is subjected to precipitation treatment and separation in a solvent recovery unit to obtain solid plastic particles and recovered organic solvent. In the solvent recovery unit, the precipitation treatment is one or more selected from back extraction, simple distillation, flash evaporation and rectification. The specific operation temperature is flexibly regulated and controlled according to the types and the proportions of the selected solvents.

In the step (2), the impurity-removed plastic-containing solution is preheated to a certain temperature and is sent into a tubular furnace pyrolysis reactor in a spray mode to carry out pyrolysis reaction, so as to obtain pyrolysis oil gas and semicoke; and carrying out oil-gas separation on the obtained pyrolysis oil gas to obtain pyrolysis oil and pyrolysis gas.

In one embodiment of the invention, the pyrolysis temperature in the tube furnace pyrolysis reactor is 450-550 ℃ and the pyrolysis pressure is 0.1-1 MPa;

the carrier gas of the pyrolysis reactor of the tubular furnace is selected from N ₂ 、H ₂ 、CH ₄ 、CO ₂ One or more of steam, pyrolysis gas, and clean syngas.

The pyrolysis gas obtained in step (2) is preferably used as carrier gas for the tube furnace pyrolysis reactor.

The semicoke obtained in the step (2) is preferably used as the pretreatment agent in the step (1).

In one embodiment of the invention, part of the pyrolysis gas is used as carrier gas for the tube furnace pyrolysis reactor, and the rest of the pyrolysis gas is sent to the combustion heating unit for generating the heat required by the whole process.

In one embodiment of the invention, the semicoke obtained in step (2) is sent to a combustion heating unit for generating the heat required for the whole process.

In one embodiment of the invention, the pyrolysis oil in the step (2) is fractionated to obtain a light fraction and a heavy fraction, and the cutting point is 180-230 ℃;

and (3) recycling the heavy fraction obtained by the pyrolysis oil fractionation to the waste plastic pretreatment unit in the step (1) as solvent oil.

The invention also provides a system for any method, which comprises a waste plastic pretreatment unit, a solid-liquid separation unit and a tubular furnace pyrolysis unit;

the waste plastic pretreatment unit is provided with a waste plastic inlet, a pretreatment agent inlet, a solvent oil inlet and a pretreated material outlet, the pretreated material outlet is communicated with the inlet of the solid-liquid separation unit, and the solid-liquid separation unit is provided with an insoluble matter outlet and a impurity-removing plastic-containing solution outlet;

the tubular furnace pyrolysis unit is provided with a tubular furnace pyrolysis reactor and a pyrolysis product separation system; the pyrolysis product outlet of the tube furnace pyrolysis reactor is communicated with the inlet of the pyrolysis product separation system, and the pyrolysis product separation system is at least provided with a semicoke outlet, a pyrolysis oil outlet and a pyrolysis gas outlet.

In one embodiment of the invention, the waste plastic pretreatment unit can be a one-stage or multistage series or parallel kettle type dissolving device, or a special-shaped dissolving device with dissolving function, or equipment with the same function such as a continuous spiral leacher. Further preferably, a stirring device and a heating device are arranged in the waste plastic pretreatment unit, the stirring device can be driven by electric power or magnetic force and can be one or more of paddle type, anchor type, frame type and spiral type, and the stirring speed of the stirring device can be 1-300r/min, preferably 60-100r/min; the heating means may be one or more of internal heating and/or external heating means. For example, the external heating type heating device can be one or more of a jacket type coil pipe or a semicircular coil pipe, and the internal heating type heating device can be various built-in coil pipes; the heat source can be one or more of electricity, conduction oil, steam and open flame heating.

The present invention is not particularly limited to the specific form of the solid-liquid separation unit, and may be various forms of filters, centrifuges, or combinations thereof. In a preferred embodiment, the solid-liquid separation unit can be one or more of one or more stages of continuous automatic solid-liquid separation equipment with heat preservation function, oil resistance and organic solvent resistance, which are connected in series, or one or more of various types of filters with automatically changeable filter screens, filter presses with scrapers, cross-flow filters, horizontal decanter centrifuges and spiral extrusion desolventizing equipment. Further preferably, the solid-liquid separation unit may be provided with a heating and heat-preserving device, the heating device may be one or more of an external heating type heating device or an internal heating type heating device, the external heating type heating device may be one or more of a jacketed type heating device or a semicircular coil, and the internal heating type heating device may be various built-in coils; the heat source can be one or more of electricity, conduction oil, steam and open flame heating. Preferably, the solid-liquid separation unit may be operated at a temperature of 250-410 ℃. When the solid-liquid separation unit is a filter, the pore diameter of the filter screen can be 0.1-75 μm, preferably 0.1-10 μm.

In one embodiment of the invention, the pretreatment device further comprises an extraction unit, a pretreatment agent recovery unit and a solvent recovery unit;

the extraction unit is provided with an insoluble matter inlet, an organic solvent inlet, a solid phase material outlet and a liquid phase material outlet, and the insoluble matter outlet of the solid-liquid separation unit is communicated with the insoluble matter inlet of the extraction unit;

the pretreatment agent recovery unit is provided with a solid-phase material inlet, a circulating pretreatment agent outlet, the solid-phase material outlet of the extraction unit is communicated with the solid-phase material inlet of the pretreatment agent recovery unit, and the circulating pretreatment agent outlet of the pretreatment agent recovery unit is communicated with the pretreatment agent inlet of the waste plastic pretreatment unit;

the solvent recovery unit is provided with a liquid-phase material inlet, a solid plastic particle outlet and a recovered organic solvent outlet, and the liquid-phase material outlet of the extraction unit is communicated with the liquid-phase material inlet of the solvent recovery unit.

In one embodiment of the invention, one or more of a solvent extraction tower or a static mixing extractor can be arranged in the extraction unit, the specific operation condition of the extraction unit is matched with that of the selected second organic solvent, the extraction aim is to remove solvent oil adhered on the discharged solid phase material, reduce the total amount of the discharged solid material, and finally achieve the aim of emission reduction.

In a preferred embodiment, the solid phase material obtained from the extraction unit is treated in a pretreatment agent recovery unit, and part or all of the solid phase material is returned to the waste plastic pretreatment unit as a circulating pretreatment agent, wherein the treatment mode of the pretreatment agent recovery unit can be selected from screening, regeneration or a combination of the screening and the regeneration. The pretreatment agent recovery unit may be in the form of an oscillating screen, a trommel screen, a single-stage or multi-stage fluidized bed regenerator, a rotary kiln regenerator, an infrared heating furnace, or the like.

In one embodiment of the invention, the tubular furnace pyrolysis reactor is provided with a depurating plastic-containing solution nozzle, a carrier gas inlet and a pyrolysis product outlet, wherein the carrier gas inlet is positioned at the bottom of the tubular furnace pyrolysis reactor, an air distribution plate is arranged at the upper part of the carrier gas inlet of the tubular furnace pyrolysis reactor, the depurating plastic-containing solution inlet is arranged at the lower part of the tubular furnace reactor and above the air distribution plate, the tail end of the carrier gas inlet is an atomizing nozzle, the atomizing nozzle is one or more of a single nozzle or a plurality of nozzles, the single nozzle is positioned at the axial center of the tubular furnace, the spraying direction is one or more of upward or downward, the plurality of nozzles are opposite, the spraying direction is one or more of upward or downward oblique, the pyrolysis product outlet is positioned at the top of the tubular furnace pyrolysis reactor, the tubular furnace pyrolysis reactor does not need an external heat device, and a heat preservation structure is arranged.

In one embodiment of the invention, the pyrolysis product separation system is provided with a cyclone separator and a three-phase separator; the cyclone separator is provided with a pyrolysis product inlet, a pyrolysis oil gas outlet and a semicoke outlet; the cyclone separator is one or more of one-stage or multi-stage cyclone separators connected in series or in parallel.

In one embodiment of the invention, the three-phase separator is provided with a pyrolysis oil gas inlet, a pyrolysis gas outlet, a pyrolysis water outlet and a pyrolysis oil outlet, the pyrolysis gas outlet is positioned above the three-phase separator, the pyrolysis water outlet is positioned below the three-phase separator, the pyrolysis oil outlet is positioned in the middle of the three-phase separator, and the pyrolysis oil outlet is communicated with the inlet of the fractionation system.

In one embodiment of the invention, the carbocoal outlet communicates with the pretreatment agent inlet of the waste plastic pretreatment unit.

In one embodiment of the invention, the pyrolysis gas outlet is in communication with a tube furnace pyrolysis reactor carrier gas inlet.

The invention is characterized in that:

according to the tubular furnace pyrolysis method and system for waste plastics, chlorine impurities, metal impurities and silicon impurities in the waste plastics are effectively removed, so that the influence of the chlorine impurities on a subsequent processing unit is avoided; and the silicon impurities are removed in the original form of the organic silicon polymer added in the plastic processing process, so that the problem of deactivation of the catalyst related to the subsequent processing process is effectively avoided. The waste plastics after impurity removal are subjected to pyrolysis reaction in a tube furnace pyrolysis reactor, and the light fraction of the obtained pyrolysis oil is used as a light oil product, and can be subjected to quality improvement treatment by a subsequent processing device to obtain fuel products or chemical products. The heavy fraction of the obtained pyrolysis oil can be recycled to the waste plastic pretreatment unit for recycling.

The method and the system provided by the invention have the advantages of small pollution discharge in the production process, good environmental protection, reduced carbon emission, contribution to solving the problem of white pollution, low content of harmful elements in the prepared light oil product, high added value and good environmental benefit, social benefit and economic benefit.

Drawings

FIG. 1 is a schematic view of one embodiment of a tube furnace pyrolysis process for waste plastics provided by the present invention.

Wherein: 1. a drying unit; 2. a sewage treatment unit; 3. a crushing unit; 4. a waste plastic pretreatment unit; 5. a solid-liquid separation unit; 6. an extraction unit; 7. a solvent recovery unit; 8. a tube furnace pyrolysis unit; 9. a pyrolysis product separation system; 10. and a pretreatment agent recovery unit.

Detailed Description

The invention will be further described with reference to the accompanying drawings, without thereby limiting the invention.

Fig. 1 is a schematic diagram of one embodiment of a tube furnace pyrolysis method for waste plastics, in which, as shown in fig. 1, waste plastics after preliminary treatment are dried in a drying unit 1, and waste water obtained after condensation of water vapor is discharged after being treated in a sewage treatment unit 2. The dried waste plastics enter a crushing unit 3 to be crushed into waste plastic fragments of 1-200 mm. The obtained waste plastic fragments, solvent oil and pretreatment agent enter a waste plastic pretreatment unit 4, PVC in the waste plastic fragments is fully decomposed into HCl and captured by the pretreatment agent, and most other plastics are dissolved in the solvent oil and enter a solid-liquid separation unit 5 to be separated into impurity-removed plastic-containing solution and solid-phase materials (insoluble matters). The insoluble matter is extracted in the extraction unit 6 and further separated to obtain deoiled solid and liquid phase material. The obtained liquid phase material is plastic-containing organic solvent, and enters a solvent recovery unit 7 to recover the organic solvent, and simultaneously, solid plastic particles are recovered. The deoiled solid phase material obtained by the extraction unit 6 enters the pretreatment agent recovery unit 10 for treatment, part of the deoiled solid phase material is recycled as the pretreatment agent, and the other part of the deoiled solid phase material is discharged.

The impurity-removed plastic-containing solution obtained by the solid-liquid separation unit 5 enters the tubular furnace pyrolysis unit 8 to carry out pyrolysis reaction, a pyrolysis product is separated by the pyrolysis product separation system 9 to obtain semicoke and pyrolysis oil gas, and the pyrolysis oil gas is further separated to obtain pyrolysis oil and pyrolysis gas.

The invention is further illustrated by the following examples, which are not intended to limit the invention in any way.

In the examples, the chlorine content in the solid mixture was measured by coulometry, and the specific method can be referred to the standard method of RIPP 64-90 (see, e.g., methods for petrochemical analysis (methods for RIPP test) Yang Cuiding, published by science Press, 1990, pages 164-167, "determination of total chlorine content in crude oil by coulometry"). The instrument is a Thermo Fisher ECS300 microcoulomb analyzer, the sample is a frozen and crushed waste plastic powder sample, and the obtained chlorine content is the total chlorine content of the sample and comprises organic chlorine and inorganic chlorine.

In the examples, the chlorine content of the liquid mixture was likewise determined by means of RIPP 64-90, except that the sample was a liquid mixture.

In the examples, the silicon content of the liquid mixture was determined by the method of "additive elements in used lubricating oils, wearing metals and contaminants and determination of certain elements in base oils (inductively coupled plasma emission spectrometry) (GB 17476-1998).

In the following examples, the crushing of waste plastics was carried out using a shear crusher, the mesh size of the screen being 50mm, unless explicitly stated.

The waste plastic raw materials used in the examples and comparative examples were as follows:

the waste plastic A is a greenhouse film, a mulching film and the like in a certain region of Shandong province, contains partial soil and biomass components, is crushed after being simply cleaned and dried, has ash content of 4.3 percent and water content of 10.5 percent, contains PE and a small amount of EVA as main plastic components, also contains trace amounts of other inseparable PP, PS and other materials, and has average total chlorine content of about 850 mug/g on a dry basis.

Waste plastic B is waste plastic separated from garbage in paper mill in Jiangsu province, and is crushed after preliminary drying, ash content in the obtained waste plastic B is 9.5%, water content is 15%, main components of the waste plastic are PE and PP, a small amount of PVC, PET, PS and the like are contained, and average total chlorine content of a drying base is 2.2%.

Waste plastic C is waste plastic in aged garbage dug in Guangdong landfill, the waste plastic C is crushed after multistage winnowing and preliminary drying, ash content in the obtained waste plastic C is 11.9%, water content is 12%, the waste plastic is mixed waste plastic containing PE, PP, PS, PET and PVC, and average total chlorine content of a drying base is 1.9%.

Example 1

The waste plastic pretreatment unit adopts an external heating type dissolution kettle, waste plastic A is mixed with a pretreatment agent and solvent oil, then impurity removal treatment is carried out at 350 ℃ and 1.5MPa, the retention time of the waste plastic A is 30min, and the treated material is separated into insoluble matters and impurity removal plastic-containing solution through a solid-liquid separation unit. The plastic components in the obtained impurity-removed plastic-containing solution mainly comprise PE and PP, the concentration of the plastic components is 16%, the silicon content of the plastic components is less than 1 mug/g, the chlorine content of the plastic components is 9 mug/g, and the total metal content of the plastic components is 3.5 mug/g. And (3) conveying the insoluble matters to an extraction unit, contacting with tetrahydrofuran for solvent extraction, separating the obtained product to obtain a solid-phase material and a liquid-phase material, treating the obtained solid-phase material in a pretreatment agent recovery unit, and returning part of recovered pretreatment agent to a waste plastic impurity removal treatment unit. The liquid phase material is in contact with back extractant water in a solvent recovery unit for back extraction treatment, the obtained solid-liquid mixture is filtered to obtain solid plastic particles and mixed liquid, and the obtained mixed liquid is rectified to respectively recover tetrahydrofuran and the back extractant for recycling.

The solvent oil is catalytic cracking light cycle oil, the distillation range is 180-350 ℃, the total aromatic hydrocarbon content is 69 mass percent, and the monocyclic aromatic hydrocarbon content is 48 mass percent; the weight ratio of the solvent oil to the waste plastic is 5:1.

The pretreatment agent is waste FCC balance agent provided by a refinery, and the grain diameter is 75-150 mu m; the weight ratio of the pretreatment agent to the waste plastic is 1:9.

The stripping agent is water, the dosage is 3 times of that of liquid phase materials, and the stripping temperature is normal temperature.

Example 2

The waste plastic pretreatment unit adopts an external heating type dissolution kettle, waste plastic B is mixed with a pretreatment agent and solvent oil, then is subjected to impurity removal treatment at 300 ℃ and 1.2MPa, the retention time of the waste plastic B is 40min, and the treated material is separated into insoluble matters and impurity-removed plastic-containing solution through a solid-liquid separation unit. The plastic components in the obtained impurity-removed plastic-containing solution mainly comprise PE and PP, the concentration of the plastic components is about 14.8%, the silicon content of the plastic components is less than 1 mug/g, the total chlorine content of the plastic components is 13 mug/g, and the total metal content of the plastic components is 4.1 mug/g. And (3) conveying the insoluble matters to an extraction unit, contacting with tetrahydrofuran for solvent extraction, separating the obtained product to obtain a solid-phase material and a liquid-phase material, treating the obtained solid-phase material in a pretreatment agent recovery unit, and returning part of recovered pretreatment agent to a waste plastic impurity removal treatment unit. The liquid phase material is in contact with back extractant water in a solvent recovery unit for back extraction treatment, the obtained solid-liquid mixture is filtered to obtain solid plastic particles and mixed liquid, and the obtained mixed liquid is rectified to respectively recover tetrahydrofuran and the back extractant for recycling.

The solvent oil is catalytic cracking light cycle oil, the distillation range is 180-350 ℃, the total aromatic hydrocarbon content is 69 mass percent, and the monocyclic aromatic hydrocarbon content is 48 mass percent; the weight ratio of the solvent oil to the waste plastic is 5:1.

The pretreatment agent is humus soil and CaO, the mass ratio of the humus soil to the CaO is 8:2, and the grain size is 75-150 mu m; the weight ratio of the pretreatment agent to the waste plastic is 1:7.

Example 3

The waste plastic pretreatment unit adopts an external heating type dissolution kettle, the waste plastic B is mixed with a pretreatment agent and solvent oil, then is subjected to impurity removal treatment at 350 ℃ and 1.8MPa, the retention time of the waste plastic B is 45min, and the reacted materials are separated into insoluble matters and impurity-removed plastic-containing solution through a solid-liquid separation unit. The plastic components in the obtained impurity-removed plastic-containing solution mainly comprise PE and PP, the concentration of the plastic components is 14.8%, the silicon content of the plastic components is less than 3 mug/g, the chlorine content of the plastic components is 15 mug/g, and the total metal content of the plastic components is 4.8 mug/g.

The solvent oil is VGO of a refinery, the distillation range of the solvent oil is 275-581 ℃, the total aromatic hydrocarbon content is 45.1 mass percent, and the monocyclic aromatic hydrocarbon content is 21 mass percent; the weight ratio of the solvent oil to the waste plastic is 5:1.

The pretreatment agent is activated carbon and Fe ₂ O ₃ The mass ratio is 9:1, and the grain diameter is 75-150 mu m. The weight ratio of the pretreatment agent to the waste plastic is 1:8.

Example 4

The waste plastic pretreatment unit adopts an external heating type dissolution kettle, the waste plastic B is mixed with a pretreatment agent and solvent oil, then is subjected to impurity removal treatment at 350 ℃ and 1.8MPa, the retention time of the waste plastic B is 30min, and the reacted materials are separated into insoluble matters and impurity-removed plastic-containing solution through a solid-liquid separation unit. The plastic components in the obtained impurity-removed plastic-containing solution mainly comprise PE and PP, the concentration of the plastic components is 14.8%, the silicon content of the plastic components is less than 1 mug/g, the chlorine content of the plastic components is 14 mug/g, and the total metal content of the plastic components is 4.1 mug/g.

The solvent oil is a heavy fraction of pyrolysis oil obtained by a pyrolysis unit of a tubular furnace, the distillation range is 220-550 ℃, the total aromatic hydrocarbon content is 52.9 mass percent after repeated circulation, and the monocyclic aromatic hydrocarbon content is 41.5 mass percent; the weight ratio of the solvent oil to the waste plastic is 5:1.

The pretreatment agent is semicoke and Fe obtained by a pyrolysis unit of a tube furnace ₂ O ₃ The mass ratio is 9:1, and the grain diameter is 75-150 mu m. The weight ratio of the pretreatment agent to the waste plastic is 1:8.

The obtained impurity-removed plastic-containing solution is sent into a tubular furnace pyrolysis reactor of a tubular furnace pyrolysis unit in a spray mode, and pyrolysis reaction conditions are as follows: the pyrolysis temperature was 500℃and the pyrolysis pressure was 0.1MPa.

The carrier gas of the pyrolysis reactor of the tubular furnace adopts the pyrolysis gas obtained by the unit.

Separating pyrolysis reaction products to obtain semicoke and pyrolysis oil gas, and further separating the pyrolysis oil gas to obtain fine coke powder, pyrolysis gas and pyrolysis oil; and fractionating the pyrolysis oil to obtain a light fraction and a heavy fraction. The light fraction and heavy fraction basic properties are listed in table 1.

Comparative example 1

The present comparative example was identical to the waste plastic raw material, solvent oil, and impurity removal treatment conditions of example 4, except that no pretreatment agent was used in the present comparative example. The reacted material is separated into insoluble matter and impurity-removed plastic-containing solution by a solid-liquid separation unit. The obtained impurity-removed plastic-containing solution has a silicon content of 42 mug/g, a chlorine content of 770 mug/g and a total metal content of 13 mug/g.

The impurity content in the impurity-removed plastic-containing solution obtained in the comparative example is too high, particularly the chlorine content is far higher than that of crude oil, the subsequent processing unit equipment is easy to corrode, and potential safety hazards exist.

Example 5

The waste plastic pretreatment unit adopts an external heating type dissolution kettle, waste plastic C is mixed with a pretreatment agent and solvent oil, then impurity removal treatment is carried out at 350 ℃ and 1.2MPa, the retention time of the waste plastic C is 35min, and the treated material is separated into insoluble matters and impurity removal plastic-containing solution through a solid-liquid separation unit. The plastic components in the obtained impurity-removed plastic-containing solution mainly comprise PE and PP, the concentration of the plastic components is 14.4%, the silicon content of the plastic components is 2.3 mug/g, the chlorine content of the plastic components is 8.8 mug/g, and the total metal content of the plastic components is 1.8 mug/g.

The solvent oil is adopted as a heavy fraction of pyrolysis oil obtained by a pyrolysis unit of a tubular furnace, the distillation range is 220-530 ℃, the total aromatic hydrocarbon content after multiple cycles is 55.9 mass percent, and the monocyclic aromatic hydrocarbon content is 38.7 mass percent; the weight ratio of the solvent oil to the dechlorinated waste plastic is 5:1.

The pretreatment agent is semicoke and Fe obtained by a pyrolysis unit of a tube furnace ₂ O ₃ The mass ratio is 8:2, and the grain diameter is 75-150 mu m. The weight ratio of the pretreatment agent to the waste plastic is 1:8.

The obtained impurity-removed plastic-containing solution is sent into a tubular furnace pyrolysis reactor of a tubular furnace pyrolysis unit in a spray mode, and pyrolysis reaction conditions are as follows: the pyrolysis temperature is 480 ℃ and the pyrolysis pressure is 0.1MPa.

The carrier gas of the pyrolysis reactor of the tubular furnace adopts the pyrolysis gas obtained by the unit.

Separating pyrolysis reaction products to obtain semicoke and pyrolysis oil gas, and further separating the pyrolysis oil gas to obtain fine coke powder, pyrolysis gas and pyrolysis oil; and fractionating the pyrolysis oil to obtain a light fraction and a heavy fraction. The light fraction and heavy fraction basic properties are listed in table 1.

And (3) sending the obtained oil-containing insoluble substances to an extraction unit, contacting with toluene for solvent extraction, separating the obtained products to obtain solid-phase materials and liquid-phase materials, and returning part of the obtained solid-phase materials serving as a circulating pretreatment agent to a waste plastic pretreatment device after the solid-phase materials are treated by a pretreatment agent recovery unit. And (3) rectifying the liquid phase material in a solvent recovery unit to obtain a small amount of solid plastic Particles (PS), recovered toluene and a small amount of adhered solvent oil respectively.

TABLE 1

	Example 4	Example 5
			Light fraction
Initial point of distillation	65	75
			50％	163	153
End point of distillation	220	220
			Impurity content/. Mu.g/g
Cl content	4.9	4.3
			Si content	1.9	2.2
Total metal content	＜1	＜1
			Heavy fraction
Initial point of distillation	220	220
			50％	403	427
End point of distillation	550	530
			Total aromatic hydrocarbon, mass%	52.9	55.9
Monocyclic aromatic hydrocarbon, mass%	41.5	38.7
			Impurity content/. Mu.g/g
Cl content	<1	<1
			Si content	＜1	＜1
Total metal content	＜5	＜5

It should be noted that the above-mentioned embodiments of the present invention are merely examples, and are not intended to limit the present invention, and various modifications and variations of the present invention will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (19)

1. A method for pyrolysis of waste plastic tube furnace, comprising the steps of:

(1) Waste plastics enter a waste plastics pretreatment unit, contact with a pretreatment agent and solvent oil for impurity removal treatment, and the obtained effluent is subjected to solid-liquid separation to obtain insoluble matters and impurity-removed plastic-containing solution, wherein the metal content of the impurity-removed plastic-containing solution is less than 5 mug/g, the chlorine content is less than 20 mug/g and the silicon content is less than 3 mug/g; the pretreatment agent is one or more selected from humus soil, red mud, dead catalyst of oil refining device, kaolin, semicoke, activated carbon and gasified ash, and optionally alkaline oxide,

(2) The impurity-removed plastic-containing solution is sent into a tubular furnace pyrolysis reactor in a spray mode and pyrolyzed at 400-650 ℃ to obtain pyrolysis oil gas and semicoke; and carrying out oil-gas separation on the obtained pyrolysis oil gas to obtain pyrolysis oil and pyrolysis gas.

2. The method of claim 1, further comprising step (3):

(3) The insoluble matter obtained in the step (1) enters an extraction unit, contacts with an organic solvent to perform solvent extraction, and the obtained product is separated to obtain a solid phase material and a liquid phase material,

after the obtained solid-phase material is treated by a pretreatment agent recovery unit, at least part of the solid-phase material is used as a circulating pretreatment agent to return to the step (1);

and separating out and separating the liquid phase material in a solvent recovery unit to obtain solid plastic particles and recovered organic solvent.

3. The method according to claim 2, wherein the organic solvent is selected from one or more of benzene, toluene, chloroform, cyclohexanone, ethyl acetate, butyl acetate, carbon disulfide, tetrahydrofuran, and gasoline.

4. The method of claim 2, wherein the pretreatment recovery unit comprises one or more of screening and regeneration treatment.

5. The method according to claim 2, wherein the precipitation treatment is selected from one or more of back extraction, simple distillation, flash evaporation and rectification in the solvent recovery unit.

6. The method according to claim 1, wherein the waste plastics are one or more of fresh household garbage, industrial and agricultural production and aged garbage, and the waste plastics are one or more of PE, PP, PS, PVC.

7. A method according to claim 1, characterized in that the waste plastic is cleaned, dried and crushed before entering the waste plastic pretreatment unit, the crushed waste plastic having a particle size of 1-200 mm, preferably 1-50 mm.

8. The method according to claim 1, wherein the waste plastic pretreatment unit is subjected to the following treatment conditions: the pretreatment temperature is 250-410 ℃, the pressure is 0.1-5 MPa, and the retention time of the waste plastics is 10-60 min.

9. The method according to claim 8, wherein the waste plastic pretreatment unit is subjected to the following treatment conditions: the pretreatment temperature is 280-390 ℃, the pressure is 0.5-4.0 MPa, and the retention time of the waste plastics is 15-45 min.

10. The method according to claim 1, wherein the distillation range of the solvent oil is 80-550 ℃, the total aromatic hydrocarbon content in the solvent oil is higher than 50 mass%, and the monocyclic aromatic hydrocarbon content is higher than 20 mass%; the weight ratio of the solvent oil to the waste plastic is 1:10-10:1.

11. The method according to claim 10, wherein the content of monocyclic aromatic hydrocarbon in the solvent oil is higher than 40 mass%;

the weight ratio of the solvent oil to the waste plastic is 1:1-7:1.

12. The method of claim 1, wherein the particle size of the pretreatment agent is in the range of 75 to 150 μm; the weight ratio of the pretreatment agent to the waste plastic is 1:10-2:1, preferably 1:7-1:5.

13. The method according to claim 1 or 12, wherein the pretreatment agent is one or more of spent catalytic cracking catalyst, humus soil, semicoke, activated carbon, and optionally basic oxide;

preferably, the semicoke is semicoke obtained in the step (2).

14. The method according to claim 1, wherein the solid-liquid separation unit is operated at a temperature of 250 to 410 ℃; the total metal content in the obtained impurity-removed plastic-containing solution is less than 5 mug/g, the chlorine content is less than 10 mug/g, and the silicon content is less than 2 mug/g.

15. The method according to claim 1, wherein the carrier gas of the tube furnace pyrolysis reactor is selected from the group consisting of N ₂ 、H ₂ 、CH ₄ 、CO ₂ One or more of steam, pyrolysis gas and clean synthesis gas;

the pyrolysis temperature in the pyrolysis reactor of the tube furnace is 450-550 ℃, and the pyrolysis pressure is 0.1-1 MPa.

16. The method of claim 1, wherein the pyrolysis oil in step (2) is fractionated to obtain a light fraction and a heavy fraction, and the cutting point is 180-230 ℃;

the heavy fraction obtained by pyrolysis oil fractionation is used as solvent oil and is recycled to the waste plastic pretreatment unit in the step (1);

the pyrolysis gas obtained in the step (2) is used as carrier gas of a tube furnace pyrolysis reactor.

17. The system for use in any of the methods of claims 1-16, comprising, a waste plastic pretreatment unit, a solid-liquid separation unit, a tube furnace pyrolysis unit;

the waste plastic pretreatment unit is provided with a waste plastic inlet, a pretreatment agent inlet, a solvent oil inlet and a pretreated material outlet, the pretreated material outlet is communicated with the inlet of the solid-liquid separation unit, and the solid-liquid separation unit is provided with an insoluble matter outlet and a impurity-removing plastic-containing solution outlet;

the tubular furnace pyrolysis unit is provided with a tubular furnace pyrolysis reactor and a pyrolysis product separation system; the pyrolysis product outlet of the tube furnace pyrolysis reactor is communicated with the inlet of the pyrolysis product separation system, and the pyrolysis product separation system is at least provided with a semicoke outlet, a pyrolysis oil outlet and a pyrolysis gas outlet.

18. The system of claim 17, wherein the carbocoal outlet is in communication with a pretreatment agent inlet of the waste plastic pretreatment unit;

the pyrolysis gas outlet is communicated with a carrier gas inlet of the pyrolysis reactor of the tubular furnace.

19. The system of claim 17, further comprising an extraction unit, a pretreatment recovery unit, a solvent recovery unit;

the extraction unit is provided with an insoluble matter inlet, an organic solvent inlet, a solid phase material outlet and a liquid phase material outlet, and the insoluble matter outlet of the solid-liquid separation unit is communicated with the insoluble matter inlet of the extraction unit;

the pretreatment agent recovery unit is provided with a solid-phase material inlet, a circulating pretreatment agent outlet, the solid-phase material outlet of the extraction unit is communicated with the solid-phase material inlet of the pretreatment agent recovery unit, and the circulating pretreatment agent outlet of the pretreatment agent recovery unit is communicated with the pretreatment agent inlet of the waste plastic pretreatment unit;

the solvent recovery unit is provided with a liquid-phase material inlet, a solid plastic particle outlet and a recovered organic solvent outlet, and the liquid-phase material outlet of the extraction unit is communicated with the liquid-phase material inlet of the solvent recovery unit.

Images