CN118272110A - Continuous treatment method and device for waste plastics - Google Patents

Abstract

The invention provides a continuous treatment method and a continuous treatment device for waste plastics. The invention provides a continuous treatment method of waste plastics, which comprises the steps of firstly pretreating the waste plastics, removing impurities and grease on the surface of the waste plastics, then inputting the waste plastics into a mixing unit, sequentially carrying out first cracking treatment and second cracking treatment on first slurry output by the mixing unit, finally carrying out gas-liquid separation and fractionation treatment on a treated product obtained by the second cracking treatment, and returning cracked tail oil obtained by fractionation to the mixing unit for recycling. The method provided by the invention can realize stable and continuous feeding of waste plastics, reduce the chlorine content in the pyrolysis oil, meet the requirements and the restrictions of downstream procedures on pyrolysis products, realize recycling of FCC waste catalysts and effectively improve the yield of the pyrolysis oil.

Description

Continuous treatment method and device for waste plastics

Technical Field

The invention relates to a continuous treatment method and a continuous treatment device for waste plastics, and relates to the technical field of waste plastic processing and utilization.

Background

Waste plastics are plastics which are used in civil and industrial applications and are finally eliminated or replaced, and the improper disposal of the waste plastics causes serious white pollution. At present, the treatment method for waste plastics comprises physical recovery, chemical recovery and energy recovery, wherein the physical recovery is also called mechanical recovery, and generally, the waste plastics are subjected to sorting, crushing and forming to produce plastic products again, but the method has higher requirements on the sorting fineness of raw materials, the quality of the produced plastic products is poor, and the recycling frequency is limited; the energy recovery is to recover heat in an incineration mode, but a large amount of harmful gas is generated in the combustion process, so that secondary pollution is caused; chemical recovery is to convert organic components in waste plastics into small molecular hydrocarbons by cracking or gasification techniques, and has the following advantages: 1) The chemical recovery can treat mixed, polluted or waste plastics subjected to multiple physical regeneration, and the selection range of raw materials is wider; 2) The quality of the chemical regenerated plastic is equivalent to that of primary plastic produced by fossil raw materials, and the chemical regenerated plastic can be applied to the fields of medical treatment, food and the like with higher requirements on quality, health condition and performance; 3) The waste plastic can be converted into chemical raw materials, so that the plastic is produced again, and the real recycling is realized; 4) Chemical recovery is one of the methods of waste plastic recovery treatment because the carbon emission reduction of the chemical recovery phase is less than that of energy recovery.

The pyrolysis of waste plastics refers to the process of obtaining pyrolysis oil by using waste plastics as raw materials through high-temperature pyrolysis or catalytic pyrolysis, and the pyrolysis oil can be used for producing clean fuel or chemical raw materials through refining, so that the recycling of the waste plastics is realized. However, in the process of cracking waste plastics, on one hand, the waste plastics have poor heat conductivity and high viscosity, so that continuous and stable feeding cannot be realized; on the other hand, with the widespread use of polyvinyl chloride and the use of chlorine-containing modifiers in plastic processing, the waste plastics inevitably contain chlorine elements, and a large amount of chlorinated hydrocarbons are generated in the cracking process, which can cause problems such as equipment corrosion, catalyst poisoning, and ammonium chloride blockage to downstream units, so how to improve the stability and continuity of waste plastic feeding and reduce the chlorine content in waste plastic cracking products has been paid attention to those skilled in the art.

Catalytic cracking is the most important secondary process in the oil refining industry, the short replacement period of the FCC catalyst results in very high catalyst and process costs, and the harmful heavy metals and catalyst suspended particles contained in the spent catalyst can cause certain pollution to soil, water and air. In addition, the pyrolysis tail oil generated in the waste plastic processing process has complex components, high impurity content and low utilization value. In the actual industrial process, how to effectively recycle the FCC spent catalyst and the pyrolysis tail oil is also one of the hot spots of continuous interest to those skilled in the art.

Disclosure of Invention

The invention provides a continuous treatment method of waste plastics, which is characterized in that waste plastics and pyrolysis tail oil are mixed to form mixed first slurry, the first slurry is subjected to first pyrolysis treatment and second pyrolysis treatment in sequence, and the pyrolysis tail oil obtained by treatment is returned to a mixing unit for recycling, so that stable and continuous feeding of the waste plastics can be realized, the chlorine content in the pyrolysis oil is reduced, the requirements and the restrictions of downstream procedures on pyrolysis products are met, the recycling of FCC waste catalysts is realized, and the yield of the pyrolysis oil is effectively improved.

The invention also provides a processing device for realizing the processing method.

The invention provides a continuous treatment method of waste plastics, which is carried out by adopting a mixing unit, a first cracking unit, a second cracking unit, a gas-liquid separation unit and a fractionating unit which are sequentially communicated, wherein at least one outlet of the fractionating unit is communicated with an inlet of the mixing unit, the first cracking unit comprises a gas input port and a gas output port, an FCC waste catalyst is loaded in the second cracking unit, and the treatment method comprises the following steps:

pretreating waste plastics, and inputting the pretreated waste plastics into a mixing unit;

Inputting the first slurry output by the mixing unit into a first cracking unit for first cracking treatment, wherein the first cracking treatment is carried out under an anaerobic condition, inputting protective gas into the first cracking unit through the gas input port, purging the first slurry, and discharging gas in the first cracking treatment process through the gas output port; the temperature in the first cracking unit is 220-380 ℃, and at least comprises two temperature areas, wherein the temperature of the temperature area close to the inlet side is lower than that of the temperature area close to the outlet side, and the temperature difference between the two adjacent temperature areas is not lower than 20 ℃;

Inputting the second slurry output by the first cracking unit into a second cracking unit for second cracking treatment, wherein the temperature of the second cracking unit is 420-550 ℃;

And (3) enabling the treated product obtained after the second cracking treatment to enter a gas-liquid separation unit for gas-liquid separation, collecting liquid materials, enabling the liquid materials to enter a fractionation unit for fractionation treatment, inputting cracked tail oil obtained after fractionation into a mixing unit, and mixing the cracked tail oil with pretreated waste plastics.

Firstly, pretreating waste plastics, removing impurities and grease on the surface of the waste plastics, and inputting the waste plastics into a mixing unit; then, sequentially carrying out first cracking treatment and second cracking treatment on the first slurry output by the mixing unit, controlling chlorine-containing compounds in waste plastics to gradually decompose in a partition heating mode in the first cracking treatment process, and purging with protective gas to avoid recombination of decomposed HCl gas and waste plastic cracking products to generate organic chloride again; meanwhile, the second cracking treatment is carried out under the catalysis of the FCC waste catalyst, so that the waste plastics can be catalytically cracked, the cracking capacity of the waste plastics is improved, HCl and other impurities such as silicon and Fe generated in the waste plastics cracking process can be effectively adsorbed, organic chlorine generated by recombination of HCl and cracking products is avoided, the adsorption and removal of HCl and organic chlorine are realized, and the recycling of the FCC waste catalyst is realized; and finally, carrying out gas-liquid separation treatment and fractionation treatment on the treated product of the second cracking treatment, and returning the fractionated cracked tail oil to a mixing unit for recycling, thereby being beneficial to improving the utilization rate of the cracked tail oil and realizing the stability and continuity of waste plastic feeding. Therefore, by the method provided by the invention, stable and continuous feeding of waste plastics can be realized, the chlorine content in the pyrolysis oil is reduced, the requirements and the restrictions of downstream procedures on pyrolysis products are met, the recycling of the FCC waste catalyst is realized, and the yield of the pyrolysis oil is effectively improved.

In a specific embodiment, the treatment method is performed by adopting a mixing unit, a first cracking unit, a second cracking unit, a gas-liquid separation unit and a fractionation unit which are sequentially communicated, wherein at least one outlet of the fractionation unit is communicated with an inlet of the mixing unit, the first cracking unit and the second cracking unit can be mutually independent reaction units or can be different partitions in the same reaction unit, the first cracking unit comprises a gas input port and a gas output port, and the second cracking unit is internally loaded with FCC spent catalyst, and the treatment process is described in detail below:

Step 1, pretreating waste plastics, and inputting the pretreated waste plastics into a mixing unit;

The waste plastics comprise bags, barrels, containers in textile industry, packaging materials in household appliance industry, building materials and pipes in building industry, shrink films in canning industry, packaging bags in food processing, mulching films in agriculture, automobile decomposed materials, household garbage and the like which are used in chemical industry; the main component comprises one or two of polypropylene (PP) and Polyethylene (PE), and can also comprise polyvinyl chloride (PVC), but the PVC content in the waste plastics is not higher than 20 percent, further, the PVC content is not higher than 10 percent, such as 1 percent, 2 percent, 3 percent, 5 percent, 8 percent and 10 percent, in consideration of the quality and processing requirement of the waste plastic cracking products.

Firstly, pretreating waste plastics, wherein the pretreatment comprises crushing treatment and cleaning treatment, and specifically, a conventional crusher can be adopted to crush the waste plastics into plastic sheets or particles with the diameter of 20-50 mm; the cleaning treatment can be carried out in a sedimentation tank to remove mud, metal impurities and grease attached to the surface of the waste plastic, and specifically, the mass ratio of the waste plastic to the water is 1:10-10:1, filtering and drying the cleaned waste plastic, wherein the water content of the dried waste plastic is controlled below 3 percent.

Next, the pretreated waste plastics are input into a mixing unit.

Along with the progress of the pyrolysis reaction, the pyrolysis tail oil from the fractionation unit is returned and input into the mixing unit, the temperature of the mixing unit is controlled to be 120-220 ℃, and the mixing process is carried out in a stirring state, so that most of waste plastics are dissolved in the pyrolysis tail oil, and the undissolved part is fully fused with the pyrolysis tail oil under the action of heating and stirring, thereby realizing the stability and continuity of waste plastics feeding.

Step 2, inputting the first slurry output by the mixing unit into a first cracking unit for first cracking treatment;

The method comprises the steps of inputting first slurry output by a mixing unit into a first cracking unit in a continuous reaction mode for first cracking treatment, wherein the first cracking unit is a horizontal reaction furnace, the temperature in the first cracking unit is controlled to be 220-380 ℃, the first cracking unit is mainly used for decomposing part of PVC in waste plastics, and further, the temperature in the first cracking unit is controlled to be 250-350 ℃.

In the first cracking treatment process, in order to remove HCl generated by cracking waste plastics, the first cracking treatment is performed under the condition of purging by a protective gas, specifically, the protective gas is input into the first cracking unit through the gas input port to purge the first slurry, and the gas in the first cracking treatment process is discharged through the gas output port, so that the possibility of generating organic chlorine by combining a decomposed product with the HCl again is reduced, corrosion of a device caused by combining the HCl with water vapor to generate hydrochloric acid is avoided, and the protective gas can be N2.

In order to absorb HCl released in the first cracking treatment process and avoid environmental pollution, the gas generated in the first cracking treatment process is input into an absorption liquid, wherein the absorption liquid can be NaOH solution or lime milk solution with pH value more than or equal to 7.

In order to enable the waste plastics to be slowly decomposed and HCl to be timely removed under the condition of blowing of protective gas, the first pyrolysis unit comprises at least two temperature areas, the temperature areas are distributed in sequence from one side of an inlet to one side of an outlet of the first pyrolysis unit, the temperature of the temperature area close to the inlet is lower than that of the temperature area close to one side of an output port, and the temperature difference between the two adjacent temperature areas is not lower than 20 ℃; for example, from the inlet side to the outlet side of the first cracking unit, the first temperature zone, the second temperature zone and the third temperature zone are included, the temperature of the first temperature zone is T1, the temperature of the second temperature zone is T2, the temperature of the third temperature zone is T3, T1 is more than or equal to 220 ℃ and less than T2 is less than or equal to 380 ℃, T2-T1 is more than or equal to 20 ℃, and T3-T2 is more than or equal to 20 ℃.

Step 3, inputting the second slurry output by the first cracking unit into a second cracking unit for second cracking treatment;

And (3) inputting the second slurry after the first cracking treatment into a second cracking unit for second cracking treatment in a continuous reaction mode, wherein the second cracking unit is a horizontal reaction furnace, the temperature in the second cracking unit is controlled to be 420-550 ℃, and an anaerobic or anoxic environment is maintained, so that the method is mainly used for cracking other waste plastics such as PE, PP and the like, and meanwhile, the PVC which is partially and incompletely decomposed is also provided.

In order to improve the cracking capacity of waste plastics and adsorb and remove HCl and other impurities generated in the second cracking process, and prevent HCl from being recombined with cracked products to generate organic chlorine, the second cracking treatment is performed in the environment of FCC waste catalyst, wherein the FCC waste catalyst is a waste FCC catalyst, and specifically is an FCC catalyst which is deactivated or crushed.

The number of times of use of the FCC spent catalyst is not more than 4 times in consideration of the efficiency of use of the FCC spent catalyst.

And 4, enabling the treated product obtained after the second cracking treatment to enter a gas-liquid separation unit for gas-liquid separation, collecting liquid materials, enabling the liquid materials to enter a fractionation unit for fractionation, inputting cracked tail oil obtained after fractionation into a mixing unit, and mixing the cracked tail oil with pretreated waste plastics.

And inputting the treated product output by the second cracking unit into a gas-liquid separation unit for gas-liquid separation to obtain cracked gas and cracked oil, then carrying out fractional distillation treatment on the cracked oil, and returning the cracked tail oil obtained by cutting into a mixing unit to be used as a solvent of waste plastics for continuous recycling, wherein the cutting temperature of the cracked tail oil is 300-500 ℃, and further 360-450 ℃.

In addition to the tail oil fraction, the pyrolysis oil of the rest fraction can be separated into gasoline and diesel oil according to the need, or divided into finer fraction segments, which can be carried out according to the conventional technical means and actual needs in the art.

In summary, the method provided by the invention can realize stable and continuous feeding of waste plastics, reduce the chlorine content in the pyrolysis oil, meet the requirements and the restrictions of downstream procedures on pyrolysis products, realize recycling of FCC waste catalysts, and effectively improve the yield of the pyrolysis oil.

The second aspect of the invention provides a device for implementing any one of the methods, the device comprising a pretreatment unit, a mixing unit, a first cracking unit, a second cracking unit, a gas-liquid separation unit, a fractionation unit and a heating unit, wherein:

The pretreatment unit is used for pretreating the waste plastics;

the mixing unit comprises a waste plastic inlet and a pyrolysis tail oil inlet, wherein the waste plastic inlet is used for inputting pretreated waste plastic, and the pyrolysis tail oil inlet is communicated with at least one outlet of the fractionating unit;

The outlet of the mixing unit is communicated with the material inlet of the first cracking unit, the first cracking unit comprises a slurry conveyer, a gas input port and a gas output port, the slurry conveyer is used for conveying slurry in the first cracking unit to the material outlet, the gas input port is used for conveying protective gas into the first cracking unit, and the gas output port is used for exhausting gas in the first cracking process;

the material outlet of the first cracking unit is communicated with the material inlet of the second cracking unit, a catalyst storage is arranged in the second cracking unit, and an FCC spent catalyst is stored in the catalyst storage;

The material outlet of the second cracking unit is communicated with the inlet of the gas-liquid separation unit, the liquid phase outlet of the gas-liquid separation unit is communicated with the inlet of the fractionation unit, and at least one outlet of the fractionation unit is communicated with the pyrolysis tail oil inlet;

the heating unit is used for controlling the temperatures in the mixing unit, the first cracking unit and the second cracking unit, and realizing that the first cracking unit comprises at least two temperature areas.

In a specific implementation manner, fig. 1 is a schematic structural diagram of an apparatus according to an embodiment of the present invention, and as shown in fig. 1, the apparatus includes a pretreatment unit, a mixing unit 1, a first cracking unit 21, a second cracking unit 22, a gas-liquid separation unit 3, a fractionation unit 4, and a heating unit, and each unit is described in detail below:

The pretreatment unit is used for pretreating waste plastics, and specifically comprises a crushing unit and a cleaning unit, wherein the crushing unit is specifically a crusher, the cleaning unit can be a sedimentation tank, and the crushing unit and the cleaning unit are respectively used for crushing and cleaning the waste plastics.

The mixing unit 1 comprises a waste plastic inlet and a pyrolysis tail oil inlet, an outlet of the pretreatment unit 1 can be communicated or not communicated with the waste plastic inlet, waste plastic treated by the pretreatment unit is input into the mixing unit 1 in an automatic continuous sample injection or manual carrying mode, pyrolysis tail oil cut by the fractionation unit 4 is input into the mixing unit 1 through the pyrolysis tail oil inlet, and the mixing unit 1 mixes the pretreated waste plastic and the pyrolysis tail oil.

Further, the heating unit is connected with the mixing unit 1, and the temperature in the mixing unit 1 is controlled to be 120-220 ℃; the mixing unit 1 is internally provided with a stirrer for stirring the waste plastics and the pyrolysis tail oil, so that most of the waste plastics are dissolved in the pyrolysis tail oil to form first slurry.

The outlet of the mixing unit 1 is communicated with the material inlet of the first cracking unit 21, and the material outlet of the first cracking unit 21 is communicated with the material inlet of the second cracking unit 22, so that the first slurry output by the mixing unit 1 is continuously cracked through the first cracking unit 21 and the second cracking unit 22. Fig. 2 is a schematic structural diagram of a first cracking unit and a second cracking unit according to an embodiment of the present invention, and fig. 3 is a schematic structural diagram of a first cracking unit and a second cracking unit according to another embodiment of the present invention, as shown in fig. 2 and 3, the first cracking unit 21 and the second cracking unit 22 may be two independent cracking units or two partitions in one cracking unit, and the first cracking unit 21 and the second cracking unit 22 may be a horizontal reaction furnace.

Since the first slurry entering the first cracking unit 21 is in a viscous paste form, a slurry conveyer 212 is disposed in the first cracking unit 21 and is used for conveying the slurry in the first cracking unit 21 to the material outlet, the slurry conveyer 212 may be a propeller, and the slurry is pushed to advance along the propeller at a certain speed and is output from the output port.

The heating unit is connected with the first cracking unit 21, and is used for controlling the temperature in the first cracking unit 21 and realizing that the first cracking unit 21 comprises at least two temperature areas; for example, with continued reference to fig. 2, the first pyrolysis unit 21 is heated by the heating unit, so that the first pyrolysis unit 21 includes three temperature zones, where the temperature of the first temperature zone is T1, the temperature of the second temperature zone is T2, the temperature of the third temperature zone is T3, and the temperatures of the three temperature zones are as described above.

In order to discharge HCl generated by the pyrolysis of PVC, the first pyrolysis unit 21 is provided with a gas inlet 213 and a gas outlet 214, the gas inlet 213 is used for delivering a shielding gas into the first pyrolysis unit 21, and the gas outlet 214 is used for collecting the gas during the first pyrolysis treatment.

The device provided by the invention further comprises an absorption unit, wherein the absorption unit is communicated with the gas outlet 214, and absorption liquid is stored in the absorption unit and is used for absorbing gas exhausted from the gas outlet 214.

The material outlet of the first cracking unit 21 is communicated with the material inlet of the second cracking unit 22, a catalyst storage 221 is arranged in the second cracking unit 22, the catalyst storage 221 and the second cracking unit 22 are overlapped in the axial direction, and a certain rotating speed is maintained, so that the slurry in the second cracking unit 22 can be pushed to move towards the direction of the output port.

The catalyst storage 221 stores therein an FCC spent catalyst for catalyzing the pyrolysis reaction of the material in the second pyrolysis unit 22, and performing adsorption removal on HCl and organic chlorine generated during the second pyrolysis process.

Further, the inside diameter of the catalyst storage 221 is D1, the inside diameter of the second cracking unit 22 is D2, D1/D2 is less than or equal to 1/2 and less than or equal to 2/3, and on the basis of combining the FCC spent catalyst and the organic chlorine, the catalyst storage is prevented from being blocked by waste plastic coking.

In addition, a cleaner 222 and a waste output port 223 are disposed in the second pyrolysis unit 22, the cleaner 222 is disposed on the inner wall of the second pyrolysis unit 22, and the waste output port 223 is disposed on the bottom wall of the second pyrolysis unit 22 near the outlet, for discharging the waste residue generated during the second pyrolysis process; the cleaner 222 may be a scraper, specifically, to remove residues remaining in the second pyrolysis unit 22, and is discharged through the waste outlet 223, and is discharged once, typically at 5-10 hours.

The material outlet of the second cracking treatment unit 22 is communicated with the inlet of the gas-liquid separation unit 3, the liquid phase outlet of the gas-liquid separation unit 3 is communicated with the inlet of the fractionation unit 4, and at least one outlet of the fractionation unit 4 is communicated with the cracked tail oil inlet of the mixing unit 1, so that the cracked tail oil obtained by fractionation is returned to the mixing unit for recycling.

The gas-liquid separation unit 3 and the fractionation unit 4 may be provided according to conventional means in the art, and the fractionation temperature and outlet may be set according to the fraction to be cut.

Considering the continuity of the cracking process, avoiding the influence of loading and unloading of the FCC waste catalyst on the waste plastic treatment process, parallel cracking units can be arranged, the FCC waste catalyst is loaded in the two cracking units, and when the FCC waste catalyst needs to be replaced, the spare cracking units are used for waste plastic treatment; specifically, when the first cracking unit 21 and the second cracking unit 22 are independent of each other, two parallel second cracking units 22 may be provided, and when the FCC spent catalyst needs to be replaced, the material output port of the first cracking unit 21 is communicated with the spare second cracking unit 22; when the first pyrolysis unit 21 and the second pyrolysis unit are different partitions of the same reactor, parallel reactors are required to be arranged, and when the FCC spent catalyst needs to be replaced, the material outlet of the mixing unit 1 is communicated with the first pyrolysis unit and the second pyrolysis unit which are standby, and the first pyrolysis unit and the second pyrolysis unit which are standby are used for treating the waste plastics.

In summary, the device provided by the invention can be used for continuous treatment of waste plastics, can realize stable and continuous feeding of waste plastics, simultaneously reduces the chlorine content in pyrolysis oil, meets the requirements and the restrictions of downstream procedures on pyrolysis products, realizes recycling of FCC waste catalysts, and effectively improves the yield of pyrolysis oil.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the drawings that are needed in the embodiments or the description of the prior art will be briefly described below, it will be obvious that the drawings in the following description are some embodiments of the present invention, and that other drawings can be obtained according to these drawings without inventive effort to a person skilled in the art.

FIG. 1 is a schematic diagram of an apparatus according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a first pyrolysis unit and a second pyrolysis unit according to an embodiment of the present invention;

Fig. 3 is a schematic structural diagram of a first cracking unit and a second cracking unit according to another embodiment of the present invention.

Reference numerals illustrate:

1-a mixing unit;

21-a first cleavage unit;

212-slurry conveyor;

213-gas entry port;

214-a gas outlet;

22-a second cleavage unit;

221-a catalyst storage;

222-a cleaner;

223-a waste outlet;

3-a gas-liquid separation unit;

4-fractionation unit.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described in the following in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Example 1

The embodiment provides a processing apparatus, including pretreatment unit, mixing unit, first pyrolysis unit, the second pyrolysis unit, gas-liquid separation unit, fractionating unit, absorption unit and heating unit, pretreatment unit is used for carrying out preliminary treatment to waste plastics, mixing unit includes the waste plastics entry, pyrolysis tail oil entry and first thick liquids export, waste plastics entry communicates with the export of pretreatment unit, pyrolysis tail oil entry communicates with at least one export of fractionating unit, first thick liquids export communicates first pyrolysis unit and second pyrolysis unit in proper order, the material export of second pyrolysis unit communicates with the entry of gas-liquid separation unit, gas-liquid separation unit includes gaseous phase export and liquid phase export, liquid phase export and fractionating unit's entry intercommunication, fractionating unit's at least one export communicates with pyrolysis tail oil entry, heating unit is connected with mixing unit respectively, first pyrolysis unit and second pyrolysis unit, wherein:

The pretreatment unit comprises a crusher and a sedimentation tank, wherein the crusher is used for crushing waste plastics into plastic sheets or particles with the diameter of 20-50mm, the crushed waste plastics enter the sedimentation tank, water is contained in the sedimentation tank, and under the action of gravity, mud and metal impurities on the surface of the waste plastics are precipitated to the bottom of the sedimentation tank, and the upper layer is scraped to remove grease.

The mixing unit is specifically a dissolution kettle with a stirrer arranged inside, and the temperature in the dissolution kettle is controlled through the heating unit.

The first pyrolysis unit and the second pyrolysis unit are shown in fig. 2, wherein a propeller is arranged in the first pyrolysis unit 5 and used for pushing the slurry to advance.

The bottom that first schizolysis unit is close to the entry is provided with the gas input mouth, and the upper portion that is close to the export is provided with the gas output mouth, and the gas input mouth is connected with nitrogen gas for carry nitrogen gas in succession to first schizolysis unit, gas output mouth and absorption unit intercommunication are used for collecting the gas that produces in the first schizolysis treatment process and input to the absorption unit in.

0 Controlling the temperature in the first cracking unit to be the same through the heating unit.

The second cracking unit is internally provided with a catalyst storage, a scraping plate and a waste output port, the catalyst storage internally stores FCC waste catalyst, the inner diameter of the catalyst storage is D1, the inner diameter of the second cracking unit is D2, and the D1/D2 is 1/2; the scraper is used for removing residues remained in the second cracking unit and discharging the residues through the waste output port.

5

Example 2

This embodiment provides a processing apparatus, which can refer to embodiment 1, and is different in that the first pyrolysis unit and the second pyrolysis unit are shown in fig. 3, i.e., the first pyrolysis unit and the second pyrolysis unit are two partitions of a horizontal reaction furnace.

0

Example 3

The present embodiment provides a treatment apparatus, which can refer to embodiment 1, and is different in that the first pyrolysis unit includes three temperature areas, and the three temperature areas are sequentially distributed along the direction from the inlet to the outlet of the first pyrolysis unit.

5

Example 4

The present embodiment provides a treatment apparatus, which can refer to embodiment 2, and is different in that the first pyrolysis unit includes three temperature areas, and the three temperature areas are sequentially distributed along the direction from the inlet to the outlet of the first pyrolysis unit.

Example 5

The embodiment provides a continuous treatment method for waste plastics, using the apparatus provided in embodiment 1, the treatment method specifically includes the following steps:

the waste plastics are obtained by mixing beverage bottles, disposable plastic bags and the like in the household garbage, and the Cl content in the waste plastics is 3 percent by a combustion-microcoulomb method.

Crushing waste plastics into particles with the particle size smaller than 50mm by a small freezing crusher in a laboratory, cleaning the crushed waste plastics particles in an ultrasonic cleaner, precipitating and removing impurities, and drying by a cyclone dryer to obtain the waste plastics with the water content of 2.1%.

The dried waste plastic particles and pyrolysis tail oil are stirred and mixed in a dissolution kettle at the normal pressure of 180 ℃ to form first slurry, the first slurry is input into a first pyrolysis unit through a raw material pump for first pyrolysis treatment, the temperature is controlled to be 250 ℃, and the feeding speed is 100g/min. N2 is continuously introduced into the furnace through the gas inlet for purging, the flow rate of N2 is 50ml/min, and N2 and gas generated by the first cracking treatment are output from the gas outlet and enter the absorption unit for absorption.

The slurry after the first cracking treatment enters a second cracking unit to carry out second cracking treatment, the temperature is controlled to be 480 ℃, the second cracking treatment is carried out under the environment of FCC spent catalyst, and the loading capacity of the FCC spent catalyst is 200g.

And (3) separating gas from liquid of the treated product after the second cracking treatment, and collecting to obtain cracking gas and cracking oil, wherein the yield of the cracking gas is 14.7%, the yield of the cracking oil is 75.2%, and the chlorine content in the cracking oil is 29ppm. Fractionating the pyrolysis oil, cutting gasoline fraction with the temperature of less than 180 ℃, diesel fraction with the temperature of 180-360 ℃ and tail oil with the temperature of more than 360 ℃, returning the tail oil with the temperature of more than 360 ℃ to a mixing unit for mixing with waste plastics, and recycling the mixture into the pyrolysis furnace.

Example 6

The embodiment provides a continuous treatment method for waste plastics, using the apparatus provided in embodiment 1, the treatment method specifically includes the following steps:

the Cl content of the waste plastics was 6% as measured by combustion-microcoulomb method using mixed waste plastics from paper mill.

Crushing waste plastics into particles with the particle size smaller than 50mm by a small freezing crusher in a laboratory, cleaning the crushed waste plastics particles in an ultrasonic cleaner, precipitating and removing impurities, and drying by a cyclone dryer to obtain the waste plastics with the water content of 1.8%.

The dried waste plastic particles and pyrolysis tail oil are stirred and mixed in a dissolution kettle at the normal pressure of 220 ℃ to form first slurry, the first slurry is input into a first pyrolysis unit through a raw material pump to carry out first pyrolysis treatment, the furnace temperature is controlled to be 280 ℃ through a heating unit, the feeding speed is 120g/min, N2 is continuously introduced into the furnace through a gas input port to purge, the flow of N2 is 60ml/min, and the N2 and gas generated by the first pyrolysis treatment are output from a gas output port and enter an absorption unit to be absorbed.

And (3) feeding the slurry subjected to the first cracking treatment into a second cracking unit for second cracking treatment, wherein the furnace temperature is controlled to be 430 ℃, and the second cracking treatment is carried out in an FCC spent catalyst environment, and the loading capacity is 200g.

And (3) separating gas from liquid of the treated product after the second cracking treatment, and collecting to obtain cracking gas and cracking oil, wherein the yield of the cracking gas is 19.6%, the yield of the cracking oil is 76.5%, and the chlorine content in the cracking oil is 38ppm. Cutting the pyrolysis oil to obtain gasoline fraction with the temperature of 180 ℃, diesel oil fraction with the temperature of 180-360 ℃ and tail oil with the temperature of more than 360 ℃, returning the tail oil with the temperature of more than 360 ℃ to a mixing unit for mixing with waste plastics, and recycling the mixture into the pyrolysis furnace.

Example 7

The embodiment provides a continuous treatment method for waste plastics, which uses the device provided in embodiment 3, and specifically includes the following steps:

the Cl content of the waste plastics was measured by combustion-microcoulomb method using mixed waste plastics from paper mill and was 4.3%.

Crushing waste plastics into particles with the particle size smaller than 50mm by a small freezing crusher in a laboratory, cleaning the crushed waste plastics particles in an ultrasonic cleaner, precipitating and removing impurities, and drying by a cyclone dryer to obtain the waste plastics with the water content of 2.0%.

The dried waste plastic particles and pyrolysis tail oil are stirred and mixed in a dissolution kettle at the normal pressure of 200 ℃ to form first slurry, the first slurry is input into a first pyrolysis unit through a raw material pump to carry out first pyrolysis treatment, the temperatures of the first temperature zone, the second temperature zone and the third temperature zone are 250 ℃, 300 ℃, 350 ℃ and the feeding speed is 150g/min. N2 is continuously introduced into the furnace through the gas inlet for purging, the flow rate of N2 is 80ml/min, and N2 and gas generated by the first cracking treatment are output from the gas outlet and enter the absorption unit for absorption.

And (3) feeding the slurry subjected to the first cracking treatment into a second cracking unit for second cracking treatment, controlling the furnace temperature to be 550 ℃, and carrying out the second cracking treatment in an FCC spent catalyst environment with a loading capacity of 180g.

And (3) separating gas from liquid of the treated product after the second cracking treatment, and collecting to obtain cracking gas and cracking oil, wherein the yield of the cracking gas is 16.3%, the yield of the cracking oil is 78.3%, and the chlorine content in the cracking oil is 25ppm. Fractionating the pyrolysis oil, cutting gasoline fraction with the temperature of less than 180 ℃, diesel fraction with the temperature of 180-360 ℃ and tail oil with the temperature of more than 360 ℃, returning the tail oil with the temperature of more than 360 ℃ to a mixing unit for mixing with waste plastics, and recycling the mixture into the pyrolysis furnace.

Example 8

This example provides a continuous process for the treatment of waste plastics, using the apparatus provided in example 1, setting the temperature in the first pyrolysis unit to 300 ℃, all other conditions being the same as in example 7.

The yield of the collected pyrolysis gas is 16.5 percent, the yield of the pyrolysis oil is 76.3 percent, and the chlorine content in the pyrolysis oil is 41ppm; cutting the fraction of the pyrolysis oil to obtain gasoline fraction with the temperature of 180 ℃, diesel oil fraction with the temperature of 180-360 ℃ and tail oil with the temperature of more than 360 ℃, returning the tail oil with the temperature of more than 360 ℃ to a mixing unit for mixing with waste plastics, and recycling the mixture into the pyrolysis furnace.

Example 9

The embodiment provides a continuous treatment method for waste plastics, which uses the device provided in embodiment 2, and specifically includes the following steps:

The Cl content of the waste plastics was measured by combustion-microcoulomb method using mixed waste plastics from paper mill to be 6.0%.

Crushing waste plastics into particles with the particle size smaller than 50mm by a small freezing crusher in a laboratory, cleaning the crushed waste plastics particles in an ultrasonic cleaner, precipitating and removing impurities, and drying by a cyclone dryer to obtain the waste plastics with the water content of 1.9%.

The dried waste plastic particles and pyrolysis tail oil are stirred and mixed in a dissolution kettle at the normal pressure of 200 ℃ to form mixed slurry, the mixed slurry is input into a first pyrolysis unit through a raw material pump to carry out first pyrolysis treatment, the temperature is controlled to be 330 ℃, the feeding speed is 150g/min, N2 is continuously introduced into a furnace through a gas input port to purge, the flow rate of N2 is 100ml/min, and the N2 and gas generated by the first pyrolysis treatment are output from a gas output port and enter an absorption unit to be absorbed.

And (3) feeding the slurry subjected to the first cracking treatment into a second cracking unit for second cracking treatment, controlling the furnace temperature to be 520 ℃, and carrying out the second cracking treatment in the environment of FCC spent catalyst with the loading capacity of 150g.

Collecting the treated product after the second cracking treatment after gas-liquid separation to obtain cracking gas and cracking oil, wherein the yield of the cracking gas is 14.9%, the yield of the cracking oil is 81.4%, and the chlorine content in the cracking oil is 51ppm; cutting the pyrolysis oil to obtain gasoline fraction with the temperature of 180 ℃, diesel oil fraction with the temperature of 180-360 ℃ and tail oil with the temperature of more than 360 ℃, returning the tail oil with the temperature of more than 360 ℃ to a mixing unit for mixing with waste plastics, and recycling the mixture into the pyrolysis furnace.

Example 10

This example provides a continuous treatment method for waste plastics, using the apparatus provided in example 4, the temperatures of the first, second and third temperature zones are 240 ℃, 300 ℃, 360 ℃ respectively, and the other conditions are the same as those in example 9.

The yield of the collected pyrolysis gas is 17.2 percent, the yield of the pyrolysis oil is 81.9 percent, and the chlorine content in the pyrolysis oil is 43ppm; cutting the pyrolysis oil to obtain gasoline fraction with the temperature of 180 ℃, diesel oil fraction with the temperature of 180-360 ℃ and tail oil with the temperature of more than 360 ℃, returning the tail oil with the temperature of more than 360 ℃ to a mixing unit for mixing with waste plastics, and recycling the mixture into the pyrolysis furnace.

Comparative example 1

This comparative example provides a method for treating waste plastics, which uses the same waste plastics as in example 5, and the waste plastics are pretreated and then directly enter a kettle-type cracking furnace for cracking treatment, the furnace temperature is controlled to be 500 ℃, and the treated product is obtained after the treatment is finished.

And (3) collecting pyrolysis gas and pyrolysis oil after the treated product enters a gas-liquid separator, wherein the yield of the pyrolysis gas is 19.7%, the yield of the pyrolysis oil is 59.3%, and the chlorine content in the pyrolysis oil is 631ppm.

Comparative example 2

This comparative example provides a method for treating waste plastics, using the same waste plastics and pretreatment method as in example 5, the pretreated waste plastics were fed into an extruder for melt extrusion treatment, the temperature of the feeding section was controlled at 130 ℃, and the compression section and the extrusion section were both controlled at 200 ℃.

Inputting the slurry after the melt extrusion treatment into a first cracking unit for first cracking treatment, controlling the furnace temperature to be 250 ℃, controlling the feeding speed to be 100g/min, continuously introducing N2 into the furnace through a gas input port for purging, wherein the N2 flow is 50ml/min, outputting N2 and gas generated by the first cracking treatment from a gas output port, and entering an absorption unit for absorption.

The slurry after the first cracking treatment enters a second cracking unit to carry out second cracking treatment, the furnace temperature is controlled to be 500 ℃, the second cracking treatment is carried out under the environment of FCC spent catalyst, and the loading capacity of the FCC spent catalyst is the same as that of the embodiment 5.

And (3) after the treated product after the second cracking treatment enters a gas-liquid separator, collecting cracking gas and cracking oil, wherein the yield of the cracking gas is 14.5%, the total yield of the cracking oil is 69.2%, and the chlorine content in the cracking oil is 39ppm.

Comparative example 3

This comparative example provides a method for treating waste plastics, using the same waste plastics and pretreatment method as in example 5, the pretreated waste plastics were fed into an extruder for melt extrusion treatment, the temperature of the feeding section was controlled at 130 ℃, and the compression section and the extrusion section were both controlled at 200 ℃.

Inputting the slurry after the melt extrusion treatment into a first cracking unit for first cracking treatment, controlling the furnace temperature to be 250 ℃ through a heater, continuously introducing N2 into the furnace through a gas input port for purging, outputting N2 and gas generated by the first cracking treatment from a gas output port, and entering an absorption unit for absorption.

And (3) feeding the slurry after the first cracking treatment into a second cracking unit for carrying out second cracking treatment, wherein the second cracking treatment is thermal cracking, namely, no catalyst or adsorbent is added, and the furnace temperature is controlled to be 500 ℃.

And (3) after the treated product after the second cracking treatment enters a gas-liquid separator, collecting cracking gas and cracking oil, wherein the yield of the cracking gas is 21.3%, the total yield of the cracking oil is 43.7%, and the chlorine content in the cracking oil is 103ppm.

In summary, the method provided by the invention can realize stable and continuous feeding of waste plastics, reduce the chlorine content in the pyrolysis oil, meet the requirements and the restrictions of downstream procedures on pyrolysis products, realize recycling of FCC waste catalysts, and effectively improve the yield of the pyrolysis oil.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims (10)

1. The continuous treatment method for waste plastics is characterized by adopting a mixing unit, a first cracking unit, a second cracking unit, a gas-liquid separation unit and a fractionation unit which are sequentially communicated, wherein at least one outlet of the fractionation unit is communicated with an inlet of the mixing unit, the first cracking unit comprises a gas input port and a gas output port, the second cracking unit is internally loaded with an FCC waste catalyst, and the treatment method comprises the following steps:

pretreating waste plastics, and inputting the pretreated waste plastics into a mixing unit;

Inputting the first slurry output by the mixing unit into a first cracking unit for first cracking treatment, wherein the first cracking treatment is carried out under an anaerobic condition, inputting protective gas into the first cracking unit through the gas input port, purging the first slurry, and discharging gas in the first cracking treatment process through the gas output port; the temperature in the first cracking unit is 220-380 ℃, and at least comprises two temperature areas, wherein the temperature of the temperature area close to the inlet side is lower than that of the temperature area close to the outlet side, and the temperature difference between the two adjacent temperature areas is not lower than 20 ℃;

Inputting the second slurry output by the first cracking unit into a second cracking unit for second cracking treatment, wherein the temperature of the second cracking unit is 420-550 ℃;

And (3) enabling the treated product obtained after the second cracking treatment to enter a gas-liquid separation unit for gas-liquid separation, collecting liquid materials, enabling the liquid materials to enter a fractionation unit for fractionation treatment, inputting cracked tail oil obtained after fractionation into a mixing unit, and mixing the cracked tail oil with pretreated waste plastics.

2. The method of claim 1, wherein the PVC content of the waste plastic is no more than 20%.

3. The method according to claim 1, wherein the temperature of the mixing unit is 120-220 ℃.

4. The method of claim 1, wherein the FCC spent catalyst is regenerated for no more than 4 uses.

5. The method according to claim 4, wherein the gas discharged during the first cracking treatment is fed into an absorption liquid, the pH of which is not less than 7.

6. The method of claim 1, wherein the cleavage tail oil has a cleavage temperature of 300-500 ℃.

7. An apparatus for carrying out the method of any one of claims 1-6, wherein the apparatus comprises a pretreatment unit, a mixing unit, a first pyrolysis unit, a second pyrolysis unit, a gas-liquid separation unit, a fractionation unit, and a heating unit, wherein:

The pretreatment unit is used for pretreating the waste plastics;

the mixing unit comprises a waste plastic inlet and a pyrolysis tail oil inlet, wherein the waste plastic inlet is used for inputting pretreated waste plastic, and the pyrolysis tail oil inlet is communicated with at least one outlet of the fractionating unit;

The outlet of the mixing unit is communicated with the material inlet of the first cracking unit, the first cracking unit comprises a slurry conveyer, a gas input port and a gas output port, the slurry conveyer is used for conveying slurry in the first cracking unit to the material outlet, the gas input port is used for conveying protective gas into the first cracking unit, and the gas output port is used for exhausting gas in the first cracking process;

the material outlet of the first cracking unit is communicated with the material inlet of the second cracking unit, a catalyst storage is arranged in the second cracking unit, and an FCC spent catalyst is stored in the catalyst storage;

The material outlet of the second cracking unit is communicated with the inlet of the gas-liquid separation unit, the liquid phase outlet of the gas-liquid separation unit is communicated with the inlet of the fractionation unit, and at least one outlet of the fractionation unit is communicated with the pyrolysis tail oil inlet;

the heating unit is used for controlling the temperatures in the mixing unit, the first cracking unit and the second cracking unit, and realizing that the first cracking unit comprises at least two temperature areas.

8. The apparatus of claim 7, wherein the catalyst reservoir has an inner diameter D1 and the second cracking unit has an inner diameter D2, 1/2.ltoreq.D1/D2.ltoreq.2/3.

9. The apparatus of claim 7, wherein a cleaner is further provided in the second pyrolysis unit, the cleaner being provided at an inner wall of the second pyrolysis unit, and a waste output for discharging waste residue generated during the second pyrolysis process.

10. The apparatus of claim 7, further comprising an absorption unit in communication with the gas outlet of the first pyrolysis unit.