WO2022067882A1

WO2022067882A1 - System and process of industrial continuous cracking of mixed waste plastics according to class

Info

Publication number: WO2022067882A1
Application number: PCT/CN2020/120684
Authority: WO
Inventors: 汪传生; 田晓龙; 卫健; 汪国春; 平伟; 李文昱; 李绍明; 张德伟; 边慧光; 郝国强; 李利; 郭磊; 尹凤福; 陈宏波; 韩雯雯; 刘海超; 梁辉; 曹梦龙; 徐东彦; 毕海胜
Original assignee: 无锡金球机械有限公司; 青岛科技大学
Priority date: 2020-09-29
Filing date: 2020-10-13
Publication date: 2022-04-07
Also published as: CN112251251A

Abstract

The present invention relates to a system and process of industrial continuous cracking of mixed waste plastics according to class, the system comprising: an extrusion dryer; first and second stage lifting screw conveyors; a catalytic mixing cylinder; a semi-plasticizing feeder; first, second and third stage cracking reaction furnaces; slag discharging first, second and third stage screws; a separator; a slag storage tank; first, second and third basket-type filters; first, second and third stage settling towers; air-cooling first, second and third heat exchangers; water-cooling first, second and third stage heat exchangers; first, second and third stage gas-liquid separation tanks; first, second and third oil tanks; a non-condensable combustible gas purifier; a tail gas treatment module; a combustion chamber; and a combustor. In the present invention, according to the characteristics of different types of plastic and different cracking temperatures, a method for cracking mixed plastics according to class is provided, and the economic value added of the product of cracking is increased by independently recycling a cracked oil product; in addition, energy consumption during the cracking process is reduced by means of the recycling combustion of non-condensable combustible gas and the recycling of high-temperature waste heat, and waste gas passes through multiple purification steps, thus preventing environmental pollution.

Description

Mixed waste plastic industry continuous pyrolysis system and process

technical field

The invention belongs to the technical field of solid waste resource utilization, in particular to a mixed waste plastics industrial continuous classification-by-class pyrolysis system and process.

Background technique

With the development of my country's plastic industry and the improvement of residents' consumption level, plastic products are widely used in industrial production and life, from industrial and agricultural production to clothing, food, housing and transportation, plastic products are everywhere. However, the pollution of waste plastics after use is becoming more and more serious. These plastic wastes will not absorb water and rot, and are not easily digested and decomposed by soil microorganisms. When ignited, they will release a large amount of toxic substances, pollute the air, and directly endanger human health. In addition, a large number of household plastic film fragments are mixed into the soil, which will block the water and air passages in the soil layer, block the expansion and extension of the root system of crops, and gradually turn the fertile fields into dead soil, resulting in successive years of yield reduction. Therefore, how to recycle and utilize waste plastics has become a major issue that countries around the world pay attention to.

According to the relevant data of the National Bureau of Statistics, the total plastic consumption in my country in 2012 was about 54.6737 million tons, while the waste rate of plastic products in China was 45% to 55%. China's plastic consumption is increasing year by year, until 2017, the data showed that the total consumption of my country's plastic industry reached 75.155 million tons, ranking the forefront of the world. Due to the country's further implementation of restrictive policies such as the plastic restriction order, the total plastic production in 2018 declined, but it was also at a high level of 60.421 million tons, accounting for about 15% of the solid waste content.

At present, there are several ways to deal with waste plastics in my country: the first is recycled plastic made of plastic particles, which requires high-quality plastics such as beverage bottles; the second is direct incineration or landfill. The treatment method is simple but causes serious pollution to the environment; the third is to recycle to generate fuel oil, which does not require high plastic quality and can create better social and economic benefits. In particular, waste plastics in domestic waste and obsolete waste cannot be sorted and reused, and can only be processed by cracking, incineration and other methods.

Cracking can convert waste plastics into oil rich in aromatic hydrocarbons, gas with high combustion value and reusable carbon rods, and has become the most effective way to recycle waste plastics in domestic waste and stale waste. However, due to the complex composition of waste plastics in domestic garbage and stale garbage, which contains a large amount of leachate, mud, bricks and other components, the difficulty of continuous cracking is aggravated; It is a flammable and explosive gas, which makes it difficult to guarantee the safety of the cracking process, which makes the industrial application of cracking difficult. In addition, the current cracking technology does not distinguish between the types of raw materials, and they all use a single cracking temperature for cracking, resulting in cracked products. The composition is complex, and it is impossible to extract valuable key materials from the cracked products, resulting in the low value of the cracked oil, which makes the cracking manufacturers have no economic benefits. accomplish.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the deficiencies in the prior art, and to provide a mixed waste plastic industrial continuous cracking system and process that can improve the economic added value of recovered oil bottles, reduce energy consumption, and avoid environmental pollution.

According to the technical scheme provided by the present invention, the mixed waste plastics industrial continuous pyrolysis system includes an extrusion dryer, a first-stage lifting screw conveyor, a catalytic mixing barrel, a second-stage lifting screw conveyor, a semi-plasticizing Feeder, primary cracking reactor, secondary cracking reactor, tertiary cracking reactor, slag discharge primary screw, slag discharge secondary screw, slag discharge tertiary screw, slag storage tank, separator, first Basket filter, second basket filter, third basket filter, primary settling tower, air-cooled primary heat exchanger, water-cooled primary heat exchanger, primary gas-liquid separation tank, secondary settling tower, Air-cooled secondary heat exchanger, water-cooled secondary heat exchanger, secondary gas-liquid separation tank, tertiary settling tower, air-cooled tertiary heat exchanger, water-cooled tertiary heat exchanger, tertiary gas-liquid separation tank, primary oil Tank, second oil tank, third oil tank, non-condensable combustible gas purifier, exhaust gas treatment module, combustion chamber and burner;

The plastic outlet of the extrusion dryer is connected with the plastic inlet of the first-stage lifting screw conveyor, the plastic outlet of the first-stage lifting screw conveyor is connected with the plastic inlet of the catalytic mixing barrel, and the plastic outlet of the catalytic mixing barrel is connected with the plastic inlet of the catalytic mixing barrel. The plastic inlet of the secondary lifting screw conveyor is connected, the plastic outlet of the secondary lifting screw conveyor is connected with the plastic inlet of the semi-plasticizing feeder, and the plastic outlet of the semi-plasticizing feeder is connected with the plastic outlet of the primary cracking reactor. The plastic inlet is connected, the plastic outlet of the primary cracking reactor is connected with the plastic inlet of the secondary cracking reactor, the plastic outlet of the secondary cracking reactor is connected with the plastic inlet of the third-level cracking reactor, and the third-level cracking reactor is connected with the plastic inlet. The slag outlet of the separator is connected with the slag inlet of the separator, the anti-coking ball outlet of the separator is connected with the anti-coking ball inlet of the first-stage cracking reaction furnace, and the slag outlet of the separator is connected with the slag material of the first-stage slagging spiral. The inlets are connected, the slag material outlet of the slag discharge primary spiral is connected with the slag material inlet of the slag discharge secondary spiral, and the slag material outlet of the slag discharge secondary spiral is connected with the slag material inlet of the slag discharge tertiary spiral. The slag outlet of the three-stage screw is connected to the slag inlet of the slag storage tank;

The waste gas outlet of the first-stage cracking reactor, the waste gas outlet of the second-stage cracking reactor, the waste gas outlet of the third-stage cracking reactor, and the waste gas outlet of the extrusion dryer are all connected to the waste gas inlet of the tail gas treatment module. The processing module includes filter bag filter, surface cooler, UV photocatalytic furnace and activated carbon box;

The oil and gas outlet of the first-stage cracking reaction furnace is connected with the oil and gas inlet of the third basket filter, the oil and gas outlet of the third basket filter is connected with the oil and gas inlet of the third-stage sedimentation tower, and the oil of the third-stage sedimentation tower is connected. The outlet is connected to the oil inlet of the third oil tank, the oil and gas outlet of the three-stage sedimentation tower is connected to the oil and gas inlet of the air-cooled three-stage heat exchanger, and the oil and gas outlet of the air-cooled three-stage heat exchanger is connected to the water-cooled three-stage heat exchanger. The oil and gas inlet is connected, the oil and gas outlet of the water-cooled three-stage heat exchanger is connected with the oil and gas inlet of the third-stage gas-liquid separation tank, and the oil-liquid outlet of the third-stage gas-liquid separation tank is connected with the oil-liquid inlet of the third oil tank;

The oil and gas outlet of the two-stage cracking reaction furnace is connected to the oil and gas inlet of the first basket filter, the oil and gas outlet of the first basket filter is connected to the oil and gas inlet of the first-stage sedimentation tower, and the oil of the first-stage sedimentation tower is connected. The outlet is connected to the oil inlet of the oil tank, the oil and gas outlet of the primary settling tower is connected to the oil and gas inlet of the air-cooled primary heat exchanger, and the oil and gas outlet of the air-cooled primary heat exchanger is connected to the oil and gas inlet of the water-cooled primary heat exchanger. connected, the oil and gas outlet of the water-cooled primary heat exchanger is connected with the oil and gas inlet of the primary gas-liquid separation tank, and the oil outlet of the primary gas-liquid separation tank is connected with the oil inlet of the first oil tank;

The oil and gas outlet of the three-stage cracking reaction furnace is connected to the oil and gas inlet of the second basket filter, the oil and gas outlet of the second basket filter is connected to the oil and gas inlet of the secondary settling tower, and the oil of the secondary settling tower is connected. The outlet is connected to the oil inlet of the oil tank, the oil and gas outlet of the secondary settling tower is connected to the oil and gas inlet of the air-cooled secondary heat exchanger, and the oil and gas outlet of the air-cooled secondary heat exchanger is connected to the oil and gas inlet of the water-cooled secondary heat exchanger. connected, the oil and gas outlet of the water-cooled secondary heat exchanger is connected with the oil and gas inlet of the secondary gas-liquid separation tank, and the oil outlet of the secondary gas-liquid separation tank is connected with the oil inlet of the second oil tank;

The non-condensable combustible gas outlet of the primary gas-liquid separation tank, the non-condensable combustible gas outlet of the secondary gas-liquid separation tank, the non-condensable combustible gas outlet of the third-level gas-liquid separation tank, and the non-condensable combustible gas outlet of the first oil tank The outlet, the non-condensable combustible gas outlet of the second oil tank and the non-condensable combustible gas outlet of the third oil tank are connected in parallel with the non-condensable combustible gas inlet of the non-condensable combustible gas purifier. The combustible gas outlet is connected to the non-condensable combustible gas inlet of the burner, the natural gas outlet of the natural gas supply station is connected to the natural gas inlet of the burner, the burner is fixed on the combustion chamber, and the high-temperature flue gas outlet of the combustion chamber is connected to a The high temperature flue gas inlet of the primary cracking reactor, the high temperature flue gas inlet of the secondary cracking reactor and the high temperature flue gas inlet of the tertiary cracking reactor are connected.

Preferably, the outer sides of the furnace bodies of the first-level cracking reactor, the second-level cracking reactor and the third-level cracking reactor are all surrounded by refractory bricks and covered with thermal insulation materials for thermal insulation.

Preferably, the outer jacket of the first-stage slag discharge spiral is provided with a circulating water cooling structure.

Preferably, the pipeline between the non-condensable combustible gas outlet of the non-condensable combustible gas purifier and the non-condensable combustible gas inlet of the burner is provided with a jacket insulation structure.

Preferably, the pipeline between the oil and gas outlet of the primary cracking reaction furnace and the oil and gas inlet of the third basket filter, the pipeline between the oil and gas outlet of the secondary cracking reactor and the oil and gas inlet of the first basket filter And the pipelines between the oil and gas outlet of the three-stage cracking reactor and the oil and gas inlet of the second basket filter are made of 316L stainless steel.

An industrial continuous cracking process of mixed waste plastics by class comprises the following steps:

(1) Dehydration and pre-plasticization: (1) Dehydration and pre-plasticization: The extrusion dryer, the first-level lifting screw conveyor, the catalytic mixing barrel, the second-level lifting screw conveyor and the semi-plasticizing feeder are heated by infrared heating When the temperature reaches 100-150°C, the mixed waste plastic first enters the extrusion dryer, and the waste plastic is dehydrated under the extrusion action of the dewatering screw in the extrusion dryer. It is transported to the catalytic mixing barrel, and the extruded waste plastic enters the catalytic mixing barrel and will instantly open and fluff, thereby releasing the moisture that has not been removed during the extrusion process; at the same time, the catalyst is also added in the catalytic mixing barrel, and is in the catalytic mixing barrel. Under the action of the conical screw of the mixing barrel, the mixed waste plastics and the catalyst are uniformly mixed, and then enter the semi-plasticizing feeder through the secondary lifting screw conveyor, and the waste plastics are converted into semi-plasticizing state by heating up and prevent The coking balls enter the primary cracking reactor together;

(2) Pyrolysis by type: in the early stage of the cracking reaction, the high-temperature flue gas at 1000-1200℃ is generated from the purchased natural gas and burned by the burner, which is the first-level cracking reactor, the second-level cracking reactor and the third-level cracking reactor. Heat supply; wherein the pyrolysis temperature of the primary pyrolysis reactor is controlled to be 300 to 350°C by the fan opening to realize the cracking of PVC plastic in the mixed waste plastics; the pyrolysis temperature of the secondary pyrolysis reactor is controlled by the fan to be 400 to 450°C ℃, realize the cracking of PP and PE plastics in the mixed waste plastics; control the pyrolysis temperature of the three-stage cracking reaction furnace to be 500-550℃ through the fan opening, realize the cracking of ABS plastics in the mixed waste plastics;

(3) Slag discharge: Slag discharge: the carbon black and anti-coking balls produced by the pyrolysis of the three-stage pyrolysis furnace first enter the separator, and the anti-coking balls separated by the separator are returned to the first-stage pyrolysis reactor, and the The carbon black enters the first-stage slag discharge screw, enters the second-stage slag discharge screw under the lifting of the first-stage slag discharge screw, and then continues to be promoted to the third-stage slag discharge screw. storage tank storage;

(4) Oil and gas recovery: The oil and gas generated by the first-level cracking reactor first pass through the third basket filter to remove the solid ash, and then enter the third-stage sedimentation tower to further remove the solid ash in the oil and gas, among which the components with larger molecular chains are It will also be condensed in the three-stage sedimentation tower, and the uncondensed oil and gas enters the air-cooled three-stage heat exchanger, and then enters the water-cooled three-stage heat exchanger. Most of the oil in the oil and gas is exchanged in the air-cooled three-stage heat exchanger and the water-cooled three-stage heat exchanger. The condensed oil and non-condensable combustible gas enter the three-stage gas-liquid separation tank to realize oil and gas separation, and the pyrolysis oil is collected and stored in the third oil tank;

The oil and gas generated by the two-stage cracking reactor first pass through the first basket filter to remove the solid ash, and then enter the first-stage settling tower to further remove the solid ash in the oil and gas. It will be condensed, and the uncondensed oil and gas enters the air-cooled primary heat exchanger, and then enters the water-cooled primary heat exchanger. Most of the oil in the oil and gas is condensed in the air-cooled primary heat exchanger and the water-cooled primary heat exchanger. , the condensed oil and non-condensable combustible gas enter the first-level gas-liquid separation tank to achieve oil and gas separation, and the pyrolysis oil is collected and stored in the first oil tank;

The oil and gas generated by the three-stage cracking reactor first pass through the second basket filter to remove the solid ash in it, and then enter the secondary settling tower to further remove the solid ash in the oil and gas. The components with larger molecular chains are also removed in the secondary settling tower. It will be condensed, and the uncondensed oil and gas enters the air-cooled secondary heat exchanger, and then enters the water-cooled secondary heat exchanger. Most of the oil in the oil and gas is condensed in the air-cooled secondary heat exchanger and the water-cooled secondary heat exchanger. , the condensed oil and non-condensable combustible gas enter the secondary gas-liquid separation tank to achieve oil and gas separation, and the pyrolysis oil is collected and stored in the second oil tank;

(5) Non-condensable combustible gas combustion: The non-condensable combustible gas separated by the first-level gas-liquid separation tank, the second-level gas-liquid separation tank and the third-level gas-liquid separation tank is processed by the non-condensable combustible gas purifier and returned to the burner for combustion , providing high temperature flue gas for the first-level cracking reactor, the second-level cracking reactor and the third-level cracking reactor through the combustion chamber;

(6) Exhaust gas treatment: The exhaust gas generated during the dehydration process of the extrusion dryer and the exhaust gas generated by the combustion of non-condensable combustible gas are connected to the exhaust gas treatment module, passed into the filter bag filter to remove dust particles, and then entered into the surface cooler for cooling , the water vapor condenses into liquid water and is discharged, and then enters the UV photocatalytic furnace to destroy the molecular structure of the exhaust gas, then enters the activated carbon box to absorb pollutants, and finally discharges the purified exhaust gas through the fan.

The present invention has the following advantages:

1. The multi-stage pyrolysis reaction temperature is set according to the types of various plastics in the mixed waste plastics, so as to realize the separate pyrolysis of each type of waste plastics in each pyrolysis stage, so as to realize the controlled breaking of molecular bonds based on temperature control and realize the realization of various plastics. Fractional cracking;

Among them, chlorine-containing waste plastics (mainly referring to PVC) will seriously corrode equipment and affect the quality of oil products. However, due to the characteristics of PVC materials, its decomposition temperature is the lowest. Therefore, through the invented process, chlorine-containing waste plastics can be preferentially separated and cracked. Oil products are treated separately without sorting, and chlorine-containing compounds can be removed online;

The invention realizes the separate recovery of various oil products, and can be used independently according to the components of various plastic oil products, thereby increasing its economic added value;

The invention realizes that the mixed plastic is free from sorting and cleaning, and avoids secondary pollution in the pretreatment process.

2. In order to strengthen the heat and mass transfer in the cracking process of waste plastics, the present invention develops a high-enthalpy medium (ie, anti-coking ball) internal circulation method, which mainly refers to adding anti-corrosion agents of different sizes and shapes during the cracking process. Coking balls, enhance the heat transfer effect in the cracking process.

3. In the present invention, the oil and gas is decomposed and recovered by graded condensation, and the condensation parts of all levels realize the separation of oil and gas and the collection of oil products through solid sedimentation, condensation, gas-liquid separation and other procedures.

4. The present invention uses high temperature flue gas to heat the cracking reactors at all levels, and controls the temperature of the cracking reactors at all levels by controlling the fan displacement; and reuses the used flue gas to reduce energy consumption.

Description of drawings

FIG. 1 is a schematic diagram of the arrangement of the system of the present invention.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments.

An industrial continuous cracking system for mixed waste plastics by class, which includes an extrusion dryer 1, a primary lifting screw conveyor 2, a catalytic mixing barrel 3, a secondary lifting screw conveyor 4, and a semi-plasticizing feeder 5 , first-level cracking reactor 6, second-level cracking reactor 7, third-level cracking reactor 8, slagging first-level screw 9, slag-discharging second-level screw 10, slag-discharging third-level screw 11, slag storage tank 12, separation 13, the first basket filter 141, the second basket filter 142, the third basket filter 143, the primary settling tower 15, the air-cooled primary heat exchanger 16, the water-cooled primary heat exchanger 17, a Stage gas-liquid separation tank 18, secondary settling tower 19, air-cooled secondary heat exchanger 20, water-cooled secondary heat exchanger 21, secondary gas-liquid separation tank 22, tertiary settling tower 23, air-cooled tertiary heat exchanger 24 , water-cooled three-stage heat exchanger 25, three-stage gas-liquid separation tank 26, first oil tank 271, second oil tank 272, third oil tank 273, non-condensable combustible gas purifier 28, exhaust gas treatment module 29, combustion chamber 30 and burner 31;

The plastic outlet of the extrusion dryer 1 is connected to the plastic inlet of the first-stage lifting screw conveyor 2, the plastic outlet of the first-stage lifting screw conveyor 2 is connected to the plastic inlet of the catalytic mixing barrel 3, and the catalytic mixing barrel is connected. The plastic outlet of 3 is connected to the plastic inlet of the secondary lifting screw conveyor 4, and the plastic outlet of the secondary lifting screw conveyor 4 is connected to the plastic inlet of the semi-plasticizing feeder 5. The plastic outlet is connected with the plastic inlet of the primary cracking reactor 6, the plastic outlet of the primary cracking reactor 6 is connected with the plastic inlet of the secondary cracking reactor 7, and the plastic outlet of the secondary cracking reactor 7 is connected with the third-level cracking. The plastic inlet of the reaction furnace 8 is connected, the slag material outlet of the three-stage cracking reaction furnace 8 is connected with the slag material inlet of the separator 13, and the anti-coking ball outlet of the separator 13 is connected with the anti-coking ball inlet of the first-stage cracking reaction furnace 6. The slag outlet of the separator 13 is connected to the slag inlet of the slag discharge primary screw 9, the slag outlet of the slag discharge primary screw 9 is connected with the slag inlet of the slag discharge secondary screw 10, and the slag discharge is connected. The slag material outlet of the secondary screw 10 is connected with the slag material inlet of the slag discharge tertiary screw 11, and the slag material outlet of the slag discharge tertiary screw 11 is connected with the slag material inlet of the slag material storage tank 12;

The waste gas outlet of the first-stage cracking reaction furnace 6, the waste gas outlet of the second-stage cracking reaction furnace 7, the waste gas outlet of the third-stage cracking reaction furnace 8 and the waste gas outlet of the extrusion dryer 1 are all in phase with the waste gas inlet of the tail gas treatment module 29. Then, the exhaust gas treatment module 29 includes a filter bag filter, a surface cooler, a UV photocatalytic furnace and an activated carbon box;

The oil and gas outlet of the first-stage cracking reaction furnace 6 is connected with the oil and gas inlet of the third basket filter 143, and the oil and gas outlet of the third basket filter 143 is connected with the oil and gas inlet of the three-stage sedimentation tower 23, and the three-stage sedimentation The oil outlet of the tower 23 is connected to the oil inlet of the third oil tank 273, the oil and gas outlet of the three-stage sedimentation tower 23 is connected to the oil and gas inlet of the air-cooled three-stage heat exchanger 24, and the oil and gas of the air-cooled three-stage heat exchanger 24 is connected. The outlet is connected to the oil and gas inlet of the water-cooled three-stage heat exchanger 25, the oil and gas outlet of the water-cooled three-stage heat exchanger 25 is connected to the oil and gas inlet of the three-stage gas-liquid separation tank 26, and the oil-liquid outlet of the three-stage gas-liquid separation tank 26 Connected with the oil inlet of the third oil tank 273;

The oil and gas outlet of the secondary cracking reactor 7 is connected to the oil and gas inlet of the first basket filter 141, and the oil and gas outlet of the first basket filter 141 is connected to the oil and gas inlet of the first-stage sedimentation tower 15, and the first-stage sedimentation The oil outlet of the tower 15 is connected to the oil inlet of the oil tank 27, the oil and gas outlet of the first-stage sedimentation tower 15 is connected to the oil and gas inlet of the air-cooled primary heat exchanger 16, and the oil and gas outlet of the air-cooled primary heat exchanger 16 is connected to The oil and gas inlet of the water-cooled primary heat exchanger 17 is connected, the oil and gas outlet of the water-cooled primary heat exchanger 17 is connected with the oil and gas inlet of the primary gas-liquid separation tank 18, and the oil outlet of the primary gas-liquid separation tank 18 is connected to the first-stage gas-liquid separation tank 18. The oil inlet of an oil tank 271 is connected;

The oil and gas outlet of the three-stage cracking reaction furnace 8 is connected with the oil and gas inlet of the second basket filter 142, and the oil and gas outlet of the second basket filter 142 is connected with the oil and gas inlet of the secondary settling tower 19, and the secondary settling The oil outlet of the tower 19 is connected to the oil inlet of the oil tank 27, the oil and gas outlet of the secondary settling tower 19 is connected to the oil and gas inlet of the air-cooled secondary heat exchanger 20, and the oil and gas outlet of the air-cooled secondary heat exchanger 20 is connected to the oil and gas inlet of the air-cooled secondary heat exchanger 20. The oil and gas inlet of the water-cooled secondary heat exchanger 21 is connected, the oil and gas outlet of the water-cooled secondary heat exchanger 21 is connected with the oil and gas inlet of the secondary gas-liquid separation tank 22, and the oil outlet of the secondary gas-liquid separation tank 22 is connected to the second gas-liquid separation tank 22. The oil inlet of the second oil tank 272 is connected;

The non-condensable combustible gas outlet of the primary gas-liquid separation tank 18, the non-condensable combustible gas outlet of the secondary gas-liquid separation tank 22, the non-condensable combustible gas outlet of the tertiary gas-liquid separation tank 26, the The non-condensable combustible gas outlet, the non-condensable combustible gas outlet of the second oil tank 272 and the non-condensable combustible gas outlet of the third oil tank 273 are connected in parallel with the non-condensable combustible gas inlet of the non-condensable combustible gas purifier 28, and the non-condensable combustible gas outlet is connected in parallel. The non-condensable combustible gas outlet of the combustible gas purifier 28 is connected to the non-condensable combustible gas inlet of the burner 31, the natural gas outlet of the natural gas supply station 32 is connected to the natural gas inlet of the burner 31, and the burner 31 is fixed in the combustion chamber 30. Above, the high temperature flue gas outlet of the combustion chamber 30 is connected to the high temperature flue gas inlet of the primary cracking reactor 6, the high temperature flue gas inlet of the secondary cracking reactor 7 and the high temperature flue gas inlet of the tertiary cracking reactor 8. .

The outer sides of the first-stage cracking reaction furnace 6, the second-stage cracking reaction furnace 7 and the third-stage cracking reaction furnace 8 are all surrounded by refractory bricks and covered with heat insulating materials for heat preservation.

The outer jacket of the first-stage slag discharge screw 9 is provided with a circulating water cooling structure.

The pipeline between the non-condensable combustible gas outlet of the non-condensable combustible gas purifier 28 and the non-condensable combustible gas inlet of the burner 31 is provided with a jacket insulation structure.

The pipeline between the oil and gas outlet of the primary cracking reaction furnace 6 and the oil and gas inlet of the third basket filter 143, the oil and gas outlet of the secondary cracking reactor 7 and the oil and gas inlet of the first basket filter 141. The pipeline and the pipeline between the oil and gas outlet of the three-stage cracking reaction furnace 8 and the oil and gas inlet of the second basket filter 142 are all made of 316L stainless steel.

(1) Dehydration and pre-plasticization: extrusion dryer 1, first-level lifting screw conveyor 2, catalytic mixing barrel 3, second-level lifting screw conveyor 4 and semi-plasticizing feeder 5 are heated to 100~ At 150°C, the mixed waste plastic first enters the extrusion dryer 1, and the waste plastic is dehydrated under the extrusion action of the dewatering screw in the extrusion dryer 1, and the dehydrated waste plastic is lifted by the first-level screw conveyor 2 It is transported to the catalytic mixing barrel 3, and the extruded waste plastic enters the catalytic mixing barrel 3 and will instantly open and fluff, thereby releasing the moisture that is not removed during the extrusion process; at the same time, the catalyst is also added in the catalytic mixing barrel, and Under the action of the conical spiral of the catalytic mixing barrel 3, the mixed waste plastic and the catalyst are uniformly mixed, and then enter the semi-plasticizing feeder 5 through the secondary lifting screw conveyor 4, and convert the waste plastic into semi-plastic by heating up. The anti-coking balls enter the first-stage cracking reaction furnace 6 together with the anti-coking balls; wherein, the anti-coking balls are ceramic particles with a particle size of 10-35 mm and different shapes;

(2) Pyrolysis by type: in the early stage of the cracking reaction, the high-temperature flue gas of 1000-1200°C generated after the natural gas is purchased and burned by the burner 31 is the first-level cracking reactor 6, the second-level cracking reactor 7 and the third-level cracking reactor 6. The cracking reaction furnace 8 provides heat; wherein the cracking temperature of the primary cracking reaction furnace 6 is controlled to be 300-350° C. by the fan opening, so as to realize the cracking of PVC plastics in the mixed waste plastics; The pyrolysis temperature is 400-450°C to realize the pyrolysis of PP and PE plastics in the mixed waste plastics; the pyrolysis temperature of the three-stage pyrolysis reactor 8 is controlled to be 500-550°C by the fan opening to realize the pyrolysis of ABS plastics in the mixed waste plastics;

(3) Slag discharge: the carbon black and anti-coking balls produced by the pyrolysis of the three-stage pyrolysis furnace 8 first enter the separator 13, and the anti-coking balls separated by the separator 13 are returned to the first-stage cracking reaction furnace 6, and the separator 13 separates The discharged carbon black enters the first-stage slag discharge screw 9, enters the second-stage slag discharge screw 10 under the lifting of the first-stage slag discharge screw 9, and then continues to ascend to the third-stage slag discharge screw 11. The stage screw 11 is sent to the slag storage tank 12 for storage;

(4) Oil and gas recovery: the oil and gas generated by the primary cracking reactor 6 first passes through the third basket filter 143 to remove the solid ash content therein, and then enters the tertiary settling tower 23 to further remove the solid ash content in the oil and gas, wherein the molecular chain is relatively Large components will also be condensed in the three-stage sedimentation tower 23, and the uncondensed oil and gas enters the air-cooled three-stage heat exchanger 24, and then enters the water-cooled three-stage heat exchanger 25. Most of the oil in the oil and gas is exchanged in the air-cooled three-stage heat exchanger. The condensed oil and non-condensable combustible gas enter the three-stage gas-liquid separation tank 26 to realize oil and gas separation, and the pyrolysis oil is collected and stored in the third oil tank 273;

The oil and gas generated by the secondary cracking reactor 7 first passes through the first basket filter 141 to remove the solid ash content, and then enters the primary settling tower 15 to further remove the solid ash content in the oil and gas, wherein the components with larger molecular chains are in the first stage. The sedimentation tower 15 will also be condensed, and the uncondensed oil and gas enter the air-cooled primary heat exchanger 16, and then enter the water-cooled primary heat exchanger 17. Most of the oil in the oil and gas is in the air-cooled primary heat exchanger 16 and the water-cooled primary heat exchanger 17 The heat exchanger 17 is condensed out, the condensed oil and the non-condensable combustible gas enter the primary gas-liquid separation tank 18 to realize oil and gas separation, and the pyrolysis oil is collected and stored in the first oil tank 271;

The oil and gas generated by the three-stage cracking reactor 8 first passes through the second basket filter 142 to remove the solid ash, and then enters the second-stage settling tower 19 to further remove the solid ash in the oil and gas, wherein the components with larger molecular chains are in the second stage. The sedimentation tower 19 will also be condensed, and the uncondensed oil and gas enter the air-cooled secondary heat exchanger 20, and then enter the water-cooled secondary heat exchanger 21. Most of the oil in the oil and gas is in the air-cooled secondary heat exchanger 20 and the water-cooled secondary heat exchanger The heat exchanger 21 is condensed out, the condensed oil and the non-condensable combustible gas enter the secondary gas-liquid separation tank 22 to realize oil and gas separation, and the pyrolysis oil is collected and stored in the second oil tank 272;

(5) Non-condensable combustible gas combustion: the non-condensable combustible gas separated by the first-level gas-liquid separation tank 18, the second-level gas-liquid separation tank 22 and the third-level gas-liquid separation tank 26 is processed by the non-condensable combustible gas purifier 28 and returned to When the burner 31 burns, the combustion chamber 30 provides high-temperature flue gas for the first-level cracking reactor 6, the second-level cracking reactor 7 and the third-level cracking reactor 8;

(6) Exhaust gas treatment: the exhaust gas generated during the dehydration process of the extrusion dryer 1 and the exhaust gas generated by the combustion of non-condensable combustible gas are connected to the exhaust gas treatment module 29, passed into the filter bag filter to remove dust particles, and then into the surface cooler After cooling, the water vapor is condensed into liquid water and discharged, and then enters the UV photocatalytic furnace to destroy the molecular structure of the exhaust gas, then enters the activated carbon box to absorb pollutants, and finally discharges the purified exhaust gas through the fan.

If the mixed waste plastics contain special waste plastics with high cracking temperature such as engineering plastics, it is necessary to add a four-stage cracking reaction furnace, and control the cracking temperature of the four-stage cracking reaction furnace to 700-750 °C through the fan opening to realize mixed plastics. Special plastics in the cracking, so as to meet the needs of mixed plastics cracking by type.

In the dehydration and pre-plasticizing step of the present invention, the mixed waste plastics may be waste plastics separated from domestic wastes, or waste plastics from stale garbage dug up in garbage factories. After preliminary treatment, these mixed plastics are It is sent to the cracking reaction dehydration and drying device. The dehydration and softening pretreatment equipment mainly includes extrusion dryer 1, primary lifting screw conveyor 2, catalytic mixing barrel 3, secondary lifting screw conveyor 4, and semi-plasticizing feeder. 5. After the waste plastic added to the feeding port enters the dehydration extruder 1, most of the liquid water is removed by the extrusion action of the dehydration screw in the dehydration extruder 1; a rotary cutter head is installed at the end of the dehydration extruder 1 , the waste plastics can be cut into pieces, and the pieces of waste plastics fall into the storage bin of the dewatering extruder 1 to be fluffy instantly, so that the unremoved water in the waste plastics overflows, and the pieces of waste plastics are lifted by the screw conveyor at the first level. Under the action of 2, it is transported to the catalytic mixing barrel 3. In the catalytic mixing barrel 3, catalysts such as ZSM-5 molecular sieve, Y-type molecular sieve, mordenite, viscous clay or metal oxide can be added, and then the secondary lifting screw The conveyor 4 is lifted to the hopper of the semi-plasticizing feeder 5, and the semi-plasticizing process is performed in the semi-plasticizing feeder 5 to prepare for subsequent thermal cracking. The liquid water extruded from the waste plastics is discharged into the external collection device through the drainage hole of the barrel, the drainage groove of the machine head, and the drainage hole of the feed pipe of the machine head, and the gaseous water is discharged from the exhaust pipe through the exhaust network and enters the exhaust gas treatment module to be processed. The process of the invention combines high-compression water squeezing and enhanced drying and conveying, has good dehydration effect, energy saving and environmental protection, and has good application prospects.

Among them, the dewatering screw of the extrusion dryer 1 adopts the design of equidistant and deepening, and the front and rear compression of the screw is relatively large, which can achieve a better dewatering effect.

In the graded pyrolysis step of the present invention, the graded pyrolysis of waste plastics is the core part of the process of the present invention, mainly due to the different compositions of the organic molecular chains of waste plastics and different pyrolysis characteristics, so as to make the initial temperature of pyrolysis and the maximum weight loss of pyrolysis. The rate temperature is different, and the pyrolysis temperature of different regions is set according to the characteristics of these materials, so as to realize their individual pyrolysis.

After the waste plastic has been dehydrated, it has entered a molten state. At this time, it enters the primary cracking reaction furnace 6. The cracking temperature is generally 300 to 350 ° C. At this time, plastics with a lower decomposition temperature, such as PVC, begin to crack, which can realize chlorine-containing plastics. Under the driving action of the double helix, the material passes through the primary cracking reaction furnace 6 and enters the secondary cracking reaction furnace 7, and the cracking temperature is set at 400-450 ° C. Molecular compounds are decomposed. The oil and gas components produced by cracking in this interval are relatively high, and the components of cracked oil products are relatively complex; the waste plastics pass through the secondary cracking reactor 7 and then enter the third-level cracking reactor 8, and the cracking temperature is set at 550~ 650℃, the pyrolysis temperature of this part is relatively high, and it is mainly responsible for the pyrolysis of engineering plastics such as ABS. The oil component produced by this part is relatively low, and the pyrolysis gas component is relatively high. This stage of the reactor is responsible for the energy supply in the cracking process;

During the cracking process, the number of pyrolysis furnaces and the pyrolysis temperature need to be determined according to the type of mixed waste plastics. If there are special plastics in the mixed plastics, it is necessary to increase the number of reactors and increase the final stage pyrolysis temperature.

In the step of grading pyrolysis of the present invention, the anti-coking balls and waste plastics enter the primary cracking reaction furnace 6 together for cracking, and then enter the secondary cracking reaction furnace 7 and the third-level cracking reaction furnace 8 in sequence, and mix and agitate to improve the uniformity of cracking. At the same time, it repeatedly rubs and scratches with the cracker wall and screw fan surface to remove coke and prevent the generation of coke, ensuring the continuous and stable operation of the cracking process.

The cracked ash and anti-coking balls formed by the cracking of waste plastics enter the barrel of the separator, and the anti-coking balls rub against each other under the stirring action of the separator screw, so that the cracked ash attached to the anti-coking balls is detached and discharged through the ash discharge port for cleaning. The clean anti-coking balls are driven by the lifter screw and enter the primary cracking reaction furnace 6 from the outlet of the anti-coking balls for automatic recycling, realizing the automatic separation of the anti-coking balls and the cracked ash formed by waste plastics.

In the slag discharge step of the present invention, high-temperature pyrolysis carbon particles will be left after the waste plastics are cracked, and the continuous output and storage of them is the key to the continuous operation of the whole set of cracking equipment. The process of the invention mainly adopts a water-cooled multi-stage screw conveying and discharging system, which is composed of a slag discharge primary screw 9, a slag discharge secondary screw 10, a slag discharge tertiary screw 11, and a slag material storage tank 12 in series. It has the characteristics of good effect, large storage capacity, good sealing performance and stable operation. It is suitable for the collection, cooling, transportation and storage of various loose materials.

In the oil and gas recovery step of the present invention, the cracked oil is the main product of the cracking of waste plastics, accounting for about 60%. At present, pyrolysis oil is centrally recovered and processed in waste plastic cracking equipment at home and abroad. The quality of oil products varies greatly with the cracking process conditions, the quality stability is poor, and the post-processing cost is high, and it is directly used as fuel oil. Economic benefits are not high.

Different components of waste plastics have different initial cracking temperatures and different cracking intervals during the cracking process. According to the components of waste plastics, the cracking temperature can be selectively set to realize the separate recovery of cracked oil products of different plastic components. Realize the maximum economic benefits of cracked oil products; and can solve the influence of chlorine content in PVC components in waste plastics on the quality of cracked oil products. The cracked oil and gas generated by reactors at all levels needs to be recovered separately, mainly through basket filters. Remove the solid ash in it, and then enter the settling tower to further remove the solid ash in the oil and gas. The components with larger molecular chains will also be condensed in the settling tower, and the uncondensed oil and gas will enter the complete set of heat exchangers. There are two cooling methods: air cooling and water cooling. Most of the oil in the oil and gas is condensed out in the heat exchanger set, and the condensed oil and non-condensable gas enter the gas-liquid separation tank to achieve oil and gas separation; the last three sets of oil and gas recovery devices produce non-condensable oil The combined gas is treated by the non-condensable gas purification device and returned to the combustion furnace for combustion to provide heat energy for the system; the pyrolysis oil produced by the condensation of each stage of the pyrolysis furnace is separately collected and stored in the oil tank, thereby reducing the chlorine content in the subsequent pyrolysis oil. At the same time, the refinement of oil recovery is realized.

In the non-condensable combustible combustion and waste heat recycling step of the present invention, in the continuous cracking process, the flue gas that has been used but is still high temperature is sent to the burner for a little temperature, and then recycled to the primary cracking reactor 6 , Two-stage cracking reaction furnace 7 and three-stage cracking reaction furnace 8, provide the required heat for the cracking of waste plastics, reduce fuel consumption, and reduce the emission of flue gas. At present, the high-temperature flue gas used for heating and cracking waste plastics is generally discharged directly into the atmosphere after passing through the cracker. This method not only pollutes the environment, but also wastes a large amount of flue gas waste heat, resulting in wasted energy.

In the tail gas treatment step of the present invention, the tail gas contains two parts, one part is the waste gas produced by the transportation during the dehydration process, and the other part is the waste gas produced by the combustion of the non-condensable combustible gas. The main cause of pollutants in the exhaust gas after combustion of non-condensable combustible gas is the incomplete combustion of non-condensable combustible gas. The pollutant components include dust particles, SO ₂ , NO _X , HCl, benzopyrene, benzene, non-methane total Hydrocarbons etc. In the process of exhaust gas treatment, the two kinds of exhaust gas are jointly passed into the filter bag filter to remove dust particles, and then enter the surface cooler for cooling, so that the water vapor is condensed into liquid water and discharged. At this time, the water saturation in the gas is relatively high. Therefore, a small part of the exhaust gas is separated from the combustion exhaust gas and mixed with the dedusted and cooled gas in the mixing tank to increase the gas temperature, thereby reducing the water saturation in the gas. The mixed gas enters the UV photocatalytic furnace to destroy the molecular structure of the exhaust gas, then enters the activated carbon box to absorb pollutants, and finally discharges the purified exhaust gas through the fan.

Claims

An industrial continuous cracking system for mixed waste plastics by class, characterized in that it comprises an extrusion dryer (1), a first-stage lifting screw conveyor (2), a catalytic mixing barrel (3), and a second-stage lifting screw conveyor machine (4), semi-plasticizing feeder (5), primary cracking reactor (6), secondary cracking reactor (7), tertiary cracking reactor (8), slag discharge primary screw (9) , slag discharge secondary screw (10), slag discharge tertiary screw (11), slag storage tank (12), separator (13), first basket filter (141), second basket filter ( 142), the third basket filter (143), the primary settling tower (15), the air-cooled primary heat exchanger (16), the water-cooled primary heat exchanger (17), the primary gas-liquid separation tank (18) , secondary settling tower (19), air-cooled secondary heat exchanger (20), water-cooled secondary heat exchanger (21), secondary gas-liquid separation tank (22), tertiary settling tower (23), air-cooled tertiary Heat exchanger (24), water-cooled three-stage heat exchanger (25), three-stage gas-liquid separation tank (26), first oil tank (271), second oil tank (272), third oil tank (273) , a non-condensable combustible gas purifier (28), an exhaust gas treatment module (29), a combustion chamber (30) and a burner (31);

The plastic outlet of the extrusion dryer (1) is connected to the plastic inlet of the first-stage lifting screw conveyor (2), and the plastic outlet of the first-stage lifting screw conveyor (2) is connected to the plastic outlet of the catalytic mixing barrel (3). The inlets are connected, the plastic outlet of the catalytic mixing barrel (3) is connected with the plastic inlet of the secondary lifting screw conveyor (4), and the plastic outlet of the secondary lifting screw conveyor (4) is connected with the semi-plasticizing feeder ( 5) is connected to the plastic inlet, the plastic outlet of the semi-plasticizing feeder (5) is connected to the plastic inlet of the primary cracking reactor (6), and the plastic outlet of the primary cracking reactor (6) is connected to the secondary cracking reactor (6). The plastic inlet of the reaction furnace (7) is connected, the plastic outlet of the second-stage cracking reaction furnace (7) is connected with the plastic inlet of the third-stage cracking reaction furnace (8), and the slag material outlet of the third-stage cracking reaction furnace (8) is connected with the plastic inlet of the third-stage cracking reaction furnace (8). The slag inlet of the separator (13) is connected, the outlet of the anti-coking ball of the separator (13) is connected to the inlet of the anti-coking ball of the first-stage cracking reaction furnace (6), and the outlet of the slag of the separator (13) is connected to the discharger. The slag material inlet of the slag first-stage screw (9) is connected, the slag material outlet of the slag discharge first-stage screw (9) is connected with the slag material inlet of the slag discharge second-stage screw (10), and the slag discharge second-stage screw (10) The slag material outlet of the slag discharge three-stage screw (11) is connected with the slag material inlet of the slag discharge three-stage screw (11), and the slag material outlet of the slag discharge three-stage screw (11) is connected with the slag material inlet of the slag material storage tank (12);

The waste gas outlet of the first-stage cracking reaction furnace (6), the waste gas outlet of the second-stage cracking reaction furnace (7), the waste gas outlet of the third-stage cracking reaction furnace (8) and the waste gas outlet of the extrusion dryer (1) are all the same. The exhaust gas inlets of the exhaust gas treatment module (29) are connected, and the exhaust gas treatment module (29) includes a filter bag filter, a surface cooler, a UV photocatalytic furnace and an activated carbon box;

The oil and gas outlet of the first-stage cracking reactor (6) is connected to the oil and gas inlet of the third basket filter (143), and the oil and gas outlet of the third basket filter (143) is connected to the oil and gas outlet of the third-stage sedimentation tower (23). The oil and gas inlets are connected, the oil outlet of the three-stage sedimentation tower (23) is connected with the oil inlet of the third oil tank (273), and the oil and gas outlet of the three-stage sedimentation tower (23) is connected to the air-cooled three-stage heat exchanger (24). ), the oil and gas inlet of the air-cooled tertiary heat exchanger (24) is connected to the oil and gas inlet of the water-cooled tertiary heat exchanger (25), and the oil and gas outlet of the water-cooled tertiary heat exchanger (25) is connected to the oil and gas inlet of the water-cooled tertiary heat exchanger (25). The oil and gas inlets of the gas-liquid separation tank (26) are connected, and the oil-liquid outlet of the third-stage gas-liquid separation tank (26) is connected with the oil-liquid inlet of the third oil tank (273);

The oil and gas outlet of the secondary cracking reactor (7) is connected to the oil and gas inlet of the first basket filter (141), and the oil and gas outlet of the first basket filter (141) is connected to the oil and gas outlet of the first-stage sedimentation tower (15). The oil and gas inlets are connected, the oil outlet of the first-stage sedimentation tower (15) is connected with the oil inlet of the oil tank (27), and the oil-gas outlet of the first-stage sedimentation tower (15) is connected with the air-cooled first-stage heat exchanger (16). The oil and gas inlet is connected, the oil and gas outlet of the air-cooled primary heat exchanger (16) is connected with the oil and gas inlet of the water-cooled primary heat exchanger (17), and the oil and gas outlet of the water-cooled primary heat exchanger (17) is connected with the primary gas-liquid The oil and gas inlet of the separation tank (18) is connected, and the oil outlet of the primary gas-liquid separation tank (18) is connected with the oil inlet of the first oil tank (271);

The oil and gas outlet of the three-stage cracking reaction furnace (8) is connected to the oil and gas inlet of the second basket filter (142), and the oil and gas outlet of the second basket filter (142) is connected to the oil and gas outlet of the secondary settling tower (19). The oil and gas inlet is connected, the oil outlet of the secondary settling tower (19) is connected with the oil inlet of the oil tank (27), and the oil and gas outlet of the secondary settling tower (19) is connected with the air-cooled secondary heat exchanger (20). The oil and gas inlet is connected, the oil and gas outlet of the air-cooled secondary heat exchanger (20) is connected with the oil and gas inlet of the water-cooled secondary heat exchanger (21), and the oil and gas outlet of the water-cooled secondary heat exchanger (21) is connected with the secondary gas-liquid The oil and gas inlet of the separation tank (22) is connected, and the oil outlet of the secondary gas-liquid separation tank (22) is connected with the oil inlet of the second oil tank (272);

The non-condensable combustible gas outlet of the primary gas-liquid separation tank (18), the non-condensable combustible gas outlet of the secondary gas-liquid separation tank (22), the non-condensable combustible gas outlet of the tertiary gas-liquid separation tank (26), The non-condensable combustible gas outlet of the first oil tank (271), the non-condensable combustible gas outlet of the second oil tank (272), and the non-condensable combustible gas outlet of the third oil tank (273) are connected in parallel with the non-condensable combustible gas purifier The non-condensable combustible gas inlet of (28) is connected, the non-condensable combustible gas outlet of the non-condensable combustible gas purifier (28) is connected to the non-condensable combustible gas inlet of the burner (31), and the natural gas supply station (32) The natural gas outlet is connected to the natural gas inlet of the burner (31), the burner (31) is fixed on the combustion chamber (30), and the high-temperature flue gas outlet of the combustion chamber (30) is connected to the outlet of the primary cracking reactor (6). The high temperature flue gas inlet, the high temperature flue gas inlet of the secondary cracking reaction furnace (7) and the high temperature flue gas inlet of the tertiary cracking reaction furnace (8) are connected to each other.
The industrial continuous cracking system for mixed waste plastics according to claim 1, characterized in that: the first-level cracking reactor (6), the second-level cracking reactor (7) and the third-level cracking reactor (8) The outside of the furnace body is surrounded by refractory bricks and covered with thermal insulation materials for thermal insulation.
The industrial continuous cracking system for mixed waste plastics according to claim 1, characterized in that: the outer jacket of the first-stage slag discharge screw (9) is provided with a circulating water cooling structure.
The industrial continuous pyrolysis system for mixed waste plastics according to claim 1, characterized in that: the non-condensable combustible gas outlet of the non-condensable combustible gas purifier (28) and the non-condensable combustible gas outlet of the burner (31) The pipes between the inlets are provided with jacket insulation structures.
The industrial continuous cracking system for mixed waste plastics according to claim 1, characterized in that: between the oil and gas outlet of the first-stage cracking reaction furnace (6) and the oil and gas inlet of the third basket filter (143) pipeline, the pipeline between the oil and gas outlet of the secondary cracking reactor (7) and the oil and gas inlet of the first basket filter (141), and the oil and gas outlet of the tertiary cracking reactor (8) and the second basket filter The pipes between the oil and gas inlets of (142) are all made of 316L stainless steel.
A kind of industrial continuous pyrolysis process of mixed waste plastics is characterized by comprising the following steps:

(1) Dehydration and pre-plasticization: extrusion dryer (1), primary lifting screw conveyor (2), catalytic mixing barrel (3), secondary lifting screw conveyor (4) and semi-plasticizing feeder (5) The temperature is raised to 100-150°C by infrared heating, and the mixed waste plastic first enters the extrusion dryer (1), and the waste plastic is dehydrated under the extrusion action of the dewatering screw in the extrusion dryer (1). , the dehydrated waste plastic is transported into the catalytic mixing barrel (3) by the first-stage lifting screw conveyor (2), and the extruded waste plastic enters the catalytic mixing barrel (3) and will instantly open and fluff, thereby releasing The water that is not removed during the extrusion process; at the same time, the catalyst is also added into the catalytic mixing barrel, and under the action of the conical spiral of the catalytic mixing barrel (3), the mixed waste plastic and the catalyst are uniformly mixed, and then the two-stage lifting is carried out. The screw conveyor (4) enters the semi-plasticizing feeder (5), and the waste plastic is transformed into a semi-plasticizing state by heating up and enters the primary cracking reaction furnace (6) together with the anti-coking balls;

(2) Pyrolysis by type: in the early stage of the cracking reaction, the high-temperature flue gas at 1000-1200°C is generated from the purchased natural gas and burned by the burner (31), which is the first-level cracking reactor (6) and the second-level cracking reactor. (7) supplying heat with the third-stage cracking reaction furnace (8); wherein the cracking temperature of the first-stage cracking reaction furnace (6) is controlled to be 300-350° C. by the fan opening, so as to realize the cracking of PVC plastics in the mixed waste plastics; through the fan The pyrolysis temperature of the secondary pyrolysis reactor (7) is controlled to be 400 to 450° C. to realize the cracking of PP and PE plastics in the mixed waste plastics; ～550℃, realize the cracking of ABS plastic in mixed waste plastic;

(3) Slag discharge: the carbon black and anti-coking balls produced by the pyrolysis of the three-stage pyrolysis furnace (8) first enter the separator (13), and the anti-coking balls separated by the separator (13) are returned to the first-stage cracking reaction furnace (6), the carbon black separated by the separator (13) enters the slagging primary screw (9), enters the slag discharging secondary screw (10) under the lifting of the slagging primary screw (9), and then continues to ascend to The slag discharge three-stage screw (11), after cooling the carbon black, is sent to the slag storage tank (12) for storage through the slag discharge three-stage screw (11);

(4) Oil and gas recovery: The oil and gas produced by the primary cracking reactor (6) first passes through the third basket filter (143) to remove the solid ash, and then enters the third-stage sedimentation tower (23) to further remove the solids in the oil and gas. Ash, the components with larger molecular chains will also be condensed in the tertiary settling tower (23), and the uncondensed oil and gas enter the air-cooled tertiary heat exchanger (24), and then enter the water-cooled tertiary heat exchanger (25) , most of the oil in the oil and gas is condensed in the air-cooled three-stage heat exchanger (24) and the water-cooled three-stage heat exchanger (25), and the condensed oil and non-condensable combustible gas enter the three-stage gas-liquid separation tank (26) to realize Oil and gas separation, pyrolysis oil is collected and stored in the third oil tank (273);

The oil and gas generated by the secondary cracking reactor (7) first passes through the first basket filter (141) to remove the solid ash content therein, and then enters the primary settling tower (15) to further remove the solid ash content in the oil and gas, wherein the molecular chain is relatively small. Large components are also condensed in the primary settling tower (15), and the uncondensed oil and gas enters the air-cooled primary heat exchanger (16), and then enters the water-cooled primary heat exchanger (17), and most of the oil in the oil and gas enters the air-cooled primary heat exchanger (16). Condensed in the air-cooled primary heat exchanger (16) and the water-cooled primary heat exchanger (17), the condensed oil and non-condensable combustible gas enter the primary gas-liquid separation tank (18) to achieve oil and gas separation, and pyrolysis oil Collect and store in the first oil tank (271);

The oil and gas generated by the three-stage cracking reactor (8) first passes through the second basket filter (142) to remove the solid ash, and then enters the second-stage settling tower (19) to further remove the solid ash in the oil and gas, wherein the molecular chain is relatively small. Large components are also condensed in the secondary settling tower (19), and the uncondensed oil and gas enters the air-cooled secondary heat exchanger (20), and then enters the water-cooled secondary heat exchanger (21), and most of the oil in the oil and gas enters the air-cooled secondary heat exchanger (20). It is condensed in the air-cooled secondary heat exchanger (20) and the water-cooled secondary heat exchanger (21), and the condensed oil and non-condensable combustible gas enter the secondary gas-liquid separation tank (22) to realize oil and gas separation, and pyrolyze the oil. Collect and store in the second oil tank (272);

(5) Non-condensable combustible gas combustion: the non-condensable combustible gas separated from the first-level gas-liquid separation tank (18), the second-level gas-liquid separation tank (22) and the third-level gas-liquid separation tank (26) passes through the non-condensable combustible gas After being processed by the purifier (28), it is returned to the burner (31) for combustion, and is provided for the primary cracking reactor (6), the secondary cracking reactor (7) and the tertiary cracking reactor (8) through the combustion chamber (30). high temperature flue gas;

(6) Exhaust gas treatment: Exhaust gas generated during the dehydration process of the extrusion dryer (1) and the exhaust gas generated by the combustion of non-condensable combustible gas are connected to the exhaust gas treatment module (29), passed into the filter bag filter to remove dust particles, and then enter the It is cooled in the surface cooler to condense the water vapor into liquid water and discharged, and then enters the UV photocatalytic furnace to destroy the molecular structure of the exhaust gas, then enters the activated carbon box to absorb pollutants, and finally discharges the purified exhaust gas through the fan.