PROCESS FOR PREPARING CHEMICALS BY GRADED GAS-PHASE DEHYDROGENATION AND CRACKING OF WASTE PLASTICS AND CRUDE OIL MIXED FEEDING

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The application claims priority to the Chinese Application No. 202411864650.0, filed on Dec. 17, 2024, the content of which is specifically and entirely incorporated herein by reference.

FIELD

The present disclosure provides a process for preparing chemicals by graded gas-phase dehydrogenation and cracking of waste plastics and crude oil mixed feeding, it belongs to the field of energy and chemical industry.

BACKGROUND

Although the widespread use of plastics has provided great convenience for daily life of the people, it has also brought forth a lot of white pollution. The use cycle of plastics is very short, a large number of plastic products, especially packaging materials, are discarded about 6-12 months after putting into use, 40% of plastics are discarded after 1-2 years, the total annual output of plastic waste in the world has reached 50 million tons. In the past few decades, waste plastics have been regarded as a part of municipal solid waste (MSW). According to surveys, waste plastics account for 4-10wt % or 10-20vol % of MSW in the industrially developed countries, mainly derived from packaging waste, automobile garbage and processing waste. The percentages of various types of waste plastics are as follows: 27% of low-density polyethylene (LDPE), 21% of high-density polyethylene (HDPE), 18% of polypropylene (PP), 16% of polystyrene (PS), and 7% of polyvinyl chloride (PVC). Because of the absence of the efficient, clean and large-scale processing technology, the waste plastics have emerged as an environmental challenge that needs to be solved in the world.

Landfilling, incineration and recycling are the three main methods for treating the urban plastic solid wastes. Because of the different national conditions, the treatment methods of urban plastic solid wastes vary from country to country. The United States of America (USA) mainly utilizes the landfilling method, while the Europe and Japan mainly adopt the incineration method. At present, the rapid pyrolysis/catalytic pyrolysis liquefaction or chemical production of waste plastics has attracted the focus of attention in China and foreign countries, and is also the waste plastic treatment technology with the most promising industrialization prospects.

The rapid pyrolysis/catalytic pyrolysis of waste plastics is an effective recycling means involving with heating and decomposing waste plastics at high temperatures under oxygen-free or low-oxygen conditions and producing valuable products, such as the pyrolysis and liquefaction of waste plastics to produce gasoline, diesel oil, petroleum wax and other chemical raw materials. However, in view of the characteristics of waste plastics such as large size and light weight, difficulty in compression, poor air permeability, easy expansion, prone to melting and bonding, and poor thermal conductivity, it is difficult to solve the problem of continuous feeding and rapid heating. At present, most of the pyrolysis and liquefaction of waste plastics adopt reaction kettle-type intermittent reactions and horizontal type rotary kiln reactions, with the defects of slow heating rate, severe feedstock adhesion and coking, low liquid product yield and added value, difficult to improve processing capacity, difficult to scale up the pyrolysis device, and the subsequent processing of chlorine-containing liquid products is challenging, the defects have hampered the efficient, clean and large-scale utilization of waste plastics. There is no large-scale waste plastic pyrolysis device in commercial operation at present.

The process for preparing chemicals by graded gas-phase dehydrogenation and cracking of crude oil directly bypasses traditional crude oil processing technology routes such as atmospheric and vacuum distillation, catalytic cracking, hydrocracking, and delayed coking, and directly catalyze dehydrogenation and cracking to produce basic chemical raw materials such as the three olefins (ethylene, propylene and butylene) and the three arenes (benzene, toluene and xylenes), the process has the advantages such as a short process, simple and convenient operation, low cost and energy consumption, and small investment, it is the most industrially promising “oil conversion” petroleum refining technology that adapts to the energy source transformation brought forth by automobile electrification. Combining the rapid pyrolysis/catalytic pyrolysis of waste plastics with the process for preparing chemicals by graded gas-phase dehydrogenation and cracking of crude oil is an effective means to improve the clean and efficient raw material utilization of waste plastics, reduce the consumption of petroleum resources, solve the pyrolysis and feeding problems of waste plastics, and improve the chemical yield and economic benefits of the device, thus it is urgent to develop a process for preparing chemicals by graded gas-phase dehydrogenation and cracking of waste plastics and crude oil mixed feeding, and the relevant equipment technology.

SUMMARY

The present disclosure aims to overcome the defects in the prior art with respect to waste plastic pyrolysis and liquefaction, and provide a process for preparing chemicals by graded gas-phase dehydrogenation and cracking of waste plastics and crude oil mixed feeding, wherein the circulation of pyrolysis dry gas and high-temperature recycle oil are used for carrying out the hot melt dechlorination and desulfurization pretreatment and the liquid phase atomization feeding of waste plastics, in order to solve the difficult problems in pyrolysis feeding of waste plastics and removal of chlorine and sulfur heteroatoms therefrom; a downer bed reactor is used for grading and gas phase catalytic cracking, and the cracking characteristics of waste plastics and crude oil in the mixed raw materials are complementary, the liquid phase cage wall effect is eliminated, the C—C and C—H bond breakage is regulated and controlled, the polycondensation coking is inhibited, the amplification effect is eliminated, the controllable cracking of waste plastics is achieved, and the yields of the three olefins (ethylene, propylene and butylene) and the three arenes (benzene, toluene and xylenes) are maximized; the five common problems in the industry are solved, namely adhesion and coking of waste plastic feedstock, difficulty in mixing the waste plastics with a heat carrier, low yield and added value of liquid product, difficulty in removing chlorine and sulfur heteroatoms from liquid product thereby affecting the subsequent processing, and difficulty in amplifying the pyrolysis device, thus the efficient, clean, high-value and large-scale utilization of waste plastics and crude oil is achieved.

The present disclosure provides a process for preparing chemicals by graded gas-phase dehydrogenation and cracking of waste plastics and crude oil mixed feeding, wherein the clean PE and PP waste plastics are sorted and processed by a waste plastics pulverizer, the obtained waste plastic fragments are added into a water-cooling feed pipe at a temperature of 20-95° C. through a controllable feeder, the waste plastic fragments are carried by a cracked dry gas and fall into an oil slurry molten liquid at a temperature of 240-320° C. in a hot melting dechlorination reactor equipped with a stirrer, and subjected to the molten dechlorination desulfurization pretreatment by stirring and mixing; the molten plastic liquid extracted from the bottom of the hot melting dechlorination reactor is pressurized and conveyed by a delivery pump, a part of the molten plastic liquid is heated by a high speed circulating tube equipped with an external heater to a temperature 20-60° C. higher than that of an oil slurry molten liquid, and returned to the upper part of said hot melting dechlorination reactor, the other part of the molten plastic liquid is used as a raw material and conveyed along with crude oil to the upper middle part of a downer cracking reactor to be fed through an atomizing feedstock nozzle; the fuel gas extracted from the top of the hot melting dechlorination reactor is treated by a desulfurization dechlorination reactor and then enters a refinery gas pipe network as the fuel gas, wherein the flow rate of the high speed circulating tube is within the range of 2-30 m/s, the mass ratio of the molten plastic liquid which returns to the upper part of the hot melting dechlorination reactor to raw material of the hot melting dechlorination reactor is 1-10:1; the atomized particle feedstock of a mixture of the molten plastic liquid used as a raw material and crude oil is subjected to rapid mixing, vaporization and controllable cracking reaction with a cracking regenerated catalyst falling from the top of said downer cracking reactor, the steam dosage of the atomizing feedstock nozzle is 4-12wt % of a mixture of the molten plastic liquid used as a raw material and crude oil, the cracking reaction temperature is within the range of 500-550° C., the pressure is within the range of 0-0.3 MPa, the reaction time is from 600 millisecond to 2 seconds, and a gas-solid separation of oil and gas is performed by a gas-solid fast separator at the bottom of said downer cracking reactor; the separated spent catalyst passes through a spent catalyst return device and flows into the bottom of a cracking riser regenerator and subjected to an air fluidized coke burning regeneration at a temperature range of 500-750° C., the bottom of said cracking riser regenerator is provided with a regenerated air inlet, and the top of said cracking riser regenerator is provided with a gas-solid separator, a heat exchanger and a regenerated flue gas outlet in sequence; the regenerated catalyst separated by the gas-solid separator at the top of said cracking riser regenerator is circulated back to the top of said downer cracking reactor through a regenerated catalyst return device to catalytically crack a mixture of molten plastic liquid used as a raw material and crude oil; the high-temperature cracked oil gas are directly injected from a gas phase feeding hole at the upper-middle part of a downer pyrolysis reactor without subjecting to condensation, and are rapidly mixed with the pyrolysis regenerated catalyst falling from the top and carry out a controllable cracking reaction, and subjected to a gas-solid separation of oil and gas by a gas-solid fast separator at the bottom of said downer pyrolysis reactor, wherein the pyrolysis reaction temperature is within the range of 570-650° C., the pressure is within the range of 0-0.3 MPa, and the reaction time is from 200 milliseconds to 1 second; the separated pyrolysis spent catalyst passes through a spent catalyst return device and flows into the bottom of the pyrolysis riser regenerator and subjected to an air fluidized coke burning regeneration at a temperature range of 600-750° C., the bottom of said pyrolysis riser regenerator is provided with an air inlet, and the top of said pyrolysis riser regenerator is provided with a gas-solid separator, a heat exchanger and a flue gas outlet in sequence; the pyrolysis regenerated catalyst separated by the gas-solid separator at the top of said pyrolysis riser regenerator is circulated back to the top of said downer pyrolysis reactor through a spent catalyst return device to catalytically crack the high temperature cracked oil gas; the high-temperature cracked oil and gas enter a fractionation tower for separation; a route of the cracked dry gas at the top of said fractionation tower is circulated back to the water-cooling feed pipe at the top of said hot melting dechlorination reactor as a feedstock carrying gas, another route of the cracked dry gas is connected to a pyrolysis gas refining system to produce the three olefins (ethylene, propylene and butylene); a route of the fractionation tower recycle oil is circulated back to the upper part of the hot melting dechlorination reactor as a high-temperature molten oil, another route of the fractionation tower recycle oil is delivered outward as a product after recovering the waste heat; the other side lines of the fractionation tower are a crude benzene fraction and a diesel fraction.

The outer wall of the water-cooling feed pipe is provided with a water-cooling jacket having a positive conical shape, a straight-pipe, or a reverse conical shape, preferably a positive conical shape.

The controllable feeder is a rotary feeder, a dual-axis screw feeder or a single-axis screw feeder.

The heating of the high speed circulating tube is performed by electromagnetic induction heating, heat conductive oil heating, steam heating or resistive heating, preferably electromagnetic induction heating.

The cracking catalyst is one of semi-coke microspheres, alumina microspheres, calcium aluminate porous microspheres, magnesium aluminate spinel porous microspheres, aluminum silicate porous microspheres, calcium silicate porous microspheres, magnesium silicate porous microspheres, and porous microsphere carriers loaded with alkali metals and/or alkaline earth metals, or a mixture thereof.

The pyrolysis catalyst is one of FCC molecular sieve catalyst, ZSM-5 shape-selective zeolite catalyst and alkaline solid porous catalyst, or a mixture thereof.

The riser regenerator is composed of a turbulent fluidized bed at the lower part and a carrying reactor at the upper part; the equivalent diameter of said turbulent fluidized bed is large, the equivalent diameter of said carrying reactor is small, the mass ratio of the equivalent diameter of said turbulent fluidized bed to the equivalent diameter of said carrying reactor is 2-3:1; the carrying reactor may be a straight tube reactor with uniform equivalent diameter, or may be composed of large and small straight tubes with diameters of different multiples of the equivalent diameter connected by large and small head pipe fittings, and the diameter ratio of the large straight tube to the small straight tube is 1.2-2:1.

The present disclosure has the following advantages over the prior art:

The present disclosure provides a process for preparing chemicals by graded gas-phase dehydrogenation and cracking of waste plastics and crude oil mixed feeding, wherein the circulation of pyrolysis dry gas and high-temperature recycle oil are used for carrying out the hot melt dechlorination and desulfurization pretreatment and the liquid phase atomization feeding of waste plastics, effectively solve the difficult problems in pyrolysis feeding of waste plastics and removal of chlorine and sulfur heteroatoms therefrom; a downer bed reactor is used for graded gas-phase catalytic cracking, and the complementarity of cracking characteristics of waste plastics and crude oil in the mixed raw materials are sufficiently utilized, the liquid phase cage wall effect is eliminated, the C—C and C—H bond breakage is regulated and controlled, the polycondensation coking is inhibited, the amplification effect is eliminated, the controllable cracking of waste plastics is achieved, and the yields of the three olefins (ethylene, propylene and butylene) and the three arenes (benzene, toluene and xylenes) are maximized; the five common problems in the industry are solved, namely adhesion and coking of waste plastic feedstock, difficulty in mixing the waste plastics with a heat carrier, low yield and added value of liquid product, difficulty in removing chlorine and sulfur heteroatoms from liquid product thereby affecting the subsequent processing, and difficulty in amplifying the pyrolysis device, thus the efficient, clean, high-value and large-scale utilization of waste plastics and crude oil is achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic diagram of the process for preparing chemicals by graded gas-phase dehydrogenation and cracking of waste plastics and crude oil mixed feeding in the present disclosure.

DESCRIPTION OF REFERENCE SIGNS

• • 1 Gas-solid separator
  • 2 Regenerated catalyst return device
  • 3 Atomizing feedstock nozzle
  • 4 Downer cracking reactor
  • 5 Gas-solid fast separator
  • 6 Pyrolysis oil gas outlet
  • 7 Spent catalyst return device
  • 8 Downer pyrolysis reactor
  • 9 Regenerated air inlet
  • 10 Cracking riser regenerator
  • 11 Heat exchanger
  • 12 Regenerated flue gas outlet
  • 13 Pyrolysis riser regenerator
  • 14 Air inlet
  • 15 Flue gas outlet
  • 16 Fractionation tower
  • 17 Crude benzene fraction
  • 18 Diesel fraction
  • 19 Recycle oil pump
  • 20 Hot melting dechlorination reactor
  • 21 Waste plastic pulverizer
  • 22 Controllable feeder
  • 23 Water-cooling feed pipe
  • 24 Desulfurization dechlorination reactor
  • 25 Delivery pump
  • 26 High speed circulating tube
  • 27 Refinery gas pipe network

DETAILED DESCRIPTION

The terminals and any value of the ranges disclosed herein are not limited to the precise ranges or values, such ranges or values shall be comprehended as comprising the values adjacent to the ranges or values. As for numerical ranges, the endpoint values of the various ranges, the endpoint values and the individual point values of the various ranges, and the individual point values may be combined with one another to produce one or more new numerical ranges, which should be deemed to have been specifically disclosed herein.

The present disclosure provides a process for preparing chemicals by graded gas-phase dehydrogenation and cracking of waste plastics and crude oil mixed feeding, wherein the clean PE and PP waste plastics are sorted and processed by a waste plastics pulverizer, the obtained waste plastic fragments are added into a water-cooling feed pipe at a temperature of 20-95° C. through a controllable feeder, the waste plastic fragments are carried by a cracked dry gas and fall into an oil slurry molten liquid at a temperature of 240-320° C. in a hot melting dechlorination reactor equipped with a stirrer, and subjected to the molten dechlorination desulfurization pretreatment by stirring and mixing; the molten plastic liquid extracted from the bottom of the hot melting dechlorination reactor is pressurized and conveyed by a delivery pump, a part of the molten plastic liquid is heated by a high speed circulating tube equipped with an external heater to a temperature 20-60° C. higher than that of an oil slurry molten liquid, and returned to the upper part of said hot melting dechlorination reactor, the other part of the molten plastic liquid is used as a raw material and conveyed along with crude oil to the upper middle part of a downer cracking reactor to be fed through an atomizing feedstock nozzle; the fuel gas extracted from the top of the hot melting dechlorination reactor is treated by a desulfurization dechlorination reactor and then enters a refinery gas pipe network as the fuel gas, wherein the flow rate of the high speed circulating tube is within the range of 2-30 m/s, the mass ratio of the molten plastic liquid which returns to the upper part of the hot melting dechlorination reactor to raw material of the hot melting dechlorination reactor is 1-10:1; the atomized particle feedstock of a mixture of the molten plastic liquid used as a raw material and crude oil is subjected to rapid mixing, vaporization and controllable cracking reaction with a cracking regenerated catalyst falling from the top of said downer cracking reactor, the steam dosage of the atomizing feedstock nozzle is 4-12wt % of a mixture of the molten plastic liquid used as a raw material and crude oil, the cracking reaction temperature is within the range of 500-550° C., the pressure is within the range of 0-0.3 MPa, the reaction time is from 600 millisecond to 2 seconds, and a gas-solid separation of oil and gas is performed by a gas-solid fast separator at the bottom of said downer cracking reactor; the separated spent catalyst passes through a spent catalyst return device and flows into the bottom of a cracking riser regenerator and subjected to an air fluidized coke burning regeneration at a temperature range of 500-750° C., the bottom of said cracking riser regenerator is provided with a regenerated air inlet, and the top of said cracking riser regenerator is provided with a gas-solid separator, a heat exchanger and a regenerated flue gas outlet in sequence; the regenerated catalyst separated by the gas-solid separator at the top of said cracking riser regenerator is circulated back to the top of said downer cracking reactor through a regenerated catalyst return device to catalytically crack a mixture of molten plastic liquid used as a raw material and crude oil; the high-temperature cracked oil gas are directly injected from a gas phase feeding hole at the upper-middle part of a downer pyrolysis reactor without subjecting to condensation, and are rapidly mixed with the pyrolysis regenerated catalyst falling from the top and carry out a controllable cracking reaction, and subjected to a gas-solid separation of oil and gas by a gas-solid fast separator at the bottom of said downer pyrolysis reactor, wherein the pyrolysis reaction temperature is within the range of 570-650° C., the pressure is within the range of 0-0.3 MPa, and the reaction time is from 200 milliseconds to 1 second; the separated pyrolysis spent catalyst passes through a spent catalyst return device and flows into the bottom of the pyrolysis riser regenerator and subjected to an air fluidized coke burning regeneration at a temperature range of 600-750° C., the bottom of said pyrolysis riser regenerator is provided with an air inlet, and the top of said pyrolysis riser regenerator is provided with a gas-solid separator, a heat exchanger and a flue gas outlet in sequence; the pyrolysis regenerated catalyst separated by the gas-solid separator at the top of said pyrolysis riser regenerator is circulated back to the top of said downer pyrolysis reactor through a spent catalyst return device to catalytically crack the high temperature cracked oil gas; the high-temperature cracked oil and gas enter a fractionation tower for separation; a route of the cracked dry gas at the top of said fractionation tower is circulated back to the water-cooling feed pipe at the top of said hot melting dechlorination reactor as a feedstock carrying gas, another route of the cracked dry gas is connected to a pyrolysis gas refining system to produce the three olefins (ethylene, propylene and butylene); a route of the fractionation tower recycle oil is circulated back to the upper part of the hot melting dechlorination reactor as a high-temperature molten oil, another route of the fractionation tower recycle oil is delivered outward as a product after recovering the waste heat; the other side lines of the fractionation tower are a crude benzene fraction and a diesel fraction.

In the present invention, the process for preparing chemicals by graded gas-phase dehydrogenation and cracking of waste plastics and crude oil mixed feeding, w herein the circulation of pyrolysis dry gas and high-temperature recycle oil are used for carrying out the circulation of the hot melt dechlorination and desulfurization pretreatment of waste plastics and the liquid phase atomization feeding of waste plastics, effectively solve the difficult problems in pyrolysis feeding of waste plastics and removal of chlorine and sulfur heteroatoms therefrom; a downer bed reactor is used for grading and gas phase catalytic cracking, and the complementarity of cracking characteristics of waste plastics and crude oil in the mixed raw materials are sufficiently utilized, the liquid phase cage wall effect is eliminated, the C—C and C—H bond breakage is regulated and controlled, the polycondensation coking is inhibited, the amplification effect is eliminated, the controllable cracking of waste plastics is achieved, and the yields of the three olefins (ethylene, propylene and butylene) and the three arenes (benzene, toluene and xylenes) are maximized; the five common problems in the industry are solved, namely adhesion and coking of waste plastic feedstock, difficulty in mixing the waste plastics with a heat carrier, low yield and added value of liquid product, difficulty in removing chlorine and sulfur heteroatoms from liquid product thereby affecting the subsequent processing, and difficulty in amplifying the pyrolysis device, thus the efficient, clean, high-value and large-scale utilization of waste plastics and crude oil is achieved.

According to the present disclosure, the raw material of the hot melting dechlorination reactor refers to the waste plastic fragments that added into the hot melt dechlorination reactor.

According to the present disclosure, the size of the waste plastic fragments obtained by the treatment with a waste plastic pulverizer treatment has a wide selection range. Preferably, the length of the waste plastic fragments is less than or equal to 15 cm, more preferably within the range of 3-5 cm, the width of the waste plastic fragments is is less than or equal to 15 cm, more preferably within the range of 3-5 cm.

According to the present invention, for any single piece of waste plastic debris, its length refers to the maximum distance between any two points of the waste plastic fragment; its width refers to the maximum distance between two points of the waste plastic fragment in a straight line direction perpendicular to the length direction. In the present invention, unless otherwise specified, the length and width of the waste plastic fragments refer to the average length and average width of all waste plastic fragments, respectively.

According to the present disclosure, the kind of controllable feeder can be selected from a wide range. According to a preferred embodiment of the present disclosure, the controllable feeder is a rotary feeder, a dual-axis screw feeder or a single-axis screw feeder.

According to a preferred embodiment of the present invention, the obtained waste plastic fragments are added into a water-cooling feed pipe at a temperature of 20-95° C. through a controllable feeder, for example, the temperature may be 20° C., 30° C., 40° C., 50° C., 60° C., 70° C., 80° C., 90° C., 95° C., and a random value within the range consisting of any two numerical values, preferably within the range of 50-70° C. In the present disclosure, the use of such a preferred embodiment can effectively prevent the waste plastics from softening and cementation in advance due to excessively high temperature, avoid plugging of the feed system, and can ensure that the material enters the subsequent hot melting dehydrogenation reactor at an appropriate temperature, and achieve smooth transition with the high-temperature oil slurry.

In accordance with a preferred embodiment of the present invention, the outer wall of the water-cooling feeding pipe is provided with a water-cooling jacket, wherein the water-cooling feeding pipe has a positive conical shape, straight-pipe, or reverse conical shape, more preferably a positive conical shape.

According to a preferred embodiment of the present invention, the said oil slurry molten liquid at a temperature of 240-320° C., for example, the temperature may be 240° C., 250° C., 260° C., 270° C., 280° C., 290° C., 300° C., 310° C., 320° C., and a random value within the range consisting of any two numerical values, more preferably within the range of 280-300° C. In the present invention, the use of aforementioned preferred embodiment ensures rapid melting of the waste plastic fragments while promoting efficient removal of heteroatoms such as dechlorination and desulfurization, facilitating the subsequent atomized feed and graded cracking, and is conducive to solving the industrial problems that the impurities are difficult to remove and easily coked during the treatment of waste plastics.

According to a preferred embodiment of the present invention, the heating of the high speed circulating tube is performed by electromagnetic induction heating, heat conductive oil heating, steam heating or resistive heating, more preferably electromagnetic induction heating.

According to a preferred embodiment of the present invention, the mass ratio of the molten plastic liquid which returns to the upper part of the hot melting dechlorination reactor to raw material of the hot melting dechlorination reactor is 1-10:1, such as 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, and a random value within the range consisting of any two numerical values, more preferably 3-6:1. In the present invention, the use of said preferred embodiment facilitates subsequent atomized feed and graded cracking, and is conducive to solving the industrial problems that the impurities are difficult to remove and easily coked during the treatment of waste plastics.

According to a preferred embodiment of the present disclosure, the steam dosage of the atomizing feedstock nozzle is 4-12wt % of a mixture of the molten plastic liquid used as a raw material and crude oil, for example, it may be 4wt %, 5wt %, 6wt %, 7wt %, 8wt %, 9wt %, 10wt %, 11wt %, 12wt %, and a random value within the range consisting of any two numerical values, more preferably 6-9wt %.

According to the present disclosure, the kind of cracking catalyst used in the downer cracking reactor has a wide selection range. According to one preferred embodiment of the present disclosure, the cracking catalyst is one of semi-coke microspheres, alumina microspheres, calcium aluminate porous microspheres, magnesium aluminate spinel porous microspheres, aluminum silicate porous microspheres, calcium silicate porous microspheres, magnesium silicate porous microspheres, and porous microsphere carriers loaded with alkali metals and/or alkaline earth metals, or a mixture thereof.

According to a preferred embodiment of the present disclosure, the cracking reaction temperature is within the range of 510-550° C., the pressure is within the range of 0.1-0.3 MPa, the reaction time is within the range of 700 millisecond to 2 seconds.

According to the present disclosure, the kind of cracking catalysts used in the downer pyrolysis reactor can be selected from a wide range. According to a preferred embodiment of the present disclosure, the pyrolysis catalyst is one of FCC molecular sieve catalyst, ZSM-5 shape-selective zeolite catalyst and alkaline solid porous catalyst, or a mixture thereof.

According to a preferred embodiment of the present disclosure, the pyrolysis reaction temperature is within the range of 580-650° C., the pressure is within the range of 0.1-0.3 MPa, and the reaction time is within the range of 500 millisecond to 1 second.

According to a preferred embodiment of the present disclosure, the riser regenerator is composed of a turbulent fluidized bed at the lower part and a carrying reactor at the upper part, the ratio of the equivalent diameter of said turbulent fluidized bed to the equivalent diameter of said carrying reactor is 2-3:1, such as 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1, and a random value within the range consisting of any two numerical values. Use of the above embodiments in the present disclosure is conducive to maintaining the stable regenerated temperature and heat capacity, overcoming the defect that the riser is difficult to implement the regenerative ignition, achieving the rapid transport of the upper part, continuously providing a high quality high-temperature regenerated catalyst for the downer bed reactor, improving selectivity of the pyrolysis reaction, thereby effectively suppressing the coking phenomenon, ensuring the operational stability and scalability of the entire process plant.

According to a preferred embodiment of the present disclosure, the carrying reactor is a straight tube reactor with uniform equivalent diameter, or is composed of large and small straight tubes with diameters of different multiples of the equivalent diameter connected by large and small head pipe fittings, and the diameter ratio of the large straight tube to the small straight tube is 1.2-2:1, for example, the diameter ratio may be 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, and a random value within the range consisting of any two numerical values. In the present disclosure, the use of aforementioned embodiment is conducive to regulating and controlling periodic variation of flow rates of gas-phase and solid-phase materials during the whole process, enhancing the heat and mass transfer, optimizing the flow and reaction state in the entire riser, avoiding the catalyst deposition, ensuring the efficient and stable regeneration process, facilitating the downer bed reactor to continuously obtain a thermal catalyst, precisely regulating and controlling C—C and C—H bond breakage, suppressing polycondensation coking, achieving controllable cracking of waste plastics, and producing the three olefins (ethylene, propylene and butylene) and the three arenes (benzene, toluene and xylenes) with a maximum yield, and effectively eliminating fluidization and heat transfer bottlenecks in the plant amplification process, and overcoming the five common problems in the industry.

According to the present disclosure, when the carrying reactor is composed of large and small straight tubes with diameters of different multiples of the equivalent diameter connected by large and small head pipe fittings, the equivalent diameter of said carrying reactor is the equivalent diameter of the straight tube directly connected to the turbulent fluidized bed.

The present invention provides a process for preparing chemicals by graded gas-phase dehydrogenation and cracking of waste plastics and crude oil mixed feeding, the process enables continuous, large-scale, efficient and clean utilization of waste plastics and crude oil for producing high value added chemicals such as the three olefins (ethylene, propylene and butylene) and the three arenes (benzene, toluene and xylenes), solves the five common problems in the industry, namely adhesion and coking of waste plastic feedstock, difficulty in mixing the waste plastics with a heat carrier, low yield and added value of liquid product, difficulty in amplifying the pyrolysis device, and difficulty in removing chlorine heteroatom from liquid product thereby affecting the subsequent processing, the yield of the three olefins (ethylene, propylene and butylene) is larger than or equal to 50%, the yield of the three arenes (benzene, toluene and xylenes) is larger than or equal to 15%, the diesel yield is larger than or equal to 20%, the overall yield of liquid products (including liquefied gas) is 93% or more, which is increased by 25 or more percentage points over the conventional waste plastic pyrolysis technology, thereby achieving the stable, reliable and long-term operation of the process plant.

The process for preparing chemicals by mixed feeding, grading, gas-phase dehydrogenation and cracking of waste plastics and crude oil will be described in detail below with reference to FIG. 1 and preferred examples of the present disclosure.

The present invention provides a process for preparing chemicals by graded gas-phase dehydrogenation and cracking of waste plastics and crude oil mixed feeding, wherein the clean PE and PP waste plastics are sorted and processed by a waste plastic pulverizer 21, the obtained waste plastic fragments are added into a water-cooling feed pipe 23 at a temperature of 20-95° C. through a controllable feeder 22, the waste plastic fragments are carried by a cracked dry gas and fall into an oil slurry molten liquid at a temperature of 240-320° C. in a hot melting dechlorination reactor 20 equipped with a stirrer, and subjected to the molten dechlorination desulfurization pretreatment by stirring and mixing; the molten plastic liquid extracted from the bottom of the hot melting dechlorination reactor 20 is pressurized and conveyed by a delivery pump 25, a part of the molten plastic liquid is heated by a high speed circulating tube 26 equipped with an external heater to a temperature 20-60° C. higher than that of an oil slurry molten liquid, and returned to the upper part of said hot melting dechlorination reactor 20, the other part of the molten plastic liquid is used as a raw material and conveyed along with crude oil to the upper middle part of a downer cracking reactor 4 to be fed through an atomizing feedstock nozzle 3; the fuel gas extracted from the top of the hot melting dechlorination reactor 20 is treated by a desulfurization dechlorination reactor 24 and then enters a refinery gas pipe network 27 as the fuel gas, wherein the flow rate of the high speed circulating tube 26 is within the range of 2-30 m/s, the mass ratio of the molten plastic liquid which returns to the upper part of the hot melting dechlorination reactor 20 to raw material of the hot melting dechlorination reactor 20 is 1-10:1, the atomized particle feedstock of a mixture of the molten plastic liquid used as a raw material and crude oil is subjected to rapid mixing, vaporization and controllable cracking reaction with a cracking regenerated catalyst falling from the top of said downer cracking reactor 4, the steam dosage of the atomizing feedstock nozzle 3 is 4-12wt % of a mixture of the molten plastic liquid used as a raw material and crude oil, the cracking reaction temperature is within the range of 500-550° C., the pressure is within the range of 0-0.3 MPa, the reaction time is from 600 millisecond to 2 seconds, and a gas-solid separation of oil and gas is performed by a gas-solid fast separator 5 at the bottom of said downer cracking reactor 4; the separated spent catalyst passes through a spent catalyst return device 7 and flows into the bottom of a cracking riser regenerator 10 and subjected to an air fluidized coke burning regeneration at a temperature range of 500-750° C., the bottom of said cracking riser regenerator 10 is provided with a regenerated air inlet 9, and the top of said cracking riser regenerator is provided with a gas-solid separator 1, a heat exchanger 11 and a regenerated flue gas outlet 12 in sequence; the regenerated catalyst separated by the gas-solid separator 1 at the top of said cracking riser regenerator 10 is circulated back to the top of said downer cracking reactor 4 through a regenerated catalyst return device 2 to catalytically crack a mixture of molten plastic liquid used as a raw material and crude oil; the high-temperature cracked oil gas derived from a pyrolysis oil gas outlet 6 are directly injected from a gas phase feeding hole at the upper-middle part of a downer pyrolysis reactor 8 without subjecting to condensation, and are rapidly mixed with the pyrolysis regenerated catalyst falling from the top and carry out a controllable cracking reaction, and subjected to a gas-solid separation of oil and gas by a gas-solid fast separator 5 at the bottom of said downer pyrolysis reactor 8, wherein the pyrolysis reaction temperature is within the range of 570-650° C., the pressure is within the range of 0-0.3 MPa, and the reaction time is from 200 milliseconds to 1 second; the separated pyrolysis spent catalyst passes through a spent catalyst return device 7 and flows into the bottom of the pyrolysis riser regenerator 13 and subjected to an air fluidized coke burning regeneration at a temperature range of 600-750° C., the bottom of said pyrolysis riser regenerator 13 is provided with an air inlet 14, and the top of said pyrolysis riser regenerator is provided with a gas-solid separator 1, a heat exchanger 11 and a flue gas outlet 15 in sequence; the pyrolysis regenerated catalyst separated by the gas-solid separator 1 at the top of said pyrolysis riser regenerator 13 is circulated back to the top of said downer pyrolysis reactor 13 through a spent catalyst return device 7 to catalytically crack the high temperature cracked oil gas; the high-temperature cracked oil and gas enter a fractionation tower 16 for separation; a route of the cracked dry gas at the top of said fractionation tower 16 is in communication with a feedstock carrying gas inlet of the water-cooling feed pipe 23 at the top of said hot melting dechlorination reactor 20, another route of the cracked dry gas is connected to a pyrolysis gas refining system to produce the three olefins (ethylene, propylene and butylene) and the three arenes (benzene, toluene and xylenes); a recycle oil pump 19 at a route of the recycle oil pipeline of a fractionation tower 16 is connected with a high-temperature molten oil inlet at the upper part of the hot melting dechlorination reactor 20, another route of the recycle oil pipeline is delivered outward as a product after recovering the waste heat; the other side lines of the fractionation tower 16 are a crude benzene fraction 17 and a diesel fraction 18.

The present disclosure will be described in detail below with reference to examples.

• • Yield of the three olefins (ethylene, propylene and butylene)=(ethylene output+propylene output+butylene output)/raw material feeding amount*100%;
  • Yield of the three arenes (benzene, toluene and xylenes)=(benzene output+toluene output+xylene output)/raw material feeding amount*100%;
  • Diesel yield=Diesel output/raw material feeding amount*100%;
  • Total yield of liquid product=(liquefied gas output+gasoline output+diesel output)/raw material feeding amount*100%.

Example 1

The clean PE and PP waste plastics were sorted and processed by a waste plastics pulverizer, the obtained waste plastic fragments (with a length of 5 cm and a width of 3 cm) were added into a water-cooling feed pipe at a temperature of 50° C. through a controllable feeder, the waste plastic fragments were carried by a cracked dry gas and fell into an oil slurry molten liquid at a temperature of 300° C. in a hot melting dechlorination reactor equipped with a stirrer, and subjected to the molten dechlorination desulfurization pretreatment by stirring and mixing;

The molten plastic liquid extracted from the bottom of the hot melting dechlorination reactor was pressurized and conveyed by a delivery pump, a part of the molten plastic liquid was heated by a high speed circulating tube equipped with an external heater to a temperature 30° C. higher than that of an oil slurry molten liquid, and then returned to the upper part of said hot melting dechlorination reactor, the other part of the molten plastic liquid was used as a raw material and conveyed along with crude oil to the upper middle part of a downer cracking reactor to be fed through an atomizing feedstock nozzle; the fuel gas extracted from the top of the hot melting dechlorination reactor was treated by a desulfurization dechlorination reactor and then entered a refinery gas pipe network as the fuel gas, wherein the flow rate of the high speed circulating tube was 10 m/s, the mass ratio of the molten plastic liquid which returns to the upper part of the hot melting dechlorination reactor to raw material of the hot melting dechlorination reactor was 3:1;

The atomized particle feedstock of a mixture of the molten plastic liquid used as a raw material and crude oil was subjected to rapid mixing, vaporization and controllable cracking reaction with a cracking regenerated catalyst falling from the top of said downer cracking reactor, the steam dosage of the atomizing feedstock nozzle is 8wt % of a mixture of the molten plastic liquid used as a raw material and crude oil, the cracking reaction temperature was 530° C., the pressure was 0.26 MPa, the reaction time was 0.8 second, and a gas-solid separation was performed by a gas-solid fast separator at the bottom of said downer cracking reactor;

The separated spent catalyst passed through a spent catalyst return device and flowed into the bottom of a cracking riser regenerator and subjected to an air fluidized coke burning regeneration at a temperature of 750° C., the bottom of said cracking riser regenerator was provided with a regenerated air inlet, and the top of said cracking riser regenerator was provided with a gas-solid separator, a heat exchanger and a regenerated flue gas outlet in sequence; the regenerated catalyst separated by the gas-solid separator at the top of said cracking riser regenerator was circulated back to the top of said downer cracking reactor through a regenerated catalyst return device to catalytically crack a mixture of molten plastic liquid used as a raw material and crude oil;

The high-temperature cracked oil and gas were directly injected from a gas phase feeding hole at the upper-middle part of a downer pyrolysis reactor without subjecting to condensation, and were rapidly mixed with the pyrolysis regenerated catalyst falling from the top and carry out a controllable cracking reaction, and subjected to a gas-solid separation of oil and gas by a gas-solid fast separator at the bottom of said downer pyrolysis reactor, wherein the pyrolysis reaction temperature was 600° C., the pressure was 0.26 MPa, and the reaction time was 0.6 second;

The separated pyrolysis spent catalyst passed through a spent catalyst return device and flowed into the bottom of the pyrolysis riser regenerator and subjected to an air fluidized coke burning regeneration at a temperature of 700° C., the bottom of said pyrolysis riser regenerator was provided with an air inlet, and the top of said pyrolysis riser regenerator was provided with a gas-solid separator, a heat exchanger and a flue gas outlet in sequence; the pyrolysis regenerated catalyst separated by the gas-solid separator at the top of said pyrolysis riser regenerator was circulated back to the top of said downer pyrolysis reactor through a spent catalyst return device to catalytically crack the high temperature cracked oil gas;

The high-temperature cracked oil and gas entered a fractionation tower for separation; a route of the cracked dry gas at the top of said fractionation tower was circulated back to the water-cooling feed pipe at the top of said hot melting dechlorination reactor as a feedstock carrying gas, another route of the cracked dry gas was connected to a pyrolysis gas refining system to produce the three olefins (thylene, propylene and utadiene); a route of the fractionation tower recycle oil was circulated back to the upper part of the hot melting dechlorination reactor as a high-temperature molten oil, another route of the fractionation tower recycle oil was delivered outward as a product after recovering the waste heat; the other side lines of the fractionation tower were a crude benzene fraction and a diesel fraction. The outputs of liquefied gas, gasoline and diesel were measured by a flow meter, the compositions of cracked dry gas and liquefied gas were obtained through the chromatographic analysis.

Upon testing and calculation, in the example, the yield of the three olefins (ethylene, propylene and butylene) was 51%, the yield of the three arenes (benzene, toluene and xylenes) was 18%, the diesel yield was 26%, and the total yield of liquid product was 95%.

As can be seen from the above examples, the present invention provides a process for preparing chemicals by graded gas-phase dehydrogenation and cracking of waste plastics and crude oil mixed feeding, the process enables continuous, large-scale, efficient and clean utilization of waste plastics and crude oil for producing high value added chemicals such as the three olefins (ethylene, propylene and butylene) and the three arenes (benzene, toluene and xylenes), solves the five common problems in the industry, namely adhesion and coking of waste plastic feedstock, difficulty in mixing the waste plastics with a heat carrier, low yield and added value of liquid product, difficulty in amplifying the pyrolysis device, and difficulty in removing chlorine heteroatom from liquid product thereby affecting the subsequent processing, the yield of the three olefins (ethylene, propylene and butylene) is larger than or equal to 50%, the yield of the three arenes (benzene, toluene and xylenes) is larger than or equal to 15%, the diesel yield is larger than or equal to 20%, the overall yield of liquid products (including liquefied gas) is 93% or more, which is increased by 25 or more percentage points over the conventional waste plastic pyrolysis technology, thereby achieving the stable, reliable and long-term operation of the process plant.