Method and system for processing waste polyolefins

Abstract

The application relates to the technical field of waste plastic pyrolysis, in particular to a processing method and system of waste polyolefin, which comprises the following steps: 1, waste polyolefin is contacted with a product directing agent to perform a pyrolysis reaction, and pyrolysis oil gas and residues are obtained; wherein the product directing agent is naphthenic oil; the feeding temperature of the waste polyolefin is 80-120 DEG C, and the feeding temperature of the product directing agent is 250-400 DEG C; the pyrolysis reaction at least comprises a first stage and a second stage; the temperature of the first stage is 250-400 DEG C, and the residence time of the first stage is 0.5-5.5 s; the temperature of the second stage is 450-650 DEG C, and the residence time of the second stage is 1-10 mins; 2, the pyrolysis oil gas is separated to obtain pyrolysis oil I with a boiling point of 40-60 DEG C and pyrolysis gas I with a boiling point of less than 40-60 DEG C. The processing method of the waste polyolefin provided in the application can significantly increase the content of gasoline fraction in the pyrolysis oil gas.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of waste plastic pyrolysis, in particular to a processing method and system of waste polyolefin. BACKGROUND

[0002] According to statistics, about 60 million tons of waste plastics are generated in China every year, about 1 / 3 of which are recycled, mainly in the form of PET; and 2 / 3 of which are incinerated or landfilled, and this part of waste plastics contains a considerable amount of waste polyolefin plastic products.

[0003] As is known to all, the atomic composition of polyolefin is C and H, and theoretically it does not contain other heteroatoms, so if this part of waste plastics is not effectively utilized, it will not only cause serious environmental pollution, but also affect the ecological balance in the natural environment; on the other hand, it also causes serious waste of petrochemical resources.

[0004] The existing waste plastic disposal methods mainly include physical recycling, incineration power generation, landfill and the like, physical recycling refers to that relatively single and high-value waste plastics such as PET mineral water bottles are made into plastic products again after physical treatment for degraded use, and they cannot be recycled again after 2-3 cycles; incineration power generation can maximize the reduction of waste plastics, but it causes a large amount of carbon emissions; since the degradation period of waste plastics is as long as 200-500 years, landfill cannot fundamentally solve the problem of white pollution, and also occupies a large amount of land resources, so currently the international community no longer recommends landfill disposal of waste plastics.

[0005] As for China, high-value waste plastics are mostly physically recycled, and the most widely used polyolefin packaging film is often discarded and disposed of in incineration power plants due to its high recycling cost and little recycling value. Based on literature and field research, polyolefin chemical recycling is considered to be the only process that can achieve sustainable development. Among them, the pyrolysis process is concerned by researchers and enterprises in various countries due to its environmental protection, high yield and other advantages, and international major refining enterprises all have self-owned intellectual property rights of polyolefin pyrolysis process.

[0006] However, in terms of the existing technology, there are two problems in the polyolefin pyrolysis technology, on the one hand, due to the low thermal conductivity, the local overheating during pyrolysis leads to low pyrolysis oil yield, on the other hand, due to the random chain scission mechanism of polyolefin cracking, in order to ensure the oil yield, the pyrolysis product distribution range is wide, covering all distillates from naphtha to heavy oil, which needs further fractionation treatment in subsequent processing. SUMMARY

[0007] The purpose of the present application is to solve the problems of low pyrolysis oil yield and wide pyrolysis product distribution range in polyolefin pyrolysis, and provide a processing method and system of waste polyolefin.

[0008] To achieve the above object, the first aspect of the present application provides a processing method of waste polyolefin, wherein the method comprises the following steps:

[0009] (1) contacting waste polyolefin with product directing agent to carry out pyrolysis reaction to obtain pyrolysis oil gas and residue; wherein the product directing agent is naphthenic oil; the feeding temperature of the waste polyolefin is 80-120℃, and the feeding temperature of the product directing agent is 250-400℃;

[0010] The pyrolysis reaction comprises at least a first stage and a second stage; wherein the temperature of the first stage is 250-400℃, and the residence time of the first stage is 0.5-5.5s; the temperature of the second stage is 450-650℃, and the residence time of the second stage is 1-10mins;

[0011] (2) separating the pyrolysis product to obtain pyrolysis oil I with boiling point ≥40-60℃ and pyrolysis gas I with boiling point <40-60℃.

[0012] The second aspect of the present application provides a processing system of waste polyolefin, wherein the system comprises: a feeding machine 1, a closed hopper 2, a feeding dragon 3, a pyrolysis reaction device 4, a first heat exchanger 5, a second heat exchanger 6, a first gas-liquid separator 7, a third heat exchanger 8, a second gas-liquid separator 9 and a boiler 10;

[0013] Wherein, the feeding machine 1 is provided with an external heating jacket I; the closed hopper 2 is arranged between the feeding machine 1 and the feeding dragon 3;

[0014] The pyrolysis reaction device 4 is a vertical pyrolysis reactor, comprising a first feeding port, a second feeding port, a pyrolysis product outlet, a residue outlet, an internal heating coil and an external heating jacket II; the first feeding port is connected with the feeding dragon 3; the heat medium outlet of the internal heating coil is connected with the heat medium inlet of the external heating jacket II;

[0015] The cold medium inlet of the first heat exchanger 5 is the product directing agent inlet, the cold medium outlet of the first heat exchanger 5 is connected with the second feeding port of the pyrolysis reaction device 4; the heat medium inlet of the first heat exchanger 5 is connected with the pyrolysis product outlet of the pyrolysis reaction device 4, and the heat medium outlet of the first heat exchanger 5 is connected with the heat medium inlet of the second heat exchanger 6;

[0016] The cold medium inlet of the second heat exchanger 6 is connected with the heat medium outlet of the external heating jacket II, and the cold medium outlet of the second heat exchanger 6 is connected with the heat medium inlet of the external heating jacket I; the heat medium outlet of the second heat exchanger 6 is connected with the first gas-liquid separator 7;

[0017] The gas phase outlet of the first gas-liquid separator 7 is connected with the cooling medium inlet of the first heat exchanger 5 and the hot medium inlet of the third heat exchanger 8 respectively, and the hot medium outlet of the third heat exchanger 8 is connected with the second gas-liquid separator 9; the cold medium inlet of the third heat exchanger 8 is connected with the hot medium outlet of the external heating jacket I, and the cold medium outlet of the third heat exchanger 8 is connected with the boiler 10;

[0018] The gas phase outlet of the second gas-liquid separator 9 is connected with the boiler 10, and the boiler 10 is connected with the hot medium inlet of the internal heating coil.

[0019] Through the above technical scheme, the beneficial technical effects obtained by the present application are as follows:

[0020] 1) The processing method of waste polyolefin provided in the present application can improve the thermal conductivity of waste polyolefin in the pyrolysis process, avoiding the formation of large blocks or large groups of materials during the pyrolysis reaction process of waste polyolefin; on the other hand, it can make the high molecular chain crack into stable products with smaller molecular weight, prevent secondary reactions, avoid re-polymerization into products with larger molecular weight, and significantly improve the content of gasoline fraction.

[0021] 2) The processing system of waste polyolefin provided in the present application can efficiently utilize the heat in the pyrolysis reaction process by setting the external heating jacket I, internal heating coil, external heating jacket II, first heat exchanger, second heat exchanger, first gas-liquid separator, third heat exchanger, second gas-liquid separator and boiler, realizing full-system heat supply and energy optimization. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a structure schematic view of a waste polyolefin processing system provided in the present application.

[0023] Explanation of reference signs:

[0024] 1, feeding machine 2, locking hopper 3, feeding screw

[0025] 4, pyrolysis reaction device 5, first heat exchanger 6, second heat exchanger

[0026] 7, first gas-liquid separator 8, third heat exchanger 9, second gas-liquid separator

[0027] 10, boiler 11, water vapor cooler 12, water-gas separator

[0028] 13, sediment tank 14, fourth heat exchanger 15, fifth heat exchanger DETAILED DESCRIPTION

[0029] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the invention. Any numeric range recited is intended to include all values from the lower value to the upper value, inclusive of both values, and to also include any value approximately or roughly between the lower value and the upper value. Numeric ranges can be expressed as "from X to Y," where X and Y are numbers. Numeric ranges can be expressed as "from X to Y," where X is a number and Y is infinity. Numeric ranges can be expressed as "from X to Y," where X is a number and Y is a number greater than X. Numeric ranges can be expressed as "from X to Y," where X is a number and Y is a number less than X. Numeric ranges can be expressed as "from X to Y," where X is a number and Y is a number greater than or equal to X. Numeric ranges can be expressed as "from X to Y," where X is a number and Y is a number less than or equal to X.

[0030] A first aspect of the present application provides a method for processing waste polyolefin, wherein the method comprises the following steps:

[0031] (1) contacting waste polyolefin with a product directing agent to perform a pyrolysis reaction to obtain pyrolysis oil gas and residue; wherein the product directing agent is naphthenic oil; the feeding temperature of the waste polyolefin is 80-120℃, and the feeding temperature of the product directing agent is 250-400℃;

[0032] the pyrolysis reaction comprises at least a first stage and a second stage; wherein the temperature of the first stage is 250-400℃, and the residence time of the first stage is 0.5-5.5s; the temperature of the second stage is 450-650℃, and the residence time of the second stage is 1-10 mins;

[0033] (2) separating the pyrolysis product to obtain pyrolysis oil I with a boiling point ≥40-60℃ and pyrolysis gas I with a boiling point <40-60℃.

[0034] In step (1):

[0035] In a preferred embodiment of the present application, the waste polyolefin contains waste polyethylene and / or waste polypropylene; wherein the content of the waste polyethylene and / or waste polypropylene is ≥80wt%, preferably ≥90wt%.

[0036] In the present application, the waste polyolefin mainly contains waste polyethylene and / or waste polypropylene, in addition to which it can also contain moisture, mechanical impurities (such as masonry, bamboo and wood, paper and a small amount of metal) and a small amount of other types of waste plastics (such as waste polystyrene, polyethylene terephthalate, polyvinyl chloride, etc.). Preferably, the content of the water is ≤5wt%, the content of the mechanical impurities is ≤3wt%, and the content of the other types of waste plastics is ≤2wt%.

[0037] In a preferred embodiment of the present application, the length of the waste polyolefin is ≤100mm, preferably ≤50mm, and further preferably ≤20mm. The length of the waste polyolefin is the maximum value of the length between any two points of the irregular film.

[0038] In the present application, the shape of the waste polyolefin is not particularly limited, which can be a film or a shell of various shapes. In order to further improve the processing effect of the waste polyolefin, the waste polyolefin is preferably subjected to crushing treatment.

[0039] In a preferred embodiment of the present application, the waste polyolefin is subjected to drying treatment before being contacted with the product-directing agent; wherein the drying temperature is 80-120°C, preferably 90-105°C.

[0040] In the present application, the drying treatment can reduce the water content in the waste polyolefin, reduce the pyrolysis energy consumption, and reduce the water content in the pyrolysis oil. The water vapor discharged during the drying treatment can be sent to a sewage treatment plant after being cooled and then discharged after being treated to meet the requirements.

[0041] In a preferred embodiment of the present application, the content of cycloalkane in the cycloalkyl oil is ≥60wt%, preferably ≥80wt%.

[0042] In the present application, the cycloalkane in the cycloalkyl oil can provide hydrogen and alkyl groups for the pyrolysis reaction, which can significantly increase the content of alkane and cycloalkane in the pyrolysis oil I, thereby increasing the yield of the gasoline fraction. In the present application, the cycloalkane refers to a saturated hydrocarbon containing one or more rings, and each ring of the cycloalkane optionally has one or more alkane side chains. For example, it includes but is not limited to cyclopentane, cyclohexane, hydrogenated indene, decalin, decahydroanthracene, and alkyl substitutes of the above cycloalkanes.

[0043] In a preferred embodiment of the present application, the distillation range of the cycloalkyl oil is 40-350°C, preferably 150-350°C.

[0044] In a preferred embodiment of the present application, the cycloalkyl oil is selected from one or more of cycloalkyl crude oil, cycloalkyl lubricating oil, cycloalkyl transformer oil, refrigerator oil, and cycloalkyl rubber oil.

[0045] In the present application, the cycloalkyl lubricating oil, cycloalkyl transformer oil, refrigerator oil, and cycloalkyl rubber oil can be synthesized according to known methods or commercially available, or can be a fraction with a boiling point ≤350°C recovered from waste cycloalkyl lubricating oil, waste cycloalkyl transformer oil, waste refrigerator oil, and waste cycloalkyl rubber oil.

[0046] In a preferred embodiment of the present application, the mass ratio of the waste polyolefin to the product-directing agent is 1:0.01-0.5, preferably 1:0.1-0.2.

[0047] In a preferred embodiment of the present application, the feed temperature of the waste polyolefin is 95-110℃, and the feed temperature of the product directing agent is 330-370℃.

[0048] In the present application, the inventors have found that, by contacting the product directing agent at high temperature with the waste polyolefin at low temperature, the mixture of the two can be more uniform, and the heat transfer from the product directing agent at high temperature to the waste polyolefin at low temperature is facilitated.

[0049] In a preferred embodiment of the present application, the product directing agent is fed by spraying. In the present application, the product directing agent at high temperature is sprayed into the waste polyolefin at low temperature. When the product directing agent at high temperature contacts the waste polyolefin at low temperature, the heat carried by the product directing agent at high temperature is transferred to the waste polyolefin, which melts and shrinks under the heat, and then liquefies after wrapping the product directing agent, forming droplets. The droplets formed can better mix the product directing agent and the waste polyolefin, and provide space for the interaction between the product directing agent and the waste polyolefin.

[0050] In a preferred embodiment of the present application, the temperature of the first stage is 300-340℃, and the residence time of the first pyrolysis stage is 1-3s; the temperature of the second stage is 500-550℃, and the residence time of the second stage is 3-7min.

[0051] In the present application, the mixture of the waste polyolefin and the product directing agent falls from top to bottom into the pyrolysis reaction zone, which is divided into an upper region and a lower region. In the upper region, the first stage is carried out, and the waste polyolefin is heated to agglomerate, forming droplets coated with the product directing agent. The droplets formed continue to fall into the lower region, where the second stage, i.e., the pyrolysis reaction, is carried out, to obtain pyrolysis oil gas. Compared with the pyrolysis reaction without the first stage, the provision of the first stage can provide sufficient time conditions for the formation of droplets, significantly improve the pyrolysis effect, increase the generation amount of alkanes and naphthenes in the pyrolysis oil I, and increase the content of the gasoline fraction in the pyrolysis oil I.

[0052] In a preferred embodiment of the present application, the residue includes mechanical impurities and / or semi-coke generated by pyrolysis.

[0053] In step (2), the waste polyolefin is mixed with the product directing agent.

[0054] In a preferred embodiment of the present application, the separation of the pyrolysis oil gas is not specially limited in the present application, and the conventional separation methods in the art can be used in the present application.

[0055] In a preferred embodiment of the present application, the content of gasoline (IBP-180℃) in the pyrolysis oil I is 15-30wt%, the content of diesel (180-350℃) is 30-60wt%, and the content of distillate oil (350-500℃) is 10-25wt%.

[0056] In the present application, the distillation range of the pyrolysis oil I is analyzed by petroleum distillation range distribution method (gas chromatography, GC-D2887), and the analysis result shows that the pyrolysis oil I does not contain distillate >500℃. The pyrolysis oil I can be further separated according to actual needs, so as to obtain gasoline, diesel and distillate oil.

[0057] In a preferred embodiment of the present application, the separation comprises the following sub-steps:

[0058] (2-1), the pyrolysis gas is subjected to first separation to obtain pyrolysis oil II with boiling point ≥150-350℃ and pyrolysis gas II with boiling point <150-350℃;

[0059] (2-2), the pyrolysis gas II is at least divided into A part and B part; wherein the A part is returned to step (1) and added to the product directing agent; the B part is subjected to second separation to obtain pyrolysis oil III with boiling point ≥40-60℃ and pyrolysis gas I with boiling point <40-60℃;

[0060] (2-3), the pyrolysis oil II and pyrolysis oil III are mixed to obtain pyrolysis oil I.

[0061] In a preferred embodiment of the present application, the first separation and the second separation are not specially limited in the present application, and the conventional separation methods in the art can be used in the present application.

[0062] In a preferred embodiment of the present application, the A part accounts for 1-50% of the total mass of the pyrolysis gas II, preferably 5-15%; and the B part accounts for 99-50% of the total volume of the pyrolysis gas II, preferably 85-95%.

[0063] In a preferred embodiment of the present application, after the A part is returned to step (1) and added to the product directing agent, the amount of the product directing agent is reduced by 25-50%, preferably 30-45%; and the mass ratio of the A part to the reduced product directing agent is 1:0.2-1.2, preferably 1:0.4-0.8.

[0064] In the present application, a large amount of naphthenes generated in the pyrolysis process are contained in the pyrolysis gas II, and the pyrolysis gas II can be partially returned to the pyrolysis reaction for recycling. When the pyrolysis gas II is returned to the pyrolysis reaction, the amount of product directing agent used can be reduced according to the amount of pyrolysis gas II returned, so as to ensure that the content of naphthenes in the mixture of part A and the product directing agent is still ≥60wt%, preferably ≥80wt%.

[0065] In a preferred embodiment of the present application, the method further comprises step (3): burning the heat-released gas I, and using the heat generated by the burning as a heat exchange medium for the pyrolysis reaction, the first separation, the second separation, the drying of the waste polyolefin, the pyrolysis oil II and the pyrolysis oil III, in sequence.

[0066] The second aspect of the present application provides a processing system for waste polyolefin, wherein the system comprises: a feeding machine 1, a closed hopper 2, a feeding dragon 3, a pyrolysis reaction device 4, a first heat exchanger 5, a second heat exchanger 6, a first gas-liquid separator 7, a third heat exchanger 8, a second gas-liquid separator 9 and a boiler 10.

[0067] The feeding machine 1 is provided with an external heating jacket I; the closed hopper 2 is arranged between the feeding machine 1 and the feeding dragon 3.

[0068] The pyrolysis reaction device 4 is a vertical pyrolysis reactor, comprising a first feeding port, a second feeding port, a pyrolysis product outlet, a slag outlet, an internal heating coil and an external heating jacket II; the first feeding port is connected with the feeding dragon 3; the heat medium outlet of the internal heating coil is connected with the heat medium inlet of the external heating jacket II.

[0069] The cold medium inlet of the first heat exchanger 5 is a product directing agent inlet; the cold medium outlet of the first heat exchanger 5 is connected with the second feeding port of the pyrolysis reaction device 4; the heat medium inlet of the first heat exchanger 5 is connected with the pyrolysis product outlet of the pyrolysis reaction device 4, and the heat medium outlet of the first heat exchanger 5 is connected with the heat medium inlet of the second heat exchanger 6.

[0070] The cold medium inlet of the second heat exchanger 6 is connected with the heat medium outlet of the external heating jacket II, and the cold medium outlet of the second heat exchanger 6 is connected with the heat medium inlet of the external heating jacket I; the heat medium outlet of the second heat exchanger 6 is connected with the first gas-liquid separator 7.

[0071] The gas phase outlet of the first gas-liquid separator 7 is connected with the cooling medium inlet of the first heat exchanger 5 and the hot medium inlet of the third heat exchanger 8 respectively, and the hot medium outlet of the third heat exchanger 8 is connected with the second gas-liquid separator 9; the cold medium inlet of the third heat exchanger 8 is connected with the hot medium outlet of the external heating jacket I, and the cold medium outlet of the third heat exchanger 8 is connected with the boiler 10;

[0072] The gas phase outlet of the second gas-liquid separator 9 is connected with the boiler 10, and the boiler 10 is connected with the hot medium inlet of the internal heating coil, as shown in Figure 1

[0073] In the present application, by arranging the external heating jacket I, the internal heating coil, the external heating jacket II, the first heat exchanger, the second heat exchanger, the first gas-liquid separator, the third heat exchanger, the second gas-liquid separator and the boiler, the heat in the pyrolysis reaction process can be efficiently utilized, and the whole system heat supply and energy optimization can be realized.

[0074] In a preferred embodiment of the present application, the feeding machine 1 is selected from a bucket elevator and / or a pneumatic conveying machine. In the present application, the external heating jacket I arranged in the feeding machine is used to dry the waste polyolefin by using flue gas or steam waste heat from the boiler. One end of the feeding machine is connected with a material pit storing waste polyolefin, and the other end is connected with a feeding conveyor, so that the waste polyolefin in the material pit can be transported into the closed hopper.

[0075] In a preferred embodiment of the present application, when the feeding machine is a bucket elevator, the system further comprises a water vapor cooler 11; wherein the water vapor cooler is connected with the gas outlet of the closed hopper 2.

[0076] In the present application, the waste polyolefin from the feeding machine can realize water vapor separation in the closed hopper, and the separated water vapor can be cooled by the water vapor cooler, so that the water evaporated in the drying process of the waste polyolefin can be collected.

[0077] In a preferred embodiment of the present application, when the feeding machine is a pneumatic conveying machine, the system further comprises a water vapor cooler 11 and a water-gas separator 12; wherein the water vapor cooler 11 is connected with the gas outlet of the closed hopper 2, and the water-gas separator 12 is connected with the water vapor cooler 11. The water-gas separator is used to separate the conveying gas from the pneumatic conveying machine.

[0078] In a preferred embodiment of the present application, the closed hopper 2 is provided with a stirring device, and the present application does not make special limitation to the stirring device, which can be one or more of a screw belt type, an anchor type, a paddle type, a turbine type, a propelling type and a frame type. Preferably, a heating jacket is arranged outside the closed hopper 2.​

[0079] In a preferred embodiment of the present application, the lower end of the closed hopper 2 is a conical head; the closed hopper 2 is provided with a stirring device, the outermost edge of the stirring blade of the stirring device is parallel to the inner wall of the hopper; wherein the stirring device is immersed in the conical head, the distance between the stirring device and the inner wall of the conical head is less than 10 cm, preferably less than 5 cm.

[0080] In a preferred embodiment of the present application, the feeding screw 3 is provided with a cooling coil and / or a cooling sleeve. The cooling medium in the cooling coil and / or the cooling sleeve is cooling water, which is used to prevent the temperature of the feeding screw from rising due to long-time operation.

[0081] In a preferred embodiment of the present application, the feeding screw 3 comprises a horizontal conveying screw and a discharging screw. In the present application, the horizontal conveying screw is used to convey waste polyolefin, and the discharging screw is used to feed the waste polyolefin into the pyrolysis reaction device.

[0082] In a preferred embodiment of the present application, the horizontal conveying screw and the discharging screw are both provided with a bulk material screw, and the pitch of the bulk material screw is ≥ 4 times the length of the waste polyolefin, preferably 8-12 times.

[0083] In a preferred embodiment of the present application, the bulk material screw in the horizontal conveying screw and the discharging screw is selected from shafted screw or shaftless screw, preferably shaftless screw.

[0084] In a preferred embodiment of the present application, the outlet of the discharging screw is conical, and the longitudinal section angle of the conical shape is 15-60°.

[0085] In a preferred embodiment of the present application, in the pyrolysis reaction device 4, the first feeding port and the second feeding port are arranged at the upper part of the pyrolysis reaction device 4, the built-in heating coil and the pyrolysis product outlet are arranged at the lower half of the pyrolysis reaction device 4, and the slag outlet is arranged at the bottom of the pyrolysis reaction device 4.

[0086] In a preferred embodiment of the present application, the second feeding port is an aerosol nozzle, and the aerosol nozzle is inclined downward, and the included angle with the horizontal direction is α, 0 < α ≤ 5°.

[0087] In a preferred embodiment of the present application, the second feeding port is provided in multiple, and the multiple second feeding ports are arranged in opposition (i.e. symmetrically).

[0088] In a preferred embodiment of the present application, the pyrolysis reactor 4 further comprises a slag tank 13, wherein the slag tank 13 is arranged at the bottom of the pyrolysis reactor 4 and is connected to the slag outlet through a valve.

[0089] In the present application, the valve between the slag tank and the slag outlet can withstand a temperature of up to 550°C. A rake-type decoking device is arranged in the slag tank to periodically clean the residues generated inside the reactor. Cooling equipment, including but not limited to cooling water coils or external cooling jackets, is also arranged in the slag tank to cool the residues.

[0090] In a preferred embodiment of the present application, the system further comprises a fourth heat exchanger 14, wherein the hot medium inlet of the fourth heat exchanger 14 is connected to the liquid phase outlet of the first gas-liquid separator 7, the cold medium inlet of the fourth heat exchanger 14 is connected to the hot medium outlet of the external heating jacket I, and the cold medium outlet of the fourth heat exchanger 14 is connected to the boiler 10.

[0091] In a preferred embodiment of the present application, the system further comprises a fifth heat exchanger 15, wherein the hot medium inlet of the fifth heat exchanger 15 is connected to the hot medium outlet of the external heating jacket I, and the hot medium outlet of the fifth heat exchanger 15 is connected to the cold medium inlets of the third heat exchanger 7 and the fourth heat exchanger 14, respectively. The cold medium of the fifth heat exchanger 15 is selected from cooling water or air. In the processing system of the present application, each device is not specially limited and can be selected according to common knowledge.

[0092] The present application will be described in detail below through examples. The following examples are carried out in the processing system shown in Figure 1 The feeding machine is a pneumatic conveying machine, and a stirring device is arranged in the conical head at the lower end of the closed hopper. The stirring device is immersed in the conical head, and the stirring blades of the stirring device are conical plates matched with the conical head. The outermost edge of the conical plate is parallel to the inner wall of the hopper, and the distance between them is 3 cm.

[0093] The feeding auger is a shaftless screw, including a horizontal conveying auger and a discharging auger. Cooling coils are arranged in the horizontal conveying auger and the discharging auger, and the cooling coils use cooling water as the cooling medium. The pitch of the bulk material screw arranged in the horizontal conveying auger and the discharging auger is 5 times the length of the waste polyolefin. The outlet of the discharging auger is conical, and the longitudinal section angle of the cone is 30°.

[0094] The second feeding port of the pyrolysis reactor is an air mist nozzle, and four nozzles are oppositely arranged with an included angle α of 2.5° with the horizontal direction.

[0095] Waste polyethylene is broken into pieces, wherein the polyethylene content is 93.0wt%, the water content is 3wt%, the mechanical impurity content is 2wt%, the other plastic content is 2wt%, and the length is ≤20mm.

[0096] Waste polypropylene is broken into pieces, wherein the polypropylene content is 90.0wt%, the water content is 5wt%, the mechanical impurity content is 2wt%, the other plastic content is 3wt%, and the length is ≤20mm.

[0097] Example 1

[0098] (1) Waste polyethylene is transported into the pyrolysis reaction device after passing through the pneumatic conveying machine, the closed hopper and the feeding screw in turn; wherein, the waste polyethylene is dried at 100℃ by using the outer heating jacket of the pneumatic conveying machine and the outer heating jacket of the closed hopper during the transportation, and water vapor is generated; the generated water vapor is separated in the closed hopper, and the separated water vapor is cooled by the water vapor cooler and treated by the water vapor separator to obtain waste water, which is sent to the waste water treatment plant for treatment; the temperature of the waste polyethylene entering the pyrolysis reaction device is 105℃;

[0099] The product directing agent is preheated to 350℃ by the first heat exchanger and then atomized and injected into the pyrolysis reaction device; the pyrolysis reaction device is under the action of the built-in heating coil and the outer heating jacket II, the upper temperature is 320℃, and the lower temperature is 525℃; the first stage is carried out in the upper part of the pyrolysis reaction device, and the second stage is carried out in the lower part of the pyrolysis reaction device to obtain pyrolysis oil gas; wherein, the product directing agent is a fraction with a distillation range of 150-350℃ recovered from waste naphthenic lubricating oil, containing 91.2wt% naphthenes and 8.8wt% aromatics; the mass ratio of waste polyethylene to product directing agent is 1:0.1, the residence time of the first stage is 2s, and the residence time of the second stage is 5min;

[0100] (2) The obtained pyrolysis oil gas is cooled and then transported into the gas-liquid separator for gas-liquid separation to obtain pyrolysis oil I with a boiling point ≥50℃ and pyrolysis gas I with a boiling point <50℃.

[0101] Example 2

[0102] Waste polyethylene is transported into the pyrolysis reaction device after passing through the pneumatic conveying machine, the closed hopper and the feeding screw in turn; wherein, the waste polyethylene is dried at 100℃ by using the outer heating jacket of the pneumatic conveying machine and the outer heating jacket of the closed hopper during the transportation, and water vapor is generated; the generated water vapor is separated in the closed hopper, and the separated water vapor is cooled by the water vapor cooler and treated by the water vapor separator to obtain waste water, which is sent to the waste water treatment plant for treatment; the temperature of the waste polyethylene entering the pyrolysis reaction device is 100℃;

[0103] The product-directing agent is preheated to 330℃ by the first heat exchanger, and then atomized and injected into the pyrolysis reactor. The pyrolysis reactor is heated by the built-in heating coil and the external heating jacket II, and the temperature of the upper part is 310℃, and the temperature of the lower part is 510℃. The first stage is carried out in the upper part of the pyrolysis reactor, and the second stage is carried out in the lower part of the pyrolysis reactor, to obtain pyrolysis oil gas at 510℃. The product-directing agent is a fraction recovered from waste naphthenic lubricating oil, with a boiling point range of 150-350℃, containing 91.2wt% naphthenes and 8.8wt% aromatics. The mass ratio of waste polyethylene to product-directing agent is 1:0.2, the residence time of the first stage is 3s, and the residence time of the second stage is 6min.

[0104] The obtained pyrolysis oil gas is cooled to 380℃ in the first heat exchanger, and then enters the second heat exchanger to exchange heat with the heating medium from the external heating jacket II, and is further cooled to 280℃. Then it enters the first gas-liquid separator to carry out gas-liquid separation at 280℃ and 0.1MPa, to obtain pyrolysis oil II with a boiling point ≥280℃ and pyrolysis gas II with a boiling point <280℃.

[0105] The obtained pyrolysis gas II is divided into A part and B part, wherein the A part accounts for 10% of the total mass of the pyrolysis gas II, and the B part accounts for 90% of the total volume of the pyrolysis gas II. The A part is introduced into the first heat exchanger to join the product-directing agent, and the amount of the product-directing agent is reduced by 30%. The mass ratio of the A part to the reduced product-directing agent is 1:0.4. The B part is introduced into the third heat exchanger to exchange heat with the pyrolysis device from the external heating jacket I, and then sent to the second gas-liquid separator to carry out gas-liquid separation at 28℃ and 0.1MPa. The pyrolysis oil III with a boiling point ≥50℃ separated from the second gas-liquid separator is cooled to room temperature and then sent to the pyrolysis oil storage tank. The pyrolysis gas I with a boiling point <50℃ separated from the second gas-liquid separator is sent to the boiler.

[0106] The obtained pyrolysis oil II is introduced into the fourth heat exchanger to exchange heat with the heating medium from the external heating jacket I, and then cooled to room temperature and sent to the pyrolysis oil storage tank to mix with the pyrolysis oil III. The heating medium from the external heating jacket I is sent to the boiler. The steam generated by the boiler is introduced into the built-in heating coil.

[0107] Example 3

[0108] The waste polypropylene is sequentially transported by a pneumatic conveying machine, a closed hopper, and a feeding screw to a pyrolysis reactor; wherein the waste polypropylene is dried at 100℃ by using the outer heating jacket of the pneumatic conveying machine and the outer heating jacket of the closed hopper, and water vapor is generated; the generated water vapor is separated in the closed hopper, and the separated water vapor is cooled by a water vapor cooler and treated by a water vapor separator to obtain waste water, which is sent to a waste water treatment plant for treatment; the temperature of the waste polypropylene entering the pyrolysis reactor is 110℃;

[0109] The product directing agent is preheated to 350℃ by the first heat exchanger and then injected into the pyrolysis reactor; the pyrolysis reactor is heated by the built-in heating coil and the outer heating jacket II, and the upper part is at 350℃ and the lower part is at 550℃; the first stage is carried out in the upper part of the pyrolysis reactor, and the second stage is carried out in the lower part of the pyrolysis reactor to obtain pyrolysis oil gas at 550℃; wherein the product directing agent is a fraction with a distillation range of 150-350℃ recovered from waste naphthenic lubricating oil, containing 91.2wt% naphthenes and 8.8wt% aromatics, the mass ratio of waste polypropylene to product directing agent is 1:0.15, the residence time of the first stage is 1s, and the residence time of the second stage is 4min;

[0110] The obtained pyrolysis oil gas is cooled to 380℃ in the first heat exchanger, and then enters the second heat exchanger to exchange heat with the heating medium from the outer heating jacket II, and is further cooled to 280℃, and then enters the first gas-liquid separator to carry out gas-liquid separation at 280℃ and 0.1MPa to obtain pyrolysis oil II with a boiling point ≥280℃ and pyrolysis gas II with a boiling point <280℃;

[0111] The obtained pyrolysis gas II is divided into part A and part B, wherein part A accounts for 5% of the total mass of pyrolysis gas II, and part B accounts for 95% of the total volume of pyrolysis gas II; part A is introduced into the first heat exchanger to join the product directing agent, and the amount of the product directing agent is reduced by 45%, and the mass ratio of part A to the reduced product directing agent is 1:0.8; part B is introduced into the third heat exchanger to exchange heat with the pyrolysis device from the outer heating jacket I and then sent to the second gas-liquid separator to carry out gas-liquid separation at 28℃ and 0.1MPa; the pyrolysis oil III with a boiling point ≥50℃ separated from the second gas-liquid separator is cooled to room temperature and then sent to a pyrolysis oil tank; the pyrolysis gas I with a boiling point <50℃ separated from the second gas-liquid separator is sent to a boiler;

[0112] The obtained pyrolysis oil II is introduced into the fourth heat exchanger to exchange heat with the heating medium from the outer heating jacket I, and is cooled to room temperature and then mixed with pyrolysis oil III in a pyrolysis oil tank; the heating medium from the outer heating jacket I is sent to the boiler; and the steam generated by the boiler is introduced into the built-in heating coil.

[0113] Example 4

[0114] The difference from Example 1 is that the product directing agent is a naphthenic lubricating oil with added paraffin and aromatic hydrocarbons, the distillation range is 180-350℃, the content of naphthenic hydrocarbons is 64.1wt%, the content of paraffin hydrocarbons is 23.3wt%, and the content of aromatic hydrocarbons is 12.6wt%.

[0115] The temperature of the waste polyethylene entering the pyrolysis reaction device is 95℃, the product directing agent is preheated to 300℃ by the first heat exchanger and then atomized and sprayed into the pyrolysis reaction device, the temperature of the first stage is 280℃, and the residence time of the first stage is 4s; the temperature of the second stage is 480℃, and the residence time of the second stage is 7min.

[0116] Example 5

[0117] The difference from Example 1 is that the product directing agent is a naphthenic lubricating oil with added paraffin and aromatic hydrocarbons, the distillation range is 180-350℃, the content of naphthenic hydrocarbons is 64.1wt%, the content of paraffin hydrocarbons is 23.3wt%, and the content of aromatic hydrocarbons is 12.6wt%.

[0118] The temperature of the waste polyethylene entering the pyrolysis reaction device is 115℃, the product directing agent is preheated to 390℃ by the first heat exchanger and then atomized and sprayed into the pyrolysis reaction device, the temperature of the first stage is 360℃, and the residence time of the first stage is 0.5s; the temperature of the second stage is 570℃, and the residence time of the second stage is 3min.

[0119] Comparative Example 1

[0120] The same as Example 1, except that the product directing agent is omitted.

[0121] Comparative Example 2

[0122] The same as Example 1, except that the product directing agent and the waste polyethylene are fed from the lower part of the pyrolysis reaction device (i.e., the part where the second stage reaction is carried out) at 525℃ for 5min.

[0123] Comparative Example 3

[0124] The same as Example 1, except that the feeding temperature of the product directing agent is 150℃, and the feeding temperature of the waste polyethylene is 60℃.

[0125] Dry ash-free base three-phase yield of waste plastics:

[0126] The present application pyrolyzes the raw material including waste plastics and product directing agent under the same conditions, analyzes the generation amount of pyrolysis oil, pyrolysis gas and pyrolysis semi-coke quality; then combines the generation amount of residue, pyrolysis oil I and pyrolysis gas I in Examples 1-5 and Comparative Examples 1-3, and calculates the dry ash-free base three-phase yield of waste plastics itself. The dry ash-free base three-phase yield of waste plastics itself in Examples 1-5 and Comparative Examples 1-3 is shown in Table 1.

[0127] Wherein, the moisture and ash content of waste polyolefin is determined by reference to the industrial analysis method of coal (GB / T212-2008). The mass of residue and pyrolysis oil I is obtained by weighing, and the mass of pyrolysis semi-coke is equal to the mass of residue minus the mass of ash.

[0128] The composition of pyrolysis gas is analyzed by gas chromatography, the volume flow of pyrolysis gas is obtained by reading the coal gas meter before being sent to the boiler, then the mass flow is calculated according to the composition of pyrolysis gas, and the mass of pyrolysis gas is obtained by integration, and the calculation method is as follows:

[0129]

[0130] In the formula, m gas is the mass of pyrolysis gas, g; t is the product calculation period time, s; V i is the volume flow of pyrolysis gas component i, L / s; V i is the molar mass of pyrolysis gas component i, g / mol.

[0131] According to the mass of three-phase products, the dry ash-free base three-phase yield of pyrolysis semi-coke, pyrolysis oil and pyrolysis gas of waste plastics itself is calculated according to the following formula:

[0132]

[0133]

[0134]

[0135] In the formula, y oil , y gas , y char are the dry ash-free base yield of pyrolysis oil, pyrolysis gas and pyrolysis semi-coke of waste plastics itself, %; m, m oil , m gas , m char are the mass of waste polyolefin, pyrolysis oil, pyrolysis gas and pyrolysis semi-coke in the co-pyrolysis process of waste plastics and product directing agent, g; M ad and A ad are the moisture and ash content in waste polyolefin, %; m oil-agent , mgas-agent , m char-agent are the mass of pyrolysis oil, pyrolysis gas and pyrolysis semi-coke generated when the product directing agent is separately reacted under the same reaction conditions.

[0136] Table 1

[0137]

[0138] Distillation range and hydrocarbon composition of pyrolysis oil generated by waste plastics themselves:

[0139] Part of the pyrolysis oil I in the present application comes from the pyrolysis of waste plastics, and part comes from the product directing agent. The distillation range and hydrocarbon composition of the pyrolysis oil generated by the product directing agent when it is separately pyrolyzed under the same conditions are analyzed; then the distillation range and hydrocarbon composition of the pyrolysis oil I in Examples 1-5 and Comparative Examples 1-3 are combined, and the distillation range and hydrocarbon composition of the pyrolysis oil generated by waste plastics themselves can be calculated.

[0140] Among them, the distillation range of the pyrolysis oil I obtained in Examples 1-5 and Comparative Examples 1-3 is analyzed by petroleum fraction boiling range distribution determination method (gas chromatography, GC-D2887), and the hydrocarbon composition in the pyrolysis oil I obtained in Examples 1-5 and Comparative Examples 1-3 is analyzed by GC-MS.

[0141] Taking waste polyethylene as an example, the distillation range and hydrocarbon composition of the pyrolysis oil generated by waste plastics themselves can be calculated according to the following formula:

[0142]

[0143] In the formula, y i-PE is the content of product component i based on waste polyethylene, %; m total is the total mass of PE and product directing agent in the pyrolysis process, g; y i-total is the content of component i in the product obtained by co-pyrolysis of waste polyethylene and product directing agent, %; m agent is the mass of product directing agent added in the pyrolysis process, g; y i-agent is the content of component i when the product directing agent is separately pyrolyzed, %; m PE is the mass of waste polyethylene used in the co-pyrolysis process, g.

[0144] Table 2

[0145]

[0146]

[0147] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including that each technical feature is combined in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A method for processing waste polyolefins, characterized in that, The processing method comprises the following steps: (1) contacting waste polyolefin with product directing agent to carry out pyrolysis reaction, obtaining pyrolysis oil gas and residue; wherein the product directing agent is naphthenic oil, the content of naphthenes in the naphthenic oil is ≥60wt%, the distillation range of the naphthenic oil is 40-350℃; the feeding temperature of the waste polyolefin is 80-120℃, the feeding temperature of the product directing agent is 250-400℃; the mass ratio of the waste polyolefin to the product directing agent is 1:0.01-0.5; The pyrolysis reaction comprises at least first stage and second stage; wherein the temperature of the first stage is 250-400℃, the residence time of the first stage is 0.5-5.5s; the temperature of the second stage is 450-650℃, the residence time of the second stage is 1-10mins; Wherein, the mixture of waste polyolefin and product directing agent falls from top to bottom into the pyrolysis reaction zone, the pyrolysis reaction zone is divided into upper region and lower region, the first stage is carried out in the upper region, the second stage is carried out in the lower region; (2) separating the pyrolysis oil gas to obtain pyrolysis oil I and pyrolysis gas I, the boiling point of the separation of pyrolysis oil I and pyrolysis gas I is 40-60℃.

2. The method of processing according to claim 1, wherein, The waste polyolefin contains waste polyethylene and / or waste polypropylene.

3. The method of processing according to claim 2, wherein, The content of the waste polyethylene and / or waste polypropylene is ≥80wt%.

4. The method of processing according to claim 3, wherein, The content of the waste polyethylene and / or waste polypropylene is ≥90wt%.

5. The method of processing according to claim 1, wherein, The content of naphthenes in the naphthenic oil is ≥80wt%.

6. The method of processing according to claim 1, wherein, The distillation range of the naphthenic oil is 150-350℃.

7. The method of processing according to claim 1, wherein, The naphthenic oil is selected from one or more of naphthenic crude oil, naphthenic lubricating oil, naphthenic transformer oil, naphthenic rubber oil.

8. The method of processing according to any one of claims 1-7, wherein, The mass ratio of the waste polyolefin to the product directing agent is 1:0.1-0.

2.

9. The method of processing according to any one of claims 1-7, wherein, The feeding temperature of the waste polyolefin is 95-110℃, the feeding temperature of the product directing agent is 330-370℃.

10. The method of processing according to any one of claims 1-7, wherein, The feeding mode of the product directing agent is spraying.

11. The method of processing according to any one of claims 1-7, wherein, The temperature of the first stage is 300-340℃, the residence time of the first stage is 1-3s; the temperature of the second stage is 500-550℃, the residence time of the second stage is 3-7min.

12. The method of processing according to any one of claims 1-7, wherein, The separation comprises the following sub-steps: (2-1), carrying out first separation on the pyrolysis oil gas to obtain pyrolysis oil II and pyrolysis gas II, the boiling point of the separation of pyrolysis oil II and pyrolysis gas II is 150-300℃; (2-2), separating the pyrolysis gas II into at least A part and B part; wherein the A part returns to step (1) to be added to the product directing agent; carrying out second separation on the B part to obtain pyrolysis oil III and pyrolysis gas I, the boiling point of the separation of pyrolysis oil III and pyrolysis gas I is 40-60℃; (2-3), mixing the pyrolysis oil II and pyrolysis oil III to obtain pyrolysis oil I.

13. The method of processing according to claim 12, wherein, The A part accounts for 1-50% of the total mass of the pyrolysis gas II.

14. The method of processing according to claim 13, wherein, The A part accounts for 5-15% of the total mass of the pyrolysis gas II.

15. The method of processing according to claim 12, wherein, The B part accounts for 99-50% of the total volume of the pyrolysis gas II.

16. The method of processing according to claim 15, wherein, The B part accounts for 85-95% of the total volume of the pyrolysis gas II.

17. The method of processing according to claim 12, wherein, After the A part is added to the product directing agent in step (1), the amount of the product directing agent is reduced by 25-50%.

18. The method of processing according to claim 17, wherein, After the A part is added to the product directing agent in step (1), the amount of the product directing agent is reduced by 30-45%.

19. The method of processing according to claim 17, wherein, The mass ratio of the A part to the reduced product directing agent is 1:0.2-1.

2.

20. The method of processing according to claim 19, wherein, The mass ratio of the A part to the reduced product directing agent is 1:0.4-0.

8.

21. The process of any one of claims 1-7, wherein, The method further comprises step (3): the pyrolysis gas I is combusted, and the heat generated by the combustion provides heat exchange medium for the pyrolysis reaction, the first separation, the second separation, the drying of the waste polyolefin, the pyrolysis oil II and the pyrolysis oil III in sequence.

22. A processing system for waste polyolefins using the processing method according to any one of claims 1 to 21, characterized in that, The system comprises a feeding machine (1), a closed hopper (2), a feeding dragon (3), a pyrolysis reaction device (4), a first heat exchanger (5), a second heat exchanger (6), a first gas-liquid separator (7), a third heat exchanger (8), a second gas-liquid separator (9) and a boiler (10). The feeding machine (1) is provided with an external heating jacket I; the closed hopper (2) is arranged between the feeding machine (1) and the feeding dragon (3); The pyrolysis reaction device (4) is a vertical pyrolysis reactor, comprising a first feeding port, a second feeding port, a pyrolysis product outlet, a slag outlet, an internal heating coil and an external heating jacket II; the first feeding port is connected with the feeding dragon (3); the heat medium outlet of the internal heating coil is connected with the heat medium inlet of the external heating jacket II; The cold medium inlet of the first heat exchanger (5) is a product directing agent inlet, the cold medium outlet of the first heat exchanger (5) is connected with the second feeding port of the pyrolysis reaction device (4); the heat medium inlet of the first heat exchanger (5) is connected with the pyrolysis product outlet of the pyrolysis reaction device (4), and the heat medium outlet of the first heat exchanger (5) is connected with the heat medium inlet of the first heat exchanger (6); The cold medium inlet of the second heat exchanger (6) is connected with the heating medium outlet of the external heating jacket II, and the cold medium outlet of the second heat exchanger (6) is connected with the heating medium inlet of the external heating jacket I; the heat medium outlet of the second heat exchanger (6) is connected with the first gas-liquid separator (7); The gas phase outlet of the first gas-liquid separator (7) is connected with the cooling medium inlet of the first heat exchanger (5) and the heat medium inlet of the third heat exchanger (8) respectively, the heat medium outlet of the third heat exchanger (8) is connected with the second gas-liquid separator (9); the cold medium inlet of the third heat exchanger (8) is connected with the heat medium outlet of the external heating jacket I, and the cold medium outlet of the third heat exchanger (8) is connected with the boiler (10); The gas phase outlet of the second gas-liquid separator (9) is connected with the boiler (10), and the boiler (10) is connected with the heat medium inlet of the internal heating coil.

23. The processing system of claim 22, wherein, The feeding machine (1) is selected from a bucket elevator and / or a pneumatic conveying machine.

24. The processing system of claim 23, wherein, The feeding machine (1) is a bucket elevator, and the system further comprises a water vapor cooler (11).

25. The processing system of claim 23, wherein, When the feeding machine (1) is a pneumatic conveying machine, the system further comprises a water vapor cooler (11) and a water vapor separator (12).

26. The processing system of any of claims 22-25, wherein, The system further comprises a fourth heat exchanger (14), wherein the hot medium inlet of the fourth heat exchanger (14) is connected with the liquid phase outlet of the first gas-liquid separator (7), the cold medium inlet of the fourth heat exchanger (14) is connected with the hot medium outlet of the external heating jacket I, and the cold medium outlet of the fourth heat exchanger (14) is connected with the boiler (10).

27. The processing system of claim 26, wherein, The system further comprises a fifth heat exchanger (15), wherein the hot medium inlet of the fifth heat exchanger (15) is connected with the hot medium outlet of the external heating jacket I, and the hot medium outlets of the fifth heat exchanger (15) are respectively connected with the cooling medium inlets of the third heat exchanger (8) and the fourth heat exchanger (14).

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