A process and system for the processing of waste plastics by contact cracking

Abstract

A processing method and processing system for waste plastic contact cracking, the method comprising: S1, plastic raw materials enter a plastic liquefaction unit for liquefaction treatment to obtain liquefied plastic; S2, the liquefied plastic enters a plastic viscosity reduction unit for viscosity reduction cracking treatment to obtain viscosity-reduced liquefied plastic oil and first dry gas; S3, in a contact cracking reaction unit, the liquefied plastic oil is mixed with a high-temperature contact agent in a mixer, and the mixture is subjected to a cracking reaction in a contact cracking reactor to obtain reaction oil gas, spent contact agent and carbon-containing ash; S4, the reaction oil gas enters a separation unit for separation treatment to obtain second dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction; the spent contact agent and carbon-containing ash enter a regeneration unit to react with oxygen to regenerate to obtain regenerated contact agent and regenerated flue gas; and the regenerated contact agent returns to the contact cracking reaction unit for continuous use. The present application realizes resource utilization of waste plastics.

Description

Technical Field

[0001] This disclosure relates to the field of waste plastic resource recycling, specifically to a processing method and system for fluidized bed cracking of waste plastics. Background Technology

[0002] With technological advancements and industrial development, plastics are now widely used as packaging materials in daily life. Used waste plastics cannot decompose naturally. While only a few types can be recycled through specific channels, a large amount ends up in landfills as household waste, occupying significant space due to their slow decomposition. Especially in recent years, the generation of waste plastics has increased dramatically, making rapid and environmentally friendly recycling an urgent task.

[0003] The simplest way to dispose of waste plastics is through direct incineration, but this produces toxic gases harmful to human health and causes secondary environmental pollution. Waste plastic pyrolysis technology involves breaking down waste plastics under anaerobic or oxygen-deficient conditions through heating or the presence of a catalyst. This process breaks down polymers into lower molecular weight substances, yielding gasoline, kerosene, diesel fractions, and some pyrolysis gases. Waste plastic pyrolysis technology alleviates the pollution caused by waste plastics and enables their recycling, representing an important direction for the resource-based treatment of waste plastics.

[0004] Currently, waste plastic pyrolysis and recycling technologies mainly include waste plastic pyrolysis and catalytic pyrolysis. CN107746722A discloses a method and equipment for producing gasoline and diesel from waste plastic pyrolysis. This system dissolves crushed and impurity-removed waste plastic in liquid pyrolysis oil, and through precise temperature control, performs melting, dehydration, dechlorination, and pyrolysis upgrading. The process requires a large amount of solvent oil. CN101374930A discloses a method and apparatus for contact decomposition of waste plastic, belonging to catalytic pyrolysis technology. It uses a heated and stirred rotary kiln as a reactor, with an FCC catalyst as the heat medium and catalytic center, and adds appropriate amounts of Ca and Fe compounds to decompose the waste plastic. However, this device requires the contact agent in the reactor to be removed and regenerated after a period of operation. Many other waste plastic pyrolysis technologies use batch pyrolysis reactors. These methods suffer from small processing scales and fail to remove impurities from the products. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a processing method and system for contact cracking of waste plastics, which can continuously fluidize and crack waste materials, realize the effective utilization of waste plastic resources, and effectively remove impurities from the products.

[0006] In a first aspect, the present invention provides a method for processing waste plastics through contact cracking, the method comprising the following steps:

[0007] S1. Plastic raw materials enter the plastic liquefaction unit for liquefaction treatment to obtain liquefied plastic;

[0008] S2. The liquefied plastic enters the plastic viscosity reduction unit for viscosity reduction cracking treatment to obtain viscosity-reduced cracked liquefied plastic oil and first dry gas;

[0009] S3. In the contact cracking reaction unit, the liquefied plastic oil and the high-temperature contact agent are mixed in a mixer. The mixture undergoes a cracking reaction in the contact cracking reactor to obtain reaction oil gas, unused contact agent and carbonized ash.

[0010] S4. The reaction oil and gas enter the separation unit for separation processing to obtain second dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction;

[0011] The recycled contact agent and charred ash enter the regeneration unit, react with oxygen to burn off the char and regenerate, yielding regenerated contact agent and regenerated flue gas; the regenerated contact agent is returned to the contact cracking reaction unit for continued use.

[0012] Optionally, before step S1, the method further includes: the plastic raw material enters the hot melt dehydration and dechlorination unit, and under a first temperature condition, the chlorine-containing plastic raw material is melted and dehydrated to obtain dehydrated plastic; then the dehydrated plastic is heated to a second temperature for dechlorination treatment to obtain dehydrated and dechlorinated plastic and hydrogen chloride gas; wherein, the first temperature is 100-170°C, and the second temperature is 150-370°C; the dehydrated and dechlorinated plastic directly enters the plastic liquefaction unit.

[0013] Optionally, the dehydrated and dechlorinated plastic is sequentially cooled and pulverized in a cooling and pulverizing unit to obtain dehydrated and dechlorinated plastic particles; the dehydrated and dechlorinated plastic particles enter the plastic liquefaction unit.

[0014] Optionally, the method further includes: the hydrogen chloride-containing gas entering the hydrogen chloride absorption unit and contacting the hydrogen chloride absorbent for hydrogen chloride absorption treatment; optionally, the hydrogen chloride-containing gas entering the hydrogen chloride absorption unit is performed under the action of a vacuum system; the hydrogen chloride absorbent is water or an alkaline solution with a pH greater than 7.

[0015] Optionally, in step S3, at least a portion of the first dry gas and / or at least a portion of the second dry gas enter the regeneration unit, so that the recycled contact agent and the charred ash undergo a complete combustion reaction in the presence of oxygen and dry gas to obtain regenerated flue gas and regenerated contact agent.

[0016] Preferably, based on the total weight of the contact agent to be regenerated, the carbon content of the contact agent to be regenerated is 0.5 to 5.0% by weight.

[0017] Optionally, in step S1, the plastic liquefaction unit uses a heated conveying device to perform the liquefaction process; optionally, the heated conveying device includes a first screw-type heated conveying device; preferably, the first screw-type heated conveying device is selected from a twin-screw or single-screw heated conveying device with heating; preferably, the process conditions for the liquefaction process include: an outlet temperature of 380-500℃, preferably 400-450℃; and a residence time of 5-30 min, preferably 5-15 min.

[0018] Optionally, in step S2, the plastic viscosity reduction unit uses an adiabatic viscosity reduction reactor to perform the viscosity reduction cracking treatment; preferably, the process conditions for the viscosity reduction cracking treatment include: a reaction temperature of 380-500℃, preferably 390-450℃, more preferably 390-420℃; and a residence time of 10-90 min, preferably 20-70 min, more preferably 30-70 min.

[0019] Optionally, in step S3, the operating conditions of the mixer are as follows: the mass ratio of the contact agent to the plastic raw material is 5 to 30:1, preferably 6 to 20:1; the mixing time is 0.1 to 2 seconds; and the temperature of the recycled contact agent is 490℃ to 750℃.

[0020] The operating conditions of the dense phase fluidized bed reactor are as follows: the mass ratio of contact agent to plastic raw material is 8-40:1, preferably 12-30:1; the reaction temperature is 490-750℃, preferably 500-650℃; and the bed linear velocity is 0.2-1.0 m / s, preferably 0.4-0.8 m / s.

[0021] Preferably, steam is introduced into the dense phase fluidized bed reactor; the mass ratio of steam to plastic raw material is 0.01 to 0.5:1, preferably 0.01 to 0.3:1.

[0022] Optionally, in step S3, the contact agent is selected from one or more of silica-alumina materials, quartz sand, or coal coke powder; preferably, the particle size of the contact agent is 150–1000 μm; optionally, the silica-alumina material is selected from catalysts containing molecular sieves and / or catalysts without molecular sieves; preferably, the molecular sieve is selected from one or more of X-type molecular sieves, Y-type molecular sieves, mordenite, ZSM-5, layered clay molecular sieves, and SAPO; preferably, the catalyst without molecular sieves is selected from catalysts prepared using one or more of the first raw materials as raw materials, wherein the first raw materials include amorphous materials. The catalyst may contain amorphous silica, kaolin, montmorillonite, palygorskite, illite, chlorite, boehmite, and silica; or the catalyst without molecular sieves may be selected from catalysts prepared using one or more of the second raw materials that have undergone acid washing, calcination, and sieving, wherein the second raw materials include amorphous silica, kaolin, montmorillonite, palygorskite, illite, and chlorite; or catalysts prepared using one or more of the second raw materials that have undergone acid washing, calcination, and sieving, together with boehmite and / or silica; optionally, the coal coke powder may be coal powder and / or petroleum coke powder.

[0023] Optionally, the regeneration process is carried out in a dense-phase fluidized bed regenerator; preferably, the process conditions for the regeneration process include: an air residence time of 0.5 to 60 seconds, preferably 1.0 to 10 seconds, a vaporization temperature of 600 to 750°C, preferably 600 to 700°C, an introduced gas containing 10 to 50% oxygen by volume, and a linear velocity of 0.05 to 0.6 m / s, preferably 0.2 to 0.4 m / s.

[0024] Optionally, the hot-melt dehydration and dechlorination unit includes a second screw-type heating and conveying device and a vacuum device connected to the second screw-type heating and conveying device; preferably, the second screw-type heating and conveying device is selected from a twin-screw or single-screw heating and conveying device; preferably, the process conditions for the melting dehydration and dechlorination treatment include: a first temperature of 120-150℃; a residence time of 0.05-1h, preferably 0.05-0.5h; a second temperature of 220-350℃, more preferably 300-330℃; a residence time of 0.05-0.5h, preferably 0.1-0.2h; and a vacuum degree of 50-300mmHg, preferably 50-150mmHg.

[0025] Preferably, the heating rate from the first temperature to the second temperature is 50–200 °C / min, more preferably 50–150 °C / min;

[0026] Optionally, the particle size of the dehydrated and dechlorinated plastic particles is 100–2000 μm.

[0027] Optionally, the plastic raw material includes one or more of LDPE, HDPE, PS, PP, PET and PVC; optionally, the chlorine content in the plastic raw material is less than 10% by weight; the ash content in the plastic raw material is 1-40% by weight, preferably 3-20% by weight.

[0028] Secondly, the present invention provides a processing system for contact cracking of waste plastics, comprising a plastic liquefaction unit, a plastic de-viscosity unit, a contact cracking reaction unit, a separation unit, and a regeneration unit connected in sequence; the plastic liquefaction unit includes a raw material inlet and a liquefied plastic outlet, and is configured to liquefy the plastic raw material; the plastic de-viscosity unit includes a liquefied plastic inlet, a liquefied plastic oil outlet, and a first dry gas outlet, and is configured to de-viscosify and crack the liquefied plastic; the contact cracking reaction unit includes a mixer and a dense phase fluidized bed reactor connected in series, the mixer having a cracking raw material inlet, a contact agent inlet, and a contact agent-oil mixture outlet, and the dense phase fluidized bed reactor having... The unit comprises an oil-fuel mixture inlet, a reaction oil-gas outlet, and a pre-regenerated contact agent outlet; the cracking feedstock inlet is connected to the liquefied plastic oil outlet, and the contact cracking reaction unit is configured to perform cracking reaction treatment on liquefied waste plastic oil; the separation unit includes a separation inlet, a second dry gas inlet, a liquefied gas outlet, a gasoline fraction outlet, a diesel fraction outlet, and a wax oil fraction outlet; the separation inlet is connected to the reaction oil-gas outlet of the contact cracking reaction unit, and the separation unit is configured to separate the reaction oil-gas; the regeneration unit includes a pre-regenerated contact agent inlet, an oxygen-containing gas inlet, a regenerated contact agent outlet, and a regeneration flue gas outlet; the regenerated contact agent outlet is connected to the contact agent inlet of the contact cracking reaction unit.

[0029] Optionally, the processing system further includes a waste plastic hot-melt dehydration and dechlorination unit, a cooling and pulverizing unit, and a hydrogen chloride absorption unit; the waste plastic hot-melt dehydration and dechlorination unit includes a raw material inlet, a dehydrated and dechlorinated plastic outlet, and a hydrogen chloride-containing gas outlet; the waste plastic hot-melt dehydration and dechlorination unit is configured to perform melting dehydration and dechlorination treatment on chlorinated plastics; the cooling and pulverizing unit is configured to cool and pulverize the dehydrated and dechlorinated plastics from the waste plastic hot-melt dehydration and dechlorination unit; the hydrogen chloride absorption unit includes a hydrogen chloride-containing gas inlet and a hydrogen chloride absorbent; the hydrogen chloride-containing gas inlet is connected to the hydrogen chloride-containing gas outlet of the waste plastic hot-melt dehydration and dechlorination unit.

[0030] Preferably, the regeneration unit further includes a dry gas inlet, which is connected to the first dry gas outlet of the plastic de-adhesion unit and / or the second dry gas outlet of the separation unit;

[0031] Preferably, the plastic liquefaction unit includes a heating conveying device; optionally, the heating conveying device includes a first screw-type heating conveying device; preferably, a twin-screw heating conveying device.

[0032] Preferably, the plastic hot melt dehydration and dechlorination unit includes a second screw-type heating and conveying device and a vacuum device connected to the second screw-type heating and conveying device; preferably, the second screw-type heating and conveying device is selected from a twin-screw heating and conveying device.

[0033] Compared with existing technologies, the processing method and system for contact cracking of waste plastics provided by this invention have the following advantages: This invention is used to achieve green resource recycling of waste plastics. It liquefies and reduces the viscosity of plastic raw materials through liquefaction and viscosity reduction cracking. Then, after mixing with a high-temperature contact agent in an oil-agent mixer, the mixture enters a reactor for cracking. This allows the plastic to rapidly pyrolyze in a liquid state in contact with the high-temperature contact agent. The cracking products, along with a small amount of steam, are agitated by the contact agent to accelerate the diffusion of gaseous products, reducing product residence time and achieving a more ideal product distribution. It also removes heteroatoms from the plastic and separates the contact agent from the gaseous products in the reactor. By producing gaseous and liquid products through contact cracking, the contact agent can be regenerated and recycled. This allows for continuous waste plastic processing, improving processing efficiency. It is highly adaptable to plastic raw materials, eliminating the need for crushing and washing. Waste plastics from landfills can be dehydrated and dechlorinated on-site, and subsequent cracking and recycling can be centralized, facilitating large-scale production and reducing processing costs. Compared with fast fluidized bed contact cracking, the contact cracking process provided by this invention simplifies the contact agent circulation process and reduces equipment investment and operation difficulty.

[0034] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0035] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. Figure 1 This is an exemplary flowchart of a processing method and system for contact cracking of waste plastics provided in this disclosure.

[0036] in:

[0037] 1- Plastic raw material storage tank; 2- Hot melt dehydration and dechlorination unit; 3- Crushing equipment

[0038] 4-Plastic liquefaction unit; 5-Plastic viscosity reduction unit; 6-Mixer

[0039] 7-Contact cracking reactor; 8-Regeneration unit; 9-Separation unit

[0040] 10-Hydrogen chloride absorption unit 11-24-pipeline Detailed Implementation

[0041] The following provides a detailed description of specific embodiments of this disclosure. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit this disclosure.

[0042] Firstly, this disclosure provides a processing method for contact cracking of waste plastics, such as... Figure 1 As shown, the method includes the following steps:

[0043] S1. Plastic raw materials enter the plastic liquefaction unit for liquefaction treatment to obtain liquefied plastic;

[0044] S2. The liquefied plastic enters the plastic viscosity reduction unit for viscosity reduction cracking treatment to obtain viscosity-reduced cracked liquefied plastic oil and first dry gas;

[0045] S3. In the contact cracking reaction unit, the liquefied plastic oil and the high-temperature contact agent are mixed in a mixer. The mixture undergoes a cracking reaction in the contact cracking reactor to obtain reaction oil gas, unused contact agent and carbonized ash.

[0046] S4. The reaction oil and gas enter the separation unit for separation processing to obtain second dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction;

[0047] The awaited contact agent and the carbonized ash enter the regeneration unit, where the awaited contact agent is regenerated in the presence of oxygen to obtain regenerated contact agent and regenerated flue gas; the regenerated contact agent is then returned to the contact cracking reaction unit for continued use.

[0048] In one specific embodiment, the plastic raw material includes one or more of low-density polyethylene (LDPE), high-density polyethylene (HDPE), polystyrene (PS), polypropylene (PP), polyethylene terephthalate (PET), and polyvinyl chloride (PVC).

[0049] Optionally, the chlorine content in the plastic raw material is less than 10% by weight; the ash content in the plastic raw material is 1-40% by weight, preferably 3-20% by weight. The plastic raw material in this disclosure can be directly sourced from waste plastics in landfills.

[0050] In one specific embodiment, when the plastic raw material contains chlorine, before step S1, the method further includes: the plastic raw material entering a hot melt dehydration and dechlorination unit, where the chlorine-containing plastic raw material is melted and dehydrated under a first temperature condition to obtain dehydrated plastic; then the dehydrated plastic is heated to a second temperature for dechlorination treatment to obtain dehydrated and dechlorinated plastic and hydrogen chloride gas; wherein the first temperature is 100-170°C and the second temperature is 150-370°C; the dehydrated and dechlorinated plastic directly enters the plastic liquefaction unit.

[0051] In one optional embodiment, the dehydrated and dechlorinated plastic is sequentially cooled and pulverized in a cooling and pulverizing unit to obtain dehydrated and dechlorinated plastic particles; the dehydrated and dechlorinated plastic particles can be easily transported or enter the plastic liquefaction unit.

[0052] In this disclosure, the waste plastic hot melt dehydration and dechlorination steps and the waste plastic liquefaction steps can use the same rapid heating liquefaction conveying equipment, or each can use a separate rapid heating liquefaction conveying equipment; for example, a screw-type heating conveying equipment with heating, etc.

[0053] In a preferred embodiment, the method further includes a hydrogen chloride absorption unit:

[0054] The hydrogen chloride-containing gas enters the hydrogen chloride absorption unit and comes into contact with the hydrogen chloride absorbent for hydrogen chloride absorption treatment; optionally, the hydrogen chloride-containing gas enters the hydrogen chloride absorption unit under the action of a vacuum system.

[0055] The preferred embodiment includes a plastic hot-melt dehydration and dechlorination step and a hydrogen chloride absorption step, which decomposes the chlorine in the waste PVC plastic into the gas phase. A vacuum system is used to quickly separate the HCl, avoiding secondary HCl reactions, improving the dechlorination efficiency of the waste plastic, and reducing the corrosion pressure on subsequent equipment. The hydrogen chloride absorbent is water or an alkaline solution with a pH greater than 7; the alkaline solution can be one or more of sodium hydroxide solution, potassium hydroxide solution, calcium hydroxide solution, sodium bicarbonate solution, sodium carbonate solution, and ammonia water.

[0056] In one specific embodiment, the charred ash and the awaited contact agent obtained from the cracking reaction in the contact cracking reaction unit described in step S3 enter the regeneration unit. Under the condition of oxygen presence, the awaited contact agent and the carbon on the charred ash undergo a complete combustion reaction to obtain regenerated flue gas, regenerated contact agent, and ash. The ash is separated out by a separation device such as a cyclone separator.

[0057] In a preferred embodiment, the method further includes: at least a portion of the first dry gas and / or at least a portion of the second dry gas entering the regeneration unit, so that the recycled contactant and the charred ash undergo a complete combustion reaction in the presence of oxygen and dry gas to obtain regenerated flue gas and regenerated contactant, thereby supplementing the heat of the regeneration unit and improving resource utilization efficiency and contactant regeneration efficiency.

[0058] In one specific embodiment, when the regenerated flue gas meets the emission standard, the regenerated flue gas is discharged externally; wherein the emission standard for the regenerated flue gas is a conventional standard in the art, such as referring to the GB13271-2014 standard.

[0059] In one embodiment, in step S1, the waste plastic liquefaction unit uses a heated liquefaction conveying device to perform the liquefaction treatment; optionally, the heated liquefaction conveying device includes a first screw-type heated conveying device; preferably, the first screw-type heated conveying device is selected from a twin-screw or single-screw heated conveying device with heating.

[0060] In a preferred embodiment, the liquefaction process conditions include: an outlet temperature of 380–500°C, preferably 400–450°C; and a residence time of 5–30 min, preferably 5–15 min.

[0061] In one embodiment, in step S2, the waste plastic de-tackification unit uses a de-tackification reactor to perform the de-tackification cracking treatment; preferably, the de-tackification reactor is an adiabatic de-tackification reactor. In this disclosure, the adiabatic de-tackification reactor can be any reactor known in the art, such as an upflow de-tackification reactor or a downflow de-tackification reactor.

[0062] In a preferred embodiment, the process conditions for the viscosity-reducing cracking treatment include: a reaction temperature of 380–500°C, preferably 390–450°C, and more preferably 390–420°C; and a residence time of 10–90 min, preferably 20–70 min, and more preferably 30–70 min. The preferred viscosity-reducing cracking process conditions in this embodiment can achieve a better viscosity-reducing effect.

[0063] In one embodiment, in step S3, the process conditions for the cracking reaction include: a reaction temperature of 490–750°C, a bed linear velocity of 0.2–1.0 m / s; a mass ratio of high-temperature contact agent to liquefied and viscous-reduced waste plastic of 5–30:1; a mixing time of 0.1–2 s; and a mass ratio of contact agent to liquefied and viscous-reduced waste plastic in the contact cracking reactor of 8–40:1. In this disclosure, the cracking reaction is carried out in a fluidized bed reactor, which is a conventional structure in the art.

[0064] In a preferred embodiment, in step S3, the process conditions for the cracking reaction include: a reaction temperature of 500–650°C, a bed linear velocity of 0.4–0.8 m / s; a mass ratio of contact agent to liquefied and viscous waste plastic of 6–20:1; a mixing time of 0.1–2 s; and a mass ratio of contact agent to liquefied and viscous waste plastic in the contact cracking reactor of 12–30:1. Cracking under the process conditions of this embodiment yields a more favorable distribution of cracking products.

[0065] In a preferred embodiment, the method further includes: introducing the liquefied waste plastic oil from the viscosity-reducing cracking process and steam into the agent-oil mixing contact cracking reaction unit; preferably, the mass ratio of steam to plastic raw material is 0.05 to 1:1:1, more preferably 0.1 to 0.5:1.

[0066] In one embodiment, in step S3, the contact agent is one or more selected from silicon-aluminum catalyst, quartz sand, or coal coke powder; preferably, the particle size of the contact agent is 150-1000 μm; more preferably, it is 250-1000 μm.

[0067] Optionally, the silicon-aluminum material is selected from catalysts containing molecular sieves and / or catalysts without molecular sieves; preferably, the catalyst containing molecular sieves is selected from one or more of the following molecular sieves: X molecular sieve, Y molecular sieve, mordenite, ZSM-5, layered clay molecular sieve, SAPO, and spent FCC catalysts.

[0068] Preferably, the sieve-free catalyst is selected from catalysts prepared using one or more of the first raw materials, wherein the first raw materials include amorphous silica-alumina, kaolin, montmorillonite, palygorskite, illite, chlorite, boehmite, and silica; or

[0069] The catalyst without molecular sieves is selected from catalysts prepared using one or more of the second raw materials that have undergone acid washing, calcination, and sieving treatment as raw materials, wherein the second raw materials include amorphous silica-alumina, kaolin, montmorillonite, palygorskite, illite, and chlorite; or is selected from catalysts prepared using one or more of the second raw materials that have undergone acid washing, calcination, and sieving treatment as raw materials and pseudoboehmite and / or silica.

[0070] Optionally, the coal coke powder is coal powder and / or petroleum coke powder.

[0071] In one embodiment, the regeneration process is carried out in a dense-phase fluidized bed regenerator. Preferably, the process conditions for the regeneration process include: an air residence time of 0.5–60 seconds, more preferably 1.0–10 seconds; a vaporization temperature of 600–750°C, more preferably 600–700°C; an introduced gas containing 10–50% oxygen by volume; and a linear velocity of 0.05–0.6 m / s, more preferably 0.2–0.4 m / s. The dense-phase fluidized bed regenerator in this disclosure employs a device conventionally selected in the art.

[0072] In one embodiment, the hot melt dehydration and dechlorination unit of the waste plastic hot melt dehydration and dechlorination pulverizing unit includes a second screw-type heating and conveying device and a vacuum device connected to the second screw-type heating and conveying device; preferably, the second screw-type heating and conveying device is selected from twin-screw or single-screw conveying devices.

[0073] In a preferred embodiment, the process conditions for the melting and dehydration treatment include: a first temperature of 100–170°C, preferably 120–150°C; a time of 0.05–1 h, preferably 0.05–0.5 h; a feeding rate of chlorine-containing waste plastic raw materials of 5–5000 kg / h, preferably 100–4000 kg / h; and preferably, a heating rate of 30–200°C / min, preferably 50–100°C / min.

[0074] Preferably, the dechlorination process conditions include: a second temperature of 150–370°C, more preferably 220–350°C, and even more preferably 300–330°C; a time of 0.05–0.5 h, more preferably 0.1–0.2 h; a vacuum degree of 50–300 mmHg, more preferably 50–150 mmHg; and preferably, a heating rate from the first temperature to the second temperature of 50–200°C / min, more preferably 50–150°C / min. This disclosure employs a gradual heating method, first heating to the first temperature for melting and dehydration, and then heating to the second temperature for dechlorination, thereby improving the dehydration and dechlorination effect of waste plastics.

[0075] In one specific embodiment, the particle size of the dehydrated and dechlorinated waste plastic particles obtained by crushing is 0.5 to 10 mm.

[0076] In this disclosure, the apparatus and methods for cooling and pulverizing can be conventional apparatus and methods in the art.

[0077] The waste plastic cracking processing method provided by this invention overcomes the technical problems existing in the current field of waste plastic pyrolysis treatment. During the research process, the inventors discovered that one of the technical problems in the prior art is that polyvinyl chloride (PVC) in waste plastics, when heated and decomposed into HCl, can rapidly undergo an addition reaction with the double bonds in the raw materials to generate chlorinated hydrocarbons, making it difficult for traditional reaction devices to efficiently remove chlorine from the waste plastics. To address this technical problem, this invention uses specialized equipment to rapidly heat PVC-containing materials for decomposition and uses a vacuum method to quickly separate the decomposed HCl from the reactor, thereby improving dechlorination efficiency. The second technical problem overcome in the existing technology is that waste plastics are high-molecular polymers. Due to their large molecular weight and solid nature, heat transfer within the plastic is very slow. Traditional heating methods cause excessive cracking of the outer layer of the plastic while the interior remains solid, resulting in a high rate of coking and high gas yield during pyrolysis. To address this second problem, specialized equipment is used to rapidly heat the waste plastics into a flowable liquid state through strong extrusion and agitation to increase the heating area. This reduces the viscosity, allowing for pump delivery. A high-temperature contact agent is used as the heat source, which can handle the large heat demand of the waste plastic pyrolysis process. Furthermore, the larger particle size of the contact agent allows for oil-agent separation within the reactor, and the coked carbon and dry gas can serve as heat sources for pyrolysis. The third technical problem overcome is that waste plastics have a low density, resulting in a low rate of entry into the reaction device. Existing technologies have a small processing scale, which cannot meet the needs of modern large-scale recycling. To address this third problem, the method provided by this invention liquefies the waste plastics, significantly increasing the transport density of the raw materials compared to solid waste plastics. Therefore, it not only enables large-scale waste plastic processing but also allows for continuous pyrolysis and recycling of waste plastics.

[0078] Secondly, this disclosure provides a waste plastic cracking processing system, which includes: a waste plastic liquefaction unit, a waste plastic viscosity reduction unit, an agent-oil mixing contact cracking reaction unit, a separation unit, and a regeneration unit;

[0079] The waste plastic liquefaction unit includes a plastic raw material inlet and a liquefied waste plastic outlet. The waste plastic liquefaction unit is configured to liquefy plastic raw materials.

[0080] The waste plastic viscosity reduction unit includes a liquefied waste plastic inlet, a liquefied waste plastic oil outlet, and a first dry gas outlet. The waste plastic viscosity reduction unit is configured to perform viscosity reduction and cracking treatment on the liquefied waste plastic.

[0081] The contact cracking reaction unit includes a cracking feedstock inlet, a contact agent inlet, a reactor, a reaction oil and gas outlet, and a standby contact agent outlet; the cracking feedstock inlet is connected to the liquefied waste plastic oil outlet of the waste plastic viscosity reduction unit, and the contact cracking reaction unit is configured to perform cracking reaction treatment on the liquefied waste plastic oil;

[0082] The separation unit includes a separation inlet, a second dry gas inlet, a liquefied gas outlet, a gasoline fraction outlet, a diesel fraction outlet, and a wax oil fraction outlet; the separation inlet is connected to the reaction oil and gas outlet of the catalyst-oil mixing contact cracking reaction unit, and the separation unit is configured to separate the reaction oil and gas; the regeneration unit includes a pre-regenerated contact agent inlet, an oxygen-containing gas inlet, a regenerated contact agent outlet, and a regenerated flue gas outlet; the regeneration unit is configured to regenerate the pre-regenerated contact agent under oxygen-containing conditions to obtain regenerated contact agent and regenerated flue gas; the regenerated contact agent outlet is connected to the contact agent inlet of the catalyst-oil mixing contact cracking reaction unit.

[0083] In a preferred embodiment, the recycling unit further includes a dry gas inlet, which is connected to the first dry gas outlet of the waste plastic de-adhesion unit and / or the second dry gas outlet of the separation unit.

[0084] In one embodiment, the processing system further includes a waste plastic hot melt dehydration and dechlorination unit, a cooling and pulverizing unit, and a hydrogen chloride absorption unit;

[0085] The waste plastic hot melt dehydration and dechlorination unit includes a chlorine-containing waste plastic raw material inlet, a dehydrated and dechlorinated waste plastic outlet, and a hydrogen chloride gas outlet; the waste plastic hot melt dehydration and dechlorination unit is configured to perform melting dehydration and dechlorination treatment on chlorine-containing waste plastics;

[0086] The cooling and pulverizing unit is configured to cool and pulverize the dehydrated and dechlorinated waste plastics from the waste plastic hot melt dehydration and dechlorination unit;

[0087] The hydrogen chloride absorption unit includes a hydrogen chloride-containing gaseous material inlet and a hydrogen chloride absorbent; the hydrogen chloride-containing gaseous material inlet is connected to the hydrogen chloride-containing gas outlet of the waste plastic hot melt dehydration and dechlorination unit.

[0088] In one specific embodiment, the waste plastic liquefaction unit includes a heated liquefaction conveying device; optionally, the heated liquefaction conveying device includes a first screw-type heated conveying device; preferably, the first screw-type heated conveying device is selected from a twin-screw or single-screw heated conveying device with heating.

[0089] The waste plastic hot melt dehydration and dechlorination unit includes a second screw-type heating and conveying device and a vacuum device connected to the second screw-type heating and conveying device; preferably, the second screw-type heating and conveying device is selected from twin-screw or single-screw conveying devices.

[0090] In a preferred embodiment, the waste plastic hot melt dehydration and dechlorination unit and the waste plastic liquefaction unit adopt a heating liquefaction conveying device, including a first screw-type heating conveying device, and a gas outlet connected to a vacuum device is provided in the middle of the screw-type heating conveying device.

[0091] In one specific embodiment, the waste plastic hot melt dehydration and dechlorination pulverizing unit further includes a non-condensable steam outlet for drawing out non-condensable steam.

[0092] In one specific implementation, such as Figure 1 As shown, a waste plastic contact cracking processing system includes: a waste plastic liquefaction unit, a waste plastic viscosity reduction unit, an agent-oil mixing agent-oil mixing contact cracking reaction unit, a separation unit, a waste plastic hot melt dehydration and dechlorination unit, a cooling and pulverizing unit, a hydrogen chloride absorption unit, and a regeneration unit.

[0093] The waste plastic hot melt dehydration and dechlorination unit includes a chlorine-containing waste plastic raw material inlet, a dehydrated and dechlorinated waste plastic outlet, and a hydrogen chloride gas outlet; the waste plastic hot melt dehydration and dechlorination unit is configured to perform melting dehydration and dechlorination treatment on chlorine-containing waste plastics.

[0094] The cooling and pulverizing unit is configured to cool and pulverize the dehydrated and dechlorinated waste plastics from the waste plastic hot melt dehydration and dechlorination unit.

[0095] The waste plastic liquefaction unit includes a plastic raw material inlet and a liquefied waste plastic outlet. The waste plastic liquefaction unit is configured to liquefy plastic raw materials. The plastic raw materials can be dehydrated and dechlorinated waste plastic particles from the cooling and crushing unit or dehydrated and dechlorinated waste plastics from the waste plastic hot melt dehydration and dechlorination unit.

[0096] The waste plastic viscosity reduction unit includes a liquefied waste plastic inlet, a liquefied waste plastic oil outlet, and a first dry gas outlet. The waste plastic viscosity reduction unit is configured to perform viscosity reduction and cracking treatment on the liquefied waste plastic.

[0097] The contact cracking reaction unit for the agent-oil mixture includes a cracking feedstock inlet, a contact agent inlet, a reactor, a reaction oil and gas outlet, and a contact agent outlet. The cracking feedstock inlet is connected to the liquefied waste plastic oil outlet of the waste plastic viscosity reduction unit. The contact cracking reaction unit for the agent-oil mixture is configured to perform cracking reaction treatment on the liquefied waste plastic oil. The agent-oil mixer of the contact cracking unit also has a cracking feedstock inlet and a contact agent inlet, and the agent-oil mixture outlet is connected to the reactor.

[0098] The separation unit includes a separation inlet, a second dry gas inlet, a liquefied gas outlet, a gasoline fraction outlet, a diesel fraction outlet, and a wax oil fraction outlet; the separation inlet is connected to the reaction oil and gas outlet of the catalyst oil mixing contact cracking reaction unit, and the separation unit is configured to separate the reaction oil and gas.

[0099] The hydrogen chloride absorption unit includes a hydrogen chloride-containing gaseous material inlet and a hydrogen chloride absorbent; the hydrogen chloride-containing gaseous material inlet is connected to the hydrogen chloride-containing gas outlet of the waste plastic hot melt dehydration and dechlorination unit.

[0100] The regeneration unit includes a pre-regenerated contact agent inlet, an oxygen-containing gas inlet, a regenerator outlet, and a flue gas outlet; the pre-regenerated contact agent inlet is connected to the pre-regenerated contact agent outlet of the agent-oil mixing contact cracking reaction unit, and the regenerator outlet is connected to the contact agent inlet of the agent-oil mixing contact cracking reaction unit; preferably, the regeneration unit further includes a dry gas inlet, which is connected to the first dry gas outlet of the waste plastic de-adhesion unit and / or the second dry gas outlet of the separation unit.

[0101] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention, but the drawings and embodiments do not constitute a limitation of the present invention.

[0102] Figure 1 This is an exemplary flow chart of the processing method and system for contact cracking of waste plastics provided in this disclosure. Figure 1 As shown:

[0103] Plastic raw materials stored in raw material storage tank 1 enter plastic hot melt dehydration and dechlorination unit 2 for dehydration, deairing, and dechlorination, resulting in dehydrated and dechlorinated plastic and hydrogen chloride-containing gas. The hydrogen chloride-containing gas is then drawn into hydrogen chloride absorption unit 10 via a vacuum system to contact with the hydrogen chloride absorbent for absorption treatment. A small amount of non-condensable gas is discharged through pipeline 24. The dehydrated and dechlorinated plastic is then subjected to cooling and pulverization treatment in cooling and pulverizing unit 3 to obtain dehydrated and dechlorinated plastic particles. These particles enter plastic liquefaction unit 4 for liquefaction treatment, resulting in liquefied waste plastic. The liquefied plastic then enters plastic viscosity reduction unit 5 for viscosity reduction and cracking treatment, resulting in liquefied plastic oil and first dry gas. The viscosity-reduced liquefied plastic oil is then mixed with fresh contact agent replenished from pipelines 19 and 12, and high-temperature regenerated contact agent from regenerator pipeline 19 in a mixer. The mixture from step 6 is then sent to the dense phase fluidized bed reactor 7. A small amount of steam can enter the dense phase fluidized bed reactor 7 through pipe joint 14. The liquefied plastic oil undergoes a contact cracking reaction with the high-temperature contact agent to obtain reaction oil gas, carbonized ash, and recycled contact agent. The reaction oil gas enters the subsequent separation unit 9 through pipeline 13 for separation treatment. Among them, the second dry gas exits the unit from pipeline 23, and the liquefied gas, gasoline fraction, diesel fraction, and wax oil fraction exit the unit from pipeline 17. The recycled contact agent and carbonized ash enter the regeneration unit 8 through pipeline 15. The coke on the recycled contact agent, the cracked dry gas from pipeline 22, and the air from pipeline 20 undergo a complete combustion reaction. The generated regenerated flue gas exits the unit through pipeline 18. After meeting the standards, it can be directly discharged into the atmosphere. The obtained regenerated contact agent is led out of the regeneration unit 8 through pipeline 19, and the balancer and ash are discharged from pipeline 21.

[0104] The present disclosure is further described in detail below through examples. All raw materials used in the examples are commercially available.

[0105] The contact agent SL-1 used is a contact agent prepared by spray drying and calcination of 10% by weight alumina and 80% by weight kaolin. The specific preparation method is referenced in CN102974383A; the average particle size of SL-1 is 200μm.

[0106] The quartz sand used is designated as SL-2, with a particle size of 500μm.

[0107] The contact agent SL-3 used is a contact agent prepared by spray drying and calcination of 10% by weight alumina and 80% by weight kaolin. The specific preparation method is referenced in CN102974383A; the average particle size of SL-3 is 265μm.

[0108] In the following examples, the residual chlorine content in waste plastic raw materials and dechlorinated waste plastic liquid phase materials obtained from dechlorination treatment was tested using the fluorescence method (XRF).

[0109] The particle size of the contact agent was measured using a particle size analyzer.

[0110] The analytical methods for other elements in liquefied waste plastics are as follows: carbon and hydrogen (SH / T 0656-2017), oxygen (SH / T0986), nitrogen (SH / T 0704-2010), and sulfur (SH / T 0842-2010).

[0111] The distribution of cracking products was obtained by simulated distillation according to the NB / SH / T 0829-2010 method.

[0112] The analytical method for the viscosity of liquefied waste plastics is: SH / T 0739-2003.

[0113] The density analysis method for diesel and wax oil is SH / T0604-2000; the composition of cracked gases is determined by the RIPP 78-90 method; and the hydrocarbon composition of naphtha, diesel, etc., is determined by chromatographic analysis.

[0114] In the following embodiments, the particle size range of the particles obtained after pulverization is 5 to 8 mm.

[0115] The contact cracking reactors in the following examples and comparative examples are fluidized bed reactors.

[0116] Example 1

[0117] The plastic raw material was waste agricultural film with a chlorine content of 0.012% by weight and an ash content of 3.007%. The plastic raw material was fed into a twin-screw heated conveyor at a feed rate of approximately 5 kg / h. It underwent melting and dehydration treatment at a first temperature of 150°C for 0.1 h. Then, it underwent dechlorination treatment at a second temperature of 300°C for 0.1 h, with a heating rate of 100°C / min from the first temperature to the second temperature. The twin-screw heated conveyor was connected to a vacuum system with a vacuum level of 150 mmHg. The resulting dehydrated and dechlorinated plastic sample, DCl-1, has the properties shown in Table 1.

[0118] The same twin-screw heated conveyor was used to liquefy the dehydrated and dechlorinated plastics. The liquefaction process conditions are listed in Table 2. The residence time was 0.2 h, and liquefied plastics were obtained.

[0119] The liquefied plastic discharged from the outlet of the twin-screw heated conveyor enters the viscosity reduction reactor, where viscosity reduction is carried out at different temperatures and residence times to obtain liquefied plastic oil DCl-1 series samples. The internal temperature of the viscosity reduction reactor, the viscosity reduction reaction time, and the viscosity of the liquefied waste plastic are listed in Table 2. When the viscosity of the liquefied plastic oil is less than 2000 cP at 200℃, the liquefied plastic oil can be pumped to the mixer using a screw pump for rapid mixing with the contact agent and then transported to the cracking reactor.

[0120] Using DCl-1-2-60 as raw material and SL-1 as contact agent, liquefied plastic oil and high-temperature contact agent (temperature 640℃) were mixed in a mixer (temperature 560℃) and then fed into a dense phase fluidized bed reactor for contact cracking reaction to obtain reaction oil gas, carbonized ash, and unprocessed contact agent. The mass ratio of contact agent to plastic raw material was 12:1. The process conditions for cracking reaction included: reaction temperature 550℃, bed linear velocity 0.5m / s, and steam to plastic raw material mass ratio 0.1:1. The product distribution of cracking reaction products is shown in Table 3.

[0121] Table 1. Material properties of plastic raw materials after dehydration and dechlorination.

[0122]

[0123]

[0124] Table 2 Properties of plastic samples after viscosity reduction treatment

[0125] Liquefaction process outlet temperature 380 390 400 410 Temperature inside the viscosity reduction reactor / ℃ 380 390 396 404 (1) Viscosity reduction reaction time / min 40 40 40 20 Viscosity (cP at 200℃) - 2496.0 1400.0 825.6 (2) Viscosity reduction reaction time / min 60 60 60 40 Viscosity (cP at 200℃) 7043.0 587.2 351.6 181.6 (2) Viscosity reduction reaction time / / / 60 Viscosity (cP at 200℃) / / / 62.1

[0126] In Table 2, a "-" in the viscosity column indicates that the viscosity is too high to be tested.

[0127] As can be seen from Example 1, waste agricultural film plastic undergoes a melting, liquefaction, and dechlorination process using a twin-screw pump before entering a viscosity reduction process. After undergoing viscosity reduction reactions at different temperatures and times, its viscosity decreases significantly, meeting the requirements of the contact cracking process. Furthermore, Table 2 shows that when the liquefaction outlet temperature is 400–450°C and the viscosity reduction cracking reaction temperature is 390–450°C, the resulting liquefied waste plastic oil from the viscosity reduction cracking process has an even lower viscosity.

[0128] Comparative Example 1

[0129] Referring to the process flow of Example 1, the same plastic raw materials were used, but the difference from Example 1 was that dehydrated and dechlorinated plastic granules DCl-1 were used as raw materials. The same twin-screw heated conveyor was used for liquefaction treatment, with an outlet temperature of 390°C and a residence time of 0.2 hours, to obtain liquefied plastic. No viscosity-reducing cracking treatment was performed; the liquefied plastic was directly mixed with a high-temperature contact agent in a mixer, and then introduced into a contact cracking reactor. The contact cracking reaction process and conditions were the same as in Example 1, and the distribution of cracking reaction products is shown in Table 3.

[0130] Example 2

[0131] Using DCl-1-3-40 as raw material and SL-2 as contact agent, liquefied plastic oil and high-temperature contact agent (660℃) were mixed in a mixer and then introduced into a contact cracking reactor with steam. The mixture was then brought into contact with the fluidized contact agent to carry out a cracking reaction, yielding reaction oil gas and raw contact agent. The mass ratio of contact agent to plastic raw material was 12:1. The process conditions for the cracking reaction included: reaction temperature of 590℃, bed linear velocity of 0.4 m / s, and mass ratio of steam to plastic raw material of 0.4:1. The product distribution of the cracking reaction products is shown in Table 3.

[0132] Example 3

[0133] Using the plastic raw material from Example 1, the same process as in Example 1 was adopted, except that the raw material was not subjected to dehydration and dechlorination steps, but was directly liquefied and mixed with a high-temperature contact agent before entering the cracking reactor. The liquefaction conditions were an outlet temperature of 390°C and a residence time of 0.1 h. The recycled contact agent (containing 1.3% carbon by weight) obtained from the cracking reaction unit was introduced into the regeneration unit for regeneration treatment. The regeneration treatment was carried out in a dense phase fluidized bed regenerator. The process conditions for the regeneration treatment included: an air residence time of 3 s, a gasification temperature of 660°C in the dense phase bed, a gas containing 21% oxygen by volume, and a linear velocity of 0.1 m / s in the dense phase bed. The obtained recycled contactant was introduced into the cracking reaction unit together with the fresh contactant (the weight ratio of recycled contactant to fresh contactant was 20:1); and the first dry gas generated from the waste plastic de-viscosity reactor and the second dry gas obtained from the separation unit were introduced into the regenerator for continued use, and the agent to be recycled was completely burned (the amount of first dry gas and second dry gas introduced can be adjusted according to the actual recycling combustion situation). The cracking reaction temperature was 510°C, and other process conditions were the same as in Example 1. The product distribution of the cracking reaction products is shown in Table 3.

[0134] Example 4

[0135] Referring to the plastic raw materials and process flow in Example 1, the specific components include:

[0136] Plastic raw materials are fed into a twin-screw heated conveyor for dehydration and dechlorination. The twin-screw heated conveyor is connected to a vacuum device. The feeding rate is 100 kg / h. The raw materials are melted and dehydrated at a first temperature of 100°C for 0.5 h. They are then dechlorinated at a second temperature of 200°C for 0.05 h. The vacuum level is 150 mmHg. The heating rate from the first temperature to the second temperature is 50°C / min.

[0137] Another twin-screw heated conveyor was used to liquefy the dehydrated and dechlorinated plastic. The outlet temperature of the twin-screw heated conveyor was 410℃ and the residence time was 0.2h, resulting in liquefied plastic.

[0138] The liquefied plastic enters a viscosity reduction reactor at a temperature of 404°C and a residence time of 30 minutes to undergo viscosity reduction treatment, thereby obtaining liquefied plastic oil DCl-2.

[0139] Using liquefied plastic oil DCl-2 as raw material and SL-3 as contact agent, the liquefied plastic oil and high-temperature contact agent (660℃) are mixed in a mixer and then fed into a contact cracking reactor. Simultaneously, steam enters the contact cracking reactor and reacts with the fluidized contact agent to carry out a cracking reaction, yielding reaction oil gas and raw contact agent. The mass ratio of contact agent to plastic raw material is 12:1. The process conditions for the cracking reaction include: reaction temperature of 510℃, bed linear velocity of 0.5m / s, and steam to plastic raw material mass ratio of 0.1:1. The product distribution of the cracking reaction products is shown in Table 3.

[0140] Table 3

[0141]

[0142]

[0143] Example 5

[0144] The plastic raw materials are LDPE, HDPE, PS, PP and PVC mixed in a mass percentage of 4:4:8:3:1. The mixed plastic is crushed and dried. The chlorine content of the mixed plastic is 2.9% by weight. Due to the use of model compounds, the ash content is about 0%.

[0145] The melting, liquefaction, and dechlorination steps employed a twin-screw heated conveyor connected to a vacuum system. The feed rate was approximately 100 kg / h, and the vacuum level was 100 mmHg. During the experiment, the outlet temperature was varied, and the morphology and chlorine content of the plastic raw materials after conveying were tested under different outlet temperature conditions. A series of liquefied dechlorinated plastics, DCl-5-1 to DCl-5-7, were obtained. The chlorine content of the obtained liquefied dechlorinated plastics DCl-5-1 to DCl-5-8 is shown in Table 5.

[0146] A vacuum system is used to extract the gaseous material containing hydrogen chloride and send it into the hydrogen chloride absorption unit, where it comes into contact with the hydrogen chloride absorbent (NaOH solution) for hydrogen chloride absorption treatment.

[0147] Table 5 Properties of liquefied plastics in Example 5

[0148]

[0149]

[0150] As can be seen from the data in Table 5, when the dechlorination outlet temperature is 300-330℃ during the hot melt dechlorination process of waste plastics, the dechlorination rate of the liquefied dechlorinated waste plastics is higher.

[0151] Example 6

[0152] The liquefied dechlorinated plastic DCl-5-3 from Example 5, whose properties are shown in Table 6, was further heated to liquefaction using a screw-type heating and conveying device. Then, after holding at different temperatures for 30 min, 50 min, and 70 min, the rotational viscosity was measured (using an adiabatic upflow viscosity reduction reactor) to obtain viscosity-reduced cracked liquefied waste plastic oil (denoted as DCl-5-3-30, DCl-5-3-50, and DCl-5-3-70, respectively). The properties of the viscosity-reduced cracked liquefied plastic oil are shown in Table 7.

[0153] The liquefied dechlorinated plastic DCl-5-6 from Example 5 was heated to 250°C using a screw-type heating and conveying device and directly extruded into an atmospheric pressure container with an internal temperature of 250°C and a gas outlet. The container was kept at this temperature for 60 minutes. A sample of DCl-5-6-60 was taken to test its viscosity. The viscosity was too high and exceeded the measurement range. The sample was a plastic solid and could not flow on its own.

[0154] Table 6

[0155]

[0156]

[0157] Table 7 Viscosity of the viscosity-reducing plastic oil in Example 6

[0158]

[0159] In Table 6, a "-" in the viscosity column indicates that the viscosity is too high to be tested.

[0160] As can be seen from the data in Table 7, the viscosity reduction effect is better when the reaction temperature is 390-420℃ and the residence time is 30-70min.

[0161] Example 7

[0162] Using SL-2 as the contacting agent, the liquefied waste plastic oil DCl-5-3-70 from the viscosity-reducing cracking process in Example 6 was introduced into a mixer along with steam. The temperature of the high-temperature agent was 700°C, and the temperature after mixing was 630°C. The mixture was then introduced into a contact cracking reactor, where it was contacted with the fluidized contacting agent to carry out a cracking reaction, yielding reacted oil and gas and a reactive contacting agent. The mass ratio of the contacting agent to the waste plastic raw material was 12:1. The process conditions for the cracking reaction included: a reaction temperature of 630°C, a bed linear velocity of 0.45 m / s, and a mass ratio of steam to plastic raw material of 0.2:1. The product distribution of the cracking reaction products is shown in Table 8.

[0163] Example 8

[0164] Using SL-1 as the contacting agent, the liquefied waste plastic oil DCl-5-3-30 from the viscosity-reducing cracking process in Example 6 was introduced into a mixer along with steam. The temperature of the high-temperature agent was 660°C, and the temperature after mixing was 530°C. The mixture was then introduced into a contact cracking reactor, where it was contacted with the fluidized contacting agent to carry out a cracking reaction, yielding reacted oil and gas and a reactive contacting agent. The mass ratio of the contacting agent to the waste plastic raw material was 16:1. The process conditions for the cracking reaction included: a reaction temperature of 510°C, a bed linear velocity of 0.60 m / s, and a mass ratio of steam to plastic raw material of 0.3:1. The product distribution of the cracking reaction products is shown in Table 8.

[0165] Table 8

[0166]

[0167]

[0168] Waste agricultural film plastics are melted, liquefied, and dechlorinated using a twin-screw pump. Then, under conditions of 550°C, they undergo contact cracking reaction using SL-1 as a carrier. The resulting products are dry gas, liquefied petroleum gas (LPG), gasoline, diesel, wax oil, and coke. After ash removal, the material balance is calculated, showing a liquid yield of 82.17% by weight and a gasoline fraction yield of 53.03% by weight. Furthermore, using the waste plastics treatment process provided in this disclosure, Cl and Si are essentially removed from the liquid phase products of the waste plastics.

[0169] As can be seen from Comparative Example 1, the liquefied waste plastics that have not been deplasticized and reduced viscosity are mixed with a high-temperature contact agent before entering the cracking reactor. However, compared with Example 1, the liquefied waste plastics that have not been deplasticized and reduced viscosity have a high viscosity, which creates resistance to the contact and diffusion of the cracking reaction, thus increasing the yield of dry gas and coke.

[0170] As can be seen from Example 2, the liquefied waste agricultural film, using quartz sand (SL-2) as the heat carrier, undergoes a contact cracking reaction to produce dry gas, liquefied petroleum gas, gasoline, diesel, wax oil, and coke. After removing ash, the material balance is calculated, showing a liquid yield of 89.21% by weight and a gasoline fraction yield of 10.33% by weight. Furthermore, using the waste plastic treatment process provided in this disclosure, Cl and Si are essentially removed from the liquid phase products of the waste plastic.

[0171] As can be seen from Example 3, after the real plastic is melted, liquefied, and dechlorinated using a twin-screw pump, most of the chlorine in the waste plastic is removed. Under conditions of 510°C, using SL-1 as a carrier, after contact cracking reaction, the resulting products are dry gas, liquefied petroleum gas, gasoline, diesel, wax oil, and coke. After removing ash, the material balance is calculated, with a liquid yield of 84.92% by weight and a gasoline fraction yield of 53.61% by weight. Furthermore, using the waste plastic treatment process provided in this disclosure, Cl and Si are essentially removed from the liquid phase products of the waste plastic.

[0172] Comparing Example 1 and Example 4, it can be seen that the process parameters used in Example 1 are the preferred technical solution. In Example 4, the contact agent used has an average particle size of 265 μm. Under these process conditions, the contact agent bed is relatively high, which makes it easy for secondary reactions to occur. Therefore, the dry gas and coke are relatively high, and the contact agent is easily carried out of the reactor by the cracking reactants.

Claims

1. A processing method for contact cracking of waste plastics, characterized in that, The method includes the following steps: S1. Plastic raw materials enter the plastic liquefaction unit for liquefaction treatment to obtain liquefied plastic; the plastic liquefaction unit uses a heated conveying device for the liquefaction treatment; the heated conveying device includes a first screw-type heated conveying device; the process conditions for the liquefaction treatment include: outlet temperature of 380~500℃; residence time of 5~30min; S2. The liquefied plastic enters the plastic viscosity reduction unit for viscosity reduction cracking treatment to obtain viscous cracked liquefied plastic oil and first dry gas; the plastic viscosity reduction unit uses an adiabatic viscosity reduction reactor to carry out the viscosity reduction cracking treatment; the process conditions of the viscosity reduction cracking treatment include: reaction temperature of 380~500℃; residence time of 20~70min; S3. In the contact cracking reaction unit, the liquefied plastic oil and the high-temperature contact agent are mixed in a mixer. The mixture undergoes a cracking reaction in the contact cracking reactor to obtain reaction oil gas, recycled contact agent, and carbonized ash. The operating conditions of the mixer include: a mass ratio of contact agent to plastic raw material of 5~30:1; the operating conditions of the contact cracking reactor are: a mass ratio of contact agent to plastic raw material of 8~40:1; and a reaction temperature of 490~750℃. S4. The reaction oil and gas enter the separation unit for separation processing to obtain second dry gas, liquefied gas, gasoline fraction, diesel fraction and wax oil fraction; The recycled contact agent and charred ash enter the regeneration unit, react with oxygen to burn off the char and regenerate, yielding regenerated contact agent and regenerated flue gas; the regenerated contact agent is returned to the contact cracking reaction unit for continued use.

2. The processing method according to claim 1, characterized in that, Before step S1, the method further includes: Chlorine-containing plastic raw materials enter a hot melt dehydration and dechlorination unit. Under a first temperature condition, the chlorine-containing plastic raw materials are melted and dehydrated to obtain dehydrated plastic. Then, the dehydrated plastic is heated to a second temperature for dechlorination to obtain dehydrated and dechlorinated plastic and hydrogen chloride gas. The dehydrated and dechlorinated plastic is sequentially cooled and pulverized in a cooling and pulverizing unit to obtain dehydrated and dechlorinated plastic particles; these particles are then fed into a plastic liquefaction unit; or... The dehydrated and dechlorinated plastics are directly fed into the plastic liquefaction unit.

3. The processing method according to claim 2, characterized in that, The method also includes: The hydrogen chloride-containing gas is introduced into the hydrogen chloride absorption unit and comes into contact with the hydrogen chloride absorbent for hydrogen chloride absorption treatment; the hydrogen chloride absorbent is water or an alkaline solution with a pH greater than 7.

4. The processing method according to claim 1, characterized in that, In step S3, at least a portion of the first dry gas and / or at least a portion of the second dry gas enter the regeneration unit, so that the recycled contact agent and the charred ash undergo a complete combustion reaction in the presence of oxygen and dry gas to obtain regenerated flue gas and regenerated contact agent. Based on the total weight of the pre-existing contact agent, the carbon content of the pre-existing contact agent is 0.5~5.0% by weight.

5. The processing method according to any one of claims 1-4, characterized in that, The first screw-type heated conveying equipment is selected from a twin-screw or single-screw heated conveying equipment with heating; the process conditions for the liquefaction treatment include: an outlet temperature of 400~450℃; and a residence time of 5~15min.

6. The processing method according to any one of claims 1-4, characterized in that, In step S2, the process conditions for the viscosity reduction cracking treatment include: a reaction temperature of 390~450℃ and a residence time of 20~70min.

7. The processing method according to claim 6, characterized in that, In step S2, the process conditions for the viscosity reduction cracking treatment include: a reaction temperature of 390~420℃ and a residence time of 30~70min.

8. The processing method according to any one of claims 1-4, characterized in that, In step S3, the operating conditions of the mixer include: a mixing time of 0.1 to 2 seconds; The operating conditions of the contact cracking reactor are: bed linear velocity of 0.2~1.0 m / s; Steam is introduced into the dense phase fluidized bed reactor; the mass ratio of steam to plastic raw material is 0.01~0.5:

1.

9. The processing method according to claim 8, characterized in that, In step S3, the operating conditions of the mixer include: the mass ratio of contact agent to plastic raw material is 6~20:1; The operating conditions of the contact cracking reactor are as follows: the mass ratio of contact agent to plastic raw material is 12~30:1; the reaction temperature is 500~650℃; and the bed linear velocity is 0.4~0.8m / s. The mass ratio of steam to plastic raw materials is 0.01~0.3:

1.

10. The processing method according to any one of claims 1-4, characterized in that, In step S3, the contact agent is selected from one or more of silicon-aluminum materials, quartz sand, or coal coke powder; the particle size of the contact agent is 150~1000μm; The silicon-aluminum material is selected from catalysts containing molecular sieves and / or catalysts without molecular sieves; the molecular sieve is selected from one or more of X molecular sieve, Y molecular sieve, mordenite, ZSM-5, layered clay molecular sieve, and SAPO.

11. The processing method according to claim 10, characterized in that, In step S3, the catalyst without molecular sieves is selected from catalysts prepared using one or more of the first raw materials, wherein the first raw materials include amorphous silica-alumina, kaolin, montmorillonite, palygorskite, illite, chlorite, pseudoboehmite, and silica; or The catalyst without molecular sieves is selected from catalysts prepared using one or more of the second raw materials that have undergone acid washing, calcination, and sieving treatment as raw materials, wherein the second raw materials include amorphous silica-alumina, kaolin, montmorillonite, palygorskite, illite, and chlorite; or is selected from catalysts prepared using one or more of the second raw materials that have undergone acid washing, calcination, and sieving treatment as raw materials and pseudoboehmite and / or silica. The coal coke powder is coal powder and / or petroleum coke powder.

12. The processing method according to claim 4, characterized in that, The regeneration process is carried out in a dense phase fluidized bed regenerator. The process conditions for the regeneration process include: air residence time of 0.5 to 60 seconds, vaporization temperature of the dense phase bed of 600 to 750°C, gas with oxygen content of 10 to 50% by volume, and linear velocity of the dense phase bed of 0.05 to 0.6 m / s.

13. The processing method according to claim 12, characterized in that, The regeneration process conditions include: air residence time of 1.0 to 10 seconds, vaporization temperature of dense phase bed of 600 to 700℃, and linear velocity of dense phase bed of 0.2 to 0.4 m / s.

14. The processing method according to claim 2, characterized in that, The hot melt dehydration and dechlorination unit includes a second screw-type heating and conveying device and a vacuum device connected to the second screw-type heating and conveying device; The first temperature is 100~170℃; the residence time is 0.05~0.5h; the second temperature is 150~370℃; the residence time is 0.05~0.5h; and the vacuum degree is 50~300mmHg. The heating rate from the first temperature to the second temperature is 50~200℃ / min.

15. The processing method according to claim 14, characterized in that, The second screw-type heating conveyor is selected from twin-screw or single-screw heating conveyors.

16. The processing method according to claim 14 or 15, characterized in that, The first temperature is 120~150℃; the residence time is 0.05~0.5h; the second temperature is 220~350℃; the residence time is 0.1~0.2h; and the vacuum degree is 50~150mmHg. The heating rate from the first temperature to the second temperature is 50~150℃ / min.

17. The processing method according to claim 2, characterized in that, The dehydrated and dechlorinated plastic granules have a particle size of 0.5~10mm.

18. The processing method according to any one of claims 1-4, characterized in that, The plastic raw materials include one or more of LDPE, HDPE, PS, PP, PET and PVC; The chlorine content of the plastic raw material is less than 10% by weight; the ash content of the plastic raw material is 1-40% by weight.

19. A processing system for contact cracking of waste plastics, used in the processing method for contact cracking of waste plastics according to any one of claims 1-18, characterized in that, It includes a plastic liquefaction unit, a plastic viscosity reduction unit, a contact cracking reaction unit, a separation unit, and a regeneration unit connected in sequence; The plastic liquefaction unit includes a raw material inlet and a liquefied plastic outlet, and is configured to liquefy plastic raw materials; the plastic liquefaction unit includes a heating conveying device; the heating conveying device includes a first screw-type heating conveying device; The plastic viscosity reduction unit includes a liquefied plastic inlet, a liquefied plastic oil outlet, and a first dry gas outlet. The plastic viscosity reduction unit is configured to perform viscosity reduction cracking treatment on liquefied plastic. The plastic viscosity reduction unit adopts an adiabatic viscosity reduction reactor. The contact cracking reaction unit includes a mixer and a dense-phase fluidized bed reactor connected in series. The mixer is provided with a cracking feedstock inlet, a contact agent inlet, and an agent-oil mixture outlet. The dense-phase fluidized bed reactor is provided with an oil-agent mixture inlet, a reaction oil-gas outlet, and a awaited contact agent outlet. The cracking feedstock inlet is connected to the liquefied plastic oil outlet. The contact cracking reaction unit is configured to perform cracking reaction treatment on liquefied waste plastic oil. The separation unit includes a separation inlet, a second dry gas inlet, a liquefied gas outlet, a gasoline fraction outlet, a diesel fraction outlet, and a wax oil fraction outlet; the separation inlet is connected to the reaction oil and gas outlet of the contact cracking reaction unit, and the separation unit is configured to separate the reaction oil and gas. The regeneration unit includes a pre-regenerated contactant inlet, an oxygen-containing gas inlet, a regenerated contactant outlet, and a regenerated flue gas outlet; the regenerated contactant outlet is connected to the contactant inlet of the contact cracking reaction unit.

20. The processing system according to claim 19, characterized in that, The processing system also includes a plastic hot melt dehydration and dechlorination unit, a hydrogen chloride absorption unit, and a cooling and pulverizing unit; The plastic hot melt dehydration and dechlorination unit includes a raw material inlet, a dehydrated and dechlorinated plastic outlet, and a hydrogen chloride gas outlet; the plastic hot melt dehydration and dechlorination unit is configured to perform melting dehydration and dechlorination treatment on chlorinated plastics; The cooling and pulverizing unit is configured to cool and pulverize the dehydrated and dechlorinated plastic from the plastic hot melt dehydration and dechlorination unit. The hydrogen chloride absorption unit includes a hydrogen chloride-containing gas inlet and a hydrogen chloride absorbent; the hydrogen chloride-containing gas inlet is connected to the hydrogen chloride-containing gas outlet of the plastic hot melt dehydration and dechlorination unit; The regeneration unit further includes a dry gas inlet, which is connected to the first dry gas outlet of the plastic de-adhesion unit and / or the second dry gas outlet of the separation unit. The plastic hot melt dehydration and dechlorination unit includes a second screw-type heating and conveying device and a vacuum device connected to the second screw-type heating and conveying device.

Images