Waste pyrolysis process and apparatus

Abstract

Waste pyrolysis process and apparatus. An apparatus and process for producing monomers and petrochemical feedstocks from waste plastics to make plastics, using a reactor (7) having two reaction zones: a high temperature first reaction zone (9), and a second reaction zone (12) of lower temperature and longer residence time. The reactor (7) is provided with an injection nozzle (8) for injecting molten plastics into the first reaction zone (9); and a nozzle (11) for injecting a fluid into the second reaction zone (12) to reduce the temperature, and the second reaction zone (12) can have a larger cross-sectional area than the first reaction zone (9). Gaseous and vapour products are separated from the catalyst (20, 21) at the outlet of the reactor (7); the catalyst can be stripped and regenerated (23) before being returned to the reactor (7). The vapour products can then be condensed and purified.

Description

Technical Field

[0001] This invention relates to processes and equipment for converting waste plastics into petrochemical products and raw materials. Background Technology

[0002] Plastic production is projected to quadruple by 2050, increasing its share of global oil consumption from 6% in 2012 to 20% in 2050, and its share of carbon budgets from 1% in 2012 to 15% in 2050. If current plastic waste generation and recycling rates remain unchanged, the ratio of plastic waste to fish in the ocean will reach 1:1 by 2050.

[0003] It is estimated that only 9% of global plastic waste is effectively recycled each year. Existing recycling technologies (often referred to as mechanical recycling) cannot economically and efficiently recover high proportions of waste plastics. The main reason is that mechanical recycling requires excessive sorting of plastics by polymer type, color, and manufacturing method, while simultaneously ensuring the plastics are relatively clean and low in contamination. This results in plastic waste being separated into hundreds of separate categories, making high-proportion plastic recycling economically unfeasible. Chemical recycling, or advanced recycling, is a potential new technological solution capable of recovering mixed plastic waste that has only undergone light sorting, such as separating it into polyolefin (PO) and polystyrene (PS) streams, which account for more than 60% of plastic production. Plastic pyrolysis is a common chemical recycling method, a thermochemical decomposition process involving heating plastics under anaerobic conditions to produce liquid and gaseous hydrocarbons. PO and PS plastics consist only of carbon and hydrogen atoms. Theoretically, if PO and PS plastics are separated from other plastic types and used as pyrolysis feedstock, the product should contain only carbon and hydrogen. However, this is not the case, as plastic manufacturers add high concentrations of additives to plastics. These additives contain components such as halogens, silicon, phosphorus, nitrogen, sulfur, oxygen, and metal compounds, which degrade the quality of pyrolysis products. In recent years, plastic pyrolysis has attracted considerable attention as a potential method for recycling low-value PO films that are difficult to process mechanically. Advanced recycling, or chemical recycling, refers to using pyrolysis products as raw materials to manufacture new plastics, replacing feedstocks derived from fossil fuels. Using pyrolysis products in plastic manufacturing can significantly reduce carbon dioxide emissions. This emission reduction effect incentivizes the recycling of plastics currently landfilled or incinerated, such as films and other low-quality plastics. Major consumer brands have an increasing demand for food-grade recycled plastics, and chemically recycled plastics are an ideal source of food-grade recycled plastics. Despite several large-scale attempts at advanced recycling, numerous technical challenges have been encountered.

[0004] The core problem with existing technologies lies in the low quality of hydrocarbon products from typical waste plastic pyrolysis units, which contain high concentrations of contaminants, primarily halogens, silicon, phosphorus, olefins, dienes, nitrogen, oxygen, sulfur, and metal compounds. The main method for producing plastic monomers in the petrochemical industry is through steam cracking units, which decompose hydrocarbon feedstocks into plastic monomers at high temperatures. The design of steam cracking units and the high temperatures they operate at make them highly susceptible to corrosion by contaminants (even at extremely low concentrations) and also prone to coking. Therefore, steam cracking units have extremely stringent requirements regarding the concentration of contaminants in their feedstocks, as shown in the table below:

[0005] The oil produced from the pyrolysis of PO and PS plastics typically contains contaminants exceeding specified limits by an order of magnitude. More seriously, plastic pyrolysis oil contains contaminants rarely found in fossil fuels, such as metals, phosphorus, silicon, and halogens like chlorine. Metals in the feedstock of steam cracking units promote coking within the cracking furnace. Therefore, steam cracking feedstocks have extremely low tolerance for metal content, typically requiring a metal content limit of 1 ppm to avoid coking problems, while the metal content in plastic pyrolysis oil is usually between 100 ppm and 500 ppm. Furthermore, the hydrotreating catalysts used to refine plastic pyrolysis products are highly susceptible to metal contamination and damage, further exacerbating the problem.

[0006] Steam cracking of hydrocarbons to produce monomers is one of the most energy-intensive processes in the petrochemical industry. Adding the energy-intensive hydrogenation process for highly polluting plastic pyrolysis oil raises questions about whether advanced recycling is truly beneficial to the environment. Therefore, there is an urgent need in this field for a pyrolysis process that can directly convert waste plastics into short-chain monomers (such as light olefins like ethylene, propylene, and butene, as well as aromatics like benzene, toluene, and xylene (BTX),) thereby eliminating the energy-intensive hydrogenation and steam cracking steps. The process of directly converting waste plastics into plastic monomers is called monomer recycling.

[0007] Many plastic pyrolysis processes break down long plastic chains into shorter hydrocarbon molecules through thermal cracking. Catalytic cracking can significantly reduce the energy required for plastic pyrolysis while improving conversion rates and process efficiency. The main product of pyrolysis is high-boiling-point waxy gas oil, which is rarely processed by steam cracking units. Worse still, the higher the boiling point of the feedstock for steam cracking units, the higher the proportion of feedstock converted into low-value fuel products. Converting hydrocarbon products from plastic pyrolysis into fuel products does not fall under the category of recycling and cannot be included in the recycled content of the plastic produced by the process. There is a need in the art to develop a method to improve the conversion rate of heavy hydrocarbons from plastic pyrolysis into light, high-value hydrocarbons (including plastic monomers).

[0008] The introduction of cracking catalysts into refining units such as fluidized catalytic cracking (FCC) units is one of the most important advancements in refining history. The main advantages of using catalysts are: reduced reaction energy requirements, significantly increased conversion rates of heavy components to light, high-value components, and reduced generation of low-value products such as coke, methane, and hydrogen. The success of advanced recovery technologies hinges on fully utilizing the advantages of catalysts.

[0009] For a variety of reasons, the use of catalytic cracking of waste plastic streams has largely failed. First, the waste plastic streams contain high concentrations of catalyst poisons, leading to rapid catalyst deactivation. This forces a choice between two options: either use a low-activity catalyst, resulting in low conversion rates, or maintain a high catalyst replacement rate to preserve high activity, but this makes the process economically unfeasible. There is a need in the art to develop a method to reduce catalyst deactivation during waste plastic processing and, when catalyst deactivation is unavoidable, maintain high conversion rates and catalytic cracking levels.

[0010] Secondly, plastics differ significantly from the feedstocks commonly used in catalytic cracking units (such as FCC units). Plastic injection is extremely difficult, but proper injection is crucial for achieving optimal catalytic cracking performance. Uneven feedstock injection leads to uneven mixing of the catalyst and plastic, thereby significantly reducing catalyst effectiveness. There is a need in the art to develop a method to ensure adequate mixing between the catalyst and plastic in the reactor.

[0011] Unlike hydrocarbon oils, which vaporize without any molecular changes, plastics do not vaporize when heated. Instead, they break down into shorter hydrocarbon chains, which are gaseous at high temperatures. Incomplete vaporization leads to increased thermal cracking, particularly increased coke yield. To ensure rapid vaporization of the feedstock, temperatures need to be significantly increased. High temperatures in hydrocarbon catalytic cracking cause two main problems: they greatly increase the rate of catalyst deactivation, and coupled with high levels of catalyst poisoning, lead to high catalyst replacement rates; they also significantly increase thermal cracking reactions, producing undesirable products that negate the benefits of using a catalyst.

[0012] High-temperature conditions in catalytic reactors require high catalyst activity and short reactor residence times to minimize thermal reactions. However, maintaining high catalyst activity is impractical when processing waste plastics due to the extremely high concentrations of catalyst poisons. Low catalyst activity and short residence times result in low conversion rates, failing to produce lighter, more valuable products. Increasing residence time improves conversion rates, but high temperatures lead to significant thermal decomposition reactions. There is a need in the art to develop a method that, when processing plastic feedstocks containing high concentrations of catalyst poisons, simultaneously achieves the vaporization of the plastic feedstock and provides optimal conditions for catalytic decomposition.

[0013] The purpose of this invention is to provide an improved method and apparatus for pyrolysis of waste polymer materials (such as polyolefin plastic waste or polystyrene plastic waste) to overcome the above-mentioned defects of the prior art. Summary of the Invention

[0014] A first aspect of the invention provides an apparatus for producing monomers and petrochemical feedstocks from waste plastic streams. The apparatus includes a reactor containing a flowing particulate catalyst or particulate heat carrier, the reactor having two reaction zones: a first reaction zone operating at a high temperature and a second reaction zone operating at a lower temperature, the second reaction zone being sized such that the residence time in the second reaction zone is longer than that in the first reaction zone. A plastic injection device injects molten plastic into the first reaction zone; at least one fluid injection device injects fluid into the second reaction zone to lower the temperature.

[0015] In a preferred arrangement, the particulate catalyst or particulate heat carrier flows upward in the reactor pipe, entrained by a flowing gas or steam that does not inhibit the catalyst's action on the molten or vaporized plastic; a suitable gas or steam is water vapor. Therefore, this reactor pipe can be referred to as a riser.

[0016] A second aspect of the invention provides a process for producing monomers and petrochemical feedstocks from waste plastics. The process includes melting the waste plastics and injecting the molten plastics into a reactor containing a flowing particulate catalyst or particulate heat carrier. The reactor has at least two reaction zones: a first reaction zone at a high temperature and a second reaction zone at a lower temperature than the first reaction zone. The second reaction zone is sized such that the residence time in the second reaction zone is longer than that in the first reaction zone. The molten plastics are injected into the first reaction zone via a feeding device, whereby the particulate catalyst or particulate heat carrier heats and pyrolyzes the plastics. The process also includes injecting fluid into the second reaction zone to achieve a lower temperature.

[0017] The reactor may contain upward-flowing particulate catalyst or particulate heat carrier, which can be heated before entering the reactor to provide heat to the reactor. As mentioned above, the residence time in the second reaction zone is longer than that in the first reaction zone. For example, the residence time in the first reaction zone may be less than 10 seconds, and the residence time in the second reaction zone may be at least 1.1 times that of the first reaction zone; or it may be 1.5 to 2.0 times, or 2.0 to 4.0 times, that of the first reaction zone. The temperature in the first reaction zone may be between 450°C and 750°C, and the temperature in the second reaction zone may be between 350°C and 650°C.

[0018] Preferably, the particulate material is the catalyst, but in some applications, an inert material (such as sand) may be used instead. The following description focuses primarily on the use of catalysts, but it should be understood that in several places where catalysts are mentioned, depending on the materials being processed and the desired product, the catalyst may be replaced by an inert particulate material.

[0019] This invention applies to waste plastics that have been pretreated to remove contaminants such as dirt, paper, moisture, and other non-polyolefin (PO) or polystyrene (PS) plastics. The pretreated plastic is melted in an extruder, and after being melted and heated, the molten plastic is pumped to a reactor through a filter. The filter removes any solids that could clog the injection device, resulting in a smaller orifice in the feed device for easier spraying. The filtered molten polymer is pumped to the feed device, which uniformly sprays the plastic onto an upward-flowing hot catalyst stream. The plastic is fed into a first reaction zone, where the temperature is higher than the conventional temperature for catalytic cracking. The high reaction temperature ensures rapid vaporization of the plastic. If the plastic does not vaporize quickly, a large amount of pyrolysis occurs, leading to unnecessary reactions and increased coke formation. Due to the material handling characteristics of polymers, good contact between the polymer feedstock and catalyst particles is difficult to achieve, resulting in poor mixing and triggering excessive pyrolysis. This invention solves this problem by first vaporizing the feedstock at extremely high temperatures in the feed zone, as the plastic is more easily mixed with the catalyst once it is in a vapor state.

[0020] This invention employs a nozzle to inject another hot fluid downstream of the plastic feed unit (i.e., above the riser), thereby generating turbulence and ensuring enhanced rapid mixing between the catalyst and the vaporized plastic, providing optimal conditions for catalytic cracking. Liquid recycled products can be supplied to this nozzle, but this lowers the reaction temperature because energy is required to vaporize the liquid. Higher temperatures are needed for the initial cracking of the plastic; therefore, high-temperature steam is typically supplied to the nozzle to minimize or avoid temperature drops. Lighter products such as naphtha require higher temperatures to crack; therefore, these lighter products, instead of steam, can be supplied to the nozzle, and the temperature drop can be compensated for by increasing the catalyst-to-feed ratio.

[0021] High temperatures facilitate the vaporization of raw materials and initially break down plastics into shorter hydrocarbon chains. However, if the broken hydrocarbons are exposed to high temperatures for an extended period, a large amount of thermal decomposition will occur.

[0022] Initially, thermal cracking does not occur in the first reaction zone because the catalyst is fully regenerated and contains almost no coke, thus exhibiting high activity. When it comes into contact with the plastic raw material at high temperatures, catalytic cracking is initiated. However, after the initial cracking reaction, coke begins to deposit on the catalyst particles, causing temporary catalyst deactivation. If hydrocarbons come into contact with a less active catalyst, thermal cracking occurs, leading to an increase in the proportion of undesirable products. This invention solves this problem by cooling this area of ​​the reactor by recycling a portion of the reactor product back to the reactor and injecting it downstream of the initial high-temperature zone (i.e., above in the riser), thereby creating a lower-temperature second reaction zone. The reduced temperature significantly decreases the amount of thermal cracking reaction occurring.

[0023] The high contaminant content in the feedstock leads to lower temperatures and lower activity, resulting in poor conversion rates. Therefore, this invention provides a longer residence time in the second reaction zone, allowing sufficient time for the low-activity catalyst and lower temperature to convert hydrocarbons into more valuable products. This invention can increase the residence time by increasing the cross-sectional area of ​​the second reaction zone, thereby reducing the velocity within the reaction zone and extending the residence time; and / or by increasing the length of the riser in the second reaction zone. The residence time in the second reaction zone can be further increased by incorporating a bed pyrolysis section. This bed pyrolysis section comprises a large-volume reaction vessel in which a certain amount of catalyst is maintained in the dense phase, thereby allowing for a longer contact time between the catalyst and hydrocarbon vapors.

[0024] The difference between the reactor riser section and the bed pyrolysis section lies in the catalyst's position. In the riser, the catalyst is in a dilute phase, resulting in relatively little backmixing during flow. In the bed pyrolysis section, however, the catalyst is in a dense phase and exhibits a bubbling appearance. The bed pyrolysis section is achieved by introducing a mixture of gas, vapor, and catalyst particles from the riser into a chamber with a significantly larger cross-sectional area. This reduces the flow rate, preventing the catalyst particles from being entrained by the gas flow. The catalyst has a specific residence time in the bed pyrolysis section, controlled by the catalyst circulation rate, bed height, and the reactor volume. The bed height can be controlled using a slide valve or loop seal.

[0025] Bed cracking can lead to very high conversion rates, which may or may not be desirable for operators. Therefore, the riser section can terminate at a stop device inside the bed reactor; for bed cracking to occur, the catalyst level must be above the stop device, allowing hydrocarbon vapors to bubble through the dense bed of catalyst. If the catalyst level is below the stop device, bed cracking will not occur, which may depend on the desired product. (In this case, the second reaction zone consists only of the riser section above the coolant injection point.) If the catalyst level is above the stop device, the second reaction zone includes not only the riser section above the coolant injection point but also the flow portion within the catalyst bed; the higher the catalyst level, the higher the conversion rate and reaction intensity. This invention allows for changing the catalyst level, thereby altering the amount of bed cracking. This also allows operators to choose whether or not to perform bed cracking simply by controlling the height of the catalyst relative to the riser stop device.

[0026] If propylene and butene are the target products, a high conversion rate is required, necessitating extensive bed pyrolysis. Operators should ensure the bed level is above the riser termination device. If the target product is naphtha, excessive naphtha pyrolysis must be avoided, thus bed pyrolysis should be prevented. In this case, operators should ensure the bed level is below the riser termination device.

[0027] By modifying the catalyst in the reactor used in this invention, the flexibility of converting waste plastics into valuable components can be further improved.

[0028] Cracking catalysts typically consist of four components: zeolite, matrix, packing material, and binder. Zeolite is the most catalytically active component; commonly used zeolites in catalytic cracking are ultra-stable U.S.Y. (USY) zeolite and ZSM5 zeolite. ZSM5 additives are often used in combination with different catalysts to control the amount and activity level of ZSM5. The matrix is ​​another catalytically active component, usually composed of activated alumina, which has better resistance to metal contamination than zeolite. The most commonly used packing material is catalytically inert clay. The binder acts as a bond, holding the zeolite, matrix, and packing material together; in some cases, clay can also act as a binder. USY zeolite and ZSM5 are significantly more expensive than the other components and have much poorer resistance to contaminants such as halogens and metals.

[0029] Zeolites contain acidic sites, and their activity originates from these sites. These acidic sites can exchange with rare earth elements such as cerium and lanthanum to enhance their strength and activity. The rare earth content can be controlled; zeolites with extremely low or no rare earth content are classified as "low-rare-earth zeolites," while those with extremely high rare earth content are classified as "high-rare-earth zeolites." The introduction of rare earth elements can maintain more and denser acidic sites, thereby promoting hydrogen transfer reactions. Hydrogen transfer reactions convert alkenes into alkanes and aromatics.

[0030] By varying the catalyst and reaction parameters, the reactor can operate in three modes. The first mode is the naphtha maximization mode, with milder reaction conditions to prevent excessive cracking of naphtha into shorter molecules such as propylene and butene, thus avoiding bed cracking and prolonged residence time. In this mode, naphtha products are not recycled; only heavier gas oil products are recycled. The catalyst used in this mode has high matrix activity, promoting the cracking of long-chain hydrocarbons into naphtha components. The catalyst has balanced hydrogen transfer activity and matrix activity matching the high paraffinic naphtha yield. This catalyst contains no or only a very small amount of ZSM-5 additive (typically less than 10%) to prevent the cracking of naphtha components into short-chain olefins such as propylene. This catalyst will contain a zeolite catalyst, structurally designed to avoid hydrogen transfer reactions that generate aromatics, which are undesirable for naphtha sold as feedstock for steam cracking units. The catalyst used in this mode has an active matrix content of at least 10% to 60%, more preferably above 40%, a low-rare-earth USY-type zeolite content of 5% to 40%, and a ZSM5 additive content of less than 20%.

[0031] The second mode maximizes the production of propylene and butene. This is achieved by extending the residence time in the reactor and possibly combining it with bed cracking. In this mode, naphtha products can be recycled back to the reactor for cracking into propylene and butene. The catalyst used in the reactor is similar to that in the first mode, also exhibiting high matrix activity to promote the cracking of long hydrocarbon chains into naphtha components. However, it contains a higher concentration of ZSM-5 additive, typically exceeding 5% but less than 60%, and a much lower concentration of the same zeolite-type catalyst used in the first mode, designed to avoid hydrogen transfer reactions (since these reactions convert light olefins such as propylene into aromatic compounds, which should be avoided). Although the zeolite content is much lower than in the first mode, its presence helps to convert some medium-chain hydrocarbons into shorter hydrocarbons, making them the ideal length that the ZSM-5 additive can handle. The catalyst used in this mode consists of 5% to 40% low-rare-earth USY-type zeolite, 5% to 40% matrix, and 5% to 60% ZSM-5 additive.

[0032] The third mode is for the production of aromatic naphtha and light olefins such as propylene and butene. This mode utilizes a longer residence time (possibly combined with bed cracking) to increase the secondary reaction rates of aromatics and light olefins. The zeolite used in this catalyst is configured to allow for a large amount of hydrogen transfer reactions to generate aromatics. This zeolite has a high concentration of rare earth stabilizers to stabilize the basic catalyst and a high concentration of acidic sites in the Y-type molecular sieve. A high concentration of ZSM-5 additive dilutes the acidic site contribution of the basic catalyst containing rare earth USY-type zeolite, thereby reducing the formation of aromatics via the hydrogen transfer mechanism. The catalyst composition used in this mode is: 5% to 40% high rare earth USY-type zeolite, 5% to 30% matrix, and less than 20% ZSM5.

[0033] Light olefins such as propylene and butene can be separated, and naphtha can be separated into aromatic and non-aromatic compounds by solvent extraction or any other method known to those skilled in the art. This invention recycles low-value light hydrocarbon products (such as non-aromatic raffinate from solvent extraction) back to the reactor, converting them into more valuable components such as aromatics and light olefins. Lighter, shorter-chain hydrocarbon components are more difficult to crack than heavier, longer-chain hydrocarbon components. Shorter products require higher temperatures and higher catalyst-to-feed ratios; therefore, the first reaction zone provides ideal conditions for cracking naphtha. This invention can recycle shorter hydrocarbon products to the first reaction zone to improve the conversion rate of plastics into more valuable monomers such as aromatics and light olefins.

[0034] In all three modes, heavy products can be recycled to reduce the temperature in the second reaction zone. Catalyst poisons such as metals and phosphorus accumulate in heavy products, which typically hinders product recycling back to the reactor. This invention addresses this problem by employing a purification process on the heavy product, or any recycled product, that removes most of the catalyst poisons, preventing catalyst poisoning or deactivation during recycling back to the catalytic reactor.

[0035] Hydrocarbon vapors, catalyst, and coke exit the reactor and enter a cyclone separator, where the catalyst and coke are separated from the hydrocarbon vapors. The catalyst and coke then fall into a stripping tower, which removes hydrocarbons entrained in the catalyst. The stripped hydrocarbon vapors merge with the hydrocarbons from the cyclone separator and flow into a condensation system. The catalyst and coke then fall through a slide valve into a regenerator, where air is introduced to burn the coke, reheating and regenerating the catalyst. Coke typically cannot provide sufficient heat for the reaction, especially considering the high catalyst-to-feed ratio and the inclusion of the recirculated flow in the reactor's heat balance. This problem can be addressed by using fuel gas or a portion of the liquid product to heat the catalyst in the regenerator, thereby providing heat for the reaction.

[0036] Depending on the quality of the plastic feedstock and the extent of the pyrolysis reaction, the coke yield can be extremely high. Users of this invention may also choose not to recover hydrocarbon products and use a lower catalyst-to-feed ratio. In this case, heat needs to be removed from the regenerator. This invention may also include a catalyst cooler to cool the catalyst when necessary.

[0037] Hydrocarbon vapors flow into a condensation system, which separates the hydrocarbon products from the reactor into marketable products with specific boiling point ranges. Hot reactor vapors are fed directly to the bottom of a distillation column, or they can be quenched to reduce superheat before being fed into the column. The vapors enter the bottom of the column and come into contact with the heavier bottom product, which has undergone a cooling and purification process to remove contaminants from the heavier bottom product. This invention allows the purified bottom product to be recycled back to the distillation column to cool and condense the reactor vapors, thereby reducing the entry of contaminants such as metals into the lighter product. The distillation column separates the vapors into at least two products. The bottom product is sent to a purification process to remove all catalyst poisons, and then recycled back to the reactor for further cracking into lighter products.

[0038] The top product can be washed with water to cool and condense the naphtha product and remove several contaminants (such as salts, acids, and ammonia) that are typically enriched in lighter products. The resulting gas stream contains many valuable light olefins (such as ethylene, propylene, and butene), but is unsellable to the petrochemical industry due to numerous contaminants far exceeding petrochemical specifications. This invention addresses this problem by compressing the gas stream and subsequently sending it to a purification process that ensures the light olefin product meets petrochemical specifications. This purification process includes at least one of the following steps: amine washing, water washing, alkali washing, acid washing, dehydration, molecular sieving, activated carbon impregnation, and adsorption.

[0039] After purification, the purified gas stream is separated into a marketable component and a fuel gas component: the marketable component contains most of the valuable components in the gas stream (such as ethylene, propylene, butadiene, and butene); the fuel gas component contains lower-value components (such as methane and hydrogen). This invention separates the C2 to C4 components into marketable products and utilizes the fuel gas for process heating. This is because most difficult-to-remove contaminants (such as carbon dioxide, oxygen, and nitrogen) are enriched in the fuel gas stream. Other contaminants not enriched in the fuel gas are removed during the purification process. The end result is that this invention can produce monomeric products that meet petrochemical industry specifications.

[0040] This invention allows for the addition of catalysts to extruders, reactors, or regenerators. It allows the addition of at least two different types of catalysts at two different locations in the process. Typically, this invention employs three main types of catalysts: a base catalyst, a zeolite catalyst, and a ZSM5 catalyst. This provides great flexibility in catalyst configuration. The base catalyst is configured with a high matrix content because the matrix is ​​well-suited for cracking long hydrocarbon chains in plastic feedstocks. The matrix is ​​highly resistant to metal contamination, with most metal contaminants depositing on it. Compared to the base catalyst, zeolite and ZSM5 catalysts are more susceptible to metal contamination. Zeolite and ZSM5 catalysts can only handle shorter hydrocarbon chains, and if added to an extruder, they will be unable to crack the long hydrocarbon chains in plastic feedstocks. This invention adds a base catalyst to the extruder and the zeolite and ZSM5 catalysts to the regenerator or reactor. When the base catalyst is added to the extruder, it begins to crack the long hydrocarbon chains in the plastic feedstock, thereby reducing the workload of the extruder and consequently reducing its power consumption. The base catalyst added to the extruder also captures metal contaminants on the base catalyst, preventing the expensive zeolite and ZSM5 catalysts from being deactivated when added to the regenerator or reactor. Adding a catalyst to the extruder can also improve the mixing effect between the catalyst and the plastic. The temperature inside the extruder is low, so pyrolysis reactions occur very little. However, the presence of a catalyst in the extruder ensures that the plastic is rapidly pyrolyzed when it is added, thus reducing unwanted reactions. Another type of catalyst that can be used is used or non-fresh FCC catalyst, often referred to as a balanced catalyst or ECAT. The main advantage of ECAT is its significantly lower cost compared to fresh catalyst, allowing for higher replacement rates. ECAT can be used with fresh catalyst or additives such as ZSM5 to achieve the desired catalyst configuration and thus the desired product composition. In this case, ECAT can be added to the extruder, and fresh catalyst (such as, but not limited to, ZSM5 additive) can be added to the reactor or regenerator. Attached Figure Description

[0041] The waste plastic pyrolysis equipment according to embodiments of the present invention will be described below by way of example, with reference to the accompanying drawings.

[0042] Figure 1 This is a schematic diagram of advanced waste plastic recycling equipment.

[0043] Figure 2 yes Figure 1 A schematic diagram of the advanced recovery reactor of the device shown.

[0044] Figure 3 yes Figure 1 A schematic diagram of the gaseous product purification process of the device shown.

[0045] Figure 4 This is a schematic diagram of an advanced recovery reactor process for producing aromatic products.

[0046] Figure 5 This is a schematic diagram of a liquid product purification process. Detailed Implementation

[0047] The attached diagram illustrates an embodiment of a waste plastic pyrolysis system; the recycling reactor and related equipment are shown below. Figure 1 As shown.

[0048] Figure 1 The equipment shown is suitable for heating waste plastic raw materials to high temperatures under anaerobic conditions, decomposing long-chain polymers into shorter hydrocarbon chains, thereby producing a separable stream to produce products such as gas oil, naphtha, syngas, and carbonaceous solid materials called coke. The products are separated from each other after generation. The waste plastic raw material 1 preferably contains only polyolefin and polystyrene plastic types with minimal residue and moisture contamination. It is first processed to allow it to be fed to the extruder 2 in an easily manageable form (such as chips, granules, or flakes).

[0049] Extruder 2 is a twin-screw extruder suitable for multiple functions, its main function being to preheat the raw material to a temperature of approximately 250°C to 375°C under anaerobic conditions. Extruder 2 achieves heating by shearing the raw material through two counter-rotating screws inside, which directly transfer driving energy to the raw material.

[0050] The second function of extruder 2 is to reduce the viscosity of the plastic feedstock, which is crucial for subsequent feedstock injection. The final function of extruder 2 is to remove moisture and contaminants. Contaminated vapors are discharged through extruder vent 5 and then sent for treatment. A catalyst can be added to the extruder via port 3 or along with the plastic feedstock 1 via the feed throat, where the extruder mixes the plastic and catalyst. This catalyst has at least some matrix activity, and its structure is capable of breaking down long hydrocarbon chains in the plastic. Ideally, the plastic should be fed into the reactor when it begins to crack. The catalyst significantly reduces the energy required for the plastic feedstock to reach the critical point where it begins to crack. The mixed extruder of plastic and catalyst also allows sufficient contact time for the catalyst to capture most of the contaminants present in the feedstock. The catalyst added to the extruder is carefully selected to be highly resistant to any metallic contaminants in the plastic feedstock and to adsorb these contaminants onto the catalyst. Therefore, this contamination does not deactivate other catalysts added downstream to the reactor or regenerator; these other catalysts are typically more expensive and less resistant to contamination than the catalyst added to extruder 2.

[0051] The plastic feedstock, in a molten state, exits from extruder 2 with low viscosity and is pumped to filter 4 via the extruder or melt pump. The filter allows the plastic and catalyst to pass through while trapping any contaminants that could clog the plastic injection nozzle 8, which serves as the feed device for the molten plastic. Filter 4 allows for smaller orifices in the injection device, thus improving injection performance. The plastic and catalyst exit the filter and enter the plastic injection nozzle 8. The plastic injection nozzle 8 first draws the polymer into a fine stream and aligns the polymer stream at least partially with the direction of the catalyst flowing in reactor 7 to aid the reactor's hydrodynamics. The injection nozzle 8 also mixes the molten polymer with high-speed, high-pressure, and high-temperature steam. Therefore, nozzle 8 injects the polymer feed into reactor 7, which contains an upward-flowing thermal catalytic bed material and steam. Injecting the plastic feedstock exposes a large area of ​​the feed plastic, enabling good heat transfer with the heat-carrying catalyst, thereby effectively pyrolyzing the plastic feedstock 1. The main benefit of spraying plastic feedstock 1 is that it enables uniform mixing of feed particles and bed material particles, thereby avoiding local temperature gradients in the feed in reactor 7 and preventing molten plastic and catalyst bed material from agglomerating or accumulating.

[0052] Injection nozzle 8 delivers plastic into a region of reactor 7 where the temperature is higher than the rest of reactor 7; this region of reactor 7 is the first reaction zone 9. The high temperature of the first reaction zone 9 immediately vaporizes the polymer feedstock, further enhancing the contact between the fed plastic molecules and the active sites of the catalyst, reducing the number of adverse reactions caused by the feedstock's inability to vaporize immediately. Figure 2 As shown, the temperature of the first reaction zone 9 is controlled by a slide valve 10, which regulates the amount of catalyst supplied to the reactor 7 from the regenerator 23. The catalyst temperature from the regenerator 23 is between 400°C and 900°C. The reaction temperature of the first reaction zone 9 is related to the catalyst temperature, catalyst flow rate, and feed flow rate; it is typically in the range of 450°C to 750°C. The feed flow rate and catalyst temperature are usually kept stable, therefore the slide valve 10 is the only parameter controlling the reaction temperature of the first reaction zone 9.

[0053] Effective mixing between the catalyst bed material and the feed is crucial for maximizing the occurrence of catalytic cracking reactions. Even with high-performance feed systems, plastic is a difficult material to inject, leading to uneven mixing between the catalyst and the plastic. This invention addresses this problem by first vaporizing the plastic feedstock and then placing another nozzle 11 above the plastic injection nozzle 8; nozzle 11 injects gas or liquid into the reactor 7 to create turbulence, thereby further mixing the vaporized plastic feedstock with the catalyst. If the temperature of the fluid or gas introduced into the reactor 7 is lower than the temperature of the catalyst, the fluid or gas will have a cooling effect on the reactor 7, thereby lowering the reaction temperature.

[0054] One of the products of this pyrolysis process is a high-boiling-point hydrocarbon product, which is not ideal as a petrochemical feedstock but can be used in this nozzle 11. However, using a high-boiling-point hydrocarbon product as a fluid can significantly reduce the reaction temperature because the high-boiling-point hydrocarbon product must vaporize, which requires latent heat of vaporization and therefore a large amount of energy. The catalyst in the first reaction zone 9 has high activity because it has not yet been deactivated by coking. This results in a very high amount of catalytic cracking at the high reaction temperature of the first reaction zone 9, while the amount of thermal cracking is relatively low. Since high temperatures may be required subsequently, it is preferable to inject hot gas into this nozzle 11. This gas can be an inert gas, such as, but not limited to, nitrogen, or a gaseous product of this process, such as syngas, but water vapor is preferred. If steam is injected at a temperature lower than the internal temperature of reactor 7, the steam will lower the temperature of reactor 7, but the temperature drop will be less than when liquids such as gas oil are injected. In any case, the mixing nozzle 11 improves the mixing effect between the catalyst bed material and the feed plastic.

[0055] The high temperature and catalyst in the first reaction zone 9 initially cause the plastic to crack into shorter hydrocarbon chains. As the plastic cracks, coke begins to deposit on the catalyst, leading to catalyst deactivation. If the high temperature of the first reaction zone 9 is maintained after deactivation due to coking, a large amount of thermal cracking will occur. This invention solves this problem by introducing a coolant 15 into the reactor to lower the reaction temperature, thereby limiting the number of thermal cracking reactions. This forms a second reaction zone 12, with a temperature lower than the first reaction zone 9; typically, its temperature is between 350°C and 650°C, about 100°C lower than the first reaction zone. The temperature of the second reaction zone is measured by a temperature transmitter 13 and increased or decreased by controlling the flow rate of the coolant 15 to the reactor. The ideal coolant 15 is a high-boiling-point hydrocarbon product produced by the process. Recycling this product back to reactor 7 as a coolant has the additional benefit of allowing this low-value product to crack into shorter-chain, higher-value products.

[0056] Excessively high concentrations of catalyst poison in the feedstock make maintaining high catalyst activity economically impractical. Therefore, catalyst activity is typically kept at a low level. The combination of low catalyst activity and low reaction temperature in the second reaction zone 12 results in low conversion rates of long-chain hydrocarbons to more valuable short-chain hydrocarbon products. However, this invention addresses this problem by increasing the residence time of hydrocarbons in the second reaction zone 12. Even with a less active catalyst, a longer residence time can improve the conversion rate of hydrocarbons to the target product. The residence time in the second reaction zone 12 can be increased by increasing its cross-sectional area and / or its length. A bed cracking section can also be added to significantly increase the residence time in the second reaction zone 12.

[0057] The difference between reaction zones 9 and 12 (or "riser sections") and the bed pyrolysis section is that in the riser sections, the catalyst is in a dilute phase, and the backmixing during catalyst flow is relatively small. In the bed pyrolysis section, however, the catalyst is in a dense phase and exhibits a bubbling appearance. This is achieved by installing a reaction termination device 16 at the end of the riser section (i.e., the outlet of the second reaction zone 12), located inside the reaction vessel 17 with a large cross-sectional area. The catalyst has a certain residence time in the bed pyrolysis section, which is controlled by the bed level, measured by a level transmitter 18 and controlled by a slide valve 19.

[0058] Bed cracking can lead to very high conversion rates, which may not be desirable for operators. The termination device 16 is located within the reaction vessel 17. For bed cracking to occur, the catalyst level must be above the termination device 16 so that hydrocarbon vapors can bubble through the dense bed of catalyst. If the catalyst level is below the termination device 16, bed cracking will not occur, which may be desirable, depending on the target product. Higher catalyst concentrations result in higher conversion rates and greater reaction intensity. This invention allows operators to control the catalyst level relative to the riser termination device 16 via a level transmitter 18 and a slide valve 19, thereby selecting whether to initiate bed cracking.

[0059] Catalyst, coke, and hydrocarbon product vapors from plastic pyrolysis exit reactor 7 and flow into cyclone separator 20. Cyclone separator 20 separates the catalyst and coke from the hydrocarbon product vapors. The vapor stream exiting the top of cyclone separator 20 enters distillation column 22. (Cyclone separator 20 is arranged in parallel with the second cyclone separator 20.) Catalyst and coke fall from cyclone separator 20 into stripping column 21. Catalyst also falls from reaction vessel 17 into stripping column 21. Steam enters from the bottom of stripping column 21 and permeates through the catalyst. The steam desorbs any hydrocarbon products adsorbed on or within the catalyst and also releases any lingering hydrocarbon vapors entrained in solid particles accumulated at the bottom of stripping column 21. Steam exits from the top of stripping column 21 and enters the second cyclone separator 20. Catalyst and coke exit from the bottom of stripping column 21 and are discharged through slide valve 19, which maintains a barrier between reactor 7 and regenerator 23.

[0060] In the improved design, the cyclone separator 20 can be located inside the reaction vessel 17, above the bubbling fluidized bed. The stripping tower 21 can also be incorporated into the reaction vessel 17, located below the riser termination device 16.

[0061] Regenerator 23 introduces air to burn coke produced by plastic pyrolysis. The combustion of coke on the catalyst bed material causes the catalyst to be reheated. Exhaust gas exiting from the top of regenerator 23 enters cyclone separator 24, which separates any solid particles from the flue gas. Flue gas exiting from the top of cyclone separator 24 flows into a waste heat recovery system (not shown), which transfers heat from the flue gas to generate steam. The cooled flue gas flows into an emissions treatment system (not shown). The reheated catalyst bed material then exits from the bottom of regenerator 23 and re-enters the bottom of reactor 7. Slide valve 10 controls the catalyst flow rate between regenerator 23 and reactor 7 while maintaining a positive pressure differential to prevent catalyst backflow into regenerator 23.

[0062] To maintain the yield of high-value components, sustain high conversion rates, and avoid the generation of undesirable products such as methane and coke, a certain level of catalyst activity must be maintained. This activity can be maintained by adding fresh catalyst 3 to extruder 2 (added along with the plastic via the extruder feed throat) or separately via a side feeder. Fresh catalyst 27 can also be added to regenerator 23 while removing an equal amount of recycled catalyst. The added fresh catalyst has higher activity than the removed catalyst, resulting in increased catalyst activity. Typically, at least two different catalysts are added, one of which is a lower-value base catalyst, such as activated alumina or ECAT. In this invention, the lower-value base catalyst 3 is added to extruder 2. This catalyst is generally more resistant to fouling and adsorbs metallic contaminants, thus preventing the deactivation of the higher-value catalyst 27, which is typically a ZSM5 additive or a specific zeolite additive added to regenerator 23. The fact that most contaminants are adsorbed by the more durable and cheaper catalyst protects the more valuable catalyst, thereby significantly improving the economics of the process.

[0063] The type and composition of the catalyst have a significant impact on the product composition. This invention can be operated in three main modes to produce different products. The first mode maximizes the production of naphtha products. In this mode, naphtha products are not recycled. The catalyst used in this mode consists of: 5% to 40% low-rare-earth USY-type zeolite, 10% to 60% matrix, and less than 20% ZSM5.

[0064] The second mode maximizes the production of propylene and butene. This mode allows for the recycling of naphtha products, converting them into propylene and butene. The catalyst used in this mode consists of 5% to 40% low-rare-earth USY-type zeolite, 5% to 40% matrix, and 5% to 60% ZSM5 additive.

[0065] Another mode is to produce aromatic naphtha and light olefins such as propylene and butene. The catalyst used in this mode consists of 5% to 40% high rare earth USY type zeolite, 5% to 30% matrix, and ZSM5 at a concentration of less than 20%.

[0066] Whether heat needs to be added to or removed from the catalyst in regenerator 23 depends on several factors, such as the volume of recovered product, the catalyst-to-feed ratio, and the amount of pyrolysis reaction occurring. This invention allows the catalyst temperature in regenerator 23 to be controlled by feeding the syngas or fuel gas product produced by the process into regenerator 23 via nozzle 28 for combustion. This invention can also remove heat from the catalyst using catalyst cooler 29, to which boiler feedwater is supplied. The boiler feedwater can be fed into cooling pipes located within the refractory lining of regenerator 23. The catalyst temperature is measured by temperature transmitter 30 and catalyst temperature controller 31, which controls the catalyst temperature by controlling the flow rate of boiler feedwater to the catalyst cooler and controlling heater 28. This invention can also supply a portion of the low-value heavy hydrocarbon liquid product (or "oil") of this process: firstly in… Figure 5 In the liquid purification process shown, catalyst contaminants are removed from the oil, which is then fed into a nozzle located in regenerator 23, where it is burned to heat the catalyst. If the contaminants contain low-value heavy hydrocarbon liquid products, and these process products are not removed, the activity of the process catalyst will be severely compromised.

[0067] like Figure 1 As shown, distillation column 22 fractionates the steam exiting the reactor cyclone separator 20. Steam enters distillation column 22, where a large amount of steam is condensed and separated according to its boiling point. Distillation column 22 is filled with trays or packing to allow steam to permeate upwards through the reflux liquid.

[0068] like Figure 5As shown, the bottom gas oil product 99 enters the metal removal process, is filtered through filter 83 to remove particulate matter such as coke and bed feed fines, and then cooled to a temperature of 60 to 70°C by heat exchanger 84. It is then mixed with acid 85 (typically, but not limited to, phosphoric acid, phosphorus, citric acid, sulfuric acid, or malic acid, or combinations thereof) and thoroughly stirred in container 86 to ensure the acid is dispersed in the oil. The acid can increase the oxidation state of the metal, thereby increasing the solubility of the metal in water or other suitable solvents; the addition of acid can also increase the solubility of other contaminants in the solvent component. After flowing out of container 86, deionized water 87 is added to the stream. The gas oil, acid, and water then flow into container 88, where a residence time of approximately 30 to 45 minutes is allowed to allow impurities primarily containing metals, halogens, and phosphorus to come into contact with the water, ensuring effective dissolution of contaminant atoms, which helps remove contaminants from the bottom gas oil. To remove these contaminants, the mixture enters centrifuge 90, separating the gas oil product from the aqueous phase containing contaminants. The aqueous phase is discharged from outlet 91 and collected and treated for safe disposal (not shown). The gas oil exiting centrifuge 90 still contains some contaminants, so it is washed again with water for further purification; deionized water is added again at 92, and the liquid enters a second centrifuge 33. Impurities are removed at 34, and a portion of the purified gas oil is pumped to heat exchanger 35, where the gas oil temperature is adjusted to 100-110°C, followed by the injection of acid (e.g., but not limited to citric acid, phosphoric acid, phosphorus, or mixtures thereof) 36. The gas oil is then conveyed to container 38, where bleaching clay 37 is added, and the mixture is stirred for approximately 30 minutes while steam 42 is blown into container 38 to enhance the contaminant removal process. After flowing out from the bottom of bleaching container 38, the mixture is pumped to another bleaching container 41, where more bleaching clay is added under vacuum 39 to help remove water from the oil. After exiting the second bleaching container 41, the purified gas oil is filtered using filter 44 to remove waste bleaching soil, which is then sent for recycling or disposal 43.

[0069] The purified oil is then sent to ion exchange unit 25 for further removal of any contaminants.

[0070] Subsequently, a portion of the purified gas oil 15 is transferred to reactor 7 as a cooling medium in the second reaction zone 12 and subjected to further cracking, as this improves the yield of light, high-value components. Another portion is sent to regenerator 23 to heat the catalyst. A further portion of the purified gas oil 45 is pumped back to distillation column 22 to cool the product vapor at the bottom of column 22.

[0071] The purification of gas-oil streams 15 and 45 removes contaminants and catalyst poisons, making them highly practical and valuable. In existing technologies, a choice must be made between recovering low-value heavy products and using catalysts in pyrolysis reactors. This is because catalyst poisons (primarily metallic contaminants) accumulate in low-value heavy products. If this stream is recycled to the pyrolysis reactor, heavy hydrocarbons are broken down into lighter, more valuable products, but due to the extremely high boiling points of metallic impurities, they remain at the bottom of the reactor or distillation column. As metallic contaminants are continuously added to the reactor from the plastic feed, these contaminants accumulate in the process, significantly accelerating the deactivation of existing catalysts. This invention actively removes such contaminants, enabling the use of catalysts in the reactor and the recycling of low-value products, converting them into lighter, more valuable products. Pumping a portion of the purified oil 45 back to distillation column 22, at a position higher than the reactor steam inlet column, allows the purified oil to adsorb metallic contaminants from the hydrocarbon vapor, thus preventing these contaminants from entering lighter, more valuable products (such as naphtha)—products that must meet the stringent feedstock specifications of the petrochemical industry.

[0072] like Figure 5 As shown, the liquid purification unit can also process naphtha product stream 51, or it can be located elsewhere to process the liquid product off-site before it is fed into petrochemical or refining processes. It may be advantageous to locate the liquid purification process in a centralized facility so that liquid products from multiple plastic pyrolysis plants can be processed by the liquid purification process before further processing.

[0073] Uncondensed steam exiting from the top of distillation column 22 enters water washing column 46, where the naphtha fraction of the steam is condensed using cooling water. Water is used as a quenching fluid because certain contaminants (such as salts, acidic contaminants, and ammonia) concentrate at ambient temperature and are highly soluble in water. The condensed naphtha and steam exit from the bottom of water washing column 46 and enter two-phase separator 47, separating the water from the naphtha fraction. The large volume of aqueous phase exiting from the bottom of separator 47 is cooled in cooler 50 and then recycled to the top of water washing column 46. 49 parts of fresh water and neutralizing agent are added at the inlet to dilute and neutralize the circulating water. 48 parts of water are sent to a water treatment plant to maintain the liquid level. A portion of the naphtha product 51 can be sent to storage 51 or recycled back to reactor 7, while a portion of the naphtha fraction 70 is sent to adsorption column 69.

[0074] Uncondensed vapors exiting from the top of the washing tower 46 are further cooled to 0°C to 40°C by a top condenser 52, and then enter a separator 53 to help remove longer carbon chains and water. Uncondensed vapors exiting from the top of separator 53 are compressed to 6 to 20 bar (gauge pressure) by a compressor 54; this compression causes an increase in the temperature of the gas and fluid, thus requiring a cooler 55 to lower the temperature of the product stream. The vapor stream exiting cooler 55 enters another separator 56, and is then further compressed 57 to 30 to 85 bar (gauge pressure). After compression, the vapor stream's temperature increases, and it is subsequently cooled by a condenser 58 before entering a final separator 59. The condensate accumulates at the bottom of separators 53, 56, and 59 and flows into a two-phase separator 71, where water and hydrocarbon fractions are separated. The hydrocarbon fraction is sent to a downstream adsorption tower 68. The aqueous fraction is sent to a wastewater treatment plant (not shown in the figure).

[0075] like Figure 3 As shown, the gas purification system can be located at different points in the process flow; such as Figure 1 As shown, this system is used to process the gas stream from separator 59 or downstream of debutanizer 73. The condensate fraction of the syngas can also be pumped into the liquid system or into a gas purification system. Alternatively, such a purification system can be installed in a petrochemical facility to purify the gaseous product before it is fed into the petrochemical process (e.g., but not limited to a steam cracking unit).

[0076] A pressurized gas stream enters the alkaline scrubbing tower 60, where the pressurized vapor stream contacts an alkaline (sodium hydroxide) aqueous solution. The pressurized hydrocarbon vapor flows upward over the downward-flowing alkaline solution through the scrubbing tower packing to maximize the contact between the two fluid streams in scrubbing tower 60, thereby removing any residual contaminants such as unremoved CO2, H2S, and NO. x Alkaline scrubbing towers can be used in combination with or replace amine treatment units (not shown in the figure). Some contaminants (such as CO2 and H2S) are present in low concentrations and typically do not require amine treatment. Compared to water in a water scrubbing tower, the higher pressure increases the solubility of contaminants in water, therefore a water scrubbing tower can be used instead of the amine treatment unit 46.

[0077] The steam stream then exits from the top of the scrubbing tower 60 and enters a dehydration bed 62, which contains substances for removing moisture from the product steam stream, such as, but not limited to, molecular sieves. The dehydrated steam stream then flows into an adsorption bed 63, which removes contaminants from the steam stream, such as arsine, phosphine, chlorides, thiols, carbonyl sulfides, hydrogen sulfide, and ammonia. Adsorption bed 63 contains metal oxide adsorbents, such as, but not limited to, iron oxide, lead oxide, copper oxide, and zinc oxide. The resulting gas stream then enters an adsorption bed 64 containing activated carbon, which removes various contaminants such as mercury and halogens.

[0078] The gas then flows into a selective hydrogenation reactor 65, which can be configured to remove certain components from the gas stream, such as, but not limited to, propadiene, butadiene, acetylene, etc. The hydrogenation reactor requires hydrogen to operate; hydrogen is present in the gas stream, but its concentration may be insufficient, thus requiring additional hydrogen. A deoxygenation reactor (not shown) can also be added as needed to remove oxygen, nitrogen oxides, etc., but this may not be necessary as these contaminants are typically discharged from the fuel gas stream.

[0079] Figure 1 and Figure 3 The gas purification system shown only displays one of each of the adsorption beds 62, 63, and 64, but typically there are at least two identical adsorption beds of each type, arranged in parallel. During operation, contaminants are adsorbed onto the adsorbent material until the material's adsorption capacity is exhausted. At this point, the gas flow is redirected to the parallel standby bed, while a stripping fluid, typically steam or nitrogen, is introduced into the first bed to desorb and regenerate the bed.

[0080] The gas purification system includes at least one of the above-mentioned purification units, in any order. For example... Figure 3 As shown, the gas purification system can also be located at other points in the process flow for purifying gaseous products, such as the top product of the butane removal column stream 76. Figure 3 As shown, gas purification systems can also be performed off-site before the gaseous products are delivered to petrochemical or refining processes. It may be advantageous to centralize the gas purification process in a facility, allowing for the purification of gaseous products from multiple plastic pyrolysis plants before further processing.

[0081] Refer again Figure 1 The purified product vapor stream then flows into condenser 67, where it is cooled by the fuel gas stream. The cooled, pressurized vapor exiting condenser 67 flows to Joule-Thomson valve 61 or expansion turbine, thereby reducing pressure and cooling the resulting gas stream. The cooled gas flows to the bottom of adsorption tower 68, where it contacts the downward-flowing hydrocarbon component from container 71, which flows through a packing layer to maximize the contact area, further removing any product components with a carbon chain length of 2 or more, such as ethylene, propylene, propane, butene, butane, etc.

[0082] The uncondensed gas stream exiting the first adsorption tower 68 is fed into the second adsorption tower 69, where naphtha 70 (from separator 47) is used to adsorb any remaining ethylene and propylene. The naphtha and recovered lighter components are then returned to tower 22 as reflux using pump 72. The uncondensed pressurized gas exiting the top of the second adsorption tower 69 passes through a Joule-Thomson valve 66, which reduces the gas pressure and simultaneously cools the gas stream, then flows through a condenser 67 (cooling the gas stream exiting the gas purification system), and then as fuel supply to the heater 28 on the regenerator 23 to heat the catalyst bed feed.

[0083] The bottom outlet stream of the first adsorption tower 68 contains a mixture of light naphtha and components such as ethylene, propylene, propane, butane, and butene. This outlet stream is fed into a butane removal tower 73, which separates the C4 and lighter components from the heavier C5 and C6 components 78, the latter of which are discharged from the bottom of the tower and sent to storage.

[0084] The lighter components exit from the top of column 73, pass through condenser 75, and then enter reflux tank 74, where the liquid portion can be recycled to the top of column 73 to distill the upward-flowing lighter components. Products below C4 can be stored as pressurized gas or transported after liquefaction.

[0085] In the third mode, when the invention is configured to produce aromatic naphtha and light olefins such as propylene and butene, naphtha product 51 is sent to the aromatic separation process. For example... Figure 4 As shown, the naphtha product is sent to the aromatics separation process 79, where the aromatic components in the feedstock 80 are separated into aromatics product 82, which contains aromatic components such as benzene, toluene, and xylene, all of which are high-value products. The non-aromatic raffinate 81 produced by the separation process 79 contains almost no aromatic components and can be sold as a steam cracking feedstock.

[0086] This invention enables the conversion of lighter products (such as naphtha products generated during operation in the second mode (maximizing the yield of propylene and butene), or raffinate product 81 (as generated during operation in the third mode), and light naphtha stream 78 into valuable monomers, such as light olefins (including propylene and butene) and aromatics, by recycling light naphtha stream 78 back to reactor 7. Lighter products (such as naphtha products, streams 81 and 78) are more difficult to crack than heavier products (such as stream 15) because shorter hydrocarbon chains require more energy to crack, thus necessitating more stringent conditions, such as higher temperatures, higher catalyst activity, and longer residence times, to crack the feedstock molecules. This invention addresses this problem by recycling these products to a first reaction zone 9, which is sufficiently stringent to crack these light product streams.

[0087] For example, lighter products can be fed into multiple locations in the first reaction zone 9: the lighter product feed can be mixed with the plastic feed and enter through the plastic injection device 8; the lighter product can also be used as a fluid in the mixing injection device 11; or, the lighter product can be added below the plastic feed device 8 via the injection device 95, such as... Figure 2 As shown.

[0088] If the operator of this invention can accept a lower naphtha conversion rate, the naphtha can be supplied together with the heavier product stream 15 as a coolant. In this case, the operator can decide to increase the residence time of reactor 7 or introduce a bed pyrolysis section into reactor 7 to improve the conversion rate of the naphtha recirculation stream.

[0089] Therefore, it should be understood that several different aspects of the invention described herein can be summarized as follows: a) A two-zone reactor in which heavy hydrocarbon products are recycled back to the reactor above the plastic injection nozzle; b) A steam nozzle located above the plastic injection nozzle for mixing the vaporized plastic and catalyst; c) Recycle light hydrocarbon products such as naphtha back to the first reaction zone, which has a higher temperature; d) Figure 3 The gas purification process shown; e) Liquid purification processes shown in process units 83 to 44; f) Figure 4 The process and catalyst composition for producing aromatics shown (Model 3); g) Catalyst composition for light olefin production (Mode 2); h) Use syngas or purified hydrocarbon products as fuel to heat the catalyst in the regenerator; i) The cracking catalyst bed located at the outlet end of the riser; j) Two different types of catalysts are added to two different parts of the process.

[0090] Terms and conditions.

[0091] 1. A process for producing monomers and petrochemical feedstocks from waste plastics, comprising: melting waste plastics and injecting the molten plastics into a reactor containing a flowing catalyst, the reactor having at least two reaction zones: a first reaction zone at a high temperature and a second reaction zone at a lower temperature than the first reaction zone, the molten plastics being injected into the first reaction zone via a plastic injection device, the catalyst being heated and pyrolyzing the plastics, the process further comprising injecting fluid into the second reaction zone to achieve a lower temperature.

[0092] 2. As described in Clause 1, waste plastics are melted through an extruder.

[0093] 3. The process as described in Clause 1 or 2, wherein the reactor is arranged to provide a bubbling catalyst bed within or above the second reaction zone.

[0094] 4. The process as described in Clause 3 further includes adjusting the catalyst level in the bubbling catalyst bed.

[0095] 5. The process as described in any one of Clauses 1 to 4, wherein the fluid injected into the second reaction zone for cooling is the liquid hydrocarbon product of the process.

[0096] 6. The process as described in any one of Clauses 1 to 5 further includes separating the catalyst from the hydrocarbon vapor at the reactor outlet and regenerating the catalyst by burning the coke deposited on the catalyst for reuse in the reactor.

[0097] 7. The process as described in Clause 6 further includes using a fluid to remove hydrocarbons from the separated catalyst and then regenerating it.

[0098] 8. A process for pyrolyzing plastics using a flowing thermal catalyst to produce hydrocarbon products as described in Clause 1, comprising: (i) The plastic is melted and heated using an extruder; (ii) It causes the flow of the thermal catalyst within the reactor; (iii) Molten plastic is introduced into the reactor through an injection device, so that the plastic comes into contact with the catalyst, thereby heating and vaporizing the catalyst and causing the plastic to decompose; (iv) Injecting fluid into the reactor via at least one other injection device, at a height above the plastic injection device but below the second reaction zone, to induce mixing; (v) Separating the catalyst from the hydrocarbon; (vi) Stripping the separated catalyst from the hydrocarbon using stripping gas; (vii) The stripped catalyst is then transported to the regenerator; (viii) Air is supplied to the regenerator to burn the coke formed on the catalyst; (x) Return the regenerated catalyst to the reactor; (xi) Separate the hydrocarbon into liquid hydrocarbon products and gaseous hydrocarbon products.

[0099] 9. The process as described in Clause 5, wherein the liquid hydrocarbon contains at least 10% hydrocarbons with a boiling point above 100°C, preferably above 200°C.

[0100] 10. The process of any one of Clauses 1 to 9, wherein the second hydrocarbon product produced by the process is fed into the reactor upstream of the plastic feeder.

[0101] 11. The process as described in Clause 10, wherein the second hydrocarbon product contains at least 10% of a hydrocarbon composition with a boiling point below 400°C, preferably below 250°C.

[0102] 12. The process described in Clause 10 or 11, wherein the second hydrocarbon product is purified to remove contaminants such as metals, phosphorus and halogens before being fed into the reactor.

[0103] 13. The process as described in Clause 12, wherein the purification process includes at least one of the following steps: (i) Filtration to remove solids; (ii) Solvent washing; (iii) Pickling; (iv) Solvent washing; (v) Retaining pollutants on the adsorbent material; (vi) Remove the adsorbent material; (vii) Pickling and separation; (viii) Solvent washing and separation; (ix) Ion exchange resin.

[0104] 14. The process described in Clause 8, during operation, involves removing a portion of the catalyst from the equipment and introducing new catalyst into the extruder and / or regenerator.

[0105] 15. In the process described in Clause 14, the catalyst added to the extruder is different from the catalyst added to the regenerator.

[0106] 16. The process of any one of Clauses 1 to 15, wherein the process is used to produce a liquid hydrocarbon product, wherein the liquid hydrocarbon product is sent to a purification process comprising at least one of the following steps: (i) Filtration to remove solids; (ii) Solvent washing; (iii) Acid washing or alkali washing; (iv) Solvent washing; (v) Retaining pollutants on the adsorbent material; (vi) Remove the adsorbent material; (vii) Separation by acid washing or alkali washing; (viii) Washing and separation of adsorbent materials.

[0107] 17. The process of any one of Clauses 1 to 16, wherein the process is used to produce a gaseous hydrocarbon product, wherein the gaseous hydrocarbon product is sent to a purification process comprising at least one of the following steps: (i) Solvent washing; (ii) Alkali washing; (iii) Amine treatment; (iv) To retain pollutants on the adsorbent material; (v) Activated carbon adsorption; (vi) Adsorption of metal oxides; (vii) Hydrogenation treatment.

[0108] 18. The process of any one of Clauses 1 to 17, wherein the gaseous product or purified liquid hydrocarbon product of the process is combusted to heat the catalyst supplied to the reactor.

[0109] 19. The process of any one of Clauses 1 to 18, wherein the catalyst comprises 5% to 40% of low rare earth USY type zeolite, 5% to 40% of matrix and 5% to 60% of ZSM5 additive.

[0110] 20. The process of any one of Clauses 1 to 19, wherein the catalyst comprises 5% to 40% high rare earth USY type zeolite, 5% to 30% matrix and ZSM5 at a concentration of less than 20%.

[0111] 21. The process of any one of Clauses 1 to 19, wherein the catalyst comprises 5% to 40% of low rare earth USY type zeolite, 10% to 60% of matrix and ZSM5 at a concentration of less than 20%.

[0112] 22. A process for catalytically pyrolyzing plastic raw materials, comprising: (a) In the presence of a cracking catalyst, plastic is fed into a pyrolysis reactor to generate a hydrocarbon stream; (b) Separating the hydrocarbon stream into at least two hydrocarbon streams, wherein at least one hydrocarbon stream is a liquid hydrocarbon stream; (c) Treating the liquid hydrocarbon stream to remove contaminants by at least one of the following steps: (i) Treating liquid hydrocarbon streams with inorganic or organic acids or combinations thereof; (ii) Wash with solvent, then separate the liquid hydrocarbon stream from the solvent component containing the contaminant. (iii) Contacting the liquid hydrocarbon stream with solid particles of the adsorbent material, and then separating the solid particles from the liquid hydrocarbon stream; and / or (iv) To bring the liquid hydrocarbon stream into contact with the ion exchange material; and (d) The purified liquid hydrocarbon stream is sent back to the pyrolysis reactor for further cracking into shorter hydrocarbon chains.

Claims

1. An apparatus for producing monomers and petrochemical feedstocks from waste plastics, comprising: Reactors containing flowing particulate catalysts or particulate heat transfer materials The reactor has at least two reaction zones: a first reaction zone adapted to operate at a high temperature, and a second reaction zone adapted to operate at a temperature lower than that of the first reaction zone, and its size is such that the residence time in the second reaction zone is longer than that in the first reaction zone; The reactor includes a plastic injection device for injecting molten plastic into the first reaction zone, and at least one fluid injection device for injecting fluid into the second reaction zone to reduce the temperature.

2. The apparatus of claim 1, further comprising at least one additional fluid injection device located downstream of the plastic injection device for injecting fluid into the first reaction zone to generate turbulence.

3. The apparatus as claimed in any of the preceding claims, comprising an extruder to produce molten plastic supplied to the molten plastic injection device.

4. The apparatus as claimed in any of the preceding claims, arranged to provide a bubbling fluidized bed, said bubbling fluidized bed being incorporated into or located downstream of the second reaction zone.

5. The apparatus of claim 4 further includes a device for adjusting the level of the particulate catalyst or particulate heat transfer material in the bubbling fluidized bed.

6. The apparatus as claimed in any of the preceding claims, comprising a separation device for separating hydrocarbon vapor from the catalyst at the outlet of the reactor, and a device for regenerating the particulate catalyst or particulate heat transfer material for reuse in the reactor.

7. The apparatus of claim 6, wherein the separation device comprises at least one cyclone separator and a steam stripper.

8. A process for producing monomers and petrochemical feedstocks from waste plastics, the process using an apparatus comprising a reactor, comprising: The waste plastic is melted and injected into a reactor containing a flowing particulate catalyst or particulate heat transfer material. The reactor has at least two reaction zones: a first reaction zone with a high temperature and a second reaction zone with a lower temperature than the first reaction zone. The second reaction zone is sized such that the residence time in the second reaction zone is longer than that in the first reaction zone. The molten plastic is injected into the first reaction zone through a plastic injection device, whereby the particulate catalyst or particulate heat carrier heats and pyrolyzes the plastic. The process also includes injecting fluid into the second reaction zone to achieve a lower temperature.

9. The process of claim 8, wherein the waste plastic is melted by an extruder.

10. The process of claim 8 or 9, wherein the reactor is arranged to provide a bubbling fluidized bed, the bubbling fluidized bed being incorporated into or located downstream of the second reaction zone.

11. The process of claim 10 further includes adjusting the level of the particulate catalyst or particulate heat transfer material in the bubbling fluidized bed.

12. The process of any one of claims 8 to 11, wherein the fluid injected into the second reaction zone for cooling is the liquid hydrocarbon product of the process.

13. The process of claim 12, wherein the liquid hydrocarbon contains at least 10% hydrocarbons with a boiling point above 100°C and preferably above 250°C.

14. The process of any one of claims 8 to 13 further comprises separating the particulate catalyst or particulate heat transfer material from the hydrocarbon vapor at the outlet of the reactor, and regenerating the separated particulate material by burning coke deposited on the separated particulate material for reuse in the reactor.

15. The process of claim 14 further includes using a fluid to remove hydrocarbons from the separated particulate material and then regenerating it.

16. The process of any one of claims 8 to 15, further comprising introducing fluid into the reactor downstream of the plastic injection device and upstream of the second reaction zone via at least one other injection device, thereby generating turbulence.

17. The process of any one of claims 8 to 16, wherein the second hydrocarbon product produced by the process is fed into the reactor upstream of the plastic injection device.

18. The process of claim 17, wherein the second hydrocarbon product contains at least 10% hydrocarbons with a boiling point below 200°C, preferably below 100°C.

19. The process of claim 17 or 18, wherein the second hydrocarbon product is purified to remove contaminants such as metals, phosphorus, and halogens before being fed into the reactor.

20. The process of claim 19, wherein the purification process comprises at least one of the following steps: (i) Filtration to remove solids; (ii) Solvent washing; (iii) Acid or alkali washing, followed by water washing; (iv) The pollutants are trapped on the adsorbent material, and then the adsorbent material is removed; (v) Acid or alkali treatment, followed by washing with water.

21. The process of any one of claims 8 to 20, wherein during operation, a portion of the catalyst is removed from the equipment and new catalyst is introduced into the extruder and / or regenerator.

22. The process of claim 21, wherein the catalyst added to the extruder is different from the catalyst added to the regenerator.

23. The process of any one of claims 8 to 22, wherein the process produces a liquid hydrocarbon product, and wherein the liquid hydrocarbon product is sent to a purification process, the purification process comprising at least one of the following steps: (i) Filtration to remove solids; (ii) Solvent washing; (iii) Acid or alkali washing, followed by water washing; (iv) The pollutants are trapped on the adsorbent material and then the adsorbent material is removed.

24. The process of any one of claims 8 to 23, wherein the process is used to produce a gaseous hydrocarbon product, wherein the gaseous hydrocarbon product is sent to a purification process, the purification process comprising at least one of the following steps: (i) Solvent washing; (ii) Alkali washing; (iii) Amine treatment; (iv) To retain pollutants on the adsorbent material; (v) Activated carbon adsorption; (vi) Adsorption of metal oxides; (vii) Hydrogenation treatment.

25. The process of any one of claims 8 to 24, wherein the gaseous product of the process is combusted to heat the particulate catalyst or particulate heat transfer material supplied to the reactor.

26. The process according to any one of claims 8 to 25, wherein the particulate material is a catalyst having the following composition: 5% to 40% low rare earth USY type zeolite, 5% to 40% matrix and 5% to 60% ZSM5 additive.

27. The process according to any one of claims 8 to 26, wherein the particulate material is a catalyst having the following composition: 5% to 40% high rare earth USY type zeolite, 5% to 30% matrix and ZSM5 at a concentration of less than 20%.

28. The process according to any one of claims 8 to 26, wherein the particulate material is a catalyst having the following composition: 5% to 40% low rare earth USY type zeolite, 10% to 60% matrix and ZSM5 at a concentration of less than 20%.

29. A process for catalytically pyrolyzing plastic raw materials, comprising: (a) In the presence of a cracking catalyst, plastic is fed into a pyrolysis reactor to generate a hydrocarbon stream; (b) Separating the hydrocarbon stream into at least two hydrocarbon streams, wherein at least one hydrocarbon stream is a liquid hydrocarbon stream; (c) Treating the liquid hydrocarbon stream to remove contaminants by at least one of the following steps: (i) Treating liquid hydrocarbon streams with inorganic or organic acids or combinations thereof; (ii) Wash with solvent, then separate the liquid hydrocarbon stream from the solvent component containing the contaminant. (iii) Contacting the liquid hydrocarbon stream with solid particles of the adsorbent material, and then separating the solid particles from the liquid hydrocarbon stream; and / or (iv) To bring the liquid hydrocarbon stream into contact with the ion exchange material; and (d) The purified liquid hydrocarbon stream is returned to the pyrolysis reactor for further cracking into shorter hydrocarbon chains.

30. An apparatus for performing the process as described in claim 29.

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