MXPA99000648A - Partial oxidation of desec plastic material - Google Patents

Abstract

An integrated liquefaction and gasification process converts plastic materials from halogen-containing waste with bulk particles, with a minimum particle size reduction, into an environmentally toxic, non-leachable, non-toxic, non-toxic synthesis and slag gas. The process involves the melting and disintegration of the halogen-containing waste plastic material with bulk particles to form a low molecular weight, low boiling, halogen-containing oil composition, which is subsequently subjected to partial oxidation in a cooling gasifier. to produce a synthesis gas. Any gas, liquid or hazardous solid produced can be purified into commercially valuable by-products or recycled in the process, which does not release hazardous materials into the environment.

Description

PARTIAL OXIDATION OF PLASTIC WASTE MATERIAL This application claims the benefit of the Provisional Requests of the U.S.A. Nos. 60 / 021,878; 60; 021,879; and 60 / 021,885, all filed July 17, 1996. BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an environmentally safe process for converting waste plastic materials into valuable gas products and environmentally non-toxic slag, and more particularly to a process of liquefaction and gasification integrated with a minimum liquid discharge to convert waste plastic materials containing halogen in bulk into a liquid hydrocarbon feedstock that can be used in a partial oxidation reactor to produce a synthesis gas that is mainly carbon monoxide and hydrogen, and non-toxic slag ambiently, not leachable. 2. Description of the Prior Art Waste plastic materials, especially plastic waste materials containing halogen, and in particular those with a high chloride content, present particularly difficult disposal problems, since these materials are subject to restrictions increasingly stringent against emptying or disposal in public landfills. The burning of plastic waste materials is feasible only if it is carried out in accordance with strict environmental restrictions against the atmospheric elimination of gases containing chloride and byproducts with toxic particles. Canadian Patent Application Number 2,130,019 to Gerhardus et al., Refers to a process for thermally breaking plastic waste materials that are subsequently subjected to partial oxidation to produce synthesis gas. However, it is necessary to thaw the plastic waste materials before partial oxidation because severe corrosion problems can occur without dehalogenation when vapors containing halide and accompanying the synthesis gas products are cooled and condensed. The halide vapors mainly in the form of hydrogen chloride are condensed from the gas degradation products that occur during the liquefaction of the waste plastic materials. Dehalogenation, especially dechlorination prior to partial oxidation is a major problem because the Canadian patent is based on the radiant cooling of the gasification products of partial oxidation. Therefore, the presence of halide or hydrogen chloride vapors would present severe corrosion problems in the equipment used in the Canadian patent process. German Patent Application DE 441236A1 to Rabe et al., Presents a process for the recycling of mixed and contaminated waste plastic materials in a gasification reaction to produce carbon monoxide and hydrogen. The German process uses the steps of liquefaction and gasification, but does not address the problem to be dealt with plastic waste materials that contain halogen. As used herein, a partial oxidation reactor may also be referred to as a "partial oxidation gasifier", or simply as a "gasifier" and these terms are often used similarly and interchangeably. The partial oxidation reactors which are used in this invention are also commonly referred to as "cooling gasifiers". The reaction temperatures for partial oxidation usually range from about 900 ° C to about 2,000 ° C, preferably from about 1,200 ° C to about 1,600 ° C. The pressures generally range from about 1 to about 250 atmospheres, preferably from about 5 to about 200 atmospheres, and more preferably from about 20 to about 80 atmospheres. Partial oxidation reactors are shown in U.S. Patent Number 4, 823,741 to Davis et al., U.S. Patent No. 4,889,540 to Segerstrom et al., U.S. Patent Nos. 4,959,080 and 4,979,964, both to Sternling, U.S. Patent No. 5,281,243 to Leininger, and the United States Numbers 5,554,202 and 5,545,238 both for Brooker et al. SUMMARY OF THE INVENTION The present invention relates to an integrated liquefaction and gasification process for converting halogen-containing waste plastic materials into bulk particles with a minimum particle size reduction within an environmentally friendly non-toxic synthesis and slag gas, vitrea, not leachable. The process involves melting and breaking the bulk plastic material containing halogen into bulk particles to form a halogen-containing oil composition with lower molecular weight and lower boiling point, which is subjected to partial oxidation in a cooling gasifier. to produce a synthesis gas. Any dangerous gas, liquid or solid produced can be purified within commercially valuable by-products or can be recycled in the process, which does not release hazardous materials into the environment. BRIEF DESCRIPTION OF THE ILLUSTRATION The appended illustration is a simplified diagrammatic representation of the stages of liquefaction and partial oxidation of the process. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is an environmentally safe and improved liquefaction process for converting waste plastic materials with a high or variable halogen content into a hydrocarbon feedstock for a partial oxidation reaction in a gasifier. cooling in order to produce a synthesis gas or "syngas" which is mainly formed by carbon monoxide and hydrogen. An important advantage of the liquefaction process is that it can convert bulk plastic material with a high halogen content, into a thermally disintegrated oil with a minimum amount of particle size reduction, or halogen elimination before liquefaction. The disintegrated oil that is produced from the waste plastic material during liquefaction serves as the main source of the hydrocarbon reagent in the partial oxidation reaction to produce the synthesis gas. The liquefaction products include a thermally disintegrated oil that does not vaporize at the melting and breaking temperatures during liquefaction. The thermally disintegrated oil is also known as "heavy oil". Liquefaction also produces condensable vapors, referred to as "condensed gases" or "condensate", and non-condensable vapors that do not condense under the cooling conditions of the liquefaction process. It has been found that the wide variations in the chemical composition of the waste plastic material are not reflected in the chemical composition of the thermally disintegrated oil. In this way, the chemical composition of thermally disintegrated oil or heavy oil is significantly less variable than the plastic waste material, while the chemical composition of condensates and / or non-condensable gases is more consistent with that of the feedstock. of waste plastic. This is an important factor because the thermally disintegrated oil constitutes approximately 70% by weight with approximately 80% by weight of the feed raw material of the gasifier. Therefore, a stable composition is important. The variation in the chemical composition of the condensates can be attenuated by mixing. The variation of the composition in non-condensable gases can be treated using these gases as fuel for the heating unit used in the liquefaction process. The process of the invention is capable of partially oxidizing waste plastic materials containing liquefied halogen in a useful synthesis gas with minimal liquid discharge and is not environmentally toxic. With "non-toxic environmentally" it is indicated that almost no gases are released into the environment, toxic liquids or solids. The process is designed to self-contain and does not release any toxic vapor, liquid or solid. Therefore, no dangerous vapor, liquid or particulate solid enters the environment. The secondary product of the slag is vitreous and non-leachable, and can be used as a public landfill or for construction. The term "vitreous slag" refers to a slag that chemically or physically links elements and / or compounds that can be harmful to the environment in its free state. These elements and / or bound compounds are resistant to the leaching of the slag. Accordingly, vitreous slag produced in the present invention is environmentally non-toxic slag. The reduction in particle size of bulk waste plastic in conventional processes before liquefaction is perhaps one of the most expensive aspects of a waste plastic recovery operation. A major advantage of the process of the invention is that only a minimal reduction in the size of the slag plastic is needed. The reduction in size to an average particle size of about 18 inches is all that is needed to feed the waste plastic material to the liquefaction step. However, reducing the particle size to an average particle diameter of about 6 inches and preferably about 2 inches is desirable to facilitate the magnetic removal of contaminants or metal components contained in the slag plastic. These particle sizes denote waste plastic materials as bulk particles that have been subjected to a minimum particle size reduction that can be transported conveniently, such as by pumping plastic waste materials with bulk particles towards a liquefaction container. In contrast, conventional liquefaction processes require the reduction of the particle size of the waste plastic to less than 1 centimeter. This usually requires expensive crushing and other special conditions and equipment to prevent melting and agglomeration of the plastic by the mechanical heat generated by the crushing operations mentioned. Therefore, the process of the invention can be characterized as "resistant" due to its great ability to liquefy and partially oxidize waste plastic materials with a minimum amount of size reduction. This is an important feature and a benefit of the invention. Another advantage of the process of the invention is that the heat necessary to melt and disintegrate the waste plastic material to form a hot liquid or oil is almost entirely supplied by the thermal values recovered from the operating steps of the process. Therefore, the process can also be characterized as substantially or completely autogenous. The prior art conditions for dehalogenation are much more limiting than the simple melting, viscosity reduction and disintegration operations carried out in accordance with the present invention. This is because the processes of the prior art operate to produce a liquid product with less than 200 parts per million (ppm) of halide, preferably less than 50 ppm. In the present invention, the dehalogenation that occurs during liquefaction is incidental, and is not necessary, or even particularly desirable. The prior art processes disintegrate and operate to dehalogenate while the present invention disintegrates and operates primarily to reduce the viscosity of the disintegrated oil formed from the waste plastic material. Conventional dehalogenation produces a vapor with halogen acid contaminated with organic materials such as, for example, organic acids, aromatics, esters, aldehydes, glycols and the like. This steam with halogen acid is suitable only for incineration in order to recover pure halogen acids or salts, and it is not marketable as acids due to the organic fraction contained therein.

It is also not useful as a fuel or raw material for organic feed because the halogen content is corrosive to the combustion equipment and the purification of the slag gas is required to avoid emissions of the halogen acid, such as, for example, HCl. If it is used as an organic feedstock, the halogen content can poison the catalyst and contaminate the product. Separately from the present invention, the acid vapor from the dehalogenation of plastics should be incinerated to produce an organic free acid. The plastic waste material used in the process of the invention can be derived from thermoplastic or thermoset plastics that have been used in the packaging, structural, construction, electrical and textile industries. More often, these materials are obsolete or waste plastics that are no longer needed and have been used in the manufacture of items for daily use in the home or industry, such as containers, packaging materials, household devices, equipment of sport and toys. Plastic waste materials can also be derived from defective manufacturing batches and waste and unusable waste from the production and processing of different plastic items. In this way, plastic waste can be simply characterized as an obsolete plastic material or post-consumer waste that can not be regenerated or economically reused. All plastics found in household waste can be tolerated in the process. Disposable plastic materials that can be used in the present invention include polyolefins, vinyl resins such as polyvinyl chloride, polyvinyl acetate, and polyvinyl alcohol. In addition, polystyrenes, polycarbonates, poly (methylene oxides), polyacrylates, polyurethanes, polyamides, polyesters and hardened epoxy resins can also be used. Referring to the FIGURE, bulk plastic materials containing halogen 2 are fed to a melting vessel 3 where the waste plastic material 2 comes into direct contact with the hot oil melting medium 14 under substantially oxygen-free conditions. and at the minimum temperature necessary to melt the waste plastic in order to form a fused viscous mixture 4 which includes the waste plastic material containing halogen 2 and the hot oil 14. The melting temperature of the bulk waste plastic is maintained as low as possible to reduce the production of waste gases 6 which are vaporized from the waste plastic material during the melt pass and include hydrogen halides, light hydrocarbons, halohydrocarbons such as methyl chloride and ethyl chloride, and carbon dioxide and water vapor. The most common halogen-containing compound is hydrogen chloride, which is produced mainly from waste polyvinyl chloride. The preferred melting temperature range is from about 110 ° C to about 375 ° C. The steam stream from the discharge gases 6 generated from the waste plastic material during the melt passage passes to a cooler 7. The molten viscous mixture 4 from the molten plastic in hot oil is passed to a heater 5 operating at the minimum temperature necessary to thermally disintegrate the molten viscous plastic mixture 4 into a hot oil composition containing low molecular weight halogen and low boiling point 8 with reduced viscosity. The preferred viscosity is less than about 3,000 centipoise (cp), preferably about 1,000 cp or less, where the viscosity is measured at the outlet temperature of the heater 5, which ranges from about 350 ° C to about 430 ° C, and also is the operating temperature range for the thermal disintegration operation. The operation of the heater 5 at this temperature reduces the amount of vapor stream of the discharge gas 9 which usually includes hydrogen halides., halohydrocarbons, light hydrocarbons and carbon dioxide. Substantially, no water vapor is produced in the steam of the discharge gas 9 which is separated from the hot disintegrated oil 8. The vapor stream of the discharge gas 9 and the vapor stream of the discharge gas 6 enter the cooler 7 where they are subjected to a condensation at a temperature of about 20 ° C to about 70 ° C, to form a stream of condensed gas 18 which includes a water-miscible condensate, a hydrocarbon condensate immiscible with water and any condensed halide. If desired, the hydrocarbon condensate not missable in water or a portion thereof can be separated, purified and sold commercially. An uncondensed organic gas stream 12 is also produced and serves as fuel for the heater 5. A portion 14 of the hot disintegrated oil stream 8 is recycled in a melting vessel 3 to serve as the melting medium. Generally, the hot oil stream 14 is recycled to the melting vessel 3 at a weight ratio of the hot oil stream 14 to the bulk plastic waste materials 2 from about 1: 1 to about 6: 1, respectively. It has also been discovered that by introducing H20 into the melting vessel 3 and / or the heater 5, the formation of halohydrocarbon gas compounds and other polar compounds such as acetone in the discharge gas streams can be suppressed or reduced. 6 and 9. Chloromethane or methyl chloride, CH3C1, is the most volatile of the halohydrocarbons formed from the liquefaction of waste plastic materials, and is likely to contribute to the problems caused by the chlorine content of the fuel gas no condensate 12 entering the process heater 5. To suppress the formation of gaseous halohydrocarbon compounds, H 0, preferably in the vapor form, can be introduced into the molten oil / plastic mixture 4, and / or the stream of the disintegrated oil 8, and / or the stream of the hot recycle oil 14, and / or directly to the melting vessel 3. In addition, the plastic material of the Bulk container 2 may come into contact with H20 as it is introduced into the heating container 3. Another benefit of introducing steam or water to the liquefaction process is that the vapor can condense a substantial amount of hydrogen chloride vapor ( HCl). The process water condenses the vapors of the halogen acid in the streams of the discharge gas 6 and 9, thereby preventing or reducing the vapors of the halogen acid becoming part of the non-condensable gas stream 12 entering the heater 5. However, the amount of H20 should be monitored carefully for optimal results. By increasing the amount of water the charge in the cooler / condenser 12 is increased. It has been found that about 5% by weight with about 15% by weight of water in the feed of the waste plastic into the melting vessel 2 or introduced into the of the reactor section of the gasifier 10, represents a good balance between the acid content in the non-condensable gases and the thermal load in the chillers. The water content of the waste plastic materials 2 is generally sufficient to supply the necessary amount of steam to suppress the formation of gaseous halohydrocarbon compounds. However, the presence of halo-hydrocarbons in the uncondensed gas stream 12 would indicate the need for additional steam in the order of about 5% by weight of H20 to about 10% by weight of H20, based on the total weight of the Feeding the waste plastic. It has been found that approximately 10% by weight of H20 in the vapor form, based on the total weight of the waste plastic feed, added directly to the melted oil / plastic mixture and fed to the heater, resulted in approximately an 86% reduction of chloromethane in the discharge gas. The stream of the condensed gas 18 containing any remaining condensed halide is fed to the gasifier 10 for the partial oxidation reaction. During the partial oxidation reaction, a synthesis gas is produced which includes carbon monoxide, hydrogen, carbon dioxide, water vapor and gaseous halides HX, where X can be chlorine, fluorine, bromine or iodine. The stream of the non-condensed gas 12 from the cooler 7 entering the heater 5 serves as the fuel thereof to increase the temperature to the level necessary to thermally disintegrate the viscous molten plastic 4 in the disintegrated hot oil stream 8. The disintegration temperature varies from about 360 ° C to about 430 ° C. A portion of the disintegrated hot oil stream 8 leaving the heater 5 is divided into streams 14 and 16 after the discharge gas stream 9 is separated therefrom. The warm disintegrated oil stream 14 is recycled into the melting vessel 3 to serve as the hot oil melting medium used to directly contact and melt the waste plastic material 2 entering the melting vessel 3. During startup, The used motor oil, or any low volatility oil, or the disintegrated oil retained from the process, can be used as the melting medium. However, once the process is operative, the recycle stream 14 of the hot disintegrated oil supplies substantially or completely all of the melting medium necessary to melt the bulk waste plastic materials containing halogen 2 into the melting vessel 3. .

The warm disintegrated oil stream 16 enters the gasifier 10 with the stream of the condensed gas 18 to serve as the complete or substantially complete hydrocarbon reactant for the partial oxidation reaction. The disintegrated oil stream 16 contains the remaining non-vaporized halogen content of the waste plastic material, which may vary from about 0.1% by weight to about 2% by weight of the oil stream 16. Oxygen or a gas stream that containing oxygen 22, such as air, is fed into the reaction zone (not shown) of the cooling gasifier 10 to serve as the oxidation agent for the partial oxidation reaction. A material with a low heating value 20 can be used as a temperature moderator to control the temperature in the reaction zone of the gasifier. The material with heating value under 20 passes within the reaction zone of the gasifier in sufficient quantities to control or moderate the temperature in the reaction zone from about 1,200 ° C to about 1,600 ° C. The temperature moderator can be water, steam, ash, C0, gas rich in C0, nitrogen, recycled synthesis gas and the like. The partial oxidation reaction carried out in the gasifier 10 with the disintegrated oil 16, the condensed gases 18 and the oxidation agent 22 produces a synthesis gas or "syngas" which mainly includes carbon monoxide and hydrogen, and smaller amounts of carbon dioxide, water vapor, hydrogen sulfide, carbonyl sulphide, hydrogen halides and methane. A secondary product of the molten slag is also produced. The synthesis gas and the slag pass into the cooling zone (not shown) of the gasifier 10 and come into contact with the water, referred to as "cooling water". The purified synthesis gas leaves the cooling zone of the gasifier 10 as a stream of synthesis gas 24 and is purified for later use. The slag 28 leaves the cooling zone of the gasifier 10 and is in a glassy, non-leachable state and is not environmentally toxic. The slag 28 can be used as a construction material, for road filling or other purpose. The hydrogen halide gases that are produced in the reaction zone of the gasifier are condensed to form acid halides which are neutralized in the cooling zone to form halide salts, such as for example NH 4 Cl, NaCl, CaCl 2, MgCl, or any another equivalent halide salt, with another halogen substituted by chlorine. A portion 26 of the cooling water from the cooling zone of the gasifier 10 is continuously removed and is generally referred to as a "purge". The purge stream 26 contains any solid particulate matter remaining finely divided and the condensed halide salts. The amount of purge cooling water 26 that is continuously removed from the cooling zone of the gasifier is based on the halide content and the amount of residual solids contained in the cooling water. The halide content and the amount of finely divided residual solids is periodically divided from samples or by a process analyzer. The withdrawn cooling water velocity 26, also referred to as the "purge rate" is programmed to maintain the concentration of the halide salt below its saturation concentration under all operating conditions in the cooling water system. In general, these salt concentrations vary from about 1000 ppm to about 20% by weight of the cooling water system. The rate of removal of the cooling water is coordinated and regulated with the cooling water supplied to the cooling zone to maintain a constant and continuous supply of cooling water in the cooling zone. EXAMPLE 1 A mixture of plastic waste materials is heated to 750 ° F (399 ° C) and melted in a batch reactor stirred at one atmosphere and maintained at this temperature for 30 minutes, to produce 80% by weight of oil, 15% by weight of condensable steam and 5% by weight of non-condensable steam (at 90 ° F and 1 atmosphere). The viscosity of the oil in the product is approximately 300 centipoise at 600 ° F. At 800 ° F (427 ° C) and the same time and pressure conditions, ie 1 atmosphere and 30 minutes, the gas product increases to 20% by weight and exceeds the fuel needed for the liquefaction stage, and it is not suitable for gasification, since it would be economically unfeasible to compress the excessive gas and place it in the gasifier. Therefore, surplus gas could be used only if it can be melted with the use of gas from the fuel at the associated site. EXAMPLE 2 Several tons of post-consumer waste plastic materials are added over a period of 5 days to a melting tank where the initial start-up melting medium used is motor oil, until it is replaced by the continuous circulation of the mixture of disintegrated oil and plastics to a process heater on and back to the melting tank as in FIGURE. The melting temperature ranges from 400 ° F to 700 ° F at a pressure of one atmosphere.All molten mixture is heated to 780 ° F (416 ° C) in the process heater and returned to the melting tank. For several days, the ratio of the recycled oil to the plastic feed exceeds 50: 1. The mass of condensable steam and the non-condensable gas generated is equivalent to the mass of the plastics added EXAMPLE 3 Several tons of plastic waste materials post-consumption are added to a melting tank 3 for a period of 12 days.The mixture of oil and molten plastics exiting the melting tank is circulated through an ignited heater 5 and returned to the melting tank 3 as in the FIGURE, with the exception that a portion of the condensate and heavy oils is removed to store periodically in order to maintain the levels in the process vessels. Storage: The condensable vapors and the non-condensable gases are continuously withdrawn to the storage tanks. The molten mixture is heated to a temperature ranging from 650 ° F (343 ° C) to 780 ° F (416 ° C) in heater 5 before recirculating to melting tank 3 operating between 500 ° F (260 ° C) C) and 680 ° F (360 ° C). The residence time in heater 5 averages 5 minutes. Gas production varies from 10 to 20% by weight, and the production of disintegrated oil varies from 60 to 80% by weight. Almost no viscosity reduction of the disintegrated / plastic oil mixture is observed at disintegration temperatures lower than 650 ° F (343 ° C). The viscosity of the disintegrated oil leaving the process heater varies from 80 to 300 centipoise at 600 ° F (316 ° C). The oil derived from the plastic and the condensate generated are subjected to partial oxidation in the gasifier 10. The gasification efficiency of this oil is equivalent to or less than other commercially gassed heavy oils since the conversion of carbon to the synthesis gas is greater in the same gasifission condiions. In all these cases, less than 20% by weight of the sloro in the feed plastics remained in the heavy oil.

Claims (10)

1. CLAIMS 1. A liquefaction process to convert a plastic waste material in bulk that is halogen into the liquid hydrosorbonate feed material for a reassessment of the oxidation of the parsial is to produce a synthesis gas, which includes: (a) fusion of a bulk dessoft plastissue material which are halogen at atmospheric conditions in a confetti diresto melting zone are a salting outgoing salting medium generated from the plastid waste material at a first sufficient temperature to produce a viscous melted mixture of the plastic material of desesho that are halogen are the salient aseite, and a first gas of dessarga; (b) thermal disintegration of the viscous viscous oil / plastic mixture in a zone of salefassión at a second sufficient temperature to produce a composition of the disintegrated substance which is halogen of redusiated visosity; (c) partial oxidation of the disintegrated oil in the reactive zone of a cooling gasifier, where the disintegrated asease serves as a primary hydrosharpening reagent in a non-catalytic partial oxidation reaction to produce a synthesis gas containing hydrogen halides; (d) cooling of the synthesis gas in the cooling zone of the gasifier, where the synthesis gas enters into contaste with cooling water containing sufficient neutralizing agent to condense and neutralize the hydrogen halides in the synthesis gas, and this way, forming condensed halide salts that are separated and recovered from the cooling water, and a synthesis gas substantially free of halogen.
2. 2. The process of claim 1, wherein the bulk waste plastics material is melted in the presence of H20 in the melting zone to suppress the formation of halohydrosarbide vapors in the first dessarga gas.
3. 3. The process of claim 1, wherein a portion of the disintegrated halogen containing oil and exiting the heater is separated and recycled to the melting zone to serve as the melting medium of the hot oil.
4. 4. The process of claim 1, wherein the first discharge gas is cooled and condensed to form a water-miscible condensate, a water-immiscible condensate and a non-condensed gas mixture.
5. 5. Proseso of the reivindisasión 1, where the plastiso material of desesho in bulk that are halogen proportions sustansialmente all the reastivo hydrosarbonado for the reassión of the oxidasión parsial.
6. 6. The process of claim 1, wherein the plastic waste material containing bulk halogen is subjected to a minimum size reduction before the melting step.
7. 7. The process of claim 1, wherein the step of fusion is carried out in the absence of a satallizer.
8. 8. The process of claim 1, wherein the halogen content of the dessyst plastis material ranges from about 0.5% by weight to about 10% by weight.
9. 9. The process of claim 1, wherein the halogen-containing bulk plaster material is melted at a temperature from about 110 ° C to about 375 ° C.
10. 10. The process of claim 1, where a material is a value of low discharge of the group formed by water, seniza, inert gases and mixtures of the above, is introduced into the area of reactivation of the gasifier to serve as moderator of temperature.