CA2024340A1 - Process for the complete reprocessing of high polymer waste products - Google Patents
Process for the complete reprocessing of high polymer waste productsInfo
- Publication number
- CA2024340A1 CA2024340A1 CA 2024340 CA2024340A CA2024340A1 CA 2024340 A1 CA2024340 A1 CA 2024340A1 CA 2024340 CA2024340 CA 2024340 CA 2024340 A CA2024340 A CA 2024340A CA 2024340 A1 CA2024340 A1 CA 2024340A1
- Authority
- CA
- Canada
- Prior art keywords
- waste products
- plasma
- polymer waste
- polymer
- converted
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/62—Plastics recycling; Rubber recycling
Abstract
ABSTRACT OF THE DISCLOSURE
High polymer waste products fill the garbage dumping grounds or they are only insufficiently converted into new low-quality products by means of imperfect recycling processes. The novel process according to the present invention will make it possible to process high polymer, preferably those which contain no volatile matter that can be defined by standardized measuring methods independently of their chemical composition and physical consistency in a form such that the raw material substance contained therein is completely reusable.
The polymer waste products are converted into a crushed or granulated form and into a conveyable consistency by mixing them with superheated steam and by feeding them to a hydrogen plasma jet having an average mass temperature of at least 1000°C and a pressure of 0.05 to 0.5 MPa so that the polymer suspension or granulate is mixed with the hydrogen plasma.
In this hydrogen plasma the polymer waste products are completely decomposed and are reacted to highly endothermic valuable target products, such as acetylene, ethylene, hydrogen, CO, HCN or HCl.
The aim is the complete material reprocessing and high finish of all the high polymers made available by the chemical industry, i.e., those having passed through one or several utilization processes.
High polymer waste products fill the garbage dumping grounds or they are only insufficiently converted into new low-quality products by means of imperfect recycling processes. The novel process according to the present invention will make it possible to process high polymer, preferably those which contain no volatile matter that can be defined by standardized measuring methods independently of their chemical composition and physical consistency in a form such that the raw material substance contained therein is completely reusable.
The polymer waste products are converted into a crushed or granulated form and into a conveyable consistency by mixing them with superheated steam and by feeding them to a hydrogen plasma jet having an average mass temperature of at least 1000°C and a pressure of 0.05 to 0.5 MPa so that the polymer suspension or granulate is mixed with the hydrogen plasma.
In this hydrogen plasma the polymer waste products are completely decomposed and are reacted to highly endothermic valuable target products, such as acetylene, ethylene, hydrogen, CO, HCN or HCl.
The aim is the complete material reprocessing and high finish of all the high polymers made available by the chemical industry, i.e., those having passed through one or several utilization processes.
Description
20243~
The present invention is applicable to the complete material reprocessing and high finish of all the high polymers made available by the chemical industry such as plastics, plastic fibres having passed through one or several utilization processes and being unsorted in the form of wastes, secondary raw materials of PVC, polyethylene, polystyrene, polyamides, polyesters, polyacrylates, etc., polluted or non-polluted and with or without structure damage due to ageing or due to the action of light and other environmental influences.
In the past few years the search for possibilities of recycling high polymer waste products has intenslfied. This includes particularly waste products such as bottles containers buckets, piping , sheets, foamed plastics, packages, panels, bullding materials, chemical fibres, etc., of PVC, polyethylene, polystyrene, polyamides, polyesters and polyacrylates, etc., but also intermediate products and monomer products that are required for their production.
Today some of these high polymer products are collected and acquired by some means and attempts of recycling them which principally are more or less incomplete are applied but nevertheless constitute some kind of saving of raw materials and energy.
The principal procedure for the re-use particularly of plastic plastics waste materials lies in remelting down, homogenizing ad transforming the high polymer waste products.
Thus, for example, a pro~ess for producing moulded parts of thermoplastic polyester moulding material by means of in;ection moulding is described in DD-PS 222 544.
A similar process for producing moulded parts from polyurethane wastes is described in DD-PS 144 885 and a process for the 202434~
preparation of the PU elast mould wastes for said process is described in DD-PS 262 237.
A process for producing moulded parts from a plastic mixed material from secondary polyethylene and rubber is described in DD-PS 137 938.
DD-PS 247 690 relates to the production of a rubber mixture, capable of being in~ection moulded, from old rubber.
DE-PS 3 603 009 describes a complete process for producing moulded parts, including the process stages detection, preclassification, purification and plastification.
Further processes dealing with these problems are described in DE-PS 3 544 417, DE-PS 3 901 139, DE-PS 3 441 906, DE-PS 3 242 120, EP 0 248 239, WO 85/00 480.
All these processes allow a profitable recycling, that is sub~ected to substantial limitations and thus has disadvantages:
1. When repeatedly uslng the converted polymer materials there occurs a substantial loss in stability and quality due to ageing so that the fields cf application are greatly restricted. An additional factor is the processing of a large number of different colours, whereby the optical attractiveness is substantially reduced. The polymer materlal cannot be passed through the recycling process several times so that the hydrocarbon substance of these products eventually gets to the garbage dumping grounds in any case. A fundamental solutlon of the raw material problem is thus not attained with this group of processes. 2. Only thermoplastic high pol~mer waste products can be processed in the above-mentioned processes. 3. The high polymer waste products to be processed must be graded and, in most cases, also purified. This requires the application of additonal processes (DD235 376, DD 256 048, DD 233 794, DD 207 zo2a~34n 629, DE 3 634 808, DE 3 535 633, DE 3 601 175, DE 2 900 666, DE 2 639 864).
However, a second group of processes allows a better re-use of the plastics waste products so that by controlled decomposition re-usable products having a lower degree of quality loss are formed in that not only ls a physical conversion carried out by a chemical conversion is also carried out. This group includes a process according to DD-PS 216 474 in which a rubber that can be vulcanized again is formed by devulcanization of old rubber wlth cleavage of the sulphur bridges while protecting the polymer structure by reducing replastification under the action of aldehydes.
In a process described in DD-PS 134 773 residues of the ethylene suspension polymerization are sub~ected to a thermooxidative degradation at 130C to 250C in the presence of 2 or oxygen-containing gases and by adding viscosity-reducing substances a partially oxidized polyethylene wax is formed as produ~t.
A process ln which residues of the ethylene suspenslon polymerlzatlon are sub~ected to a thermooxldative degradation at 130 to 250C ln the presence f 2 or oxygen-containing gases and by adding viscosity-reducing substances a partially oxldlzed polyethylene wax is formed as product, is descrlbed ln DD-PS 134 773.
A process for reprocessing isocyanate-contalning distillation residues by conversion lnto lsocyanates is described ln DD-PS 238 988. In this process the residues are reacted wlth epoxide compounds at temperatures below 300C and mixed with dl-or polyisocyanates.
Furthermore, the reprocessing of special plastics wastes is known from the following patents: DD 146 826 Production of flexible hot melt adhesives based on polyester by alcoholysis while ;~0243~
continuously adding diols and polyalkylene oxides at pressures of up to 2.0 MPA and by subsequent polycondensation. DD 141 525 Recovery of hydrogen-active compounds from polyurethane wastes.
DD 130 256 Process for the production of hot melt adhesives from polyester wastes. DD 125 979 Process for the utilization of crosslinked polyester and epoxide resin wastes. DE 3 0~7 829 Conversion of wastes from polyolefins in a careful procedure lnto higher-valence modified pitches and low-boiling aromatic substances and olefins at medium pressures and at temperatures above 300C. DE 2 951 617 Recycling of Polyurethane by alcoholysis or acidolysis. DE 2 911 203 Process for the recovery of polystyrene by selectively dissolving them in liquid SO2 in a first step and by evaporating the SO2 in a second step. EP 0 052 213 Process for the catalytic depolymerization of polytetramethyl glycol ether in the presence of bleaching clay as catalyst at ~emperatures of 90 to 180C with the aim of producing tetrahydrofuran. EP 0 048 340 Recovery of caprolactam from nylonoligomers. EP 0 031 538 Recycling of polyurethane by alcoholic and acidolysis. EP 0 000 948 Production of polyol-containing liquids from polyurethane wastes in the presence of intensily basic compounds at temperatures of 150 to 220C.
All the processes of this group have the following disadvantages:
1. The range of application is highly specifically dlrected to a specific polymer type with a limited share in the total yleld of society in most cases. 2. The problem of making the polymers available in a graded conditlon remalns inasmuch as the starting product is not a residue that is obtalned directly in the production of the polymers. 3. The polymer product is converted into a qualitatively more or less high-grade product that is useful in a different way; a true recycling for the reproduction of a new original polymer does not occur.
A further known recycling process is the hydrogenation of carbon-containing wastes at temperatures of 75C to 600C and at high pressure of up to 600 ~ars tRheinbraun process DD-PS 249 036).
Z0~3~
Apart from the disadvantages of an additional hydrogen consumption and of the required high pressures necessitating high technical expenditure, this process has the disadvantage that there are formed undefined hydrogen carbon mixtures which cannot be used without further processing. Recycling directly into the polymer synthesis is not possible.
FUrthermore, pyrolysis processes operating in the temperature range of 150C to 500C (DE 3 323 161) and 400C to 650C (DE 3 531 514) are also known. The first process can process only thermoplastic plastics. The resulting products are of low value and their further use is difficult. In the second process the low-grade pyrolysis waste gases are passed to a thermal afterburning stage without any further utilization. This process thus is only useful for the destruction of secondary polymers and varnish sludges.
A process that also is only useful for the removal of plastics wastes is described in DE-PS 2 409 966. In the process protected by said patent the photodissocation of plastics wastes by sunlight is substantially accelerated by applying decomposition accelerators such as manganese, iron, cobalt, nickel or copper salts of higher-fatty acid.
Furthermore, process for the plasma pyrolysis and for the plasma gasification of crude fossil material such as coal, coal-containing substances, petroleum and natural gas are known. The pyrolysis of old tires resulting in low-grade and inapplicable carbon blacks, oils and pyrolysis gases is also known.
It is the aim of the present invention to devise a process which allows the processing of all the secondary high polymers obtained, preferably those which originally contain no volatile matter that can be defined by standardiæed measuring methods, independently of their chemical composition and physical consistency, ln a form such that the raw-material substance ~02~4(~
contained therein, i.e., C, H, Cl, can be completely used again so that by utilizlng the existing sequence chemistry a synthesis of completely new, unrestrictedly applicable high polymer is obtained from the old substance, i.e., an almost 100% true recycling process.
According to the present invention this aim is achieved in that the hi~h polymer waste products are converted by plasmachemical means into their chemical basic materials from which they had originally been synthetized, such as acetylene, ethylene, hydrogen, HCN, CO, ~Cl and carbon black. The high polymer waste products are suitably sub~ected to a plasma hydrolysis under reducing conditions or to a plasma gasiflcation at the simultaneous presence of reducing and oxidizing plasma conditions.
For this purpose the high polymer waste products are granulated or comminuted in some other way, converted into a conveyable consistency mixed with superheated steam and fed to a hydrogen plasma ~et having an average mass temperature of at least 1~00C
and a pressure of 0.05 to 0.5 MPa so that the polymer suspension or granulate and the hydrogen plasma are mixed. The nascent reactive plasma subsequently enters a plasma reactor. After a residence time of 10-3 to 30 seconds in the plasma corresponding to the chemical composition and the physlcal state, for example, the particle slze, the plasma ~et is quenched to temperatures below 1000C and thus converted into a pyrolysis gas current.
The solids present in the plasma pyrolysis gas current, such as carbonized polymer waste products or carbon black, are removed from the plasma pyrolysis gas, which is completely or partially separated into its constituents.
For the conversion into a conveyable consistency the comminuted or granulated polymer waste products suitably are thermally melted down, preferably in an extruder, dissolved in a solvent or solvent mixture, suspended in water or hot steam, hydrogen, ;~02~4~
methane, carbon dioxide or fuel gas, etc., are passed in as entraining gas. The complete or partial separation of the plasma pyrolysis gas forming in the plasma process into its constituents is preferably carried out by absorption and low temperatures distillation. The constituents thus forming can then also be passed on to corresponding polymer synthesis processes, either entirely or partially.
The mode of operation of the process according to the present invention lies in that long-chain molecules, like those represented by all the high polymers, even those of a textile nature, have a relatively low bond energy between the carbon atoms which facilitates easier cleav'age into hydrocarbon fragments than is the case, for example, in fossile carbon carriers, e.g., coal.
Under the conditions of a reactive hydro~en plasma all the high polymers are split into fragments, which split into the thermodynamically most favourable compounds, such as acetylene ethylene, hydrogen, CO, HCl, HCN, i.e., highly energetic compounds which also represent the chemical starting substance for the todays production of all known polymers. Polyethylene thus is reacted by the action of a hydrogen plasma ~et according to the following overall reaction formula:
~ -Plasma (CH2 ) n ~ -~ ~ a C2H2 + b a2II4 + c ~ + d C
The coefficients a, b, c and d depend on the plasma temperaturs, i.e., the dlssociation degree and the plasma enthalpy. Polyvinyl chloride reacts in the hydrogen plasma accordlng to the following overall reactlon formula:
~02434(:~
~ ~Plasma (CH2~ICl)n C2H2 ~ b C2H4 t c H2 ~ d C + e HCl As to the meaning of the coefficients a, b, c, d, and e the same applies as in the rsaction of polyethylene.
The admixture of superheated steam to the polymer granulate or suspension prior to mixing them with the plasma ~et prevents the formation of carbon black in favour of the formation of hydrogen and of an additional formation of C0, i.e., the superheated steam participation in the reaction in a controlled manner.
The use of polyacrylates in the plasma ~et results in a conversion into the products acetylene C2H2, ethylene C2H4, hydrogen H2, carbon black C and HCN.
In the reaction in a hydrogen plasma ~et polystr~ne yields acetylene C2H2, ethylene C2H4, hydrogen H2 and carbon black C
and, depending on the application of hot steam, CO in favour of the formation of carbon black. It is important for the process according to present invention that the hlgh polymer waste products usually contain no volatile products deterrable by conventional test methods, i.e., that these products, as for example, coal, cannot be measured for this purpose by standardized methods.
The required reaction time, i.e., the residence time of the high polymers in the plasma ~et, depends on the manner of introducin~
the high polymer waste products into the plasma jet, i.e., granulate suspension or melt, on the particle si2e of the high polymer waste products and on their chemical structure and is between 10-3 and 60 seconds.
Finally, from the plasma pyrolysis of high polymer waste products by means of the process according to the present invention, any 2024~0 of the basic chemical materials for today's polymer synthesis, i.e., acetylene C2H2, ethylene C2~4, hydrogen H2 carbon monoxide CO, hydrocyanic acid HCN as well as methanol (via H2/CO
mixtures)~ acetaldehyde, acetic acid ( via acetylene), can be obtained. A basis for a novel synthesis of all known polymer materials with the known sequence chemistry of the above-mentioned basic materials is thus provided.
Example 1 A mixture of more than 50% by weight of thermoplastic high polymer waste products (for example, polyethylene, is granulated in a granulating mill, then melted down in an extruder at 115C
(thermoplastic component) and subsequently pressed by said extruder ln to an admixture division of a plasma pyrolysis reactor that encases a hydrogen plasma ~et having an average mass temperature of 2500C. In said reactor the surface of the polymer suspension flow passing through the admixture division is cleared off and is chemically d~ssociated in the plasma within a reaction time of 10 seconds and converted into acetylene and hydrogen.
The reactive plasma is ~quenched~ by the recycle gas quenched at the outlet of the plasma reactor and the product C2H2, C2H4H2 are stabilized.
On separating the solids and washing the acetylene solvent the residual pyrolysis gas mlxture is passed to a gas separator in order to obtain the pyrolysis gas components in a pure form.
Said components are then again passed to a polymer synthesis.
Example 2 Polyethylene waste products are granulated in a granulating mill and subsequently melted down in an extruder at 180C and homogenized. The melt is atomized in a highly fluid state by - 2024~40 superheated steam havlng a temperature of 250C and a pressure of 0.5 MPa and are passed to a hydrogen plasma ~et having an average mass temperature of 3000C. The products acetylene, ethylene, CO, H2 and C formed after reaction time of 0.5 second in the plasma reactor designed as a fluid~zation reactor, are stabilized with cold recycle pyrolysis gas at the reactor outlet and, after separating the carbon black they are passed to a gas separator.
ExamPle 3 Polyvinyl chloride wastes are granulated in a granulating mlll, whereupon they are mixed with a solvent mixture of trichloroethylene and tetrachloromethane in an attached agitator at 80C. At the same time the PVC waste product is partially dissolved and solubilized and the nascent suspension is fed by means of pump pressure lnto the admlxture divislon of a plasma pyrolysis reactor while adding superheated steam. A hydrogen plasma jet having an average mass temperature of 2000C is spreading in sald reactor. Solvent and polymer wastes are ~ointly reacted plasma chemically to acetylene, ethylene, hydrogen, HCl and carbon black within a reaction time of 1 second, quenched with cold pyrolysis recycle gas at the reactor outlet and subsequently passed to the mechanical separation of carbon black, then washed with water and passed to gas separator.
In a further variant the polymer/solvent suspenslon is fed by means of pump pressure to the admixture dlvislon of the plasma reactor, where it ls in~ected into the hydrogen plasma ~et by means of hot steam having a temperature of 250C.
Example 4 An undeflnable mixture of various non-thermoplastic polymer wastes is granulated in a granulating or beater mill, whereupon it is fluidized with superheated steam of 250C to 300C as entraining gas in a plasma reactor, which encases an H2 plasma ~)2434f) jet having an average mass temperature of 2500C. In the plasma reactor, designed as fluidized-bed reactor, the granulated polymer substance is completely reacted into high-grade polymer products, such as acetylene, ethylene, hydrogen, CO and HCl at an average residence time of 1 minute.
The pyrolysis gas, which has a resldence time of 10-3 second in the rector, is quenched in water at the reactor outlet and ls passed on for the separation of carbon black and subsequent washing with HCl. The separation into the components of the polymer starting product is carried out in a subsequent gas separation analysis.
The quenched pyrolysis gas leaving the reactor has the following composition:
C2H2 = 5 to 10% by volume C2H4 = ~ to 3% by volume H2 = 50 to 70% by volume CO = 5 to 10% by volume HCl = 10% by volume Apart from the complete recycling, further advantages of the process according to the present invention are:l. it is gentle on the sources of primary energy carriers. 2. The expenditure for the extraction and the preparation of fossile raw material can be dispensed with. 3. Reduction of the energy consumption for the production of the polymers to 60 tod 70~ as compared with the procedure via fossile raw materials slnce the high polymer can be split more readily and more completely. 4. Omission of costly process stages that are hard on the envlronment (for example, PVC
production: omisslon of the chlorine electrolysis and of the carbide furnaces for the C2H2 synthesis). 5. Continuous renewal of the polymer supply in the economy, practically without the use of raw materials. 6. The composition of the polymer product mixture influences only the composition of the pyrolysls gas ~02434~
without having a detrimental effect on the process. 7. The residues adhering to the high polymer waste products, as for example household chemicals, are also reacted to useful products, such as C2H2,C2H4,CO, etc.
The present invention is applicable to the complete material reprocessing and high finish of all the high polymers made available by the chemical industry such as plastics, plastic fibres having passed through one or several utilization processes and being unsorted in the form of wastes, secondary raw materials of PVC, polyethylene, polystyrene, polyamides, polyesters, polyacrylates, etc., polluted or non-polluted and with or without structure damage due to ageing or due to the action of light and other environmental influences.
In the past few years the search for possibilities of recycling high polymer waste products has intenslfied. This includes particularly waste products such as bottles containers buckets, piping , sheets, foamed plastics, packages, panels, bullding materials, chemical fibres, etc., of PVC, polyethylene, polystyrene, polyamides, polyesters and polyacrylates, etc., but also intermediate products and monomer products that are required for their production.
Today some of these high polymer products are collected and acquired by some means and attempts of recycling them which principally are more or less incomplete are applied but nevertheless constitute some kind of saving of raw materials and energy.
The principal procedure for the re-use particularly of plastic plastics waste materials lies in remelting down, homogenizing ad transforming the high polymer waste products.
Thus, for example, a pro~ess for producing moulded parts of thermoplastic polyester moulding material by means of in;ection moulding is described in DD-PS 222 544.
A similar process for producing moulded parts from polyurethane wastes is described in DD-PS 144 885 and a process for the 202434~
preparation of the PU elast mould wastes for said process is described in DD-PS 262 237.
A process for producing moulded parts from a plastic mixed material from secondary polyethylene and rubber is described in DD-PS 137 938.
DD-PS 247 690 relates to the production of a rubber mixture, capable of being in~ection moulded, from old rubber.
DE-PS 3 603 009 describes a complete process for producing moulded parts, including the process stages detection, preclassification, purification and plastification.
Further processes dealing with these problems are described in DE-PS 3 544 417, DE-PS 3 901 139, DE-PS 3 441 906, DE-PS 3 242 120, EP 0 248 239, WO 85/00 480.
All these processes allow a profitable recycling, that is sub~ected to substantial limitations and thus has disadvantages:
1. When repeatedly uslng the converted polymer materials there occurs a substantial loss in stability and quality due to ageing so that the fields cf application are greatly restricted. An additional factor is the processing of a large number of different colours, whereby the optical attractiveness is substantially reduced. The polymer materlal cannot be passed through the recycling process several times so that the hydrocarbon substance of these products eventually gets to the garbage dumping grounds in any case. A fundamental solutlon of the raw material problem is thus not attained with this group of processes. 2. Only thermoplastic high pol~mer waste products can be processed in the above-mentioned processes. 3. The high polymer waste products to be processed must be graded and, in most cases, also purified. This requires the application of additonal processes (DD235 376, DD 256 048, DD 233 794, DD 207 zo2a~34n 629, DE 3 634 808, DE 3 535 633, DE 3 601 175, DE 2 900 666, DE 2 639 864).
However, a second group of processes allows a better re-use of the plastics waste products so that by controlled decomposition re-usable products having a lower degree of quality loss are formed in that not only ls a physical conversion carried out by a chemical conversion is also carried out. This group includes a process according to DD-PS 216 474 in which a rubber that can be vulcanized again is formed by devulcanization of old rubber wlth cleavage of the sulphur bridges while protecting the polymer structure by reducing replastification under the action of aldehydes.
In a process described in DD-PS 134 773 residues of the ethylene suspension polymerization are sub~ected to a thermooxidative degradation at 130C to 250C in the presence of 2 or oxygen-containing gases and by adding viscosity-reducing substances a partially oxidized polyethylene wax is formed as produ~t.
A process ln which residues of the ethylene suspenslon polymerlzatlon are sub~ected to a thermooxldative degradation at 130 to 250C ln the presence f 2 or oxygen-containing gases and by adding viscosity-reducing substances a partially oxldlzed polyethylene wax is formed as product, is descrlbed ln DD-PS 134 773.
A process for reprocessing isocyanate-contalning distillation residues by conversion lnto lsocyanates is described ln DD-PS 238 988. In this process the residues are reacted wlth epoxide compounds at temperatures below 300C and mixed with dl-or polyisocyanates.
Furthermore, the reprocessing of special plastics wastes is known from the following patents: DD 146 826 Production of flexible hot melt adhesives based on polyester by alcoholysis while ;~0243~
continuously adding diols and polyalkylene oxides at pressures of up to 2.0 MPA and by subsequent polycondensation. DD 141 525 Recovery of hydrogen-active compounds from polyurethane wastes.
DD 130 256 Process for the production of hot melt adhesives from polyester wastes. DD 125 979 Process for the utilization of crosslinked polyester and epoxide resin wastes. DE 3 0~7 829 Conversion of wastes from polyolefins in a careful procedure lnto higher-valence modified pitches and low-boiling aromatic substances and olefins at medium pressures and at temperatures above 300C. DE 2 951 617 Recycling of Polyurethane by alcoholysis or acidolysis. DE 2 911 203 Process for the recovery of polystyrene by selectively dissolving them in liquid SO2 in a first step and by evaporating the SO2 in a second step. EP 0 052 213 Process for the catalytic depolymerization of polytetramethyl glycol ether in the presence of bleaching clay as catalyst at ~emperatures of 90 to 180C with the aim of producing tetrahydrofuran. EP 0 048 340 Recovery of caprolactam from nylonoligomers. EP 0 031 538 Recycling of polyurethane by alcoholic and acidolysis. EP 0 000 948 Production of polyol-containing liquids from polyurethane wastes in the presence of intensily basic compounds at temperatures of 150 to 220C.
All the processes of this group have the following disadvantages:
1. The range of application is highly specifically dlrected to a specific polymer type with a limited share in the total yleld of society in most cases. 2. The problem of making the polymers available in a graded conditlon remalns inasmuch as the starting product is not a residue that is obtalned directly in the production of the polymers. 3. The polymer product is converted into a qualitatively more or less high-grade product that is useful in a different way; a true recycling for the reproduction of a new original polymer does not occur.
A further known recycling process is the hydrogenation of carbon-containing wastes at temperatures of 75C to 600C and at high pressure of up to 600 ~ars tRheinbraun process DD-PS 249 036).
Z0~3~
Apart from the disadvantages of an additional hydrogen consumption and of the required high pressures necessitating high technical expenditure, this process has the disadvantage that there are formed undefined hydrogen carbon mixtures which cannot be used without further processing. Recycling directly into the polymer synthesis is not possible.
FUrthermore, pyrolysis processes operating in the temperature range of 150C to 500C (DE 3 323 161) and 400C to 650C (DE 3 531 514) are also known. The first process can process only thermoplastic plastics. The resulting products are of low value and their further use is difficult. In the second process the low-grade pyrolysis waste gases are passed to a thermal afterburning stage without any further utilization. This process thus is only useful for the destruction of secondary polymers and varnish sludges.
A process that also is only useful for the removal of plastics wastes is described in DE-PS 2 409 966. In the process protected by said patent the photodissocation of plastics wastes by sunlight is substantially accelerated by applying decomposition accelerators such as manganese, iron, cobalt, nickel or copper salts of higher-fatty acid.
Furthermore, process for the plasma pyrolysis and for the plasma gasification of crude fossil material such as coal, coal-containing substances, petroleum and natural gas are known. The pyrolysis of old tires resulting in low-grade and inapplicable carbon blacks, oils and pyrolysis gases is also known.
It is the aim of the present invention to devise a process which allows the processing of all the secondary high polymers obtained, preferably those which originally contain no volatile matter that can be defined by standardiæed measuring methods, independently of their chemical composition and physical consistency, ln a form such that the raw-material substance ~02~4(~
contained therein, i.e., C, H, Cl, can be completely used again so that by utilizlng the existing sequence chemistry a synthesis of completely new, unrestrictedly applicable high polymer is obtained from the old substance, i.e., an almost 100% true recycling process.
According to the present invention this aim is achieved in that the hi~h polymer waste products are converted by plasmachemical means into their chemical basic materials from which they had originally been synthetized, such as acetylene, ethylene, hydrogen, HCN, CO, ~Cl and carbon black. The high polymer waste products are suitably sub~ected to a plasma hydrolysis under reducing conditions or to a plasma gasiflcation at the simultaneous presence of reducing and oxidizing plasma conditions.
For this purpose the high polymer waste products are granulated or comminuted in some other way, converted into a conveyable consistency mixed with superheated steam and fed to a hydrogen plasma ~et having an average mass temperature of at least 1~00C
and a pressure of 0.05 to 0.5 MPa so that the polymer suspension or granulate and the hydrogen plasma are mixed. The nascent reactive plasma subsequently enters a plasma reactor. After a residence time of 10-3 to 30 seconds in the plasma corresponding to the chemical composition and the physlcal state, for example, the particle slze, the plasma ~et is quenched to temperatures below 1000C and thus converted into a pyrolysis gas current.
The solids present in the plasma pyrolysis gas current, such as carbonized polymer waste products or carbon black, are removed from the plasma pyrolysis gas, which is completely or partially separated into its constituents.
For the conversion into a conveyable consistency the comminuted or granulated polymer waste products suitably are thermally melted down, preferably in an extruder, dissolved in a solvent or solvent mixture, suspended in water or hot steam, hydrogen, ;~02~4~
methane, carbon dioxide or fuel gas, etc., are passed in as entraining gas. The complete or partial separation of the plasma pyrolysis gas forming in the plasma process into its constituents is preferably carried out by absorption and low temperatures distillation. The constituents thus forming can then also be passed on to corresponding polymer synthesis processes, either entirely or partially.
The mode of operation of the process according to the present invention lies in that long-chain molecules, like those represented by all the high polymers, even those of a textile nature, have a relatively low bond energy between the carbon atoms which facilitates easier cleav'age into hydrocarbon fragments than is the case, for example, in fossile carbon carriers, e.g., coal.
Under the conditions of a reactive hydro~en plasma all the high polymers are split into fragments, which split into the thermodynamically most favourable compounds, such as acetylene ethylene, hydrogen, CO, HCl, HCN, i.e., highly energetic compounds which also represent the chemical starting substance for the todays production of all known polymers. Polyethylene thus is reacted by the action of a hydrogen plasma ~et according to the following overall reaction formula:
~ -Plasma (CH2 ) n ~ -~ ~ a C2H2 + b a2II4 + c ~ + d C
The coefficients a, b, c and d depend on the plasma temperaturs, i.e., the dlssociation degree and the plasma enthalpy. Polyvinyl chloride reacts in the hydrogen plasma accordlng to the following overall reactlon formula:
~02434(:~
~ ~Plasma (CH2~ICl)n C2H2 ~ b C2H4 t c H2 ~ d C + e HCl As to the meaning of the coefficients a, b, c, d, and e the same applies as in the rsaction of polyethylene.
The admixture of superheated steam to the polymer granulate or suspension prior to mixing them with the plasma ~et prevents the formation of carbon black in favour of the formation of hydrogen and of an additional formation of C0, i.e., the superheated steam participation in the reaction in a controlled manner.
The use of polyacrylates in the plasma ~et results in a conversion into the products acetylene C2H2, ethylene C2H4, hydrogen H2, carbon black C and HCN.
In the reaction in a hydrogen plasma ~et polystr~ne yields acetylene C2H2, ethylene C2H4, hydrogen H2 and carbon black C
and, depending on the application of hot steam, CO in favour of the formation of carbon black. It is important for the process according to present invention that the hlgh polymer waste products usually contain no volatile products deterrable by conventional test methods, i.e., that these products, as for example, coal, cannot be measured for this purpose by standardized methods.
The required reaction time, i.e., the residence time of the high polymers in the plasma ~et, depends on the manner of introducin~
the high polymer waste products into the plasma jet, i.e., granulate suspension or melt, on the particle si2e of the high polymer waste products and on their chemical structure and is between 10-3 and 60 seconds.
Finally, from the plasma pyrolysis of high polymer waste products by means of the process according to the present invention, any 2024~0 of the basic chemical materials for today's polymer synthesis, i.e., acetylene C2H2, ethylene C2~4, hydrogen H2 carbon monoxide CO, hydrocyanic acid HCN as well as methanol (via H2/CO
mixtures)~ acetaldehyde, acetic acid ( via acetylene), can be obtained. A basis for a novel synthesis of all known polymer materials with the known sequence chemistry of the above-mentioned basic materials is thus provided.
Example 1 A mixture of more than 50% by weight of thermoplastic high polymer waste products (for example, polyethylene, is granulated in a granulating mill, then melted down in an extruder at 115C
(thermoplastic component) and subsequently pressed by said extruder ln to an admixture division of a plasma pyrolysis reactor that encases a hydrogen plasma ~et having an average mass temperature of 2500C. In said reactor the surface of the polymer suspension flow passing through the admixture division is cleared off and is chemically d~ssociated in the plasma within a reaction time of 10 seconds and converted into acetylene and hydrogen.
The reactive plasma is ~quenched~ by the recycle gas quenched at the outlet of the plasma reactor and the product C2H2, C2H4H2 are stabilized.
On separating the solids and washing the acetylene solvent the residual pyrolysis gas mlxture is passed to a gas separator in order to obtain the pyrolysis gas components in a pure form.
Said components are then again passed to a polymer synthesis.
Example 2 Polyethylene waste products are granulated in a granulating mill and subsequently melted down in an extruder at 180C and homogenized. The melt is atomized in a highly fluid state by - 2024~40 superheated steam havlng a temperature of 250C and a pressure of 0.5 MPa and are passed to a hydrogen plasma ~et having an average mass temperature of 3000C. The products acetylene, ethylene, CO, H2 and C formed after reaction time of 0.5 second in the plasma reactor designed as a fluid~zation reactor, are stabilized with cold recycle pyrolysis gas at the reactor outlet and, after separating the carbon black they are passed to a gas separator.
ExamPle 3 Polyvinyl chloride wastes are granulated in a granulating mlll, whereupon they are mixed with a solvent mixture of trichloroethylene and tetrachloromethane in an attached agitator at 80C. At the same time the PVC waste product is partially dissolved and solubilized and the nascent suspension is fed by means of pump pressure lnto the admlxture divislon of a plasma pyrolysis reactor while adding superheated steam. A hydrogen plasma jet having an average mass temperature of 2000C is spreading in sald reactor. Solvent and polymer wastes are ~ointly reacted plasma chemically to acetylene, ethylene, hydrogen, HCl and carbon black within a reaction time of 1 second, quenched with cold pyrolysis recycle gas at the reactor outlet and subsequently passed to the mechanical separation of carbon black, then washed with water and passed to gas separator.
In a further variant the polymer/solvent suspenslon is fed by means of pump pressure to the admixture dlvislon of the plasma reactor, where it ls in~ected into the hydrogen plasma ~et by means of hot steam having a temperature of 250C.
Example 4 An undeflnable mixture of various non-thermoplastic polymer wastes is granulated in a granulating or beater mill, whereupon it is fluidized with superheated steam of 250C to 300C as entraining gas in a plasma reactor, which encases an H2 plasma ~)2434f) jet having an average mass temperature of 2500C. In the plasma reactor, designed as fluidized-bed reactor, the granulated polymer substance is completely reacted into high-grade polymer products, such as acetylene, ethylene, hydrogen, CO and HCl at an average residence time of 1 minute.
The pyrolysis gas, which has a resldence time of 10-3 second in the rector, is quenched in water at the reactor outlet and ls passed on for the separation of carbon black and subsequent washing with HCl. The separation into the components of the polymer starting product is carried out in a subsequent gas separation analysis.
The quenched pyrolysis gas leaving the reactor has the following composition:
C2H2 = 5 to 10% by volume C2H4 = ~ to 3% by volume H2 = 50 to 70% by volume CO = 5 to 10% by volume HCl = 10% by volume Apart from the complete recycling, further advantages of the process according to the present invention are:l. it is gentle on the sources of primary energy carriers. 2. The expenditure for the extraction and the preparation of fossile raw material can be dispensed with. 3. Reduction of the energy consumption for the production of the polymers to 60 tod 70~ as compared with the procedure via fossile raw materials slnce the high polymer can be split more readily and more completely. 4. Omission of costly process stages that are hard on the envlronment (for example, PVC
production: omisslon of the chlorine electrolysis and of the carbide furnaces for the C2H2 synthesis). 5. Continuous renewal of the polymer supply in the economy, practically without the use of raw materials. 6. The composition of the polymer product mixture influences only the composition of the pyrolysls gas ~02434~
without having a detrimental effect on the process. 7. The residues adhering to the high polymer waste products, as for example household chemicals, are also reacted to useful products, such as C2H2,C2H4,CO, etc.
Claims (10)
1. A process for the complete reprocessing of high polymer waste products or waste-product mixtures of any chemical composition, characterized in that the polymer waste products are converted by plasma chemical means into the chemical basic materials from which they had originally been synthesized.
2. A process as in claim 1, wherein the polymer waste products are subjected to a plasma pyrolysis under reducing conditions
3. A process as in claim 1, wherein the polymer waste products are subjected to a plasma gasification at the simultaneous presence of reducing and oxidizing plasma conditions.
4. A process as in claim 1, wherein the crushed or granulated polymer waste products are converted into a conveyable consistency, the conveyable polymer waste products are mixed with superheated steam and fed to a hydrogen plasma jet having an average mass temperature of at least 1000°C and a pressure of 0.05 to 0.5 MPa and are distributed therein, the residence time of the polymer waste products in the plasma is selected corresponding to their chemical composition and the physical state of the polymer waste products fed to the plasma jet, for example particle size, but it is preferably in the range of 10-3 second to 30 seconds, the plasma jet is quenched on completion of the reaction to temperatures below 1000°C and is converted into a pyrolysis gas current and the solids present in the plasma pyrolysis gas current, such as carbonized polymer waste products or carbon black, are removed from the plasma pyrolysis gas and the plasma pyrolysis gas is entirely or partially separated into its constituents.
5. A process as in claim 4, wherein the crushed or granulated polymer waste products are thermally melted down, preferably by means of an extruder, and thus converted into a conveyable consistency.
6. A process in claim 4, wherein the crushed and granulated polymer waste products are converted into a conveyable consistency by mixing them with a solvent or solvent mixtures.
7. A process as in claim 4, wherein the crushed and granulated polymer waste products, are converted into a conveyable consistency by mixing them with water.
8. A process as in claim 4, wherein the crushed and granulated polymer waste products are fed into the plasma reactor by means of hot steam, hydrogen, methane CO2 or fuel gas as entraining gas.
9. A process as in claim 4, wherein the complete or partial separation of the plasma pyrolysis gas into its constituents is carried out by means of absorption or low temperature distillation.
10. A process as in the claims 4 and 9, wherein after the complete or partial separation of the pyrolysis gas into its constituents said constitutents are passed to corresponding polymer synthesis processes, either entirely or partially.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2024340 CA2024340A1 (en) | 1990-08-30 | 1990-08-30 | Process for the complete reprocessing of high polymer waste products |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2024340 CA2024340A1 (en) | 1990-08-30 | 1990-08-30 | Process for the complete reprocessing of high polymer waste products |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2024340A1 true CA2024340A1 (en) | 1992-03-01 |
Family
ID=4145853
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2024340 Abandoned CA2024340A1 (en) | 1990-08-30 | 1990-08-30 | Process for the complete reprocessing of high polymer waste products |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2024340A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2018085934A1 (en) * | 2016-11-09 | 2018-05-17 | Handa, Janak H. | System and process for converting plastic waste to oil products |
-
1990
- 1990-08-30 CA CA 2024340 patent/CA2024340A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2018085934A1 (en) * | 2016-11-09 | 2018-05-17 | Handa, Janak H. | System and process for converting plastic waste to oil products |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP3126735B2 (en) | Controlled catalytic and thermal sequential pyrolysis and hydrolysis of mixed polymer waste streams for sequential recovery of monomers or other high value products | |
| Kaminsky | Thermal recycling of polymers | |
| KR100293752B1 (en) | Method for treating waste or waste plastic material | |
| Aguado et al. | Feedstock recycling of plastic wastes | |
| Valerio et al. | Strategies for polymer to polymer recycling from waste: Current trends and opportunities for improving the circular economy of polymers in South America | |
| Kaminsky et al. | New pathways in plastics recycling | |
| Kaminsky | Recycling of polymers by pyrolysis | |
| EP0574171B1 (en) | Partial oxidation of scrap rubber tires and used motor oil | |
| US5055167A (en) | Method for the complete utilization of high polymer waste products | |
| KR100308464B1 (en) | Method for producing synthesis gas | |
| EP0641366A4 (en) | Improved poly ethylene terephthalate decontamination. | |
| JPH11140224A (en) | Treatment of waste thermosetting plastic | |
| Miller | Industry invests in reusing plastics | |
| CA2024340A1 (en) | Process for the complete reprocessing of high polymer waste products | |
| Meszaros | Advanced recycling technologies for plastics | |
| EP0249748B1 (en) | Process for the destructive hydrogenation of carbon-containing wastes in a fluidized bed | |
| Thakur | Recycled Polymers: Chemistry and Processing, Volume 1 | |
| NO177753B (en) | Process for full utilization of high polymer waste products | |
| EP1603861B1 (en) | A method for the decontamination of polyethylene terephthalate | |
| EP1038909A1 (en) | Mathod for the recycling of rubber | |
| KR200256293Y1 (en) | Oil creation device | |
| Sponchioni et al. | Poly (methyl methacrylate): Market trends and recycling | |
| JPH0496943A (en) | Method for full utilization of high polymer | |
| Esfandian et al. | Chemical Recycling of Plastic Waste | |
| Barla et al. | 10 Potential Use of Subcritical Water Technology in Polymer Fibers Recycling |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |