Mixed plastic waste processes

An account is given of the chemical recycling activities of BASF in a pilot plant at Ludwigshafen in Germany, where mixed plastics waste is processed to obtain hydrochloric acid, oil, gas, naphtha, aromatics and alpha-olefins. 

MeLean, Va., 3rd-4th June 1993, p.189-200. 8(13) GASIFICATION PROCESS FOR MIXED PLASTICS WASTE Simons en K Texaeo Ine. 

It is generally known that to obtain pure fractions from a mixture of different plastics is a more expensive process than separation of simple clean polymers, in plant. Therefore, it is anticipated that the separation of a municipal mixed plastic waste should be the most challenging. In such a fraction, traces of foods, labels, dirt (size mm), solvents (alcohols, petrol etc.), metals, low molecular weight products of different origins etc. could be found. Some of the sorting methods used are listed in Table 1. 

The detailed analysis of the derived oil/wax and gas products from the pyrolysis of plastics in relation to process conditions and different types of plastic is essential in providing data for the assessment of the feedstock recycling process. In addition, the yields and composition of gases and oils from the pyrolysis of mixed plastic waste are important in assessment of the process and to determine the possibility of any interactions between the plastics during pyrolysis. 

The research on the liquefaction of waste polymers and the coprocessing of waste plastics with vacuum residue or coal has been a subject of study by many groups at universities and environmental agencies. A significant amount of effort and funds are being diverted to develop process technology in order to convert mixed plastics waste from municipal... 

This section deals with the economic evaluation of the conversion of mixed plastics waste (MPW) into synthetic crude (syncrude) oil and coprocessing of MWP with vacuum residue into syncrude. In their feasibility study, Ali and co-workers considered the process technology developed by Veba Oel AG of Germany the Veba Combi-Cracking (VCC) option for the processing of MPW [31], The process data and economic data were taken mainly from Dijkema and Stougie [32] and Huffman and Shah [33] for this study. All the cost data were translated to represent the economic analysis for Saudi Arabian conditions. 

G. P. J. Dijkema, and L. Stougie, Environment and Economic Analysis of the Veba Oel Option for the Processing of Mixed Plastic Waste , Interduct, Rotterdamseweg 145, 2628 AL Delft, The Netherlands (1990). 

Mad ar and M. Juriga, A new method of the organic waste treatment concerning waste oil, mixed plastics waste, oil sludge and PCBs waste processing with simultaneous recovery of hydrocarbons . Petroleum and Coal, 45 (3-4), 187 (2003). 

MPW = mixed plastic waste MSW = municipal sohd waste ASR = auto shredded residue BFB = bubbling fluidized bed CFB = circulating fluidized bed. Rows in itaUcs are related to fluidized-bed processes. Data have been mainly obtained from [9, 20-24]... 

Some of the procedures of value for processing of mixed plastic wastes may also be useful for the recovery of value from the laminates used for efficient packaging of food and beverages (e.g., milk cartons, Tetrapaks). A combination of heat and pressure may be employed on a recycle stream of this type of material to fuse the mixed fibrous and resin components into a dense board-like product [31, 32]. This highly weather and insect resistant product, Eco Superwood Plastic Lumber, may be sawn, nailed, drilled, etc., like wood, and it resists rotting in direct contact with the soil without the need for preservatives. 

Only a small number of the investigations summarized in this review addresses the obvious practical concern of mixed plastics waste. Higher performance products with multiple polymeric layers, the use of additives, fillers and colorants, and the expense of sorting individual polymers for subsequent processing all demand resource recovery strategies capable of handling a complex mixture of... 

Vezzoli, A., Beretta, C. A., and Lamperti, M. 1993. Processing of mixed plastic waste, In Recycling of Plastic Materials, F. P. La Mantia, ed., pp. 219-36. ChemTec Pubhshing, Toronto-Scarborough, Canada. 

From mixed plastics, the formation of ethene, methane and hydrogen increase with temperature but the formation of propene and higher hydrocarbons decreases. Whether the isolation of olefins can compete economically with the oil cracking process remains to be seen, but the total hydrocarbon pyrolysate is similar to naphtha, the feedstock for petrochemicals production. It should be noted that because pyrolysis is primarily a non-oxidative process carried out under carefully controlled conditions, the possibility of dioxin formation is much reduced. In 1995 about 100 kT of mixed plastics wastes were converted into chemical feedstocks in Europe by pyrolysis, and this is expected to increase at the expense of incineration over the next ten years. 

Due to its sensitivity to contamination from other polymers and from impurities, solvolysis will most likely find application within well-defined product areas with efficient collection and sorting infirastructures. Thermolysis, on the other hand, shows high potential for treating mixed plastics waste such as municipal solid waste and automotive shredder residue which otherwise would go to landfill. Not all thermolytic processes are suited for the generation of new polymers, and a certain amount of the oils, gases and solid residues from these processes is used to replace fuel. 

Mechanism of pyrolytic degradation is complex involving a large set of reactions, even for a single class of plastic. Generic degradation reactions such as chain scission, H-transfer, unzipping, disproportionation, and combination occur in the process. Typical mix of products from mixed plastic waste streams with different pyrolysis conditions are shown in Table 9.3. 

Dijkema GPJ, Stougie L. Environmental and Economic Analysis of Veba Oel Option for Processing of Mixed Plastic Waste. Delft DeUt University Clean Technology Institute 1994. 

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