The use of pyrolysis in the management of waste low density polyethylene water sachets
Packaged water sachets, made from low density polyethylene (LDPE), constitute a reasonable percentage of municipal solid waste. Considering the limitations of conventional methods of waste management such as land filling system and incineration on the management of LDPE, pyrolysis was adopted in handling the waste. Pyrolysis of waste packaged water sachet was carried out in a batch reactor at temperatures 200 - 400 under atmospheric pressure. A 5 kg shredded waste material was reduced to 1.10 kg, which accounted for a 79.8% waste reduction by the process. The off gases were condensed and 1.068 liters of liquid products were recovered. Fractional distillation of the liquid product yielded waxy oil (57%), gasoline (16.3%), diesel (10%) and aviation kerosene (7%). These hold similar characteristics with Nigeria National Petroleum Corporation (NNPC) specifications for the products. Pyrolysis of the waste LPDE also yielded residual solid products, which were turned into pellets. The physical and mechanical tests confirmed that the pellets qualify as coarse light weight aggregate. The pellets had low water absorption capacity of 3.3%, abrasion value of 15.6%, density of 890 kg/m3 and specific gravity in the range of 0.92 to 1.01. Pyrolysis is an effective management process for waste LPDE and at controlled conditions could yield products, which could serve as lightweight aggregate for medium to low traffic highway sub-base and surfacing.
Keywords: Pyrolysis, polyethylene, pellets, , plastics, pyro-oil, gasoline, aviation kerosene, diesel