PYROLYSIS PROCESS STUDIES FOR POST CONSUMER POLYETHENE WASTE CONVERSION AND UPGRADING OF THE PYROLYSIS OIL

Abstract

Pyrolysis is a waste to energy conversion technology that operates in oxygen free environments. Pyrolysis can be applied in the sustainable management of plastic wastes through conversion to liquid and gas fuels which are  chemically  similar  to  fossil  fuels.  This  study  was  carried  out  to  implement  a  suitable  and  cost -effective recycling technology that will help solve severe pollution problems resulting from poor management of waste plastics  in  urban  and  rural  set-ups  in  Kenya.  The  paper  aims  to  conduct  pyrolysis  process  studies  for  postconsumer  polyethene  waste  conversion  and  characterization  of  the  resultant  liquid  products.  This  was conducted in a locally assembled pyrolysis reactor at temperatures ranging between 200 to 350 °C for periods 1 to 2 hours. Low Density Polythene (LDPE), High Density polythene (HDPE) and Polypropylene (PP) were used in  the  experiments.  Plastic  waste  materials  were  collected  from  the  open  dumpsites,  washed,  sun -dried, sorted out according to resin codes, sliced and pelletized in to small pieces of dimensions of 2 mm. The samples
were  feed  in  the  preheated  reactor  for  conversion  and  the  liquid  collected  in  glass  jars.  Fractionation  was conducted  to  partition  the  crude  into  petrol  at  150oC  and  diesel  at  350 oC.  HDPE,  LDPE  and  PP  produced 720±1.64, 696.07±1.67 and 602.08±2.01 ml of crude oil for 1 kg of wastes respectively. Diesel yield was 72%, 70% and 60% for HDPE, LDPE and PP respectively while petrol was 6%, 8% and 6% respectively. HDPE, LDPE and PP produced 1 %, 5 % and 1 % of solid residue respectively. The results showed that over 90% conversion of plastic waste into fuel products is achievable through pyrolysis process.

Key words: Pyrolysis, waste to energy, LDPE, HDPE, PP