Modelling and experimental studies of municipal green waste pyrolysis

Pyrolysis of biomass feedstock has attracted an increased interest in renewable energy sector. The product of pyrolysis process such as oil, gas and charcoal possess significant thermodynamic properties for heat and power generation. Studies suggest that Municipal Green Waste (MGW) has acceptable characteristics with a calorific value of 19 MJ/kg, which can be considered a significant source of feedstock to produce bio-oil. This study focuses on an efficient way of producing bio-oil from municipal green waste through pyrolysis process using a fluidized bed reactor. A 5-6 kg sample of municipal green waste was pyrolysed in a short sealed rotary furnace which had an off gas condenser to produce charcoal and condensate products. The condensate was further processed in-situ using a centrifuge to produce organic or bio-oil products. It was found from the experiment that about 20% bio-oil, 40.8% biochar and 29.8% syn-gas can be obtained from MGW. Process flow diagram has been produced for the integrated system. A four-stage steady state simulation model has been developed for process simulation using ASPEN Plus. In the first stage moisture content of the green waste feedstock was reduced. In the second stage biomass was decomposed according to its elemental decompositions. In the third stage, volatile matter and non-volatile components were separated. Then in the fourth stage, pyrolysis reactions have been modelled using gibbs free energy minimization approach. Ultimate and proximate analysis data from experimental investigations were used in ASPEN simulation. The simulation results were then compared with the experimental results and a good agreement between them were found. In particular, the variation of basic elemental mass percentage for C was 7.3 %, for H2 was 15.82 %, for N2 was 7.04 % and for S was 5.56 %.