Pyrolysis process is the thermal decomposition of carbonaceous materials in the absence of oxygen into carbonaceous residues, liquid hydrocarbons and combustible gases. It is a precursor to other thermochemical processes (gasification and combustion) and therefore very important thermochemical process. Pyrolysis process is an efficient and effective method of treating solid wastes but its large-scale utilization is still limited by certain factors. The major factor is the high amount of energy used during the pyrolysis process and in order to make pyrolysis a cost effective commercial energy process, there is need to explore different approaches/strategies to reduce energy usage during the process. Another important challenges with pyrolysis of solid wastes are the stability of...[ Read more ]

Pyrolysis process is the thermal decomposition of carbonaceous materials in the absence of oxygen into carbonaceous residues, liquid hydrocarbons and combustible gases. It is a precursor to other thermochemical processes (gasification and combustion) and therefore very important thermochemical process. Pyrolysis process is an efficient and effective method of treating solid wastes but its large-scale utilization is still limited by certain factors. The major factor is the high amount of energy used during the pyrolysis process and in order to make pyrolysis a cost effective commercial energy process, there is need to explore different approaches/strategies to reduce energy usage during the process. Another important challenges with pyrolysis of solid wastes are the stability of certain products fraction and composition of the solid waste feedstocks. Therefore, in this study, experimental, modelling and optimisation of solid wastes pyrolysis were investigated and different operational strategies were proposed towards solving the pyrolysis problem. Selected solid wastes feedstocks such as bamboo waste, waste tyres, sawdust, empty fruit bunch (EFB) and plastics (polystyrene and high density polyethylene) were employed in this research study.

In the experimental study, common thermal analysis techniques and laboratory scaled pyrolysis unit were used to study the influence of particle size, pyrolysis temperature and heating rates on selected solid wastes feedstocks. A mathematical model was developed in MATLAB using the parameters generated from the experimental study. This model describes transiently the pyrolysis progress of particles subjected to specified pyrolysis conditions in a pyrolysis reactor. The effect of the operating parameters on the pyrolysis progress was studied using the model and some experiments were conducted to validate the model results. In addition to the pyrolysis model, selected operating conditions were optimised with focus on minimizing energy input for the pyrolysis reaction. The constraints and optimisation equations depend on the operating strategy under consideration.

Therefore in this present study, three operational strategies to reduce the energy usage during the pyrolysis of solid wastes were proposed. The operational strategies are operating parameters studies and optimisation including mixed-size approach, multi-stage pyrolysis and optimisation and co-pyrolysis/mixed-waste pyrolysis. The results and the design of the various approaches are clearly stated in this thesis. These operational strategies were shown to minimize the energy usage, improve the pyrolysis products quality, enhance the pyrolysis process efficiency and can further help in designing the operation of pyrolysis process in a large scale. Overall, the application of some or all the proposed strategies will help to make pyrolysis of solid wastes more energy efficient and more profitable on a large scale.