Modelling and experimental studies of biomass and organic pyrolysis

Pyrolysis is a thermal conversion process that decomposes organic materials into liquid hydrocarbons, carbonaceous residues and combustible gases in the absence of oxygen. Depending on the process conditions and the type of feedstocks, the yield distribution among the three categories of products and their constituents can vary a lot. Therefore, an analysis on the feedstock pyrolysis characteristic and the impacts of process parameters on pyrolysis outcomes can greatly assist in the designing, operating and optimizing of pyrolysis processes. This research aims to utilize both experimental and modelling approaches to perform the analysis on some biomass and organic feedstocks such as wood, bamboo, common plastics and tyre, and to provide insights for the design and operation of pyrolysis processes. In the experimental study, the effects of heating rate, final pyrolysis temperature, sample size, pyrolysis time and feedstock shrinkage are investigated using common thermal analysis techniques and a bench-scale pyrolysis unit. A mathematical model that integrates the feedstock characteristic from the experimental study was built to simulate the pyrolysis progress of multiple feedstock particles in a pyrolysis reactor. The model composes of several sub-models that describe pyrolysis kinetic and heat flow, particle heat transfer, particle shrinking and reactor operation. It forms the basis for the discussion on the considerations of and interrelation between processing conditions, feedstock size, pyrolysis energy usage, processing time, product quality and secondary reaction for the design and operation of pyrolysis processes. Apart from studying on some general considerations for the design and operation of pyrolysis process, the model was also used to demonstrate and evaluate on two multi-stage pyrolysis operation strategies – adiabatic stage pyrolysis and fractional pyrolysis. These operation strategies are shown to help minimize the energy usage, maximize certain product fractions, enhance processing efficiency and provide a better separation of products