Microwave Pyrolysis of Biomass: Control of Process Parameters for High Pyrolysis Oil Yields and Enhanced Oil Quality

Abstract

The oil yield and quality of pyrolysis oil from microwave heating of biomass was established by studying the behaviour of Larch in microwave processing. This is the first study in biomass pyrolysis to use a microwave processing technique and methodology that is fundamentally scalable, from which the basis of design for a continuous processing system can be derived to maximise oil yield and quality. It is shown systematically that sample size is a vital parameter that has been overlooked by previous work in this field. When sample size is controlled the liquid product yield is comparable to conventional pyrolysis, and can be achieved at an energy input of around 600 kWh/t. The quality of the liquid product is significantly improved compared to conventional pyrolysis processes, which results from the very rapid heating and quenching that can be achieved with microwave processing. The yields of Levoglucosan and phenolic compounds were found to be an order of magnitude higher in microwave pyrolysis when compared with conventional fast pyrolysis. Geometry is a key consideration for the development of a process at scale, and the opportunities and challenges for scale-up are discussed within this paper.

Microwave pyrolysis of biomass for bio-oil production: Scalable processing concepts

“…This compares well with the energy requirements reported for microwave pyrolysis of woodchips in a fixed bed (0.6-0.7 kWh/kgbiomass) in order to pyrolyse to a level comparable with conventional pyrolysis [92], although avoiding thermal runaway effects.…”

The application of microwave heating in bioenergy: A review on the microwave pre-treatment and upgrading technologies for biomass

“…MW heating is dependent on the interaction of electromagnetic energy with biomass, and the ability of the material to absorb and convert this energy into heat [176]. There is clearly a lack of fundamental data on the dielectric properties of biomass and its individual constituents, however it is vital that such parameters are studied and understood in order to understand the heating behaviour and thermal gradients that can exist within different systems [177].…”

“…50°C. It is known that the dielectric properties of biomass change nonlinearly with temperature [183], however only a limited number of studies have determined the dielectric properties of biomass at elevated temperatures (within the 100°C -900°C temperature range) [176,185,186,188,189]. Considering that the pre-treatment of biomass may require temperatures that exceed 100°C (for example biomass torrefaction requiring temperatures up to 300°C), further work is required to determine the dielectric responses of different biomass feedstocks at higher temperatures.…”

Microwave pyrolysis of lignocellulosic biomass––a contribution to power Africa

“…The bio-oil analysis showed mixtures of phenolic, aromatic hydrocarbons, cyclopentanones, carboxylic acids, ketones, and furan derivatives. In addition, it demonstrates that the yield and quality of bio-oil are dependent on key parameters such as micro wave power, biomass particle size/composition, and type of susceptor [135] Larch Experiment was carried out using a fundamentally designed scalable microwave system maximize pyrolysis oil yield and quality.…”