AbstractsBiology & Animal Science

Pyrolysis of biomass is the thermochemical conversion process whereby the long lignocellulosic polymers in biomass are cracked into several higher-value products such as bio-oil, bio-char and combustible non-condensable gases (NCG). Fast pyrolysis in particular is aimed at maximising the yield of crude liquid bio-oil, with the production of bio-char and NCG as co-products. Since a large quantity of under-utilised biomass is produced in the forestry sector annually, as by-product from harvesting, this sector has shown particular interest in this process. Furthermore, the continuing drive for renewable and sustainable energy production, particularly of drop-in liquid biofuels, has urged the development of such technology on a commercial scale. The main purpose of this investigation was to evaluate the technical feasibility and performance of the scalable dual fluidised bed (DFB) reactor system designed and constructed at the University of Pretoria by Swart in 2012. The sub-objectives of this study were as follows: • Biomass pre-treatment equipment was implemented to ensure that the physical characteristics of the biomass feedstock meet the pyrolysis process requirements. • The scalable DFB reactor system, including all sub-systems and ancillary equipment, was commissioned to ensure satisfactory operation of the complete system. • Continuous, steady-state experimental runs were conducted to produce fast pyrolysis products in the scalable DFB reactor system. • The fast pyrolysis products were quantified and characterised to evaluate the technical feasibility of the DFB reactor system. • A material and energy balance was conducted over the pyrolysis fluidised bed (PFB) reactor to quantify its performance. Eucalyptus grandis raw material, as received from Sappi Southern Africa’s Ngodwana mill, was successfully converted to bio-oil, bio-char and NCG in the scalable DFB reactor system. Fast pyrolysis was conducted at a pyrolysis temperature of 500 °C, a vapour residence time of 4 s and a sawdust feed rate of 2.0 kg/h. The PFB reactor temperature could be controlled easily, at the desired setpoint (500 °C), by continuously circulating hot solids between the two bubbling fluidised beds. The excellent temperature control of the PFB reactor makes the DFB system a suitable reactor system for the fast pyrolysis of biomass on a commercial scale. At these PFB reactor conditions the yield of fast pyrolysis products, on a dry feedstock basis, was determined as 36.3, 14.0 and 49.7 weight % for bio-oil, NCG and bio-char respectively. High-value process heat, in the form of hot flue gas (450–500 °C), was produced in the combustion fluidised bed Although the crude liquid bio-oil contained highly oxygenated compounds (including organic acids, water, alcohols, esters, sugars, aldehydes, ketones, furans, pyrans and phenolics) it may be utilised for heat generation when co-fired with conventional fossil fuels, including heavy furnace oil. However, the scalable DFB reactor system allows for integrated catalytic fast…