Effects of biomass type, blend composition, and co-pyrolysis temperature on hybrid coal quality

An experimental study on co-pyrolysis of coal with biomass wastes to produce hybrid coal was conducted to investigate the effects of important process variables, namely biomass type (rice husk and sawdust), blend composition, and co-pyrolysis temperature on the quality of hybrid coal. The experiments were carried out using a vertical tubular furnace equipped with temperature controller to maintain the co-pyrolysis reactor at a given temperature. Nitrogen gas was introduced into the furnace to create an inert environment preventing the sample from burning. A known mass of solid sample consisting of manually granulated blend of coal and biomass with binder in spherical shape was contained in a basket made of stainless sieve. After a given residence time, the sample was taken from the furnace. The blend sample prior to experiment and the produced hybrid coal were then characterized for its proximate analysis, ultimate analysis and calorific value. Experimental findings suggested that by increasing co-pyrolysis temperature from 200 to 400 °C, the calorific value of hybrid coal will increase by 14.5-17.7% to be 5585-7060 kcal/kg. It was also showed that 30% increase in the biomass content in the fuel blend would produce a hybrid coal that emitting up to 25.9% less in CO2 when used for combustion, although its calorific value decreased down to 8% compared to the biomass blend. It is shown that hybrid coal obtained from this study is comparable in calorific value to bituminous coal, thus suitable for power plant while being more environmentally friendly.