Gasification of lignite in a fixed bed reactor: Influence of particle size on performance of downdraft gasifier

In this work, an experimental study of the gasification of lignite with various particle sizes was carried out in a pilot-scale (10 kWe) downdraft type fixed bed gasifier. The main objective of the study was to investigate the feasibility of the lignite as a fuel for downdraft gasifier and to evaluate the effect of the particle size on gasifier performance. The influence of the particle size on fuel consumption rate, temperature profile in various zone, gas yield, gas composition and cold gas efficiency was studied. Six different particle sizes viz. 13-16 mm, 16-19 mm, 19-22 mm, 22-25 mm, 25-28 mm, 28-31 mm were selected for experimental work. With the increase in particle size, the reduction in fuel consumption rate was observed, whereas the producer gas production rate had increased. The heating value of the gas increased as particle size increased from 13-16 mm to 22-25 mm and then same had decreased with increase in particle size. Higher temperature in reduction zone resulted in higher H2 and CO contents in producer gas. Under the experiment conditions, the fuel consumption rate, gas yields, LHV (Lower heating value) of gas fuel and cold gas efficiency varied in the range of 9.58-10.67 kg/hr, 2.43-2.63 Nm3/kg, 3.33-4.17 MJ/Nm3 and 51.5%-65.7% respectively. The experimental results showed that the gasification performance was better with lignite particle size of 22-25 mm.