Investigation of Lignite and Firewood Co-combustion in a Furnace for Tobacco Curing Application

Co-combustion of lignite and firewood was investigated for an application in tobacco curing industry in Northern Thailand. Extensive experiments have been carried out in a newly developed furnace suitable for small curing unit, in place of locally made furnace. The aim of this investigation is to evaluate the performance of the combustion chamber in the required thermal output range for tobacco curing and to examine the influence of fuel feed rate, fuel mixture ratio and air staging on the combustion and emission characteristics of the furnace during steady state operation. Their effects are characterized in terms of the observed variations of temperature distributions, emissions of CO, SO₂, CO₂, O₂ and combustion efficiency. Co-firing of firewood and lignite has been found to exhibit acceptable temperature distribution, high combustion efficiency and low emissions over a wide thermal output span. Stable operation at low (50 kW) and high (150 kW) thermal output was achieved with average CO and SO₂ content in flue gas typically below 1400 and 100 ppm, respectively. Under the conditions considered, it was showed that the fuel feed rate had greater influence on combustion and emissions than firewood and lignite mixture ratio and air staging.