1-013 (O) Proceedings of the 2 nd Regional Conference on Energy Technology Towards a Clean Environment 12-14 February 2003, Phuket, Thailand Co-combustion of lignite and municipal solid waste in a fluidized bed: influence of air staging K. Suksankraisorn 1,2 , S. Patumsawad 1 , P. Vallikul 1 , B. Fungtammasan 1 and A. Accary 2 1. The Waste Incineration Research Center (WIRC), King Mongkut’s Institute of Technology North Bangkok, Bangkok, 10800, Thailand. 2. Laboratoire Gestion Des Risques et Environnement (GRE), Universite de Haute Alsace, Mulhouse, 68200 France. Abstract Laboratory experiments have been carried out using an 11.5-cm-diameter fluidized bed to examine the influence of air staging on the co-combustion and emission characteristics of high-sulfur Thai lignite mixed with high-moisture MSW, under different MSW/mixture fractions and excess air levels. Air staging is achieved by dividing air supply into the in-bed fluidizing primary air and the over-bed secondary air, with the degree of air staging being expressed as the ratio of secondary to total air. Its effects are characterized by the observed variations of temperature distributions, combustion efficiency, and emissions of CO, CO 2 , SO 2 , NO and N 2 O. The results show that air staging alters the combustion regime and the temperature distributions significantly. It gives rise to enhanced combustion immediately above the secondary-air injection port, with increased temperature in the dense bed and reduced temperature in the freeboard. Combustion efficiency is only slightly affected. The emission of CO increases with increasing proportion of secondary air due to reduced in-bed excess air and the increase is dependent on the mass fraction of the waste. SO 2 emission increases significantly with increasing proportion of secondary air, probably due to enhanced oxidation of H 2 S to SO 2 in the splash zone. The emission of NO, irrespective of the waste fraction, is reduced remarkably with increasing proportion of secondary air because of the increasingly fuel-rich condition in the dense-bed. A slight decrease in N 2 O is also seen with increasing secondary air due to increased in-bed temperature and reduced NO. Keywords Fluidized bed, co-combustion, lignite, solid waste, air staging Introduction In recent years, co-combustion of a conventional fuel such as coal or lignite, with an alternate or “opportunity” fuel like biomass or municipal solid waste (MSW) has been increasingly recognized as an effective means for reducing the emissions of some of the pollutants resulting from the burning of the conventional fuel and for the disposal of waste materials with energy recovery [1-2]. The approach is particularly attractive where the conventional fuel concerned contains high sulfur, as co-firing with a low-sulfur alternate fuel improves sulfur retention and reduces SO 2 emission remarkably, without undue increase in CO or NO emissions [3-4]. From the point of view of waste incineration, co-combustion is also advantageous because the more reactive coal augments the combustion of waste with inferior fuel properties, such as that with high moisture and low calorific value.