Experimental Study On The Biomass Combustion Character In Stoker-Fired Boiler

Along with the lack of energy source and the environment depravation, our country has been faced with a series economy and environment problems, the researchers begin to think much of the utilization of biomass. Grate combustion is an important means. Biomass combustion in stoker-fired boiler is an important way to reconstruct small power plant unit and grate furnace, the research of biomass combustion characteristic in stoker-fired boiler has important industry sense.The combustion characteristic of different type biomass fuel is researched from microcosmic and macroscopical aspects. Thermal analysis means is used to analyze the kinetics of biomass combustion. The biomass packed bed combustion characteristic is researched in a small fixed-grate furnace, and the main factors to the combustion (fuel character. Shape and size, airflow rate) are researched too.In the experiment of thermal analysis, the process of biomass combustion is divided into 3 steps according to the logarithm method. The ignition temperature, combustion stability exponent, volatile release character exponent and combustion character exponent are used to distinguish the combustibility. The infection of heating rate, hold gas components and fuel chemistry composition are also researched. A part of released gas productions and tar are on-line examined using mass spectrometry. The apparent activation energy and preexponential factor are obtained by kinetic analysis. The combustion process is simulated by mathematical means.The main factors that can influence the packed bed combustion character are analyzed in the biomass combustion experiment in the small fixed-grate furnace. The furnace can be used to simulate grate combustion, room combustion (suspending combustion) and air flow distribution experiment.In the experiment, the ignition front velocity, ignition front temperature and gas components above the fuel bed are used to distinguish grate combustion characteristic in different conditions. The influence as followings:⑴the smaller fuel particle need longer time to combust completely, the fuel bed temperature is higher and combustion stability is better;⑵the biomass pellet has higher energy density and uniformity, combustion stability is better, it is suitable to grate combustion. The cut biomass is easy to be blow out , it is suitable to room combustion or suspending combustion;⑶the complete combustion need different time for different type biomass fuel, the more volatile the biomass has the fewer time it burns out, the more ash the biomass has the worse combustion stability. Because of the high volatile content of biomass, the intensive combustion zone is in the forward, the airflow distribution should be chosen according to the fuel type;⑷because the biomass is easy to be ignited and burned out, the excess air ratio should not be high.