الفهرس 
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Abstract
In Egypt there is abundance of agriculture byproducts and residues that is still provoking environmental problems, in particular, rice straw. Utilizing of biomass for energy production alleviates the growing waste disposal problems and preserves the diminishing conventional fossil fuels.The present work is dedicated to investigate the combustion characteristics of agriculture waste in a bubbling fluidized bed as well as the rate of heat energy produced. Rice straw has been selected as a case of study because it still creates the worst environmental issue. Rice straw has been prepared as pellets of diameter 12 mm and length 15 mm by virtue of chopping and compression processes. The bulk density of the pellets is about 0.73 g/cm3. The rice straw pellets have been burnt in an atmospheric bubbling fluidized furnace of diameter 300 mm and height 3300 mm. The experiments have been carried out under steady state conditions and by means of overbed fuel feeding system. Experimental results demonstrate that combustion of rice straw in fluidized bed is successfully achieved with high efficiency. Post combustion of volatile over bed is evident that results in a peak temperature in freeboard. This may be due to the escape of the unburnt volatile matter from the fluid bed. The peak temperature degree and location are sensitive to the operating parameters, especially fluidization velocity and excess air. The NOx level is relatively low ranging from 175 to 270 ppm. The obtained results show that at high level of the studied operating parameters (fluidization velocity, bed height, bed temperature and excess air), NOx emission increases with different degrees. The results also indicate that fluidization velocity has the highest impact on carbon loss and combustion efficiency. The most important results achieved in this research: 1. A simple technique has been utilized to convert rice straw into form of pellets which is suitable for feeding and burning. The pellets have a bulk density, at least, 10 times more compared to its primary state. 2. A considerable amount of heat is released in the freeboard zone due to the postcombustion of volatiles. The peak temperature occurs in the freeboard zone. Its degree and location are dependent on operating conditions. 3. Burning of rice straw has been realized with combustion efficiency above 96% over a wide range of operating conditions. Combustion efficiency is found to be improved with increasing bed height, bed temperature and excess air. 4. Fluidization velocity has a negative impact on carbon loss and combustion efficiency. 5. The NOx level is relatively low ranging from 175 to 270 ppm. The studied operating parameters (fluidization velocity, bed height, bed temperature and excess air) somewhat promote NOx emission.