الفهرس | Only 14 pages are availabe for public view |
Abstract Abstract The present study investigates the combustion of four kinds of biomass in a circulating fluidized bed (CFB) system located in Faculty of Engineering, Minia University. The aim of this study is offering the optimum experimental conditions for straw, saw dust wood, cotton seeds burs and corn stalks combustion in CFB combustor. In addition, the study investigates the effect of changing the equivalence ratio (Ô) on the temperature distribution, emissions, and heat flux inside the combustion chamber. The test rig consists mainly of the circulation system, the fuel supply system, and the air supply system. The circulation system consists of the combustion chamber, the connecting pass and the cyclone. The combustion chamber consists of the reactor and the air distributor. The reactor is a steel cylinder with 145 mm inner diameter, 2000 mm height and 12 mm thickness. The furnace is warm up by the combustion of the commercial butane gas (Butagas). Every kind of the used biomass is burned with different values of equivalence ratio. The temperatures and heat flux are measured along the reactor. The emissions of CO, NOX and SO2 are measured in mg/Nm3 in flue gases along the reactor and at the chimney. Finally, a comparative study between the combustion of the four kinds of biomass was obtained. It is concluded that there is a general stable trend of the temperature across the horizontal sections and along the combustion chamber for all used biomass except for the cotton seeds burs combustion. The admission of the first secondary air reduces the temperature for all used biomass except for the cotton seeds burs combustion. The second secondary air raises the temperature above its admission level for cotton seeds burs and corn stalks combustion. However, it has no obvious effect on temperature in case of straw and saw dust wood combustion. The highest temperature level occurs at Ô=1.24 except for corn stalks combustion where it occurs at Ô=1.4. Straw verifies the highest temperature (1080 ˚C) for all used biomass. The corn stalks combustion achieves to the highest flue gas temperature (about 350 ˚C). The maximum temperatures inside the reactor and at the chimney occur with equivalence ratio of 1.24. ˽ The maximum and minimum values of heat flux along the combustion chamber are 55 kW/m2 and 7 kW/m2 respectively. Saw dust wood produces the highest values of CO emissions (about 3000 mg/Nm3). Cotton seeds burs produce the lowest values of CO emissions (about 250 mg/Nm3). The secondary air minimizes CO and NOx emissions for all combusted biomass. SO2 emissions are under the German standard limit. The lowest values for emissions occur at Ô=1.24 equivalence ratio except for cotton seeds burs combustion where the minimum values are at Ô=1.4. |