Experimental Study of Ignition and Combustion Characteristics of Mixed Rice Straw and Sewage Sludge Solid and Hollow Spherical Pellets in a Plasma Combustion System

In this work, the ignition and combustion characteristics of mixed rice straw and sewage sludge pellets in air atmosphere were investigated using a plasma combustion system. One common pellet shape (solid spherical pellet) and another new shape (hollow spherical) are used in this study. High-speed camera was used to record and observe ignition and combustion process of pellets. In case of hollow pellets, the shape and distribution of flame are found to be better compared to solid pellets. Also, it is clear that the values of volatile combustion times in case of hollow pellets are low compared to solid pellets. The overall heat transfer enhanced in case of hollow pellet due to the large area subjected to hot gases and the high surface to volume ratio. Hollow pellet consumed less time for internal ignition and volatiles char combustion compared to solid pellet. Volatiles and char combustion lasted for 63.05 and 61 s, respectively for hollow pellet while these values were found to be 72.8 and 83 s, respectively for solid pellet.