Experimental Study on Combustion of Sunflower Shells in a Pilot Swirling Fluidized-Bed Combustor

This paper reports the experimental results from a study of burning sunflower shells in an innovative swirling fluidized-bed combustor (SFBC), using an annular spiral air distributor as the swirl generator. The combustion tests were performed for two fuel feed rates-60 and 45 kg/h while the total amount of excess air was within a range of 20%-80%. During the tests, primary air was introduced into the bed through an air distributor at the combustor bottom, while secondary air was injected tangentially into the bed splash zone, with the intention to facilitate rotational gas solid flow and also to mitigate CO in this region. For the selected operating conditions, temperature and gas concentrations (O-2, CO, CxHy as CH4, and NO) were measured along axial and radial directions in the combustor, as well as in the stack gas. As revealed by the experimental results, radial and axial temperature profiles in the SFBC were rather uniform and weakly dependent on the fuel feed rate, excess air and secondary air, whereas gas concentration profiles showed apparent effects of operating conditions in both directions. At a fuel feeding of 60 kg/h, 55% excess air seems to be an optimal value for the effective burning of sunflower shells in the SFBC, ensuring the highest combustion efficiency (similar to 99%) and acceptable levels of CO and NO emissions, both complying with the local emission standards, while maintaining CxHy emissions at a reasonable level.