A new take on
A new boiler technology, the Rotary Cascading Bed Combustion (RCBC) system, that cleanly and efficiently converts high sulfur coals, waste coals, refuse-derived fuels (RFD), shredded tires and industrial and municipal wastes to energy has been extensively tested at North American Rayon Corporation in Elizabethton, Tennessee. This technology is the mechanical equivalent of large fluidized bed combustors being developed for utilities. In operation, fuel is fed into a cylindrical combustion chamber and is mixed with limestone, which limits the formation of acidic sulfur dioxide (SO2) emissions. Due to combustion temperatures that range between 1600-1650 degrees F far lower than conventional steam generating systems, nitrogen oxide (NOx) emissions are also reduced.
The Center for Electric Power at Tennessee Technological University developed a comprehensive program to evaluate the overall performance of the system and to review test data. This evaluation was sponsored by the Tennessee Department of Economic and Community Development Energy Division and the Appalachian Regional Commission.
To illustrate the ability of the RCBC to burn a wide variety of fuels with emissions well below EPA limits, a few test results are presented. While burning high sulfur/high ash Tennessee coal with an average ash content of 26.3 percent, the RCBC yielded average emissions of .96 Ibm/MMBtu of SO2 and .50 Ibm/MMBtu of N0x. In test burns of RDF containing .44 percent sulfur and 9.46 percent ash, average emissions were .22 IbmfMMBtu of SO2 and .07 lbm/MMBtu of N0x. These representative results are below those required by current Clean Air Act regulations. Similar results were obtained for over thirty burn tests using single and multiple fuels.
Based on the extensive test data collected, we believe the RCBC technology is viable and should be advanced to commercial-scale as soon as possible. Such commercial development would provide a technology not only to meet Clean Air Act requirements but also to lower energy costs for industry and offer another alternative for solid waste management.
Director of the Center for Electric Power
Tennessee Technology University