 This boiler burns wood chips, derived from the waste of demolished frame houses, together with coal. Nowadays in Japan, there is a tendency to utilize wastes as fuel to reduce impacts on the environment and to save energy costs. When using wastes, emission pollutants such as CO, NOx, dioxins, particles and SOx must be reduced. MHI applied a newly developed combustion method (called M-Star*) to meet the strict emission regulations. The CO, NOx, dioxins control combustion method, based on the optimization of air feed to the combustor, is adopted. The air is divided into four stages, which are primary air, OFA (over fire air), L-AA (lower additional air), and U-AA (upper additional air). The region from the fluidized bed up to L-AA is used as a reducing zone for control of NOx emissions. The gas temperature then rises with the L-AA and U-AA injection for CO and dioxin reduction. In addition, a bag filter with active coal injection system for particles and dioxins reduction and a magnesium desulfurization system for SOx reduction are installed. During the performance test, it was confirmed that emissions were held to very low levels. [Overview of the plant]
*)M-Star : Mitsubishi Multi-Stage Air Re-firing (Patent) |
