Characteristics of Co-combustion of Low-Rank Coal with Biomass

The fundamentals of ignition, NO x (NO and N 2 O) emissions, and ash formation characteristics for biomass and mixtures of coal with biomass are precisely elucidated in this study. In this study, biomass, coal, and a biomass−coal mixture are burned, using an electrically heated drop tube furnace. In the combustion test, the focus is on the ignition behavior, combustion efficiency, NO x emission behavior, and formation characteristics of particulate matter, based on the results of gas compositions along the furnace axis and a collection of particulate matter by a low-pressure impactor. As a result, the addition of biomass into low-rank coal affects combustion behavior, especially for ignition enhancement. The NO and N 2 O concentrations in co-combustion are almost the same as those in coal combustion, even if the quantity of input fuel nitrogen under the co-combustion condition is half of that under the coal combustion conditions. A kinetic simulation of the NO and N 2 O behavior results is conducted, using the homogeneous reaction schemes at constant temperature. The simulation result of NO concentration agrees with the experimental result obtained. However, the N 2 O concentration calculated is less than the experimental result, because the heterogeneous schemes that are related to N 2 O are not considered in this simulation. Fine particulates with a size of <2 μm during biomass combustion are produced. Burning the biomass with coal shifts the particle size distribution from fine particles to coarse particles, which can be captured by dust collection systems.