Unsteady heating of coal particles before ignition

A novel method for analyzing the heating of coal particles in a coal powder -laden jet in the near-burner region is proposed. This method takes into ac count both the rime delay due to coal particle unsteady heating and the ind uction period needed for the coal particle to ignite from the practical eng ineering point of view. A review of the flow and heating of coal particles is presented. The principle and analysis procedures for estimating the igni tion heat and the heat balance are outlined. The advantage of the proposed method over the previous analyzing method which is based on the steady-stat e heat balance is also discussed. The influencing trends of various factors on the results are calculated and drawn in a group of diagrams. The calcul ating procedure is demonstrated hy using an industrial swirl burner as data source. The predicted hot gases recirculating ratio is in general agreemen t with the measurements on the physical model. This study offers a useful r eference in engineering practice for improving burner design and performanc e.