Unsteady heating of coal particles before ignition

TLDR: In this article, a novel method for analyzing the heating of coal particles in a coal powder-laden jet in the near-burner region is proposed, taking into account both the time delay due to coal particle unsteady heating and the induction period needed for the coal particle to ignite from the practical engineering point of view.

Abstract: 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 account both the time delay due to coal particle unsteady heating and the induction period needed for the coal particle to ignite from the practical engineering point of view. A review of the flow and heating of coal particles is presented. The principle and analysis procedures for estimating the ignition heat and the heat balance are outlined. The advantage of the proposed method over the previous analyzing method which is based on the steady-state heat balance is also discussed. The influencing trends of various factors on the results are calculated and drawn in a group of diagrams. The calculating procedure is demonstrated by using an industrial swirl burner as data source. The predicted hot gases recirculating ratio is in general agreement with the measurements on the physical model. This study offers a useful reference in engineering practice for improving burner design and performance.