Experimental Investigation On The Factors And Mechanism Of Coal Ash Slagging On Tipical Refractories In A Sintering Muffle

PC-fired boilers in power plants in China have been firing low rank coals and the fired coal will be further degraded in the future. For the purpose of improving the ignition and combustion efficiency, insulating refractory laid on furnace waterwall is adopted almost by all low rank coal fired boilers at home and abroad. The insulating refractory can improve the combustion obviously, but it can lead to another problem——slagging, which has been embarrassing the design and operation of the boilers. In order to understand the mechanism of coal ash deposition on refractory and the subsequent behaviors, the effects of thermophysical factors on the deposition, penetration and slagging of coal ashes, a new static sintering method used to investigate the deposition, penetration and slagging was proposed and applied.The sintering experiments of coal ash/refractory board were conducted as respect to SiC-based and corundum-based refractory and ashes of coal sampled from different power plants in Hunan province, the concrete experimental procedures include: spread coal ash loosely on refractory board so as to constitute pairs of coal ash/refractory board; sinter the pairs in a muffle under different temperatures, duration time and atmosphere, etc.; analyze the naturally cooled samples of coal ash(or slagging) and refractory board by XRD, SEM and EDS. On the basis, the mechanism and factors influencing the slagging on the board were totally analyzed and thereby the theory for research of slagging-resistant refractory is established.The concept of a critical temperature, at which coal ash slagging on refractory happens, was proposed and a trial-and-error based sintering method was also proposed. In order to evaluate the strength of the sintered coal slagging on refractory board and thereby determine the critical temperature, the visual, vibrating and XRD-based methods were proposed and used. The results show that the above mentioned method is reliable and an important progress for measurement of the critical temperature of coal ash slagging on refractory board.