Experimental Investigation On Factors And Mechanism Of Coal Ash Slagging On Tipical Refractories In A Coal Combustion System

The qualities of coals for utility boilers are low and varying too much in China. So, how to ensure the boiler to realize the high efficiency combustion and stable combustion has been a hotspot in boiler combustion technology fields. For refractory belt technology, which is one of the most simple, efficient methods for improving of inferior coal's burning stabilization, has been widely applying by coal-fired power plants. But after laid the refractory belts, some problems such as coal ash slagging would become even more severe. Coal ash slags are the major hidden dangers that do harm to boilers'security, economical operations. So, for burning low quality coal boilers, it's very important that how to use the refractory belt technology to improve boilers'stable combustion and to reduce the mass of coal ash slags as much as possible. If want to reduce the mass of coal ash slags, the coal ash slagging factors and the coal ash slagging mechanisms on refractories must be researched.In this paper, two kinds of high aluminum refractories and one kind of high SiC refractory, which all have been widely applying in coal-fired power plants, were used to experiment with five kinds of coal samples in a heating furnace and a horizontal type of Pulverized Coal experimental system respectively. Based on the melting temperatures and composition characteristics of coal samples, the effect of coal compositions and refractories on coal slagging characteristics were studied and compared through changed the experimental coal samples, experimental temperatures and refractories in these experiments and, in order to research the mechanisms of coal slagging on refractories, some text methods such as XRD, SEM, EDX etc. were employed. By means of hierarchical processing for coal ash slags, the microstructures and compositions of coal ash slags were studied. It is find base on these experiment results that the erosive thickness of coal ash slags is bigger on high aluminum refractories than on high SiC refractories. For high SiC refractories, the passivating reactions have been happened in air at high temperature, and then the SiO2 passivating film formed, so the erosion of coal ash slags on surface of high SiC refractories became more difficult. Therefore, the high SiC refractories are more suitable for refractory belt. The results of these researches can provide theoretical basis for coal ash slag mechanisms and can provided reference and guidance for the designs of refractory belts and the slagging prevention technologies of utility boiler.