烧结特性对煤灰导热性能的影响

Effect of sinter properties on thermal conductivity of coal ashes

为了解析煤灰在反应器内壁或换热器表面上沉积层的导热特性,以3种煤灰(X,J和A)为原料,通过XRF,XRD,SEM-EDX以及热常数测定仪等分析化学组成、结构以及形貌对烧结煤灰导热性能的影响。结果表明:烧结煤灰的导热率和体积密度都随着温度的升高而增大,增大趋势因煤灰的化学组成不同而有明显差异。体积密度和导热率的增加速率都随硅比的增大而减小,随碱酸比的增大而增大。体积密度与热导率的变化呈线性关系。高温下,莫来石和石英等耐熔矿物的大量存在使酸性灰(X和J)的烧结速率缓慢,烧结体结构改变较小,导热率增加缓慢;而单斜辉石、钙长石等矿物质的存在,促使A烧结体的体积密度显著改变,导热率快速增加。

In order to resolve thermal conductivity of coal ash on the inner wall of reactor or the surface of heat exchanger, three typical coal ashes (i.e., X, J and A) with various compositions were employed to clarify the conductivity properties of coal ash depositions on the heat transfer or the inner wall of reactor. The correlations among chemical compositions, micro-structures and morphologies on the thermal conductivity of sintered coal ash were systematically investigated using XRF, XRD, SEM-EDS and thermal conductivity analyzer, etc. Results show that the thermal conductivity and bulk density increase with temperature increase. Their increasing trends are different due to various chemical compositions. The thermal conductivities present the linear relationship with the bulk densities for the same sintered ash. Under high temperature, the existence of refractory minerals, such as mullite and quartz, gives rise to some small changes of physical and chemical structure for acid ashes (X/J), which causes a slow increase of sintering rate and thermal conductivity. And the formation of minerals, such as clinopyroxene and anorthite, brings a great variation of bulk density for basic ash (A), which leads to the sharp increase of thermal conductivity. © 2015, China Coal Society. All right reserved.