Biomass can be torrefied to improve the fuel quality prior to its utilization. In addition, a large number of soluble alkali metals can be removed by water washing, to solve slagging and other ash-related problems. In this study, computer-controlled scanning electron microscopy (CCSEM) was used to analyze the mineral composition and elemental distribution of straw, torrefied straw char, and torrefied-water washed straw char. The mineral transformation behavior and the distribution of main elements, when these biomass species were individually co-combusted with coal, were also studied in detail. The comparison of the mineral composition of bulk ash obtained from torrefied straw combustion and straw combustion revealed that the quartz phase decreased and the aluminosilicates of K-, Na-, and Ca–Fe–K increased in the former compared to that in the latter. After the torrefied straw was washed with water, the quartz and Si-Rich phases increased. K aluminosilicate decreased and the quartz phase increased when the torrefied sample was co-combusted with coal at both mixing ratios of 1:1 and 1:4 compared to straw/coal co-combustion. When the torrefied-water washing sample and coal were co-combusted at a 1:1 ratio, the quartz phase decreased, and the Si-Rich and mullite phases increased. When the straw/torrefied char/torrefied-washed char was co-fired with coal at the 1:4 ratio, the amount of K aluminosilicate was less compared to that observed at the 1:1 ratio. It can be concluded that both torrefaction and torrefaction-washing can reduce the content of low-melting-point aluminosilicates in the mineral composition of the studied biomass after co-combustion, which can be beneficial to alleviate the ash slagging problem.

生物质可以在使用前进行烘焙以提高燃料质量。此外，水洗可去除大量可溶性碱金属，解决结渣等灰分问题。在这项研究中，计算机控制的扫描电子显微镜 (CCSEM) 被用来分析秸秆、烘焙秸秆炭和烘焙水洗秸秆炭的矿物组成和元素分布。还详细研究了这些生物质物种与煤单独共燃时的矿物转化行为和主要元素的分布。干烧秸秆燃烧和秸秆燃烧得到的散装灰的矿物组成的比较表明，石英相减少，铝硅酸盐 K-、Na-、与后者相比，前者的Ca-Fe-K增加。将烘焙过的秸秆用水洗涤后，石英和富硅相增加。与秸秆/煤混合燃烧相比，当烘焙样品与煤以 1:1 和 1:4 的混合比混合燃烧时，铝硅酸钾降低，石英相增加。当水洗样品和煤以 1:1 的比例混合燃烧时，石英相减少，而富硅相和莫来石相增加。当秸秆/烘焙炭/烘焙洗涤炭与煤以 1:4 的比例共烧时，与在 1:1 的比例下观察到的相比，铝硅酸钾的量较少。