Study Of Characteristics Of None-equality Distribution Of Trace Elements In Coal Ash And Evaporation Of Mineral Matter In Coal

Coal combustion is the main way to get energy in China. Great harm has been done to our health and the environment by the trace elements which are released from coal combustion. In the meantime, mineral matter that is concomitant with the coal is a crucial key to effect the ash aggradations and feculence coagulation. Thus, it is essential to learn the characteristic of distribution of trace elements and the evaporation speciality of mineral matters.In the article, the content of trace elements in different density distinctions and granularity levels of Xiaolongtan flying ash were measured by means of ICP-MS and XRF, result indicated that: as the flying-ash's consistency or particle size increasing, it shows different rules in the content of trace elements. Some are decreasing, some are increasing. Some are increasing first, and then decreasing, there is a maximum in a point. Some are decreasing first and then increasing, there is a minimum in a point. It behaves a characteristic of none-equality distribution. When the sulfur-removing ash are compared with the non-sulfur-removing ash, the content of trace element of former are lower than the latter. So the sulfur-removing system restrains the releasing of trace elements. What's more, the density and the particle size more small, the more powerful the sulfur-removing system restrains the content of trace elements.Then thermogravimetric experiments of the coal from Shenfu, Xiaolongtan and Yangzonghai and their low temperature ash were compared. It was shown that the thermogravimetric curves of coal and their low temperature ash are common in that both of them have four differential thermogravimetric apices. The combustion characteristic of coal and its low temperature ash in two different atmospheres were analyzed. As to the coal, the kindling point,temperature of maximum weight loss, burnout temperature in condition of O₂/CO₂ are all lower when compared to the atmosphere of O₂/N₂. But the differences are all within 10%, which can be ignored. There is no obvious rule about the low temperature ash when the atmosphere is changed. The heating rate also has an important influence on the thermogravimetric curve. When the heating rate is promoted, thermogravimetric integral curve shifts to high temperature area, the location of differential curve peak shifts to the right, and the peak value of weight-loss also enhances accordingly. In high temperature area, carbon in coal has little influence on the evaporation characteristics of mineral matter. O₂/CO₂ restrains the evaporation of mineral matter. The evaporated quantity of mineral matter increases with the velocity of heating rate increasing.Results of this article have great sense on trace elements release controlling and hasten the full combustion of coal.