The Coal And Slagging Lower Ash Melting Point Of Shaanxi Sex Research And Its Mechanism

Nowadays, liquid slag discharge is the most useful way of China’s gasifiers, which requires coal ash melting point to be less than 1350 ℃. The slagging rate of the coal combustion is the primary factor that makes combustion furnaces to operate steady. Therefore, it is particularly important to improve the ash melting characteristics and slagging rate and enlarge the using range of coal.Coal blending is one of the most effective ways to reduce the ash melting temperature and slagging rate. In this paper, eight different coals with different melting point are selected and match with different ratio. Coals with high ash fusion point are matched with coals with low ash fusion point to reduce the melting point, furthmore, the requirements of the gasifier liquid discharge would be satisfied. The mechanism of the relationship between coal blending and coal ash melting is discussed by analysing the chemical composition of the ash and XRD spectrogram. On the other hand, the influence of coal blending in coal slagging is studied and the conclusions are showen as follow.Firstly, the four kinds of coal ash melting temperature decrease significantly in the same way after mixing the coals with high ash melting point and coals with low ash melting point. It is nonlinear relationship between the change of coal ash melting temperature and matching ratios. Both of 1# coal matched with 10% of 5# and 3# coal matched with 10% of 8# coal can satisfy the requirement of the liquid state slag furnace and their effects are the best. 60% of the 8# coal should be added into 2# in order to make it satisfy the requirement, eventhough, its effect is the worst. The 4# coal can get a better effect by mixing with 30% of 8# or mixing with 20% of 7# and it also can fit with the requirements of the liquid state slag furnace.Secondly, the main reason for the effect of matching ratio to coal ash melting tempreture is analysied by XRD. In this process, it is found that the capacity and kinds of minerals in the coal ash changed. The increases of mullite, quartz and other minerals lead to an improvment of coal ash melting tempreture, to the contrary, the increases of calcite and feldspar reasult in the decrease of coal ash melting tempreture. Obviously, It is a difficult process to study the change of coal ash melting tempreture because there are too many variable quantity.Thirdly, it can be observed by SEM that the ash got under 815℃ is mainly composed of floc and a small amount of larger particles. As the increse of the burning tempreture, the ash gradually aggregate and form a large particle finally. Sometimes accompanied with the appearance of pores which is the evidence of emergence of gas. When the temperature reaches DT temperature, coal ash is composed of irregular large particles with smooth surface and form a glassy substance.Forthly, the slagging characteristic of mixture of high and low slagging coals reduces significantly. 11# coal is better than 9# coal for the use of reducing slagging rate of 10# coal. There are a lot of internal factors(the coal ash melting tempreture, the ratio of alkaline and acid, the ratio of calcium and iron, the ratio of silicon and aluminum and so on) which can effect the slagging characteristic of coals.