Study On Brown Coal Upgrading And Slurryability

With the gradually decreasing of highquality coal resources and quickly increasing ofmining costs, the whole world starts to lay more emphasis on the development of brown coalresources. However, its application is restricted by several reasons, such as its high watercontent, high oxygen levels, low calorific value, easy weathering and natural, inconvenient forlongdistance transport and so on. Only by upgrading process can the economic value ofbrown coal be improved and the application of brown coal be expanded.In this paper Yunnan Xiaolongtan brown coal is chosen as object of study and donedehydration and low temperature carbonization experiment, and the slurry performance of thebrown coal and their chars is discussed. The conclusions of study are as follows:Hot air drying and microwave drying have good dehydration effect on Xiaolongtanbrown coal, the calorific matter and ash of brown coal did not produce apparent change,calorific capacity significantly improved, but the dried brown coal can absorb the moisture inthe air, so that the moisture of brown coal regain. We simulate the climate condition on theSouth to do water absorbance experiment of dried brown coal, the results show that themoisture content of dried brown coal can retune to15%.Therefore the ideal dehydration targetof brown coal is about15%.By using the selfmade low temperature carbonization reactor, we do low temperaturecarbonization experiment of Xiaolongtan brown coal, the results show that with the increaseof carbonization temperature, the semicoke yield gradually decreases, whereas the tar yieldchange from rising to declining. The suitable temperature of lignite low temperature is in therange of550~600℃, when the tar yield (ca.6.5%) and semicoke yield (50~60%) are relativelyhigh. With the increase of carbonization temperature, the air dried basic volatile of semicokeof Xiaolongtan brown coal gradually diminishes (from33.56%to15.32%), the content offixed carbon increases from48.32%to65.47%, and the content of ash increases from15.6%to17.4%.The elemental content of carbon increase significantly, the elemental content ofhydrogen and oxygen quickly reduce in the semicoke.The slurry performance of Xiaolongtan brown coal is poor, its maximum concentration isonly48.85%, its can not reach the quality and technical requirements of coal water mixturefor combustion or gasification. The concentrations of coal water mixture increasesignificantly while there are made by semicoke which produced from low temperaturecarbonization. The concentration of550℃semicoke coal water mixture is highest, amount to66.51%, but the static stability is poor. By employing the mixture of Xiaolongtan lignite andsemicoke, slurry performance is reduced somewhat, but this can effectively improve thestability of semicoke water coal mixture, the concentration of coal water mixture is61.47%,reach the third grade of national coal water mixture standard. This provides effective way forthe preparation of high concentration coal water mixture by using brown brown coal.