Study On Extraction Vanadium From Stone Coal With Oxidizing Roasting Process By Rotary Kiln

The key process of extracting vanadium from stone coal is oxidizing roasting processing, its aim is to transfer the low valent to high valent which can solve in the water, it determines the conversion rate of vanadium and the overall yield. The roasting equipment contributed significantly to the roasting results. There are many problems in the roasting process with traditional roasting equipment:the low conversion rate, causing serious waste of resources, the low automation level, and generate a large number of smoke gas which pollute the environment. In view of this situation, it is significant to extracting vanadium from stone coal with a new roasting equipment.In this paper, using the stone coal ore powder which from a place in Hubei for sodium roasting by laboratory electric rotary kiln, by changing the impacts which affects the conversion rate to explore the optimal conditions of dynamic oxidation roasting by rotary kiln for this stone coal ore. The optimal conditions are:the quantity of additive of NaCl is 10%, material stay in the kiln for 3 hours, the roasting temperature is 850℃, the charge ratio of rotary kiln is 16%, the optimal pressure of the kiln is about lOPa, comparing the experiment data of electric furnace we can draw the conclusion that:compare to the roasting process by electric furnace, rotary kiln can reduce the quantity of additive, and increase the conversion rate of vanadium dramatically. The quantity of NaCl was reduced from 16% to 10%,and the conversion-leaching rate was risen from 61.03% to 70.30%.Using the rotary kiln in the semi-industrial scale experiment, by changing the impacts to explore the optimal operating conditions of dynamic oxidation roasting by rotary kiln for this stone coal ore. The optimal conditions are, the residence time of material in the kiln is 3.5 hours, and the conversion-leaching rate has reached 67.5%.Through analysing the residence process of the material, we know that in this semi-industrial scale experiment, the critical impacts which affect the conversion rate is the time which the material stay in the high-temperature zone.According to the Fourier heat conduction equation, we get the model of heat transfer in the material of rotary-kiln.and also get the temperature distribution of the rotary kiln axial. Dividing the rotary kiln into four temperature range, calculating the time which the material stay in each temperature zone, drawing the conclusion that the optimum time which the material stay in high-temperature zone is 90 min. At last, investigating the agglomeration phenomenon in rotary kiln and the impact on the conversion-leaching rate, and analysing the cause of agglomeration phenomenon.From all of above, the semi-industrial scale experiment proves that extracting vanadium from stone coal by rotary kiln is feasible, providing reliable theoretical and practical foundation.