Energy Saving Analysis Of The Calcination Section In The Production Of Pigment-grade TiO₂

In the sulfate process of TiO2 production, TiO2 is obtained by calcining hydrous titanium dioxide after washing and salt processing. Slurry of hydrous titanium dioxide is firstly filted with a vaccume drum filter to a solid content of about 35%. And then it is dehydrated, decomposed and crystallized in a rotary kiln. To finish the crystalline transformation of TiO2 and the growth process of pigment preliminary particles, the holding time of the rotary kiln is usually about 14-15 hours. Burning coal gas and diesel oil at the head of kiln provides it with necessary heat energy. Following discharge of the calcined titanium dioxide, it is cooled, ground and packed.Heat balance simulation was conducted according to the calcination process of hydrous titanium dioxide in the Titanium Company, Panzhihua Iron and Steel (Group) Cooperation. The results show that the heat energy consumption in the present device reaches 3.21×10~6kcal per ton of pigment TiO2. It is much higher than those leading levels attained by those companys abroad (about 2.5-3×l0~6kcal per ton of pigment TiO2). But 74.95% of the heat is uneconomically comsumed in vaporation of water or lost with flue gas. Only 1/4 of heat is effectively utilized in the process of decomposition and crystallization.A new calcination technology was suggested in this work. By a pressing filter, the slurry of hydrous titanium dioxide was dehydrated to a high solid content of about 55%. More water will be removed by mechanical method. It will greatly reduce the envatoration heat in the kiln. The simulation results show that, at the same TiO2 throughput, the ratio of heat consumed in envaporation and flue gas is reducedto be 57%. The total heat consumption in calcination decreases to about 2.31×10~6 kcal per ton pigment TiO2, lowering 27.94% comparing with the present consumption. The simulation also shows that about 10 tons of TiO2 production will be increased per day with the same heat consumption as present device. The heat consumed in envaporation and flue gas accounted for only 49.57% of the total heat consumption. This would yield extra profits of ￥1.8 million annually.