Technological Study On Sandy Alumina Production By Continuous Carbonization Precipitation Of Sintering Process

As the application of dry scrubbing technique and large-scale central point-feeding pre-baked anode cell in modern electrolytic aluminum industry, raw material alumina is required for higher physical index which can be met by sandy alumina. Its major physical performance indexes are particle size -45μm﹤15% and attrition index﹤20%. So it is necessary to develop sandy alumina production technology suitable for the domestic bauxite resources and alumina production process, especially sandy alumina production technology by continuous carbonization precipitation of Sintering Process.In this paper, the author theoretically analyzes the variation law of carbonization precipitation process in sodium aluminate liquor by starting with carbonization precipitation technology of Sintering Process. By researching the influence of various factors on product quality of carbonization precipitation in laboratory experiment and pilot experiment, the author puts forward that the major factors affecting product quality of carbonization precipitation are temperature of carbonization precipitation, gradient of precipitation rate, time of precipitation, characteristic of crystal seed and addition of seed etc. The technological conditions of sandy alumina production by carbonization precipitation are defined as follows:Temperature of pregnant liquor is 70～73°C; time of precipitation is 5.0～6.0h; factor of seed is 0.08～0.14.Gradient of precipitation rate is in turn controlled as 18±3%, 42±3%, 62±3% and 86±3% till qualification from first tank to last tank.On this technological condition the industrial experiment and commercial production are carried out. Alumina product transformed from hydrate through GSC calcinations has reached the following physical indexes:Particle size +150μm average 4.83%, -45μm average 9.64% and fineness index 3.25%; higher strength and attrition index average 10.5%.Chemical composition of alumina product has met the requirement of metallurgical alumina grade II.Sandy alumina precipitation technology of Sintering Process can be widely applied to alumina refineries with continuous carbonization precipitation of Sintering Process.