Liquid Crude For Some Atmospheric Desilication Technology And Industry Research

Desilication of green solution is a key process to maintain high quality of product and involves in consumption of energy. At present, the two-stage desilication technology, firstly to form sodium alumino-silicate hydrate at high pressure, secondly to form hydrate garnet at atmosphere pressure adding CaO or 4CaO.Al₂O₃ CO₂H₂O, was applied in alumina production by sintering process. Because more than 150℃ was needed to realize the first desilication, more energy was consumed, and scale was easy to be formed on the surface of instrument as well, which decreased the energy tranforming coefficient and shortened the equipment running time.Based on the literature about desilication at atmosphere pressure and combined the formation of sodium alumino-silicate hydrate with practical condition of desilcation in ZhongZhou branch of CHALCO, the desilication at atmosphere pressure was studied systemly in laboratory. The results indicated that the desilication was facilitated in the increase of temperature, prolongation of desilication time, augment of seed and application of activated seed. The suitable desilication technology was obtained: desilication temperature >95℃, desilication time varied 3⁴h, activated seed amount 50g/L. And then the desilication at ordinary pressure was experimented in industrial scale. Suitable technologies and equipments were recommended, that is: green solution stayed in tank for predesilication at 98¹05℃ for about 4h, solution was heated at about 115℃ in tube-still indirectly, solution stayed for 4h in tank. After the technology run two years, the better tenchology has been put up, that is: green solution stayed in tank for predesilication after heated, solution was heated at about 115℃ in casing pipes indirectly, solution stayed for 4h in tank at μsi 280-320. The technology has been applied in alumina production since May 2004, all technological index were in agreement with that of design. And equipment run stably, little scale can be found in casing pipes, equipment's running time prolonged obviously. The tenchnology appears in practical, economical and energy saving.