Sustainable Mining and Metallurgy

In the process of alumina production, the formation of pipeline scab in high pressure dissolution process is inevitable. Scab will reduce heat transfer efficiency, increase energy consumption and increase production costs. On the basis of introducing the composition and phase of scab, the cause and harm of scab, this paper analyzed the problems existing in the removal of scab in the high pressure dissolution process of Zunyi Aluminum Co., Ltd., and optimized and improved the existing high pressure water removal method. There are great differences in the mechanism and phase composition of the formation of high pressure dissolution pipeline scab. The low temperature section scab is mainly sodium silicon slag, and the high temperature section scab is mainly perovskite and hydroxyl perovskite. For low-temperature casing, scab removal can be achieved by increasing the cleaning pressure; for the high temperature section, the method of molten salt heating dry burning combined with high pressure water removal can be used to eliminate the scab. The production practice showed that under the conditions of salt dry burning for 3~4h, temperature of 300~320℃ and cleaning pressure of 150MPa, the cleaning effect of casing scar in high temperature section is obviously improved, and the heat transfer coefficient is obviously improved, with an average value of 900W/m²·℃. The optimization method has achieved good cleaning effect.