Research On Stockpiling Technology By Mixing Semidry Process For Red Mud Produced From Bayer Process

Before 2007, in Chalco's Shandong Branch, all the red mud produced from the Low Temperature Bayer Process were used in dosing step of the Sintering process, while only those produced from the later process were discharged. As the prices of energy like burning coal, steam, etc. have increased significantly, and as the alumina output of the Bayer process has gone up, it is no longer economical to consume red mud from the Bayer process, which can only be discharged. The red mud contains little calcium oxide as Low Temperature Bayer Process requires no lime in the digestion step, that results in low stockpile strength, plus poor dehydration performance, it doesn't concrete after dehydration, therefore can't be used for dam construction. A temporary solution is using red mud from the Sintering process to construct the dam while stock those from the Bayer process inside after drying. The problems of this solution include high cost for piling with drying process, heavy dust pollution during transportation, etc.This subject made laboratory study on the mineral characteristics of red mud from the Bayer Process and that from the Sintering Process. Mixing experiments with different proportions of both red mud focused mainly on the strength and other indexes of the mixture, studied the mixing mechanism of the two red mud, and developed new stockpiling technology by mixing and semidrying the two red mud. Based on the breakthrough in laboratory test, field industrial test was carried out at Chalco Shandong Branch's no.1 red mud storage yard for the dam construction and stockpiling performance of the mixture by red mud from two processes. About 55,000 m3 of red mud was piled while the dam constructed reached 6 meters high in vertical direction. The geotechnical investigation & analog computation on the 300 meters long test dam body and the storage area, carried out by Xi'an Engineering Investigation and Design Research Institute during the industrial test, proved the technical feasibility of the stockpiling technology by mixing semidry process of the two kinds of red mud.After success in industrial test, this subject got industrialization application at Chalco Shandong Branch's red mud storage yards. Both no.2 & no.3 red mud storage yards mix two kinds of red mud for storage-the red mud produced from Sintering process, after filtration, is mixed with the final stage under-flow from the Bayer process by different proportions, then the mixture is pumped to the yards for dam construction and storage. After the application of mixing semidry stockpiling technology with two kinds of red mud, the yards have been running in good condition, the cost for stockpiling the red mud from Bayer process was sharply reduced, while the environmental problem, caused by dust pollution when transfer by trucks the filter cakes of red mud from the Bayer process, was solved.