Study On New Technology Of Red Mud Dealkalization And The Red Mud Comprehensive Utilization

Large accumulation of Red Mud, which is a residue produced from the alumina smelting, will not only take up space, cause environmental pollution, but also result in the waste of natural resource. The mineral substances contained in Red Mud could be used as raw materials for cement production, while the alkali components confine this application. The research of Red Mud dealkalization will be of great importantce to decrease the discharge of Red Mud, promote the development of cement industry and the Great Wall Aluminum Corporation.Employing modern chemical methods such as TG-DTA, XRD, and IR, the analysis on the characteristics of Red Mud shows that there exists amorphism aluminosilicate and crystalline substances which consist of calcium carbonate (mostly calcite, little aragonite), perovskite. It is proven that during the heating process from ambient to 900℃, the deprivation of absorbed water and crystalline water in red mud is finished before 600℃, the decomposition of calcium carbonate taking place between 620℃and 760℃,β-C₂S taking shape at 700℃, and continually emerge at 800℃, whereas the perovskite remains inertia during the heating. According to the characteristic of Red Mud heat treatment and its chemical composition, it can be utilized in Portland cement production.The study on Red Mud grindability indicates that by grinding, part of the adhesive alkali in Red Mud can be deprived and its grain diameter can be diminished. This study also shows that choosing the right equipments can greatly promote the process of Red Mud dealkalization. Based on the Red Mud dealkalization orthogonal experiment with the addition of sulfuric acid, conducted with speed muller, the contents of Na₂O and K₂O in Red Mud can be lowered to 1.98% and 0.61%, and the milling time and the amount of sulfuric acid have significant influence to the result.The results of the calcium oxide hydration orthogonal experiment in high temperature and pressurization shows that the contents of Na₂O and K₂O can be reduced to 1.41% and 0.44%, and the deprivation of Na₂O and K₂O is greatly influenced by the reaction time and temperature. Combined with the two methods, the content of alkali in Red Mud can be reduced to less than 1%, and the milling time, the amount of sulfuric acid, the temperature have great influence on the Red Mud dealkalization.The optimum conditions for dealkalization are as follows: milling period 40min, per 100g red mud with sulfuric acid 0.0160 mol, reaction time 14min, temperature =120℃. Under this condition, the proportion of alkali in Red Mud can fall from 5.63%to 0.86%. The dealkalized red mud can be utilized in the production of 52.5^# Portland cement.According to this Red Mud dealkalization technology, the alkali in Red Mud can be decreased from 5.63% to less than 1% with the advantages of lower energy dissipation, continuity and sewerage zero draining. In terms of the overall evaluation, the comprehensive utilization benefit of Red Mud will be 80.6 Yuan per ton and this will greatly promote the development of our national alumina industry as well as cement industry.