Theory And Technology Of Selective Dissociation-floatation Process On Accumulative Bauxite Desilicate

China's Guangxi and Yunnan, etc. are rich in accumulative bauxite ores. At present ore washing is the only way been used to desiliconize for the separation of accumulative bauxite ores due to less relevant separation technologies. Targeted at Wenshan accumulative bauxite in Yunnan Province, theory and technology of beneficiation-desiliconization are probed in this dissertation on the basis of the ore structure, with the help of microscopical observation, x-ray diffraction analysis, EDS spectrum analysis. The trend of aluminum minerals and silicate minerals during the process of crushing and dissociation characteristics of aluminum minerals and silicate minerals in various grain sizes of crushed products are also studied. Flotability and its mechanism of accumulative bauxite have been examined through infrared spectrum analysis, electrokinetic potential analysis, adsorptive capacity test and grain size analysis and so on. As a result, a prototype of "accumulative bauxite selective dissociation agglomeration floatation process" is developed. The main study contents and results are shown as follows:1. Properties of accumulative bauxite oresAccumulative bauxite ores have been formed through long-term karstification and transformation based on the mineral source of sedimentary bauxite. In the accumulative bauxite, the aluminum, silicon and iron are the principal elements which mainly exsit in such minerals as diasporite, kaolinite and limonite, etc. correspondingly with the features of higher-content aluminum, higher-content silicon, higher-content iron and lower-content sulfur. There exist differences in embedded characters among aluminum minerals and silicate minerals. Compared with kaolinite, diasporite aggregate is coarser in disseminated grain size and harder in hardness.The aluminum content is higher in the compact-structure accumulative bauxite ores while that is lower in loose-structure ones. In the accumulative bauxite, A/S value of coarser sizes is obviously higher than that in the fine size.2. Selective dissociation of accumulative bauxite oresDuring the grinding process, obvious selective dissociation phenomenon happens in powder cemented accumulative bauxite ores and clay cemented ones. Aluminum minerals are enriched in the coarse sizes. As a result, the improvement of dissociation facilitates higher A/S value in the coarse sizes.As for the crude ores with lower A/S value, it is difficult for the coarse-size products obtained from direct classification after crushing to meet the requirements of the Bayer process. When the grinding fineness is 50-55% content of-0.074mm size, the A/S value of +0.074mm size products from the powder cemented accumulative bauxite and clay cemented ones samples are all over 9, which satisfies the requirements of Bayer process on the bauxite concentrates. The recovery of aluminum is 40-50%. The increment of grinding fineness is in favor of improving the A/S value of the coarse-size products, but the recovery of aluminum reduces in the coarse-size products.Combined with microscopical observation, x-ray diffraction analysis and EDS spectrum analysis, it is found out that the liberation degree is higher in the coarse-size monomer after grinding, diasporite is mainly intergrowth with iron ore. Although the A/S is low in the fine-size ores, there still exists massive diasporite intergrowth, and aluminum minerals can be basically liberated from silicate minerals as well.3. Floatability of minerals in accumulative bauxiteThe floatability of diasporite and kaolinite in accumulative bauxite deposite is very close to that in the sedimentary one. It's a good pulp condition for the floatability of two kinds of minerals when the pH is between 6 to 9, in which the floatability of diasporite is higher than that of kaolinite. The floatability of diasporite is good at the size of+0.038mm while bad at -0.038mm. A certain amount of aluminum ions and iron ions can be used to activate the diasporite behavour in floatation.Aluminum oleate can be formed when chemical action of sodium oleate takes place with the surface of diasporite. The adsorption of sodium oleate on the surface of diasporite is two times more than that on the kaolinite, resulting in the difference in the floatability of the two kinds of minerals-diasporite and kaolinite. Appropriate amount of activator TK can selectively make fine-size diasporite produce the hydrophobic aggregate and improve the mineral recovery. Addition of sodium hexametaphosphate can increase the difference in floatability between diasporite and kaolinite. The adorption of it can enlarge the negative value of Zeta potential of mineral particles, so it is beneficial to the dispersion of slime.4. Desiliconization of accumulative bauxite by floatation processDesiliconization of Wenshan bauxite can be realized by means of the floatation process. Considering of the plenty of mine slime in the accumulative bauxite, selective activation of minor diasporite particles and strengthened pulp dispersion are the key to the desiliconization of the by floatation process. Highly effective activator TK can be used to activate the floatation of the accumulative bauxite and can greatly improve the recovery of aluminum under the premise of not lowering the A/S of the concentrates.In view of Yunnan Wenshan accumulative bauxite, the flowsheet of "Selective Dissociation-Agglomeration Floatation Process" is obviously much more better than the process of ore washing in the separation effect. By the former, concentrates of A/S= 11.30 can be obtained with the recovery of Al2O3 up to 81% in the entire flow.5. Comparison of technical economy between two flowsheets of "Ore washing-Bayer process" and "Floatation-Bayer process"The flowsheet of "Floatation-Bayer Process" for producing aluminum oxide with accumulative bauxite can be formed by using "Selective Dissociation-Agglomeration Floatation Process" developed in this research as a mineral processing technology. For Yunnan Wenshan Aluminum Oxide Factory with the capacity of 800kt/year, comparison and analysis of technical economy and social efficiency in terms of limit factors in the whole process from mining to the production of aluminum oxide indicate that compared with the flowsheet of "Ore washing-Bayer Process", the flowsheet of "Floatation-Bayer Process" can save the cost /or increase the total amount of profits by RMB 115 million Yuan per year, which has obviously improved the capacity to earn profits and to resist risks. Furthermore, the guaranteed life of the mineral resources in Wenshan Prefecture can be prolonged from 50 years to 99 years based on the existing proven reserves because of the greatly increased utilization efficiency of the resources. Therefore, this "Floatation-Bayer Process" has a good prospect for popularization, which will be of great advantage to the sustainable development of aluminum industry in Yunnan Province and to the sustainable advancement of local economy and society.