Microwave pretreatment of bauxite.

摘要

The major focus of this research work was the application of microwaves for the pretreatment of bauxite ores, in particular, the fracturing of the ore and also the reduction and separation of hematite. Firstly, the real and the imaginary permittivities of the ore were determined as a function of temperature. Secondly, the effects of heating time, sample mass, particle size, microwave power and sample bulk density on the sample temperature in a microwave field were studied. Thirdly, the strength tests were carried on bauxite (2) and bauxite (4) samples after the microwave and conventional preheating. Both the preheating can reduce the sample strength index significantly. This was attributed to fracturing of the sample. With microwave heating the fracturing was mainly resulted from the selective heating of hematite in bauxite sample and dehydroxylation of gibbsite in some cases. With conventional preheating, the fracturing was caused by the dehydroxylation of gibbsite alone. Fourthly, the microwave assisted reductions of hematite in bauxite (3) were performed with four experimental configurations. The maximum hematite of 88.65% was recovered by using the fourth arrangement with the alumina recovery of 70.27%. As a comparison, the conventional heated reduction can recover about 54.58% hematite and 89.33% alumina.