| Quartz sand, a very versatile non-metallic mineral, was raw materials of nearly a hundred kinds of industrial products due to its good heat-resistance, corrosion-resistance, rich in resources and low price, etc., widely used in the glass industry, photovoltaic industry, the field of padding, production of silicon metal casting industry and so on. With the steady developments of quartz purification technologies, calcination was widely applied to quartz purification by virtue of its own superiority. Therefore, it will lay a foundation for expanding the application of calcination process in the quartz purification fields to investigate on the influence of calcination on quartz’ grinding characteristics and acid leaching purification.First of all, the 1# quartz simple, taken from Inner Mongolia Ulanhot, was used to study the changes of quartz ores’characteristics by means of several methods such as chemical components analysis, mineral compositions analysis, surface morphology observation using scanning electron microscope, differential thermal curves measurement, bearing pressure determination and specific surface areas analysis. The results showed that calcination and water quenching had few effects on the chemical components, mineral compositions and crystal structures of quartz ores. However, plenty of cracks were formed with specific surface areas increased and bearing pressure decreased significantly after the ores were calcined.After that, a series of grinding tests were conducted to investigate the influences of calcination temperature, calcination time, calcination particle size, cooling method and standing time after calcination on grinding characteristics of quartz ores. The generating speeds of -0.355+0.074mm,-0.074mm in the grinding products were employed as evaluation indexes of grinding process. The results showed that the grinding efficiency increased with the rise of calcination temperature. When the calcination temperature was 800℃, the growth of generating speeds for the two specified size had reached 2.13 g·L-1·min-1、0.73 g·L-1· min-1 respectively. The reasonable calcination temperature range was 800～900℃. The calcination time was relative to the ore particle size of calcination. The smaller the ore particle size was, the shorter the calcination time was required. In the conditions of this study, the required calcination time for -100+25mm and -25+5mm quartz ores were 10min and 5min respectively when the calcination temperature was 900℃. With the same calcination temperature and calcination time, the particle size of grinding products increased with the increasing of calcination feeds’particle size. But the grinding efficiencies of calcined quartz ores were apparently higher than that of not calcined ores. What’s more, the fineness and uniformity of the grinding products of calcined ores were both improved obviously as well as the coarse particles reduced evidently.Based on the study of the effects of calcination on the grinding characteristics of quartz, the experiments were carried out to study the impacts of calcination on acid leaching purification process using 1 quartz simple, 2# simple taken from Inner Mongolia Xiwuzhumuqin Banner. It was found that, comparing with the original ore, the characteristics of acid leaching for calcined quartz were not changed for both different calcination sizes and different calcination temperatures. Most of the iron impurity in the calcined and not calcined quartz could be removed under the leaching test conditions of this paper, but the removal rate of the aluminum impurity was generally low. For not calcined quartz, H2SO4, HC1, HF and H2C2O4 could be used to leach the quartz ore and would obtain better results, among which H2C2O4 was the best. According to the leaching results of the experiments of oxalic acid, the suitable conditions for not calcined quartz that the size was -0.355+0.1mm were leaching equilibrium time 1h, leaching temperature 20℃, the leaching concentration of the oxalic acid 1%, leaching liquid-solid ratio 1:1, ultrasonic power 200W. The suitable conditions for calcined quartz that size was -0.355+0.lmm were leaching equilibrium time 2h, leaching temperature 20℃, the leaching concentration of the oxalic acid 1%, leaching liquid-solid ratio 1:1, ultrasonic power 225W. On the basis of the condition tests results of mixed acid leaching, the suitable conditions for not calcined quartz were H2SO4:H2C2O4=9:1, the total concentration of acids 15%. The suitable conditions for calcined quartz were H2SO4:HF= 7:3, the total concentration of acids 15%.To further verify the above acid leaching results, the acid leaching tests were conducted using the 2# quartz sample under the same conditions. The results showed that the effects of calcination on the 1# and 2# quartz samples’characteristics of acid leaching purification were same basically, which meant that calcination had few influence on the characteristics of acid leaching purification of the two samples. The leaching effects had a great relationship with the contents and the modes of impurities in the quartz ores. The lower impurity contents and no structural impurities in 2# quartz sample led to lower impurity contents in leaching products than 1# quartz sample. Leaching the sample of -0.355+0.1mm under the appropriate conditions, the calinied 1# quartz could obtain the purified products containing 0.187% aluminum impurities and less than 0.001% iron impurities, meet the standards of secondary silica sands in "industrial pickling quartz sand". Not calcined 1# quartz sample could obtain the purified products containing 0.210% aluminum impurities and 0.002% iron impurities, up to the standards of high purity quartz sands. The calcined and not calcined for 2# quartz sample could obtain the purified products containing 0.016% and 0.038% aluminum impurities respectively, containing 0.009% and 0.004% iron impurities respectively with the content of SiO2 above 99.9%. Both calcined and not calcined 2# quartz sample could meet requires of the quartz sands used for optical glass.At last, the mechanisms of calcination improving quartz’s grinding efficiencies, iron and aluminum removal using acids and improvement of ultrasound-assisted oxalic acid leaching were discussed preliminarily. |
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