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实际上所有用于制铝、磨料、陶瓷、玻璃以及其他工业的氧化铝,都是用拜耳法从铝土矿制取的。所用的基本原理虽然都和原先有过的一样,但在工艺上却有显著的发展。生产过程利用循环的苛性碱溶液,在整个循环中的各处,温度和浓度各不相同。氧化铝的溶解度,随碱浓度和温度的增加而增加。因此,应该在高温下用高碱浓度的循环溶液从铝土矿中溶出氧化铝。所得的富含氧化铝的溶液,除去溶解的和不溶解的杂质后,经冷却和稀释氧化铝成为过饱和,变成水合物析出。水合氧化铝焙烧成氧化铝。所有用户都需要化学纯度极高的产品,此外还要求产品有极大差别的物理性质。现代工厂的年产量在250000吨到500000吨氧化铝范围内。本文讨论近代拜耳法的化学工程学,特别是一座复杂工厂的设计条件和操作,包括在生产溶液和料浆的腐蚀、磨损和结垢状况下操作的热交换器、蒸发器、反应器、固液分离设备以及辅助设备。
In fact, all alumina used in aluminum, abrasive, ceramics, glass and other industries is made from bauxite by the Bayer process. Although the basic principles used are the same as those originally used, there has been a significant development in technology. The production process utilizes circulating caustic solutions that vary in temperature and concentration throughout the cycle. The solubility of alumina increases with increasing alkali concentration and temperature. Therefore, alumina should be dissolved from the bauxite at a high temperature with a circulating solution of high alkali concentration. The resulting alumina-rich solution, after removal of dissolved and undissolved impurities, is cooled and the alumina is diluted to become supersaturated to precipitate as hydrates. The hydrated alumina is roasted to alumina. All users require products of extremely high chemical purity, in addition to the very different physical properties of the product. Modern plants produce between 250,000 tons and 500,000 tons of alumina per year. This article discusses the chemical engineering of modern Bayer processes, in particular the design conditions and operation of a complex plant, including heat exchangers, evaporators, reactors, and solids that operate in the corrosive, abrasive and fouling conditions of production solutions and slurries Liquid separation equipment and auxiliary equipment.