外文文献翻译--选煤厂介耗分析

第 1 页 中文 4300 字 专业英文翻译 第 2 页 毕业设计英语翻译 姓 名： 学 号： 学 院： 应用技术学院 专 业： 矿物加工工程 翻译题目： 选煤厂介耗分析 指导教师 ： 职 称 ： 讲 师 2011 年 6 月 第 3 页 英文原文 An analysis of medium losses in coal washing plants Abstract A major operating cost in dense-medium separation is in replacement of lost medium solids. The loss of medium solids, being costly, plays a crucial role in determining the economics of any preparation operation. Coal washeries that employ dense-medium cyclones often attempt optimization of the processes by varying the vortex or the spigot diameter and the feed relative density. While these changes help in closer control of the separation process, they also result in medium losses due to changes in the medium split ratio (ratio of the medium flow rate in overflow to underflow). Since medium solids are lost by adhesion to products and as magnetic separator effluent, the effect of the change in medium split ratio on the drain-and-rinse screens and, hence, the magnetic separator circuit needs to be studied. In Tata Steel's coal washeries, at Jharkhand India, which employs primary and secondary dense-medium cyclones in series to produce clean coal, middlings and rejects, reducing the relative density of feed medium, had an insignificant effect on the medium split ratio. On the other hand, changing the cone ratio (ratio of the overflow diameter to the underflow diameter) changed the relative density and the flow rates through the cyclone outlets, thus affecting the performance of the magnetite recovery circuit. A systematic study through laboratory tests and a detailed plant sampling campaign helped in identifying the causes of magnetite loss. Upon implementation of the recommendations, the magnetite losses decreased, resulting in a saving of approximately US$27,500 per annum. The study also helped in evolving some checkpoints for plant operators for identifying magnetite losses. Keywords: dense-medium cyclone； magnetite losses； drain-and-rinse screens； magnetic separators 1. Introduction Dense-medium (magnetite in the case of coal), a slurry/suspension having a relative density intermediate to that of valuable mineral and gangue, is generally used as the medium of separation in most coal preparation plants. The medium, being costly, plays a crucial role in determining the economics of any preparation operation. Dardis (1987) quotes figures of 20–40% of dense-medium plant operating cost being attributable to medium loss for plants engaged in mineral separations employing ferrosilicon as the medium. The figure is 10–20% in the case of magnetite. There are clearly incentives to reduce this loss, and it is often possible to do so with minimal capital expenditure through improved operating procedures and minor changes to plant configuration. This paper draws on the experience from one such study carried out by R&D Tata Steel, Jamshedpur, Jharkhand, India to identify some important operating issues in medium loss in coal washing plants and the factors influencing the loss. 2. Causes of medium loss in dense-medium plants There are normally only two possible routes by which medium can be lost from the plant: