1、1、翻译原文Study on flotation characteristics of oxidised Indian highash sub-bituminous coalAbstract：It is well known that high rank coals are generally more hydrophobic than low rank coal or oxidised coal. Non-coking coal (sub-bituminous) of the Talcher coal field in India has very high ash content and
2、is believed to have oxidised surface. This coal is very difficult to float even at higher concentration of collector due to its oxidised surface with reduced hydrophobicity. This investigation has been carried out to study the flotation characteristics of oxidised Indian high ash sub-bituminous coal
3、 having particle size below 1 mm. Initially the flotation study was carried out using conventional reagents only in a Denver D-12 sub-aeration flotation cell. Then it was pre-treated with aliphatic alcohols i.e., ethanol and butanol to de-oxidise the coal surface. The attempt was also made using a n
4、on-conventional reagent known as black oil as promoter for this type of coal to enhance the floatability. The combinations of the above reagents were also studied to improve the flotation performance. Flotation study was also carried out at optimum reagent conditions to evaluate the flotation perfor
5、mance using flotation column. To characterize the flotation performance with respect to macerals response, the petrography study was carried out on bulk, concentrate, +500 m and500 m size fractions of tailings of the flotation. Based on the test data, it may be concluded that this coal has potential
6、 to give a product of around 31% ash content with 80.4% yield from 4142% ash content of feed coal. In case of column flotation, the product ash could be reduced further to 26.6% from the same feed coal with 66.5% yield.1. IntroductionCoal, an organic sedimentary rock is very heterogeneous; it contai
7、ns organic matter, which consists of various components with distinct chemical and physical properties referred to as macerals and inorganic matter mostly in the form of minerals. The quality characteristics of coal are attributed mainly to its nature of deposit and origin. While European and Americ
8、an coals are of marine deposits and of in-situ origin, Indian coals in general are of drift origin. The drift origin means the original plant materials, which were later transformed into coal, were transported by rivers and laid down. As a result, the plant materials were intimately contaminated wit
9、h clay and other detrital minerals giving rise to a high inherent ash content. In other words, extraneous material is intimately mixed in the coal matrix. In India 90% of the coal production is from Gondwana coals, situated mostly in south-eastern quadrant of the country. These are of drift origin (
10、Sagar et al., 2003).Macroscopically, coal is made up of finely mixed discrete organic entities known as macerals, which fall into three main groups with different physical and chemical properties: vitrinite, exinite (liptinite) and inertinite (Jimenez et al., 1998; Polat et al.,2003). The vitrinite
11、group comprises the most abundant macerals in coal. The measurement of vitrinite reflection is commonly used to determine coal rank. These macerals are derived from the woody tissue and bark of trees. As the rank increases, the reflectance of vitrinite group macerals increases simultaneously. On the
12、 basis of petrological study, coal is classified into two groups i.e., (a) sapropelic coal, which is not available in India and (b) humic coal. Humic coals are banded coals. All Indian coals are banded coals (Sarkar, 1994). Banded coal consists of alternate layers of bright and dull coals. The bands
13、 of macerals, which can be distinguished by the naked eye, are called lithotypes. The main lithotypes are vitrain (vitrinite-rich), fusain (inertinite-rich), clarain (vitrinite- and exinite-rich) and durain (inertinite- and exinite-rich). In general, the major minerals in coal are clay minerals (ill
14、ite, snectite, kaolinite), carbonates (calcite, dolomite, siderite) and oxides (quartz). The minor minerals are pyrite, sphalerite, hematite, limonite, goethite, spatite, feldspar and zircon (Damberger et al., 1984). The liberation characteristics of mineral matter differ from deposit to deposit bas
15、ed on its origin of formation.The majority of coal reserves in India are thick and inferior in quality. In India, the total reserve of coal is estimated to be around 253 billon tonnes as of 1.1.2006. About 86% of this deposit is non-coking coal. Most of the Indian non-coking coals contain high ash i
16、n the range of 4050%. A higher ash contentobviously is co-related with a poor calorific value. The gross calorific value is typically lower than 3300 kcal/kg (Yenigalla, 2003; Misra et al., 2003; Chowdhary, 1995).In general, washeries have been set up in India to beneficiate coking coal using heavy media cyclones (13+0.5 mm size) and froth flotation techniques (0.5 mm size). Beneficiation of non-coking (sub-bituminous) coals in India was not given due importance
