Influential factors on the oil agglomeration process for coal recovery from different grade coals

Abstract

Large amounts of waste fine coals are produced, which are difficult to be treated because of high ash content and inorganic sulfuric compounds. In order to make efficient use of waste fine coal, a retrieval technique is necessary for the recovery of coal combustible content from fine waste coals. Nowadays, the floatation process can be used, but it is impractical for developing countries due to high costs, then the oil agglomeration process can deal with these problems. In this study, we investigated the affecting factors of coal cleaning efficiency of oil agglomeration on the element content and chemical structure of three different grade coals because there are many grades of coals around the world. For determination of chemical content in three different grade coals, the help of proximate and ultimate analysis was used, and then for investigation of their chemical structure differences of carbonaceous content, a Fourier transforminfrared spectrometry (FT-IR) was applied. Furthermore, for the oil agglomeration experiments, kerosene and vegetable oil which differ in structure were used as aggregating agents. We used ash free coals or their mixed samples which were conditioned to the ratios of carbonaceous and ash content in order to make it the same contained amounts. From the results of the oil agglomeration experiments, it was concluded that the characteristics of agglomerate and the coal cleaning efficiency of oil agglomeration are not only influenced by the oil types, but also affected by the oxygenic content, aromatic and aliphatic chemical structures in different grade coals. Oxygenic function groups of carbonaceous content in coal samples , Waste Management and the Environment VI 187 www.witpress.com, ISSN 1743-3541 (on-line) WIT Transactions on Ecology and The Environment, Vol 163, © 201 WIT Press 2 doi:10.2495/WM120 1 18 prevent oil from attaching to the carbonaceous surface and forming the bulky aggregate. Then, it leads to depressing combustible matter recovery; however, this can be improved by changing oil types. Oxygenic content in oil such as vegetable oil plays the role of the bridging material to the oxygenic function groups of carbonaceous content in coal samples. Moreover, the aromatic functional groups in carbonaceous content have the resonance inspection of delocalized  electrons; it interacts badly to the aliphatic functional groups in oil. Comparatively carbonaceous content consisting of more aliphatic series tends to form aggregates easily. Whatever coals we use on the oil agglomeration, it is possible to achieve better efficiency by taking these factors into account.