The removal of trace elements from Spanish high rank coals by a selective agglomeration process

Abstract

The effectiveness and selectivity, over a wide oil concentration range, of the n-heptane agglomeration for the removal of trace and major elements from the fines of three Spanish anthracites, were studied. X-ray fluorescence spectrometry was used for the analysis of inorganic elements. Contents of trace and major elements in AT, AG and AV high rank coals were reduced in the range 10–55% depending on coal and oil concentration. Al, Ca, Fe, K, Mg and Si major and Ba, Mn, Rb and Zr trace elements were eliminated from the three coals with similar or slightly higher effectiveness than that corresponding to the agglomeration process. The effectiveness of the removal of Na, P and Ti major and Cu, Cr, Ni, Pb, Sr, V, Y and Zn trace elements was similar or less than that of the cleaning process. For a given element and oil concentration, the effectiveness of its removal from coal by agglomeration is influenced by coal type, the morphology of the minerals where the element is present and the composition, the size as well as the distribution of these minerals in coal. The selectivity of element removal from coal by agglomeration is both coal and oil concentration dependent. Pyritic sulfur was removed from AT coal with a remarkable degree of selectivity.