J. Cara

Microbiological desulfurization of column-packed coal

Abstract A microbial inoculum was selected to be later employed in the desulfurization of column-packed coal. A percolating liquid at pH 1.5 was used, and the total iron was monitored throughout the process. The results, after 42 days of percolation indicate that elimination of pyritic sulfur achieved a level of 46%, with relatively small changes in the immediate analysis of the coal. In light of these results, a small pilot plant was designed in order to desulfurize coal in heaps of 20 to 30 ton.

The biodesulphurization of a semianthracite coal in a packed-bed system

The purpose of this study was to improve the desulphurization yield of a high sulphur-content semianthracite from northern Spain adapted to the process conditions of a packed-bed reactor, for which three 5-kg packed columns of coal were set up with the pH stabilized at 1.5. The process was begun by inoculating the first column with a culture obtained from micro-organisms native to the coal itself, mainly Thiobacillus ferrooxidans and Leptospirillum ferrooxidans, grown in a stirred reactor. The percolate of this column was then used to seed the second column, the percolate of which was then inoculated into the last one. The purpose was to obtain from the last column a better adapted and more active biomass which would give a better desulphurization yield for coal. Results show an increased yield from the first column to the last over the first 20 days of treatment, but the total desulphurization in the third column was less than expected, owing to a high precipitation of jarosite.

Semi-continuous bioleaching of heavy metals and trace elements from coal

The micro-organisms used in the processes of sulphur elimination from coal by bioleaching are currently considered to play an important part in the dissolving of other elements (Cu, V, Ni, Pb, Cr, Se, As, etc.). In this study an analysis is carried out a process of biodesulphurization of coal and the elimination of certain heavy and trace elements. An 8.4-1itre reactor was used, comprising three columns connected in series with a volume of 2.8 litres each. Twenty elements were studied, in three groups according to the criteria of the National Research Council of the USA, major components found in most coals in large quantities, elements hamafial to the environment and dements of medium and low environmental impact. Of the major components, only iron, calcium and phosphorous are leached throughout the process. Of the harmful dements, it can be said that almost all the cadmiun released is due to bioleaching. Arsenic and boron are also bioleached in the process. Of the elements of medium and low environmental impact, it is our opinion that only copper is dissolved, at least to any great extent, by bioleaching