The biodesulphurisation of coal carried out in pile could be an interesting option to clean coal. In view of the good results obtained in biodesulphurisation test column at lab scale on a sample of semianthracite coal that proceed of an industrial plant with a high sulphur content, mainly pyritic sulphur, the feasibility of the process at pilot plant scale was studied. The pile was formed with 6 ton of gravity middlings coal sample with a grain size −12+0.5 mm from S.A. Hullera Vasco-Leonesa industrial plant. The coal has a total sulphur content of 3.78% and a pyritic sulphur content of 2.88%, the rest of sulphur is organic sulphur. The biodesulphurisation process in pilot plant follows three stages: stabilization of the pile, biodesulphurisation and washing. Heap was sampled twice during stabilisation stage, at the end of desulphurisation process and finally once washed. A pyritic sulphur removal of 39% and total sulphur removal of 23% was obtained. To complete the bioleaching process, the treatment of purge of leachate was carried out with the objective to recycling to head of process. The best treatment was a pre-treatment of the leachate until pH 4, and further treatment by reverse osmosis of the clarified water. Comparing this process with conventional precipitation to reach disposal limits, the reagents consumption and sludges were reduced considerably and due to the high quality of permeate it permits to recycle it to head of process.

An efficient depression of coal sulphides in the flotation process means a healthier environment and may be essential for the sustainability of a coal operation. Nitric and ferric oxidative pre-treatment of coal pyrite have been tested to improve pyrite depression, and the results are compared with those from the process of raw, not pre-treated coal. The removal indexes point to nitric pre-treatment as the best, but depression is still low. The microscopic study of feed and products, coupled to Digital Image Analysis (DIA) in all the cases, provide important clues to understand the behaviour of pyrite, which can be related to quantitative parameters, such as the exposition ratio (ER), and to qualified interpretation of the textures. Pyrite shows in the first float an unexpected hydrophobic behaviour, which is due to its occurrence as framboids, or porous particles which may be intergrown with organic matter and behave as coal. In general, the flotation results can be predicted from the DIA-data, e.g. depression of liberated pyrite into the tailings, increased by oxidative pre-treatments by 300% (ferric) or by >400% (nitric); or concentration of middlings with lower pyrite ER in the floats. DIA is an efficient tool to obtain some important quantitative informations which otherwise would be inaccessible (e.g. the morphological data on >1,000,000 pyrite particles for this study), and its use should be enhanced to check ore processing.

This chapter discusses biological sulfur removal by thiobacillus thiooxidans in fine coal coming from a flotation washing plant. The results of the bio-desulfursulfursulfurization of fine coal coming from a washing process with Thiobacillus thiooxidans NCIMB 8343 indicates that the more adequate value of the initial pH is 3.6 achieving a percentage of desulfursulfursulfurization about 15% for a slurry concentration of 20% wt/v, and a diameter of particles less than 15/am. In these operating conditions, the sulfur removal takes place from the pyritic form. The addition of nutrients to the culture medium is considered necessary. The influence of several parameters––pH, addition of nutrients to the slurry, slurry concentration, and types of coal––is described in the chapter.

Vapor-liquid equilibrium data at 1 atm pressure for the systems n-Heptane-Isobutyl Acetate, Toluene-Isobutyl Acetate and Toluene-n-Butyl Acetate are reported. The data were well correlated by different thermodynamic equations. The behaviour of the systems Toluene-Isobutyl Acetate and Toluene-n. Butyl Acetate is close to the ideality.