Gunnel Olsson

Microorganisms for desulphurization of coal: the influence of leaching compounds on their growth

An investigation was undertaken to outline how microorganisms suggested for use in coal desulphurization are affected by compounds leached from coal. Three species of the genus Sulfolobus were studied. Sulfolobus acidocaldarius was seen to be affected by compounds leached from coal more negatively than Sulfolobus brierleyi and Sulfolobus solfataricus. It was observed that certain conditions during leaching, such as pH, temperature and leaching time, were important for the concentration of compounds leached from coal. It was seen that compounds leached from coal, in some cases, can improve the growth yield for the microorganisms.

Oxidation of pyrite by Acidianus brierleyi: Importance of close contact between the pyrite and the microorganisms

Experiments were done in order to study the thermophilic archaebacterium Acidianus brierleyi during oxidation of pyrite (FeS2). The microorganisms were grown both separated from the pyrite by a membrane and in close contact with the pyrite. From the results it can be concluded that direct contact is needed for good growth of the strain studied. The obtained results indicate that the direct contact mechanism may be applied to oxidation of sulfidic minerals by A. brierleyi.

Microbial desulfurization of coal by Thiobacillus ferrooxidans and thermophilic archaea

Several different microorganisms have been suggested for coal desulfurization. In the present investigation, the thermophilic archaea Acidianus brierleyi (DSM 1651), Sulfolobus acidocaldarius (DSM 639) and Sulfolobus solfataricus (DSM 1616) were compared with the mesophilic bacterium Thiobacillus ferrooxidans (DSM 583) concerning their capability of removing sulfur from coal. The desulfurization rate as well as the amount of sulfur removed by the microorganisms was studied. Two of the investigated microorganisms, Thiobacillus ferrooxidans and Acidianus brierleyi, were capable of oxidizing pure pyrite as well as oxidizing sulfur in coal. A kinetic analysis was performed assuming first order reactions. The rate constant for oxidation of pure pyrite by A. brierleyi was observed to be higher than for T. ferrooxidans, The values of the rate constants for sulfur removal from coal were comparable for the two microorganisms, but were higher than for oxidation of pure pyrite. (Less)

Microbial desulfurization of different coal types

This chapter discusses different coals compared with respect to the extent of sulfur removal and jarosite formation when processed with A. brierleyi. All coals are of low-sulfur type with a sulfur content ranging from 0.6 % through 1.8 %. The efficiency of the microbial processing of coal depends on three factors––namely, the rate of sulfur removal, the extent of sulfur removal, and the formation of jarosite. Each coal contains one part sulfur available for removal during microbial processing. The available sulfur can in most cases be deduced to pyritic and sulfatic sulfur, the latter representing a minor fraction of the total sulfur.

Microbial Desulfurization of Coal and Oxidation of Pure Pyrite by T. ferrooxidans and Acidianus brierleyi

SummaryThiobacillus ferrooxidans andAcidianus brierleyi were capable of oxidizing pure pyrite as well as oxidizing sulfur in coal. First order reactions were assumed in the kinetic analysis performed. For oxidation of pure pyrite the rate constant was higher forA. brierleyi than forT. ferrooxidans. For sulfur removal from coal the values of the rate constants were comparable for the two microorganisms.

Desulfurization of Low Sulfur Coal by it Acidianus brierleyi: Effects of Microbial Treatment on the Properties of Coal

The effect of microbial desulfurization of two different low-sulfur coals by the thermophilic archaebacteria Acidianus brierleyi was studied with respect to the following properties of the coal: porosity, surface area, pore diameter, particle size, heating value, proximate and ultimate analyses as well as ash composition. About 35-40 percent of the sulfur was oxidized microbially. The microbial treatment only had a slight or negligible effect on most properties. Significant increases were seen with respect to oxygen content and volatile matter for one of the coals. The ash content had a significant increase in phosphorus which originated from the growth medium. Furthermore, jarosite formation was significant, especially for one of the coals investigated. For the same coal a large increase in porosity was seen and the surface area decreased significantly at the same time. (Less)

The measurement of cell growth in coal slurries

Microbial growth in coal slurries can be detected if surfactant is present in the samples by analysing the protein concentration after disintegration of the cells. Without surfactant present in the samples, the proteins are readily adsorbed on the coal surfaces. A suitable surfactant is sodium dodecyl sulphate at 0.5 to 1% of the sample volume.