Chapter 12 - Microbiological desulphurisation of coal

Abstract

This chapter describes the microbiological desulfurization of coal. Atmospheric oxidation or weathering of coal can result in a significant reduction in the sulfur content. It is theoretically possible to catalyze this oxidative dissolution of pyrite, FeS 2 , in coal by the use of microorganisms. The rate of pyrite solubilization depends on the concentration of Fe 3+ in solution. In the presence of microorganisms, the rate of reaction is very rapid and the rate of solubilization is controlled by the rate of reaction. The rate of reaction is temperature dependent. Faster solubilization of pyrite from coal can be achieved by using S. acidocaldarius rather than T. ferrooxidans at the expense of providing additional energy to maintain the higher temperature required by this microorganism. The chapter presents the process conditions for a conceptual 7300 t/day plant for the desulfurization of coal with T. ferrooxidans. A large storage volume, in the form of lagoons, is required to provide a residence time of 18 days. These lagoons must be lined, covered, agitated, and aerated. The residence time and, hence, the required storage volume may be reduced by using S. acidocaldarius but at the additional expense of heating the lagoons to between 60°C and 80°C.