Desulphurization of petroleum coke

Abstract

The sulphur content in coal and petroleum coke varies from traces to 10% or more by weight. This exists in two

forms, inorganic and organic. Sulfur in coal and rocks associated with coal mines like petroleum wastes can occur as

organic sulfur, sulfate sulfur and pyritic sulfur. On combustion of coal/coke, sulphur gets released into the atmosphere

and contributes to the air pollution in the form of ‘acid rain’. Organic sulphur occurs as an integral part of the

molecular coal and the petroleum waste matrix and is not readily accessible for microbial attack. So, the removal of

organic sulphur from coal/coke/petcoke while retaining its fuel value is most difficult. Chemical processes need a

very lengthy and tedious process involving elevated temperature and pressure, which is not feasible on a technical

scale. On the other hand, biological processes occur under very mild reaction conditions. Hence, the desulphurization

of petroleum waste by microbial technique can be achieved in an economical and simpler way. In the present paper,

a biological process using <i>Thiobacillus thiooxidans </i>has been described for the removal of total sulphur from Navanagar

petcoke sample. The results have shown that the mean total sulphur content in the metcoke sample was 6.32%. After

first bacterial leaching with <i>T. thiooxidans </i>13.5% sulphur was removed by the bacteria and the remaining sulphur

content in the metcoke was 5.46%. The second leaching of the previously leached petcoke sample, using <i>T. thiooxidans</i>

resulted into sulphur removal upto 93%.