Microbial removal of sulphur from petroleum coke (petcoke)

Abstract

Petroleum coke (pet coke) is a carbonised heavy residual product obtained from petroleum processing. Pet coke contains between 1 and 10% w/w sulphur as both inorganic and organic forms. The removal of organic sulphur from pet coke is desirable to reduce the environmental harm of its combustion emissions but the elevated temperatures and pressures needed result in a lower fuel-value. The removal of sulphur by microbial attack involving acidophilic bacteria is an alternative approach and is the subject of this study. Single and mixed cultures of Thiobacillus thiooxidans (isolated from natural hot sulphur spring) and Thiobacillus ferrooxidans (isolated from an existing culture) were investigated for total sulphur removal from pet coke. Batch leaching experiments showed a reduction in total sulphur of 92% over 28 days. A combination of Thiobacillus species performed better than the single bacterial culture.