Heavy Petroleum Stock (HPS)/Fuel Oils (FO)/Residual fuels are the liquid or semi-liquid, high-boiling fraction of residue from the distillation of petroleum and are used as a fuel. HPS is widely used as a fuel for the power generation in the Diesel Engine Generating (DG) sets. After removal of the lower boiling fraction of crude oil the somewhat higher boiling fraction becomes gasoline and diesel oil. A portion of the higher boiling fraction is 'cracked' to yield additional gasoline. Still heavier oils become lubricants. Paraffin, asphalt, etc., are also extracted from the crude oil. It is the remaining residual oil, not economically usable for other industrial purposes, which is then sold as a relatively low cost fuel. With the advent of industrialization, requirement for Heavy Petroleum Stock (HPS)/Fuel Oils (FO) is increasing many folds. Additionally, as a sequel to the current steep rise in the cost of crude oil, the refinery profit margins are shrinking dangerously, which has put tremendous pressure on to the refinery production teams to extract more and more of middle distillates that fetch more money as compared to the residual fuels. This has a definite bearing on to the resultant quality of the residual products. In nut shell, therefore, the increased demand of residual fuels and simultaneously increasing severity in refining process has adversely affected the stability and compatibility of residual fuels leading to emergence of problems like sludge separation and filter choking during operation. Indian refineries are, therefore, facing challenging task to predict the stability characteristics of these fuels as though these fuels meet relevant Indian national specification, several field problems like sludge separation and filter chocking are reported. Studies conducted so far have indicated that the testing of residual fuel samples as per standard specifications is unable to address the field problems such as sludge separation and filter chocking. Processing severity and improper blending at the refinery end adversely affect the stability and compatibility of residual fuels leading to the field problems associated with sludge separation, filter chocking etc. It has been observed that optimizing process operation and proper selection and blending of cutter stock can tackle these problems. The present paper attempts to analyze the effect of plant operating conditions and use of appropriate cutter stock on the stability of residual fuels in the form of a case study. Potential use of additives for imparting fuel stability is also studied and included in the present paper.
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