Economic Considerations of the Oil Shale and Related Conversion Processes

Abstract

Economical criteria for the evaluation of oil shales depends on the process of utilisation. For combustion the economic grade oil shale is defined as that having a minimum upper calorific value of 750 kcal/kg on dry basis. For pyrolysis, in general, the limiting kerogen content is a function of a lot of parameters but the lower quoted value is 5 % organic content which corresponds to oil yield of 25 l/ton of rock or 6 US gallons per short ton. Shale oil cost components include; mining, crushing, beneficiation and retorting of oil shale, and refining and upgrading of products. The fraction of mining, crushing and beneficiation costs are minor compared to the rest of the items. The grade and type of kerogen directly influences the economics ot the process. Oil shale beneficiation, by-product credits from sulphur utilisation and electric power generation are another contributing factor to economics; Efficient combustion adds to revenues and solves solid residues problem. Refining is one of the most important component of cost items of shale oil processing due to high hydrogen consumption. It is generally accepted that proportion of refining cost is about 20–40% of the total cost of production of oil from oil shale.