| Description |
New relations are developed for calculating enthalpy changes during heating, retorting, or cooling of raw, spent, or burned oil shales of various compositions. The relations describe the sensible heats of the minerals, kerogen, and char, and the reaction heats of kerogen pyrolysis and bound-water dehydration. The mineral sensible heat is obtained by summing the "handbook" enthalpy values of the constituent minerals. A relation for the heat capacities of kerogen and char as a function of their molecular formula and temperature is developed by correlating the heat capacities of several model organic compounds. Simpler relations for mineral, kerogen, and char heat capacities are derived specifically for Green River shale. For Green River shale, a relation for the extent of mineral dehydration as a function of temperature and a value for the heat of this dehydration are based on available data. The heats of Green River kerogen pyrolysis at 500°C after rapid heating, and near 350°C during slow heating are obtained by careful analysis of existing data. The new relations show excellent agreement at all temperatures with available data for the enthalpy requirements of heating raw, spent, and burned Green River shale of widely varying grades. They should be accurate at temperatures above those for which oil shale calorimetric data are available, since they are based on accurately measured high-temperature enthalpies of the Individual minerals and model compounds. The relations can be easily adapted to shales having different mineral and organic compositions, such as Devonian shales. |
