Effect of programmed heating on yields and oil quality in retorting of Green River oil shale

Three large blocks of oil shale from the Hell's Hole Canyon outcrop were selected and graded with Fischer assay at 18, 45 and 73 US gal/ton. Smaller cubes with similar bedding planes were cut from these blocks, with side dimensions of around 0.12 m. These cubes were heated under a nitrogen atmosphere, with constant heating rates of 2, 1, and 0.5°C/min, respectively, from ambient temperature up to 600°C. Two additional runs were performed for each block holding the temperature constant for 24 hours at 200°C and 300°C (soaking conditions). In all cases the liquids collected during the retorting process had a higher hydrogen to carbon ratio (1.7 to 1.8) at the beginning of the runs than near their end (1.35 to 1.6). Their nitrogen content increased from 1.5 to 1.8 weight percent initially to 3 to 3.8 weight percent at the end of the runs. For the 200°C soaking condition the oil produced was lighter (i.e., lower density and better yield of lower boiling point components) than the oil prod