ScienceAsia 5 (1979): 027-042 |doi: 10.2306/scienceasia1513-1874.1979.05.027
THE EFFECT OF ATMOSPHERE ON OIL SHALE RETORTING
K. BUNYAKIAT and S. OSUWAN
Summary: An attempt was made to study the effect of atmosphere on Mae Sot oil shale retorting in a modified Fischer assay retort employing nitrogen, carbon dioxide and hydrogen gases. Mae Sot oil shale of 4-10 mesh size was retorted at 400o, 450o and 500 oC, each at various flow rates of 0.010, 0.015 and 0.020 cu ft/min. It was found that the maximum oil yield was 64.0 gallons/ton under carbon dioxide atmosphere retorting at 400.C and 0.010 cu ft/min. This is 18% higher than the Fischer assay oil yield of similar oil shale. The oil quality, judging from the low pour point and the high heating value is best at 34.5 oC and 10,545 cal/g obtained under hydrogen atmosphere retorting at 400 oC and 0.015 cu ft/min. However, the properties of oil produced under various conditions are only slighrly different.
The effect of carbon dioxide on higher oil yield at lower temperature can be explained as the result from carbon dioxide suppression of the decomposition of inorganic carbonates in oil shale resulting in higher heat available for kerogen decomposition at lower temperature. Continuous flow of gas during retorting also assists the diffusion of oil vapors from oil shale pores which is the rate determining step, hence increasing the oil yield.
Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
Received 12 February 1979