Pyrolysis of oil shale by solid heat carrier in an innovative moving bed with internals

Abstract

This article reports a new moving bed with particularly designed side and central channels as its internals for small-size oil shale pyrolysis by solid heat carrier. The bed is called moving bed with internals (MBI), and the solid heat carrier is shale ash from industrial Fushun retorting furnace. The pyrolysis was tested by varying the temperature of solid heat carrier, thickness of particle bed between the side and central channels, and ash-to-shale mass blending ratio in terms of the oil and gas product distribution and qualities. The shale oil yield is close to 90% of the Fischer Assay yield, and of the produced oil over 70wt.% is gasoline and diesel and its dust content is only about 0.1wt.%. The highest shale oil yield occurs at the pyrolysis temperature of 495°C. The shale oil yield decreases with increasing particle bed thickness due to the increased shale oil cracking over shale ash in the prolonged residence time of volatile products inside the particle bed. Mechanism analysis shows that the central channel in the MBI directs the pyrolysis products to flow from the annulus to center of the particle bed, and this makes the moving bed as a filtration layer that considerably reduces the dust content in the produced oil. Meanwhile, this lateral flow greatly shortens the time of secondary reactions occurring to the pyrolysis products so that MBI could be applied to small-size oil shale to produce shale oil with high yield and high quality.