Oil shale project run summary, large retort: Run L-2

A. Run Objective. To determine the retorting behavior of individual oil shale blocks in a shale rubble matrix during simulated modified in-situ (MIS) combustion retorting. B. Conclusions. The interiors of large particles are delayed in retorting (compared to a surrounding matrix of small particles) by the greater lengths of the heat transport paths in the larger particles and their lower surface/mass ratio. In Run L-2 these delays were determined for six cylindrical blocks of three sizes surrounded by two different matrices. The delays resulted in oil being released from the blocks into an oil degrading environment in the rubble matrix. The combination of high interior block and matrix temperatures and oxygen presence at block surfaces during oil release caused the oil produced in block interiors to be degraded either in transport from the block interiors or in the rubble matrix. For three of the blocks, the fraction of generated oil that was degraded to light (C,-C.) hydrocarbons was determined from analysis of retort offgas produced during block retorting. The offgas ethene/ethane ratio was a sensitive indicator of oil degradation for all the blocks. High ethene/ethane ratios of intra-retort gas sampled near the blocks correlated with oxygen presence. The ethene/ethane ratios increased with both block size and matrix heating rate. This last factor was influenced by matrix size distribution, the bulk heating rate tending to be lower for the broader size range material.