Oil shale project run summary, small retort: Run S-24

A. Objective. Previous Lawrence Livermore National Laboratory pilot retort experiments, simulating modified in-situ (MIS) oil shale retorting, have employed relatively high (1-3 m/day) retorting rates. Such rates not only would have an obvious commercial economic advantage but, in pilot retort trials, have produced high oil yields. However, commercial MIS retorts may be limited to low (< 0.3 m/day) rates by pressure drop and mine safety considerations. Run S-24 was designed to determine the effect of a low retorting rate (0.24 m/day) on (a) oil yield, and (b) applicability of our correlations between fluid product data and both oil yield and retorting rate. B. Conclusions. Run S-24 gave results only partially applicable to field MIS retorts because the desired, overall low retorting rate was not achieved. We were unable to operate the retort under near-adiabatic conditions at the designed rate. Over-compensation of heat loss by the electric heaters attached to the vessel wall expanded the retorting front and artificially raised the effective overall retorting rate. However, even under these distorted conditions, our correlations between fluid product composition and oil yield were valid. Furthermore, the correlation between C2-C4 hydrocarbon production and retorting rate was also substantiated. Run S-24 results also defined and quantified the effects on the product gas of including steam in the injection air. Temporary elimination of steam produced measured decreases in production rates of H2, CO2 and H2S. The sources of the decreases were identified as reductions of, respectively, steam-char, steam-carbonate and steam-iron sulfide reactions. Conversely, steam elimination raised production of CO and COS.