Oil shale project: run summary for small retort Run S-11

Results are reported on retort run S-11 conducted to observe the effects of combustion retorting with undiluted air at relatively rapid burn (retorting) rates and to provide a base case for retorting small uniform shale (Anvil Points master batch -2.5 +- 1.3 cm) with undiluted air. It was found that a 0.6 m/sup 3//m/sup 2//minute superficial gas velocity gave an average rate of propagation of the combustion peak of about 2.7 m/day and an average maximum temperature on the centerline of the rubble bed of 1003/sup 0/C. Oil yield was 93 percent of Fischer assay. For small uniform shale particles (-2.5 + 1.3 cm) it is concluded that only small losses in yield (92 percent vs 96 percent in Run S-10) result from high retorting rates. Maximum temperature considerations preclude going to higher rates with undiluted air. Without diluent, a larger air flux would give excessive bed temperatures causing rock melting and potential closure to gas flow. In experimental retorts, another problem of excessive temperatures is potential damage to metal walls and in-situ sensors. No advantage is seen to using recycled off-gas as a combustion gas diluent. Inert diluents (e.g. nitrogen or steam) may be necessary for process control, butmore » the fuel values in the off-gas should best be used for energy recovery rather than burned in the retort during recycle. Another consideration from model calculations is that the use of recycle gas containing fuel components retards the retorting rate and so is undesirable. No further recycle experiments are planned as the results of this run proved satisfactory.« less