Oil shale project run summary, large retort: Run L-1

The overall goals were to study oil yield loss and operating characteristics in combustion retorting of a rubble bed with physical characteristics comparable to some of those anticipated in field retorts. Shale particle size range and bed porosity were the two parameters selected for simulation (along with shale grade which had been in the typical range in previous experiments). This run confirmed the important roles of rubble bed structure and particle size range in retort performance. Oil yield losses result when oil generation in the interiors of large particles lags behind that in the surrounding smaller particle matrix and when non-uniform permeability produces fingering of oxygen into regions which have not finished kerogen decomposition. In the first case, oil emerges from the blocks into a degrading environment in which thermal cracking, oxidative degradation and burning can occur. In the second case, high permeability flow paths carry oxygen into regions which are still producing oil and bypass regions of unburned char (solid fuel). Oil yield from lean shales, those which provide only enough residual char to fuel the process (or even less), will be most sensitive to char bypass. L-l demonstrated that reasonable oil yields (72 percent of Fischer assay) can be achieved even from rubble beds which induce complex non-uniform gas flow patterns. This, in turn, implies that more severe yield losses noted in other laboratory and field retort operations stem from additional causes (e.g., poor sweep efficiency or inordinate heat losses).