Comparison of the Acceptability of Various Oil Shale Processes

While oil shale has the potential to provide a substantial fraction of our nation’s liquid fuels for many decades, cost and environmental acceptability are significant issues to be addressed. Lawrence Livermore National Laboratory (LLNL) examined a variety of oil shale processes between the mid 1960s and the mid 1990s, starting with retorting of rubble chimneys created from nuclear explosions (Lombard et al., 1967) and ending with in-situ retorting of deep, large volumes of oil shale (Burnham, 2003). In between, it examined modified-in-situ (MIS) combustion retorting of rubble blocks created by conventional mining and blasting (Lewis and Rothman, 1975; Campbell, 1981), in-situ retorting by radio-frequency energy (Mallon, 1980), aboveground combustion retorting (Braun et al., 1984), and aboveground processing by hot-solids recycle (HRS) (Lewis et al., 1986). This paper reviews various types of processes in both generic and specific forms and outlines some of the tradeoffs for large-scale development activities. Particular attention is given to hot-recycledsolids processes that maximize yield and minimize oil shale residence time during processing and true in-situ processes that generate oil over several years that is more similar to natural petroleum.