METHOD AND SYSTEM FOR HEATING A BED OF HYDROCARBON- CONTAINING ROCKS
Hydrocarbon-containing rocks (e.g. mined oil shale or mined coal or tar sands) are introduced into an excavated enclosure (e.g. a pit or an impoundment) to form a bed of rocks therein. One or more heaters (e.g. molten salt heaters) are operated to pyrolyze kerogen or bitumen of the rocks. In some embodiments, a hydrocarbon reflux loop is maintained within the enclosure to convectively heat the hydrocarbon-containing rocks by boiling hydrocarbon liquids from a reservoir at the bottom of the enclosure so that vapor passes to the top of the enclosure, condenses, and falls back through the bed. Alternatively or additionally, the rocks may be heated by heaters embedded within wall(s) and/or a floor of the enclosure. Some embodiments relate to techniques for upgrading mined coal to recover both hydrocarbon pyrolysis fluids and upgraded coal (e.g. anthracite coal).