Concurrent thermal processes. Pyrolysis and gasification

Spent shales prepared by the Fisher method from oil shales of the Rotem deposit/Israel were studied in a continuous fluidized bed reactor at 700-900°C under atmospheric pressure, using mixtures of nitrogen and carbon dioxide as the fluidizing gas. A set of simultaneous processes takes place, including pyrolysis of the organic residue in the spent shales, decomposition of calcium carbonate, dehydration of clay phases, decomposition of pyrites, reduction of anhydrite to calcium sulfide and other minor reactions. An important secondary process is gasification of the organic residue by carbon dioxide produced by carbonate decomposition or combustion. The extent to which these reactions take place depends on temperature, composition of the fluidizing gas, particle size of the spent shales, and mean residence time of the particles in the reactor.