A. Hardware

Pyrolysis systems are as varied as combustion systems. The ancient process of making charcoal by the slow pyrolysis of a pile of wood covered with earth is still used today in some developing countries. Pyrolysis times are several days and charcoal is the main product. Before fossil fuels became the preferred feedstocks for chemical production in the early part of the twentieth century, biomass pyrolysis reactors in industrialized countries consisted of various types of ovens and horizontal and vertical steel retorts, essentially all of which were operated in the batch mode. Provision was made for charcoal recovery, pyroligneous acid refining, by-product recovery, and gas recovery and usage. Modern pyrolysis reactor configurations include fixed beds, moving beds, suspended beds, fluidized beds, entrained-feed solids reactors, stationary vertical-shaft reactors, inclined rotating kilns, horizontal shaft kilns, high- temperature (1000 to 3000°C) electrically heated reactors with gas-blanketed walls, single and multihearth reactors, and a host of other designs.