The Relation of Pyrolysis Processes to Charcoal Chemical and Physical Properties.

Pyrolysis has been practiced for years for charcoal production but in the 1970s interest in new technology which minimized the production of charcoal and minimized the production of bio-oil began to be studied. Often called fast pyrolysis since they rely on reactor systems where high heat transfer is possible such as various fluid bed systems. The simplest reactor for this is a bubbling fixed fluidized bed of sand that runs at 500 C. An alternative approach is to allow higher char yields to occur by keeping the temperature below 400 C and using mechanical conveyance of the feedstock through the reactor where the residence time is on the order of minutes instead of seconds. One example of this is vacuum pyrolysis. This paper will review the nature of the historical and modern approaches to pyrolysis with emphasis on the underlying chemistry, the chemical characteristics of the products, and the types of practical production systems that could be used to integrate bioenergy with charcoal preparation for application to soils.