An Evaluation of a Prototype Dry Pyrolysis System for Destruction of Solid Wastes

Pyrolysis is a technology that can be used on future space missions to convert wastes to an inert char, water, and gases. The gases can be easily vented overboard on near term missions. For far term missions the gases could be directed to a combustor or recycled. The conversion to char and gases as well as the absence of a need for resupply materials are advantages of pyrolysis. A major disadvantage of pyrolysis is that it can produce tars that are difficult to handle and can cause plugging of the processing hardware. By controlling the heating rate of primary pyrolysis, the secondary (cracking) bed temperature, and residence time, it is possible that tar formation can be minimized for most biomass materials.

This paper describes an experimental evaluation of two versions of pyrolysis reactors that were delivered to the NASA Ames Research Center (ARC) as the end products of a Phase II and a Phase III Small Business Innovation Research (SBIR) project. One version is a two-stage reactor that allows pyrolysis of the solid wastes and catalytic pyrolysis of the tars into additional gases and small amounts of carbon. The second version is a three-stage reactor that includes a third stage for catalytic combustion of the volatiles. This paper presents results on the pyrolysis of various biomass wastes such as wheat straw and peanut leaves. Recommendations and modifications to improve its performance and reliability are also discussed.