(144f) Design and Operation of a Laboratory-Scale Pyrolysis System

Since the early 1970's, the most widely used wood preservative has been chromated copper arsenate (CCA), resulting in nearly 80% of all treated wood products in North America being treated with CCA. By the end of 2003 CCA-treated wood was restricted to industrial applications, resulting in a considerable increase in the volume of CCA-treated wood slated for disposal. Landfilling was considered an acceptable means of discarding CCA-treated wood products until recently, as there have been instances of the toxic metals leaching from the landfills and contaminating the surrounding soil and groundwater. It is clear that traditional disposal methods are not adequate and that a safe and efficient disposal method for CCA-treated wood must be developed.

Fast pyrolysis, the heating of biomass at temperatures between 400°C and 650°C in the absence of oxygen, is a promising technology that can be applied to the disposal of CCA-impregnated wood waste. Pyrolysis of lignocellulosic material produces char, liquid condensate (bio-oil), and non-condensing gases. The focus of this research is on removing the CCA-metals from the treated wood waste while recovering the energy value of the wood. This is accomplished by concentrating the CCA-metals in the bio-oil, for possible re-use in wood preservatives, during pyrolysis. A laboratory scale pyrolysis system, capable of operating in the desired temperature range under atmospheric and vacuum conditions, has been designed. The system is also designed to enable the collection of each pyrolysis product so that complete mass balances on the metals can be performed, tracking the fate of the CCA components. This paper discusses the process of designing and operating the laboratory scale pyrolysis system, as well as preliminary experimental results.