Rules of Thumb for Reactor Design and Process Conditions for Thermochemical Treatment of Chromated Copper Arsenate (CCA) Treated Wood Waste

摘要

Lab-scale pyrolysis experiments have been performed to gain insight in the mechanisms influencing the metal behavior during carbonization of chromated copper arsenate (CCA) treated wood chips. To this end a fixed bed low temperature pyrolysis reactor and a thermogravimetric (TG) analyser have been used. Besides CCA treated wood chips, mixtures of metal and organic model compounds (AS_2O_5, As_2O_3, CrAsO_4, CrAsO_4 + Ca(OH)_2, AS_2O_5 + glucose, AS_2O_5 + lignin, AS_2O_5 + activated carbon, As_2O_3 adsorbed on activated carbon, CrAsO_4 + glucose, CrAsO_4 + lignin, CrAsO_4 + Ca(OH)_2 + glucose, CrAsO_4 + Ca(OH)_2 + lignin) have been pyrolyzed in a controlled way. The aim of these model compound experiments is not to imitate the real CCA wood pyrolysis process, but to isolate some individual mechanisms (without being influenced by a variety of complex interactions) and to study the influence of different process parameters on these mechanisms. The parameters controlled during pyrolysis (and their corresponding range) are: temperature (330°C - 430°C), heating rate (5°C/min - 20°C/min), residence time (10 min - 40 min), reactor pressure (0 bar gage - 5 bar gage), heater gas flow rate (1000 Nl/h - 1800 Nl/h), oxygen concentration (1 vol% - 3 vol%) and steam concentration (5 wt% -15 wt%).