Low temperature pyrolysis of CCA treated wood waste
A sustainable development approach requires that decisions made on the processing of waste materials consider which technologies will maximise the useful recovery of both materials and energy from waste prior to any disposal. The waste considered in this project is waste of chromated copper arsenate (CCA) treated wood, which will increase significantly in quantity in the future. There are many technological options to manage CCA treated wood waste, but all have their limitations and problems. Thermal utilisation of the wood waste has the advantage of providing energy and concentrating wastes for recycling or disposal. Among the thermochemical processes thermal carbonisation, aiming at recuperating the metals and the energy contained in the CCA treated wood, has been identified as a candidate for the best available technology. However, more fundamental research work is needed to understand, prove, control and optimise this technology for this specific application. In the current research the metal (Cu, Cr and As) behaviour during the thermochemical conversion process and the characteristics and “value” of the pyrolysis products are studied in detail through experiments and modelling.
The experimental programme consists of different steps, starting with model compounds in the kinetically controlled regime to come to real impregnated wood samples that are treated in a lab-scale reactor where the combination of flow, heat transfer and chemical reactions is important. The influence of process parameters (pressure, temperature, heating rate, residence time, heater gas flow rate, oxygen partial pressure, steam addition) is investigated in order to define an operating window that minimizes arsenic release and guarantees products of high quality.
In the theoretical part a dynamic reactor model that accounts for transport processes as well as chemical kinetics is developed (in order to obtain good foundations for control strategy). Furthermore, the global system is modelled to incorporate the interaction between the different components. Energy and exergy balances enable to evaluate the efficiency of the system. The experimental results are used to validate the mathematical models.
Contact persons
Frederic Cuypers
Lieve Helsen
Collaborations
Company Thermya
K.U.Leuven - Department Chemical Engineering
Related projects
K.U.Leuven-OT project
Bilateral project with Thermya
Bilateral project with Arch Timber Protection
VMM study
