Formation of metal agglomerates during carbonisation of chromated copper arsenate (CCA) treated wood waste: Comparison between a lab scale and an industrial plant

Department of Mechanical Engineering, University of Leuven, Louvain, Flemish, Belgium
Journal of Hazardous Materials (Impact Factor: 4.53). 10/2006; 137(3):1438-52. DOI: 10.1016/j.jhazmat.2006.04.041
Source: PubMed


This paper compares the results obtained by scanning electron microscopy coupled to X-ray analysis (SEM-EDXA) of the solid product after carbonisation of treated wood waste in a lab scale and in an industrial installation. These setups (lab scale and industrial) are characterized by different operating conditions of the carbonisation process. Moreover, the wood waste input to the processes differs significantly. From this study, it is clear that some similarities but also some differences exist between the lab scale study and the study with the industrial Chartherm plant. In both reactors, a metal (and mineral) agglomeration process takes place, even in the case of untreated wood. The agglomerates initially present in the wood input may serve as a seed for the metal agglomeration process during "chartherisation". The industrial setup leads to a broader range of agglomerates' size (0.1-50 microm) and composition (all possible combinations of Cu, Cr, As and wood minerals). Some agglomerates contain the three metals but the major part is a combination of wood minerals and one or two of the three preservative metals, while all agglomerates analysed in the lab scale product contain the three metals. The separate influence of wood input characteristics and process conditions cannot be derived from these experiments, but the observations suggest that the higher the CCA retention in the wood input is, the easier is the metal agglomeration process during chartherisation of CCA treated wood waste. From the analyses performed in this study it seems that copper behaves differently in the sense that it agglomerates easily, but the resulting particles are small (<1 microm).

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    ABSTRACT: Earlier research has identified the Chartherm process (Thermya, France) as a candidate for the best available technology to treat chromated copper arsenate (CCA) impregnated wood waste. This paper presents the working principle, the characteristics and the current state-of-knowledge related to the process, illustrating clearly the differences with pyrolysis and carbonisation processes. To emphasise the specific nature of the process, it has been given its own name 'chartherisation'. The avoidance of tar and dioxin release, the role of the solid matrix in the metal behaviour and the separation process are described. Furthermore, the possible benefits of working at elevated pressure are discussed, based on the experience with charcoal production from coal and biomass. This paper shows that more fundamental research is needed to understand and model all mechanisms contributing to the characteristic nature of chartherisation, in order to control the dynamic behaviour and tune the operating conditions in the reactor on the quality of the products requested.
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    ABSTRACT: Recycling of waste wood is important for the effective utilization of natural resources. Thermal degradation process seems to be a promising technology for material and energy recuperation out of CCA treated wood waste. The charcoal product resulting from CCA treated wood contain Cu, Cr and As. The research aims at thermal valorisation of CCA treated wood waste using low temperature pyrolysis at different heating rates. During pyrolysis an agglomeration process takes place which results not only the growth of existing mineral agglomerates but also the formation of new agglomerates. The chemical and the physical characterizations of pyrolysis solid products show that the CCA treated wood waste could be used for the production of materials in particular charcoal with high specific area and CCA metal agglomerates.
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    ABSTRACT: In this paper, pyrolysis and hydroliquefaction processes were successively used to convert CCB-treated wood into bio-oil with respect to environment. Pyrolysis temperature has been optimized to produce maximum yield of charcoal with a high metal content (Cu, Cr, and B). The results obtained indicate that the pyrolysis at 300 °C and 30 min are the optimal conditions giving high yield of charcoal about 45% which contains up to 94% of Cu, 100% of Cr and 88% of B. After pyrolysis process, the charcoal has been converted into bio-oil using hydroliquefaction process. The optimization approach for the yield of bio-oil using a complete factorial design with three parameters: charcoal/solvent, temperature and hydrogen pressure was discussed. It is observed that the temperature is the most significant parameter and the optimum yield of bio-oil is around 82%. The metal analysis shows that the metals present in the bio-oil is very negligible.
    No preview · Article · May 2012 · Bioresource Technology
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