Pyrolysis of chromated copper arsenate (CCA) treated wood waste at elevated pressure: Influence of particle size, heating rate, residence time, temperature and pressure

Abstract

a b s t r a c tLab-scale pyrolysis experiments with weathered CCA treated wood chips have been performed and the influence of particle size, residence time (10-40 min), heating rate (5-20 • C/min), temperature (330-430 • C) and pressure (0 bar, 5 bar) has been investigated. Few data, covering the pyrolysis of weathered wood was found in the literature and the literature data on pyrolysis experiments with a controlled CCA wood input, showed that results were often highly affected by experimental uncertainty. In order to reduce the uncertainty on the results, a thorough characterization of the wood input has been performed and a ratio method has been proposed which allows to study the effect of particle size on arsenic and chromium volatilization. Larger wood particles show a higher arsenic and chromium retention during pyrolysis which is attributed to the higher mass transfer resistance in these particles. Residence time has a limited effect on arsenic retentions. Increasing heating rate results in a limited increase in arsenic retentions and a more profound increase in chromium retentions. The latter is attributed to a lower average particle temperature during heating caused by the thermal lag in larger particles. Elevated pressure results in a significant increase of arsenic retentions, which is probably due to higher mass transfer resistance. Increasing temperature results in a slight decrease in arsenic retentions till 390 • C, with a sharp decrease at higher temperatures. Chromium retentions are less affected by increasing temperature, especially at higher temperatures. To conclude, a mechanism is proposed for the volatilization of chromium and arsenic during low temperature pyrolysis of CCA wood. Mass transfer resistance and the formation of As 4 O 6 are crucial for the control of arsenic volatilization, while heat transfer resistance and thermal lag are more important for the control of chromium volatilization.

Fire Promotes Arsenic Mobilization and Rapid Arsenic(III) Formation in Soil via Thermal Alteration of Arsenic-Bearing Iron Oxides

“…The behavior of As in this study to some extent mirrors the findings of Helsen et al (2004) who found reduced gaseous species generated during thermal decomposition of glucose encouraged the reduction of As(V) (as As 2 O 5 ) to As(III). Our findings also accord with previous studies exploring combustion of Copper-Chrome-Arsenate (CCA) treated wood (Wasson et al, 2005) and Pteris vittata (Yan et al, 2008), in which pyrolysis was reported to drive partial reduction of As(V) to As(III) and cause partial volatilization of As(III) at temperatures >400 • C (Helsen et al, 2003;Cuypers and Helsen, 2011). In addition, pyrolysis of organic matter at temperatures ≤500 • C can cause reduction of other transition metals, including Cu and Ni (Richardson et al, 2010;Liu et al, 2012).…”

Arsenic transformation behaviour during thermal decomposition of P. vittata, an arsenic hyperaccumulator

“…At 600℃, around 60% of the arsenic was released under both pyrolysis and gasification process, which was in agreement with the former studies. Cuypers et al [43] proved that the arsenic release showed a pronounced increase at temperatures higher than 390℃in the pyrolysis of CCA treated wood. Yan et al [33] in a complimentary study found that nearly 62.5% of the total volatilised arsenic emitted at the incineration temperature occurred below 400℃.…”

Pengaruh Diameter Kanal Pelet Katalis Zeolit Aktif dan Ni-Zeolit terhadap Pirolisis Limbah Batang Pohon Sagu (Metroxylonsp.)

“…Pirolisis dipengaruhi oleh ukuran partikel, laju pemanasan, waktu, suhu serta tekanan [3]. Pirolisis pada temperatur 400 0 C merupakan metode yang baik karena memaksimalkan senyawa lignin dan selulosa dari tumbuhan untuk menghasilkan bahan bakar cair [2].…”