High temperature pyrolysis of solid products obtained from rapid hydrothermal pre-processing of pinewood sawdust

Abstract

A sample of pinewood sawdust was rapidly pre-processed in a torrefaction-type procedure, separately in subcritical water (neutral) and with added Na 2 CO 3 (alkaline compound) and Nb 2 O 5 (solid acid) in a batch reactor. The original sawdust and the three friable solid recovered products from the hydrothermal procedure were characterized in detail. The solid recovered products gave higher C/O and C/H ratios, higher calorific values and reduced moisture contents compared to the original sawdust. The four solid samples were then subjected to rapid high temperature pyrolysis in a fixed-bed reactor to investigate the effect of the pre-processing routes on the yields and compositions of pyrolysis products. With increasing pyrolysis temperature, the pre-processed samples produced more CO and H 2 , far more char and less tar than the original sawdust. The trends in the composition of gases and the yields of char suggested a combination of Boudouard reaction and CO 2 dry reforming as the predominant reactions during pyrolysis. For all samples, increased temperature led to reduced tar production with an increase in the aromatic oxygenates and aromatic hydrocarbons contents of the tar. At 800 °C, the ratio of aromatic hydrocarbons increased dramatically particularly from the sample pre-processed with Nb 2 O 5 indicating possible deoxygenation catalysis.

Sources of Biomass Feedstock Variability and the Potential Impact on Biofuels Production

“…HTL About 50 % of the oxygen rich volatiles can be reduced, leading to greater energy density of the solid char product from pine sawdust hydrothermal preprocessing [40].…”

Catalytic conversion of bio-oil in supercritical water: Influence of RuO2/γ-Al2O3 catalysts on gasification efficiencies and bio-methane production

“…The difference in weight between the solid residue and the ash was taken as the weight of char. Furthermore, the fresh catalysts, the solid residues and the calcined catalyst (ash obtained from the solid residues) were all analysed by an x-ray diffractometer (XRD) to check for the alumina and ruthenium oxide phases [23]. In addition, the fresh catalyst and calcined catalysts were characterised by scanning electron microscope -energy dispersive xray spectroscopy (SEM-EDXS).…”

Key environmental and production factors for understanding variation in switchgrass chemical attributes

“…Upland switchgrass had a minimum of 72% volatiles and a maximum of 84% with most of the variation between location and within the Oklahoma field site (Figure 2a). Higher volatiles are related to increased fuel acidity following pyrolysis (Carpenter et al, 2014), faster burn rates in direct combustion (Jenkins et al, 1998), and decreased energy density of char from HTL (Onwudili et al, 2014). Carbon had location-to-location variation with an overall range of 46%-51% (Figure 2c).…”