Oxidative Torrefaction of Phragmites australis: Gas-Pressurized Effects and Correlation Analysis Based on Color Value

Abstract

In this study, atmospheric (AP) and gas-pressurized (GP) torrefaction of Phragmites australis (PAS) were carried out in a rotary tube furnace and a gas-pressurized autoclave, respectively, aiming to investigate the effects of torrefaction pressure on the physicochemical properties and combustion characteristics of torrefied PAS. The organic components of liquid products were also analyzed. Compared with AP torrefied PAS, GP torrefied PAS had a higher weight loss, higher heating value (HHV), lignin content, lower ash content, and atomic O/C and H/C ratios. In addition, GP torrefied PAS had better hydrophobicity, representing a stronger storage capability in humid environments. The organic components of liquid products derived from AP torrefaction were mainly aldehydes, ketones, phenols, and furans, while those from GP torrefaction were mainly phenols, acids, ketones, and alcohols. GP torrefied PAS contained a higher combustion stability and better fuel properties than AP torrefied PAS. The color of GP torrefied PAS was significantly darker than that of AP torrefied PAS, and the weight loss, volatile matter (VM) content, and HHV of AP and GP torrefied PAS showed good correlations with the color parameters. This study innovatively carried out torrefaction in a pressurized atmosphere and used color parameters to establish a model to predict the quality of torrefied products; the results could be applied directly to guide the further development of wetland biomass upgrading and products quality controlling.

Effect of Torrefaction Conditions on Physical and Thermal Properties of High- and Low- Quality Palm Pruning Residue Pellets

“…2 that the colors of both highand low-quality pellets darken with the increase in the torrefaction temperature and residence time. This is consistent with the results of the previous studies [41,42]. It can be also seen from Fig.…”

“…It has been reported in previous studies that the reasons for the darkening of the torrefied biomass may be the lignocellulosic structure of the material, the surface properties of the biomass, the sugar molecule content, and the Maillard reaction [42,45]. In this study, torrefaction process is more effective in HQ pellets with low moisture content than LQ pellets with high moisture content.…”

Combining Oxidative Torrefaction and Pyrolysis of Phragmites australis: Improvement of the Adsorption Capacity of Biochar for Tetracycline

“…The higher TC adsorption capacity of TPBC than of PBC was the result of torrefaction pretreatment. In the oxidative process, devolatilization and thermal decomposition of PAS and oxidation reactions occur, resulting in better physicochemical properties of oxidatively torrefied PAS (Huang et al, 2020). Therefore, after the subsequent pyrolysis process, the obtained TPBC had a higher specific surface area, stronger hydrophobicity, and lower ash content, which led to a higher TC adsorption capacity.…”

Virtual Special Issue of Recent Research Advances in China: Thermochemical Processing of Biomass and Solid Wastes

“…Ahmad et al 10 investigate the effect of the treatment temperature on properties of hydrochars using P-and N-enriched agricultural and antibiotic residues as feedstocks via microwave-assisted hydrothermal conversion. Huang et al 11 study the effects of torrefaction pressure on the physicochemical properties and combustion characteristics of torrefied Phragmites australis. Liu et al 12 report the pyrolytic behavior of pubescent samples pretreated by MgCl 2 solution and HCl solution at room temperature and the properties of obtained bio-oil.…”