A New Method for Direct Determination of Char Yield during Solid Fuel Pyrolysis in Drop-Tube Furnace at High Temperature and Its Comparison with Ash Tracer Method

Abstract

A drop-tube furnace with a novel double-tube configuration was successfully developed to directly determine char yields during the pyrolysis of a wide range of solid fuels (mallee wood; mallee leaf; rice husk; biosolid; and subbituminous, bituminous, and anthracite coal) at a gas temperature of 1573 K. The char yield from pyrolysis of mallee wood and mallee leaf is <5%, ∼13% for rice husk, ∼16% for biosolid, ∼45% for subbituminous and bituminous coal, and ∼75% for anthracite coal. The retentions of Na, K, Mg, and Ca in biomass chars are <50%. About 35% of Na and K and ∼66–85% of P and refractory species in biosolid are retained in the char. In contrast, the retentions of major inorganic species in coal chars are >85%. This study shows using total ash as ash tracer results in 45–220% overestimation of char yields for biomass fuels and 13–27% for coals due to partial evaporation of ash. Similarly, selecting Na and K results in overestimation of biomass char yields by at least 2.5 times and selecting P leads to overestimation of biomass char yields by at least 80% because of substantial release of these species during pyrolysis. Similarly, selecting Mg, Ca, Al, Fe, Ti, or Si as tracer also results in inaccurate estimation of char yields due to partial release of these elements during pyrolysis. It is noted that for Si, which is often used as a tracer, the overestimation of char yields is 9–16% for coals but can be substantial (17–50%) for the case of biomass samples because of the substantial Si release during the pyrolysis of biomass (especially mallee wood with ∼32% of Si released). Clearly, for the solid fuels studied, no single element can be reliably used as tracer for calculating char yield during pyrolysis at high temperature. The new experimental method developed in this study fills this critical gap and enables direct determination of char yield during solid fuel pyrolysis in drop-tube furnace at high temperature.

HTC of Wet Residues of the Brewing Process: Comprehensive Characterization of Produced Beer, Spent Grain and Valorized Residues

“…For the results obtained by Weber method, it seems plausible to suspect that the difference was caused by the fact that inorganic content was affected to the greatest extent by the HTC process, performed at relatively long residence time. Both ash tracer method and Weber method, are based on the assumption that all of the ash, originally present in valorized biomass, remains in the solid product [49,63]. However, the Weber method compares the content of ash and fixed carbon combined, thus making the influence of any loss of inorganic part from solid fraction smaller [49].…”

“…where: Ym-mass yield (further part of the subscript indicating a method); VM-respective volatile matter content of feedstock and product, % dry Moreover, the mass yield was also assessed, using well-established ash tracer method, used for indirect assessment of mass losses, during various thermal conversion processes [63]:…”

Evaluation of devolatilization behaviour of different carbonaceous materials under rapid heating for the novel HIsarna ironmaking process

“…The isothermal plug flow reactor (IPFR) was used to study the effect of rapid heating on biomass material with three torrefaction degrees, the reactivity of the chars was determined by calculating weight loss through the ash tracer method and it was found that the biomass with higher torrefaction has lower reactivity [32]. The filament platinum pyrolyzer [31], custom made thermogravimetric analysis (TGA) furnace [33] and the drop tube furnace method [13], [26]- [29], [34], [35] have all been used to produce chars through rapid heating to different final temperatures. The solid char particles produced via these experimental techniques were used for further analysis to investigate the effect of different rapid heating conditions on char formation.…”

Charcoal as an Alternative Reductant in Ferroalloy Production: A Review

“…Charcoal from fast pyrolysis exhibits a higher volatile matter content compared to slow pyrolysis char produced at same temperature [172]. The charcoal yield of wood and herbaceous biomass decreases to less than 4% on dry ash free basis at temperatures above 1000 • C [173,174], whereas the formation of soot increases at temperatures larger than 900 • C with a maximum yield between 1100 to 1250 • C [97,175]. Biomass with a high lignin content will form larger soot yields compared to biomass which is enriched in cellulose or xylan content [171,176], in which the soot and tar formation is reduced by high concentrations of alkali metals.…”