Heat and Mass Transfer Effects in a Furnace‐Based Micropyrolyzer

Abstract

Microgram‐scale reactors combined with gas chromatography (GC) coupled to mass spectrometry (MS) or flame ionization detection (FID) are used widely in pyrolysis research. Whether these devices meet the expected fast heating rates and short vapor residence times of fast pyrolysis have not been verified. In this study, experiments and simulations are used to investigate heat and mass transfer in a furnace‐based micropyrolyzer. Surprisingly, heating rates obtained from the temperature history of sample cups in the reactor were modest compared to the greater than 1000 K s−1 heating rates sometimes assumed for such reactors. The heating rate at 773 K, employed commonly in fast pyrolysis, was only 180 K s−1. The highest rate observed was 494 K s−1 at a furnace temperature of 1268 K, which is well above typical pyrolysis temperatures. The mass transfer of volatilized samples was studied using both an optically accessible furnace and computational fluid dynamics. The standard sample cups used with these micropyrolyzers impede the escape of vapors. The use of shallow perforated cups overcame this mass transfer limitation to lead to levoglucosan yields ≈10 % higher than usually reported for the pyrolysis of cellulose.

Measuring biomass fast pyrolysis kinetics: State of the art

“…The two reactors are heated separately in two furnaces, thereby, offering the flexibility in choosing reaction temperatures. The micropyrolyzer reactors are usually coupled with gas chromatography (GC) techniques like GC‐MS, GC‐TOF‐MS (time‐of‐flight mass spectrometer), or GC‐FID (Figure ; Choi, Lee, Zhang, Brown, & Shanks, ; Proano‐Aviles, Lindstrom, Johnston, & Brown, ; Ronsse et al, ). U‐shaped two‐stage tubular reactors, separated by quartz wool, have been reported by Norinaga et al (Kousoku, Norinaga, & Miura, ; Norinaga et al, ; Qi et al, ; Yang et al, ; Yang, Appari, Kudo, Hayashi, & Norinaga, ; Yang, Furutani, Kudo, Hayashi, & Norinaga, ) for intrinsic gas‐phase pyrolysis kinetic studies of cellulose and lignin model compound such as catechol, resorcinol, and hydroquinone pyrolysis.…”

“…Recently, Proano‐Aviles et al () published a detailed experimental study on heat and mass transfer effects in a micropyrolyzer. Various sample holder types were considered to explain the transport effects.…”

Where does the Oxygen go? – Pathways and Partitioning in Autothermal Pyrolysis

“…Even in this sample size range, cellulose powders undergo mass transfer limitations, as demonstrated by observed secondary reactions [78]. Both Zhang et al [78] and Proano-Aviles et al [344] modified pyrolysis cups in response to their findings, to mitigate poor ventilation-induced secondary reactions. These modifications were subsequently adopted by the manufacturer, Figure 12.…”

“…These modifications were subsequently adopted by the manufacturer, Figure 12. [344]; the manufacturer subsequently added two new sample holder designs incorporating these modifications [343].) Figure 13.…”

“…Sample holders utilized in the micropyrolyzer. Dimensions in mm, figure borrowed with permission from Proano-Aviles [344].…”