The Effects of Particle Size, Different Corn Stover Components, and Gas Residence Time on Torrefaction of Corn Stover

Abstract

Large scale biofuel production will be possible only if significant quantities of biomass feedstock can be stored, transported, and processed in an economic and sustainable manner. Torrefaction has the potential to significantly reduce the cost of transportation, storage, and downstream processing through the improvement of physical and chemical characteristics of biomass. The main objective of this study was to investigate the effects of particle size, plant components, and gas residence time on the production of torrefied corn (Zea mays) stover. Different particle sizes included 0.85 mm and 20 mm. Different stover components included ground corn stover, whole corn stalk, stalk shell and pith, and corn cob shell. Three different purge gas residence times were employed to assess the effects of interaction of volatiles and torrefied biomass. Elemental analyses were performed on all of the samples, and the data obtained was used to estimate the energy contents and energy yields of different torrefied biomass samples. Particle density, elemental composition, and fiber composition of raw biomass fractions were also determined. Stalk pith torrefied at 280 °C and stalk shell torrefied at 250 °C had highest and lowest dry matter loss, of about 44% and 13%, respectively. Stalk pith torrefied at 250 °C had lowest energy density of about 18-18.5 MJ/kg, while cob shell torrefied at 280 °C had the highest energy density of about 21.5 MJ/kg. The lowest energy yield, at 59%, was recorded for stalk pith torrefied at 280 °C, whereas cob and stalk shell torrefied at 250 °C had highest energy yield at 85%. These differences were a consequence of the differences in particle densities, hemicellulose quantities, and chemical properties of the OPEN ACCESSEnergies 2012, 5 1200 original biomass samples. Gas residence time did not have a significant effect on the aforementioned parameters.

Corn Cob as a Potential Feedstock for Slow Pyrolysis of Biomass

“…40 The feedstock with high lignin content could produce higher char yield during the pyrolysis process. The results of lignocellulosic content of corn cob from this study is consistent with the findings reported by Demirbas 23 and Medic et al 24 as presented in Table 2 where the cellulose is the main component of corn cob feedstock. The different locations of sample collection may result in slight variation of the chemical properties due to their diverse origin and species.…”

“…For the lignocellulosic component, it was observed that the corn cob feedstock contained higher hemicellulose of 39.3% and lower cellulose and lignin, 28.75% and 19.6% respectively. However, Demirbas 23 and Medic et al 24 found that cellulose is the main lignocellulosic component in the corn cob; 52 daf wt% and 45.2 wt% respectively. The percentage of C, H, N, S and O are determined from the elemental analysis.…”

Effect of Torrefaction on the Properties of Corn Stalk to Enhance Solid Fuel Qualities

“…One is moisture loss, with the other being thermal decomposition to form volatile gaseous products such as H 2 O, CO, CO 2 , acetic acid and other organics [16]. The reduction in the mass yield is attributed to the thermal effects which resulted in the loss of moisture, followed by the depolymerization of the secondary cell-wall constituents, i.e., hemicellulose, cellulose and lignin [18]. The decrease in mass during torrefaction at a lower temperature is thought to be mainly caused by the loss of moisture.…”

Some Chemical Compositional Changes in Miscanthus and White Oak Sawdust Samples during Torrefaction

“…In addition, it has been noted that torrefaction of biomass not only increases biomass energy properties, but produces some higher hydrocarbons as well, which can typically be used for producing chemicals or for improving overall energy efficiency [31]. Some recent experimental and techno-economical studies on torrefaction include: (a) the effects of particle size, different corn stover components, and gas residence times on the torrefaction of corn stover by Medic et al [32]; (b) the techno-economic analysis of a production-scale torrefaction system for cellulosic biomass upgrading by Shah et al [33]; (c) biomass upgrading by torrefaction for the production of biofuels by van der Stelt et al [34]; (d) the study of particle size effect on biomass torrefaction and densification by Peng et al [35]; (e) recent advances in biomass pretreatment, torrefaction fundamentals, and technology by Chew and Doshi [36]; and (f) studies by Tumuluru et al [37] on the response surface analysis of elemental composition and energy properties of corn stover during torrefaction. In general, response surface methodology (RSM) is the commonly used method to understand the effect of process variables on the product properties.…”