The influence of torrefaction on the biochar characteristics produced from sesame stalks and bean husk

Abstract

Torrefaction encourages homogeneity and enhances the energy-producing capabilities of biomass. In the current study, bean husk (BH) and sesame stalks (SS) were torrefied for 30 and 60 min at operating temperatures of 200, 225, 250 and 275, and 300 °C with nitrogen purging. Mass yield (MY), higher heating value (HHV), energy yields (EY), and torrefaction severity index (TSI) were examined. The variations of the biochar characteristics, pyrolysis kinetics by applying two models (Coats and Redfern (CR) and Direct Arrhenius (DA)), and crystallinity index (CRI) were depicted. Depending on pyrolysis kinetics, thermodynamic activation parameters were derived to elucidate biomass pyrolysis. The alterations in the torrefied materials’ composition were also analyzed using Fourier transform infrared spectroscopy (FTIR). The calculations revealed that the torrefied SS and BH decreased MY by 32.74, 29.02% and decreased EY 26, 20.97%, increased high heating values by 14.1, 13.52%, increased fixed carbon by 55.1, 39.91% respectively, and had a slight reduction in bulk density (approximately 2%). Generally, 275 °C and 30 min were the optimal conditions for a balanced torrefaction of SS and BH based on the HHV that reached to 20.5, 16.2 MJ/kg and EY that reached to 86.16 and 85.56% respectively. The FTIR, XRD, and the thermogravimetric results showed that the torrefaction treatment altered samples owing to carbohydrate breakdown, a rise in lignin, and a reduction in hemicellulose as the temperature of the torrefaction process increased. The CR methodology yielded greater frequency factor (A) and activation energy (Ea) values than the DA method. The broadest peak width, lowest average Ea, and lnA were seen in sesame stalks that had been torrefied at 300 °C and 30 min that reached to 107.85 (kJ/mol) and 13.57 (min−1). Results indicated an excellent linear relationship with the index of comprehensive pyrolysis (CPI), CRI, atomic H/C ratio, severity index, and EY.

A novel solar disk chamber reactor for agricultural waste recycling and biochar production

“…It is confirmed that the highest temperature and residence time of the torrefaction method for sesame stalk biochar production (generated from 200 to 300 °C for 30 and 60 min) produced the highest carbon mass fraction (55.77%) and fixed carbon (55.10%). On the other hand, biochar yield, oxygen content, and hydrogen content declined to their lowest values with increasing temperatures, resulting in decreased H/C and O/C molar ratios due to the decay of hemicellulosic and cellulosic compounds (Khairy et al 2023). Park et al (2015) detected a similar observation by studying the effect of pyrolysis temperature on the sesame biochar characteristics and its phosphorus release.…”

“…The moisture content of SS was relatively low, less than 10%. This percentage is favorable for the pyrolysis process (Khairy et al 2023). However, the moisture contents of both T1 and T2 were relatively close and lower than SS by about 50%.…”

Biochar from Lignocellulosic Biomass: The Importance of Physicochemical Characterization and Multi-Criteria Decision Analysis for Its Applications

“…Biochar O/C -0.12; Biochar H/C -0.66; HHV-25.73 MJ kg -1 ; Energy yield -47.52%; Fuel Ratio -5.87; Thermal stability -0.85.Biochar O/C -0.64; Biochar H/C -1.25; HHV-20.5 MJ kg -1 ; Biochar yield -76.25%; Fuel Ratio -0.52;[119] …”