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Sida hermaphrodita is one of the energy crops with high potential for energy conversion technologies. In this study the torrefaction of Sida hermaphrodita was carried out at the specially constructed test bench simulating industrial like process operating conditions. The torrefaction temperature was in the range from 250 to 350 °C. The obtained solid products (biochars) were characterized in terms of its proximate and ultimate properties. The chemical analysis of liquid phase was also performed. The combustion process of obtained biochars was examined by Simultaneous Thermal Analysis (STA) through dynamic runs at 10 °C/min heating rate from RT to 700 °C. The structural changes during the torrefaction were studied using scanning electron microscope technique. The fibre analysis was performed to determine structural composition (the content of hemicellulose, cellulose and lignin). Results from analyses significantly contributed to extending databases in the field of plant torrefaction. The results confirmed positive features of obtained biochars comparing to raw biomass material. It was concluded, that the optimal process temperature for Sida hermaphrodita should not exceed 400 °C. Additionally, the mineral matter was investigated using X-ray Fluorescence (XRF) to study the influence of torrefaction on chemical composition of the ash. Only some differences in ash compounds were observed. • Sida Hermaphrodita torrefaction process were conducted at specified temperatures. • Increasing process temperature leads to enhance energy properties of obtained biochar. • The fibre and structural analyses confirmed the changes in morphology structure. • Condensates of torrefaction contained high amount of organics. [ABSTRACT FROM AUTHOR]

Abstract The main problem and also challenge was to find a satisfactory effective tool for real-time control the torrefaction/pyrolysis process of biomass and to evaluate (also in real-time conditions) biochar quality. This paper presents results from investigation on a new method for both evaluating biochar quality and control biomass thermal processing at temperatures of 300, 350 and 400 ◦ C. Thermal processing of biomass in this temperature range is torrefaction and pyrolysis. Investigation was focused on processing Virginia Mallow (Sida Hermaphrodita) energetic crops. Several strong correlations were observed as follows: carbon and hydrogen content in biochar (charcoal), oxygen content, ash and volatile matter from biochar, calorific value and temperature of the process and finally, acetic acid in condensate and carbon content in the biochar. The results show that the content of acetic acid, being one of the major compounds present in the condensate (black liquor, biooil), is in satisfactory linear correlation with the process temperature and furthermore, with carbon content in biochar. The mathematical description for this polynomial function was proposed as follows: Carbon (%) = 0.6e-3 x Acetic Acid (ppm)+49.5. The correlation between acetic acid in black liquor and carbon in biochar was used to introduce a new method which can be considered as a diagnostic tool for determining biochar quality in real-time conditions during biomass thermal processing. Hence, carbon content in biochar as well as its calorific value can be determined by measuring percentage of acetic acid in the condensate. This correlation was considered as the main novelty presented here. This method provides relatively fast evaluation of quality of biochar produced in industrial scale torrefaction systems, what makes it possible to optimize process parameters (temperature, retention time) in real time conditions and improve biochar production process in this way. Highlights • C H tradeoff for biochar is in strong linear negative correlation. • Acetic acid in biooil increased from 5 to 25% with process temperature increase. • Acetic acid in biooil is verifiable correlated with carbon content in biochar. • Acetic acid vs. carbon correlation can be used to control biochar quality. [ABSTRACT FROM AUTHOR]

A novel approach, linking both experiments and modelling, was applied to obtain a better understanding of combustion characteristics of torrefied biomass. Therefore, Pine, Acacia and Miscanthus giganteus have been investigated under 260 °C, 1 h residence time and argon atmosphere. A higher heating value and carbon content corresponding to a higher fixed carbon, lower volatile matter, moisture content, and ratio O/C were obtained for all torrefied biomass. TGA analysis was used in order to proceed with the kinetics study and Chemkin calculations. The kinetics analysis demonstrated that the torrefaction process led to a decrease in Ea compared to raw biomass. The average Ea of pine using the KAS method changed from 169.42 to 122.88 kJ/mol. The changes in gaseous products of combustion were calculated by Chemkin, which corresponded with the TGA results. The general conclusion based on these investigations is that torrefaction improves the physical and chemical properties of biomass. [ABSTRACT FROM AUTHOR]