Vliv draslíku na termickou degradaci biomasy

Abstract

The dissertation thesis provides an overview of thermal conversion technologies for biomass with potassium additives using changes in temperature, pressure, and heating rate. Thermochemical conversion represents the most economical approach to energy recovery using biomass fuels. The theoretical part of the work includes literature data on thermochemical decomposition processes for common biomass species and waste biomass. In the next section, information on the potassium-based additives used and their influence on decomposition products and thermochemical processes is summarized. Attention is paid to hydrothermal carbonisation (180–250 °C), torrefaction (200–300 °C), slow pyrolysis (300–700 °C), fast pyrolysis (400–800 °C), flash pyrolysis (800–1000 °C), gasification (800–1000 °C) and combustion. The products of thermochemical conversion (biochar, oil, and gases) should be reused, allowing a reduction in the consumption of non-renewable fuels. Potassium (K) is an element that is often present in biomass. From information in the literature, it is known to affect the degradation of lignocellulosic biomass. Therefore, a full understanding of the role of potassium during thermal degradation of biomass is necessary to predict the thermal behaviour of biomass. For this purpose, biomass samples were impregnated with K2CO3 at different concentrations (0.1, 0.3, and 0.9 wt.%). Simulations of combustion, torrefaction, and pyrolysis were performed on a thermogravimetric analyzer (TG/DSC2 Mettler Toledo) followed by an evaluation of the thermal degradation process at different temperatures. The laboratory experimental pyrolysis equipment of ENET Centre was used to obtain information on the yield of the different products of thermochemical conversion (gas, solid product, and bio-oil). The chemical analysis of the functional groups bound to biochar obtained from the thermal conversion of biomass was carried out by FTIR spectroscopy using the attenuated total reflection (ATR) method using an FTIR spectrometer (Nicolet 6700). The results obtained provide new insight into the importance of potassium in the thermal conversion of biomass with a better understanding of the decomposition mechanisms. The effect of potassium impregnation on biomass torefaction is almost imperceptible at lower temperatures, while the catalytic effect of potassium is evident at higher torefaction temperatures (250 °C). For the same mass loss in the temperature range 200–300 °C, at least 28% and up to 93% time savings can be achieved when biomass is treated with potassium. This information could help to reduce the operating time and/or temperature, making torrefaction a green method of waste biomass recovery.