Improvement of combustible characteristics of Paulownia leaves via hydrothermal carbonization

Abstract

The Paulownia leaves (PL) was used for the first time as feedstock for the potential production of novel carbon-rich materials applying hydrothermal carbonization (HTC) technology. The HTC is one of the suitable methods for converting biomass into high-value carbonaceous products that could replace existing fossil fuels or be used for some other application. In this study, hydrochars of PL were obtained at five different temperatures (180, 200, 220, 240, and 260 degrees C), and the influence of temperature on hydrochar structures was analyzed. Physicochemical composition, structural, and combustion properties were estimated for hydrochar efficient characterization. The results showed that tested hydrochars had lower moisture, volatiles, oxygen, and sulfur content compared to PL biomass. Also, the HTC process increases carbon content and created high-energy C-C bond structures in hydrochars which improved fuel ratio (FR), energy density (ED), higher heat value (HHV), and lower heating value (LHV). However, hydrochar mass yields were significantly low, which affected the lower heating value (EY). The spectroscopic and thermal analysis confirmed the formation of new aromatic structures in hydrochars and enhancement of their thermal stability and combustion ability, respectively. Before hydrochar practice, in order to enhance their mass yields, it is necessary to further analyze the influence of the HTC parameters or hydrothermal co-carbonization with other biomass should be taken into concern. The results showed that HTC could be an efficient method to improve the combustion properties of PL biomass.