Solar Hydrothermal Processing of Biomass: Influence of Temperature and Pressure on the Fuels
Abstract
Before the extended use of fossil fuels, biomass was the main source of energy. Nowadays, there is an interest on using it for the production of different energetic materials, as well as added value substances. In order to obtain these products, biomass has to be transformed trough thermochemical conversion process. Thermochemical biomass conversion processes present attractive options due to their ability to produce fuels quickly, along with the ability to decompose most biomass compounds, such as lignin. Hydrothermal processing (HTP) is a promising technology for being carried out at lower temperatures than pyrolysis and gasification and utilizing wet material up to 70% humidity content, saving biomass drying. However, one concern is that HTP typically uses fossil-generated electricity for heating. Therefore, to reduce its environmental impact, concentrated solar energy has been proposed as a heat source. In the present work, hydrothermal liquefaction of agave bagasse was performed in a solar furnace of 25kW. The experiments were carried out in a solar reactor specifically designed to work at maximum conditions of 220 bar and 500°C. The experiments were carried out with heating rate of 2°C/min. They considered different operational parameters of temperature (150, 200, 250 and 300°C), initial pressure (10, 30 and 50 bar), residence time (0, 30, 60, and 90 min), as well as biomass ratio (5, 10, 15 and 20 wt. %). The main results indicate that at lower temperatures of 250°C, a bio-oil with better energetic properties than that obtained by conventional pyrolysis at 450°C can be accomplished.