(321a) Gasification of Organic Solid Waste Under High-Flux Solar Irradiation: Thermodynamics, Kinetics, and Fixed-Bed Reactor Evaluation

Conventional autothermal gasification processes are driven by heat derived from combustion of a portion of feedstock. Combustion generates byproducts, which contaminate the product synthesis gas (syngas) ‒ a mixture mainly consisting of H₂ and CO. The advantages of solar-driven gasification as a means of upgrading carbonaceous feedstocks to syngas were demonstrated in prior work in the field. Here, we present a study of solar thermal dry gasification of organic waste including thermodynamics, chemical kinetics and design, fabrication and evaluation of a 2 kW_th fixed-bed CO₂ gasifier. Thermodynamic analyses were conducted to explore theoretical efficiency and composition limits of the process. Chemical kinetics of CO₂ gasification were investigated by employing thermogravimetric analysis with selected types of carbonaceous feedstocks including waste wood and sewage sludge. The high-flux solar irradiation tests were performed with a windowless solar gasifier with two concentric silicon carbine cavities: the inner cavity serving as a solar receiver to absorb high-flux solar irradiation and the outer cavity serving as a reactor chamber for gasification. The gasifier tests were performed under simulated sunlight provided by a new multi-source high-flux solar simulator developed at National University of Singapore. The solar flux distribution in the reactor aperture plane was measured by a water-cooled thermogage heat flux sensor and a CCD camera. The effects of CO₂/C ratio and input solar power to the reactor on the carbon conversion, cold gas efficiency, and solar-to-fuel efficiency were experimentally explored.