Experiment and modeling study of particle spectral emittance in concentrated solar biomass thermochemical conversion

The integration of solar thermochemical conversion with biomass gasification offers significant potential for achieving high-efficiency solar-to-chemical energy conversion. The thermal radiation characteristics of biomass directly influence its ability to capture and utilize solar radiation; however, previous studies often simplified biomass as a gray body, neglecting the complex physicochemical transformations occurring during pyrolysis and gasification that substantially alter its radiative properties. To address this gap, this study employed a self-developed platform for indirect emittance measurement to investigate three biomass samples. Samples representing different reaction stages of pyrolysis and gasification were prepared, and their spectral emittance was measured across the solar radiation waveband (0.3–2.5 μm). The results indicate that as the pyrolysis temperature increased, the total solar absorptance of biomass samples increased sharply from 0.49 to 0.90, thereby significantly enhancing their radiative absorption capacity. Ash content exhibited a pronounced inhibitory effect on emittance, particularly during gasification, where the high-ash wheat sample (29.44 %) displayed the lowest emittance. During gasification, all samples maintained high absorption capacity, with the emittance ranged from 0.87 to 0.93 in 0.3–2.5 μm. Based on the observed influences of reaction stage, ash content, and wavelength on emittance, two sixth-order emittance models were developed for pyrolysis and gasification. These models achieved low prediction errors of 1.20 × 10⁻³ and 4.05 × 10⁻⁵, respectively. This study provides valuable insights into the thermal radiative behavior of biomass and supports more accurate modeling of solar-driven pyrolysis and gasification processes.