Novel vertical image furnace for fast pyrolysis studies

The image furnace is used to mimic experimentally heating conditions representative of a fluidized bed biomass gasifier. The aim of this paper is to demonstrate the feasibility of heat flux density modulation with a new improved vertical image furnace which is based on the former horizontal setup. This is achieved through the comparison of the experimental and theoretical surfaces temperatures evolutions. A numerical model is solved in order to estimate the theoretical surface temperature evolution of a char particle immersed in a fluidized bed at 1123 K. The goal of the experiments performed with char samples is to reproduce the same temperature evolutions. The surface temperatures profiles are measured by pyrometry in different conditions (constant heat flux density, variation of the heat flux density over time) and compared to the modelling results. The experiments at constant heat flux density show poor agreement with the model, in comparison with experiments made with variable heat flux density. The best agreement is obtained when the heat flux density is decreased from 560 kW m−2 to 250 kW m−2 in 1 s after a period of 500 ms.