Torrefied Biomass Size for Combustion in Existing Boilers

A fundamental investigation was conducted on the combustion characteristics in air of different torrefied biomass particles size ranges. The targeted biomass types were waste crop, herbaceous and woody. The experimental setup that was used in this investigation consisted of a drop-tube furnace, operated at a wall temperature of 1400 K, and a three-color pyrometer, interfaced with the furnace. Entire luminous particle combustion profiles of individual particles were recorded. Results are compared with relevant past data on the combustion characteristics of single coal particles of different ranks, burned in the same furnace under identical operating conditions. The goal of this work is to identify the appropriate size of torrefied biomass particles whose combustion durations match those of 75-90 μm pulverized coal particles, which is a size typically used in pulverized fuel boilers. Such data will be useful in deciding the fuel sizing for co-firing coal with biomass.

Simulation of Laser Heating of Aluminum and Model Validation via Two-Color Pyrometer and Shape Assessment

The modeling of laser-based processes is increasingly addressed in a competitive environment for two main reasons: Preventing a trial-and-error approach to set the optimum processing conditions and non-destructive real-time control. In this frame, a thermal model for laser heating in the form of non-penetrative bead-on-plate welds of aluminum alloy 2024 is proposed in this paper. A super-Gaussian profile is considered for the transverse optical intensity and a number of laws for temperature-dependent material properties have been included aiming to improve the reliability of the model. The output of the simulation in terms of both thermal evolution of the parent metal and geometry of the fusion zone is validated in comparison with the actual response: namely, a two-color pyrometer is used to infer the thermal history on the exposed surface around the scanning path, whereas the shape and size of the fusion zone are assessed in the transverse cross-section. With an average error of 3% and 4%, the model is capable of predicting the peak temperature and the depth of the fusion zone upon laser heating, respectively. The model is intended to offer a comprehensive description of phenomena in laser heating in preparation for a further model for repairing via additive manufacturing.