Maximum Fluidized Bed Boiler Temperature Determination for Coal–Biomass Combustion Condition Through Ash Area Reduction Technique

The residue of the so-called fibrous seed from the açai fruit represents 70% of the mass of the fruit and has potential for useful energy generation. Evaluating and treating the residue as a renewable fuel offers both economic and environmental benefits, whereas today, it is disposed of as organic waste. The co-firing of the fibrous seed and coal in fluidized bed boilers is an attractive option due to the high efficiency of the combustion process and the low bed temperature. However, one of the issues for this application is the low seed ash sintering temperature, which promotes the agglomeration of the bed material. This work aims to present a new procedure for evaluating the sintering temperature of açai seed and coal ash, making it simpler and consistent with traditional techniques. The proposed procedure for determining the starting ash sintering temperature is based on two simple and dynamic methodologies: simultaneous thermal analysis (STA) and sintering by an area reduction in ash samples. The data obtained allow us to determine that the coal ash begins to sinter at around 1000 °C, while the açai seed ash starts at around 700–850 °C, exhibiting a significant area reduction.