Numerical Analysis of Coffee Husk Combustion
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Date
2025-06
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Addis Ababa University
Abstract
Coffee husk, the primary byproduct generated during coffee processing, presents a promising opportunity as a renewable energy source, particularly in regions with high coffee production like Ethiopia. Despite its abundance and energy potential, coffee husk remains underutilized—especially in direct combustion systems, where its combustion behavior and environmental impacts have not been thoroughly studied. This study focuses on the numerical simulation of coffee husk combustion within a biomass furnace using ANSYS Fluent. The main objectives is to design a combustion chamber geometry, to investigate the influence of excess air on combustion characteristics, to study the effects of the position of the secondary air inlet and to analyze the environmental impact of the combustion process, with a specific focus on carbon monoxide (CO) emissions.
The simulation was carried out by developing a 2D furnace model and applying appropriate boundary conditions, turbulence models and chemical kinetics. Coffee husk properties is defined based on available literature, with an emphasis on gas-phase combustion of volatiles and gas released from char combustion. Results indicate that excess air significantly affects combustion temperature and CO emission levels. The analysis shows that 60% excess air provides a average outlet temperature of 1295 k with nearly zero carbon monoxide emissions. Furthermore, the location of the secondary air inlet played a critical role in enhancing mixing, while both fuel flow rate and excess air had a direct influence on temperature distribution and emission concentration. The numerical model was validated using experimental data from rice husk combustion, chosen due to its similarity to coffee husk. The flue gas temperatures showed good agreement, with only a 2.2% deviation at 35% excess air. Although the variation increased with higher excess air levels, all deviations remained within an acceptable range.
In conclusion, the study demonstrates that coffee husk can be effectively utilized in direct combustion systems with controlled operating parameters. The findings provide valuable insights for sustainable energy production in coffee-producing regions and open doors for further research in this area.
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Coffee husk Combustion Numerical Simulation Chemical Kinetics