Optimizing biomass briquette drying: A computational fluid dynamics approach with a case study in Mozambique

Abstract

Biomass fuels remain the primary cooking energy source in many developing regions, contributing to deforestation and greenhouse gas emissions. Briquettes made from waste biomass are a sustainable alternative; however, their production is hindered by inefficient drying methods, such as open sun drying, which can take 5 to 7 days. This study evaluates the thermal and airflow performance of a solar tunnel dryer (STD) designed to accelerate drying times for charcoal briquettes under Mozambique's climatic conditions. Using Computational Fluid Dynamics (CFD) simulations, temperature and airflow distributions were analyzed to optimize dryer performance. Moisture and temperature profiles of hexagonal briquettes with inner holes indicated effective drying, achieving uniform moisture reduction to 10 % from an initial 50 %. Drying time was projected based on simulated airflow and temperature conditions, showing a significant reduction compared to traditional methods. The STD, operating with air temperatures of 36.5 °C to 65 °C and velocities up to 33.5 m/s at a mass flow rate of 1.36 kg/s, demonstrated its potential to enhance briquette production efficiency while maintaining environmental sustainability. The findings underscore the viability of solar drying technology for biomass fuel processing. • CFD simulations optimize airflow and drying in a solar tunnel dryer for charcoal briquettes. • Solar dryer design reduces drying time and energy consumption versus open sun drying • Real briquette geometry and climate data from Mozambique used in 3D simulations. • Results show uniform temperature distribution, improving briquette drying efficiency. • Simulated airflow patterns reveal reduced turbulence and enhance drying rates.