Mathematical Modelling and Sensitivity-Based Optimization of Energy-Efficient Cassava Drying in Ghana

Abstract

Pneumatic flash drying of cassava mash is a critical, energy-intensive unit operation among small- and medium-scale agro-processors in Ghana. While operational adjustments such as feed-rate tuning have demonstrated significant energy reductions in empirical trials, the stability of optimized operating points under shifting inlet conditions remains poorly quantified. This paper presents a thermodynamic and psychrometric mass-and-energy balance model tailored to small-scale Ghanaian pneumatic flash dryers. Benchmarked against commercial field trials (where feed-rate tuning increased dried-product output from 42.2 ± 7.3 to 65.0 ± 5.5 kg/h and reduced specific energy consumption from 4,388 ± 716 to 3,509 ± 527 kJ/kg water), the model investigates system sensitivity across fluctuating raw cassava moisture (0.40 ≤ Xi ≤ 0.60 kg/kg db) and feed rates (40 ≤ Fw ≤ 110 kg/h). The sensitivity analysis demonstrates that the reported optimal feed rate of 98.6 kg/h is strictly constrained by an exhaust air relative humidity threshold (RHout ≤ 55.3%) to prevent in-duct condensation and product caking. An increase in initial cassava moisture of 0.05 kg/kg shifts the minimum achievable specific energy consumption point downward in throughput by approximately 8.4 kg/h. A generalized operational decision matrix is proposed to enable local operators to dynamically adjust dryer settings to seasonal moisture variations.