Evaluating the Trade-Off Between Energy Efficiency and Energy Saving in Spray Drying Operations

In this study, modelling simulations were employed to analyze the effects of inlet drying air flow rate and temperature, product feed rate, and heat recovery ratio in a spray dryer. The energy efficiency, energy savings, and final product outlet temperature were investigated. As the heat recovery ratio (by-pass ratio) increased, total energy savings improved, though energy efficiency declined at a slower rate compared to energy savings. The modelling study, conducted with five different by-pass ratios (100%, 70%, 50%, 30%, and 0%), indicated that the optimal by-pass ratio was 30%. At this ratio, energy efficiency decreased by 5%, while energy savings increased by approximately 16%. Additionally, at higher by-pass ratios, the product outlet temperature rose significantly. To maintain product quality, it was found that the maximum acceptable temperature of 60°C could be achieved at by-pass ratios of 40% or lower.