Greenhouse gas emission reduction potential, energy and exergy analysis of combined microwave-convective dryer

Abstract

About 12–25% of the energy used in the food processing industries in the drying section and various technologies such as the combination of microwave and convective methods has been applied to reduce greenhouse gases and environmental pollution effects. In this study, the effects of microwave power (200–500 W) and drying air temperatures (30–55 °C) on energy and exergy aspects, GHG emissions (CO2, SO2, and NOx), and GHG reduction potential were evaluated and optimized using genetic algorithm approach in a combined microwave-convective drying process. The results showed that higher drying air temperature caused an increasing energy loss and decreasing exergy efficiency. The energy and exergy efficiencies were found to be in the range of 5.20–23.50% and 5.12–9.19%, respectively. The exergy improvement potential and GHG emissions decreased with increasing microwave power and decreasing drying air temperature. The total GHG emissions varied between 2002.4 and 7627.4 (g/kg water). Optimization of the drying parameters for the given constraints resulted in 498 W and 30.2 °C. The GHG emissions can be reduced 14.1%–28.6% with a recovery of exergy loss. Therefore, it can be concluded that heat recovery mechanisms are needed to reduce exergy waste and GHG emissions.