Design of a waste-based heat recovery system for industrial baking ovens at a large-scale food facility

Abstract

Food manufacturing facilities are a crucial industry for many national economies. However, maintaining a sterile, clean environment they require also demand large amounts of energy and fuel, necessitating in-depth scientific studies to conserve energy in such complex environments. This study designed a unique, large-scale, and industrial-level waste heat recovery (WHR) system with an 18-month implementation within 15 tunnel ovens at a Biscuits and Wafers Industry (BWI) plant in Yemen, a country facing multiple energy challenges. Initial measurements indicated that up to 60% of thermal energy was delivered within the exhaust gases at 150–250 ℃, with a cumulative waste energy of up to 6,000 MWh/year. To overcome this, modular heat pipe systems with deionized water and a sintered copper wick were incorporated to preheat combustion air. Material integrity was verified through Helium leak testing (<1*10−9 mbar*L/s) and monthly ATP bioluminescence swabbing (<10 RLU), providing empirical evidence of zero cross-contamination and HACCP compliance. The proposed system had thermal efficiencies (η) of 36–42%, and exergy efficiencies (ψ) of 22–28%, indicating that an energy saving of more than 3,000 MWh/year and a reduction of about 650 t CO2 emissions could be achieved. Economic analysis resulted in a very competitive simple payback period of 4.1–4.6 years and an Internal Rate of Return (IRR) of 20–22.3%. Besides, the proposed design also offers validated design parameters and SCADA-based control strategies to scale up carbon-neutral thermal recovery in the global food manufacturing industry. It also provides economic standards and operational values for wider industry applications.