Energy Recovery Based on Exhaust Gas Recirculation and Heat Regeneration Processes Applied in a Firewood Boiler

This research investigated the exhaust gas recirculation (EGR) process to recover part of the thermal and chemical energy left in the exhaust boiler stream. A theoretical energy conversion and use analysis was performed based on a small boiler. Several measurements and analyses of the operation reports provided the boundary conditions and relevant information for modelling the processes. The methodology considered the radiation from exhaust gases, thermodynamics balances, and financial engineering calculations for the energy recovery analysis. Financial results indicate that the exhaust gas recirculation process implementation, regarding 20% of the EGR ratio, presented 69% and 1.45 years of internal returning rate and payback, respectively. However, the regenerative process presented an internal returning rate and payback values of 112% and 0.9 years. Indeed, both processes might be applied in order to increase efficiency and reduce emissions.