Preliminary study to validate practicality of Heat Recovery Boilers with Water Spray (HR-B/WS)

This paper introduces a preliminary study to validate the efficacy of a heat recovery boiler with water spray (HR-B/WS) that is currently under development. The HR-B/WS, where high temperature water condensed in the system is sprayed onto the inlet airstream, is designed to increase the recovery of waste heat and reduce NOx formation by lowering the flame temperature irrespective of the air ratio. Compared to the basic condensing boiler with the same return water temperature, HR-B/WS reduces the NOx and CO emission by approximately 50%. However, the rise in the efficiency was estimated at 2~3%, which was less than expected. This study identified its causes by analyzing the heat and mass balances based on the preliminary results and confirmed the design points of the heat recovery system aimed at improving the efficiency. © 2021 The Korean Society of Mechanical Engineers.