A total heat recovery system between the flue gas and oxidizing air of a gas-fired boiler using a non-contact total heat exchanger

Abstract

Recovering heat from the flue gas of a gas-fired boiler can both improve boiler efficiency and decrease pollutant emissions. To improve the efficiency of the gas-fired boiler in a more cost effective and higher efficient way, a non-contact total heat recovery (NCHR) system is proposed for recovering heat from flue gas for use in heating and humidifying the oxidizing air of the boiler. A mathematical model of a boiler with an NCHR system was established, and the performance of the NCHR system was compared with that of other heat recovery systems. It is shown that the efficiency of a boiler with an NCHR system can reach 103.4% for an inlet oxidizing air temperature of 0°C, which is 13.4% higher than the efficiency of a traditional boiler. According to the case study, the energy saving potential of a boiler with an NCHR system is 12.97% compared to that of a traditional boiler. As for the economic analysis, the payback period of a boiler with an NCHR system to traditional boiler and the condensing boiler is 1year and 3years, respectively. In addition, the operation cost of an NCHR system is less than that of a boiler with an absorption heat pump for heat recovery (AHPB) system, indicating that the NCHR system has obvious economic benefits.