Energy saving measurement method for flue gas waste heat recovery system with a water vapor heat carrier boiler

Flue gas waste heat recovery can effectively reduce the exhaust heat loss of boilers, decrease fuel consumption, and lower greenhouse gas emissions. As an energy-efficient heat recovery system for both sensible and latent heat, the heat recovery system with spraying water in flue gas and humidification in inlet air of boilers has been used in many projects recently. However, there are arguments on how to evaluate the energy-saving rate of the system because of the complex process and energy conversion relationship of the system. Based on the analysis of the energy balance and conversion relationships in the flue gas heat recovery system, a method for calculating the energy savings of the whole system compared with the system without flue gas heat recovery, including inlet air preheating in boilers, is proposed by using conventional equipment such as temperature sensors and heat meters. Taking the Hengli Thermal Power Plant in Linyi County, Shandong Province as an example, measurement and energy saving results after the implementation of flue gas waste heat recovery system are provided. The results reveal that for a boiler with an evaporation rate of 176.90 t/h, the total energy savings achieved by the entire flue gas heat recovery system amount to 10.86 MW, which accounts for 8.46% of the heat output of the boiler. Among these savings, 1.73 MW is obtained through boiler inlet air preheating and humidification, constituting 16% of the total heat recovery. This measurement method provides technical support for the real-time online monitoring of energy savings in the large-scale implementation of the system.