Applicability of self-driven humid and hot flue gas waste heat recovery system

Abstract:

The flue gas produced by gas combustion has the characteristics of high temperature and high moisture content. The lithium bromide absorption heat pump can recover the sensible and latent heat in the flue gas, but it still requires an external driving heat source. To solve the problems of poor heat recovery capacity and low economic efficiency of such systems, this paper proposes a self-driven humid and hot flue gas waste heat recovery system. The system combines a graded flue gas heat exchanger with traditional lithium bromide absorption heat pump. The thermal model and applicability model of the system were established, and the influence of main parameters on the thermal performance and applicability of the system was analyzed. Results show that under the conditions of flue gas inlet temperature of 550 ℃ and inlet moisture content of 120 g/kg(a), the maximum heat recovery efficiency of the system was 11.6 %, and the minimum value of the heat recovery net income balance period was 5.2 a. When the expected values of the heat recovery ratio and the net income balance period were 10% and 5.5 a respectively, the applicable range of the secondary water outlet temperature was 55 ℃~64 ℃. The maximum value of the energy-saving expansion coefficient of the self-driven system was 29.7%, when the flue gas inlet temperature was high and the inlet moisture content was low, indicating that the self-driven system at this time has the most significant energy-saving capacity in contrast with the direct heat exchange scheme.