Study of flue gas emission and improvement measure in a natural draft dry-cooling tower with flue gas injection under unfavorable working conditions

Abstract

In this paper, we observed that flue gas from a natural draft dry-cooling tower (NDDCT) with flue gas injection could not be discharged smoothly under unfavorable working conditions (e.g., when the louvers are closed in winter), which may have caused severe corrosion on the inner shell of the cooling tower. In light of this issue, we proposed an improvement measure. On the basis of the computational fluid dynamics (CFD) method, we established a numerical model for NDDCT with flue gas injection to predict the flow field and pollutant diffusion. We simulated flue gas emissions for a NDDCT with flue gas injection under normal and unfavorable working conditions. The results showed that the air mass flow rate and heat rejection of the cooling tower decreased significantly, and the air flow in the cooling tower became disorganized when the louvers were closed under unfavorable working condition. Compared with normal working conditions, the pollutant concentration on the inner shell of the cooling tower increased by 1.5 times under unfavorable working conditions. After increasing the height of flue gas outlet, the pollutant concentration on the inner shell of the cooling tower decreased obviously.