Computer modeling of Tennessee Valley Authority's coal based power plant at Kingston to predict the effluent to Emory river

by 1968- Bagchi, Bratendu

In the wake of stringent environmental regulations, this research studies ash pond discharge to the river by Kingston Power plant. Currently 1296 MGD of fresh water from the Emory river via plant intake is used in condenser cooling. 40 MGD of ash sluice water containing ammonium compounds, mercury compounds, phosphates, Arsenic, Selenium, etc, is discharged to the plant intake via the ash pond for recycle back as sluice water into the plant. Ammonia slip from SCR unit is responsible for the ammonia and mercury comes from the coal. The research addresses the methodology to predict pollutants in the ash pond discharge and optimize the overall water consumption from its current usage by using the pinch analysis method and recycle. A generic model focusing particularly on ammonia and mercury discharge is developed using ChemCAD simulator backed by actual data from the Kingston Power plant. The research reveals that mercury either elemental or oxidized tends to adsorb on the ash surface (KD ~ 10000 mL g iv -1). It is found in this work that in the presence of ammonia, mercury desorption follows a complex equation, due to the ammonia mercury interaction. About 70% of the ammonia slip is captured as ammonium compounds adsorbed on the fly ash surface and destroyed biologically in the pond. The ammonia destruction is modeled as Monod equation. On an average, the volatile suspended solid increases from 2 to 5.2 mg/l during the experimental residence time of 17 days suggesting a nitrification process responsible for ammonia breakdown. The model can be used to estimate ammonia, nitrates, phosphates, and mercury in the effluent to the river. The model can also form a basis for future research to (i) analyse Arsenic and Selenium; (ii) the effect of pH and Loss of Ignition on mercury desorption from the ash; (iii) assist in designing any treatment scheme deemed necessary at a future date by providing effluent data based on coal feed and process conditions. v