Coagulation/Flocculation Treatments for Flue-Gas-Derived Water from Oxyfuel Power Production with CO2 Capture

Capturing CO2 from fossil fuel combustion provides an opportunity for tapping a significant water source that can be used as service water for a capture-ready power plant and its peripherals: more than 5% of the mass of water required for cooling-tower makeup in an oxy-fired plant employing integrated pollutant removal (IPR) for capture. Water condensed from oxycombustion flue gas by the National Energy Technology Laboratory's (NETL's) integrated pollutant removal (IPR) CO2-capture process has been analyzed for composition, and an approach for its treatment, for both in-process reuse and release, has been outlined. Experiments were performed to develop specifications for the first step (coagulation/flocculation) of this treatment approach. The results show that flocculation can remove most cations and reduce fine particulates by at least 90%. The speed of separation points to fast, in-line treatment of water for reuse within IPR, thus minimizing the water requirements for CO2 capture. In experiments, flocculation/coagulation removed few of the anions from solution. However, the remaining supernatant is amenable to reverse osmosis, crystallization, and ion-exchange processes for anion removal and cleanup of the remaining cations.