Enhanced capture of mercury in baghouse by using novel filtration media and filter design

Study was conducted at a 5-MW equivalent slipstream facility. During the trials lasting 10 days, the effect of a range of process variables was studied. The variables included flue gas temperature, air-to-cloth ratios, interval between cleaning, and the effect of removing some of the fly ash by an electrostatic precipitator (ESP) upstream of baghouse, etc. The study consisted of testing a novel membrane-based filtration media formed as pleated elements. Data will be presented that shows that by using novel pleated filtration elements, mercury capture as high as 98% can be achieved by inherent fly ash alone (without needing to inject powdered activated carbon). This was true in spite of majority (about 80%) of mercury being in elemental form in the flue gas. Traditional round filter bags are typically known to capture significantly lower percentage of mercury in the flue gas by inherent fly ash. Data was also collected with injection of activated carbon upstream of baghouse. It was found that by using these novel filtration elements, if a plant is already using powdered activated carbon the consumption of activated carbon can be reduced by as much as 85%. Data will be reviewed along with the proposal of mechanisms about how this novel filtration element works in achieving such high mercury captures, as compared to traditional round bags.