Increased Relative Humidity (RH) Found to Induce Higher Rates of Particle Agglomeration during Powdered Sorbent Injection for Hg Emissions Control

The effect of particle agglomeration has been shown using the agglomeration sensor developed in the ATESR Lab; however, inconsistent results have been obtained when trials were performed in different seasons. As shown in Figure, delta I/I_0 is plotted as a function of the maximum number concentration for each trial. Results obtained in February are about 4% lower than those in June. We hypothesized that the relative humidity (RH) during sorbent storage affected the results; therefore, an aqueous impinger was implemented to increase the RH value to which the sorbent was exposed from 0% to 50%. As shown in Figure 3, the test results with higher RH shows overall larger delta I/I_0 values at identical particle number concentrations, suggesting that a higher RH value can increase the rate of particle agglomeration during sorbent feeding.

Figure 1: Three agglomeration results based on delta I/I_0 obtained at different times and conditions.