Dry injection of sodium sorbents (trona and sodium bicarbonate) has been proven as an important multi-pollutant control technology due to (a) its low capital cost, (b) small installation, © easiness to operate, and (d) flexibility to fuel changes. Trona has been used as the main sodium sorbent due to its relatively low price. However, for some power plants where higher SO2 removal rates are desired and amount of generated fly ash need to be minimized, sodium bicarbonate (NaHCO3) offers a good alternative. For these reasons, a power plant that has been using trona since Fall 2005 tested conversion from trona to sodium bicarbonate on a 100 MW boiler. Trona or sodium bicarbonate was injected upstream of a hot-side ESP. The flue gas temperature at the injection point was around 600 oF. For 80% of SO2 removal, the normalized stoichemetric ratio (NSR) with trona was 2.5. With milled sodium bicarbonate, the required NSR for the same SO2 removal rate was decreased to 1.0. Over 97% of HCl was also removed. As a result, less sorbent was needed and significant savings in the sorbent was achieved. Furthermore, less fly ash was produced due to the sorbent change, and resulted in lower fly ash disposal cost. Same as trona, the sodium bicarbonate was able to keep the stack opacity below the limit since both sodium sorbents were able to lower the fly ash resistivity and thus enhance the ESP performance. Click Here For Complete Speaker Text
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