Integrated dry NO{sub x}/SO{sub 2} emissions control system. Final report, Volume 1: Public design

The U.S. Department of Energy (DOE)/Pittsburgh Energy Technology Center (PETC) and the Public Services Company of Colorado (PSCo) signed the cooperative agreement for the Integrated Dry NO{sub x}/SO{sub 2} Emissions Control System in March 1991. This project integrates various combinations of five existing and emerging technologies onto a 100 MWe, down-fired, load-following unit that burns pulverized coal. The project is expected to achieve up to 70% reductions in both oxides of nitrogen (NO{sub x}) and sulfur dioxide (SO{sub 2}) emissions. Various combinations of low-NO{sub x} burners (LNBs), overfire air (OFA) ports, selective non-catalytic reduction (SNCR), dry sorbent injection (DSI) using both calcium- and sodium-based reagents, and flue-gas humidification are expected to integrate synergistically and control both NO{sub x} and SO{sub 2} emissions better than if each technology were used alone. For instance, ammonia emissions from the SNCR system are expected to reduce NO{sub 2} emissions and allow the DSI system (sodium-based reagents) to achieve higher removals of SO{sub 2}. Unlike tangentially or wall-fired units, down-fired require substantial modification to their pressure parts to retrofit LNBs and OFA ports, substantially increasing the cost of retrofit. Conversely, the retrofitting of SNCR, DSI, or humidification systems does not require any major boiler modifications and are easily retrofitted to all boiler types. However, existing furnace geometry and flue-gas temperatures can limit their placement and effectiveness. In particular, SNCR requires injecting the SNCR chemicals into the furnace where the temperature is within a very narrow temperature range