Integrated Dry Nojso, Emissions Control System Baseline Sncr Test Report Subj: Integrated Dry Nox/s02 Emissions Control System Doe I.d. De-fc22-91pc90550

The DOE sponsored Integrated Dry NOJSO, Emissions Control System program, which is a Clean Coal Technology Ill demonstration, is being conducted by Public Service Company of Colorado. The test site is Arapahoe Generating Station Unit 4, which is a 100 MWe, down-fired utility boiler burning a low sulfur western coal. The project goal is to demonstrate 70 percent reductions in NO, and SO, emissions through the integration of: 1) down-fired low-NO, burners with overfire air; 2) Selective Non-Catalytic Reduction (SNCR) for additional NOX removal; and 3) dry sorbent injection and duct humidification for SO, removal. The effectiveness of the integrated system on a high-sulfur coal will also be tested. This report documents the second test phase of the program. This second test phase was comprised of the start up of the SNCR system followed by a brief parametric test series. Time constraints due to the retrofit schedule precluded optimizing the SNCR system. Testing investigated both urea and aqueous ammonia as SNCR chemicals. Other parameters investigated included boiler load, the amount of chemical injected, as well as injection parameters (injection location, amount of mixing air, dilution water flow, and injector orifice sizes). NO, removals of nominally 35 percent could be obtained with both chemicals while maintaining ammonia slip levels less than 10 ppm at full load. At higher chemical injection rates (nominal N/NO molar ratios of 1.5 to 2.0). NO, reductions in the range of 60 to 70 percent were achieved, but with unacceptable levels of NH, slip. For a given level of NO, reduction, ammonia slip was lower with aqueous ammonia injection than with urea. The test program also confirmed prior observations that 1) the optimum temperature for NO, reduction with ammonia is lower than with urea, and 2) N,O emissions as a by-product of the SNCR process are lower for ammonia compared to urea.