OCR Text |
Show 6 A16SE738.T basis, with the current limits being 2970 lb/hr with compliance based on annual stack testing. Testing has shown NOx emissions ofO.9-1.3Ibs/MMBtu at full load conditions. In conjunction with the initial SNCR conceptual test, NOx measurements at the stack and at the economizer outlet also indicated an average baseline of 1.1 Ibs/MMBtu. Baseline data were recorded daily using information gathered by the plant Continuous Emissions Monitoring System (CEM:S). The CEMS was installed in November 1993; therefore, there is a limited amount of historical baseline data available. Prior to the demonstration, CEMS baseline data were gathered over the period from December 1 to December 12, 1993. At the beginning of the demonstration, baseline data were recorded three times daily for five minutes during each period. On January 27, the length of the baseline period was increased to 30 minutes to accommodate the time response of the system following shut-off of the SNCR system, thereby allowing more representative data to be recorded. A three dimensional surface generated from a plot of baseline data from December 1-12, 1993 is presented in Figure 3. The general trend of NOx increasing with load and O2 can be seen in the figure, as well as the increased dependence of NOx upon O2 at the higher loads. Not shown are the actual data points that went in to the best fit plot. The variability in the data was quite high, similar to the high variability found in the short term test. Scatter relative to the surface/curve was +/- 250 ppm NOx, representing a 40% uncertainty in NOx• Further attempts at correlation to more quantitatively defme relationships between operating conditions and NOx were similarly not successful. This inability to correlate average NOx to load and economizer O2 is hypothesized to be a result of the cyclone and unit specific conditions. Area Regulation (AIR) and Load Following With the introduction of independent power producers, units that were previously marginal baseload units have changed from being baseloaded to load following. Since most coal units cannot take frequent starts and stops, this limits the degree of cycling or load following that can occur. However, they can accommodate load changes more frequently than the full to minimum load swings that previously only occurred at night or on weekends. On an economic dispatch basis relative to other coal-frred baseload units, this unit is generally one of the last to be dispatched off its minimum load segment and is usually the frrst to be backed down as load demand decreases. Normally such adjustments would only occur at night or on weekends and incremental changes during the day would be made with the more flexible oil-and gas-frred units. However, there is currently an oversupply of baseload capacity from recently completed nuclear and cogeneration units in the PJM Interconnection Power Pool. As a result, the marginal coal units such as B.L. England Unit 1 are being called on to provide the necessary incremental adjustments during the day. A second role often assumed by units that load follow is area regulation. In contrast to load following which might be adjusted hourly, area regulation involves smaller, more frequent adjustments to load. Fine-tuning of load for area regulation occurs on a minute-by-minute basis and involves MW adjustments of around 10 MW. These small and frequent adjustments |