OCR Text |
Show testing is handicapped because a limited number of operating scenarios can be exercised and the results obtained must be assigned appropriate, though often unknown, weighting factors in order to obtain a true, representative average. Analysis results of the carbon content of the flyash collected during the baseline and AOFA perfonnance tests are presented in Figure 7. In addition to its impact on thennal efficiency, unacceptable levels of unburned carbon might cause reduced precipitator perfonnance and the inability to market flyash. This condition could require that the AOFA flow be reduced thereby lowering the potential NOx reduction. Full-load results from samples taken from the economizer outlet indicate combustibles loss-on-ignition (LOI) values twice the pre-retrofit condition. The near-isokinetic samples are obtained continuously from two, single point, sampling probes (the CEGRIT probes) located at the economizer outlet. Results from multi-point, isokinetic, mass-train sampling at the electrostatic precipitator (ESP) inlet confrrm this doubling. WB Retrofit. The new LNBs were installed during a seven week outage starting March 8, 1991, and continuing to April 28, 1991. Prior to the outage, rigging was installed, access pathways were formed, and when possible, insulation and lagging were removed. Although no pressure part modifications were required, installation of the new FWEC burners was far from simple. Complicating factors included craft labor shortages, the presence of asbestos and unacceptable levels of arsenic in the boiler, and the requirement to coordinate with the many other work activities occurring at the plant during a major outage. Thirty craft personnel were involved in the retrofi~ working a single, ten-hour shift. six days a week for four weeks and two, ten-hour shifts, six days a week for the remaining three weeks. Optimization of the burners for NOx reduction was perfonned by FWEC personnel during a three week period in June. The optimization required that the unit be taken out of economic dispatch and run at full-load for much of the optimization period. NOx (lb/MBtu) Figure 6: 1 . 4~----------~------------r-----------.-----------~------------. SHORT-TERM BASELINE 1 . 2+------------+------------~--~--~--4-----~--~~----~~--~ 25% LONG-TERM BASELINE 40% 0.8 t------t-=;--====*===========t=~-=--I----______j LONG-TERM AOFA SHORT·TERM AOFA O . 6+------------+------------~----------4------------+------------4 O . 4+------------+------------~----------4------------+----------~ 250 300 350 400 450 500 Load (MW) Plant Hammond Phase I and Phase II NOx Emissions 10 |