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Show 12 The HOT FOIL® LOI Analyzer is a direct complement to the multi-point O2 analyzer in conducting combustion diagnostics and/or boiler tuning for NOx optimization. Although composite ash samples drawn from several points in the duct are commonly used to establish the optimum operating O2 level for acceptable ash LOllevel and minimum NOx' it is often advantageous to collect individual (point-by-point) ash samples in a duct during combustion diagnostics to identify regions of high LOI and low O2• Once uniform combustion has been established by burner air register, mill or fan bias adjustments using the multi-point O2 analyzer, the uniformity can be quickly confirmed by processing the ash samples using the HOT FOIL ® LOI analyzer. If the ash LOI data indicates that additional tuning is necessary to achieve boiler performance goals, these changes can be implemented within the hour rather than waiting several days for the lab LOI test results. This instrumentation is particularly valuable in tuning OFA systems. It should be noted that combustion uniformity can be achieved using the diagnostic techniques outlined above even in cases where the coal flow distribution between burner pipes leaving a mill is not balanced. Unfortunately, some utilities have postponed boiler tuning efforts until a major outage so they can replace coal pipe orifices or repair riffle boxes because the coal flow is not even. However, it is often not necessary to postpone tuning until uniform coal flow has been achieved because the local burner secondary air flow can often be adjusted to compensate (depending upon the degree of coal flow imbalance). In other words, prior individual burner pipe coal flow measurements can be used to guide the secondary air flow adjustment at the burner front until a uniform airlfuel ratio is achieved at all burners. This approach points out the necessity of dOing thorough pulverizer testing and primary air/coal flow distribution testing before engaging in a detailed combustion tuninglboiler performance and emissions characterization test program. Future Instrumentation Requirements The need to continually maintain compliance with the Clean Air Act Amendment NOx regulations is expected to lead to more frequent combustion diagnostic and tuning activities as well as more advanced instrumentation requirements. Continuous emission monitoring systems (CEMS) and NOx optimization software may become more useful in identifying a degradation in NOx emissions or a departure from a specified operating parameter range. However, more detailed diagnostic instrumentation will become necessary to identity combustion related problems in the burner zone, particularly as equipment wears and furnace ash deposits build. Unfortunately, burner zone visibility to spot these problems is often very poor and a combination of local 02' CO, NOx' gas temperature and ash carbon measurements are necessary to identify and isolate combustion system related problems. As low NOx firing system performance degrades to the point where compliance at full load without a derate becomes a concern, it is anticipated that the need for combustion diagnostics on a more real time basis may develop. Although gaseous emissions measurement at the economizer exit on a real time basis is commonplace, the real time measurement of these parameters at the |