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One Page Tip: August 2020

NOx Correlation Testing - Pre-Testing Activites

Review the features of the NOx Correlation module found in the StackVision User Guide, in the “Help” area of the StackVision software. Here are some helpful tips for pre-testing for NOx Correlation:

1. As with all procedures, preparation is extremely important. Get out and review your in-house procedure, especially since this testing is performed infrequently (every 5 years) and it’s expensive to conduct (the stack testers will cost $10K - $20K, plus the actual operating expenses).

2. Review your testing plans with the people responsible for dispatching and operating the unit involved. These
conversations should begin weeks, if not months, in advance.

3. Go ahead and review any past correlation testing records and even begin setting up and defining those new records. The StackVision Users Guide is a great resource.

4. Review your in-house records, due to the infrequency of these tests, preparing and following a site-specific procedure helps lead to consistent and successful results.

5. Determine or verify the validity of the four operating parameters that you will be tracking and recording in the
data system. These four parameters must be chosen carefully and lead directly to the formation of NOx emissions.

Therefore, if one or more parameters deviates from their normal range of operation, as recorded during the NOx testing, then the NOx curve is no longer representative of the actual NOx emissions and the root cause for this deviation should be investigated and corrected.

6. If water or steam injection is used, then most states require the water or steam injection rate, or injection ratio, be one of the four operating parameters. The other operating parameters are typically compressor outlet pressure, temperature, inlet guide van position, or others. The parameters chosen should be made while consulting with the turbine or boiler manufacturer.

7. Decide which operating levels (usually four sets of operating levels from minimum to maximum load) the testing is to be performed at. Be aware that the maximum operating level which can be achieved can change, due to ambient weather conditions. Hotter weather conditions (hot ambient air can mean less dense air or less mass of O² per cubic foot) in summer can limit or reduce the maximum load the unit can reach.

8. Prepare for testing by selecting the date with the various parties involved (your boss, the operating staff, etc.). In many cases, the dates for the testing need to be scheduled at least several weeks to several months in advance, especially with the stack testing team.

9. Review the records from the most recent round of testing, focusing on the fuel flow, heat input, and the four operating parameters. Duplicating those operating conditions should replicate the emission conditions and hopefully achieve a successful set of testing results. Make sure all preventative maintenance activities have been completed successfully on the fuel flow metering system, along with any work for the burners, which might impact the formation of NOx emissions.

For questions, suggestion, or for a general chat, do not hesitate to contact me.

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Jon Konings

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