IECM 12.0 beta User Manual > Modules Included with the IECM > Pulverized Coal (PC) Plant > SET PARAMETERS > NOx Control > 2. Hot-Side SCR >

Performance (continued)

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The Hot-Side SCR system has additional inputs for performance entered on this parameter screen. Many of the calculated quantities on the Performance screen are determined by the reference parameters on this screen. The following parameters are available:

•Reference Parameters: The first set of reference parameters is primarily used to determine the actual space velocity. The values are used with actual operating conditions through a series of correction factors in the IECM. If you set the actual space velocity displayed on the Performance screen, this set of input parameters is not used by the IECM and does not have to be set.

•Space Velocity: This is the reference space velocity for a high dust system. It is used to calculate the actual space velocity.

•Catalyst Replacement Interval: This is the reference operating life in hours associated with the reference space velocity for the high dust catalyst. It is used to calculate the actual space velocity.

•Ammonia Slip: Ammonia slip accounts for the ammonia passing through the reactor unchanged and further downstream. The value is based on an 80 percent or lower NOx removal efficiency. It is used in calculating the ammonia stoichiometry and actual space velocity.

•Temperature: This is the operating temperature associated with the reference space velocity. It is used to determine the actual space velocity.

•NOx Removal Efficiency: This is the NOx removal efficiency associated with the reference design specifications for the SCR system. It is used to determine the actual space velocity.

•NOx Concentration: This is the inlet NOx concentration associated with the reference design specifications for the SCR system. It is used to determine the actual space velocity.

•Reference Catalyst Activity: Catalyst activity decreases with operating time due to plugging and catalyst poisoning. The loss is a complex function of the catalyst formulation and geometry, the operating conditions associated with the flue gas, including temperature and composition, and the loading and composition of the fly ash. This complex function is represented by an exponential decay formula in the IECM. The following parameters are used to determine the reference catalyst activity, assuming the initial activity has a value of unity:

•Minimum Activity: The minimum activity is a lower limit for catalyst activity decay. The actual activity approaches this value over a long period of time.

•Reference Time: This is the time that corresponds to a particular activity known for the catalyst. It is used to determine a decay rate constant.

•Activity at Reference Time: A second activity reference point is needed to determine the activity decay rate. The activity should correspond to the reference time specified. It is used to determine a decay rate constant.

•Ammonia Deposition on Preheater: This is the percent of the ammonia slip that is deposited as ammonium salts in the air preheater. It is treated like a partition coefficient.

•Ammonia Deposition on Fly Ash: This is the percent of the ammonia slip that is absorbed onto the fly ash. It is treated like a partition coefficient. This is important for high dust systems.

•Ammonia in High Concentration Wash Water: The ammonia that deposits in the air preheater is periodically removed by washing. It is initially highly concentrated and requires denitrification pretreatment prior to regular treatment. This is the average concentration in that stream.

•Ammonia in Low Concentration Wash Water: The ammonia that deposits in the air preheater is periodically removed by washing. The concentration is initially high, but gradually decreases. This is the average concentration of the low concentration stream.

•Ammonia Removed from Wash Water: The ammonia that deposits in the air preheater is periodically removed by washing. This is the average amount of ammonia removed from the high and low concentrated streams.