NOX Predictive Emissions Monitoring System at a TMP Mill, 2000 Engineering Conference Proceedings

Loren Euhus, P.E., Lori Blau--Ponderay Newsprint Company operates a newsprint mill in Usk, Washington. A Predictive Emissions Monitoring System (PEMS) for boiler NOx emissions was implemented at this mill in September of 1999. PEMS work by accurately predicting NOx emissions based upon more easily measurable variables, such as air flow into the boiler, temperature of the combustion air, fuel flow, residual oxygen concentration in the stack, etc. This application will save the mill in emissions monitoring costs.

First, conventional Continuous Emissions Monitoring System (CEMS) measurements were performed, providing historical data over a wide range of operation. Then an empirical predictive model was created from the historical data, and the model was put on line. To qualify to replace the CEMS, the NOx PEMS was subjected to rigorous certification testing as outlined by the U.S. Environmental Protection Agency (EPA). After review, the EPA certified the PEMS for operation, and the CEMS was removed from the mill. Re-verification of the predictive model will occur yearly with a relative accuracy test.

In addition, statistical data reconciliation techniques were employed to identify sensor failure, notify operations, and replace the bad input value with a predicted value in order to continue PEMS calculations. Sensor failures were simulated, and the EPA approved the PEMS for operation during single sensor failure.