Abstract: A method and system are provided for calculating a marginal cost curve for a plant at a plant load range comprising a plurality of specified plant loads. The method includes providing a model used for controlling the plant. The model relates plant load and one or more given cost contributing factors. The marginal value for each of the one or more given cost contributing factors at each of the plurality of specified plant loads is determined using the model. A variable cost at each of the plurality of specified plant loads is determined by: (i) multiplying the marginal value of each of the one or more given cost contributing factors at each of the plurality of specified plant loads by a respective unit cost of each of the one or more given cost contributing factors, and (ii) if there are a plurality of given cost contributing factors, summing the results of (i) at each of the plurality of specified plant loads.

Abstract: A method and system are provided for controlling SNCR performance in a fossil fuel boiler. A performance goal for the boiler and data on current boiler performance is obtained. A determination is made as to whether the performance goal is satisfied by the current boiler performance. When the performance goal is not satisfied, the generally closest operating region in which the performance goal would be satisfied is identified. The operating region is associated with desired operating parameters of one or more devices affecting SNCR performance. One or more control moves are determined using the desired operating parameters of the one or more devices for directing the boiler to the operating region. The one or more control moves are communicated to the one or more devices.