PREDICTION OF NOX EMISSIONS FOR FBC BOILERS BY EMPIRICAL MODELS – THE INFLUENCE OF SCALE-UP

摘要

Reliable prediction of NOX emissions can provide useful information for boiler design and fuel selection. The disadvantages and complexity of recently used kinetic NOX prediction models could be overcome by developing a simple empirical model. However, existing empirical models for prediction of NOX are used exclusively for pulverized coal boilers. This paper aims to modify some commonly used pulverized coal combustion empirical NOX prediction models – Pohl′s model and Ibler′s model – to fit the fluidized bed combustion boilers. The data from large scale fluidized bed combustion units are used for empirical models modification and compared with the data from pilot scale 0.5 MW fluidized bed combustion boiler. The reliability of proposed modifications to physical models and the influence of scale-up are discussed. The maximum reliability was achieved by modified Ibler′s model. If fuel mixtures were excluded the reliability increased. The NOX emissions of pilot scale boiler were higher compared to large scale units. However, these values were in agreement with Ibler′s model prediction, meaning the cause of higher values are fuel and combustion parameters and not the scale-up.