Lagrangian Approach for the Prediction of Slagging and Fouling in Pulverized Coal Combustion

The deposition of ash particles in pulverized coal combustion provokes several problems for the operation of utility boilers. In order to avoid such problems, power plant operators have great interest in predicting the slagging and fouling tendency of the used fuel.For this purpose, an industrially highly relevant tool for the prediction of slagging and fouling which is applicable on high performance computing platforms such as vector machines or massively parallel systems has been developed. The model has been implemented into the CFD code AIOLOS and couples several relevant processes that are crucial for the build-up of depositions in power plants. It accounts for the flight of the ash particles through the furnace, the corresponding interaction with the flue gas and considers several deposition mechanisms on walls and tube bundles. In case of a predicted contact between a particle and a surface, the deposition rate is calculated based on the stickiness of the particle and the surface which is correlated with the melting behaviour. The model also takes into account the change of the heat transfer resistance of the already deposited particles and consequently the influence on the flue gas temperature.The model has exemplary been applied to a utility boiler with a thermal input of 730 MW (360 MW_el) in order to demonstrate the capability of this engineering tool.