Integrated transient simulation of a BFB boiler with CFD models for the BFB furnace and dynamic system models for the steam cycle and boiler operation

An approach for integrated transient simulation of a BFB boiler furnace and the coupled steam cycle is presented. The BFB furnace is simulated with in-house CFD models implemented in the ANSYS Fluent® software. The boiler steam cycle with control loops is simulated with the dynamic process simulation software Apros®. The paper describes the steps taken to couple the modeling tools and discusses the way the numerical solutions can proceed in unison. The approach is demonstrated for a commercial BFB boiler. A fast load change situation was selected as the test case. A coupled transient simulation was carried out and the process behavior during the transient was analyzed. Critical properties affecting the feasibility of a given ramp rate are the emission release rates and temperature transients in the boiler. These properties are monitored during the transient simulation. The paper presents these results along with instantaneous data that show the spatial distribution of temperature and gas composition in the furnace. The paper shows that the modeling approach is feasible. Applicability of the approach and possible future improvements are discussed.