Heat and power stations are often in need of optimizations. A simulation model is a tool for findingways to optimize the plant. The scope of this diploma work is to develop a simulation model ofBoiler 5 at Mälarenergi AB. Boiler 5 is a circulated fluidized bed boiler that was taken into service inyear 2001. Among the included parts in the boiler are cyclone, convection part andINTREX-chambers. The software that was used for the simulation was SimTech’s IPSEpro. IPSEprois a heat and mass balance software for steady state calculations. The program comes with a set ofmodules in a library called APP_lib which contains modules such as preaheaters, pump, boiler andturbine stages. The user can however design own modules in the Model Development Kit, since thelibrary code is open source. The development of the simulation model started with an updating of anold model from year 2003. Values provided from Foster Wheeler where then used to make the modelcalculate in a right way. Thereafter some calculations of the super heaters’ heat transfer coefficientswere made. The coefficients were then translated into IPSEpro’s own programming language ModelDescription Language, and were put into the model’s modules. The results were compared with realvalues from the plant’s system. It showed that the calculated values needed more investigations to bemore accurate. The conclusion was that the final model needs more equations to describe the plant in amore realistic way.