The simultaneous combined heat and power (CHP) production via biomass gasification is considered as one of the main alternatives to fossil energy. Yet, a major obstacle in the development of this advanced technology lies in the presence of tars in syngas that are responsible for clogging downstream process equipment. Mathematical modelling and simulation studies are powerful tools to predict the performance of new processes. Baratieri et al. (2009), Pérez-Fortes et al. (2011) or Damartzis et al. (2012) develop comprehensive models of integrated biomass gasification plant, but based on thermochemical equilibrium approach that do not take into account the formation of tars. Recently, extensive models of Dual Fluidised Bed (DFB) gasifier demonstrate the possibility of accurately predict the formation of tars in syngas (Abdelouahed et al., 2012). The work presented in this paper consists in integrating a rigorous model of a DFB gasifier capable of predicting tar and contaminants in a global biomass CHP process. Our model includes the steps of wood drying, wood gasification, syngas cleaning, and power production in gas engine. Heat integration is considered all over the process for intern consumption and extern district heating. The model is set in Aspen Plus® and external Fortran user-subroutines are used to precisely describe complex phenomena in gasification reactor and gas engine. The energey efficiency of the CHP plant is evaluated. Simulation results highlight the strong impact of the syngas cleaning step in the overall performance of the CHP plant.