High temperature pressurised black liquor gasification has the potential to significantly improve the efficiency of energy and chemical recovery in the pulping industry. However, a lack of demonstration of the reliability of the process has delayed its large scale industrial implementation. As an important step towards a greater trust in the process reliability, a self-consistent CFD model has been developed. This paper contains a detailed description of the model and a performance prediction of an entrained flow pilot gasifier for a typical operational condition. Emphasis is put on the modelling of input data for the CFD simulation where eight key assumptions form the basis for a consistent model of the black liquor composition. The results for the pilot gasifier performance with typical values for the design variables indicate that the droplet size should be <200 ?m and/or have a residence time of 2-3 s for a high level of carbon conversion.