A process model has been developed which is able to predict with confidence the sulphur-dioxide removal performance of sorbent injected into the furnace for control of SO2. The model requires limited input information on the boiler plant conditions and the sorbent. It has been validated against laboratory and industrial-scale plant data, and gives a good prediction of sulphur-dioxide removal for both limestone and dolomitic sorbents. Therefore this model provides industrial plant designers and process operators with a valuable tool, enabling them to assess the performance of in-furnace sorbent injection for their plant, as well as selecting the most suitable sorbent and identifying the optimum location for the addition of sorbent.