Pneumatic conveying systems provide a highly flexible means of transporting dry bulk particulate material. The main problem encountered when designing, optimising, or uprating these systems is the determination of the air supply necessary to achieve a particular duty (solids mass flow rate). Many correlations exist to predict the pressure drop necessary to drive the flow, and the gas velocities necessary for successful operation. Unfortunately, the design methods that incorporate these correlations are limited in terms of their flexibility. The development of this simulation resulted from the desire to increase the flexibility of the design method, and the need to employ more than one pressure drop correlation. As a result of these two requirements the problem of simulating the operation of a pneumatic conveying system was re-evaluated.