This paper considers the special problems posed by the modelling and simulation of particulate processes and analyses the reasons which obstructed the application of general purpose process modelling tools to these processes in the past. It argues that the latest generation of these tools is now capable of directly representing and simulating particulate processes. It outlines the features of one such tool and demonstrates its capabilities by applying it to the study of the start-up of a continuous mixed suspension mixed product removal (CMSMPR) crystallization unit.