Application of flowsheet simulation systems is not common in solids processing. Commercially available flowsheet simulation systems have usually a strong focus on fluid processes and just a few solids handling features. Special requirements for solids processing are identified and taken into consideration during development and implementation of an appropriate flowsheet simulation system. The features of the prototype simulator SolidSim are presented. Applications to soil-washing - a process for remediation of contaminated soils - demonstrate the usefulness of the simulator in plant design, plant adaptations and related tasks for complex solids processes.