To intensify the research in the field of dynamic modeling of solids processes, in the year 2013 the DFG Priority Program SPP 1679 “Dynamic simulation of interconnected solids processes” has been started. Its main objectives are the development of new dynamic models of different apparatuses in solids processing technology, providing numerical tools for flowsheet simulation and the investigation of the dynamics of solids processes. The SPP 1679 structurally consists of 27 individual projects, which are distributed among several German universities. They are thematically divided into four main groups (Fig. 1). An important part of this project is the development of a flowsheet simulation system Dyssol (an acronym for Dynamic Simulation of SOLids processes), intended for the dynamic modeling of industrial production processes with complex structures. A novel dynamic simulation system, as the central project (Z-Project) of the priority program, should be designed to integrate models, algorithms and methods developed within the whole SPP. The system must be able to handle processes with complex structures, considering solid, liquid and gas phases as well as their arbitrary mixtures.

A novel flowsheet simulation environment has to be developed within this project. It must be able to combine the results of other groups of the SPP 1679 into a single comprehensive framework. The main features that must be taken into account are:

• Dynamic simulation of flowsheets to reflect the time-dependent behaviour of processes and to consider accumulation of mass and energy;

• Proper calculation of multidimensional distributed parameters of the solid phase, integrating their possible interdependence.

One of the main challenges of the simulation of solids processes is related to the dispersity of granular materials (Fig. 3): the solid phase can be distributed along several interdependent parameters, such as size, shape, moisture content and density. For correct handling of solids in this case an approach with transformation matrices is used. This concept allows preserving information about all parameters, even those which are not considered or not changed in a particular apparatus.

Among the main features of the novel simulation system are the following:
-    dynamic simulation of complex process structures;
-    advanced calculation algorithm for dynamic simulations;
-    consideration of solid, liquid and vapor phases and their mixtures;
-    proper handling of multidimensional dependent distributed properties of solids;
-    providing standardized interfaces for implementation of new units and solvers of equations;
-    high modularity and extensibility of the simulation system.