Thesis for the Degree of Master of Science


Year 1999
Jouni Savolainen

Dynamic model of a disc filter

The purpose of this thesis was to design and implement a dynamic simulation model of a disc filter in APMS simulation environment.

In the literature part of the thesis, firstly, the theory of filtration is described. In this part the basic equation of filtration, ie. the Darcy equation, is introduced both for compressible and incompressible filter cakes. Also, a more complex partial differential equation describing the internal structure of a compressible cake is discussed. In further theoretical discussions the basic equation describing fluid flow phenomena, ie. the Bernoulli equation is introduced.

In this thesis only disc filters used in papermaking processes are considered. The tasks and operational principles of a disc filter as a central part of paper machine fiber recovery and water circulation system are described. In addition to these the two major control strategies of disc filters are introduced and other disc filter models found in the literature are considered.

The second half of the literature part describes simulation programs. These are divided into two disctinct classes, static and dynamic simulators. The characteristics of both are discussed and examples of software and their producers are mentioned. The APMS dynamic simulator developed by VTT is described in more detail.

The experimental part of the thesis is divided into three parts describing the design, implementation and testing of the model. In the design part the database and program code structures are described. In the implementation part the tools used are discussed. In addition to this the three major parts of simulating with APMS, the generation, preparation and simulation are described in the context of the disc filter model.

The model was tested by simulating flow and consistency disturbances in the feed of the disc filter using two different control strategies. The model was found to give qualitatively correct responses in all simulated cases.

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