A computer model for a general clarifier-thickener has been made and used for comparing different strategies for control of such dewatering units through simulations. The model builds on widely acknowledged theory for modelling clarifier-thickeners - discretizing the settling PDE into a set of ODEs so that concentrations of solids at discrete depths inside the unit become the states of the numerical model - and it was written in the Modelica language using the modelling and simulation environment Dymola. The work of estimating model parameters for themodel and comparing different control strategies was made looking at one particular clarifier-thickener at the company Boliden's mineral processing plant in Garpenberg. Among the control strategies that were compared in simulations were simple PID control and cascade control as well as more advanced control schemes. The simulations showed that the optimal control strategy to use is cascade control using rake torque as a secondary variable, which makes sense in particular for large thickeners such as the one mainly considered in this work.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:uu-319980 |
| Date | January 2017 |
| Creators | Teerikoski, Sakari |
| Publisher | Uppsala universitet, Avdelningen för systemteknik |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | UPTEC F, 1401-5757 ; 17015 |
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