Modelling CaS03/CaSO4 precipitating flow in water treatment deviices

27.12.2002 - 31.12.2007
Research funding project
The intent of this project is the exploration of thermo- and hydrodynamics of water flows in reverse osmosis membranes and heat exchangers within water treatment plants. Fouling, the attachment or adsorption of substances onto the process equipment, limits heat and mass transfer, thus, the operation of the unit. A major fouling phenomenon in aqueous systems is scale formation due to precipitation of salts in water. Calcium carbonate and calcium sulphate are predominant sparingly soluble salts that are present in the seawater as well as brackish and industrial water systems. The first emphasis is the set-up of a model yielding consistent sets of thermodynamic properties (heat capacity, density, vapour pressure, osmotic pressure) for the aqueous systems. This model has two answer two purposes: applicability to numerical flow simulation and validity for a wide range of operating conditions - 0 to 100 bar in reverse osmosis membranes and 0 to 150 °C in heat exchangers at salinities up to 15 weight percent. Thus, a main effort is the modelling of the effects of varying temperature and pressure on the electrolyte equilibrium. The topic of co-precipitation is addressed by differing equilibrium formulations, the range of validity and the applicability of the laws of thermodynamics is investigated. The second emphasis is the implementation of the thermodynamic model into a numerical flow simulation program. An existing stand-alone flow simulation code provides extensive opportunities to implement the property data and the specific boundary conditions for heat and mass transfer in the devices. The output of the overall simulations are predictions of scaling effects depending on the operating conditions. This knowledge can be used to optimise these conditions as well as the usage of anti-scalants and other pre-processing steps. The information of salt concentrations and the osmotic pressure at the surface of the membrane leads to better assessment of the mass transfer.

People

Project leader

Project personnel

Institute

Grant funds

  • European Commission (EU) 6.FP: MOBILITY - Human resources and mobility Marie-Curie Grants 6.Rahmenprogramm für Forschung European Commission - Framework Programme European Commission Application number 008916

Research focus

  • Climate Neutral, Renewable and Conventional Energy Supply Systems: 30%
  • Modeling and Simulation: 70%

Keywords

GermanEnglish
Stoff & Wärmeübertragung Heat & mass transfer
Reverse-OsmoseReverse osmosis
WärmetauscherHeat Exchanger
Wässrige ElektrolyteAqueous electrolytes
ScalingScaling

External partner

  • The University of New South Wales School of Chemical Engineering and Industrial Chemistry

Publications