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Evaporators are used in process engineering and food technology for increasing the concentration of solutions. Part of the solvent is removed by evaporation, which means that the solution retains a higher concentration of dissolved solids. Film evaporators are used in particular for temperature-sensitive solutions such as milk.
The CE 715 allows the operating behaviour of a rising film evaporator to be investigated. The untreated solution is fed from the feed tank below into the evaporator. The evaporator is a double pipe heat exchanger that is heated by steam. The steam pressure on the casing side is adjusted with a PID controller. A cyclone is installed after the evaporator to separate the evaporated solvent and the concentrated solution. The solvent vapour removed is condensed in a water-cooled condenser and collected in a tank. The concentrated solution can also be collected in a tank or fed back into the evaporator for the concentration to be increased further.
The two tanks, the cyclone and the condenser are made of glass for better observation. The system can also be operated under a vacuum to reduce the boiling point of the solvent. All relevant pressures, temperatures and flow rates are measured to allow evaluation and monitoring of the process.
To clean the system while installed, a pump and cleaning nozzles are fitted in the condensate and concentrate tanks.
Common salt and water are the recommended materials for experiments.
The well-structured instructional material sets out the fundamentals and provides a step-by-step guide through the experiments.
Learning Objectives / Experiments
- fundamental principle of film evaporation for increasing the concentration of temperature-sensitive solutions
- investigation of the variables influencing the solid concentration in the solution
- influence of pressure and feed flow rate on the separating process
- influence of flow rate and pressure of the heating steam on the separating process
- investigation of the variables influencing the energy efficiency of the process
- energy balances at heat exchangers
- system cleaning while installed