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 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.
Learning Objectives And 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
Specification
- Rising film evaporator for increasing the concentration of temperature-sensitive solutions
- Stainless steel steam-heated single pipe evaporator
- Control valve for adjustment of steam pressure via PID controller
- Water jet pump and vacuum controller to reduce the evaporation temperature
- Separation of concentrated solution and evaporated solvent using glass cyclone
- Glass condenser for condensation of removed solvent vapour
- Stainless steel feed tank
- Glass tanks for concentrate and condensate
- Measurement of flow rate, pressure and temperature
- Steam supply from laboratory network
Technical Specification
- Rising film evaporator
- Heat transfer surface: approx. 0,08m2
- Length: approx. 1,2m
- Control valve: Kvs value: 0,4m3/h
- Water jet pump
- Final vacuum: approx. 100mbar
- Flow rate: approx. 90L/min
- Vacuum controller: -100…0kpa
- Condenser for solvent vapour
- Heat transfer surface: approx. 0,2m2
- Tanks
- Feed: approx. 30L
- Concentrate, condensate: approx. 10L each
- Measuring ranges
- Temperature: 7x 0…170°C
- Pressure: -1…1bar; 0…6bar (abs); 0…10bar
- Flow rate: 2…36L/h; 0…1000L/h
- 230V, 50Hz, 1 phase
- 230V, 60Hz, 1 phase
- 120V, 60Hz, 1 phase
