Crystallisation enables dissolved substances from solutions to be transformed into a solid and separated.
This trainer has been developed in cooperation with the Chair of the Thermal Process Technology at the Martin-Luther University, Halle-Wittenberg (Prof. Dr. Ulrich).
A pump delivers a saturated potassium sulphate solution in a circuit with a tank. To prevent premature crystallisation, the solution is heated above saturation temperature using a heating circuit. Both circuits are connected by two heat exchangers. A small amount of this undersaturated solution is fed through the crystallisation cell as a bypass. To crystallise this part of the solution, it is cooled by cooling water using two heat exchangers. Reducing the temperature converts the solution into an oversaturated, metastable state.
The crystallisation cell is a tube fitted with porous filter media at both the inlet and outlet. The removable cell can be opened to allow the addition of seed crystals. The porous filter media are selected in a way that the crystals can’t escape from the cell. The flow conditions cause a fluidised bed in the cell. The dissolved potassium sulphate crystallises out of the metastable solution at the seed crystals. The crystals grow. The growth rate can be determined by weighing the crystals before and after the experiment and by measurement of time.
A stirred tank with heat exchanger is available to prepare a saturated potassium sulphate solution. The temperatures in the two tanks and the temperature required in the bypass for crystallisation are recorded and controlled using sensors.
A drying chamber, a balance, a screening machine and a microscope are recommended for evaluating the experiments. Potassium sulphate is not included.
Specification
crystallisation from solutions in fluidised bed
stirred tank for preparation of a saturated solution
circuit for undersaturated solution with tank, 2 heat exchangers for heating and pump
bypass for oversaturated solution with crystallisation cell and 2 heat exchangers for cooling
removable and fillable crystallisation cell, PMMA
heating circuit with pump, tank, heater and thermostat
adjustment of flow rate in bypass using valves
measurement and control of temperatures in stirred tank, tank for undersaturated solution and in crystallisation cell
Technical data
Tanks
stirred tank: approx. 25L
for undersaturated solution: approx. 25L
heating circuit: approx. 32L
Pump (solution)
max. flow rate: approx. 21L/min
max. head: approx. 38m
Pump (heating circuit)
max. flow rate: approx. 6L/min
max. head: approx. 9m
Crystallisation cell
diameter: approx. 40mm
height: approx. 80mm
Heater power output: approx. 2kW
Measuring ranges
temperature: 3x 0…100°C, 1x 0…80°C
flow rate: 1x 0…12L/min
230V, 50Hz, 1 phase
230V, 60Hz, 1 phase
230V, 60Hz, 3 phases
UL/CSA optional
Dimensions and weight
LxWxH: 2000x800x1850mm
Weight: approx. 255kg