Fermenter design and operation Flashcards
Purpose of a Fermenter
Operate aseptically for days Agitate and aerate without damage to the organism
Low power consumption Temperature control
pH control
Reduce evaporation Minimise use of labour Maximise computer control Geometrically similar for scale-up
Flexibility
When selecting height there are three possibilities
Total vessel height Unaerated liquid height Aerated liquid height
Increasing Height leads to?
Increased the hydrostatic pressure
Allows more agitators
+ve and -ve of increased hydrostatic pressure
+ increases the solubility of oxygen
- increases solubility of other gases which may be toxic (e.g. CO2)
+ve and -ve of more agitators
+ Better power development - Can lead to compartmentalisation
Increasing diameter leads to
Lowers the superficial (linear) gas velocity
Reduces surface area available for heat transfer
+ve and -ve of lowers gas velocity
- poor mixing, oxygen transfer
+ve and -ve of reducing SA
- Leads to temperature and control problems
Measures and control of a STR
Temperature, Flow of gas and fluid, pressure and power/agitation
Measures for T
Sensor: Resistance thermometer Control: Use of water jackets or pipe coils
Measures for flow of gas and fluid
Gas: Measurement via rotameter or mass flow controller Fluid: Load cells or pump calibration
Measures for Pressure
Sensor: Diaphragm gauge Control: During normal operation of stainless steel vessels a positive head pressure is maintained to assist in the maintenance of aseptic conditions
Measures for power/agitation
Power: Watt meter attached to the motor in large scale systems Rpm: Tachometer
