Instrumentation and Control Abira Khan

Sensors 3 main classes: Sensors which penetrate into the interior of the fermenter, e.g. pH electrodes, dissolved-oxygen electrodes. Sensors which operate on samples which are continuously withdrawn from the fermenter, e.g. exhaust-gas analysers. Sensors which do not come into contact with the fermentation broth or gases, e.g. tachometers, load cells In relation to its application for process control: In-line sensor On-line sensor Off-line sensor

Temperature Control Mercury-in-glass thermometers Electrical resistance thermometers Thermistors

Process Controls Flow measurement and control- Gases, Liquids Pressure measurement and control Safety valves Agitator shaft power Rate of stirring Foam sensing and control Weight- Load cell Microbial biomass Dissolved oxygen and carbon diooxide: P(O2)= C(O2)×PT Inlet and exit-gas analysis pH measurement and control Redox potential

Thermal Mass Flowmeter

Foam Sensing and Control Unit

On-line Analysis of Other Chemical Factors Ion-specific sensors Enzyme and microbial electrodes Near infra-red spectroscopy Mass spectrometers

Control Systems A control loop consists of 4 basic components: A measuring element A controller. A final control element The process to be controlled Manual control Automatic control: Two-position controllers (ON/OFF). Proportional controllers. Integral controllers. Derivative controllers

Simple Manual/Automatic Control Loop for Temperature Control

Control Systems Combinations of methods of control Proportional plus integral Proportional plus derivative Proportional plus integral plus derivative

Aeration and Agitation

O2 Transfer from Gas to Liquid Phase KLa, the volumetric mass-transfer coefficient, the units of which are reciprocal time (h -1) The volumetric mass-transfer coefficient is used as a measure of the aeration capacity of a fermenter The larger the KLa, the higher the aeration capacity of the system The KLa value will depend upon the design and operating conditions of the fermenter and will be affected by such variables as aeration rate, agitation rate and impeller design

Reference Principles of Fermentation Technology- Stanbury- 2nd edition, Chapter 8, 9