Control Characteristics of pH-Controller | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Objective: To determine the control characteristics of pH controller (M7822N) of Bio-Engineering AG fermenter. Theory: The adequate pH control action in the bioreactor is highly dependent on the several factors e.g., density, viscosity & volume of the fermentation broth, strength of acid and bases, on/off time of the pumps, pH zone (band) of control action etc. It is possible to design the controller settings of above critical parameters so that the control action is quickly established. Faulty settings of the above parameters will lead to oscillations of the measured pH value around the set point, or offset between controlled value and set point or even delayed control response. The Bio-Engineering AG, Switzerland fermenter has M7822N pH controller which allows to manipulate above parameters to arrive at optimal set point. This needs to be established before the start of any cultivation experiment so as to feature quick & stable control action with-out over any addition of acid/alkali. Description of the pH Controller: The different components of the controller are described below: 1. pH/mv potentiometer – This potentiometer enables adjustment of the slope of pH electrode by means of a calibration buffer. Procedure: Switch 1 to pH Observations: Record the observations in the following combination of P-band, TON and TOFF values. Keep the starting pH as 4 and set point pH as 7.
Prepare a plot of pH vs time for the above settings of P-band, TON & TOFF settings using high speed chart recorder. Discussion: Analyze & discuss the advantages and disadvantages of the different combination of P-band, TON & TOFFsettings. Identify the best combination of the setting from the above combinations or your own for the given fermenter system. |
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