M
Hi,
I'm developing a bioreactor (fermentor) for biomass production in our lab. We chiefly need to control three parameters - temperature, pH and
DO (Dissolved Oxygen).
Temperature control is pretty straightforward (at least I think so) - We plan to use a PID controller in the market which regulates a steam
jacket covering the bioreactor.
For controlling the pH we plan to incorporate a controller which is connected to a dosing-pump that switches between pumping an alkaline
liquid (KOH/NaOH) or an acidic one (diluted HCl) depending up on the setpoint of the pH.
But I'm having problems designing a DO control system. For pumping oxygen (air) into the bioreactor, we plan to use a diaphragm pump
connected to a sparger immersed in the biomass inside the bioreactor. Just above the sparger is a stirrer (RPM 200 - 1000) which will
'break' the oxygen bubbles (as they come out of the sparger) into smaller ones so that the oxygen has a better chance to get absorbed in the
biomass. Further, DO takes a long time to get registered in the biomass. So if we start pumping in oxygen now, it may be a while before it gets absorbed in quantities enough to be effectively detected by the sensor. To sum-up the DO problem:
1. We have to control the oxygen level in the biomass.
2. The oxygen takes a while to get dissolved.
3. We can control the oxygen dissolution by two factors -
a. By increasing/decreasing the oxygen flow through the sparger, i.e. pump more/less.
b. By increasing/decreasing the RPM of the stirrer.
Can anybody help me how to design a system for controlling the DO to regulate the oxygen pump and/or the stirrer speed?
Thanks in advance,
Mohit Mahajan,
Bioprocess engineering,
DEI, Agra,
India.
I'm developing a bioreactor (fermentor) for biomass production in our lab. We chiefly need to control three parameters - temperature, pH and
DO (Dissolved Oxygen).
Temperature control is pretty straightforward (at least I think so) - We plan to use a PID controller in the market which regulates a steam
jacket covering the bioreactor.
For controlling the pH we plan to incorporate a controller which is connected to a dosing-pump that switches between pumping an alkaline
liquid (KOH/NaOH) or an acidic one (diluted HCl) depending up on the setpoint of the pH.
But I'm having problems designing a DO control system. For pumping oxygen (air) into the bioreactor, we plan to use a diaphragm pump
connected to a sparger immersed in the biomass inside the bioreactor. Just above the sparger is a stirrer (RPM 200 - 1000) which will
'break' the oxygen bubbles (as they come out of the sparger) into smaller ones so that the oxygen has a better chance to get absorbed in the
biomass. Further, DO takes a long time to get registered in the biomass. So if we start pumping in oxygen now, it may be a while before it gets absorbed in quantities enough to be effectively detected by the sensor. To sum-up the DO problem:
1. We have to control the oxygen level in the biomass.
2. The oxygen takes a while to get dissolved.
3. We can control the oxygen dissolution by two factors -
a. By increasing/decreasing the oxygen flow through the sparger, i.e. pump more/less.
b. By increasing/decreasing the RPM of the stirrer.
Can anybody help me how to design a system for controlling the DO to regulate the oxygen pump and/or the stirrer speed?
Thanks in advance,
Mohit Mahajan,
Bioprocess engineering,
DEI, Agra,
India.