1 reply to this topic

[Zauberberg]

Does anyone have practical experience related to pH measurement and control in Alkylation Units neutralization sump, where acid drain liquid is being collected together with spent caustic and alkaline water from refrigerant and alkylate wash?
We are faced with the problem of frequent pH sensor fouling, leading to erroneous measurement and lack of proper neutralization process control, which both result in pH runaways and severe consequences in downstream wastewater treatment plant.

We have already tried different pH control systems, and all of them are lacking of sensor fouling resistance. Any suggestions on this issue?

[JMW]

If ever you can't make a direct measurement, try an indirect one.

What other properties vary in line with the pH? Look at each property in turn and when you identify the available technologies you will need to compare the measurement resolution with property variability to determine the sensitivity and you also look for features which address the problems you currently have.

For example, in evaporator control density can be measured to within 0.1% and viscosity to within 1.0% yet the viscosity is used for fish oil because the viscosity varies from 1 to 300cst while the density varies from 980 to 1000kg/m3. Despite the lower sensor accuracy, viscosity measurement is far more sensitive to product quality change.

In this case you might investigate ultrasonic measurement. I seem to recall an article on one of the manufacturer's websites about using for pH measurement.
AH, did a quick serahc and here is the link:
http://www.sensotech...d/LSM065_01.pdf