How to control pH of a solution?



It is important to maintain the chemical properties of solutions at a setpoint in chemical industries. The process reaction will be depended on the chemical properties of solution used in the process.

The simple pH control can be explained by a simple process.

The pH of the solution is measured using a sensor. If the reading of sensor output is below the setpoint, then an alkaline solution is added to the solution to increase the pH level.

If the sensor output reading is greater than the setpoint, then an acid solution is needed to add in the solution to decrease pH level.

The acid and the alkaline solutions used to control the pH level are commonly known as Reagents.

A model for a practical pH control is shown above.

The pH of the solution is measured using a sensor and the pH value measure is applied to the analyzer which compares the actual pH value with a setpoint.

The control action is given to the field device, such as valves or pumps. There are two field devices shown above A & B, if one is to add acid then the other is to add alkaline. Thus both acidity and basicity can be controlled.

pH control techniques are commonly used in Food industries, chemical industries and in wastewater management.