Application of PLC in Process Control of Industrial Pure Water System

Application of PLC in Process Control of Industrial Pure Water System


Water is colorless and odorless. It seems simple but it is not simple. There are many components in water, and water quality, hardness, pH, conductivity, etc. are also quite particular and have different grades.

The water system is the type that the technology industry, the panel industry and the industry are more commonly contacted with. Whether it is wastewater treatment or pure water production, it is not a single device that can purify the water. In the middle, it is necessary to go through the dosing procedures of many systems, complex cooperation and precise data control.……etc. These complex pure water production control procedures are often assisted by PLC programmable controllers to carry out automatic control procedures.

Today, Longzhong is going to introduce the process of industrial pure water system!


First of all, let's introduce some terms that will be mentioned in the manufacture of industrial pure water systems:

Hydrogen ion concentration ( pH value )

The pH value refers to the hydrogen ion concentration index, also known as the "acid-base value", which is a scale of the hydrogen ion activity in the solution, that is, a measure of the acidity and alkalinity of the solution. Water is neutral when its pH is 7, acidic when it is below pH 7, and basic when it is above pH 7.



Indicates the ability of water to conduct current, and the conductivity is related to the total concentration, mobility, valence, relative concentration and water temperature of ions in water. Generally, the higher the conductivity, the more electrolyte in the water.


reverse osmosis

Reverse osmosis English abbreviation: RO, is a method of using osmosis (osmotic pressure) to purify water. Place clear water (hypotonic solution) and salt water (hypertonic solution) in a tube, separated by a semi-permeable membrane that allows water to pass through, and it can be seen that water flows from places with low osmotic pressure to places with high osmotic pressure.

Then we will mention the water purification procedure, the procedure is probably:
2B3T ion exchange resin system → RO system reverse osmosis → The treated pure water is sent to the water outlet for use.

Flow chart of pure water system

The raw water first needs to be filtered by a multi-layer filtration system, and all larger particles of impurities are removed through the filter bed in the system, and then the 2B3T adsorption function is used to remove chlorine, chloramines, herbicides, pesticides, industrial solvents, and some heavy metals in the water. After the 2B3T treatment, the water will enter the primary pure water storage tank. At this time, it needs to be filtered again to deal with the particulate impurities, and then it will enter the RO reverse osmosis treatment system.

Finally, from the produced reverse osmosis pure water, the unneeded specific ions are further removed through the automatic mixed bed system (this part is similar to the ion exchange resin of 2B3T), and the produced water will enter after the last filtration. Pure water storage bucket, pure water is done.


●2B3T ion exchange resin tower
2B refers to 2 BED (bed) cation exchange resin bed and anion exchange resin bed; 3T is 3 TOWER (tower) degassing tower. 2B3T is a set of desalination system consisting of positive bed, negative bed and degassing tower, also commonly known as 2 beds and 1 tower.

2B3T process: mainly use the cation resin tower to absorb the cations in the influent water, remove the CO2 and carbon dioxide through the degassing tower, and then use the anion resin tower to absorb the anions in the water. In this way, the conductivity of the permeate water can be made below 1μs/cm, and the recovery rate of the latter stage RO  can be improved. When the ion exchange resin process is saturated with adsorption, it is necessary to use regeneration agents such as HCl hydrochloric acid, NaOH sodium hydroxide …


●RO system reverse osmosis
The reverse osmosis membrane is the basic component of the water purification system, and the water produced is usually used in the semiconductor industry, electroplating industry, pharmaceutical industry and medical water, and also used in nuclear power generation. Reverse osmosis is driven by a semi-permeable membrane and a pump (pressurized motor), and the water pressure pushes water molecules to pass through the semi-permeable membrane, separates water from impurities, and processes and purifies it into high-quality water.
It is worth mentioning that the salt removal rate of RO membrane is as high as 93%, which can be used to concentrate and recover salt-containing water, and also used to concentrate sugar-containing solutions in the food industry.


Pure water outlet method
●POU (Point of use):Point of use type, installed on the point of use. For example: install a POU under the kitchen faucet or the countertop and add an extra tap for drinking water.
●POE (Point of entry):Centralized treatment, a system installed at the point where the water pipes enter the house. Just like the Taiwan water company will centrally filter and purify the water, and then send the water that can be used for people's livelihood to each household through the water pipeline.


These complex water treatment programs are not just installed by PLC and automatically controlled by the process. How to effectively monitor the water quality, regenerate the dosing value, save the man-hours spent by personnel in the operation of the industrial water system, and check the stability of the pure water quality control…… The only way to do it is to write the settings through the PLC program.

For the process control of the PLC industrial pure water system, Longzhong Enterprise has accumulated considerable experience so far, which can be seen:Achievement case - plant water system

Have any plant water system needs
Longzhong provides Technical Advisory Services | Tel: 06-243-7822

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