Demineralisation refers to the removal of dissolved solids from feed water and process streams. By definition, demineralisation is the near-total removal of inorganic salts from water. In most industrial process water treatment applications, this is accomplished through ion exchange.
Natural occurring water contains many dissolved solids in diluted forms which are usually various types of salts. These solids are known as total dissolved solids (TDS). Demineralization is the process of removing nearly all dissolved solids and mineral ions from water.
In industrial water treatment, demineralization refers to the removal of dissolved solids from feed water and process streams. By definition, demineralization is the near-total removal of inorganic salts from water. In most industrial process water treatment applications, this is accomplished through ion exchange.
Allmech electrode boilers operate on the principle that when electricity passes through any resistant material, such as water, it causes an increase in that resistant materialâs temperature. This principle ensures that no external heating mechanism is required and renders the boiler safe under all operating conditions. That is, where there is no water in the system, there is no resistant material and therefore no increase in temperature.
What is a Demin Plant?
A demin plant is a type of water purification plant. A Demin plant refers to any water treatment process or technology with near total removal of ionic mineral contaminants. Demin water plants are typically done with ion exchange or reverse osmosis, depending on the facilityâs needs, demineralization can provide near-total removal of ionic mineral contaminants.
Demin water is used widely for industrial and scientific purposes such as in laboratory applications and testing, computer chip manufacturing, lead-acid batteries, cooling systems, high pressure boiler feed, laser cutting, steam irons and steam raising, pharmaceutical manufacturing, cosmetics, aquariums and fire extinguishers.
How does a demin plant work?
A demin plant typically consists of two vessels; one containing cation and the other containing anion exchange resins. Raw water enters first through the cation resin, where mineral contaminants are replaced by hydrogen ions, and next through an anion resin, where mineral contaminants are replaced by hydroxyl ions, which combine with the hydrogen ions to form pure water. A demin plant then needs to be regenerated with hydrochloric acid and sodium hydroxide when necessary.
There is some flexibility in the configuration of a demineralization system in order to optimally meet various process conditions and purity goals. In designing a demineralization system, consideration should be given to changeability of the feed water, level of purity needed, system footprint, tolerance for ion leakage (in particular sodium and silica), and chemical feed requirements, among other factors.
Allmechâs Demin Plant
Allmechâs demin plants consist of two vessels; one containing cation and the other containing anion exchange resins. In short, raw water enters through the cation resin first, where mineral contaminants are replaced by hydrogen ions. Then it flows through an anion resin, where mineral contaminants are replaced by hydroxyl ions, which combine with the hydrogen ions to form pure water. The impurity ions are taken up by the resin, which must be periodically regenerated to restore it to the original ionic form. The denim plant then needs to be regenerated with hydrochloric acid and sodium hydroxide when necessary. The system runs as a stand-alone and does the control and regeneration automatically, with input control from the conductivity sensor.
What control valves are used in Demin Plants?
Allmech selected our Runxin F63C3 top mount automatic softener control valve as it is designed for either softening or demineralisation water treatment systems. The valve can be used with FRP vessels sizes up to 1465 and have a 1â inlet and outlet. The softener control valves have five main functions: service, backwash, brine and slow rinse, brine refill and fast rinse.
With the addition of the new PLC, Allmechâs demin plant is more easily customisable through the programming of the various inputs. It also offers alarm functionality to flag when water quality isnât up to scratch, which ensures the water is not needlessly dumped through backwashing and alerts the user to potential issues in the system. We use 3 Runxin ceramic electronic ball valves (3-wire) 12 volt units in our process. They are used as in service, rinse unit as well as emergency shut off.
Automatic and manual ceramic ball valves offer a cost-effective alternative to solenoid valves and provide better wear resistance. Our manual ceramic ball valves were used for manual isolation of water lines.
What industries use demin plants?
Demineralised water is water where the minerals or salts are removed. It is used in applications where water with low salt content or low conductivity is required. For every application a required conductivity is used.
Common applications for demin water require the use for ultra-pure water, which has even higher standards of pollution. Demin plants are used for various industrial and scientific purposes. These could range from laboratory applications and testing, to computer chip manufacturing, automotive uses such as lead-acid batteries & cooling systems, high pressure boiler feed, laser cutting, steam irons and steam raising, pharmaceutical manufacturing, cosmetics, chemicals, textiles, hospitals, fertilizers, aquariums and fire extinguishers.
What contaminants does demineralization remove?
Demineralization generally results in almost complete removal of minerals, and is typically reserved for applications requiring higher level of water purity, such as feed or makeup water for high pressure boilers, rinse water for food and beverage industries, or process streams used in electronics manufacturing. Below we have outlined the most common contaminants treated by demineralizers:
Cations
The cation resins within a demineralization system will exchange cations, or contaminants having a positive charge. Common cationic contaminants include:
- Â Calcium (Ca2+)
- Â Iron (Fe3+)
- Â Magnesium (Mg2+)
- Â Manganese (Mn2+)
- Â Potassium (K+)
- Â Sodium (Na+)
Anions
The anion resins within a demineralization system will exchange anions, or contaminants having a negative charge. Common anionic contaminants include:
- Alkalinity (CO32-, HCO3â)
- Chloride (Clâ)
- Nitrate (NO3â)
- Sulfates (SO42-)
How long does regeneration of a Demin plant take?
Allmechâs demin plant regeneration is carried out using a municipal or raw water supply, it is necessary to regenerate the cation first. You then use the âdecationisedâ water to regenerate the anion column. The full regeneration process is estimated at 2,5 hours.
Typical regeneration process
The Cation vessel is installed with a Runxin F63C3 automatic control valve as it is design for demineralisation water treatment systems. The unit will regenerate first in the following sequence.
- Backwash â 5 minutes
- Acid draw / slow rinse â 60 minutes
- Fast rinse â 10 minutes
- Return to service
Once the Cation unit has completed the regeneration cycle the Anion vessel with a Runxin F63C3 automatic control valve will start its regeneration using Cation water.
- Backwash â 5 minutes
- Acid draw / slow rinse â 60 minutes
- Fast rinse â 10 minutes
- Return to service
Once the Anion unit has completed the regeneration cycle the plant returns to service mode and is ready to provide treated water.
Runxin ceramic electronic ball valve (3-wire) 12 volt unit is used to return the demin plant to service from the regeneration cycle.
Is pre-treatment of water necessary?
Some pre-treatment of water may be required. This will depend upon the nature of the incoming water and the type of Demin plant.
Examples include:
- A Demin plant operated on low conductivity municipal water where significant levels of organics are present may need an organic scavenger or carbon filter for pre-treatment.
- A rinse water recovery Demin plant system may also need carbon pre-filtration if there are high rates of organics or the presence of free chlorine.
- Multi-media filtration might also be used in this instance, where suspended solids (possibly resulting from Metal Hydroxide precipitation) could be present.
Our advantages
Selection of your demin plant depends on the application, water quality and water consumption. Our technical team are at your service to ensure the optimum solution.
- Custom designed solutions for unique solutions
- Turn-key solutions including design, engineering, manufacturing, automation, installation, maintenance and training.
- State-of-art technologies for effective water and wastewater treatment, recycling, reuse, and disposal.
- On-site service and support.