FAQ'S About Demineralization Plant (DM Plant)?
What is Demineralization Plant? A Demineralization Plant consists of two pressure vessels containing cation and anion exchange resins. Various types of ion exchange resins can be used for both the cation and the anion process, depending on the type of impurities in the water and what the final water is used for. Typically, the cation resin operates in the hydrogen cycle. The cation in the water (i.e. calcium, magnesium, and sodium) passes through the cation exchange resin where they are chemically exchanged for hydrogen ions.
The water then passes through the anion exchange resin where the anions (i.e. chloride, sulfate, nitrate, and bicarbonate) are chemically exchanged for hydroxide ions. The final water from this process consists essentially of hydrogen ions and hydroxide ions, which is the chemical composition of pure water. The simplified demineralization plant consists of Composite resin vessel with change of strong cation and anion resin; control panel encompassing conductivity measurement and alarms, etc; acid and caustic injection facility from bulk, semi-bulk, or carboy containers.
What is DM water used for? The high-purity water from a DM plant is typically used for food beverage industries, high pressure boiled feed, wash water for computer chip manufacture, pharmaceutical process water, micro-electronics and any process where high-purity water is a requirement.
Why are there numerous types of resins used in demineralization plants? The type of resins employed and selected depends on numerous factors:
1. Treated water quality.
2. Input water quality.
3. Presence of organic foulness.
4. Water temperature.
5. Flow through plant required.
6. Regeneration method-either counter-current or co-current regeneration.
There is a vast range of resins to select from, e.g. pure fine resins, enhanced capacity resins, gel polystyrene resins, potable clear gel resins, resins for water containing organic matter, resins to achieve low silica levels.
What is co-current flow regeneration? The resin contained in the pressure vessel has about 50% free spaces above the resin (known as resin-free board). This free space allows backwashing, removal of any entrained solids, re-classification of the resin bed and it relieves bed compaction.
Water and acid/caustic regeneration is carried out in a down-flow direction.
What is counter-current flow regeneration? With counter-flow regeneration, the regeneration acid and caustic passes in the opposite direction to the service flow water. With counter-flow regeneration, the regeneration passes through the resin near to the outlet of the unit and, hence, counter-current flow regeneration has lower leakage to service than the co-current method.
How do you regenerate a DM plant? The "Aqua World" range of DM plant regenerates automatically according to the conductivity. The reentrant for the cation column is 28% hydrochloride acid and 30% caustic soda for the anion column.
What is mixed-bed demineralization? Polishing mixed beds come after the cation and anion standard vessels and, as the name implies, they are there to polish the water. The bed is an intimate mix of anion and cation resins. These resins are not regenerated at a pre-set time according to conductivity and are not operated to exhaustion but are regenerated on time and volume.
How to size a demineralization plant? For the sizing of a demineralization plant, a good in-depth water analysis is normally required which gives the breakdown of total anions and total cations and any potential organic foulness. The final required quality water specification is required, as well as flow rate and water used per day. In some circumstances, Life saver Water systems can "budget size" demineralization plant by knowledge of the total dissolved solids and water usage rates. This is not recommended, however for accurate costing and for a guaranteed outlet water quality.
Can water systems service demineralization plants? Yes, we offer single-day services or service contacts on all water treatment equipment. All of our water treatment service engineers are fully qualified and experienced on the full spectrum of water treatment equipment available. We have defined service specification sheets (available on request) which define the exact service schedule proposed for a demineralization plant.