TOTAL WATER
- Industrial Dealkalization:
Softeners
Dealkalizers
Rinse
Boiler Feed
Reverse Osmosis
Degasifier
Strong Base Demineralizer
Depth Filtration
Carbon Filtration
Demineralizers and Deionizers
Ultraviolet (UV) Systems
Industrial Dealkalization/Dealkalizers
Dealkalization (chloride-anion exchange) is concerned with the reduction of carbonate and bicarbonate anions. This can be accomplished by several methods, the simplest method being chloride-anion exchange. The advantages to this method include no acid handling problems, no need for degasification equipment, and no nooed for mechanical re-pressurization equipment that is required by other types of alkalinity removal systems.
The process used in chloride-anion dealkalization is ion exchange. This is the same process used in water softening, except that in softening one is concerned with the removal of certain cations. With dealkalization, carbonate, bicarbonate, sulfate and nitrate anions are removed and replaced with an equal amount of chloride anions.
In the exchange process for dealkalization, the anion resin has a great deal of exchange sites which when fully charged have chloride anions attached to them. Softened water is then brought into contact with the resin and the previously mentioned anions exchange places with the chlorides anions. Most of the bicarbonate and carbonate anions are removed, thus reducing the alkalinity of the water supple The water coming out of the dealkalizer contains sodium chloride in approximately the same amount as the total dissolved solids of the softened water coming into the dealkalizer.
In the service position the dealkalizer simply allows water to pass through the resin and on to use. The regeneration process requires a brine tank and is accomplished in the same way as in a softener. First, there is a backwash of the resin bed. Next, the brine is educted over the resin, and the chloride anions exchange places with the bicarbonate, carbonate sulfate and nitrate anions. This chloride-anion exchange continues until almost all exchange sites on the resin are occupied by cloride anions. After the brine step, there is a slow rinse followed by a fast rinse. At the end of the fast rinse, regeneration is complete and dealkalizer is ready for service again.
When removal of carbon dioxide is desired (such as in the condensate return line of steam boiler, the dealkalizer process is modified. A chemical feed pump is added to the unit to injet a small amount of sodium hydroxide (NaOH) into the dealkalizer during the brining position of the regeneration cycle. This converts CO2 gas into bicarbonate alkalinity (HCO3), which can then be exchanged by the anion resin. A dealkalizer will not remove silica from the water.
Chloride-anion dealkalization is usually recommended for processes that require a continuous supply of water at a low flow rate.
To meet the requirements of continuous operation, softened water and proper hydraulic balance, a dealkalizer system frequently consists of a four-tank system made up of a duplex softener and a duplex dealkalizer. An alternator control keeps one softener/dealkalizer train in service while the other softener/dealkalizer train is regenerating. This arrangement also allows multiple regenerations per day, to minimize equipment investment.