Dealkalizer Plant
A dealkalizer, also known as an anion exchange system, is a water treatment technology used to reduce the alkalinity of water by removing alkaline minerals, primarily bicarbonate and carbonate ions. Alkalinity refers to the capacity of water to neutralize acids, and high alkalinity levels can lead to issues such as scaling, corrosion, and interference with certain industrial processes.
System Components
Pre-Treatment: Prior to entering the DM plant, water often undergoes pre-treatment processes to remove suspend particles, organic matter, and chlorine. Pre-treatment may involve processes such as sedimentation, filtration, activated carbon adsorption, and disinfection.
Cation Exchange Unit: The cation exchange unit is the first stage of the DM plant and contains a bed of cation exchange resin. The resin beads in this unit exchange positively charge ions (cations) present in the water, such as calcium, magnesium, sodium, and potassium ions, with hydrogen ions (H+). This process reduces the concentration of cations in the water.
Anion Exchange Unit: The anion exchange unit follows the cation exchange unit and contains a bed of anion exchange resin. The resin beads in this unit exchange negatively charge ions (anions), including chloride, sulfate, bicarbonate, and nitrate ions, with hydroxyl ions (OH-). This process reduces the concentration of anions in the water.
Mixed Bed Unit: After the cation and anion exchange units, some DM plants include a mixed bed unit. The mix bed unit consists of a mixture of cation and anion exchange resins in a single vessel. It helps achieve further purification and removes any remaining traces of cations and anions, producing highly demineralize water.
Regeneration: Over time, the cation and anion exchange resins become exhauste and require regeneration to restore their capacity. Regeneration involves passing regenerant chemicals, such as hydrochloric acid (HCl) for cation resin and sodium hydroxide (NaOH) for anion resin, through the resin beds to remove the adsorb ions. This process restores the resin’s ability to remove minerals and salts from the water.
Polishing Treatment: In some cases, additional polishing treatment steps may be include in the DM plant to further enhance water quality. This can involve processes like activat carbon filtration, ultrafiltration, or reverse osmosis to remove any residual impurities and achieve the desire water purity level.
System Steps
Ion Exchange : Water enters the resin tank, and the alkaline ions, primarily bicarbonate (HCO3-) and carbonate (CO3^2-) ions, come into contact with the strong base anion exchange resin beads. The resin beads attract and remove these alkaline ions from the water, exchanging them with other anions present in the resin.
Alkalinity Reduction: As the water passes through the resin, the alkaline ions are replace by other anions, typically chloride (Cl-) or sulfate (SO4^2-) ions. This results in a reduction in the alkalinity of the water.
Treated Water Flow: The dealkaliz water, with reduce alkalinity levels, flows out of the resin tank and is distribute for various uses, such as industrial processes, steam generation, or other applications where low alkalinity water is require.
Capacity and Regeneration: Over time, the resin bed becomes saturate with alkaline ions, and its capacity to remove alkalinity diminishes. The control valve initiates a regeneration cycle when the system reaches a certain point.
Regeneration: During the regeneration process, a brine solution (sodium chloride or potassium chloride) is introduce into the resin tank. The brine solution displaces the adsorbe alkaline ions on the resin beads, effectively regenerating the resin.
Rinse: After the regeneration process, the resin bed is rins with fresh water to remove any remaining brine and ensure the removal of any loose debris or resin fines.
Return to Service: Once the rinsing is complete, the dealkalizer system returns to the treatment mode, and the resin bed is ready to remove alkaline ions from incoming water again.
Significance & Advantages
The output of a DM plant is typically demineraliz water, which has a very low concentration of dissolve minerals and salts. Demineralized water is commonly use in various industrial processes, including boiler feedwater, cooling towers, pharmaceutical production, electronics manufacturing, laboratory applications, and more, where precise water quality and purity are essential.
Regular maintenance, including resin regeneration, monitoring of water quality, and occasional resin replacement, is necessary to ensure the continue performance and efficiency of a DM plant.
