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A demineralization plant is a water treatment facility designed to remove dissolved mineral salts and ions, such as calcium, magnesium, sodium, chloride, sulfate, and bicarbonate, from water to produce high-purity or deionized water. This process is primarily achieved through ion exchange resins in a staged sequence involving cation and anion exchange.

Design and Process

• The demineralization process typically employs two main ion exchange columns: one with a strong acid cation resin that replaces mineral cations (e.g., Ca2+, Mg2+, Na+) with hydrogen ions (H+), and another with a strong base anion resin that replaces anions (e.g., Cl−, SO4²−, HCO3−) with hydroxyl ions (OH−).

• The H+ and OH− ions released combine to form pure water (H2O), effectively removing dissolved salts.

• Sometimes a mixed-bed unit, containing a mixture of both cation and anion resins, is used after the dual beds for further polishing to produce ultrapure water.

• Pre-treatment steps such as filtration or clarification often precede the ion exchange process to remove suspended solids and protect resin beds.

• Regeneration of exhausted resins involves chemical treatments with acid (for cation resins) and caustic (for anion resins) solutions to restore ion exchange capacity.

• Additional units like degassers may be included to remove dissolved gases such as CO2, and ultrafiltration systems may be used for colloidal silica removal.

Applications and Uses

• Providing high-purity water for boilers and steam generation in power plants, preventing scale formation and corrosion.

• Supplying ultrapure water for pharmaceutical manufacturing, electronics, and semiconductor industries.

• Producing process water for industrial applications requiring minimal dissolved solids.

• Used in laboratories and medical facilities for controlled water quality.

• Essential for industries requiring water free from mineral contaminants to protect equipment and product quality.

 

In summary, demineralization plants use ion exchange to remove dissolved mineral salts from water, employing cation and anion exchange columns followed by regeneration cycles. Their design is tailored to feedwater quality and required output purity. These plants are crucial in industries like power, pharmaceuticals, and electronics that need mineral-free water to ensure operational efficiency and equipment longevity.