Ion Exchange Principle

Cation resin exchanges dissolved cations (Ca, Mg, Na) for hydrogen ions. Anion resin exchanges anions (Cl, SO4, HCO3) for hydroxyl ions. Combined treatment removes virtually all dissolved salts producing demineralized water.

System Configuration

Two pressure vessels in series - cation exchanger followed by anion exchanger. Raw water flows through cation bed converting salts to acids. Acidic intermediate flows through anion bed neutralizing acids. Product water essentially mineral-free.

Cation Vessel

Strong acid cation resin in hydrogen form. Vessel with inlet distributor, resin bed 30-48 inches depth, freeboard for backwash expansion, outlet underdrain. Regenerated with sulfuric or hydrochloric acid restoring hydrogen form.

Anion Vessel

Strong base anion resin in hydroxyl form. Similar vessel design as cation. Regenerated with sodium hydroxide (caustic) restoring hydroxyl form. Type I resin removes silica, Type II more economical for non-silica applications.

Material Construction

FRP vessels resist acid and caustic exposure during regeneration. Internal distributors in corrosion-resistant materials. Stainless steel or plastic piping. Regenerant-resistant valves and controls.

Operating Pressure

Typical 50-100 psig service pressure. Pressure drop through each bed 10-15 psi when clean increasing to 20-30 psi at exhaustion. Total system pressure drop managed through proper sizing.

Water Quality

Inlet water pre-treated removing suspended solids and chlorine protecting resins. Product water conductivity typically 1-10 microsiemens/cm. Silica under 0.02 ppm with Type I anion resin. Quality depends on regeneration effectiveness.

Regeneration Cycle

Service exhausts resin capturing contaminants. Backwash loosens bed removing accumulated solids. Chemical regeneration restores exchange capacity. Rinse removes excess regenerant. Return to service. Cycle frequency based on water quality and throughput.

Applications

Boiler makeup water, pharmaceutical water systems, electronics manufacturing ultrapure water, laboratory rinse water, process industries requiring mineral-free water, and any application needing demineralized water.

Capacity Calculation

Resin volume based on water hardness, TDS, and required production rate. Typical exchange capacity 20-30 kilograins per cubic foot cation resin, 15-25 kilograins anion. Proper sizing balances capital versus regeneration frequency.

Automation

Control systems manage service, regeneration, and rinse cycles. Conductivity monitoring triggers regeneration at breakthrough. Flow totalizers track volume processed. Automated regenerant dosing ensures proper restoration.

Performance Benefits

Produces high-purity demineralized water. Proven ion exchange technology. Relatively low capital cost for moderate purity requirements. Simple operation with automated controls.

Construction Standards

Vessels per ASME Section X for FRP or Section VIII for metal. Piping per applicable codes. Chemical handling per safety standards. Complete documentation with capacity calculations and regeneration specifications.

ERGIL demineralization units provide reliable two-bed ion exchange water purification producing low-conductivity demineralized water for industrial applications.