Sulfate Removal System (SRS)

Challenges of Sulfate in Caustic Soda Production:

High sulfate levels in brine lead to multiple issues in caustic soda plants, including:

1. Reduced Current Efficiency and Chlorine Purity: Sulfate ions can release oxygen at the anode, which reduces the anode’s current efficiency and lowers the purity of chlorine gas produced.
2. Membrane Longevity: Sulfate can form melamine salts with other compounds, damaging the ion-exchange membrane and shortening its lifespan.
3. Crystallization and Blockage: Excessive sulfate can increase sodium chloride content in brine and lead to crystallization, risking blockages in pipelines and pump impellers.

Traditional vs. Nanofiltration-Based Sulfate Removal:

Historically, caustic soda plants have relied on chemical precipitation methods, adding chemicals like barium chloride or calcium chloride to precipitate out sulfate. However, these methods bring several drawbacks:

• Toxicity and Safety Hazards: Barium chloride, a common chemical in this process, is highly toxic and requires careful handling.
• Environmental Impact: Barium sulfate precipitation introduces hazardous waste, requiring additional disposal and environmental management.
• Overdosing Issues: Excess barium must be added to prevent residual barium ions from exceeding safe limits, further increasing costs and waste.

Technical Specifications of the Nanofiltration Membrane:

• Molecular Weight Cut-Off: 200-300 Daltons, effectively filtering out divalent and multivalent ions like sulfate (SO₄²⁻), calcium (Ca²⁺), and magnesium (Mg²⁺) while allowing monovalent ions (e.g., Cl⁻, Na⁺) to pass through based on feed composition.

• Pore size is 0.5 to 1 nm
• Allow monovalent ions (sodium ions, chloride ions) pass through
• It has over 95% high rejection rate of divalent ions (sulfate ion)
• Material with an aromatic amide structure, which allows a relatively high operating pressure. Sometimes>5MPa.

• Durability and Stability: The membrane has a long service life, is highly resistant to chlorine and other harsh chemicals, and performs reliably under the demanding conditions of chlor-alkali production.

The Nanofiltration Sulfate Removal System (SRS) represents a transformative advancement for brine treatment in caustic soda plants. By providing a safe, cost-effective, and eco-friendly alternative to traditional chemical methods, SRS nanofiltration enhances brine quality, improves production efficiency, and contributes to sustainable operations in the chlor-alkali industry. With its high sulfate removal rate, durability, and compatibility with chlorinated environments, the SRS system is an ideal solution for modern caustic soda production needs.