VSEP Nanofiltration for Solvay‑Process Brines & Calcium Chloride Recovery
Reduce Thermal Load • Recover Value • Enable High‑Fouling Brine Treatment
Optimize your Solvay‑process calcium‑chloride recovery with VSEP Nanofiltration, the only membrane technology engineered to handle high‑fouling brines. By removing water before thermal evaporation, VSEP dramatically reduces energy consumption with calcium chloride recovery, critical because CaCl₂ brines have a high boiling‑point elevation, making evaporation extremely energy‑intensive.
Unlike conventional RO or spiral NF, VSEP thrives where osmotic pressure and scaling normally shut membranes down. It passes sodium chloride (ideal for downstream RO volume reduction) while retaining calcium‑rich liquor. It also functions as a membrane crystallizer, managing precipitation of gypsum, silica, and metal hydroxides without fouling, something traditional membranes cannot survive.
With VSEP, chemical plants gain:
- Lower thermal load on evaporators
- Fewer scaling and maintenance issues
- Higher yield CaCl₂ concentrate ready for recovery (some NaCl removed)
- Cleaner NF permeate suitable for efficient spiral‑RO polishing
Engineered for the harsh chemistry of Solvay spent liquor containing calcium chloride, VSEP provides the highest‑efficiency pretreatment available for downstream recovery systems.
Overview: The Solvay Process and Its Calcium Chloride Byproduct
The Solvay (ammonia‑soda) process is the world’s dominant industrial route for producing soda ash (Na₂CO₃). It reacts brine (NaCl), ammonia, carbon dioxide, and limestone derivatives to form sodium bicarbonate, which is then calcined into soda ash.
A major co‑product of the Solvay process is calcium chloride (CaCl₂), formed during ammonia recovery when ammonium chloride reacts with lime:
This CaCl₂ remains in the “spent liquor,” which also contains highly soluble sodium chloride and some sparingly soluble salts.
How Calcium Chloride Is Normally Recovered
Industrial plants typically recover CaCl₂ through evaporation and crystallization, concentrating the liquor to 35–45% before final crystallization or flaking. During this process, sparingly soluble salts are present and must be dealt with—conventional crystallizers can precipitate and manage salts such as gypsum (CaSO₄), sodium sulfate, silica, and metal hydroxides as the liquor becomes supersaturated.
The final CaCl₂ product is used worldwide for:
- Road de‑icing and anti‑icing (the largest global application)
- Dust suppression
- Oil & gas well fluids
- Concrete setting acceleration
- Industrial brines and desiccants
The Thermal Problem: High Energy Demand in Evaporation
Calcium‑chloride solutions have a high boiling point elevation, making evaporation energy‑intensive and costly. Plants seek to reduce water load before thermal processing, but this is challenging:
- RO cannot operate on Solvay spent liquor due to extreme osmotic pressure.
- Conventional NF or RO scaling occurs because sparingly soluble salts precipitate during concentration.
This is where VSEP becomes uniquely effective.
VSEP Nanofiltration: A Breakthrough for CaCl₂ Recovery
Why VSEP Works When Spiral‑Wound NF/RO Fails
VSEP’s vibrating membrane module shears the boundary layer, preventing scale adhesion and allowing operation on streams that quickly destroy standard membranes.
Unlike spiral‑wound membranes, VSEP NF can function as a “membrane crystallizer”, allowing controlled precipitation of:
- Gypsum (CaSO₄)
- Silica (SiO₂)
- Metal hydroxides / carbonates (Fe, Al, Mg)
These solids remain suspended instead of forming scale, allowing continuous, stable operation even on high‑fouling Solvay liquors.
Process Advantage: Selective Sodium Chloride Passage
Nanofiltration in VSEP allows monovalent ions like Na⁺ and Cl⁻ to pass, while retaining most divalent species. This means:
- NF Permeate = Mostly NaCl, at reduced TDS (low CaCl2 loss)
- NF Concentrate = Higher‑purity CaCl₂ stream with sparingly soluble salts removed as particulate matter
This separation is highly beneficial because NaCl is not needed for CaCl₂ buyers and contributes to high evaporation load.
After VSEP: Spiral RO Can Now Be Used on NF Filtrate
Because the NF permeate is mostly monovalent salts and far less scaling‑prone, it can then be:
- Volume‑reduced with conventional spiral‑wound RO,
- Achieve significant water removal at low energy,
- Produce a brine suitable for disposal or crystallization, depending on plant objectives.
- The spiral RO concentrate containing NaCl can be reprocessed and sent back to the front of the Solvay process for brine preparation.
VSEP makes RO possible by removing the fouling species first.
Typical Analytic Results — VSEP NF + Spiral RO
| Stream | % Solids | Conductivity | Volume | Sodium | Calcium | Chloride |
| Spent Liquor (CaCl2) | 13.0% | 143,000 µS | 100% | 12,000 mg/L | 22,000 mg/L | 74,000 mg/L |
| VSEP NF Concentrate | 17.4% | 164,000 µS | 42% | 12.000 mg/L | 38,000 mg/L | 110,000 mg/L |
| VSEP NF Permeate | 4.6% | 65,900 µS | 58% | 12,000 mg/L | 43 mg/L | 24,300 mg/L |
| Spiral RO Concentrate | 8.62% | 114,900 µS | 26% | |||
| Spiral RO Permeate | 0.2% | 4,400 µS | 26% |
- The VSEP NF Concentrate feeds the evaporator after concentration
- The VSEP NF Permeate feeds a spiral RO to concentrate NaCl
- The spiral RO permeate is discharged
- The spiral RO concentrate recycles NaCl for the initial brine solution
Thermal Load Reduction: The Core Economic Benefit
By removing 30–70% of the water load before evaporation (application‑dependent), VSEP:
- Reduces steam and fuel consumption
- Decreases evaporator duty cycles
- Minimizes maintenance from scale and fouling
- Lowers the cost of CaCl₂ production or waste‑liquor management
Because evaporation of CaCl₂ requires progressively more energy at higher concentrations, every liter of water removed upstream yields disproportionate energy savings.
VSEP Samples from Spent Liquor
VSEP Concentrate (on the right) shows concentrated CaCl2 and precipitated gypsum.
Why VSEP Is the Preferred Technology for Solvay Brine Pre‑Concentration
- Handles high‑fouling brines with gypsum, silica, sulfate, metals
- Selectively removes sodium chloride via NF
- Reduces evaporation energy load dramatically
- Enabling step that makes downstream RO possible
- Produces higher‑purity CaCl₂ concentrate for sale
- Proven performance on industrial Solvay‑process liquors
Optimize Your Solvay Process Brine Treatment with VSEP
Chemical processors worldwide rely on VSEP to handle the streams that conventional membranes cannot.
If your Solvay plant seeks:
- Lower thermal requirements
- Reduced scaling in evaporators
- Higher‑value CaCl₂ production
- Lower waste‑brine volumes
- Superior energy efficiency
Then VSEP Nanofiltration is the most advanced and cost‑effective solution available.
Contact VSEP Engineering Today
Learn how we can customize a full‑scale treatment system tailored to your Solvay calcium‑chloride brine.
Request a technical evaluation
Ask about pilot testing for your exact brine chemistry
About New Logic Research & VSEP Technology
A Proven Leader in Industrial‑Scale Membrane Innovation
For more than three decades, New Logic Research has been a trusted engineering partner to the world’s most demanding industrial processors. The company is best known for developing VSEP (Vibratory Shear Enhanced Process) membrane systems—uniquely engineered solutions designed to treat tough, high‑solids, high‑scaling, and high‑viscosity process streams that defeat conventional spiral‑wound RO/NF technology.
VSEP systems have been adopted across major industries including chemicals, refining, mining, pulp and paper, wastewater treatment, and power generation, where operators require maximum uptime, scaling resistance, and predictable performance under extreme operating conditions. Their vibratory membrane architecture provides orders‑of‑magnitude higher shear at the membrane surface versus traditional membranes, allowing VSEP to operate successfully on streams containing crystallizing salts, colloids, oils, and abrasive particulates—applications where standard NF/RO would quickly foul or fail.
In chemical production and brine‑management applications, including Solvay‑process spent liquor, VSEP has become a go‑to technology because it can function as a membrane‑based crystallizer, allowing controlled precipitation of gypsum, silica, carbonates, and metal hydroxides without scaling or plugging. The result is a robust, energy‑saving method for pretreating brines that would otherwise require costly thermal evaporation as their first processing step.
By combining deep process‑engineering expertise with patented membrane technology, New Logic has established itself as a global credibility leader in high‑fouling liquid separation. Its systems are known for exceptional reliability, low operating cost, and the ability to solve separation challenges previously considered impossible—making VSEP an ideal fit for the Solvay calcium‑chloride recovery process and other industrial brine‑concentration applications.