Sustainable Industrial Quality Water Through Thermal Engineering
Producing high-purity distillate from seawater — powered by waste heat, solar, or nuclear energy.
Overview
Thermal desalination is the process of evaporating and condensing water under vacuum conditions. This allows feed steam to be multiplied to produce distilled water with less than 2 ppm total dissolved solids from seawater containing 35,000–40,000 ppm.
This is achieved through a cascading series of effects operating at progressively lower pressures and temperatures. Each stage recovers energy from the previous stage, maximising thermal efficiency until the lowest practical temperature is reached.
How It Works: The Multi Effect Distillation (MED) Process
Our core desalination technology uses a series of vessels (effects) at progressively lower pressures to evaporate and condense water efficiently.
Steam Entry
Steam enters the first effect and evaporates seawater under vacuum.
Energy Cascade
Vapour from Effect 1 becomes the heat source for Effect 2 at a lower temperature and pressure.
Multi-Stage Recovery
The cascade continues through multiple effects recovering energy at each stage.
Distillate Collection
Distillate is collected from every effect producing high purity water (<2 ppm TDS).
Steam Supply Integration Options
| Steam Supply Method | When to Use | Notes |
|---|---|---|
| Vacuum Vapour Generator (VVG) | Flue gas waste heat available | Our proprietary innovation |
| Thermo Vapour Compressor (TVC) | Pressurized steam at 5–10 bar(a) | Standard method, TVC sourced externally |
| Low Temperature Flash (LTF) | Hot water available | Simple flash process |
Where Thermal Desalination Works
Most effective where heat is already available, enabling freshwater production with minimal additional energy input.
| Heat Source | Industry Example | Steam Supply |
|---|---|---|
| Thermal Power Plants | Coal, gas, or combined cycle plants | TVC / VVG |
| Solar Thermal Plants | Linear Fresnel Reflector (LFR) fields | TVC |
| Nuclear Facilities | Research reactors, nuclear power plants | TVC |
| Waste Flue Gas | Cement, steel, glass, or process industries | VVG |
| Low-Grade Waste Heat | Any industry rejecting heat to atmosphere | VVG / LTF |
| Ocean Thermal Gradient | Island and coastal installations | LTTD |
Why Thermal Desalination is a Long Term Solution
Exceptional Energy Efficiency
Due to the cascading nature of energy transfer, thermal desalination is inherently energy-efficient at just 1.5–3 kWh/m³. Compare this to Reverse Osmosis (RO) at 3–6 kWh/m³ — and RO cannot use waste heat at all.
| Metric | Value |
|---|---|
| Electrical energy consumption | 1.5–3 kWh per m³ |
| Primary energy source | Waste heat (essentially free) |
| Pumping power | Minimal — vacuum operation |
Low Chemical Consumption
Thermal desalination requires only preventive dosing to discourage scaling. No high pressure membranes, no frequent chemical cleaning cycles.
- Lower operating costs
- Reduced environmental impact
- Simplified maintenance
High-Purity Output
Produces water with less than 2 ppm TDS — significantly purer than typical RO permeate — ideal for:
- Boiler feed water
- Process water for sensitive applications
- Drinking water (after mineralization)
Vacuum Vapour Generator (VVG)
Our Innovation — Rethinking Low-Grade Waste Heat Recovery
The VVG is a direct vapour generation heat recovery device operating under vacuum conditions. Instead of heating large quantities of circulating hot water and subsequently flashing it, the VVG integrates these functions into a single compact unit.
Learn More About VVG →
Low Temperature Thermal Desalination (LTTD)
A niche technology using the natural temperature gradient of the ocean. Warm surface seawater evaporates under deep vacuum, and the vapour is condensed using cold deep-sea water.
Applicability: Limited to specific coastal/island locations with access to deep cold water (600–1000m depth).
Our Experience: 3 × 150 m³/day plants delivered to Lakshadweep Islands.
Construction & Design Quality
Designed for long service life using the technology license from Dr. Marco Rognoni, Water Edge Technologies, Italy.
| Design Parameter | Specification |
|---|---|
| Design Life | 25 years |
| Guaranteed Availability | 95% |
| Annual Downtime | 5 days/year for preventive maintenance |
| Material Standards | Duplex Steel, Titanium Gr 2, SS 316L |
Rubber Grommet Innovation
A key innovation in our desalination plants is the use of rubber grommets to fix tubes to tube sheets. This:
- Avoids direct contact between dissimilar metals
- Prevents galvanic corrosion
- Extends tube life significantly
- Simplifies tube replacement
Key Projects
| Project | Location | Capacity | Technology | Year |
|---|---|---|---|---|
| RAMDAS | Narippaiyur, TN | 144 m³/day | Solar MED-TVC | 2011 |
| Mini Solar Desal (DST) | Kanyakumari, TN | Pilot scale | Solar MED | 2018 |
| NTPC Simhadri | Andhra Pradesh | 120 m³/day | Flue Gas LTF-MED | 2017 |
| Lakshadweep Islands | Amini, Kadamat, Chetlat | 3 × 150 m³/day | LTTD | 2018–24 |
| OSCOM IREL | Odisha | 2 × 250 m³/day | MED-TVC | 2020–23 |
| BARC | Mumbai | R&D scale | Nuclear MED-TVC | 2015 |
Why Choose Vapour Desal Technologies?
- Proven results under Indian field conditions — from tropical islands to industrial sites
- 25-year design life with 95% guaranteed availability
- Design license from Dr. Marco Rognoni — a global pioneer in thermal desalination
- Proprietary innovations like VVG and rubber grommet tube fixing
- Integrated with solar, nuclear, and flue gas heat sources
- High-grade materials — Duplex Steel, Titanium Gr 2, SS 316L
- Decades of experience in custom evaporator and pressure vessel engineering