MVR — Mechanical Vapor Recompression Evaporation
A mechanical compressor raises the pressure and saturation temperature of evaporated vapor so it becomes the heating steam for the same effect. Electrically driven, no live steam in steady state — the lowest-operating-cost evaporation route where grid power is available and steam is expensive.
Four Numbers That Define MVR
Reference ranges under typical operating conditions — where your project lands inside each range depends on the variables in the energy determinants table.
The MVR Vapor Loop
Latent heat is recycled inside a single closed loop: vapor is compressed to a usable condensing temperature, condensed on the same heat-transfer surface that generated it, and the condensed water leaves as clean distillate.
Simplified MVR Flow Diagram
One compression stage closes the loop — the temperature lift only needs to cover the boiling-point elevation plus the driving ΔT across the heat-transfer surface.
Evaporation
Feed liquid boils on the heat-transfer surface — falling film for clean low-viscosity feeds, forced-circulation for scaling or crystallizing service. See process configuration.
Vapor–Liquid Separation
The vapor body or separator disengages entrained droplets before the compressor — droplet carry-over erodes impellers and contaminates distillate.
Mechanical Recompression
A centrifugal or roots-type compressor raises vapor pressure and saturation temperature so it can condense against the boiling liquid — electrical energy substitutes for live steam.
Condensation & Distillate
Compressed vapor condenses on the shell side, releasing its latent heat to the evaporating liquid. Condensate exits as clean distillate, ready for reuse or discharge.
What an MVR Train Is Built From
Six modules make up every MVR plant. Some are manufactured in-house; others are integrated from qualified partners — engineering responsibility is never outsourced.
Vapor Compressor
Centrifugal or roots type, sized to the required temperature lift and vapor volume. The compression ratio is limited by compressor type — this is the hard ceiling on how much boiling-point elevation an MVR train can absorb.
Evaporator Body & Heat Exchanger
Falling-film or forced-circulation configuration selected by feed fouling tendency and viscosity — the same Dimension B decision as any evaporator, independent of the MVR energy strategy.
Vapor–Liquid Separator
Custom vapor bodies sized for vapor velocity and entrainment control. A larger body is the standard remedy when droplet carry-over threatens compressor internals or distillate quality.
Motor & Variable Frequency Drive
The VFD controls compressor speed against evaporator duty — part-load turndown without wasting compression work. Motor and VFD efficiency both enter the specific-energy balance.
Vacuum System
Liquid-ring pumps or ejectors remove non-condensable gases that would otherwise blanket the heat-transfer surface. Cooling water at 25–32 °C is required for condensation duty.
Automation & Control
PLC/SCADA loops holding the compression ratio, boiling temperature and feed rate in balance — including density and temperature instrumentation that protect the compressor against surge.
What Determines Where in 15–25 kWh/t You Land
Four variables set the number. Two of them come from your feed chemistry — which is why MVR economics must be screened against feed data, not catalog figures.
Figures reflect typical industrial ranges observed in operating references; project-specific selection requires heat and mass balance, utility cost modeling (steam vs. electricity) and compressor / boiler availability analysis.
Where MVR Wins — and Where It Doesn't
MVR is the default choice for new plants where grid capacity and power price are favorable. Find your situation below; the full side-by-side table lives on Compare Technologies.
When One Strategy Isn't Enough
MVR, multi-effect and TVR are not mutually exclusive. Hybrids are common when a single strategy cannot meet the energy target within CAPEX constraints.
MVR combined with — not opposed to — thermal routes
Four hybrid patterns cover most field deployments. Each is selected on project-specific heat and mass balance, not visible from reference tables:
For high-BPE feeds where MVR alone would push toward the upper end of the energy range, hybrid MVR + multi-effect keeps the compression ratio inside the compressor’s operating envelope. See the ZLD solution line for where pattern (c) is standard practice.
Limitations to Design Around
Compressor maintenance (bearings, seals) is the standing OPEX item; the maximum compression ratio is limited by compressor type; and higher boiling point elevation reduces the MVR benefit. MVR economics are electricity-price sensitive — screen against your utility contract, not against benchmark tariffs. All figures on this page are indicative ranges for preliminary screening, not a process guarantee.
MVR Questions We Answer Most
Recurring questions from engineers screening an MVR route for the first time.
Four variables: compressor pressure ratio, boiling point elevation of the feed, compressor isentropic efficiency (75–85% centrifugal, lower for roots), and motor / VFD efficiency. For BPE of 2–4 °C with centrifugal compression, expect 18–22 kWh per tonne. For BPE above 6 °C, expect the upper end of the range — or a hybrid MVR + multi-effect configuration.
Stable electrical capacity at the compressor rating — typically 200 kW to over 2 MW for industrial-scale plants, at 400 V or 690 V 3-phase — plus a small amount of start-up steam and cooling water at 25–32 °C for condensation duty. No live steam is consumed in steady-state operation.
No. MVR is mechanical recompression of process vapor by an electrically driven compressor (Dimension A energy strategy). TVR uses high-pressure motive steam through an ejector — no rotating equipment, but a compression ratio ceiling of roughly ≤1.5× per stage and dependence on motive steam at ≥8 bar(g). Vacuum / low-temperature evaporation is a separate operating-temperature choice that can combine with either.
Yes — but pair it with the right process configuration. High-TDS brines carry boiling point elevation that eats into the effective ΔT, and scaling feeds need forced-circulation service at 2–3 m/s tube-side velocity with the heater temperature rise held at ≤10 °C. The energy strategy and the heat-transfer configuration are orthogonal decisions; MVR constrains neither.
When electricity is expensive or unreliable relative to steam, when grid capacity at the compressor rating is unavailable, or when feed boiling point elevation is high enough to push the required compression ratio past the compressor type’s envelope. In those cases multi-effect with a TVR booster — or a hybrid — usually screens better. The comparison page carries the full decision table.
Screening an MVR Route?
Send us feed analysis (including TDS and expected boiling point elevation), throughput and site utility prices. We will return a preliminary MVR vs. multi-effect vs. TVR screening with indicative specific energy — not a brochure.