MVR evaporation runs on electricity at 15–25 kWh per tonne of water (default 20). Multi-effect evaporation runs on steam at 0.33 / 0.28 / 0.25 tonnes per tonne for 3 / 4 / 5 effects. The cheaper currency at your site decides.
TOOL VISUAL
The annual purchased-energy bill of two evaporation routes on the same duty: MVR — a single-effect evaporator with a mechanical vapor recompressor, buying electricity at 15–25 kWh per tonne of water evaporated; and multi-effect — N vessels in series, buying steam at 0.33 / 0.28 / 0.25 tonnes per tonne for 3 / 4 / 5 effects.
Energy is 60–80% of lifetime operating cost on an evaporation train, and the choice between electricity and steam locks in that bill for 20–30 years. Regional price spreads of 3× flip the answer: the same evaporator that saves money on Scandinavian hydroelectricity can lose money on an inland-China coal-steam site.
Five inputs, two annual energy bills, one savings number. Default values reflect a mid-size project operating 7,920 hours per year (90% availability). Nothing is stored, nothing is sent.
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MVR = W × 20 kWh/t × Pelec × H
Multi-Effect = W × 0.28 t/t (4-eff) × Psteam × H
Savings = CostME − CostMVR
% Saving = Savings / CostME × 100
Specific consumption bands: MVR 15–25 kWh/t water (default 20, driven by compression ratio and BPE); 3-effect 0.33 / 4-effect 0.28 / 5-effect 0.25 t steam/t water.
Comparison applies to the default 4-effect configuration; 3-effect and 5-effect trains shift steam consumption to 0.33 / 0.25 t/t respectively.
Why the same evaporator can have radically different OPEX in different regions.
Two technologies, two energy currencies. MVR buys electricity: a compressor lifts process vapor to a higher pressure so it recondenses in the same heat exchanger, and every tonne of water evaporated costs 15–25 kWh of shaft work. Multi-effect buys steam: vapor boiled off in one effect heats the next, so one tonne of live steam evaporates 3–4 tonnes of water depending on the number of effects. Which bill is smaller depends almost entirely on where your site sits on the electricity–steam price map.
MVR consumption is band, not a point: 15–25 kWh/t water. The position inside the band is driven by compression ratio (set by the required temperature lift), boiling-point elevation of the feed and compressor type. Near-saturated NaCl brine with 10–15 °C BPE sits at the top of the band; clean low-BPE liquors sit at 15–18 kWh/t.
Multi-effect consumption falls with effect count: 0.33 t steam/t water at 3 effects, 0.28 at 4, 0.25 at 5 — steam economies of roughly 3.0 / 3.6 / 4.0. Each added effect buys another 15–20% steam saving but adds a vessel, more plot area and a larger condenser. Real trains running fouling or high-BPE feeds should expect 10–30% above these catalogue figures.
Five factors sit outside the model: (1) boiling-point elevation penalizes MVR disproportionately at compression ratios above ~1.8; (2) CAPEX differential of 20–40% for the compressor train; (3) maintenance — compressor overhaul every 5–8 years is a real cash event; (4) partial-load efficiency below 60% turndown; (5) CO₂ pricing, which increasingly favors electric drive — estimate the carbon side separately.
When you have an annual savings number, the next question is what it buys: feed it into the ROI Calculator for simple payback and annualized return.
This tool returns screening-grade values. Actual consumption can deviate ±30% depending on boiling-point elevation (near-saturated NaCl brines run 5–15 °C, Na₂SO₄ systems 3–10 °C), compressor efficiency curves, scaling propensity, condenser sizing and the temperature-difference budget across effects.
The comparison covers annual purchased energy only. CAPEX, maintenance, cooling-water cost, labor and depreciation are excluded — for the full project picture use the ROI Calculator.
This is a preliminary screening aid, not a process guarantee. For a firm comparison, contact the engineering team with your feed analysis and utility contracts.
Pair this energy comparison with our ROI Calculator — or skip the tools and request a process design package with both energy and CAPEX modeled for your actual feed.
Send your feed characterization (TDS, COD, main salts, viscosity), throughput and product targets — we respond with a preliminary process route within two business days.