Recovering Flash Steam: Reusing Low-Pressure Vapor via Jetomat

INTRODUCTION

Whenever hot condensate drops pressure—at a trap outlet, flash tank, or vent—some of it “flashes” back into steam. That flash steam is valuable energy, but in many plants it’s vented or only partly recovered. Jetomat steam jet ejectors (a steam thermocompressor / steam jet compressor) solve this neatly: they pull low-pressure flash steam and recompress it so you can feed a medium-pressure consumer. The payoff is immediate—saving energy, fewer roof plumes, and better steam economy in heating systems like multi-effect evaporators and distillation reboilers.

WHAT IS FLASH STEAM RECOVERY WITH A JETOMAT?

A Jetomat is a controllable thermo vapour recompressor that uses a high-pressure motive jet to entrain low-pressure vapor (flash) and then, in a diffuser, converts the jet’s velocity back to pressure. That’s the classic steam jet ejector working principle—momentum exchange with no rotating parts.

Instead of installing a larger flash vessel or vent condenser alone, a controllable ejector mixes flash with motive steam and delivers usable mixed steam at the setpoint (e.g., 2–4 bar(g)).

COMPONENTS

1.     Controllable Motive Nozzle (with actuator)

• Converts motive steam pressure to high velocity; creates suction.

• Actuator/spindle modulates the nozzle design throat area → stable control and 3:1–5:1 rangeability.

2.     Suction Inlet & Mixing Chamber

• Connect to the flash source: trap manifold, flash tank, or condensate receiver vent.

• The jet entrains low-pressure vapor; momentum is shared in the mixing zone.

3.     Diffuser and Nozzle (pressure recovery)

• Converts velocity back to pressure so mixed steam can feed a medium-pressure user (e.g., 3 bar(g) reboiler).

4.     Instrumentation & Controls

• Primary control on mixed-steam pressure (or temperature); optional suction pressure/flow monitoring.

• Integrates with PLC/DCS; easy drop-in for existing steam equipment.

WHY BOTHER?

• Energy & fuel: Each 1 kg of recovered flash steam typically displaces ≈1 kg of fresh boiler steam at the same pressure—direct, miserable saving energy.

• Steam economy: In multi-effect evaporators, re-using flash as a driver for another effect reduces specific steam consumption (kg steam/kg product).

• Quality & stability: Ejectors give fast response and steady pressure, improving heat flux and heat transfer solutions in reboilers and calandrias.

• Maintenance: No rotating parts; fewer traps/vents to manage—simpler condensate and flash steam recovery system.

• Environmental: Smaller or no vent plumes → lower “thermal pollution.”

Where it shines

• Multi-effect evaporators (sugar, juice, dairy, gelatin, chemicals)

• Distillation & stripping (solvent recovery, alcohols, aromatics)

• Large trap manifolds and flash tanks at pressure drops

THE PHYSICS IN PLAIN ENGLISH

A) How much flash steam do I have?

When saturated condensate at pressure (P_1) is reduced to (P_2), a mass fraction (x_f) flashes:

[
x_f \approx \frac{h_{c}(P_1)-h_{c}(P_2)}{h_{fg}(P_2)}
]

• Example: Condensate at 8 bar(g) (Tsat ≈ 170 °C) drops to 0 bar(g).
  Using steam-table values, (x_f) is typically 10–15%.
  If a header sends 10 t/h condensate to atmosphere, ≈1.0–1.5 t/h becomes flash steam—often visible as a vent plume.

B) What does the ejector actually do?

• Motive steam: say 10 bar(g)

• Suction (flash): say 0–0.3 bar(g) at 100–105 °C

• Mixed: target 3 bar(g) supply to a reboiler/evaporator effect

With a feasible entrainment ratio ( \omega = \dot m_s / \dot m_m ) of 0.5–1.0, recovering 1,000 kg/h flash typically needs 1,000–2,000 kg/h motive, delivering 2,000–3,000 kg/h of mixed steam at 3 bar(g).

Rule of thumb: Every recovered kg/h of flash cuts fresh steam to that user by nearly 1 kg/h.

TWO TYPICAL SCENARIOS

1) Multi-Effect Evaporator (MEE) – “Drive the next effect”

• Before: Effect-1 condensate drops to a flash tank; vapor vents or is partly condensed.

• After (Jetomat): Ejector pulls flash from that tank and recompresses it to feed Effect-2 heater at ~3 bar(g).

Typical results:

• Specific steam to the MEE improved by 10–25%, depending on baseline venting.

• Faster pick-up and more stable calandria pressure (no PRV lag), improving throughput.

Example numbers (illustrative):

• Flash available: 1.2 t/h at ~0 bar(g)

• Motive: 10 bar(g), 1.6 t/h

• Mixed to Effect-2: 2.8 t/h at 3.0 bar(g)

• Fresh steam displaced: ≈1.2 t/h → annual saving = 1.2×8,000 = 9,600 t/y of boiler steam (multiply by your €/t).

2) Distillation Reboiler – “Stop venting the flash tank”

• Before: Trap manifold/flash tank vents 600 kg/h; reboiler uses fresh 3 bar(g) steam.

• After (Jetomat): Ejector entrains 600 kg/h flash, uses ~700–1,200 kg/h motive, and supplies 1,300–1,800 kg/h mixed to the reboiler.

• Effect: Fresh 3 bar(g) steam to the reboiler drops by ≈600 kg/h; roof vent goes quiet.

CONTROLS THAT KEEP IT SIMPLE

• Primary loop: Mixed-steam pressure control (e.g., 3.0 bar(g) ±0.05) by modulating the motive nozzle/valve.

• Secondary checks: Suction temperature/pressure to ensure you’re pulling vapor, not air; optional flow indication.

• PLC/DCS: Standard 4–20 mA or fieldbus; easy to add recipes for different products/batches.

• Response time: With a modern actuator, <2–5 s to setpoint—perfect for batch steps and load swings.

PRACTICAL PIPING & DESIGN TIPS

• Short suction run: Large-radius bends, no low pockets; insulate.

• Drainage: Make sure condensate drains cleanly to the flash source; avoid liquid slugging.

• Sizing inputs: Suction flow (kg/h), suction pressure/temperature, motive header pressure, target mixed pressure, allowable Δp to user.

• Turndown: Design for 3:1–5:1 motive turndown so nights/weekends stay stable.

• Polishing options: If a specific user demands very dry steam, add a small steam separator downstream—most process heaters accept saturated steam.

WHY AN EJECTOR BEATS “BIGGER FLASH TANKS” ALONE

• Throttling vs. recycling: Bigger vessels still rely on throttling/condensing; the steam jet Thermocompressor reuses vapor at process pressure.

• Fewer moving parts: No rotating compressor to maintain; the jet device is rugged and compact.

• System simplification: Often fewer traps/vents; your flash steam recovery system becomes integral, not an add-on.

• Improved heat transfer: Stable pressure and higher mass flow improve heater side coefficients—practical heat transfer solutions without PRV lag.

QUICK COST PICTURE

Recovering 600 kg/h flash for 8,000 h/y displaces 4,800 t/y of boiler steam.

• If your steam all-in cost is €6/t, that’s €28,800/y saved.

• If €10/t, that’s €48,000/y.
  These savings stack with maintenance reductions from fewer vents and simpler loops.

CONCLUSION

Flash steam isn’t waste—it’s work you can reuse. A Jetomat ejector turns low-pressure vapor from traps, flash tanks, and receivers into useful medium-pressure steam, boosting evaporator and reboiler performance while saving energy and calming your roof vents.

How to start (simple checklist):

1. Find the plumes: Measure flash flow (kg/h) at vents/flash tanks.

2. Pick a sink: Which user can take 2–4 bar(g) mixed steam (next effect, reboiler, LP header)?

3. Get a sizing pass: Ask for thermocompressor design (entrainment ratio, compression ratio, diffuser and nozzle geometry, turndown).

4. Pilot & prove: Track fresh-steam reduction, product rate, and stability for 2–4 weeks—then replicate site-wide.