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Double Membrane Gas Holder
| MOQ: | 1 SET |
| Price: | Please contact us |
| Standard Packaging: | Standard export wooden box |
| Delivery Period: | 5~60 days |
| Payment Method: | L/C,T/T |
| Supply Capacity: | 20 sets per month |
Double Membrane Gas Holder:
A Complete Technical & Buying Guide
You are sizing storage for an anaerobic digestion plant. The sales pages all sound the same. This guide explains how the holder actually works, how to size it, what the pressure numbers mean, what it costs over ten years, and where it quietly fails — written from the shop floor, not the brochure.
What a double membrane gas holder actually is
A double membrane gas holder is a flexible, low-pressure storage balloon for biogas and other neutral gases. It sits either on the ground on a concrete ring or bolted to the crown of a digester tank.
Unlike a steel gasholder with a heavy piston, it has no moving metal parts. It holds shape with air. The "double membrane" name comes from two fabric skins, plus a base membrane on standalone units:
- Inner membrane — the gas bladder. Raw biogas sits inside it. It expands when you make more gas and collapses when you draw gas down.
- Outer membrane — the weather shell. An explosion-proof blower keeps it inflated with air, which protects the inner skin from wind, snow, UV and hail.
- Base membrane — on a ground-mounted unit, it seals the floor so the whole system is gas-tight from the ground up.
The space between the inner and outer membranes is the support-air chamber. That chamber is the heart of the system, and most of the confusion about "pressure" starts there.
How it keeps a constant pressure (and why the numbers conflict)
Here is the part most suppliers get wrong on their own spec sheets. There are two pressures, and they are not the same thing.
When the digester pushes more gas in, the inner membrane swells. The control cabinet senses the rise and vents support air so the inner bladder still presses out at the set pressure.
When gas is drawn down, the blower adds support air to keep the dome rigid and the delivery pressure steady. The result: a near-fixed outlet pressure across a wide fill range.
Why do competitor sheets disagree so much? Because some quote the support-air figure, some quote the gas-delivery figure, and some quote a peak design value. When you ask for a quote, state the gas delivery pressure your engine needs. A single vague "operating pressure" line on a datasheet is not enough to engineer against.
Key specifications, and what they mean for you
These are the numbers worth checking against your project. The ranges reflect standard biogas fabrics; your supplier should hand you the fabric mill test report, not just a brochure figure.
How to size the holder (most buyers skip this)
A holder is a buffer between uneven gas generation and uneven gas use. Size it wrong and you either flare gas at peak or starve the engine at trough. The method is simple; the data is the hard part.
A practical first estimate
Buffer volume (m³) ≈ (peak hourly production − average hourly consumption) × hours of autonomyFor a farm AD plant with a strong day-night swing, the holder often lands at 30 to 60 percent of daily gas output. A steady industrial plant with grid-linked CHP can run smaller.
Do not size from peak daily production alone — that over-specs the fabric and the budget.
Worked example
Suppose a digester averages 80 m³/h of biogas but peaks at 140 m³/h in the afternoon, while the CHP burns a flat 100 m³/h. The gap is 40 m³/h at peak.
If you want two hours of buffer before the engine throttles, you need about 80 m³ of working storage — not the 1,900 m³ a daily-total figure would suggest. Getting this right is usually the difference between a sensible quote and a 30 percent overspend.
Double membrane vs steel vs concrete
The honest comparison buyers actually need. No technology wins everywhere.
The ten-year cost view
Steel holders look comparable on day one, then cost you for it. A 1,000 m³ steel wet-seal unit needs water heating through winter, a full repaint every 3 to 5 years as H2S attacks the shell, and crane time for inspection.
A membrane holder's ongoing cost is mostly blower electricity (a few hundred watts) plus one fabric swap around year 12 to 15. On a typical farm AD plant the membrane route lands well below steel on life-cycle cost, which is why it took most of the new-build market.
Where it fits
Honest limitations — when not to specify a membrane holder
Every competitor page sells this as the answer to everything. It is not, and a good supplier will tell you so before you buy.
- Pressure ceiling. Above roughly 50 mbar stored-gas pressure, move to a steel pressure vessel. The fabric is not built for it.
- H2S overload. Standard fabric is rated to about 8,000 ppm. Consistently higher, and you either desulfurize upstream or pay for a special laminate.
- Flame and impact. The membrane is flame-retardant (B1), not fire-proof. Keep it clear of open flame, hot exhaust runs, and vehicle or equipment impact. A steel shell wins where that risk is real.
- Extreme cold. Rated fabric goes to −40 °C, but condensation and ice at the base need a documented detail. Do not assume; verify the low-end test data for your climate.
What maintenance actually looks like
"Low maintenance" on a brochure means nothing without a schedule. Here is the realistic one.
Why specify through Mondes
Sichuan Mondes Green Technology Co., Ltd. builds double membrane gas holders and the Glass-Fused-to-Steel digester tanks they sit on, so the roof and the tank are designed as one system instead of two suppliers pointing at each other.
Fabrication runs under an ISO 9001:2015 quality system, membranes are 100% high-frequency welded, and every unit ships with the fabric test data and a clamp-profile drawing for your tank crown.
We would rather tell you when a membrane holder is the wrong call than win a sale and lose a reference. If your duty is high-pressure, flame-exposed, or above the H2S ceiling, we will say so and point you to the right structure.
Need a holder sized for your plant?
Send your digester output curve and the gas delivery pressure your engine needs. We will return a sized proposal with the fabric spec and a clamp drawing for your tank.
Email richie@scmondes.comFrequently asked questions
How does a double membrane gas holder keep a constant pressure?
An explosion-proof blower pushes ambient air into the gap between the inner and outer membranes. A pressure relief valve keeps that support-air pressure steady, usually 5 to 20 mbar. That air cushion presses down on the inner gas bladder from all sides, so biogas leaves at a near-fixed pressure no matter how full the holder is.
What working pressure should I specify?
Two numbers matter and people mix them up. The support-air pressure that holds the dome shape sits around 5 to 20 mbar. The stored-gas pressure you deliver downstream is typically 5 to 50 mbar depending on whether the holder is a low-pressure tank-top roof or a standalone unit. Tell your supplier the gas delivery pressure your CHP or boiler needs.
How do I calculate the buffer volume I need?
Buffer volume (m³) = (peak hourly gas production minus average hourly consumption) × hours of autonomy. A farm AD plant with a strong swing usually sizes the holder at 30 to 60 percent of daily gas output. Your process engineer should confirm against the real feedstock and digester curve.
How long does a double membrane gas holder last?
PVDF-coated polyester membranes typically carry a 15 to 20 year design life in normal biogas service. The base membrane on a standalone unit is planned for replacement around year 10 to 15. H2S load, UV and temperature all move that number, so ask for the fabric test data.
Can it be mounted on an existing digester tank?
Yes. Tank-top holders bolt to the rim of a Glass-Fused-to-Steel, epoxy-coated, stainless or concrete digester using a stainless clamp profile and seal gasket. That turns the roof into storage and saves civil works. The tank rim must carry the clamp load and present a flat, level crown.
Where should I not use a membrane holder?
Skip it for stored-gas pressure above roughly 50 mbar, for raw biogas with H2S far above 8,000 ppm without a special fabric, and for any location exposed to open flame or mechanical impact. A steel pressure vessel or a desulfurization step ahead of storage is the safer call.
Related reading
- Glass-Fused-to-Steel digester tanks — the tank your holder can bolt straight onto.
- Biogas storage tank systems — full storage and digester packages.
- Double membrane gas holders and energy storage safety — our earlier technical note.
