Compressed Air & Gas Dryers

Biogas & Natural Gas Dryer

Dry, steady fuel gas for your engines and boilers, with no liquid water in the line and no methane vented.

Download brochure Download questionnaire
A skid-mounted gas drying unit with two vessels, a heat exchanger, gauges and a large flanged cover

Product overview

Dry fuel gas, from the digester to your engine

Biogas leaves the digester fully saturated, and every metre of pipe cooler than the digester condenses part of its water. At 38 °C, water vapour makes up about 6.4 % of the gas by volume, or 46 g in every actual cubic metre.

Our dryer chills the gas with a water-glycol circuit, usually to 3–10 °C, so the excess water condenses, separates and drains through liquid-seal traps without letting gas escape. It then reheats the gas: chilled to 5 °C and reheated to 25 °C, it leaves at a relative humidity of about 28 %.

It handles digester biogas, landfill and sewage gas, biomethane and natural gas, and is built for hazardous areas, close to the digester, gas storage or engine it serves. With an adsorption stage, it also dries pressurised gas to pressure dew points below 0 °C, with no methane vented.

A skid-mounted gas drying unit with two vessels, a heat exchanger, gauges and a large flanged cover
  • 88 %Of the incoming water removed, 38 °C in and 5 °C out
  • 3–10 °CTypical chilling set point, which sets the dew point
  • About 28 %Relative humidity after reheating to 25 °C
  • ZeroMethane vented

Benefits

The problems it solves

Warm, saturated gas condenses water wherever it cools. Here is what that water does to your gas plant, and how the dryer stops it.

  • Engines tripping on low gas pressure

    The problem

    A water column only 10 mm high balances 1 mbar of gas pressure, so a small pool of condensate at a low point restricts or stops the flow.

    How it solves it

    With a dew point below every downstream temperature, no condensate pools in your gas lines, and engine trips caused by water end.

  • Acid attack on engines and pipes

    The problem

    H₂S and CO₂ dissolve in condensate and form an acid that corrodes pipework, blowers and valve seats, and attacks engine bearings and cylinder liners.

    How it solves it

    Dry gas reduces acid formation, oil degradation and deposits, extending your oil change intervals and time between overhauls.

  • Short carbon filter life

    The problem

    Water vapour competes with siloxanes for adsorption sites, and wet gas lets siloxanes break through to burn to abrasive silica in the engine.

    How it solves it

    Reheated gas at low relative humidity keeps adsorption sites free for siloxanes and H₂S, so your activated carbon lasts longer.

  • Unsteady engine output

    The problem

    Varying water content alters the heating value of the gas, disturbing air-fuel ratio control and raising the risk of misfiring and knocking.

    How it solves it

    Constant water content gives a constant heating value, so your engines hold their rated electrical output with fewer control corrections.

  • Gas escaping at drains

    The problem

    Uncontrolled condensate drainage releases methane and H₂S, and H₂S deadens the sense of smell above about 100 ppm.

    How it solves it

    Water leaves the gas at one defined point, through liquid-seal traps that drain it without letting gas escape.

  • Ice and hydrates in CNG

    The problem

    At CNG storage pressures of 200–250 bar, water condenses far above its atmospheric dew point, and ice and hydrates block regulators, filters and dispenser valves.

    How it solves it

    With an adsorption stage, pressurised gas is dried to pressure dew points below 0 °C, with its regeneration gas kept inside the process.

Where it’s used

Wherever gas is burned, upgraded or compressed

From farm digesters to fuelling stations, anywhere wet fuel gas has to reach an engine, burner or compressor dry.

  • Aerial view of a biogas plant with green digester domes beside farmland

    Agricultural biogas plants

    Gas from manure, energy crops and residues, dried before the combined heat and power engines.

  • Aerial view of round tanks at a sewage treatment works

    Municipal wastewater

    Sewage gas for on-site engines and boilers, dried ahead of activated carbon to keep siloxane deposits out of the engines.

  • An excavator working on a landfill at dusk

    Landfill sites

    Saturated gas collected under vacuum, dried to protect blowers, flares and gas engines.

  • Wine bottles moving along a bottling line

    Food and beverage processing

    Breweries, dairies, sugar mills, distilleries and starch plants burning biogas from their wastewater and residues in boilers.

  • A spherical gas holder beside a gasometer frame

    Biomethane upgrading

    Dried raw biogas for membrane, pressure swing adsorption, amine and water scrubbing plants.

  • A fuel nozzle in the filler of a white car

    CNG and bio-CNG stations

    Gas dried so that no water, ice or hydrates form at vehicle storage pressure.

Also pulp and paper effluent plants, natural gas distribution and industrial users, oil and gas production, and laboratories and pilot plants.

How it works

Precool, chill, separate, reheat

A chilled water-glycol circuit cools your gas until its water condenses out. The dry gas is then warmed back up, well below saturation, before it moves on.

How a biogas and natural gas dryer works: warm, saturated gas is precooled in a gas-to-gas heat exchanger, chilled by a water-glycol circuit so its water condenses, and the droplets are separated and drained through liquid-seal traps. The cold, dried gas is reheated in the same gas-to-gas heat exchanger and leaves through the gas blower. Wet gas in38 °C · saturatedCondensate out Dry gas out≈ 20 °C · RH ≈ 37 %Gas blower Gas-to-gas heat exchanger Liquid-seal traps Chilled heat exchanger 5 °C dew point 5 °C Separatorand demisterCondensate out Water-glycol chillerPumpHeat out 12345Wet raw gasChilled gasDry gas, reheatedCondensateCold glycolWarmed glycol

  1. 1. PrecoolWarm, saturated raw gas enters the gas-to-gas heat exchanger and gives up heat to the cold dried gas. Water begins to condense and drains to a liquid-seal trap.

  2. 2. ChillThe gas flows through the chilled heat exchanger, against the flow of the water-glycol coolant, and cools to its set point, typically 3–10 °C. Most of the water condenses.

  3. 3. Separate and drainThe separator and its demister catch the condensed droplets, and liquid-seal traps drain the condensate without letting gas escape. Ammonia, part of the H₂S and CO₂, and part of the siloxanes leave with it.

  4. 4. Reheat and boostThe dried gas returns through the gas-to-gas heat exchanger and warms by 15–20 K: chilled to 5 °C and reheated to 20 °C, its relative humidity falls to about 37 %. The blower then raises it to supply pressure, commonly 50–200 mbar, and adds compression heat.

  5. 5. The chilled glycol circuitA pump circulates the water-glycol coolant through the heat exchanger and back to the chiller, which rejects the heat to ambient air or cooling water. Glycol keeps the coolant from freezing, and its temperature is held high enough that no ice forms on the gas side.

Example figures for raw biogas saturated at 38 °C, near atmospheric pressure, chilled to 5 °C.

Get the full details

Our brochure covers it in detail, and our questionnaire tells us what we need to recommend the right one for your plant.

Download brochure Download questionnaire

Keep exploring

More from our range

Equipment for every stage of your compressed air, and our own engineers to test, commission and look after it.

Why Settle for Mediocrity When You Can Partner with the Best?

We are more than just another industrial solutions provider. We’re a partner in your success. With decades of experience and a team of experts dedicated to providing comprehensive solutions from equipment to service and sourcing, we’re confident in our ability to help you optimize your performance and achieve your business goals.

Speak with an Expert