Compressed Air & Gas Dryers

Heatless Desiccant Dryer

Bone-dry air down to −70 °C, with no heater, no hot surfaces and, if you need it, no electricity at all.

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A compact heatless desiccant dryer with twin pressure gauges and a control panel on its front

Product overview

Deep, dry air wherever you need it, with no heat

Our heatless desiccant dryer takes the water vapour out of your compressed air by pressure swing adsorption. It delivers pressure dew points of −20 °C, −40 °C or −70 °C, and regenerates its desiccant with a share of its own dried air, without heaters, blowers or steam.

Two towers of desiccant take turns: one dries your air while the other is regenerated, and they swap every few minutes, so drying never stops and your outlet dew point holds steady whichever tower is in service. At −40 °C, the air leaving carries less than 0.25 % of the water vapour that entered.

Drying and regeneration both run close to ambient temperature, so the dryer has no hot surfaces and draws very little power, and pneumatically operated versions need no electricity at all. That suits it to hazardous areas, offshore platforms, rolling stock, remote sites and drying right beside a single machine.

A twin-tower heatless desiccant dryer on a frame, with its filters, valves and controller
  • −70 °CLowest pressure dew point
  • Class 1ISO 8573-1:2010 water class at −70 °C
  • 99.77 %Of the water vapour removed at −40 °C
  • ZeroHeating energy for regeneration

Benefits

The problems it solves

Compression packs the water from eight cubic metres of air into one, and the air leaves your aftercooler saturated. Here is what that water does to a plant, and how the dryer stops it.

  • Rust in your pipework

    The problem

    Rust flakes block orifices, jam valve spools and score cylinder bores.

    How it solves it

    Air at −40 °C pressure dew point has a relative humidity of under 1 % at any pipe temperature above 0 °C, so internal rust stops forming.

  • Ice in the cold

    The problem

    Ice blocks outdoor instrument lines, rail brake systems and air lines that pass through cold stores.

    How it solves it

    −40 °C and −70 °C pressure dew points keep outdoor piping, cold-store lines and moisture-sensitive processes free of condensate and ice.

  • Heat where it isn’t allowed

    The problem

    Hazardous areas limit surface temperatures and prohibit electrical ignition sources, and offshore and remote sites have little space or power.

    How it solves it

    With no hot surfaces and optional pneumatic operation, the dryer can be installed in ATEX and IECEx zones, drawing typically tens of watts, or none at all.

  • Microbes in your air

    The problem

    Wherever air touches food or medicines, moisture lets microorganisms multiply in the network.

    How it solves it

    −40 °C pressure dew point is below the −26 °C threshold for microbial growth and meets BCAS Class 2 for air in direct contact with food.

  • Drains all over the plant

    The problem

    Drip legs, point-of-use drains and sloped runs collect condensate, and lose compressed air as they do.

    How it solves it

    A network carrying air at −40 °C needs none of them, and the dryer itself has no drain connection.

  • Dew point upsets

    The problem

    Brief overloads, inlet temperature spikes and start-up after a shutdown can push wet air downstream.

    How it solves it

    Short cycles keep the moisture front well inside the bed, and after start-up or an upset the dryer returns to its specified dew point within a few cycles.

Where it’s used

Where deep, dry air has to be simple and safe

From instrument air in hazardous zones to air that touches food, medicines and paint, a heatless dryer brings deep dew points wherever your air needs them.

  • Wine bottles moving along a bottling line

    Food and beverage

    Class 2:2:1 air for direct food contact under BCAS Guideline 102, and conveying of milk powder, sugar, flour and cocoa without caking.

  • Yellow tablets spilling from a medicine bottle

    Pharmaceuticals and healthcare

    Tablet coating, fluid-bed granulation and capsule filling, and medical air within the European Pharmacopoeia limit of 67 ppm v/v water.

  • Robots welding a car body on an assembly line

    Automotive and surface finishing

    Spray painting, powder coating and abrasive blasting, which all fail when moisture is present.

  • Blue plastic bottle caps in a moulded tray

    Plastics

    PET preform blowing at 30–40 bar g, and dry air for hygroscopic resins such as PA, PC and PET.

  • Test tubes of coloured chemicals in a laboratory rack

    Chemicals

    Reactor blanketing and handling of moisture-reactive materials such as isocyanates.

  • Electricity pylons and power lines at sunset

    Power generation

    Instrument air for dampers and valve operators, and dry air for high-voltage switchgear with pneumatic operating mechanisms.

Also instrument air in oil, gas, refining and petrochemical plants, including ATEX and IECEx zones, electronics and semiconductors at −70 °C, feed air for nitrogen and ozone generators, rail brake air, portable compressors in mining and tunnelling, laboratories and cold stores.

How it works

Dry, vent, purge, swap

While one tower dries your air at line pressure, the other is vented to atmosphere and swept with a little of the dry air. Expanded to atmospheric pressure, that air is dry enough to strip the water off the desiccant.

How a heatless desiccant dryer works: wet air rises through one tower of desiccant at line pressure and leaves dry, while the other tower is vented to atmosphere and swept from the top down by a metered share of the dry air, which carries the released water out through a silencer; the towers swap every few minutes, with no heater. Tower B half-cycle, 5 min Purge ≈ 5 s 235–255 s 40–60 s Wet air inPre-filterAfter-filter Dry air outPDP −40 °C / −70 °C Tower AdryingLine pressure Tower BregeneratingNear atmospheric Purge orifice14–20 % at 7 bar g Humid purge exhaust 12345Wet compressed airDry airDry purge air, expandedWater from the bedHumid purge exhaustOutside the dryer

  1. 1. AdsorbWet air enters the bottom of Tower A and rises through the desiccant, which adsorbs its water vapour. Dry air leaves the top of the tower for your network.

  2. 2. DepressuriseTower B’s inlet closes and its exhaust opens. The tower vents from line pressure to near atmospheric pressure within seconds, and the sudden pressure drop starts desorption.

  3. 3. PurgeA metered flow of dry air from the top of Tower A expands to atmospheric pressure, flows down through Tower B collecting the released water, and leaves through the silencer. Purge typically takes 14–20 % of rated flow at 7 bar g.

  4. 4. RepressuriseTower B’s exhaust closes, and purge air raises it back to line pressure, typically over 30–60 seconds, so the changeover causes no pressure dip or dew point spike.

  5. 5. Change overTower B takes over drying, and Tower A depressurises and regenerates. For −40 °C a typical cycle lasts 10 minutes, and for −70 °C it is commonly shortened to 4 minutes.

Typical figures for −40 °C pressure dew point at 7 bar g, with a 10-minute cycle.

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.

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