Compressed Air & Gas Dryers

Heated Desiccant Dryer

Deep, steady dew points around the clock, with heat rather than your compressed air doing most of the regeneration.

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A twin-tower heated desiccant dryer with its control cabinet and purge heater

Product overview

Deep dew points for big plants that never stop

Our heated desiccant dryer takes the water vapour out of your compressed air by adsorption, and regenerates its desiccant with heat. It delivers a pressure dew point of −40 °C as standard, and −70 °C with a molecular sieve bed, so no condensation forms in pipes, instruments or processes that stay above that dew point, including outdoor pipe racks in winter and lines through cold rooms.

Two towers of desiccant take turns: one dries your air for several hours while the other is regenerated, then they swap. Heat raises the vapour pressure of the water held on the desiccant by several hundred times, so a modest flow of hot purge air carries it away.

Because the heater supplies most of the regeneration energy, little dry air is spent on purging: averaged over a full cycle, it is commonly quoted at 5–8 % of rated flow. That makes it the natural choice for continuous, high-flow duty in your central compressor house.

A large twin-tower heated desiccant dryer on a skid, with its heater and control panel
  • −40 °CPressure dew point as standard
  • −70 °CPressure dew point with molecular sieve
  • 5–8 %Of rated flow used as purge, as commonly quoted
  • 99.77 %Of the water vapour removed at −40 °C

Benefits

The problems it solves

Compressed air leaves the aftercooler saturated, and every surface cooler than the air condenses more water. Here is what that water does to a plant, and how the dryer stops it.

  • Rust in your pipework

    The problem

    Rust scale blocks orifices, jams valve spools and scores cylinder bores.

    How it solves it

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

  • Frozen lines and instruments

    The problem

    Ice blocks outdoor instrument lines and air lines through cold stores, and a frozen instrument loses control of your process.

    How it solves it

    −40 °C as standard, and −70 °C with molecular sieve, keeps outdoor lines, cold-store piping and sensitive processes free of condensate and ice.

  • Purge that eats your air

    The problem

    On a plant compressing 5,000 m³/h, each 1 % of flow used as purge is 50 m³/h of compressed air, 438,000 m³ a year of continuous running.

    How it solves it

    Heat supplies most of the regeneration energy, so average purge is commonly quoted at around 5–8 % of rated flow.

  • Dew point swings

    The problem

    Short overloads and hot inlet air push moisture towards the outlet of a desiccant bed.

    How it solves it

    Each tower is thoroughly regenerated by heat, and the dry reserve at the outlet end of the bed absorbs short overloads and inlet temperature spikes.

  • Worn valves and dusty beds

    The problem

    Every changeover vents a tower, cycles the valves and moves the desiccant beads against each other.

    How it solves it

    A typical 8-hour cycle keeps depressurisations to a few a day, so valves operate less often, blowdown losses are small and desiccant attrition is lower.

  • Audits and specifications

    The problem

    Regulated plants release product only against a documented record of compliant dew point.

    How it solves it

    The dryer sets the ISO 8573-1:2010 water class, Class 2 at −40 °C and Class 1 at −70 °C, and continuous dew point records support GMP and HACCP audits.

Where it’s used

Where big plants need deep, dry air

Heated regeneration pays off on large central plants running around the clock, and deep dew points matter most where your lines run outdoors or through the cold.

  • Molten metal pouring from a ladle in a foundry

    Steel, aluminium and metals

    Large networks across outdoor yards, rolling mills and furnace areas, where freezing and corrosion stop production.

  • Electricity pylons and power lines at sunset

    Power generation

    Instrument air for dampers, valve actuators and soot-blower controls, and dry air for pneumatically operated high-voltage switchgear.

  • A worker pouring concrete over steel reinforcement

    Cement, glass and mining

    Long outdoor air lines, pneumatic conveying of powders and pulse-jet bag filter cleaning, kept free of blockages and caking.

  • Test tubes of coloured chemicals in a laboratory rack

    Chemicals and fertilisers

    Dry air protects moisture-sensitive reactions, catalysts and hygroscopic products during conveying and storage.

  • 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 and flour without caking.

  • Robots welding a car body on an assembly line

    Automotive

    Large, continuous flows for spray painting, robotic tools and leak testing in paint shops, body shops and powertrain plants.

Also central instrument air in oil, gas, refining and petrochemicals, pulp and paper, pharmaceuticals, −70 °C air for electronics and semiconductors, feed air for nitrogen generators, drying of nitrogen, carbon dioxide and natural gas, and air-jet looms in textiles.

How it works

Dry, heat, cool, swap

While one tower dries your air, the other is vented, heated and cooled, ready to take over. Hot purge air flows down the bed from its outlet end, so the part that sets your dew point is regenerated first.

How a heated desiccant dryer works: wet air rises through one tower of desiccant and leaves dry, while the other tower is vented to atmosphere, heated from the top down by a metered flow of hot dry purge air that carries the water out through a silencer, then cooled and repressurised before the towers change over. Tower B’s regeneration HeatCool ≈ 2–3 h ≈ 1 h Wet air inPre-filterAfter-filter Dry air out−40 °C PDP Tower AdryingLine pressure Tower BregeneratingNear atmospheric Purge heater150–200 °C Hot, humid exhaust 12345Wet compressed airDry airHot purge airHeated desiccantHot, humid exhaustOutside the dryer

  1. 1. AdsorbWet air rises through Tower A, where the desiccant holds its water vapour, and leaves the top dry, at −40 °C pressure dew point as standard. In a common arrangement each tower dries for 4 hours at a time.

  2. 2. DepressuriseTower B's inlet closes and its exhaust opens, venting it to near atmospheric pressure. The venting rate is limited so the escaping air does not lift and grind the bed.

  3. 3. HeatA metered flow of dry air from Tower A is expanded, heated, typically to 150–200 °C for activated alumina, and passed down through Tower B. A thermal front moves down the bed, and the released water leaves through the silencer as hot, humid air. When the exhaust temperature rises, the whole bed has been heated.

  4. 4. CoolThe heater switches off and unheated dry purge air keeps flowing until the bed is close to purge air temperature, so it returns to service without a temperature or dew point spike.

  5. 5. Repressurise and change overThe exhaust closes and dry air raises Tower B to line pressure. Tower B then takes over drying, and Tower A begins its own regeneration.

Typical figures for an 8-hour cycle with activated alumina, each tower drying for 4 hours.

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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