Dehumidifiers

Adsorption Dehumidifier

Bone-dry air for your rooms, stores and processes, even below freezing.

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A stainless steel adsorption dehumidifier with round duct connections and a control panel

Product overview

Dry air at any temperature, right down to sub-zero dew points

Our adsorption dehumidifier dries air by passing it through a slowly rotating desiccant rotor, a honeycomb of thousands of small channels holding silica gel, with molecular sieve added where very low dew points are needed. The desiccant attracts water molecules straight from the vapour, so your air is dried without being cooled and without liquid water forming inside the unit.

About three quarters of the rotor face dries your process air while the remaining quarter is regenerated by air heated, commonly, to 100–140 °C. The wheel turns continuously, so the dry air never stops, and the collected water leaves outdoors as humid exhaust.

Because adsorption responds to relative humidity rather than to the amount of water in the air, it keeps drying at 0 °C and below, and it does not frost up. It treats the air of a room, a store, a production enclosure, a ship's hold or a process, as a standalone unit or built into your air-handling system.

A large stainless steel adsorption dehumidifier with an air intake grille
  • −20 °C to −40 °CTypical outlet dew points
  • 0 °C and belowKeeps drying, with no frost build-up
  • 100–140 °CReactivation air, commonly
  • About 8.7 kg/hWater taken from 1,000 m³/h dried to −40 °C

Benefits

The problems it solves

Air always carries water, and people, wet processes and open doors add more. Here is what that moisture does, and how the dehumidifier stops it.

  • Processes that need very dry air

    The problem

    Dry rooms and moisture-reactive products need a relative humidity of a few percent at room temperature, or dew points well below 0 °C.

    How it solves it

    The rotor delivers dew points of −20 °C to −40 °C, and lower with pre-cooling and a purge sector, and holds them indefinitely.

  • Frost in cold stores

    The problem

    In a freezer store at −25 °C, humid air entering through doors deposits frost on floors, evaporators and packaging.

    How it solves it

    Air dried to a dew point below −25 °C stops that deposition, and the dehumidifier keeps drying below 0 °C without frosting up.

  • Sweating surfaces

    The problem

    In air at 20 °C and 50 % RH, a chilled pipe at 6 °C, a cold steel beam or a product from cold storage sweats and drips.

    How it solves it

    Any surface warmer than the air's dew point stays dry, so your pipes, products and moulds stay free of condensation.

  • Caking and sticky products

    The problem

    Sugar, salt, milk powder and fertilisers cake, gelatin capsules soften and hard candy becomes sticky.

    How it solves it

    Low relative humidity stops caking, clumping and softening in the products you make and store.

  • Corrosion and mould

    The problem

    Blasted steel flash-rusts within hours in humid air, and mould attacks paper, timber, textiles and stored grain.

    How it solves it

    Keeping humidity low stops corrosion, mould, caking, frost and condensation on your products and assets.

  • Heat going to waste

    The problem

    Steam, hot water, condenser heat and process waste heat are often rejected unused.

    How it solves it

    Reactivation can run on electricity, steam, hot water, gas or recovered waste heat, turning your surplus energy into drying capacity.

Where it’s used

Wherever moisture spoils what you make or store

From pharmaceutical suites to ships' holds, dry air protects products, processes and assets.

  • Yellow tablets spilling from a medicine bottle

    Pharmaceuticals

    Dry air protects hygroscopic powders during granulation, tabletting, capsule filling and blister packing.

  • Wine bottles moving along a bottling line

    Food and confectionery

    Keeps hard candy and chewing gum from becoming sticky, milk powder, sugar and spices free-flowing, and chocolate free of condensation.

  • Blue plastic bottle caps in a moulded tray

    Plastics

    Dry air around injection moulds running with chilled water prevents condensation that marks parts.

  • A hand mixing paint in open tins of colour

    Surface preparation and coating

    Keeps blasted steel inside tanks, ship blocks and pipelines free of flash rust until coating.

  • A naval warship at sea

    Marine and defence

    Ships' holds, laid-up vessels, aircraft and stored equipment preserved in dry air.

  • Electricity pylons and power lines at sunset

    Power generation

    Generators, turbines and boilers kept dry during shutdowns and lay-up.

Also lithium-ion battery dry rooms, cold stores and freezer tunnels, water and wastewater pumping stations, electronics storage to J-STD-033, bridge girders, cables and wind turbines, archives, museums and seed banks, and ice rinks.

How it works

Adsorb, turn, regenerate

A slowly turning desiccant wheel dries your air in one sector and is dried out itself by hot air in the other.

How an adsorption dehumidifier works: process air is filtered and passes through the upper three quarters of a slowly turning desiccant rotor, which adsorbs its water vapour, and the process fan delivers the dry, warmer air to the room. Heated reactivation air flows the opposite way through the lower quarter, drives the water back out of the desiccant, and the reactivation fan discharges it outdoors. Desiccant rotor Seal M Slow drive Rotor face 6–20 rev/h Process air in20 °C · 7.3 g/kgFilter Dry air to the roomProcess fan−20 °C dew point · 0.63 g/kgat least 16 K warmer Reactivation air inHeater100–140 °C Wet air to outdoorsReactivation fan27 g/kg · dew point near 30 °C 12345Humid airDry airReactivation sector, and heatHot reactivation airWet air, to outdoors

  1. 1. AdsorbFiltered process air enters the rotor's channels and meets desiccant that has just come out of regeneration. Water vapour is adsorbed on the channel walls, and the air leaves drier and warmer: dried from 7.3 g/kg to a −20 °C dew point, it warms by at least 16 K.

  2. 2. LoadThe slow drive turns the wheel at between about 6 and 20 revolutions per hour. Each segment spends about three quarters of a revolution in the process sector, and its water content rises as it goes.

  3. 3. Heat and releaseThe segment crosses the seal into the reactivation sector. Reactivation air, filtered and heated commonly to 100–140 °C, flows through it the opposite way, heats the desiccant and drives the water back out.

  4. 4. ExhaustThe reactivation fan draws the warm, humid air out and discharges it outdoors. It leaves at about 27 g/kg, with a dew point near 30 °C.

  5. 5. Cool and repeatThe hot, dry segment turns back into the process sector, where the incoming process air cools it, ready to adsorb again. Every segment runs through the cycle once per revolution, so the dry air flows without interruption.

Worked example: process air at 20 °C and 7.3 g/kg dried to a −20 °C dew point, with reactivation flow at one third of process flow.

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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