Chemical & Process Technology: FAYF

Monday, June 23, 2008

FAYF - Dehumidification

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Chemical Engineering JUNE 2008 release has shared a new FAYF. This FAYF is related to some tips on Dehumidification.

What is Dehumidification ?

Dehumidification is a process to reduce the level of humidity in air to a level for good health, cleanliness and preserve structure & quality of material.

Why dehumidify air ?
Human health - As humid air can cause mold and mildew to grow inside homes, it potentially increases human health risks.

Prevent moisture regain
- Dried food such as rice, bread, etc are dry in nature to maintain it structure, avoid mold growth and low decaying process, . Maintaining moisture in air prevent dry food becoming wet.

Prevent condensation - Moisture in are contact with cold surface like refrigerant pipe, fridge, etc would cause condensation.

Prevent corrosion - Condensed water on metal surface would promote corrosion.

Drying - Dried air can be used to reduce moisture content in product.

How air is Dehumidify ?
Three methods are common used in dehumidifying. There are :
(i) Cooling
- Cool air below dew point and moisture in the air is condensed and drained out.

(ii) Adsorption

- Humidity is reduced with an adsorbent material as silica gel or activated alumina. Adsorption is a physical process where moisture is condensed and kept in material. Adsorbent material can be reactivated by passing hot gas.

(iii) Absorption

- Humidity is reduced with an absorbent material such as calcium chloride solution. Absorption involves a change in the physical or chemical structure of the material.

In this FAYF, only Cooling and Adsorption process are discussed.

In addition, the FAYF briefly compare the advantages and disadvantages of Cooling and Adsorption process. Basically cooling is economic and consider when dew pointing level is not that stringent. Adsorption process is used when a very dry air is required.