In humidifiers and air chambers water vapour is needed for the process of air treatment. Water vapour can be provided by steam generators, by spraying or evaporation on a surface which is in contact with the air needed to be moistened.
Water treatment for humidifiers and air chambers is similar to the water treatment for low pressure steam boilers. It additionally needs dosing of biocides and TDS to prevent any problems caused by excessive thickening and exceeding solubility of individual types of salt.
PREPARATION OF SUPPLYING WATER
Losses due to evaporation or TDS need to be replaced by supplying water. Such water must be prepared in the way that does not cause formation of sediments, lining or corrosion in the system.
To prevent formation of sediments and linings we need to remove from the supplying water some substances which could form such sediments. This can be achieved by means of ion exchange; softening, decarbonisation and demineralisation, or by means of membrane separations (reverse osmosis).
To protect system materials against corrosion and linings, we need to inject into the supplying water corrosion inhibitors, hardness stabilisers and dispersants or multifunctional chemicals which contain all the needed components. Only the right concentration of such chemicals in the system water can enable efficient system protection. In the system with stable water quality, upon the supposition that also supplying water is of good quality and stable, it is possible to inject chemicals proportional to the flow of supplying water. In other cases we need to regularly control the level of inhibitors and to supply them additionally if needed.
The corrosion dynamics can be ascertained and estimated with measurements of weight loss on corrosion coupons. These must be embedded in the circulation in accordance with the appropriate standards.
SYSTEM WATER TREATMENT
System water is thickened and contains impurities which enter the system through their contact with the air. The water temperature is usually around 20?C. Such circumstances are favourable for formation and growth of microorganisms (algae, fungi and bacteria). Bio-films and accumulation of algae represent a constant threat for infections.
To prevent microbiological growth in the system water we need to inject biocides. It must be emphasised that with the use of biocides we do not achieve water sterility, but we control biological growth and keep it within acceptable limits. There are two methods of dosing biocides available shock dosing and constant dosing.
With the occasional shock dosing we take measures when biological growth exceeds the desired level. Preventively we can dose chemicals several times a week, or we decided for biocide on the basis of regular biological tests.
SWith constant dosing using much lower concentration as the one used in shock dosing we want to prevent biological growth in the system water.
When using system biocides the so called resistance of microorganisms can appear which demands replacement of the dosing recipe.
