The purpose of an experiment was to answer what differences there are between the usual silica gels when used in an adsorber in the field. For this comparison 0.5 kg, each of the silica gels Orange-Green (OG), Orange-Colorless (OF), Blue-Pink (BR) and the KC Dry Beads OC (KC) are examined.

The test conditions for all adsorbents are based on a mass flow of 46.6 g/h. This is calculated over a volume flow of 50 l/min, a temperature of 20°C and a relative humidity of 90%. All tests show behavior characteristic of silica gel. The breakthrough curves differ only at high loadings, due to the different maximum loadings.

The loading over time is also absolutely comparable between the silica gels. Differences can only be seen in the maximum loading.

All silica gels show the same behavior in water absorption. Only the differences at high loads can be justified by the varying maximum loadings. However, this maximum loading is well above the time of color change and is secondary to use in aeration dryers.

The loadings of the color envelopes vary greatly. The silica gel KC dry beads OC achieves the color change at the lowest loadings. As a result, the service life, the breakthrough curve and the water absorption take the lowest values. In contrast to this is the silica gel orange-colorless. This silica gel reaches the color changes only at high loads. This results in a long service life, a high breakthrough curve and a large amount of registered water. The orange-green and blue-pink silica gels have comparable properties in color change.

Silicagel Orange-Green

KC Dry Beads

Figure: Photos show adsorbers at 10%, 20% and 30% total loading, silica gel 0.5kg (dry).

Conclusion

The differences in the ratios are due to the moisture indicators. For systems with a requirement for low relative humidity, the Silicagel KC dry beads OC is most suitable. The early colour changes prevent the entry of a large amount of water. This is at the expense of the service life. The Silicagel Orange Colourless is suitable for systems where the service life is more important than the amount of water introduced. For all standard applications the Silicagels Orange-Green and Blue-Pink are best suited.