Silicagel


SILICAGEL

Silicagel DE EN

adsorbents silicagel

 

GIEBEL Adsorber® Silicagel

Silica gels are the most common desiccants and consist of 99% silica (SiO2). For use in ventilation dryers for ventilation of hydraulic power units, gears, storage tanks, transformers, etc., the silica gel is orange-green due to the high water absorption capacity of up to approx. 40% of the dry mass, a simple regeneration in the furnace, safe handling, and of the good contrast color indicator, the most suitable drying agent.

With a granule size of 2-5 mm spheres, the pressure build-up is very low and the gap volume optimal to ensure a very good contact of the water molecules to the silica gel surface.

With a properly designed adsorber, dew points of up to -40 ° C are achieved. Depending on the selection of the color indicator in the silica gel, the drying efficiency and the maintenance interval of an adsorber can be influenced. It can be selected from very strong drying and short maintenance interval to a weaker air drying and a long maintenance interval.

Applications:

  • Huydraulic units
  • Gear
  • Storage tanks
  • Barrel & IBC
  • Transformers

Downloads

  Productflyer

  Product Data Sheet (colorless)

  Product Data Sheet (orange-colorless)

  Product Data Sheet (orange-green)

   More documents


Features

Varieties of silcia gels

A distinction is made in fine-pore silica gels and wide-pore varieties. Fine-pore silica gels have a higher water adsorption at low partial pressures. Wide-pore silica gels have a smaller inner surface, but larger pores. Fine-pore silica gels are used much more frequently in the dehumidification because they are hydrophilic due to the larger specific surface area and the greater number of silanol groups than wide-pore.

Material and technical data

  • Chemical designation: Amorphous silicon dioxide
  • Composition: SiO2
  • CAS-Number: SiO2     63231-67-4

Fine-poreWide-pore
Appearance and shapeRound, solid ballsRound, solid balls
Grain sizemm5.005.00
Bulk densitykg/l70.000.60
Pore volumeml/g35.007.00
Crushing strengthN>200-
Specific surfacem²/g600.00300.00
Silicon dioxide SiO2%99.0099.80
Trace elements%1.000.20
Water adsorption capacityml/kg>370>70

 



Pore distribution

In fine-pore, microporous silica gels the centre of gravity of the pore radius distribution is 1-2 nm (10-20 Å).

In wide-pore mesoporous silica gels the pores are 2-20 nm (20-200 Å).

porenverteilung
Pore distribution of fine-pore and wide-pore silica gel


Adsorption kinetics

Critical to the use of silica gels as drying agents are the binding energies, and the loading capacity. For the first molecular layer, the binding energy is 5.140 kJ / kmol.

With increasing loading on multi molecular level, this value drops sharply. This results in a slowing of water absorption in a bulk of silica gel.

adsorptionskinetik
Slowing adsorption velocity with increasing loading


Equilibrium loading

Combining fine-pore silica gel-water corresponds to a convex isotherme type. The isotherme shows a steep rise. The mono molecular occupancy of the silica gel is complete at about 30%, then takes a multi-layered occupation of adsorbent surface and capillary instead. At an adsorption capacity level of about 35% it occupies as a plateau and rises slightly.

adsorptionsisothermen
Adsorption isotherms of fine-pore and wide-pore silica gel
isothermen
Isotherms fine-pore silica gel at 20o C, 40o C and 60o C

Varieties of silcia gels

A distinction is made in fine-pore silica gels and wide-pore varieties. Fine-pore silica gels have a higher water adsorption at low partial pressures. Wide-pore silica gels have a smaller inner surface, but larger pores. Fine-pore silica gels are used much more frequently in the dehumidification because they are hydrophilic due to the larger specific surface area and the greater number of silanol groups than wide-pore.

Material and technical data

  • Chemical designation: Amorphous silicon dioxide
  • Composition: SiO2
  • CAS-Number: SiO2     63231-67-4


Pore distribution

In fine-pore, microporous silica gels the centre of gravity of the pore radius distribution is 1-2 nm (10-20 Å).

In wide-pore mesoporous silica gels the pores are 2-20 nm (20-200 Å).


Adsorption kinetics

Critical to the use of silica gels as drying agents are the binding energies, and the loading capacity. For the first molecular layer, the binding energy is 5.140 kJ / kmol.

With increasing loading on multi molecular level, this value drops sharply. This results in a slowing of water absorption in a bulk of silica gel.


Equilibrium loading

Combining fine-pore silica gel-water corresponds to a convex isotherme type. The isotherme shows a steep rise. The mono molecular occupancy of the silica gel is complete at about 30%, then takes a multi-layered occupation of adsorbent surface and capillary instead. At an adsorption capacity level of about 35% it occupies as a plateau and rises slightly.



Regeneration of silica gels

In practice, the most common method used to regenerate silica gel is to increase the temperature. In the desorption of water vapor from silica gel, the temperature must be above 100°C. Recommended for regeneration are temperatures between 150°C to 175°C. However, bearing in mind that one is damaged in the silica gel applied color indicator at these temperatures. Therefore, a regeneration temperature is specified from 121°C for silica gel with color indicator and should not exceed 140°C.

Silica gel Regeneration



Aging of silica gels

If fine-pore, colorless silica gel is regenerated at a temperature of 150°C, the equilibrium concentration decreased after 100 cycles by about 20% and the half value diffusion coefficient by 32%. Thereafter, the equilibrium loading and the diffusion coefficient reaches a limit value, which is up to 500 cycles no longer significantly below.

aging
Change equilibrium loading and half value diffusion coefficient



Adsorption of further substances

Besides water, also other substances can be adsorbed by silica gels. To ensure the optimal choice of the adsorbents the substances and their diffusion coefficient should be known facing silica gel.

MixtureInert gasTemperature [°C]Pressure [bar]
strongly boundweaker bound
COO2-0; 1001.00
CO2O2, CO-100.001.00
H2OC6H6N1 (1 bar)50.001.00
C2H4C2H4-0.003.00
C3H8C2H4, C3H8-0.001.00
C3H6C2H4, C3H8-0-40; 251.00
i-C4H10n-C4H1025.001.00
C6H6n-C6H14Air (1 bar)70.000.00
CH3OHC6H6, H2ON2 (1 bar)50.001.00
CH3OHC6H625.001.00

Mixture (decreased binding forces)Inert gasTemperature [°C]Pressure [bar]
C3H6 / C3H8 / C2H4-25.001.00
CH3OH / H2O / C6H6N2 (1 bar)50.001.00



Color indicator

For visual display of loading with steam silica gel is dyed with an indicator.

Frequently pH indicators are used. In the adsorption of water on the surface of the silica gel, the pH value changes.

This change causes a change in color of the indicator. Further, iron and the heavy metal salts of cobalt (II) chloride are used.

 

 

Color indicatorColor indicatorHesitation
Orange -> GreenpH-indicatorharmless
Orange -> ColorlesspH-indicatorcritical
Iron saltharmless
Blue -> PinkHeavy metalcritical
Orange -> RedpH-indicatorharmless
Blue -> RedpH-indicatorharmless
Colorless-harmless

 

Color indicator



Grain sizes

The size of the grain has a strong influence on the adsorption. The larger the particle diameter is...

  • the longer adsorption times in the perfused adsorber
  • the smaller the pressure loss when flowing through the adsorbents bedding
  • the greater the void fraction of adsorbents bedding
  • the greater the effect of the wall effect in the adsorbents
  • the greater the hydraulic diameter of the adsorbents bedding
  • the more uneven the radial velocity profile in the adsorber

For perfused bulks od silica gel balls are recommended with a diameter of 3-5 mm.



Regeneration of silica gels

In practice, the most common method used to regenerate silica gel is to increase the temperature. In the desorption of water vapor from silica gel, the temperature must be above 100°C. Recommended for regeneration are temperatures between 150°C to 175°C. However, bearing in mind that one is damaged in the silica gel applied color indicator at these temperatures. Therefore, a regeneration temperature is specified from 121°C for silica gel with color indicator and should not exceed 140°C.

Silica gel Regeneration



Aging of silica gels

If fine-pore, colorless silica gel is regenerated at a temperature of 150°C, the equilibrium concentration decreased after 100 cycles by about 20% and the half value diffusion coefficient by 32%. Thereafter, the equilibrium loading and the diffusion coefficient reaches a limit value, which is up to 500 cycles no longer significantly below.



Adsorption of further substances

Besides water, also other substances can be adsorbed by silica gels. To ensure the optimal choice of the adsorbents the substances and their diffusion coefficient should be known facing silica gel.



Color indicator

For visual display of loading with steam silica gel is dyed with an indicator.

Frequently pH indicators are used. In the adsorption of water on the surface of the silica gel, the pH value changes.

This change causes a change in color of the indicator. Further, iron and the heavy metal salts of cobalt (II) chloride are used.

 

Color indicator



Grain sizes

The size of the grain has a strong influence on the adsorption. The larger the particle diameter is...

  • the longer adsorption times in the perfused adsorber
  • the smaller the pressure loss when flowing through the adsorbents bedding
  • the greater the void fraction of adsorbents bedding
  • the greater the effect of the wall effect in the adsorbents
  • the greater the hydraulic diameter of the adsorbents bedding
  • the more uneven the radial velocity profile in the adsorber

For perfused bulks od silica gel balls are recommended with a diameter of 3-5 mm.


Assortment

Standard

  • 2,0 l plasic bottle
  • 4,0 l plastic canister
  • 30,0 l plastic barrel
  • 60,0 l plastic barrel


Optional

  • 1,0 kg bag
  • 25,0 kg bag
  • Aluminium composite bag
  • Other types of packaging on request


Delivery

  • Standard silica gels are available up to 1.000 kg from stock.
  • More varieties and lager quantities available on request.

Silica gel varieties

Silica gelsColorlessOrange-GreenOrange-ColorlessBlue-PinkBlue-RedOrange-RedWide-pore
silica gel
Grain sizes3-5 mm3-5 mm3-5 mm3-5 mm3-5 mm3-5 mm1,4-2,8 mm
0,5-1 mm
1-3 mm

 


Standard

  • 2,0 l plasic bottle
  • 4,0 l plastic canister
  • 30,0 l plastic barrel
  • 60,0 l plastic barrel


Optional

  • 1,0 kg bag
  • 25,0 kg bag
  • Aluminium composite bag
  • Other types of packaging on request


Delivery

  • Standard silica gels are available up to 1.000 kg from stock.
  • More varieties and lager quantities available on request.

Silica gel varieties

WE'RE HERE FOR YOU

You will receive an offer on the same day
A personal appointment will be realized within a week
You will receive a standard GIEBEL Adsorber within a week.

GIEBEL FilTec GmbH
Carl-Zeiss-Str. 5 / 74626 Bretzfeld-Schwabbach / Germany
Tel. +49 (0) 7946 944401 - 0 / info@giebel-adsorber.de