Silica gel is a spherical bead consisting of 97% silica and 3% alumina. It is available in two types: indicating, a translucent bead impregnated with blue color and non-indicating, which is a brown translucent color.
Since silica gel fractures in the presence of liquid water. It must be protected by a 10% to 15% (by weight) layer of activated alumina as a water buffer on the inlet side of the desiccant bed. Dew points to -40°F and lower may be achieved with silica gel depending on dryer design and operating conditions.
| Non-Indicating | Indicating | |
|---|---|---|
| Color and Form | Translucent brown bead | Translucent blue bead |
| Bulk Density | 49 lbs./cu. ft. | 49 lbs./cu. ft. |
| Surface Area | 3.67 x 106 sq. ft./lb. | 3.67 x 106 sq. ft./lb. |
| Relative Humidity | Non-Indicating | Indicating |
|---|---|---|
| 100% RH | 39% | 37% |
| 90% RH | 36.3% | 34% |
| 60% RH | 33.3% | 29% |
| 10% RH | 6.4% | 4.9% |
| Non-Indicating | Indicating | ||
|---|---|---|---|
| 33-0315 | 5 lb. Pail | 33-0316 | 5 lb. Pail |
| 33-0243 | 25 lb. Pail | 33-0246 | 25 lb. Pail |
| 33-0244 | 50 lb. Bag | 33-0247 | 50 lb. Bag |
| 33-0245 | 330 lb. Steel Drum | 33-0248 | 375 lb. Steel Drum |
High moisture retention capacity under dynamic conditions
Used in some heated type regenerative dryers. Under dynamic conditions, a higher design capacity rating and lower regeneration temperature can be used.
Uniform bead shape
This shape provides lower pressure drop and less abrasion than granular types. Smooth beads also pack uniformly to minimize channeling.
Provides visual check of desiccant condition (indicating type only)
Beads are impregnated with a moisture indicator. The color changes from blue to pink as moisture is adsorbed. Reduced capacity of this type is due to the presence of indicator material in its pores.
