Activated Alumina Drying Grade

Optimised for Compressed Air and Gas Drying

SorbiTech Activated Alumina Drying Grade is the aluminium oxide adsorbent engineered specifically for compressed air dryers and gas dehydration trains. SorbiTech manufactures the sphere through controlled hydration and thermal activation of aluminium hydroxide, with the gamma alumina phase preserved through firing temperature control.

The result is a smooth sphere with a surface area of 320 to 380 m²/g, a crush strength above 130 N per sphere, and an attrition loss below 0.3 percent on ASTM D4058. This grade differs from the AA-201 defluoridation grade in the surface optimisation for thermal cycling rather than for ligand exchange.

Heatless and Heated Desiccant Dryers

In a heatless air dryer the bed cycles every 4 to 10 minutes between adsorption at 7 to 10 barg and depressurised regeneration with purge air. SorbiTech builds the dryer with twin towers, fast acting cycle valves, and a buffer tank sized for the demand profile, with the SorbiTech alumina charge carrying the duty for 5 to 7 years.

In a heated desiccant dryer the cycle is longer, typically 4 to 8 hours, and a heater dries the regeneration purge at 175 to 250 °C. The heated route gives a lower outlet dew point at the cost of additional electricity, and is selected for cryogenic feed prep and other deep drying duties.

Operating Data

• Water capacity: ≥ 20 percent by weight
• Bulk density: 0.75 to 0.82 kg/L
• Crush strength: ≥ 130 N per sphere
• Attrition loss: ≤ 0.3 percent (ASTM D4058)
• Adsorption pressure: 4 to 100 barg
• Regeneration temperature: 175 to 250 °C
• Outlet pressure dew point: minus 20 to minus 70 °C (heated) or minus 20 to minus 40 °C (heatless)

Selecting Against Silica Gel

Silica gel reaches a lower outlet humidity at moderate inlet, but loses capacity sharply once the inlet relative humidity rises and dusts heavily under fast cycling. SorbiTech specifies activated alumina for any duty with a saturated feed, any fast cycling heatless dryer, and any high vibration installation where the silica gel attrition would foul the downstream system.

Forms and Supply

Supplied as 3 to 5 mm and 5 to 8 mm spheres by SorbiTech with a certificate of analysis per batch. Standard packaging is 25 kg drums or 500 kg big bags. Available as standard media for an existing dryer or as the charge in a new SorbiTech dehydration package. SorbiTech specifies the drying grade for the twin tower TSA dehydration unit guard layer and heatless air dryers; see the industrial gas sector and the parent activated alumina family.