Screening alumina is less practical than sieve, because sieve tends to break up an cause the increased pressure drop mentioned. 3-5 years is a typical bed life for alumina (as siad earlier, it depends), so you are getting reasonable life.
As a rule, if one is 'topping off' a bed with fresh...
Two beds (one on adsorption, one on regeneration) will be sufficient and suitable for instrument air drying. There are a number of companies that specialize in building compressed air dryers. Compressor distributors often sell dryers as well, but do not typically design them themselves.
I would...
CL-750 is a patented, promoted alumina by Alcoa (www.adcats.alcoa.com) for chloride removal. A newer version, CL-760, is now available with capacity of 20% by weight (for vapor phase service). Metal oxides cost more.
Iron oxide works well in high temperature service.
Chuck
For drying gas for instrument air use in a remote location (i.e., not electricity, etc.), a pressure swing dryer using activated alumina is recommended. You want to deal with heavy hydrocarbons first, since if these condense on the alumina you will not be able to drive them off. Filtration...
The best guide is this: determine if the product must just avoid condensation; if something akin to Instrument Quality Air (18 deg F dewpoint below the minimum recorded ambient in the area), or if something as low as cryogenic (<0.1 ppmv, or -100 deg F dewpoint ) is required. Cost will increase...
Hydrated alumina Al2O3*3(H2O) can be flash activated, or calcined, by heating. This activation results in Al2O3*1/2H2O. The common desiccant in plant compressed air dryers is Activated Alumina. With various modifications, it is used in a wide variety of adsorption and purification processes. The...
