Compressed air is dried to prevent condensation and corrosion which can disrupt manufacturing processes and contaminate products. Water is the primary promotor of chemical reactions and physical erosion in compressed air systems. A myriad of external heat regeneration compressed air dryer designs have been devised to provide “commercially dry” air, air having a dew point of -40°F or less, to prevent corrosion. External heat regeneration compressed air dryers use solid adsorbents in granule form to reduce the moisture content of compressed air.
Adsorbents are miraculous microporous granules with a plethora of nanopore cavities throughout which are too small to be seen even with the aid of an optical microscope. Larger pores in the 500 to 2,000 angstrom range, macropores, provide access to the nanopores deep within the adsorbent particle. The molecular forces inside the confined spaces of the nanopores are extraordinary exhibiting unusual effects on molecules entering the cavities. Natural zeolites, adsorbents formed in acidic lakes near prehistoric volcanic eruptions, may have been the birthplace of our first organic life forms. The catalytic nature of the adsorbent surfaces may have promoted chemical reactions resulting in the formation of the initial ammoniates and amino acids.
Recent research at the Oak Ridge National Laboratory has revealed that the adsorption process produces a physical change-of-state. Water molecules were found to dislocate upon adsorption and the hydrogen and oxygen atoms reform in a continuous association inside the nanopores. The adsorbed state is neither gaseous, liquid, or solid, but rather a “quantum tunneling” state discovered by neutron scattering experiments.
Synthetic adsorbents have been developed for industrial services to dry and purify air. These include activated alumina, silica gel, and molecular sieves. Two adsorbent filled vessels are installed in a external heat regeneration compressed air dryer, one for drying the compressed air and one for regeneration. The vessels are switched from on-stream drying service to off-stream regeneration alternately.
This article comes from airbestpractices edit released
