Info

Source: U.S. Environmental Protection Agency (EPA), 1987, EAB control cost manual, 3d ed. (Research Triangle Park, N.C. U.S. EPA). Notes: The amount adsorbed is expressed in kg adsorbate/kg adsorbent. The equilibrium partial pressure is expressed in Pa.

Data are for the adsorption on Calgon-type BPL activated carbon (4 X 10 mesh). Data should not be extrapolated outside of the partial pressure ranges shown.

Source: U.S. Environmental Protection Agency (EPA), 1987, EAB control cost manual, 3d ed. (Research Triangle Park, N.C. U.S. EPA). Notes: The amount adsorbed is expressed in kg adsorbate/kg adsorbent. The equilibrium partial pressure is expressed in Pa.

Data are for the adsorption on Calgon-type BPL activated carbon (4 X 10 mesh). Data should not be extrapolated outside of the partial pressure ranges shown.

a) Concentration of pollutant in air stream as a function of bed length a) Concentration of pollutant in air stream as a function of bed length

b) Concentration of pollutant at the exit

Time

FIG. 5.20.11 Adsorption profiles for a single contaminant in an air stream.

Time

FIG. 5.20.11 Adsorption profiles for a single contaminant in an air stream.

Periodic Removal

This system is the simplest to design or build but is not necessarily the most efficient or cost-effective to operate. Essentially, the adsorbate is left in a fixed-bed or fluidized-bed adsorber until the adsorptive capacity of the bed is approached. Then, the adsorbate is removed for destruction, disposal, or regeneration. A new adsorbent is then charged to the system. For systems in which either the adsorbent or adsorbate is hazardous or contact with air is deleterious, this method presents issues requiring expensive solutions. Further, during changeover of the spent adsorbent, the adsorber is not used. Therefore, a minimum of two adsorber units is necessary for any plant in continuous operation.

Continuous Removal

By simultaneously introducing and removing adsorbent, this system achieves continuous operation. This system requires the bed, or the material in the bed, to be in continuous motion. A fixed-bed can rotate so that the fraction of the bed exposed to the feed stream is continuously charged. The spent adsorbent then rotates to a separate zone where the system regenerates it either by flushing with a carrier gas, contact with a reagent, or desorption of the adsorbate by sweeping with a hot gas. Because the adsorbent is necessarily porous, no significant reverse pressure differential exists between the feed and flushing systems.

A solid adsorbent cascading through the feed gas can be continuously removed from the base of the adsorber unit. Regenerated adsorbent can then be recycled to the unit.

Was this article helpful?

0 0

Post a comment