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Mechanical Design and Operation of Alkanolamine Plants 253

150°F. Below 120°F the amine solution viscosity may lead to a high pressure drop across the
carbon bed; at temperatures above 150°F the adsorptive capacity of the carbon is reduced.
8 x 30 Mesh High-DensityActivated Carbon Filter

Most activated carbon filters use a coal-based, 8 x 30 mesh activated carbon to treat a 10 to
20% amine solution slipstream. Bed heights are typically 10 feet with a flux of 2 to 4 gpm/ftz
(contact time 15 to 20 minutes). Bright and Lister (1987) recommend that an 8 x 30 mesh
activated carbon filter have a 5 micron mechanical prefilter to remove suspended solids from
the amine solution and to prevent plugging of the activated carbon pores. The activated carbon
fdter should be followed by a 10 micron afterfilter to remove carbon fines which might exit the
carbon filter. Many 8 x 30 mesh commercial activated carbon filters are designed more conser-
vatively. For example, Keaton and Bourke (1983) review the design of an activated carbon sys-
tem used to filter a 10% lean DEA solution slipstream. The 42 gpm slipstream of 25 wt% DEA
solution is taken from the lean amine pump discharge. The activated carbon filter is a 104
diameter by 1 l-ft carbon steel vessel with a 316 stainless steel liquid collection system contain-
ing 20,000 pounds of Calgon SGL 8 x 30 mesh granular activated carbon. Surface loading is
0.6 gpm of amine per square foot and the carbon contact time is 120 minutes.
Figure 3-27a can be used to estimate the clean bed pressure drop for 8 x 30 mesh activat-
ed carbon. Since the 8 x 30 mesh activated carbon filter has an upstream mechanical filter,

SUPERFICIAL VELOCITY-GPMIFT'
Figure 3-27a. Clean bed pressure drop of ethanolamine solution through Calgon SGL
8 x 30 mesh cahon. (Wgon, 1986)