Civil Engineering Reference
In-Depth Information
Approximate Slurry Flow, gpm
0
5
10
15
20
25
70
60
Maximum
Carbon-Water
Ratio
3 lb Carbon/gal Water
50
40
Operating
Region
Minimum
Velocity
30
Recommended
Carbon-Water
Ratio
1 lb Carbon/gal Water
20
10
Maximum
Recommended
Velocity
2
4
6
8
10
Linear Velocity, ft/sec
Fig. 17-10.
Carbon delivery rate (1-inch pipe) (Courtesy of Calgon Carbon Corporation)
capacity relationship with the pump curves. See Krasner et al.
29
for a detailed discus-
sion on carbon slurry hydraulics.
Pilot plant tests indicate that after an initial higher rate, the rate of attrition for
activated carbon in moving water slurries is approximately constant for any given
velocity, reaching an approximate value of 0.17 percent fines generated per exhaustion-
regeneration cycle. This deterioration of the carbon with cyclic operation has been
reported to be independent of the velocity of the slurry, within the recommended range
of 3.5 to 5 ft / sec (1.0 to 1.5 m / s). Loss of carbon by attrition in hydraulic handling
apparently is not related to the type of pump used (diaphragm or centrifugal).
Carbon slurries can be transported by using water- or air-pressure centrifugal
pumps, eductors, or diaphragm pumps. The choice of motive power is a combination
of owner preference, turndown capabilities, economics, and differential head require-
ments.
CARBON ADSORPTION ENHANCEMENT WITH OZONE
Depending on water quality, ozone pretreatment ahead of GAC adsorption may in-
crease GAC service life by 5 to 100 percent.
30
Under most circumstances, a 10 to 20
percent extension of carbon service life can be expected. Preozonation tests should be
conducted during GAC pilot plant operations.
