Civil Engineering Reference
In-Depth Information
Carbon Transport Facilities
Once carbon is introduced into the adsorption-
regeneration system, GAC is usually transported hydraulically in slurry form. Air or
pneumatic transport of carbon is sometimes used for bulk handling of makeup carbon.
Handling characteristics have been reported for water slurries of 17
40 mesh
granular carbon in a 2-in. (50-mm) pipeline. The data indicate that a maximum of 3
lb carbon / gal (0.36 kg carbon / L) of water could be transported hydraulically but that
it is better to use a ratio of 1 lb carbon / gal (0.12 kg carbon / L). The velocity necessary
to prevent settling of carbon is a function of pipe diameter, granule size, and liquid
and particle density. The minimum linear velocity to prevent carbon settling was found
to be 3.0 ft / sec (0.9 m / s). It is recommended that a velocity of 3.5 to 5.0 ft / sec (1.0
to 1.5 m / s) be used for design. Velocities of over 10 ft / sec (3 m / s) are undesirable
because of carbon abrasion and pipe erosion. Carbon delivery rates are a function
of pipe diameter, slurry concentration, and linear velocity. Data are shown in Figure
17-9 and 17-10 for a 2-in. (50-mm) pipe and a 1-in. (25-mm) pipe, respectively. The
shaded area in Figures 17-9 and 17-10 show the operating region that meets the design
criteria. One-inch (25-mm) pipes are able to provide GAC transfer rates of 5 to 16 lb/
min. Two-inch (150-mm) pipes are used for GAC transfer rates above 30 lb / min.
Pressure drop data for various slurry concentrations and velocities in 2-in. (50-mm)
pipe are shown in Figure 17-11. This figure shows that the headloss increases rapidly
as the slurry concentration increases. The designer must balance the headloss and
Approximate Slurry Flow, gpm
10
20
30
40
50
60
70
80
90
100
300
280
260
240
220
200
180
Maximum
Carbon-Water
Ratio
3 lb Carbon/gal Water
160
140
120
Operating
Region
Minimum
Velocity
Recommended
Carbon-Water
Ratio
1 lb Carbon/gal Water
100
80
60
40
20
Maximum
Recommended
Velocity
0
2
4
6
8
10
Linear Velocity, ft/sec
Fig. 17-9.
Carbon delivery rate (2-inch pipe) (Courtesy of Calgon Carbon Corporation)
