Water Softening - Public Water Systems - page 436

For solution feed of CO 2 , equipment similar (except for materials of construction)
to solution feed chlorinators may be used. Chlorinator capacity is reduced about 25
percent when feeding CO 2 . Approximately 60 gallons of water is required to dissolve
1 pound (0.454 kg) of CO 2 at room temperature and atmospheric pressure. Absorption
efficiency with solution feed of CO 2 approaches 100 percent.

CARBON DIOXIDE PIPING AND DIFFUSION SYSTEMS

Because the gas temperature in recarbonation systems is usually in the 70 to 100 F
(21.1 to 38 C) range, the pressure is about 6 to 8 psi (40 to 55 kPa). And because
CO 2 pipe runs are usually less than 100 feet (30 m), it is convenient to use Table
13-3 to estimate the pipe size required. The pipe sizes obtained from Table 13-3 are,
of course, an approximation. For greater accuracy, or for long lines, the following
modification of the Darcy-Weisbach formula may be used for pressure loss in air
piping:

ƒ LTQ

2

p

(13-22)

38,000 pD

5

where:

delta p pressure drop, psi (kPa)

0.048 D
0.148

0.027

ƒ (Note: usual values for ƒ 0.016-0.049)

Q
L pipe length, feet (m)
T absolute temperature of the gas,

R( F 460)

Q gas flow, cu ft / min (m 3 / min)
p absolute pressure of the gas, psi (kPa) (or line pressure in psi 14.7)
D pipe diameter, inches (cm)

The pressure loss in elbows and tees can be approximated by use of the following
formulas:

TABLE 13-3. Approximate Gas-Carrying Capacity
Pipe Diameter Capacity

Inches cm cu ft / min m 3 / min

1 2.54 45 1.27

2 5.08 250 7.1

3 7.02 685 19.4

4 10.16 1,410 39.9

6 15.24 3,870 109.5