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210 Lawrence K. Wang et al.

Table 1
Constants for Use in Determining Height of a Gas Film Transfer Unit
Range of
3,600 G L''
area
2
2
Packing b c d (lb/h-ft ) (lb/h-ft )
Raschig rings
0.375 in. 2.32 0.45 0.47 200–500 500–1,500
1 in. 7.00 0.39 0.58 200–800 400–500
6.41 0.32 0.51 200–60O 500–4,500
1.5 in. 17.30 0.38 0.66 200–700 500–1,500
2.58 0.38 0.40 200–700 1,500–4,500
2 in. 3.82 0.41 0.45 200–800 500–4,500
Bert saddles
0.5 in. 32.40 0.30 0.74 200–700 500–1,500
0.81 0.30 0.24 200–700 1,500–4,500
1 in. 1.97 0.36 0.40 200–800 400–4,500
1.5 in. 5.05 0.32 0.45 200–1,000 400–4,500
3-in Partition rings 650 0.58 1.06 150–900 3,000–10,000
Spiral rings
(stacked staggered)
3-in.Single spiral 2.38 0.35 0.29 130–700 3,000–10,000
3-in. Triple spiral 15.60 0.38 0.60 200–1,000 500–3,000
Drip-point grids
No. 6146 3.91 0.37 0.39 130–1,000 3,000–6,500
No. 6295 4.56 0.17 0.27 100–1,000 2,000–11,500
Source: ref. 11.

Values of Sc and Sc for several pollutants are given in the literature (3,4). In this
G L
example, the effect of temperature on Sc is ignored. L'' is determined as the result of
L'' = L/A (18)
column
Now, the total tower height, Ht using Ht determined in Eq. (12) is determined:
total column
Ht = Ht + 2 + (0.25 D ) (19)
total column column
3
The actual cost of packing is based on the volume of packing, V (ft ), needed to
packing
fill the tower:
2
V = (π/4) (D ) (Ht ) (20)
packing column column
2
V = 0.785 (D ) (Ht ) (20a)
packing column column
3
The packing cost equals volume packing, V , times the cost of packing ($/ft of
packing
packing). Note that now that the tower has been sized, if the tower design calls for a
fractional foot diameter (i.e., 4.15 ft), the calculations must be repeated until an
approximate 0.5 ft tower diameter is reached (i.e., 4.5 ft) or more preferably a whole
foot diameter is reached (i.e., 4.0 ft). This is so because tower suppliers will quote a
project based on their standard size of manufacture.