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Process Circuit Analysis 87

Subscripts:
First Subscript - stream number
Second Subscript
Ethylene Dichloride -1

Wastewater

Steam

Figure 3.1 Steam stripping of ethylene dichloride from wastewater.

for the stream number and the component being considered. Write the stream
number first, according to Figure 3.1, and the component number second, where 1
indicates ethylene dichloride and 2 water. Thus, y 4,i means that in stream four the
concentration of ethylene dichloride is y 4>1. If we use molar flow rates, y must be
in mole fraction units. A component balance may be written for each component
and for an n component system, n independent component balances may be writ-
ten. In this case, we may write, according to Equation 3.3, for ethylene dichloride
and water

Ys.i m 3 = y 2,i m 2 + y 4il m, (3.4)

Yu m, + y 3, 2 m 3 = y 2, 2 m 2 + y 4, 2 no, (3.5)

Because for stream 1 contains no ethylene dichloride, we can also write

Y 2,i + Y2.2 = 1 (3.6)

Y2,i + Y2,2 = 1 (3.7)
Y4,i + Y4.2 = 1 (3.8)

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