A

Inicrccpi of component balance line on the y-axis

The foregoing equations can be directly applied to a column having several feeds and no side-products. They

A simple column can be regarded as a two-section complex column. Section 1 is the rectifying section, while section 2 is the stripping section. Table 2.6 draws an analogy between the simple and the complex table 2.5 Equations Applying to Each Section "J" of a Complex Fractionator (Continued)

also apply if side-products exist and the following values are used for point k of each side-product:

If heat is removed (e.g., via an intercondenser) or added (e.g., via an interreboiler), the foregoing equations still apply when each source of heat removal or addition is treated as two simultaneous partitions, one from which a stream leaves the column and one to which a stream of the same composition reenters. The two partitions are denoted k' and k, respectively. For heat removal, the stream leaving the column is saturated vapor, and the stream reentering is condensed liquid; the reverse applies for heat addition. The following equations are used:

Fk = AHIHV qk = 1 for heat removal qk - 0 for heat addition (2.42) zk = composition of stream leaving (or reentering) the column

Qk = 0 for heat removal Qk> = 1 for heat addition

Note that there is no net inflow or outflow of material at the point of heat removal or addition; therefore, the "9-line," Eq.(2.39), cannot be used to determine minimum reflux for the section directly above these points.

soubce: From Henry Z. Kister, Chemical Engineering, January 21, 1985, pp. 97-104. Reprinted courtesy of Chemical Engineering.

column equations. It is apparent that the complex column equations are merely a series expansion of the simple column equations. Detailed derivation is elsewhere (19).

Minimum reflux. The minimum reflux in a simple fractionator is calculated by drawing a straight line between the product composition on table 2.6 Analogy Between Simple Column Equations and Complex Column Equations

Simple column table 2.6 Analogy Between Simple Column Equations and Complex Column Equations

Simple column

Equation for

Rectifying section

Stripping section

Complex column

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