CHEN 4501W Lecture Notes - Lecture 31: Pampas
31 Oct 2015
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=> xd --> normally set by product specification --> n - 1 specs. Concept of fractional recoveries fi,d = fraction of i leaving in the distillate stream or from balance eqns. Heuristic: choose fid = 0. 995 - 0. 999 (**) => use (**) and (*) to calculate the remaining specification. Here, xbi can be calculated => all target specifications can be calculated from overall materials balance. Same logic can be applied to heavy components; ex: fractional recovery of a heavy in a bottoms stream as follows. Fractional recoveries are significant optimization variables with respect to separation system. However, for conceptual design, we"ll use the heuristic (**) can never get f = 1that"s thermodynamically impossible. => in this example, given f, xf, specify xd, and calculate xbi using fractional recovery guideline => 2n specifications. => calculate xb, b, d from overall materials balance: choose column pressure (p) First, calculate condensor temperatures at 1 atm condensor just = heat exchanger.
