# Solve part a of Example 13-2 with a form of the Kremser equation that has an (x^{*})

## Question:

Solve part a of Example 13-2 with a form of the Kremser equation that has an $$x^{*}$$ or $$y^{*}=0$$, but do not use Eqs. (12-31) or (13-19).

Equation (12-31)

Equation (13-19)

Example 13-2

The last step in the recovery of streptomycin from fermentation broth is extractive separation of the active ingredient streptomycin A from streptomycin B (King, 1971). The solvents are an aqueous buffer solution (diluent) and amyl acetate (solvent). The extraction factor for streptomycin A is mAE/R = 1.50 and for B is mBE/R = 0.45 where mi = yi/xi in weight fraction. The feed is in an aqueous solution and F

1. a. The feed is added to the entering raffinate, and a countercurrent cascade (Figure 13-3) with seven stages is used. Find the recovery fraction of A in the outlet solvent stream and of B in the outlet raffinate stream. Note: There is no center feed.

2. b. Based on Eq. (13-18d) for a fractional extraction system, how many stages are required to achieve 91% recovery of A in the extract and 90% recovery of B in the raffinate?

3. c. A seven-stage fractional extraction system has the feed added to the raffinate on stage 2 or stage 3 or stage 4 (Figure 13-5). Determine recovery fractions for each feed stage.

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