Although not absolutely necessary, a spreadsheet using nothing fancier than Goal Seek or Solver will reduce the

Question:

Although not absolutely necessary, a spreadsheet using nothing fancier than Goal Seek or Solver will reduce the calculation burden of this design problem significantly.
Your boss requests a preliminary design for separation of pyridine (B) from furfural (A) in a fractional extraction system. A and B are dissolved in water with water-free wt. frac. of \(\mathrm{z}_{\mathrm{A}}=0.40\) and \(\mathrm{z}_{\mathrm{B}}=0.60\). Design for a base case where \(\mathrm{F}=1.0 \mathrm{~kg} / \mathrm{h}\) feed and \(\mathrm{R}=100 \mathrm{~kg} / \mathrm{h}\) diluent (water). Use toluene as the solvent and operate at \(25^{\circ} \mathrm{C}\). A recovery of at least \(91.0 \%\) and a purity of at least \(95.75 \%\) (on a solventfree basis) of A are required. Maximum number of stages is 10. Data are in Table 13-3.
image text in transcribed Preliminary design procedure: For split between top and bottom, initially use equal split, center-feed equations to estimate \(\mathrm{N}\) and \(\mathrm{N}_{\mathrm{F}}\). Calculate recovery of A and B. Assume the feed splits between E and R in same ratio as \(\mathrm{z}_{\mathrm{A}} / \mathrm{z}_{\mathrm{B}}\). Determine purities of the two products from mass balance calculations Look at your preliminary results. Is there is room for improvement by changing the number of stages?
Tuning preliminary design (assumes that your initial purity was too low): Use equations that do not require equal splits and centered feed. Set \(\mathrm{N}=10\). Because the best feed location is unknown, start by keeping \(\mathrm{N}_{\mathrm{F}} / \mathrm{N}\) from your preliminary calculation constant (but use integer values for \(\mathrm{N}\) and \(\mathrm{N}_{\mathrm{F}}\) ). Determine the recovery of A. Change E/R to return to the specified recovery. Determine the recovery of \(\mathrm{B}\) in the raffinate, and use mass balances to calculate solvent-free purities. If your purity of A on a solvent-free basis is not good enough, you will need to change the recovery of B in the raffinate. First, try adjusting the feed stage (remember to fix the recovery of A to \(91 \%\) by changing \(\mathrm{E} / \mathrm{R})\). Once you have a solution with \(\mathrm{N}=10\) that meets the specifications, record it, and try \(\mathrm{N}=9\). If you cannot get \(\mathrm{N}=10\) stages to meet the requirements, try increasing the number of stages slowly. When you have the lowest number of stages that works and the best value of \(\mathrm{N}_{\mathrm{F}}\), report \(\mathrm{N}, \mathrm{N}_{\mathrm{F}}\), recovery of \(\mathrm{A}\) in extract, recovery of \(\mathrm{B}\) in raffinate, and purity of A in extract on a solvent-free basis.