This problem is based on the answer to the preceding problem. So please use N = 6 + Reboiler and Nf = 3 from the bottom

as answers to the preceding problem.

Y9. Ponchon-Savarit (Prob. 13-3 in Luyben, Chemical Process Analysis) The column of the preceding problem was designed 20 years ago and has been operating ever since. Energy costs have risen, and it is now desired to reduce operating costs. One suggestion is to heat the feed to 200F using waste heat, thus, perhaps, operating at a lower reflux ratio and reducing the reboiler duty. Can this be done? Will we have to change the column feed point? What will be the new reboiler heat duty