Optimal rectification column, reboiler vessel, connection pipe selection and optimal control of batch distillation considering hydraulic limitations

Abstract

In this article the optimal selection of the reboiler vessels, rectification columns and connection pipes with regard to reboiler swelling, and tray and pipe flooding is investigated. Since the reboilers are constrained by liquid swelling, while pipes and columns are constrained by flooding it is important to pair the equipment so that the vapor rate limitations are as close as possible, thus ensuring maximal equipment capacity usage. Calculations at 1 and 0.25 bar pressure are performed for the standardized 1.6, 2.5, 4 and 6.3 m 3 reboiler vessels [Rührbehälter Basler Norm, N 253, 1977] and sieve tray rectification columns with nominal diameters ranging from 0.2 up to 0.6 m. The dynamic operation of the batch distillation process having the vapor load and reflux ratio as input profiles is evaluated by formulating and solving an optimal control problem constrained by the hydraulic limitations. The open-loop optimization problem is solved using a dedicated Matlab tool – OptCon – which implements the multiple shooting strategy and the large-scale non-linear programming problem is handled by the HQP engine.