Feed Location

Chapter from the Fractionation Design Guide.

Feed Location Optimization

Feed Condition	Optimal Location	Notes
Subcooled Liquid	Upper-middle of column (70-80% down)	Minimize reboiler duty
Saturated Liquid	Near middle of column (50-60% down)	Standard position
Two-Phase Mixture	Lower section (30-50% down)	Energy balance critical
Superheated Vapor	Lower section (20-40% down)	High sensible heat content

Calculation Method

Kirkbride Equation

log(N_s/N_r) = 0.206 * log{[(x_D/x_B) * (x_B,F/x_D,F)² * (1-x_D)/(1-x_B)]}

Where: N_s = stripping section trays, N_r = rectifying trays, x = mole fractions

Source: Fractionation_Design_Guide_v1.xlsx · sheet “Feed_Location”

© 2026 Inflection Point Engineering, LLC. All rights reserved. The content of this page — including calculation methods, reference data, written analysis, interactive tools, and source code — is the intellectual property of Inflection Point Engineering, LLC and is protected under applicable copyright, trademark, and trade secret laws. Unauthorized reproduction, redistribution, modification, or derivative use in whole or in part is prohibited without prior written consent.

Disclaimer. This material is provided for informational and educational purposes only and does not constitute professional engineering advice. Calculations, reference data, and methodologies are based on published standards and accepted engineering practice but are not a substitute for engineering judgment, site-specific analysis, or review by a licensed Professional Engineer. Inflection Point Engineering, LLC makes no warranties, express or implied, regarding the accuracy, completeness, or fitness for a particular purpose of any content presented here, and shall not be liable for any direct, indirect, incidental, or consequential damages arising from its use. Users assume all risk associated with applying this content to real-world design, operations, or decisions.