Table of Contents
Vapor-liquid equilibrium (VLE) is a fundamental concept in chemical process engineering. It describes the balance between vapor and liquid phases of a substance at a given temperature and pressure. Understanding VLE is essential for designing separation processes such as distillation and extraction.
Basics of Vapor-Liquid Equilibrium
VLE occurs when a liquid and its vapor coexist at equilibrium. The composition of each phase remains constant over time, provided the system is closed. The key parameters include temperature, pressure, and the composition of each phase.
Calculating Vapor-Liquid Equilibrium
Calculations of VLE typically involve equilibrium data such as vapor-liquid equilibrium diagrams and activity coefficients. Raoult’s law and Dalton’s law are often used for ideal systems, while activity coefficient models are applied for non-ideal mixtures.
Methods and Tools
Common methods for VLE calculations include the use of flash calculations and equilibrium stage models. Software tools like Aspen Plus and HYSYS facilitate these calculations, providing accurate predictions for process design.
- Vapor pressure data
- Activity coefficient models
- Equilibrium diagrams
- Simulation software