Phase equilibrium measurements (VLE)
Measurement of phase equilibria for gas/liquid, vapour/liquid is essential for the design of processes, for example for the absorption of gases such as CO2 and H2S, and for the development of thermodynamic models. When CO2 is removed from natural gas at 50-100 bar pressure, an absorption medium will take up small amounts of hydrocarbons. It is necessary to know exactly how much is being absorbed. This is an example where equilibrium measurements are important. SINTEF has several apparatuses for equilibrium measurements covering a wide range of phase equilibria relevant to gas absorption.
- Vapor-liquid equilibrium measurements at low temperature (LT-VLE).
Under atmospheric pressure, partial pressure of CO2 over homogeneous solutions is measured at 40-80°C. Measuring range for CO2 in the vapor phase is from ppm to 40 mol %.
- Vapor-liqluid equbrium measurements at high temperature (HT-VLE) are used for equilibrium measurements at temperatures up to 150oC up to 6 bar total pressure.
- Equilibrium measurements for muliphase systems (emulsions, slurries) (LabMax®).
Partial pressure of CO2 is measured at low temperatures (25-60°C) under atmospheric pressure as in the LT-VLE. At higher temperatures (80-120 °C), equilibrium data are based on total pressure measurements as in HT-VLE.The apparatus is equipped also with PVM – particle view real-time microscopy, and FBRM for measurements of particle size distribution. The apparatus is suitable for crystallization study.
- High-pressure equilibrium measurements (HP VLE) are used for measurements at temperature and pressure ranges relevant for pre-combustion and natural gas purification.
Here the equilibrium can be measured at temperatures between -10 and 170 oC under pressure up to 195 bara. Liquid and gas phase samples can be taken at equilibrium and analysed online using GC. The setup is designed for CO2, H2S, amines and hydrocarbons.
Heat of absorption measurements
Information on the heat of absorption is directly related to the energy consumption for solvent regeneration in the absorption-desorption cycle. This information is necessary for design and operation of the absorption plant, as well as for thermodynamic modelling.
Heat of absorption can be measured in the reaction calorimeter at temperatures between 30 and 150°C at pressure of up to 20 bar (medium pressure reactor) or 50 bar (high pressure reactor).
Reaction kinetics for CO2 with amines is a key property that forms the basis for optimization of absorption chemicals and design of equipment. Kinetics measurements for gas-liquid reactions are demanding measurements and require special equipment. SINTEF has following equipment for the determination of kinetics:
- String of discs column
- Stirred cell for mass transfer measurements
Physio-chemicals properties – viscosity, density, thermal conductivity.
Knowledge of such properties are required for the establishment of good models for absorber and stripper, for sizing of equipment and for comparison and optimization of the absorption chemicals. SINTEF has a broad portfolio of apparatuses for the accurate measurement of these properties.