Development of an automated dual piston pressure swing adsorption system

Abstract

Thousands of different adsorbate materials are developed every day. However, current instruments are not able keep up with testing the materials and faster methods needed. This thesis described the development and automation of a, a novel DP-PSA (Dual Piston-Pressure Swing Adsorption) setup. It is a unique system suited to test novel materials for the efficient separation of binary mixtures in a single adsorption column. The DP-PSA is a closed system where pistons moving in cylinders at each end of the adsorbent column induce the cycling of fluid flows and pressure variations in the fixed bed. The equipment can be assimilated to a distillation column with total reflux and allows the measurement of the maximum separation achievable with the material. Pressure transducers to measure absolute pressure variations and pressure drops are placed at the top and at the bottom of the column, respectively. Four thermocouples inside the column are placed in two pairs at different positions along the column. In each pair one thermocouple is inserted into a zeolite pellet while the other is exposed to the gas phase. The apparatus is automated by LabVIEW code and controlled by a real time computer, Compact RIO. Thus, the automated DP-PSA is able to run a series of experiment without direct supervision. The development of the DP-PSA includes experiment design, measurement of leak rates, dead volumes for packed and unpacked column, friction, pressure drop across the adsorbing column and temperature gradient along the column. The system with thermocouples can be run in two modes: single pellet experiments and full packed column runs. Single pellet experiments, where only the pellets connected to the thermocouples are inside the system, were carried out to study the heat transfer between the zeolite pellets and gases (He, N2, CO2, and mixtures of N2 and CO2). The other mode is that the adsorbing column is packed fully with zeolite pellets. Experiments with pure gases and mixtures of N2 and CO2 were run with different configurations of the system: cycle time; phase angle; stroke length ratio and initial temperature. The system was tested using commercial 13X pellets. The measured signals were compared based on the amplitude and time shifts and numerical simulations were used to compare the predictions of a dynamic model of the system with the experimental results. The DP-PSA has been shown to generate a very large set of experimental results, with varying conditions which allows to determine physical parameters of dynamic models. This is achieved without consuming gases given that several experiments are automatically carried out in a closed system.

Thousands of different adsorbate materials are developed every day. However, current instruments are not able keep up with testing the materials and faster methods needed. This thesis described the development and automation of a, a novel DP-PSA (Dual Piston-Pressure Swing Adsorption) setup. It is a unique system suited to test novel materials for the efficient separation of binary mixtures in a single adsorption column. The DP-PSA is a closed system where pistons moving in cylinders at each end of the adsorbent column induce the cycling of fluid flows and pressure variations in the fixed bed. The equipment can be assimilated to a distillation column with total reflux and allows the measurement of the maximum separation achievable with the material. Pressure transducers to measure absolute pressure variations and pressure drops are placed at the top and at the bottom of the column, respectively. Four thermocouples inside the column are placed in two pairs at different positions along the column. In each pair one thermocouple is inserted into a zeolite pellet while the other is exposed to the gas phase. The apparatus is automated by LabVIEW code and controlled by a real time computer, Compact RIO. Thus, the automated DP-PSA is able to run a series of experiment without direct supervision.

The development of the DP-PSA includes experiment design, measurement of leak rates, dead volumes for packed and unpacked column, friction, pressure drop across the adsorbing column and temperature gradient along the column. The system with thermocouples can be run in two modes: single pellet experiments and full packed column runs. Single pellet experiments, where only the pellets connected to the thermocouples are inside the system, were carried out to study the heat transfer between the zeolite pellets and gases (He, N₂, CO₂, and mixtures of N₂ and CO₂). The other mode is that the adsorbing column is packed fully with zeolite pellets. Experiments with pure gases and mixtures of N₂ and CO₂ were run with different configurations of the system: cycle time; phase angle; stroke length ratio and initial temperature. The system was tested using commercial 13X pellets. The measured signals were compared based on the amplitude and time shifts and numerical simulations were used to compare the predictions of a dynamic model of the system with the experimental results. The DP-PSA has been shown to generate a very large set of experimental results, with varying conditions which allows to determine physical parameters of dynamic models. This is achieved without consuming gases given that several experiments are automatically carried out in a closed system.