Bill Gilbert and Mark B. Shiflett | LEEP2 Laboratory 2444
A pressure swing adsorption (PSA) system has been constructed and installed in LEEP2 laboratory 2444 by post-doctoral student Dr. Bill Gilbert and Professor Mark Shiflett. The PSA system is used to study the separation of contaminants such as N2, CO2, CO, and H2S from natural gas (NG). They are currently working with Dr. David Corbin (Senior Scientist, CEBC) to develop new molecular sieves for the kinetic separation of N2 from NG. The system is fully automated and incorporates 4 PSA beds and 2 drying beds as shown in Figures 1 and 2. A Hiden process mass spectrometer with sampling valve provides instantaneous sampling from 16 locations. A LabView® data acquisition program both runs and collects the data from the experiment. A safety interlock system allows continuous unattended operation.
To remove contaminants, the natural gas is fed under pressure through a PSA column containing molecular sieve which can adsorb N2. After the sieve is saturated with N2, the flow is redirected to the next column and the first column is depressurized to desorb the N2 and regenerate the sieve. Figure 3 provides a description of the PSA cycle. In some cases the desorption is slower than the adsorption step, so multiple columns are needed to allow time for complete column regeneration. Development of a molecular sieve to remove N2 from CH4 based on size difference is challenging because they only differ in size by 0.2 Angstroms (N2 is 3.6 Angstroms vs. CH4 is 3.8 Angstroms). However, if a molecular sieve can be developed for this application, it will significantly reduce the cost of separating inert gases such as N2 and possibly He from NG. Current technologies, such as cryogenic plants for N2 removal, are complex and have high capital and operating costs compared to using a PSA system. The PSA technology is also field deployable, modular and can be scaled out to meet the capacity of the gas field. Negotiations are currently underway with a major oil and gas company to sponsor this project.
Figure 1 – Pressure Swing Adsorption System (PSA)
Figure 2 – Pressure Swing Adsorption System Schematic
Figure 3 – Pressure Swing Adsorption System Cycle