H. Oyaisi, O. Abunumah, P. Ogunlude, E.B. Abunumah, A. Giwa, E. Gobina, R. Prabhu
Royal Cornhill Hospital,
United Kingdom
Keywords: Oxygen, Nitrogen, Separation, Covid-19, Displacement Pressure, Permeation, CO2
Summary:
An analytical model has been developed for producing medical Oxygen devices through the synergetic application of membrane technology, nanotechnology, biotechnology and fluid dynamics. This research is inspired by the medical Oxygen demand and supply challenges faced during the Covid-19 pandemic in medical facilities worldwide. The Covid-19 pandemic brought to the foreground the need for medical oxygen production methods that are accessible, timely deployment, economical and of high medical quality. The extant methods of producing medical Oxygen include Cryogenic Air Separation Unit, Pressure Swing Adsorption and Oxygen Concentrator techniques. However, the method proposed in this research is based on displacement pressure (DP) and can overcome certain demerits, such as energy consumption, in extant methods. Extensive experimental and data mining approaches were applied in the study. Thermally stable ceramic membranes with nano and micro scale pore sizes and other morphological parameters were crafted for the experiments and model. Seven of the eight gases found in ambient Air were experimented with - Nitrogen (N2-78%), Oxygen (O2-21%), Argon (Ar-0.9%), Carbon Dioxide (CO2-0.04%), Methane (CH4-0.0002%), Helium (He-0.000524%), and Hydrogen (H2-0.00005%). The effects of the thermophysical and thermochemical properties of the respective gases on oxygen production were investigated. A total of 1,920 experimental runs were conducted and 19,200 data points were generated. The results show that various membrane and nano parameter settings offered different energy, deliverability, separation and purity opportunities. Different flow regime characterisations such as Knudson, Darcy and Forchheimer also offered different benefits to O2 production. The membranes with nanopore scale are observed to be more effective than micropore scale membranes. Their respective summative separation factors are 2.93 and 2.40 at a feed pressure of 0.20atm. The DP was experimentally determined for each membrane pore scale. For the 15nm membrane, DPs are He (0.158atm), CH4 (0.044atm), N2 (0.046atm), Air (0.022atm), O2 (0.110atm), Ar (0.056atm), and CO2 (0.032atm). Given a membrane morphological setting, these are the minimum pressure that must be overcome for the respective gases to permeate the pores. The data was used to develop a two-stage analytical model. Oxygen has the highest DP, save for He. This indicates that N2, with its relatively low DP (0.046atm) and higher fractional composition (78%) in Air, can be separated as a permeate while the other gases are collected as retentates. From this study and the morphological setting of our nanoscale membrane, it is noted that injecting Air (feed) in stage-1 into the membrane at a pressure that is 455% of the O2 DP (that is, 0.110atm) could yield 96% purity (fractional composition) of O2 in the retentate gas mixture and pure (100%) N2 in the permeate for a timestamp of one second. Similarly, in Stage-2, feeding the retentate gas mixture from stage-1 into stage-2 at a feed pressure that is 910% of O2 DP yields pure (100%) O2 in the stage-2 permeate while the other gases (Ar, He, CO2, CH4) are collected as retentates. The analytical model developed can also be applied to other separation process equipment in the chemical, petroleum and pharmaceutical industries.