(476c) Hybrid Membrane-Cryogenic Distillation Processes for Argon Production from Air

Nowadays simultaneous production of oxygen, nitrogen and argon from air on a commercial scale is performed mainly by cryogenic distillation¹. Although this technology is relatively mature and can deliver high purity products at high capacities, it is highly energy and capital intensive. In particular, separation of oxygen and argon represents a significant challenge due to their similar volatilities.

In recent years, demand for high purity argon has grown, in tandem with increased demand for oxygen². Current distillation technologies can produce extremely high purity argon but many distillation stages are required and energy demand of the separation is high³. Consequently, there is a need for development of cost-efficient processes to produce argon from air.

In this work, a novel hybrid process is proposed wherein a membrane unit is coupled with distillation unit to create a novel, energy-efficient process for argon production. A range of membranes at various levels of technological maturity is considered.

Appropriate models are developed to evaluate the performance of these novel processes. Air separation units are modelled in Aspen Plus. Permeation of gas molecules through membranes is described by solution diffusion mechanism. Countercurrent and crossflow membrane models are implemented in Aspen Plus as â??user-defined unitsâ??. The models are validated against published experimental data. An optimisation based solution technique is applied to determine optimum process conditions of the hybrid flowsheet.

A systematic methodology is under development to design, evaluate and optimise alternative hybrid membrane-cryogenic distillation processes for air separation. The performance of hybrid processes will be evaluated in terms of the power demand of the main air compressor and the membrane area required in order to identify the most promising design options offering capital and energy savings compared to conventional cryogenic air separation processes.

 

¹ Castle, W. 2002. Air separation and liquefaction: recent developments and prospects for the beginning of the new millennium. International Journal of Refrigeration, 25, 158-172.

² Transparency Market Research. 2014. Noble Gases Market (Helium, Xenon, Neon, Krypton, and Argon) - Global Industry Analysis, Size, Share, Growth, Trends and Forecast, 2013 - 2019 [Online].

³ Agrawal, R., Auvil, S., Choe, J. and Woodward, D. 1990. Membrane/cryogenic hybrid scheme for argon production from air. Gas Separation & Purification, 4, 75-80.