Analysis of ammonia separation from purge gases in microporous hollow fiber membrane contactors

• Published in: Journal of hazardous materials 2013-09, Vol.260, p.576-584
• Main Authors: Karami, M.R., Keshavarz, P., Khorram, M., Mehdipour, M.
• Format: Article
• Language: English
• Subjects: Absorption; Air Pollutants - chemistry; Ammonia; Ammonia - chemistry; Ammonia separation; Applied sciences; Carbon Dioxide - chemistry; Chemical Industry; Chemical thermodynamics; Chemistry; Contactors; Diffusion; Exact sciences and technology; Fibers; Gases; General and physical chemistry; General. Theory; Hollow fiber; Liquids; Mathematical models; Membrane contactor; Membranes; Membranes, Artificial; Microscopy, Electron, Scanning; Models, Theoretical; Pollution; Polymers - chemistry; Polypropylenes - chemistry; Porosity; Purge gas; Separation; Solubility; Water - chemistry
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2013.06.002

•Ammonia absorption was modeled in a hollow fiber membrane contactor.•Separation process was very effective and with recoveries higher than 99%.•SEM images showed that ammonia caused some micro-cracks on the surfaces of fibers.•Membrane wetting did not have significant effect on the absorption of ammonia.•Gas phase resistance was predominant on the absorption of ammonia. In this study, a mathematical model was developed to analyze the separation of ammonia from the purge gas of ammonia plants using microporous hollow fiber membrane contactors. A numerical procedure was proposed to solve the simultaneous linear and non linear partial differential equations in the liquid, membrane and gas phases for non-wetted or partially wetted conditions. An equation of state was applied in the model instead of Henry's law because of high solubility of ammonia in water. The experimental data of CO2–water system in the literature was used to validate the model due to the lack of data for ammonia–water system. The model showed that the membrane contactor can separate ammonia very effectively and with recoveries higher than 99%. SEM images demonstrated that ammonia caused some micro-cracks on the surfaces of polypropylene fibers, which could be an indication of partial wetting of membrane in long term applications. However, the model results revealed that the membrane wetting did not have significant effect on the absorption of ammonia because of very high solubility of ammonia in water. It was also found that the effect of gas velocity on the absorption flux was much more than the effect of liquid velocity.