A highly-efficient hybrid technique-Membrane-assisted gas absorption for ammonia recovery after the Haber-Bosch process

The present study deals with the first complex experimental evaluation of the unique hybrid technique - membrane-assisted gas absorption for NH3 recovery applications. In order to determine the influence of technological parameters and compare different absorbents impact, a special lab-scale test platform was designed and coupled with the specific back-flush-to-vent gas chromatographic technique. The efficiency of ammonia capture was evaluated during the separation of ternary gas mixture consisting of H2, N2 and NH3. The wide range of absorbents and gas separation membranes was screened to determine the potentially efficient combinations of membrane-absorbent systems. As a result, the poly-(vinyltrimethylsilane) (PVTMS) commercially available gas separation membrane covered with deep eutectic solvents (DES) based on ammonium thiocyanate (NH4SCN) combined with glycerol (G), urea (U) and ethylene glycol (EG) was used as a combined system for further evaluation in the NH3 recovery process. It was experimentally defined, that the membrane-assisted gas absorption technique provides efficient recovery of NH3, and its concentration in permeate reach 98.96 vol% in the case of NH4SCN:G. Nevertheless, that DES couldn't provide stable efficiency in contrast with less-viscosity DESes, such as NH4SCN:U and NH4SCN:EG. It was found that these absorbents allow achieving up to 98.42 and 98.7 vol % of NH3 in permeate.

Automated summary

The study evaluated the efficiency of membrane-assisted gas absorption for NH3 recovery applications, finding that the NH4SCN:G combination can reach up to 98.96% NH3 recovery but lacks stable efficiency compared to lower-viscosity deep eutectic solvents like NH4SCN:U and NH4SCN:EG, which can achieve up to 98.42% and 98.7% NH3 recovery, respectively.