CO2 absorption enhancement by water-based nanofluids of CNT and SiO2 using hollow-fiber membrane contactor

• Published in: Separation and purification technology 2019-02, Vol.210, p.920-926
• Main Authors: Rezakazemi, Mashallah, Darabi, Mohammad, Soroush, Ebrahim, Mesbah, Mohammad
• Format: Article
• Language: English
• Subjects: CFD; CO2 absorption enhancement; Hollow fiber; Mass transfer; Membrane contactor; Nanofluid
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2018.09.005

•CO2 capture using nanofluids in hollow fiber membrane energy system were explored.•CFD model was developed to explore effect of CNT and SiO2 nanoparticles.•Grazing effect and Brownian motion were applied to investigate mass-transfer improvement.•Improvement mechanisms of CO2 absorption by nanofluids were explored. In this study, CO2 absorption enhancement using nanofluids in a gas-liquid hollow fiber membrane contactor (HFMC) was conducted through a 2D mathematical model. The model was developed by considering molecular diffusion in radial and axial directions as well as non-wetting condition. CO2 absorption was conducted from a gas mixture, containing CO2 and air, which flows in the shell. Also, absorbents which are containing CNT and SiO2 nanoparticles flow in tube side counter-currently. The effect of nanoparticles was considered by taking two prominent mechanisms for mass transfer enhancement in nanofluids; i.e., Brownian motion and Grazing effect. Model predictions compared with experimental results and excellent agreement was found. The simulation results indicated that introducing 0.05 wt.% SiO2 nanoparticles enhanced absorption rate up to 16%. CNT because of high adsorption capacity and hydrophobicity showed much better performance than the SiO2 nanoparticles, so that introducing 0.05 wt.% CNT enhanced the absorption rate up to 34%. For better performance of nanoparticle in the absorbent, there is an optimal loading which is 0.03 and 0.04 wt.% for SiO2 and CNT, respectively.