Measuring the liquid-solid mass transfer coefficient in packed beds using T2-T2 relaxation exchange NMR. (2nd February 2022)

• Record Type: Journal Article
• Authors: Elgersma, Scott V.; Sederman, Andrew J.; Mantle, Michael D.; Gladden, Lynn F.
• Is Part Of: Chemical engineering science. Volume 248:Part B(2022)
• Publication Date: 2022-02-02
• Subjects: Liquid–solid mass transfer -- Packed bed -- Exchange NMR; Chemical engineering -- Periodicals; Génie chimique -- Périodiques; Chemical engineering; Periodicals; Electronic journals; 660
• DOI: 10.1016/j.ces.2021.117229
• Languages: English
• ISSNs: 0009-2509

Abstract

Highlights: Direct measurement of liquid–solid mass transfer coefficient in a packed bed. Novel method for measuring mass transfer coefficient using relaxation exchange NMR. Measurements of mass transfer coefficient made in the range Re = 0–38.6. First direct measurement of mass transfer coefficient in a packed bed at Re = 0. Sh found to reach constant asymptotic value, Sh ~9, at zero flow Re = 0. Abstract: Direct measurement of the liquid–solid mass transfer coefficient in packed beds is achieved using T 2 - T 2 relaxation exchange NMR. This method directly probes molecular exchange between intra- and inter-pellet fluid, rather than requiring a net flux between phases as in conventional methods. Mass transfer coefficients measured using the NMR method are compared with literature values and two widely used correlations. For Reynolds number, Re, less than 0.2, the mass transfer coefficients measured using NMR show excellent agreement with the correlations over the flow conditions for which they were developed. The approach also enables the quantification of mass transfer in the limit of, and at, zero flow. At Re = 0, the Sherwood number in packed beds with voidage of 0.41 determined by NMR is found to approach 9, in good agreement with previously reported results, but significantly greater than that predicted by extrapolating well-known correlations beyond their range of validity to Re = 0.