Noninvasive measurements of gas exchange in a three-dimensional fluidized bed using hyperpolarized 129Xe NMR

TL;DR

This paper introduces a non-invasive NMR method using hyperpolarized 129Xe to measure gas exchange in a 3D fluidized bed, providing new insights into phase interactions and validating fluidized bed models.

Contribution

A novel NMR technique for direct, non-invasive measurement of gas exchange in fluidized beds using hyperpolarized 129Xe, with potential for spatial resolution.

Findings

Measured gas exchange rate constants between phases.

Observed three distinct xenon peaks in NMR spectra.

Results agree with existing fluidized bed models.

Abstract

We present a novel NMR technique that provides a non-invasive, direct measurement of gas exchange in a three-dimensional gas-fluidized bed of solid particles. The NMR spectrum of hyperpolarized 129Xe gas in an Al2O3 particle bed displays three resolved peaks corresponding to xenon in bubbles, the interstitial spaces (emulsion), and adsorbed on particles. Modified NMR exchange and saturation-recovery sequences, together with data analysis based on an exchange-coupled set of Bloch equations, yield gas exchange rate constants between the emulsion and adsorbed phases, and between the bubble and emulsion phases. The results are in approximate agreement previously unverified predictions from well-known models of fluidized bed behavior. Incorporation of NMR imaging methodologies would straightforwardly allow similar measurements on a spatially-resolved basis.