Emulsion droplet sizing using low-field NMR with chemical shift resolution and the block gradient pulse method

Lingwood, I.A.; Chandrasekera, Thusara C.; Kolz, J.; Fridjonsson, Einar O.; Johns, Michael L.

doi:10.1016/j.jmr.2011.11.020

Cited by 52 publications

(43 citation statements)

References 40 publications

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“…(2) exists in which it is assumed that the duration of the applied magnetic field gradient, d, is equal to zero; since the use of the EFNMR requires the use of a comparatively very long value of d (up to 40 ms) we do not consider this method further in this work. More recently [20], we demonstrated the use of the block gradient pulse (bgp) approximation method to describe restricted diffusion inside spherical droplets (emulsion droplet sizing), with significantly improved accuracy compared to the assumption of a Gaussian phase distribution or an infinitely short d over all experimental parameter space considered. The bgp method is based on the generalised gradient waveform set of methods [21][22][23], in which an eigenfunction expansion is used to solve the Bloch-Torrey equation in the presence of a piecewise-constant gradient waveform [24].…”

Section: Pulsed Field Gradient Emulsion Droplet Sizingmentioning

confidence: 99%

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Determination of mean droplet sizes of water-in-oil emulsions using an Earth’s field NMR instrument

Fridjonsson

Flux

Johns

2012

Journal of Magnetic Resonance

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Section: Pulsed Field Gradient Emulsion Droplet Sizingmentioning

confidence: 99%

“…Details regarding the derivation can be sourced from Grebenkov [25] and our implementation for emulsion droplet sizing, as is employed in the work presented here, is detailed in Ref. [20].…”

Section: Pulsed Field Gradient Emulsion Droplet Sizingmentioning

confidence: 99%

Determination of mean droplet sizes of water-in-oil emulsions using an Earth’s field NMR instrument

Fridjonsson

Flux

Johns

2012

Journal of Magnetic Resonance

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“…While it is common practice to avoid this regularization step when using benchtop NMR apparatuses by assuming a priori a log-normal distribution, this is not universally appropriate. In this work, the emulsion DSDs are extracted using Tikhonov regularization with general cross-validation (GCV) to choose the regularization parameter (see the studies by Hollingsworth and Johns 26 and Lingwood et al 39 for further details).…”

Section: ■ Introductionmentioning

confidence: 99%

Optimized Droplet Sizing of Water-in-Crude Oil Emulsions Using Nuclear Magnetic Resonance

et al. 2014

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Water-in-crude oil emulsions are an increasing problem during production. Essential to any emulsion breaking method is an ability to accurately measure droplet size distributions; this is rendered extremely difficult given that the samples are both concentrated and opaque. Here, we systematically consider the use of a standard, low-field benchtop nuclear magnetic resonance (NMR) apparatus to accurately measure the droplet size distributions. Such measurements are challenging because the NMR signal from the oil phase erroneously contributes to the measured water droplet size distribution. Conventionally, the oilphase signal is nulled-out based on differences in the NMR T 1 relaxation parameter between water and oil. However, in the case of crude oil, the oil presents a broad T 1 distribution, rendering this approach infeasible. On the basis of this oil T 1 distribution, we present an optimization routine that adjusts various NMR measurement timing parameters [observation time (Δ) and inversion time (T inv )] to effectively eliminate this erroneous crude oil contribution. An implementation of this optimization routine was validated against measurements performed using unambiguous chemical-shift selection of the water (droplet) signal, as would conventionally be provided by high-field superconducting NMR spectrometers. We finally demonstrate successful droplet sizing of a range of water-in-crude oil emulsions.

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“…An alternative derivation is the short gradient pulse (SGP) model which assumes the gradient pulse duration is negligible, d = 0, and hence that the diffusion that occurs during this period can be neglected. To overcome some of the drawbacks of the GPD and SGP approaches [36][37][38], Lingwood et al [39] im-…”

Section: Nuclear Magnetic Resonancementioning

confidence: 99%

Explosive Emulsion Characterisation using Nuclear Magnetic Resonance

Hayward

Ling

Johns

2019

Propellants Explo Pyrotec

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Explosive emulsions are frequently employed in mining operations as they offer a comparatively robust, safe and effective product. These are typically formulated as concentrated ammonium nitrate solutions dispersed in an oil phase in the form of a highly concentrated water‐in‐oil emulsion. Being highly concentrated, determining the droplet size distribution (which is critical to assessing long‐term emulsion stability and explosive effectiveness) of these emulsions is challenging. Here we demonstrate that this is readily achieved using bench‐top Nuclear Magnetic resonance (NMR) Pulsed Field Gradient (PFG) techniques. The initial mean droplet size is shown to decrease with an increase in the concentration of ammonium nitrate or emulsifier or when inert salt was added to the composition, it was found to increase as the concentration of the aqueous (oxidiser) phase was increased. The emulsion droplet size distributions were observed to remain constant for a 3‐month period over the composition range explored.

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Emulsion droplet sizing using low-field NMR with chemical shift resolution and the block gradient pulse method

Cited by 52 publications

References 40 publications

Determination of mean droplet sizes of water-in-oil emulsions using an Earth’s field NMR instrument

Determination of mean droplet sizes of water-in-oil emulsions using an Earth’s field NMR instrument

Optimized Droplet Sizing of Water-in-Crude Oil Emulsions Using Nuclear Magnetic Resonance

Explosive Emulsion Characterisation using Nuclear Magnetic Resonance

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