Extent of mixing in a two-component batch system measured using MRI

Lee, Y.; McCarthy, Maureen I.; McCarthy, Kathryn

doi:10.1016/s0260-8774(00)00240-5

Cited by 19 publications

(4 citation statements)

References 7 publications

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“…Food materials are excellent systems for MR inspection because of the similarity in their MR characteristics (e.g., relaxation times, low magnetic susceptibility variation) to those of medical subjects. Recent developments include the use of model food systems to demonstrate MR's temperature mapping capabilities (Nott et al, 1999) and a quantitative evaluation of mixing in food-processing operations (Lee et al, 2001). Small spectrometers dedicated to quality control applications in food production are already in use.…”

Section: Process Applicationsmentioning

confidence: 99%

Magnetic resonance: Ongoing and future role in chemical engineering research

Gladden

2003

AIChE Journal

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IntroductionI n 1988, a report by Amundson on behalf of the U.S. National Research Council (Amundson, 1988) identified nuclear magnetic resonance (NMR) spectroscopy as a potentially useful tool for studying catalyst structure and surface chemistry, noting the existence of magnetic resonance imaging (MRI). Fourteen years later, there is a substantial body of evidence to say that magnetic resonance (MR) techniques, far more wide ranging in scope than was originally envisaged, have become integrated into chemical engineering research and are becoming increasingly more popular in this role. This said, the diversity of measurements that can be made and the systems that can be studied are still relatively poorly understood. The opportunities for market penetration are still quite high.From a chemical engineer's perspective, the most important attributes of MR lie in its ability to record 1-D, 2-D and 3-D images with the resolution as high as 5-10 µm, along with spatially resolved maps of transport characteristics (diffusion, dispersion, and flow vector), chemical composition, and variations in the state of matter being probed-all this information being accessed noninvasively and without the need for a tracer. It is the ability to combine different MR measurements within a single experiment (e.g., combining spectroscopy and transport measurements) that makes it so useful in chemical engineering research. To date, most effort has been focused on transferring the imaging and flow visualization measurements originally developed for medical applications across the nonmedical arena. In itself this is not a trivial exercise, since the MR characteristics of nonmedical systems and their requirements on the detail of implementing the MR experiment are quite different from those of medical subjects. Ongoing MR Research in Chemical EngineeringMR is established, but is still relatively underused in three distinct areas of application: characterizing fluid flows; visualizing structure-hydrodynamics relationships in process units; and the integrated use of MR with theoretical modeling and numerical simulation studies. The way in which MR is used in each of these applications can be quite different. Characterizing fluid flowsUntil recently, applications of MR to study flow phenomena have almost entirely been restricted to probing the liquid, as opposed to gas, phase-a direct result of the relatively poor signalto-noise inherent in MR techniques. Nuclear spin densities in the liquid phase are ~10 3 higher than those in the gas, thereby making signal acquisition faster and easier. The potential use of MR in studying fluid flows is huge, because methods can be used to probe molecular displacements over length scales of 10 -6 m up to the physical dimension of the sample. The time scales over which these displacements can be studied in a single measurement is sample-dependent (and depends on the characteristic relaxation time properties of the system), but can lie in the range of milliseconds to seconds. For those who are brave enough to r...

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Section: Process Applicationsmentioning

confidence: 99%

Magnetic resonance: Ongoing and future role in chemical engineering research

Gladden

2003

AIChE Journal

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“…Unlike previous studies with noncolloidal particles [10,11], the spread characteristics did not provide information to adequately describe either the rate or extent of mixing. To exemplify, Table 3 gives CV values for t = 0 (prior to mixing) and at t = 20 min.…”

Section: S(t) = K (7)p(7) Exp(-te /T_ (R)[1 -Exp(-tr/t~mentioning

confidence: 80%

“…By deflnitiom, as these three values approach one another the distribution is described by a normal probability curve. In addition to center characteristics, spread characteristics were also used to evaluate the rate and extent of mixing [9,10]. The standard deviation t S T D ) , a spread characteristic, is given by…”

Section: Methodsmentioning

confidence: 99%

Magnetic resonance imaging as a sensor system for multiphase mixing

et al. 2002

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Mixing in a multicomponent batch system was evaluated by magnetic resonance images. The system was a I0% carbon black powder suspended in aqueous solution. The factors in this study were surfactant type (neodol 23-5 and sodium dodecyl sulfate) at two levels: 1 and 0.1%. Water (0% surfactant) was used as the control. In addition to surfactant type and level, the third factor ,,vas mixing mode: with vortex and without vortex motion. These conditions were disp[ayed at 180 and 60 rpm impeller speed respectively. The type of surfactant did not yield significantly different results in terms of mixing effectiveness. The rate of mixing, as characterized by first-order rate constants, was statistically different asa function of mixing mode, level of surfactant and the interaction of these factors. The extent of mixing, charactefized by a normalized mean signal intensity, was also statistically different as a function of the same factors and interaction. The incorporation of air and subsequent release of air was desc¡ by the volume change of the mixmre asa function of time.

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“…The measurement requires a few minutes to make and provides concentration of fluid as a function of position in the split-and-recombine mixer. This technique is suitable for application to a wide range of mixing problems and geometries [6][7][8][9][10][11]. Limitations to the technique are that a nonmagnetic mixer must be constructed and used in the MRI equipment, and at least one of the materials must provide a sufficient signal for data acquisition.…”

Section: Discussionmentioning

confidence: 99%