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Gas-solid instrumentation development in the Sibley School

An important prerequisite for conducting experiments in gas-solid systems is to develop instruments capable of recording the principal variables in these systems. In this context, we have designed new diagnostic techniques since 1985. Notably, we created dielectric measurements of solid volume fraction for a variety of systems (industrial plants, snow pack, sand dunes, fluid beds) and refined optical fiber techniques.

For a synoptic view of instrumentation in gas-solid flows, see Louge, M.: “Experimental Techniques,” ch. 9 in Circulating Fluidized Beds, J. Grace, T. Knowlton and A. Avidan, eds, Blackie Academic & Professional (1997), pp. 312-368.

A fruitful collaboration with Merck has led to the development of instrumentation, such as the level sensor described in the article below, which allow feedback control of continuous pharmaceutical manufacturing.

Michel Y. Louge, Jasdeep Mandur, William Blincoe, Anthony Tantuccio, and Robert F. Meyer: “Non-invasive, continuous, quantitative detection of powder level and mass holdup in a metal feed tube,” Powder Technology 382, 467-477 (2021).

In this article, we describe a quantitative, non-invasive capacitance detector providing a rapid signal that varies continuously with powder level and/or mass holdup in the metal feed tube of a tablet press. We outline the principle of its processing electronics, provide an algorithm for the accurate interpretation of its signals, pose general design guidelines for embedding the instrument in the tube, and show how the detector can be paired with another non-invasive reference probe to operate with varying powder blend and moisture. We illustrate a control strategy that keeps powder level constant with a process example.


Our main publications on this subject include:

M. Louge, M. Tuccio, E. Lander and P. Connors: “Capacitance Measurements of the Volume Fraction and Velocity of Dielectric Solids Near a Grounded Wall,” Rev. Sci. Instrum. 67 (5), 1869-77 (1996).

In this paper, we describe a capacitance technique to measure solid volume fractions in vessels, such as industrial fluid bed reactors, where the wall is a metal held at a reference voltage. By cross-correlating signals from two adjacent probes, we also use the technique to record suspension velocity. This work is the object of US patents 5459406 and 5546006, which are licensed to Capacitec, Inc.
An excerpt of Louge, et al (1996) is available here.

A. Elizabeth Griffith, M.Y. Louge and Jamaludin Mohd. Yusof: “Simultaneous, Non-invasive Measurements of Convective Heat Transfer and Solid Volume Fraction at the Wall of an Entrained Gas-Solid Suspension,” Rev. Sci. Instrum. 71, 2922-2927 (2000).

In this paper, we describe a constant-temperature heat flux probe fitted within the central grounded surface of a capacitance probe. This allowed us to conduct simultaneous measurements of solid volume fraction and heat transfer coefficient at the wall of vessel holding a gas-solid suspension.
An excerpt of Griffith, Louge and Mohd. Yusof (2000) is available here.

Louge, M.Y., Iyer, S.A., Giannelis, E.P., Lischer, D.J. and Chang, H.: “Optical Fiber Measurements of Particle Velocity using Laser-Induced-Phosphorescence,” Applied Optics 30, 1976-81 (1991).

In this paper, we demonstrate a method to measure the velocity of phosphorescent tracers in a gas-solid suspension.
An excerpt of Louge, et al (1991) is available here.

Lischer, D.J. and Louge, M.: “Optical fiber measurements of particle concentration in dense suspensions: calibration and simulation,”  Applied Optics 31, 5106-5113 (1992).

In this paper, we simulate the response of an optical fiber probe measuring solid volume fractions in a fluid-solid suspension using a Monte-Carlo technique launching photons at random consistent with fiber characteristics and recording the fraction returning to the probe. We also generalized this analysis to other kinds of optical fibers, see Louge (1994). These zipped files contain the FORTRAN simulation programs, which are thoroughly commented. Other zipped files contain MS Word transparencies of a presentation on gas-solid instrumentation, and another on optical fiber measurements of solid volume fraction.
An excerpt of Lischer and Louge (1992) is available here.

Louge M. and Opie M.: “Measurements of the Effective Dielectric Permittivity of Suspensions,” Powder Tech. 62, 85-94 (1990).

In this paper, we describe a technique to evaluate the effective dielectric properties of a suspension of powders, and we review homogenization theories and models.
An excerpt of Louge and Opie (1990) is available here.

Acree Riley, C. and Louge, M.Y.: “Quantitative Capacitive Measurements of Voidage in Dense Gas-Solid Flows,” Particulate Science & Tech. 7 51:59 (1989).

In this paper, we outline the capacitance technique and its use in a fluid bed. Since this 1989 publication, we have applied the technique in circulating fluidized beds, a coal burning powerplant, snow packs and avalanches, and sand dunes; we have also coupled it to a small flux meter, and used it to calibrate optical fiber probes. We offer a short tutorial on the use of capacitance probe with pure dielectric solids.