Laser capillary spectrophotometry for drop‐size concentration measurements

Abstract

A laser capillary spectrophotometric technique (LCS), based on the method of Verhoff et al. (1969Verhoff et al. ( , 1977, is developed for the rapid and accurate determination of the bivariate drop size-concentration distribution for reactive liquid-liquid dispersions. The method employs a precision bore capillary, through which a sample is drawn from the mixing vessel by a vacuum pump. An appropriate light source is used to distinguish between the slugs of dispersed phase and continuous phase as the sample passes by two detection points in the capillary. The optical device is designed to measure drop size by the difference of light refraction between the two phases and drop concentration by the light absorbance of the organic phase in the drop. The new technique can automatically measure drop-size and drop-concentration distributions of thousands of drops within a few minutes. This technique can provide important information on the state of a reactive dispersion in situ and can provide information on the influence of dispersed-phase mixing effects on mass transfer and/ or reactions in liquid-liquid dispersions. Further, the LCS technique provides the capability for on-line monitoring and control of units processing liquid dispersions.

Measuring bubble, drop and particle sizes in multiphase systems with ultrasound

“…The specific gas-liquid interfacial area is usually determined using a light scattering technique (Calderbank, 1958;Calderbank et al, 1960), or by simultaneous determination of the gas holdup and the bubble-size distribution. Methods to determine the bubble diameter include photography (with digital image analysis) (Machon et al, 1997;Pacek et al, 1994) and capillary techniques with light transmission analysis (Barigou and Greaves, 1991;Bae and Tavlarides, 1989) or by using contact probes (Burgess and Calderbank, 1975;Calderbank and Pereira, 1977). However, all these techniques have limited applicability, because they only allow for small volume fractions and require transparent solutions.…”

On‐line monitoring of chord distributions in liquid–liquid dispersions and suspension polymerizations by using the focused beam reflectance measurement technique

“…Several techniques have been developed since the second half of the twentieth century to study the bubbles/droplets/particle size distributions in heterogeneous systems (gas–liquid, liquid–liquid and solid–liquid) to understand and control the evolution of these distributions in chemical processes . These techniques are often based on laser spectroscopy, capillary spectroscopy , laser scattering , near‐infrared spectroscopy , and backscattered lighting .…”

Prediction of settling velocity of drops in a concentration batch liquid‐liquid dispersion

“…Moreover, g(n) has been assumed to be such that the flux,f(n), is convex. It should be remembered that in a liquid-liquid dispersion, though the number density of drops, n(v,x, t ) , can be measured experimentally [6,7], it is a tedius procedure. However, the volume fraction of the dispersed phase, E , which relates the number density through…”