The New Jersey Institute of Technology's
Electronic Theses & Dissertations Project

Title:	Use of an optical probe to measure bubble characteristics in gas fluidized beds
Author:	Chu, Thomas Tai-Pai
View Online:	njit-etd1984-015 (xi, 141 pages ~ 5.0 MB pdf)
Department:	Department of Chemical Engineering and Chemistry
Degree:	Doctor of Engineering Science
Program:	Chemical Engineering
Document Type:	Dissertation
Advisory Committee:	Perna, Angelo J. (Committee chair) Huang, Ching-Rong (Committee member) Lewandowski, Gordon (Committee member) Klapper, Jacob (Committee member) Wong, Wing T. (Committee member)
Date:	1984
Keywords:	Fluidization. Bubbles. Probes (Electronic instruments).
Availability:	Unrestricted
Abstract:	A novel optical probe has been developed and used for on-line monitoring of the bubble characteristics in a three-dimensional gas fluidized bed. The probe sensor has a major dimension of 1.8 cm, and contains an LED and a photo-cell separated by a gap of 2.5 mm. Coupled with a non-inverting comparator circuit with hysteresis as a noise filter, the probe has been very effective in characterizing the size distribution, shape and velocity of gas bubbles. A 96 liter rectangular fluidized bed was used, containing glass beads with a size fraction of 355μ to 250μ. Air was the fluidizing medium, with gas velocities ranging from 1.2 Umf to 2 Umf. The probe position was varied from 35 to 55 cm above the distributor, and 0 to 8 cm from the bed centerline. The bubble size distribution was fit to a truncated gamma function. It was also found that the Davies-Taylor Equation for bubble velocity was inadequate to fit the data, since the velocity varied significantly with the position in the bed. Motion pictures were also taken in a two-dimensional bed to obtain qualitative information on bubble characteristics.