Date of Award
1991
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Abstract
The present experimental work deals with the study of the hydrodynamic characteristics exhibited by a concurrent upflow gas-solids suspension under fully developed flow conditions in the dilute and the dense phase flow regimes. Pressure drop and the mean solids volumetric concentration were measured in vertical transport line of 20 mm inside diameter using sand particles with an average particle diameter of 210 {dollar}\mu{dollar}m. Mean solids concentration of more than 7 percent and solids loading ratios as high as 75 were obtained in the experiments. The mean solids concentration was measured by trapping the particles in a 4.32 m long test section with a set of pneumatic driven quick closing slide valves. The particle size distribution for the solids hold-up was also determined using sieve analysis.;By varying the solids mass flowrates while using the air velocity as the parameter, the dilute phase, 'dense phase 1', and possibly a third regime--'dense phase 2' were observed sequentially. Moreover, unstable operations which lead to the total plugging of the transport line were also experienced at some extreme conditions. The hydrodynamic behaviour such as the mean solids concentration and its average particle diameter, average solids velocity, average slip velocity, average slip velocities of the coarse and the fine fractions, and the pressure drop exhibited in each flow regime was analyzed. Results indicated that both the dilute and the dense phase 1 flow regimes possessed their own distinct hydrodynamic characteristics. However, the difference between those noticed in the dense phase 1 and in the dense phase 2 regimes was subtle. In the course of the experiments, negative solids-wall friction losses were observed at low transport gas velocities when the conveyor was operating in the dense phase regime. The particles in the coarse fraction appeared to travel at a significantly higher speed than the fines in the dilute phase flow. However, both fractions were being carried along at about the same velocities in the dense phase regime.;A power law relationship was developed to correlate the mean solids concentration with the solids mass flowrate and the transport gas velocity for the dilute phase regime. However, the same technique could not be extended to dense phase conveying due to the different solids flow behavior. A flow regime diagram based on the transport gas velocity and the solids mass flowrate was also presented to identify the operating conditions of the observed regimes as well as the limiting solids carrying capacities for the conveying system studied. The overall results point to the conclusion that different methods are required to treat the hydrodynamic characteristics inherent to each flow regime.
Recommended Citation
Mok, Steven Lai-kwok, "The Study Of The Hydrodynamic Characteristics Of Vertical Upflow Gas-solids Suspension In The Dilute And Dense Phase Regimes" (1991). Digitized Theses. 2103.
https://ir.lib.uwo.ca/digitizedtheses/2103