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Título: Characterization of rigid spargers and their selection for flotation columns
Autores: Escudero Garcia, Ramiro.
Fecha: 1998
Publicador: McGill University - MCGILL
Fuente:
Tipo: Electronic Thesis or Dissertation
Tema: Engineering, Chemical.
Engineering, Environmental.
Descripción: Rigid spargers are enjoying renewed interest in some flotation column applications such as de-inking of recycled paper and de-oiling of water. Sparger selection depends on the physical characteristics of the porous material, the liquid/slurry properties, and the dimensions of the column. There is no generally accepted method to select spargers for a given flotation column duty. A methodology for selecting stainless steel rigid spargers is proposed. The methodology is based on a target bubble size (db), gas holdup (epsilong), or bubble surface flux ( Sb). It combines two models: one for bubble formation at the sparger proposed by Kumar and Kuloor which relates bubble size to sparger characteristics, and drift flux analysis which relates mean bubble size, gas holdup, and gas rate.
Prediction of bubble size by the Kumar and Kuloor model requires a knowledge of an equivalent pore diameter (De) of the sparger. A procedure to estimate De by fitting the predicted and measured epsilong - Jg relationships is developed.
Comparison of bubble size measured photographically with that estimated from drift flux analysis, and predicted by the Kumar and Kuloor model shows acceptable agreement between the measured, estimated and predicted values.
By combining db predicted with drift flux analysis, and allowing for column dimensions, both the gas holdup and the bubble surface flux were predicted. A maximum in sparger surface area was found above which the gas holdup and the bubble surface flux do not increase.
Spargers were characterized according to their permeability (k ), by applying the Darcy law. Sparger homogeneity was established from this permeability measurement. A relationship between De and k was derived. For spargers with permeability up to 0.75 darcy (0.75 x 10-5 m2), the equivalent pore diameter was constant (De = 2 mum). For larger permeabilities De increased with permeability.
Application of the sparger selection criteria in a pilot unit (0.5 m diameter column) showed epsilong and Sb can be predicted with acceptable accuracy.
Idioma: en