vā = (Ļā ā Ļā) g dĀ² / (18 Ī¼)vā: m/s; Ļ: kg/mĀ³; d: m; Ī¼: PaĀ·s.
Use when: Stokes' law: isolated spherical particle, Newtonian fluid, creeping regime; not directly valid for any concentrated pulp.
Slurry settling and filtration
Compare gravity sedimentation and filtration under pressure difference.
What is happening?
In settling, the particles move under the effect of gravity and form a more concentrated zone. Flocculation can increase aggregate size, but excess flocculant does not necessarily improve separation.
In filtration, the liquid passes through a porous medium and a cake of solids. The resistance of the cake often increases with the mass deposited, which can slow the flow rate at imposed pressure.
The formulas, with their conditions.
Q = A ĪP / [Ī¼ (Rm + Rc)]Q: mĀ³/s; A: mĀ²; ĪP: Pa; resistances R: mā»Ā¹.
Use when: Darcy's law in the form of medium and cake resistances.
Where is this principle used?
Hydrometallurgical plant
Clarify a solution and recover residues.
Water treatment plant
Thicken and dehydrate sludge.
What to observe in the experiment
Compare the initial filtration flow rate and its evolution with the thickness of the cake, at constant pressure.
References and readings
This sheet explains the principles and their assumptions. Educational simulation can simplify the process; an industrial model requires suitable data and validation.
Have you understood the essentials?
Only one correct answer per question. Answer all three questions, then view the answer key.
Intu Lab Ā· Understanding sheet Ā· Kimba Christian