ParTech, Sedi Flashcards
Resistance to indentation
Resistance to scratching
Hardness
Ease with which a substance may be broken by impact
Brittleness or Friability
Data for particle sizes are usually expressed in terms of the fraction retained in a screen
Particle Size Analysis
Equivalent Diameter Equation
Diameter of a sphere of equal volume as
that of the particle
Sphericity Equation
Sphericity = 6V/D*S
Units for particle size:
Coarse particles
inch or mm
Units for particle size:
Fine particles
mesh size
Units for particle size:
Very fine particles
um or nm
Units for particle size:
Ultrafine particles
m^2/gram
Screening
Separation of a mixture of particles of various sizes into two or more portions,
Dry Screening
Treatment of a material containing a natural amount of moisture
Wet Screening
Water is added to the material being treated to wash the fine material through the screen
Screen Aperture
Clear space between individual wires of the screen
Mesh
Number of apertures per linear inch
Oversize
+ Material
The material that fails to pass through the screen openings
Undersize
- Material
The material that passes through the screen openings
Screen blinding
Clogging of the screen openings with sample particles
Sieving
For determination of particle size
distribution
Closed circuit operation
Oversize material is returned to the crusher
Open circuit operation
No material is returned to the crusher
Sieving
For determination of particle size
distribution
Thickener / Clarifier
Industrial unit in which the concentration of a suspension is increased by sedimentation, with the formation of a clear liquid
Thickening
Often referred to as “dewatering”.
Centrifugal Separators
Used to enhance settling time of particles
Sieving
For determination of particle size
distribution
FLUIDIZATION STAGE:
it is the fluidization stage wherein particles remain in contact with one another and the bed structure remain stable until the velocity is increased to the point where pressure drop is balanced by the weight per unit area of the particles
fixed bed
FLUIDIZATION STAGE:
in gas-fluidized systems, it is the region where the dominant pattern is one of the vertically upward transport of particles , essentially gas-solids transport or pneumatic conveying
fast fluidization
FLUIDIZATION STAGE:
it is the stage where in the bed continues to flow upward even at constant velocity . there is no trend for bed height and pressure drop
mobilized bed
FLUIDIZATION STAGE:
in this stage it is when the particles are hoovering in the fluid , drag force balances the weight of the particles , the bed height increases and it has constant pressure drop
fluidized bed
Equation used to describe flow of fluid through a porous medium under laminar condition is ____
Kozeny-Carman Equation
Sedimentation
Operation by which solids are separated from liquids due to the difference in their respective densities
SEDIMENTATION MECHANISM:
Regardless of their properties, the particles are sufficiently far apart to settle freely.
Dilute / Free Sedimentation
The ultimate velocity when the acceleration force and resisting (buoyant & drag) force are equal. Remains constant in this velocity afterwards.
Terminal Velocity
Classification
Separation of solid particles into several fractions based upon their terminal velocities.
SEDIMENTATION MECHANISM:
Settling at high concentrations. Particles no longer settle individually.
Hindered Sedimentation
SEDIMENTATION MECHANISM:
Channels of fluid forces through the particle mass
Channeling
SEDIMENTATION MECHANISM:
When the suspension zone disappears, and all the solids are contained in the sediment
Critical Sedimentation Point
SEDIMENTATION MECHANISM:
Particles closer to the base will be compressed by the mass of solids above,
Compression
Create large conglomerations of elementary particles with occluded liquid.
Flocculation
Addition of electrolytes to form ions to neutralize charges of particles (electrolyte cation neutralize negative particles and such).
Coagulation
Methods used in Thickener Calculation
a. Yoshioka Construction (Graphical)
b. Talmadge and Fitch Method
PRESSURE DROP IN FIXED BEDS:
Laminar Flow
Kozeny-Carman
Re < 1.0
PRESSURE DROP IN FIXED BEDS:
Turbulent Flow
Burke-Plummer equation
Re > 1000
PRESSURE DROP IN FIXED BEDS:
Laminar and Turbulent Flow
Ergun equation
FLUIDIZATION REGIMES:
Describe dP/l vs velocity and bed height for
Fixed Bed
Increasing dP/l
Constant bed height
FLUIDIZATION REGIMES:
Describe dP/l vs velocity and bed height for
Fluidized Bed
Highest dP/l
FLUIDIZATION REGIMES:
Describe dP/l vs velocity and bed height for
Transport Regime
Decreasing dP/l
Increases bed height
CLASSIFIER TYPES:
1. Gravity
2. Sorting
- Gravity
Based on Particle Size - Sorting
Particle Densities
Factors affecting Centrifuge
- Feed Characteristics
- Equipment Size
- Operating Parameters
*Bowl speed
*Water depth
*Differential spiral feed
