CE20226 - Particle Tech Ming Flashcards
What’s particle technology?
The branch of science and engineering dealing with the production, handling, modification, and use of a wide variety of particulate materials, both wet or dry, in sizes ranging from nanometers to centimeters.
What are the (4 main) different unit operations for particle technology?
Size reduction Size enlargement Separation Mixing Storage, transport and dosage Particle characterisation (Size and shape analysis)
What are examples of size reduction, size enlargement, separation
and mixing processes?
Size reduction •Crushing •Grinding •Milling •Cutting / Slicing •Defibrating •Deagglomerating
Size enlargement •Agglomeration •Briquetting •Pelletizing •Coating •Compacting
Separating •Screening •Sieving •Grading •Sedimentation •Filtration
Mixing •Homogenizing •Stirring •Emulsifying •Spraying / Dispersing •Nebulizing / Pulverizing
What’s a dispersed system?
A system where particles or droplets are dispersed in a continuous phase.
Particle technology deals with particulate materials, bulk solids or powders, and particles or droplets that are contained within a gas or a liquid. Such particle collectives are named “Dispersed systems”.
Dispersed systems usually consist of many single particles - the dispersed phase - and the surrounding medium -the continuous phase. Both dispersed phase and the continuous phase can be solid, liquid or gaseous.
How are the volume concentrations and mass concentrations of the dispersed phase in a dispersed system found?
c. v = Vd / Vt
c. m = md / Vt
Where d represents the dispersed phase value.
How does specific surface area change with particle size?
Sv ~ 1/x
What are the properties of particles as their size is decreased?
specific surface area increases: SV ≈ 1/x
adhesive forces increase vs mass forces
increased tendency to agglomerate and stick to surfaces
pellets and agglomerates become more stable
free-flowing properties (flowablity) decreases
bulk-density decreases and porosity increases
mixing becomes more difficult but less self-segregation
reactivity increases
solubility, vapour-pressure and reaction rate increase
drag force increases vs mass force under flow conditions
electrostatic interactions increase
optical properties change (scattering, diffraction, reflection, absorption)
homogeneity of single particles increases: rigidity increases and grindablity decreases
What are the most important characteristics of a particle?
Size - affects properties such as SA:V and the rate at which a particle will settle in a fluid.
Shape - regular (e.g. spherical or cubical) or irregular (grains, corn flakes)
Composition - determines properties such as density and conductivity.
In many cases, the particle is not complete uniform. Particles might be porous or may be consist of a continuous matrix in which small particles of a second material are distributed.
What must be considered when choosing a method for particle size analysis?
Nature of the material to be sized, e.g. – Estimated particle size and particle size range – Solubility – Ease of handling – Toxicity – Flowability – Intended use
Cost
– Capital
– Running
Specification requirements
What are the 4 main particle size measurement techniques?
Sieve
Microscope
Sedimentation
Laser diffraction analysis
What are the features of sieving for particle size measurement?
Considers weight distribution
Sieve analysis is performed using a nest or stack of sieves where each lower sieve has a smaller aperture size than that of the sieve above it.
Sieves can be referred to either by their aperture size = mesh size = sieve number
The mesh size is the number of wires per linear inch.
– 250 μm = No. 60
– 125 μm = No. 120
Sieving may be performed wet or dry, by machine or by hand, or a fixed time or until powder passes through the sieve at a constant low rate.
Advantages and disadvantages of sieving:
Advantages
– Easy to perform
– Wide size range
– Inexpensive
Disadvantages – Known problems of reproducibility – Wear/damage in use or cleaning – Irregular/agglomerated particles – Rod-like particles : overestimate of under-size – Labour intensive
What are the features of microscopy for particle size measurement?
2 main types: optical and electron microscopes
Considers number distribution
Being able to examine each particle individually has led to microscopy being considered as an absolute measurement of particle size.
Can distinguish aggregates from single particles
Can be coupled to image analysis computers, each field can be examined, and a distribution obtained
Most severe limitation of optical microscopy is the depth of focus being about 10μm at x100 and only 0.5μm at x1000
Advantages and disadvantages of optical microscopy:
Advantages: – Relatively inexpensive – Each particle individually examined: detect aggregates, 2D shape, colour – Permanent record e.g., photograph – Small sample sizes required
Disadvantages:
– Time consuming - high operator fatigue
– Very low throughput (amount of material passing though)
– No information on 3D shape
– Certain amount of subjectivity
Advantages and disadvantages of electron microscopy:
Advantages:
– Particles are individually examined
– Visual means to see sub-micron specimens
– Particle shape can be measured
Disadvantages: – Very expensive – Time consuming sample preparation – Materials limitation – Low throughput - not for routine use
What are the features of sedimentation for particle size measurement?
Considers wight distribution, and different between fluid and particle density
These methods depend on the fact that the terminal velocity of a particle in a fluid increases with size.
2 categories:
Incremental: changes with time in the concentration or density of the suspension at known depths are determined.
Cumulative: the rate at which the powder is settling out of suspension is determined.
What’s stokes diameter?
The diameter of the sphere that would settle at the same rate as the particle.
Advantages and disadvantages of sedimentation:
Advantages:
– Equipment required can be relatively simple and inexpensive.
– Can measure a wide range of sizes with accuracy and reproducibility.
Disadvantages:
– Sedimentation analyses must be carried out at concentrations which are sufficiently low for interactive effects between particles to be negligible so that their terminal falling velocities can be taken as equal to those of isolated particles.
– Large particles create turbulence, are slowed and are recorded undersize.
– Particle re-aggregation during extended measurements.
– Particles have to be completely insoluble in the suspending liquid.
What are features of laser light scattering particle measurement?
Considers volume distribution.
Particles pass through a laser beam and the light scattered by them is collected over a range of angles in the forward direction.
The angles of diffraction are, in the simplest case inversely related to the particle size.
Advantages and disadvantages of laser light scattering for particle measurement:
Advantages:
– Non-intrusive : uses a low power laser beam
– Fast : typically <3minutes to take a measurement and analyse.
– Precise and wide range.
– Absolute measurement, no calibration is required.
– Simple to use
– Highly versatile
Disadvantages:
– expense
– volume measurement all other outputs are numerical transformations of this basic output form, assuming spherical particles
– must be a difference in refractive indices between particles and suspending medium
What are the different statistical diameters to identify the equivalent spherical diameter?
Martins’s Diameter: The distance between opposite sides of a particle are measured on a line bisecting the projected area.
Feret’s Diameter: The distance between parallel tangents on opposite sides of the particle profile.
Both Martin’s and Feret’s diameters are generally used for particle size analysis by optical and electron microscopy.
What are equivalent diameters?
Equivalent diameter is the diameter of a circle or a sphere with the same characteristics than the considered particle. This can be both geometric or physical equivalent diameters d.
Equivalent Circle Diameter: the diameter of a circle having an area equal to the projected area of the particle in random orientation.
Equivalent Spherical Diameter: the diameter of a sphere that has the same volume as the irregular particle being examined.
What are the different equivalent diameters?
- dV: Equivalent diameter of a sphere with the same volume
- dS: Equivalent diameter of a sphere with the same surface area
- dP: Equivalent diameter of a circle with the same projected surface area
- dPe: Equivalent diameter of circle with same circumference than particle image
- dW: Equivalent diameter of a sphere with the same terminal settling velocity
- dSt: “Stokes diameter” – Terminal setting velocity in the Stokes region
Equivalent Circle Diameter: the diameter of a circle having an area equal to the projected area of the particle in random orientation.
Equivalent Spherical Diameter: the diameter of a sphere that has the same volume as the irregular particle being examined.
How can particle shape be described?
Spherical Angular Irregular Flake Spheroidal Granular Geometric Etc
How can particle size be defined, considering the particle to be a sphere?
Assumption: Simplest shape is the sphere – same from all directions
Particle shape can be characterised by comparing it to a sphere in one of two ways:
1) Equivalent diameter is the diameter of a sphere of equivalent volume.
2) Sphericity is given as:
Ø = SA of sphere of same vol as particle / SA of particle
= dv/ds
= 6Vp / (de*Sp)
Where:
Vp - particle volume
de - equivalent diameter
Sp - particle SA
How is particle sphericity calculated?
Ø = SA of sphere of same vol as particle / SA of particle
= dv/ds
= 6Vp / (de*Sp)
Where:
Vp - particle volume
de - equivalent diameter
Sp - particle SA
What is a monodisperse particle distribution?
When all particles are the same size
What is a polydisperse particle distribution?
When there is a wide distribution with particles of many sizes
What’s a distribution display (considering particle size)?
A graph of volume against particle size considering histograms, differential distributions and cumulative distributions of the particles in a sample.
What are the typical particle size distributions?
Normal distribution: particles resulting from growth processes e.g. natural products such as grains, crystallised products, granules agglomeration.
Log normal distribution: particles resulting from natural size reduction processes or industrial crushing e.g. sand, crushed rocks.
Rosin-Rammler distribution: fine and ultrafine industrial size reduction processes e.g. cement, pigments.
What are the 3 main dispersed systems?
Molecular dispersions
Colloidal dispersions
Coarse dispersions
What are properties of molecular dispersions?
- Particles invisible in electron microscope
- Pass through semipermeable membranes and filter paper
- Particles do not settle down on standing
- Undergo rapid diffusion
- E.g. ordinary ions, glucose
What are properties of colloidal dispersions?
- Particles not resolved by ordinary microscope, can be detected by electron microscope.
- Pass through filter paper but not pass through semipermeable membrane.
- Particles made to settle by centrifugation
- Diffuse very slowly
- E.g. colloidal silver sols, naural and synthetic polymers
What are properties of course dispersions?
- Particles are visible under ordinary microscope
- Do not pass through filter paper or semipermeable membrane.
- Particles settle down under gravity
- Do not diffuse
- E.g. emulsions, suspensions, red blood cells
What are colloids?
A homogeneous non-crystalline substance consisting of large molecules or ultramicroscopic particles of one substance dispersed through a second substance.
Colloids include gels, sols, and emulsions; the particles do not settle, and cannot be separated out by ordinary filtering or centrifuging like those in a suspension.
What are the 3 classifications of a dispersed system?
Hydrophilic colloidal dispersion (in water)
- surfactant micelles and phospholipid vesicles, also known as association colloids.
Lyophilic colloids (lyo=solvent) - colloidal systems are proteins, rubber, gelatin and gums.
Lyophobic colloids
- gold, silver and sulfur.
What are properties of the sizes and shapes of colloids?
Particles lying in the colloidal size have large surface area when compared with the surface area of an equal volume of larger particles.
The possession of large specific surface results in:
1- platinium is effective as catalyst only when found in colloidal form due to large surface area which adsorb reactant on their surface.
2- The colour of colloidal dispersion is related to the size of the paticles
e.g. red gold sol takes a blue colour when the particles increase in size.
The shape of colloidal particles in dispersion is important:
The more extended the particle, the greater its specific surface, the greater the attractive force between the particles of the dispersed phase and the dispersion medium.
Flow, sedimentation and osmotic pressure of the colloidal system affected by the shape of colloidal particles.
• Particle shape may also influence the pharmacologic action.
How are colloidal solutions purified?
1) Dialysis:
Semipermeable cellophane membrane prevent the passage of colloidal particles, yet allow the passage of small molecules or electrolytes.
2) Electrodialysis:
In the dialysis unit, the movement of ions across the membrane can be sped up by applying an electric current through the electrodes induced in the solution.
- The most important use of dialysis is the purification of blood in artificial kidney machines.
- The dialysis membrane allows small particles (ions) to pass through but the colloidal size particles (haemoglobin) do not pass through the membrane.
What’s the Faraday-Tyndall effect?
When a strong beam of light is passed through a colloidal solution, the path of light is illuminated (a visible cone formed).
- This phenomenon resulting from the scattering of light by the colloidal particles (doesn’t occur with pure solutions)
What are the optical properties of colloids?
When a strong beam of light is passed through a colloidal sol, the path of light is illuminated (a visible cone formed)
- light scattering depends on Tyndall effect. It’s described in terms of turbidity.
Ultra-microscope has declined in recent years as it does not able to resolve lyophilic colloids. Thus electron microscopes are capable of yielding pictures of actual particles size, shape and structure of colloidal particles.
What’s turbidity?
Turbidity: the fractional decrease in intensity due to scattering as the incident light passes through 1 cm of solution.
- Turbidity is proportional to the molecular weight of lyophilic colloid
How does Brownian motion change with viscosity?
This brownian motion arises due to the uneven distribution of the collisions between colloid particle and the solvent molecules.
- Brownian movement was more rapid for smaller particles.
- It decreases with increase the viscosity of the medium.
What’s Fick’s first law?
Used to describe diffusion.
dq = - DA(dc/dx)dt
How is osmotic Pressure found?
Pi = cRT
What does Stokes’ law show?
The rate of sedimentation (v)
What affects viscosity of colloids?
The viscosity of colloidal dispersion is affected by the shape of particles of the disperse phase:
Spherocolloids - dispersions of low viscosity
Linear particles - more viscous dispersions
Are colloids charged?
The particles of a colloidal solution are electrically charged and carry the same type of charge, either negative or positive.
The colloidal particles therefore repel each other and do not cluster together to settle down.
The charge on colloidal particles arises because of the dissociation of the molecular electrolyte on the surface.
How is electrophoresis applied to colloids?
Electrophoresis is the most known electrokinetic phenomena. It refers to the motion of charged particles related to the fluid under the influence of an applied electric field.
If an electric potential is applied to a colloid, the charged colloidal particles move toward the oppositely charged electrode.
What’s electro-osmosis.
It is the opposite in principal to that of electrophoresis.
- When electrodes are placed across a clay mass and a direct current is applied, water in the clay pore space is transported to the cathodically charged electrode by electro-osmosis.
- Electro-osmotic transport of water through a clay is a result of diffuse double layer cations in the clay pores being attracted to a negatively charged electrode or cathode. As these cations move toward the cathode, they bring with them water molecules that clump around the cations as a consequence of their dipolar nature.
What’s sedimentation potential?
The sedimentation potential also called the Donnan effect.
- It is the potential induced by the fall of a charged particle under an external force field.
- It is analogous to electrophoresis in the sense that a local electric field is induced as a result of its motion.
- If a colloidal suspension has a gradient of concentration (such as is produced in sedimentation or centrifugation), then a macroscopic electric field is generated by the charge imbalance appearing at the top and bottom of the sample column.
What forces act on particles in a fluid?
Drag Gravity Lift Electric Diffusion as correction factor (for very small particles)
What are examples of mass forces affecting particles?
Inertia
Centrifugal
Gravity
What are examples of surface forces acting on particles?
Drag
Buoyancy
Lift
What are examples of field forces affecting particles?
Electric
Magnetic
Diffusion
What’s stokes law?
An expression describing the resisting force on a particle moving through a viscous fluid and showing that a maximum velocity is reached in such cases, e.g. for an object falling under gravity through a fluid.
Fd = 3pimudu
Where Fd is drag force, mu is fluid viscosity, u is fluid velocity relative to the particle, d is particle diameter.
How is Reynolds calculated?
Re = rhoud/mu
How do flow conditions vary with Re?
As Re’ increases the skin drag becomes proportionally smaller
At values greater 20 flow separation occurs
At values above 100 – 200 vortex shedding occurs
Even higher Re’ lead to fully developed wake
How is drag coefficient calculated?
Cd = R/(rho*u2)
Where R is force per h it projected area of particle in a plane perpendicular to the direction of motion.
For a sphere. The projected area is that of a circle of the same diameter as the sphere.
What are the 4 regions of a drag coefficient - Reynolds number graph?
1) Linear slope (-1), the upper limit of Re for which is 0.2.
2) Transition / intermediate region. Curve progressively changes from -1 to 0 as Re increases.
3) Cd is approximately constant (at 0.22)
4) When are exceeds 2 e^5, the flow in the boundary layer changes from streamline to turbulent, and separation occurs nearer the rear of the particle. In this case, drag force is decreases considerably and Cd is roughly 0.05.
What’s terminal falling velocity?
Velocity at which gravity and resistive forces are balanced.
What assumptions are made for the drag coefficient equations?
- Settling isn’t affected by the presence of other particles in the fluid. This is known as free settling. When there’s interference of other particles, it is known as hindered settling.
- Walls of containing vessel don’t affect settling.
- The fluid is considered a continuous medium, and the particle size is large compared with mean free path of molecules of the fluid.
What’s centrifugal force?
An object travelling in a circle behaves as if it is experiencing an outward force
The centrifugal force depends on the mass of the object, the speed of rotation, and the distance from the centre
Centrifuges are extensively used for separating fine particles, even colloids.
Centrifugal acceleration = rw^2
Centrifugal force = ma = mrw^2
How does gravity settling compare to centrifugal settling?
Gravity: F = mg Acceleration constant In direction of earth Equilibrium velocity reached Terminal velocity given by:
u = d^2(d.rho)g/ 18*mu
Centrifugal: F = mrω2 Acceleration increases with r Acceleration increases with ω Away from axis of rotation Equilibrium velocity never reached Instantaneous velocity:
u = u.t* rw^2/g
What are the (4) main types of centrifuge?
Tubular bowl
Disc bowl
Perforate bowl basket
Zonal ultracentrifuge
What are properties of tubular bowl centrifuges?
- Most useful for solid-liquid separation with enzymatic isolation
- Can get good separation of microbial cells in solution
Properties of tubular centrifuges:
The bowl is tall and has a narrow diameter, 1–=150 mm.
Such centrifuge, known as super-centrifuges, develop a force about 13000 times the force of gravity.
Some narrow, centrifuges.
Having a diameter of 75 mm and very high speeds or so rev/min, are known as ultracentrifuges
These centrifuges are often used to separate liquid-liquid emulsions.
Properties of disk bowel centrifuge:
- Used for removing cells and animal debris
- Can partially remove microbial and animal cell debris
The feed enters the actual compartment at the bottom and travels upward through vertically spaced feed holes, filling the spaces between the disks
The holes divide the vertical assembly into an inner section, where mostly light liquid is present, and an outer section, where mainly heavy liquid is present. The heavy liquid flows beneath the underside of a disk to the periphery of the bowl
The light liquid flows over the upper side of the disks and toward the inner outlet
Any small amount of heavy solids is thrown outer wall
Periodic cleaning is required to remove solids deposited
Disk bowl centrifuges are used in starch-gluten separation, concentration of rubber latex, and cream separation
How is centrifugal acceleration calculated?
a = rw^2
Where r is radius and w is angular velocity
How is centripetal force calculated?
F = mrw^2
Since w = v / r (angular velocity = velocity / radius)
F = mv^2/2
How is angular velocity calculated?
w = 2πf = 2π/t = 2πN/60
How does separation by centrifuge depend on the distance, r, which the particles travel?
After the residence time, the particle is at distance r.B from the axis of rotation.
(where r2 is the radius of the centrifuge: )
If r.B < r2, the particles will leave the fluid
If r.B = r2, particles are deposited on the wall if the bowl and effectively removed from the liquid.
Particles that don’t reach the wall will exit with the liquid.
How is the terminal settling velocity at radius, r, for settling in the Stokes’ law range found?
v = (w^2rD.p^2(rho.p - rho)/18*mu = dr / dt
which can be integrated to find residence time (liquid volume / feed volumetric flowrate)
What’s the cut point / critical diameter (D.pc)?
The diameter of a particle that reaches half the distance between r1 and r2.
= (r2-r1)/2
(where r2 is the distance from the centre of the centrifuge to the bowl wall, and r1 is from the centrifuge centre to the liquid surface boundary along the centrifuge).
How do forces develop in centrifugal separation?
During centrifugation, a slurry feed of solid particles and liquid is admitted at the center.
The feed enters and is immediately thrown outward to the walls of the container.
The liquid and solids are now acted upon by the vertical and the horizontal centrifugal forces.
The liquid layer then assumes the equilibrium position, with the surface almost vertical.
The particles settle horizontally outward and press against the vertical bowl wall.
Liquids having different densities are being separated by the centrifuge.
The denser fluid will occupy the outer periphery, since the centrifugal force on it is
Features of cyclones:
They separate particles through centrifugal forces
No moving parts
Separate in overflow (smaller/lower density) and underflow (larger/higher density)
What 2 main factors affect cyclone efficiency?
The velocity at which particles move towards the wall / or collection area of cyclone where it is theoretically collected
Length of time available for collection (residence time)
How can cyclone performance be described?
By 2 main metrics:
Pressure drop and the fractional efficiency curve (FEC)
Benefits of using cyclones:
Dry No moving parts Robust Construction Can be easily designed for very severe duty (examples) Low cost (sometimes) Safety
They’re used when it’s the most economical solution
What are the different flow patterns within cyclones?
Tangential - Tangential velocity exposes particles to centrifugal field. Critical for operation. If too slow no centrifugal field
Radial - Radial flow of particles away from centre and net flow of liquid towards centre.
Axial - Axial flow takes material either to overflow or underflow. Since the axial flow separates into overflow and underflow there is a locus (zone) with net zero velocity (LZVV)
What occurs in axial flow?
Axial flow takes material either to overflow or underflow. Since the axial flow separates into overflow and underflow there is a locus (zone) with net zero velocity (LZVV)
Particles that orbit at radial distance > LZVV will be carried to the underflow
Particles that orbit at radial distance < LZVV will be carried to the overflow
Particles that orbit at radial distance = LZVV have no preference
How are cyclones designed?
Typically, a particulate-laden gas enters tangentially near the top of the cyclone.
The gas flow is forced into a downward spiral simply because of the cyclone’s shape and the tangential entry.
Another type of cyclone (a vane-axial cyclone) employs an axial inlet with fixed turning vanes to achieve a spiraling flow.
Centrifugal force and inertia cause the particles to move outward, collide with the outer wall, and then slide downward to the bottom of the device.
Near the bottom of the cyclone, the gas reverses its downward spiral and moves upward in a smaller inner spiral.
The cleaned gas exits from the top through a “vortex-finder” tube, and the particles exit from the bottom of the cyclone through a pipe sealed by a spring- loaded flapper valve or rotary valve.
How efficient are cyclones?
Cyclones have often been regarded as low-efficiency collectors.
However, efficiency varies greatly with particle size and cyclone design.
Some cyclone manufacturers advertise cyclones that have efficiencies greater than 98% for particles larger than 5 microns, and others that routinely achieve efficiencies of 90% for particles larger than 15 – 20 microns.
In general, operating costs increase with efficiency (higher efficiency requires higher inflow pressure), and three categories of cyclones are available: high efficiency, conventional, and high throughput.
How is the number of turns in the cyclone device calculated?
N = 1/H * (Lb + Lc/2)
Where:
H is height of inlet duct
Lb is length of cyclone body
Lc is vertical length of cyclone cone
How is gas residence time for the outer vortex of a cyclone found?
t = path length / speed
= piDN/Vi
Where:
D is cyclone body diameter
Vi is gas inlet velocity
N is number of turns in cyclone
How is particle drift velocity (in radial direction) found?
Vt = W / dt
Where dt is residence time and W is inlet width.
It is also a function of particle size
What does LZVV stand for?
Locus of zero vertical velocity
What’s mixing and what are some types?
Combining substances into one mass
Perfect
Random
Segregating
What are the 3 important objectives if mixing statistics?
Quantifying goodness of mixture
Assessing acceptability of mixtures regarding product specifications
Determining mixing times and evaluating different mixers
What’s random sampling?
When each component has the same chance to be present in a sample
What’s representative sampling?
Number of particles, z, in sample is much larger than 1 but…
What does the Lacey mixing index consider?
The ratio (b) of mixing achieved to mixing possible
What are the different segregation mechanisms?
Trajectory segregation
Segregation caused by flowing air
What must be considered in representative sampling?
Simple size?
Best location for sampling?
How many samples to take and how often?
Sampling rules for best results:
Powder should be samples when in motion
Take samples along whole diameter
Take samples of whole stream at time intervals…
What are the 3 main reasons for particle size reduction?
To generate a desired particle size, form or size distribution
Increase surface size for increased chemical/physical reactivity
Separation of heterogeneous materials
How is a particle broken down?
It needs to be stressed by the comminution (Size reduction machine)
Forces on the outside of the particle by the machine or neighbouring particles
Deformation within the particle
Initial fracture to induce local tensions
Example stress mechanisms:
Stress applied between 2 surfaces - Pressure, shear, hit, cut, stock etc
Stress applied at single surface - particles hitting walls, or each other
Stress fro, surrounding medium - shearing current, sonication, cavitation
Stress applied by non-mechanical energy - thermal, electromagnetic, chemical – induced.
What are the 3 laws for particle size reduction energy requirement?
Rittinger’s law
Kick’s law
Bond’s law
What’s Rittinger’s law?
Energy for particle size reduction is directly proportional to the increase in surface. p = -2, KR is the crushing strength of the material, fc is the Rittinger constant.
E = KR*fc(1/L2 - 1/L1)
Rittinger’s law (mainly applicable for fine grinding and large increase of surface area)
What’s Kick’s law?
Energy needed in any size reduction process is directly proportional to the ratio of the volume of the feed particle to the product particle.
E = Kkfcln(L1/L2)
Kk is Kick’s constant
What’s Bond’s law?
It calculates the energy required to reduce the top particle size of the material from size L1 to L2.
Eb = Ei*(10/(L2)^0.5 -10/(L1)^0.5)
What’s agglomeration?
What are the different u it processes for agglomeration?
Mechanical unit processes to cluster and link small dispersed particles to larger entities.
Unit operations:
- flocculation
- granulation
- compacting
- sintering
What are the different material and non-material bonds?
— Material —
Solid bridges:
- sintered
- crystallisation
Liquid bridges:
- adsorption layers
- capillary bridges
— Without material bond —
Attraction forces:
-van-der-waal
….
