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Learning unit 1 Part A 14 02 2022

Particulate Technology 3B
Dr Phathutshedzo Khangale
14 February 2022
Lecturer contact information
Dr Phathutshedzo Khangale
Room: 4131, John Orr Building
Phone: 011-559-6314
Email: pkhangale@uj.ac.za
Consultation times
Wednesday – 10:00 – 12:00
Important information
• Study guide
• Blackboard
• Graduate Attributes
• Assessment dates (tests and exams)
• Assessment weight
• Learning units
• Textbook
• Classroom activities
• Attendance
Important information
• Study guide
• Blackboard
❑Will be uploaded on Blackboard today
❑Primary medium of communication
❑Assessment – Major assessments on campus
❑Student collaboration/participation
• Assessment details
Important information
• Graduate Attributes
❑Graduate Attribute 2: Application of scientific
and engineering knowledge
Demonstrate competence to apply knowledge of mathematics, natural
science and engineering sciences to defined and applied engineering
procedures, processes, systems and methodologies to solve welldefined engineering problems;
❑Graduate Attribute 9: Independent Learning
Engage in independent and life-long learning through well- developed
(Semester Mark)
❑By participating and applying the principles that you will learn in this
course you will be able to master the following ECSA graduate
To be communicated
To be communicated
To be communicated
• Missing a test will jeopardize the class mark. If a learner is sick, contact the
lecturer within 3 days of the test date. You will be expected to produce a
medical certificate from an accredited doctor if you are sick or any
acceptable proof thereof!
• The pass mark for the course is 50% (except if you get less than 40% in the
exam – in this case you fail anyway).
• Students must fulfil the required graduate attributes, which are assessed as
explained in the study guide (failure to meet minimum requirements for both
GAs will results in the final mark being CAPPED at 35%).
Important information
• Learning units
• LU 1: Characteristics of Solid Materials
• Classroom activities
• Participate in class
• Participate in the group discussion
• LU 2: Production of Particulate Materials
• LU 3: Mixing Particulate Material
• LU 4: Relative Motion between Particles and fluids
• LU 5: Movement and storage of particulate Materials
• LU 6: Circular Motion of particles and the design of
• LU 7: Fluidisation
• LU 8: Sedimentation
• Attendance
• It is compulsory to attend all lectures. Attend at least
80% of your lectures, otherwise you will
automatically fail the module as your final mark will
be CAPPED at 35%.
• LU 9: Filtration
• Introduction to Particle Technology – Martin Rhodes
• Additional sources: Chemical Engineering Vol. 2 - Coulson and Richardson
Definition – Particle Technology
❑Particle technology is a term used to refer to the science and technology related to the handling
and processing of particles and powders.
❑Particle technology is also often described as powder technology, particle science and powder
❑Powders and particles are commonly referred to as bulk solids, particulate solids and granular
❑Today particle technology includes the study of liquid drops, emulsions and bubbles as well as
solid particles
Application Particulate Material
What are the industries that uses particulate
❑Particulate materials, powders or bulk solids are used widely in all areas of the process industries,
for example in the food processing, pharmaceutical, biotechnology, oil, chemical, mineral
processing, metallurgical, detergent, power generation, paint, plastics and cosmetics industries
Particle Size and Particle Shape Analysis
❑In many powder handling and processing operations particle size and size distribution play a key
role in determining the bulk properties of the powder.
❑Describing the size distribution of the particles making up a powder is therefore central in
characterizing the powder.
❑Particle size is important because this affects properties such as the surface per unit volume and the rate at
which a particle will settle in a fluid.
❑A particle shape may be regular, such as spherical or cubic, or it may be irregular, for example, a piece of
broken glass.
Particle characterization – Single Particles
❑The simplest shape of a particle is the sphere, because of its symmetry, any question of orientation does not
have to be considered, since the particle looks exactly the same from whatever direction it is viewed and
behaves in the same manner in a fluid. No other particle has this characteristic
❑A measure of particle shape which is frequently used is the sphericity, ψ, defined as:
❑Another method of indicating shape is to use the factor by which the cube of the size of the particle must be
multiplied to give the volume.
❑Other properties of the particle which may be of importance are whether it is crystalline or amorphous,
whether it is porous, and the properties of its surface, including roughness and presence of adsorbed films.
Single Particles
❑ Hardness may also be important if the particle is subjected
to heavy loading
❑ Feret’s diameter (distance between two tangents on
opposite sides of the particle) and shear diameter (particle
width obtained using an image shearing device) and
equivalent circle diameters such as the projected area
diameter (area of circle with same area as the projected
area of the particle resting in a stable position)
Figure 1.1. Feret’s diameter
• Sieve analysis
Measurement of particle size
• It is carried out using a nest of sieves, each lower sieve being
of smaller aperture size.
• Measurement of particle size and of particle size
distribution is a highly specialized topic, and
• The sieves may either be mounted on a vibrator, which
considerable skill is needed in the making of
should be designed to give a degree of vertical movement in
accurate measurements and in their interpretation.
addition to the horizontal vibration or may be hand shaken.
• Before a size analysis can be carried out, it is
• The efficiency of screening is defined as the
necessary to collect a representative sample of the
ratio of the mass of material which passes
solids, and then to reduce this to the quantity which
the screen to that which is capable of passing
is required for the chosen method of analysis.
• Sedimentation and elutriation methods (>1 μm)
Measurement of particle size
• These methods depend on the fact that the terminal falling
velocity of a particle in a fluid increases with size.
• Microscopic analysis (1–100 μm)
• Microscopic examination permits measurement of
the projected area of the particle and also enables
an assessment to be made of its two-dimensional
• The largest particles are deposited preferentially and
consequently the rate of increase of weight falls off
progressively as particles settle out.
• In general, the third dimension cannot be
determined except when using special
• 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.
• Automatic methods of scanning have been
• By using the electron microscope, the lower limit of
size can be reduced to about 0.001 μm.
• The elutriation method is a reverse sedimentation process
in which the particles are dispersed in an upward flowing
stream of fluid.
Measurement of particle size
• Laser diffraction analyzers
• X-ray or photo-sedimentometers
• These instruments exploit the radial light scattering • Instruments such as X-ray or photo-sedimentometers
distribution functions of particles.
serve to automate this method in a non-intrusive
• A suspension of particles is held in, or more usually
passed across, the path of a collimated beam of • This technique is limited to the analysis of particles
laser light, and the radially scattered light is collected whose settling behaviour follows Stokes’ law and to
by an array of photodetectors positioned conditions where any diffusive motion of particles is
perpendicular to the optical axis. The scattered light • negligible.
distribution is sampled and processed using
appropriate scattering models to provide a particle
size distribution.
• Instruments are available which provide particle size
information over the range 0.1–600 μm.
Measurement of particle size
• Sub-micron particle sizing
• Particles of a size of less than 2 μm are of particular
interest in Process Engineering because of their
large specific surface and colloidal properties.
• Photon correlation spectroscopy (PCS), may be
used to provide information about particle diffusion
Particle size distribution
• Most particulate systems of practical interest consist
of particles of a wide range of sizes, and it is
necessary to be able to give a quantitative indication
of the mean size and of the spread of sizes.
• The results of a size analysis can most conveniently
be represented by means of a cumulative mass
fraction curve, in which the proportion of particles (x)
smaller than a certain size (d) is plotted against that
size (d).
• From these results a cumulative size distribution can
be built up and this can then be approximated by a
smooth curve provided that the size intervals are
sufficiently small
Figure 1.1. Particle Size Distribution curve
(cumulative basis)
Figure 1.2. Particle Size Distribution curve
(frequency basis)
Mean particle size
• Mean size will describe only one particular
characteristic of the powder and it is important to
decide what that characteristic is before the mean is
calculated. Thus, it may be desirable to define the
size of particle such that its mass or its surface or its
length is the mean value for all the particles in the
Figure 1.4. Particle Size Distribution curve
Figure 1.3. Particle Size Distribution curve
❑ For naturally occurring materials the curve will
generally have a single peak.
❑ For mixtures of particles, there may be as many
peaks as components in the mixture.
• Mean sizes based on surface
Mean particle size
• Mean sizes based on volume
Mean particle size
• Mean dimensions based on length
Exercise 1.1
• The size analysis of a powdered material on a mass
basis is represented by a straight line from 0 per
cent mass at 1 μm particle size to 100 per cent
mass at 101 μm particle size as shown in Figure 1.5.
• Calculate the surface mean diameter of the
particles constituting the system.
Figure 1.5. Size analysis of powder