This document discusses particle analysis and screening. It begins by defining key particle properties like size, shape, and density. Different measurement techniques are described that characterize particles based on these properties. Average particle sizes are defined for mixtures using various means. Screen analysis is then covered, including how to perform sieve analysis using standardized screen sizes and how to analyze the results. Material balances for screening operations are also presented, showing equations to calculate flow rates of undersize and oversize particles based on feed rates and mass fractions.
The first lecture in the module Particle Technology, delivered to second year students who have already studied basic fluid mechanics. Some applications of Particle Technology are described, in industry and nature, and particle size analysis and means of representing the data. The format for the laboratory classes for the module and their reports are covered.
Detailed working of each equipments, formulas and calculations. Easy to understand. Very helpful for those students who face difficulty in making lab reports
The first lecture in the module Particle Technology, delivered to second year students who have already studied basic fluid mechanics. Some applications of Particle Technology are described, in industry and nature, and particle size analysis and means of representing the data. The format for the laboratory classes for the module and their reports are covered.
Detailed working of each equipments, formulas and calculations. Easy to understand. Very helpful for those students who face difficulty in making lab reports
This presentation is made to provide the overall conceptual knowledge on Chilton Colburn Analogy. It includes basis, importance, assumption, advantages, limitations and applications in addition to the derivation. Make It Useful!
Slides for the eLearning course Separation and purification processes in biorefineries (https://open-learn.xamk.fi) in IMPRESS project (https://www.spire2030.eu/impress).
Section: Mass transfer processes
Subject: 2.2 Molecular diffusion
(No "Download lock")........... Study it, Download it, Understand it, Apply it and Serve the community.
رَبِّ زدْنيِ عِلْماً (Arabic)..............Ameen.
PLEASE NOTE THIS IS PART-1
By Referring or said Learning This Presentation You Can Clear Your Basics Fundamental Doubts about Fluid Mechanics. In this Presentation You Will Learn about Fluid Pressure, Pressure at Point, Pascal's Law, Types Of Pressure and Pressure Measurements.
The word Micromeritics refers to a discipline of science and technology that deals with studies related to the fundamental as well derived properties of particles. The knowledge and control of the size of particles is of importance in pharmacy and materials science.
This presentation is made to provide the overall conceptual knowledge on Chilton Colburn Analogy. It includes basis, importance, assumption, advantages, limitations and applications in addition to the derivation. Make It Useful!
Slides for the eLearning course Separation and purification processes in biorefineries (https://open-learn.xamk.fi) in IMPRESS project (https://www.spire2030.eu/impress).
Section: Mass transfer processes
Subject: 2.2 Molecular diffusion
(No "Download lock")........... Study it, Download it, Understand it, Apply it and Serve the community.
رَبِّ زدْنيِ عِلْماً (Arabic)..............Ameen.
PLEASE NOTE THIS IS PART-1
By Referring or said Learning This Presentation You Can Clear Your Basics Fundamental Doubts about Fluid Mechanics. In this Presentation You Will Learn about Fluid Pressure, Pressure at Point, Pascal's Law, Types Of Pressure and Pressure Measurements.
The word Micromeritics refers to a discipline of science and technology that deals with studies related to the fundamental as well derived properties of particles. The knowledge and control of the size of particles is of importance in pharmacy and materials science.
a complete description of the particle size distribution of particles in different categories. Sedimentation is a phenomenon that completely work with the size of particles.
This is a comprehensive presentation on particle size distribution. A fundamental property in bulk solids handling.
Link to file: https://drive.google.com/open?id=11dn9O0onwCLaX44R6ApNLhi9PHYGdLr6
This presentation includes characteristics of an individual particle in a powder or in a mixture, mean particle size of a mixture or a powder, particle size distribution, fineness modulus etc.
Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
NO1 Uk best vashikaran specialist in delhi vashikaran baba near me online vas...Amil Baba Dawood bangali
Contact with Dawood Bhai Just call on +92322-6382012 and we'll help you. We'll solve all your problems within 12 to 24 hours and with 101% guarantee and with astrology systematic. If you want to take any personal or professional advice then also you can call us on +92322-6382012 , ONLINE LOVE PROBLEM & Other all types of Daily Life Problem's.Then CALL or WHATSAPP us on +92322-6382012 and Get all these problems solutions here by Amil Baba DAWOOD BANGALI
#vashikaranspecialist #astrologer #palmistry #amliyaat #taweez #manpasandshadi #horoscope #spiritual #lovelife #lovespell #marriagespell#aamilbabainpakistan #amilbabainkarachi #powerfullblackmagicspell #kalajadumantarspecialist #realamilbaba #AmilbabainPakistan #astrologerincanada #astrologerindubai #lovespellsmaster #kalajaduspecialist #lovespellsthatwork #aamilbabainlahore#blackmagicformarriage #aamilbaba #kalajadu #kalailam #taweez #wazifaexpert #jadumantar #vashikaranspecialist #astrologer #palmistry #amliyaat #taweez #manpasandshadi #horoscope #spiritual #lovelife #lovespell #marriagespell#aamilbabainpakistan #amilbabainkarachi #powerfullblackmagicspell #kalajadumantarspecialist #realamilbaba #AmilbabainPakistan #astrologerincanada #astrologerindubai #lovespellsmaster #kalajaduspecialist #lovespellsthatwork #aamilbabainlahore #blackmagicforlove #blackmagicformarriage #aamilbaba #kalajadu #kalailam #taweez #wazifaexpert #jadumantar #vashikaranspecialist #astrologer #palmistry #amliyaat #taweez #manpasandshadi #horoscope #spiritual #lovelife #lovespell #marriagespell#aamilbabainpakistan #amilbabainkarachi #powerfullblackmagicspell #kalajadumantarspecialist #realamilbaba #AmilbabainPakistan #astrologerincanada #astrologerindubai #lovespellsmaster #kalajaduspecialist #lovespellsthatwork #aamilbabainlahore #Amilbabainuk #amilbabainspain #amilbabaindubai #Amilbabainnorway #amilbabainkrachi #amilbabainlahore #amilbabaingujranwalan #amilbabainislamabad
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
Learn about the cost savings, reduced environmental impact, and minimal disruption associated with trenchless technology. Discover detailed explanations of popular techniques such as pipe bursting, cured-in-place pipe (CIPP) lining, and directional drilling. Understand how these methods can be applied to various types of infrastructure, from residential plumbing to large-scale municipal systems.
Ideal for homeowners, contractors, engineers, and anyone interested in modern plumbing solutions, this guide provides valuable insights into why trenchless pipe repair is becoming the preferred choice for pipe rehabilitation. Stay informed about the latest advancements and best practices in the field.
CFD Simulation of By-pass Flow in a HRSG module by R&R Consult.pptxR&R Consult
CFD analysis is incredibly effective at solving mysteries and improving the performance of complex systems!
Here's a great example: At a large natural gas-fired power plant, where they use waste heat to generate steam and energy, they were puzzled that their boiler wasn't producing as much steam as expected.
R&R and Tetra Engineering Group Inc. were asked to solve the issue with reduced steam production.
An inspection had shown that a significant amount of hot flue gas was bypassing the boiler tubes, where the heat was supposed to be transferred.
R&R Consult conducted a CFD analysis, which revealed that 6.3% of the flue gas was bypassing the boiler tubes without transferring heat. The analysis also showed that the flue gas was instead being directed along the sides of the boiler and between the modules that were supposed to capture the heat. This was the cause of the reduced performance.
Based on our results, Tetra Engineering installed covering plates to reduce the bypass flow. This improved the boiler's performance and increased electricity production.
It is always satisfying when we can help solve complex challenges like this. Do your systems also need a check-up or optimization? Give us a call!
Work done in cooperation with James Malloy and David Moelling from Tetra Engineering.
More examples of our work https://www.r-r-consult.dk/en/cases-en/
Student information management system project report ii.pdfKamal Acharya
Our project explains about the student management. This project mainly explains the various actions related to student details. This project shows some ease in adding, editing and deleting the student details. It also provides a less time consuming process for viewing, adding, editing and deleting the marks of the students.
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
2. 3.1 Analysis of Solid particles
3.1.1 Characterization of solid particles
• Individual solid particles are characterized by their
size, shape and density.
• Particles of homogeneous solids have the same
density as the bulky material.
• Particles obtained by breaking up a composite solid
(e.g metal-bearing ore) have various densities usually
different from the density of the bulk material.
Dr. Bilha Eshton
3. Why measure particle properties?
1. Better control of product quality (cement, urea,
cosmetics etc.)
In an increasingly competitive global economy, better
control of product quality delivers real economic benefits
such as:
• ability to charge a higher premium for your product;
• reduce customer rejection rates.
Dr. Bilha Eshton
4. 2. Better understanding of products, ingredients
and processes
• improve product performance.
• troubleshoot manufacturing and supply issues
• optimize the efficiency of manufacturing processes
• increase output or improve yield
• stay ahead of the competition
3. Designing of equipment for different
operations
• For example equipment for crushing, grinding,
conveying, separation, storage etc.
Dr. Bilha Eshton
5. Which particle properties are important to
measure?
From a manufacturing and development perspective,
some of the most important physical properties to
measure are:
• particle size
• particle shape
• surface properties
• mechanical properties
• Microstructure
• Density
Dr. Bilha Eshton
6. 3.1.2 Particle shape
• The shape of individual particles is best expressed in terms of
sphericity (Φs) which is independent of particle size.
• For spherical particle of diameter Dp, Φs=1; for non-spherical
particle, the sphericity is defined by this relation:
Φ𝑠 ≡
6𝑉
𝑝
𝐷𝑝𝑠𝑝
… … … … … … … … … … … … (3.1)
• Where:
Dp = equivalent or nominal diameter of particle
sp = surface area of one particle
Vp = volume of one particle
Dr. Bilha Eshton
7. • The equivalent diameter is sometimes defined as
the diameter of a sphere of equal volume.
• For fine particles, Dp is usually taken to be the
nominal size based on screen analysis or
microscopic analysis.
• The surface area is found from adsorption
measurements or from the pressure drop in a
bed of particles.
• For many crushed materials, Sphericity is
between 0.6 and 0.8. For particles rounded by
abrasion, their sphericity may be as high as 0.95.
Dr. Bilha Eshton
8. For many crushed materials, Φs is between 0.6 and 0.8 as
shown in the Table below.
Dr. Bilha Eshton
Table 28.1 in Unit operations of
Chemical Eng. Vol 5
10. 3.1.3 Particle Size
• The most important physical property of particulate
samples is particle size.
• Particle size measurement is routinely carried out across
a wide range of industries and is often a critical
parameter in the manufacturing of many products.
• Particle size has a direct influence on material
properties such as:
– Reactivity or dissolution rate e.g. catalysts, tablets
Dr. Bilha Eshton
11. – Stability in suspension e.g. sediments, paints
– Efficacy of delivery e.g. asthma inhalers
– Texture and feel e.g. food ingredients
– Appearance e.g. powder coatings and inks
– Flowability and handling e.g. granules
– Viscosity e.g. nasal sprays
– Packing density and porosity e.g. ceramics.
Dr. Bilha Eshton
12. • In general particle diameters may be specified for any
equi-dimensional particle. However, most particles
used in industries are not equi-dimensional i.e. that
are longer in one direction than in others.
• In order to simplify the measurement process, it is
often convenient to define the particle size using the
concept of equivalent spheres.
• In this case the particle size is defined by the diameter
of an equivalent sphere having the same property as
the actual particle such as volume or mass for
example.
Dr. Bilha Eshton
13. • The equivalent sphere concept works very well for
regular shaped particles.
• However, it may not always be appropriate for
irregular shaped particles, such as needles or plates,
where the size in at least one dimension can differ
significantly from that of the other dimensions.
• Such particles are often characterized by the second
longest major dimension. For example needle like
particles, Dp would refer to the thickness of the
particle, not their length.
Dr. Bilha Eshton
14. Some common diameters used in microscope analysis
are statistical diameters such as:
• Martin’s diameter (length of the line which bisects
the particle),
• Feret’s diameter (distance between two tangents on
opposite sides of the particle) and
• shear diameter (particle width obtained using an
image shearing device).
• Some of these diameters are described in the next
slide
Dr. Bilha Eshton
16. • If a sieve is used to measure the particle size, an
equivalent sphere diameter will be obtained. This is
the diameter of a sphere passing through the same
sieve aperture.
• If sedimentation technique is used to measure
particle size then, the particle diameter is expressed
as the diameter of a sphere having the same
sedimentation velocity under the same conditions.
• Other examples of the properties of particles
measured and the resulting equivalent sphere
diameters are given in the next slide.
Dr. Bilha Eshton
18. UNITS FOR PARTICLE SIZE
Depending on convention, particle sizes are expressed in
different units depending on the size range involved.
• Coarse particles: inches or millimeters,
• very fine particles: micrometers or nanometers.
• Ultrafine particles: surface area per unit mass, i.e.
m2/g
Dr. Bilha Eshton
19. 3.1.4 Mixed particle sizes and size analysis
• In a sample of uniform particles of diameter Dp the total
volume of the particles is:
𝑉
𝑝 =
𝑚
𝜌𝑝
……………………………………………………..3.2
Where: m = total mass of the sample
ρp = density of particles
• The number of particles in a sample is then:
𝑁 =
𝑚
𝜌𝑝𝑉𝑝
……………………………………………………….3.3
• Total surface area of the particles is:
𝐴 = 𝑁𝑠𝑝 =
6𝑚
Φ𝑠𝜌𝑝𝐷𝑝
………………………………….3.4
Dr. Bilha Eshton
20. Particle Size Analysis
• To analyse the particle size for a mixtures of particles
having various sizes and densities, the mixture is sorted
into fractions, each of constant density and approximately
constant size.
• Each fraction can then be weighed, or the individual
particles in can be counted or measured by any method.
Equations 3.3 and 3.4 can then be applied to each fraction.
• Information from such particle size analysis is tabulated to
show the mass or number fraction in each size increment
as a function of the average particle size (size range).
Dr. Bilha Eshton
21. • An analysis tabulated based on size increment as a
function of average particle size is called a
differential analysis.
• An analysis which is obtained by adding,
consecutively, the individual increments, starting
with that containing smallest particles is called the
cumulative analysis.
• Both method are shown in a Figure (next slide)
Dr. Bilha Eshton
25. 3.1.5 Specific Surface Area of Mixture
• If the particle density ρp and sphericity Φs are known, the
surface area of the particles in each fraction may be
calculated from eqn. 3.4 and the results for all fractions
added to give Aw, the specific surface area (i.e. the total
surface area per unit mass of particles).
• If ρp and Φs are constants, Aw is given by:
Dr. Bilha Eshton
26. • Hence, Aw ……………………………………3.5
Where subscript = individual increments
xi = mass fraction in a given increment
n = number of increments
ഥ
𝐷𝑝𝑖 = Average particle diameter, taken
as arithmetic average of smallest and
largest particle diameters in
increment.
Dr. Bilha Eshton
27. 3.1.6 Average Particle Size
The average particle size for a mixture of particles is defined by
the volume-surface mean diameter ഥ
𝐷𝑠 which is related to the
specific surface area Aw.
It is defined as:
ഥ
𝐷s ≡
6
Φ𝑠𝐴𝑤𝜌𝑝
…………………………………3.6
Substituting Aw (eq. 3.5) gives:
………………………………………3.7
Dr. Bilha Eshton
28. • If the number of particles in each fraction Ni is known
instead of the mass fraction, ഥ
𝐷𝑠 , is given by:
…………………………………..3.8
• And the arithmetic mean diameter ഥ
𝐷𝑁 is calculated by:
………………………………..3.9
Where:
NT = the number of particles in the entire sample.
Dr. Bilha Eshton
29. • The mass mean diameter ഥ
𝐷𝑤 is calculated from:
………………………………..3.10
• Dividing the total volume of the sample by the
number of particles in the mixture gives the average
volume of a particle. The diameter of such a particle
is a volume mean diameter calculated from:
………………………………..3.11
Dr. Bilha Eshton
30. • For samples consisting of uniform particles these
average diameters are all the same.
• For mixtures containing particles of various sizes,
average diameters may differ from one another.
Dr. Bilha Eshton
31. 3.1.7 Number of Particles in a Mixture
• Equation 3.3 is used to calculate the number of particles in
fraction and Nw, the total population in one mass unit of
sample is obtained by summation over all the fractions.
• For a given particle shape, the volume of any particle is
proportional to cube of its diameter.
• i.e. 𝑉
𝑝 = 𝑎𝐷𝑝
3……….……………………………………..3.12
Where a is the volume shape factor.
From equation 3.3 assume a is independent of size, then:
……………………….……….3.13
Dr. Bilha Eshton
32. 3.1.8 Screen (sieve) Analysis and Standard
screen series
• Standard screens are used to measure the size (and
size distribution) of particles in the range between 3
and 0.0015 in. (76 mm and 38μm).
• Testing sieves are made of woven wire screens, the
mesh and dimensions (openings) of which are
carefully standardized.
• The openings are square and each screen is identified
in meshes per inch. e.g. 10 mesh, Dpi = 1/10 = 0.1 in.
Dr. Bilha Eshton
33. Mesh No. is the numbers
of opening per linear
inch.
• Area of opening in any screen = 2 times the
area of opening in next smaller screen.
• Mesh dimension of any screen = 1.41 times
Mesh dimension of next smaller screen.
Dr. Bilha Eshton
34. • The actual openings are however smaller than those
corresponding to the mesh number, because of
thickness of wire.
• The common screen series is the Tyler standard screen
series. The area of the openings in any one screen in
this series is exactly twice to that of the openings in
the next smaller screen.
• The ratio of the actual mesh dimension of any screen
to that of the next smaller screen is √2 =1.41.
Dr. Bilha Eshton
35. • For close sizing, intermediate screen are available, each of
which has a mesh dimension = 1.189 times that of next smaller
standard screen.
• Analysis using standard screen: Screens are arranged serially in
a stack, with the smallest mesh at the bottom and the largest at
the top. Materials are loaded at top and then shacked for a
period of time (e.g. 20 minutes).
• The particles retained of each screen are removed, weighed
and masses of individual screen increments are converted into
mass fraction of total sample.
• Any particle that passed the finest screen are caught in the pan
at the bottom of stack. Results of screen analysis are then
tabulated.
Dr. Bilha Eshton
36. Table 1. Tyler standard screen series (Appendix 20)
Dr. Bilha Eshton
39. A typical screen analysis is shown in Table 3 (next slide)
• First column: mesh size,
• second column: width of opening of screen,
• third column: mass fraction of total sample that is retained
on that screen xi (where i is the number starting from the
bottom of the stack),
• fourth column: averaged particle size Dpi (since the particle
on any screen are passed immediately by the screen ahead
of it, the averaged of these two screen are needed to specify
the averaged size in that increment).
• Fifth column: cumulative fraction smaller than Dpi.
Dr. Bilha Eshton
41. Example 1
The screen analysis shown in Table 3 applies to a
sample of crushed quartz. The density of particles is
2650 kg/m3 and the shape factor are a=2 and Φs =
0.571. For material between 4-mesh and 200-mesh in
particle size, calculate:
(a) Aw in square millimeters per gram and Nw in
particles per gram.
(b)ഥ
Dv, ഥ
Ds , ഥ
Dw and Ni for the 150/200- mesh increment.
(c) What fraction of the total number of particles is in
the 150/200- mesh increment?
Dr. Bilha Eshton
42. 3.2 SCREENING
• Screening is a method of separating particles
according to size alone by a semipermeable
membrane (or screening surface).
Dr. Bilha Eshton
43. • In screening, the solids are dropped on, or through a
screening surface.
• The under size or fines particles pass through the
screen openings; the oversize or tails do not.
• Material passed through a series of screens of
different sizes is separated into sized fractions, i.e.
fractions in which both the maximum and minimum
particle sizes are known.
• The final portions consist of particles of more uniform
size than those of the original mixture.
Dr. Bilha Eshton
44. The screening surface may consist of:
(i) woven-wire (ii) perforated plastic cloth
Dr. Bilha Eshton
(iii) grizzly bars and wedge wire sections
45. 3.2.1 Material balance over a screen
• Simple material balance can be written over a
screen which is useful in calculating the ratios
of feed, oversize and undersize from the
screen.
• Consider a feed which contains material A and
B to be separated.
• Let F, D and B be the mass flow rates of feed,
overflow and underflow, respectively.
Dr. Bilha Eshton
46. • and let xF, xD and xB be the mass fractions of
the material A in these three streams.
• The mass fractions of material B in the feed,
overflow and underflow are: 1-xF, 1-xD and 1-xB
respectively.
• Since the total material fed to the screen must
leave it either as underflow (B)or as overflow
(D), then:
Dr. Bilha Eshton
47. 𝐹 = 𝐷 + 𝐵……………………………………3.14
• The material A in the feed must also leave in
these two streams, then
𝐹𝑥𝐹=𝐷𝑥𝐷+𝐵𝑥𝐵…………………………….3.15
• Eliminating B from equations 3.14 and 3.15 gives
𝐷
𝐹
=
𝑥𝐹−𝑥𝐵
𝑥𝐷−𝑥𝐵
…………………………………………3.16
Dr. Bilha Eshton
48. Eliminating D from equation 3.15 gives:
𝑩
𝑭
=
𝒙𝑫−𝒙𝑭
𝒙𝑫−𝒙𝑩
…………………………………….3.17
Dr. Bilha Eshton
49. 3.2.2 Effectiveness of screens
• The effectiveness of a screen (or screen efficiency) is a
measure of the success of a screen in separating
materials A and B.
• If the screen functioned properly, all material A would
be in the overflow and all material B would be in the
underflow.
Dr. Bilha Eshton
50. • A common measure of screen effectiveness is the ratio
of oversize material A that is actually in the overflow
to the amount of A entering with the feed.
• Screen effectiveness with respect to material A is
therefore:
𝐸𝐴=
𝐷𝑥𝐷
𝐹𝑥𝐹
………………………………………...3.18
• Where EA is the screen effectiveness based on the
oversize.
Dr. Bilha Eshton
51. • Similarly an effectiveness based on the undersized
material is given by:
𝐸𝐵=
𝐵(1−𝑥𝐵)
𝐹(1−𝑥𝐹)
…………………………………………..3.19
A combined overall effectiveness can be defined as the
product of the two individuals and if the product is
denoted by E, we get:
……........…………………………….3.20
Dr. Bilha Eshton
52. • Substituting D/F and B/F from equation 3.16 and
3.17 into equation 3.20 gives
……….………….3.21
Example 2
A quartz mixture having the screen analysis shown in Table 3
(next slide) is screened through a standard 10-mesh screen.
The cumulative screen analysis of overflow and underflow are
given in the Table. Calculate the mass ratios of the overflow
and underflow to feed and the overall effectiveness of the
screen.
Dr. Bilha Eshton
54. 3.2.3 Capacity of screens
• The capacity of screens is measured by the mass of material
that can be fed per unit time to a unit area of the screen.
• The probability of passage of a particle through a screen
depends on the fraction of the total surface represented by
openings, on the ratio of the diameter of the particle to the
width of an opening in the screen, and on the number of
contacts between the particle and the screen surface.
• For a series of screens of different mesh sizes, the number of
openings per unit screen area is proportional to 1/Dpc
2 where
Dpc = width of screen opening.
Dr. Bilha Eshton
55. 3.3 Screening equipment
• Varieties of screen are available for different
purposes.
• In most screen particles drop through openings by
gravity.
• Some of screening equipment include: Stationary
screens and grizzlies; Gyrating screens; Vibrating
screens; Centrifugal sitter.
Dr. Bilha Eshton
56. 3.3.1 Grizzly Screens
• consist of a set of parallel bars held apart by spacers
at some predetermined opening.
• Bars are frequently made of manganese steel to
reduce wear.
• A grizzly is widely used before a primary crusher in
rock- or ore-crushing plants to remove the fines
before the ore or rock enters the crusher.
• It can be a stationary set of bars or a vibrating screen.
• Types: (i) stationary grizzly (ii) flat grizzlies (iii)
vibrating grizzlies.
Dr. Bilha Eshton
58. 3.3.2 Vibrating Screens
• They are used as standard practice when large
capacity and high efficiency are desired.
• The capacity, especially in the finer sizes, is so much
greater than that of any of the other screens that they
have practically replaced all other types when
efficiency of the screen is an important factor.
• Advantages include accuracy of sizing, increased
capacity per unit area, low maintenance cost per ton
of material handled, and a saving in installation space
and weight.
Dr. Bilha Eshton
59. • They are divided into two main classes:
(i) mechanically vibrated screens (ii) electrically vibrated screens
Dr. Bilha Eshton
60. 3.3.3 Gyrating Screens
• the machine gyrates in a circular motion at a near level
plane at low angles. The drive is an eccentric gear box
or eccentric weights
Dr. Bilha Eshton
61. On your own, read:
3.3.4 Revolving screens
3.3.5 Centrifugal sifters
END OF CHAPTER
Dr. Bilha Eshton