9. •It consists of a helicoid flight (helix rolled from flat steel
bar) or a sectional flight (individual sections blanked and
formed into a helix from flat plate), mounted on a pipe or
shaft and turning in a trough. Power to convey must be
transmitted through the pipe or shaft and is limited by
the allowable size of this member. Screw-conveyor
capacities are generally limited to around 4.72 m3/min
(10,000 ft3/hr).
•Almost any degree of mixing can be achieved with
screw-conveyor flights cut, cut and folded, or replaced by
a series of paddles
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Screw Conveyors
11. • It can travel for miles at speeds up to 5.08 m/s
(1000 ft/min) and handle up to 4539 metric tons/h
(5000 tons/h). It can also operate over short
distances at speeds slow enough for manual
picking, with a capacity of only a few kilograms per
hour
•Belt-conveyor slopes are limited to a maximum of
about 30°, with those in the 18 to 20° range more
common. Direction changes can occur only in the
vertical plane of the belt path and must be carefully
designed as vertical curves or relatively flat bends
Belt Conveyors
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16. • Most vibrating conveyors are essentially directional-throw
units which consist of a spring-supported horizontal pan
vibrated by a direct connected eccentric arm, rotating
eccentric weights, an electromagnet, or a pneumatic or
hydraulic cylinder. The motion imparted to the material
particles may vary, but its purpose is to throw the material
upward and forward so that it will travel along the conveyor
path in a series of short hops. The capacity of directional-
throw vibrating conveyors is determined by the magnitude
of trough displacement, frequency of this displacement,
angle of throw, slope of trough and ability of the material to
receive and transmit through its mass the directional throw
of the trough
Vibrating or Oscillating Conveyors
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18. • The conveying action of various designs of continuous-flow
conveyors varies with the type of conveying flight but
theoretically is not comparable with the action in a flight or drag
conveyor. Flights vary from solid surfaces to skeleton designs
• The continuous-flow conveyor is a totally enclosed unit which
has a relatively high capacity per unit of cross-sectional area and
can follow an irregular path in a single plane. These features
make it extremely versatile.
• The capacity of the continuous-flow conveyor is dependent on
the particular design being considered. Limiting speeds are
subject to considerable controversy. It is advisable to follow the
manufacturer’s recommendations closely for best conveyor
service.
Continuous-Flow Conveyors
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1. Flight conveyors: These devices are available in an almost
infinite variety. Most flight-conveyor applications are open
designs for rough conveying operations, but some are built
with totally enclosed easing
2. Apron conveyors: Probably the most common chain
conveyors, these are available in a wide variety of designs
for both horizontal and inclined travel. Their main
application is the feeding of material at controlled rates,
with lump sizes that are large enough to minimize dribble.
The typical design is a series of pans mounted between two
strands of roller chain, with pans overlapping to eliminate
dribble, and often equipped with end plates for deeper
loads. Pan design may vary according to material
requirements
Types of Continuous-Flow Conveyors
22. Pneumatic Conveyors
•One of the most important material-handling techniques in
the chemical industry is the movement of material
suspended in a stream of air over horizontal and vertical
distances ranging from a few to several hundred feet
•The capacity of a pneumatic-conveying system depends on
product bulk density (and particle size and shape to
some extent)
energy content of the conveying air over the entire
system
diameter of conveying line
equivalent length of conveying line.
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30. thinking beyond tomorrow 30
Storage Bin
• Storage vessel is considered as consisting of a bin and
a hopper
• A bin is the upper section of the vessel and has vertical
sides.
• The hopper, which has at least one sloping side, is the
section between the bin and the outlet of the vessel.
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•Mass Flow
All the material in the vessel moves whenever any is
withdrawn
•Funnel Flow
Only a portion of the material flows when any
material is withdrawn
Types of Storage Bin
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• Particles segregate, but remit on
discharge
• Powders de-aerate and do not flood
when the system discharges
• Flow is uniform
• Density of flow is constant
• Level indicators work reliably
• Product does not remain in dead
zones, where degradation can occur
• Bin can be designed to yield non-
segregating storage, or to function as
a blender
• Particles segregate and remain
segregated
• First portion in is last one out
• Product can remain in dead zones
until complete cleanout of the
system
• Product tends to bridge or arch,
and then to rat-hole when
discharging
• Flow is erratic
• Density can vary
• Level indicators must be placed in
critical positions so they will work
properly
• Bins perform satisfactorily with
free-flowing, large-particle solids
Mass-flow bins Funnel-flow bins
Principal Characteristics
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Gates
• Gates are used to control flow from bins, hoppers, and
processing equipment to feeders or directly to conveyors
Types
Hand slide gate
Rack-and-pinion gate
Lever-operated quadrant gate
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Hoppers
• Vibrating Hoppers : They are used to enlarge the
storage-bin opening and to cause flow by breaking up
material bridges
•Types
The gyrating kind: in which vibration is applied
perpendicularly to the flow channel
The whirlpool type: which by providing a combined
twist and lift to the material, causes bridging to break
35. Feeders
•Used to assist in bin unloading and in producing uniform
feed
•Types
Screw feeders: variable pitch screw to produce a
uniform draw of material across the entire hopper
opening
Belt or apron feeders: The capacities of these
feeders can be increased by tapering the outlet in the
horizontal and vertical planes
Vibratory feeders: provide uniform flow along a slot
opening of limited length. Distance between the
feeder pan and the hopper is increased in the feed
direction. Slot length is limited by the motion of the
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Star feeders: Star feeders with a collecting-screw
conveyor provide highly uniform withdrawal along a
slot opening. A vertical section of at least one outlet
width should be added above the feeder to ensure
uniform withdrawal across the opening
Screw feeders Vibratory feeder.
Star feeder
37. Feeder selection on the basis of the physical
characteristics of the material to be handled
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40. thinking beyond tomorrow 40
Crushing and Grinding
• Crushing or grinding is sometimes required to reduce the
particle size. The particle size should be reduced no more
than is required for homogeneity and ready attack by
reagents
•Types
Jaw crusher
Gyratory crushers
Roll crushers
Pan crushers
Jaw crusher
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Screening
• Separation of a mixture of various sizes of grains into
two or more portions by means of a screening surface,
the screening surface acting as a multiple go-no-go
gauge and the final portions consisting of grains of
more uniform size than those of the original mixture.
• The screening surface consist of woven-wire, silk, or
plastic cloth, perforated or punched plate, grizzly bars,
or wedge wire sections.
46. •Mesh and Space Cloth: which is the number of
openings per linear inch counting from the center of
any wire to a point exactly 25.4 mm (1 in) distant, or
by an opening specified in inches or millimeters,
which is understood to be the clear opening or space
between the wires. Mesh is generally favored for
cloth 2 mesh and finer and clear opening for space
cloth of 12.7-mm (1⁄₂-in) opening and coarser
•Aperture :Aperture, or screen-size opening, is the
minimum clear space between the edges of the
opening in the screening surface and is usually given
in inches or millimeters
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51. Particle-Size Distribution
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•Sieve Scale :A sieve scale is a series of testing sieves
having opening in a fixed succession
•In Tyler Standard sieve scale the widths of the
successive openings have a constant ratio of the
square root of 2, or 1.414, while the areas of the
successive openings have a constant ratio of 2
openings in a fixed succession
•Testing Sieves
•U.S. Sieve Series
•International test sieve series : It recommended for
adoption as an international standard 19
52. The Rotary Dryer
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•Rotating cylindrical dryers are suited for free-flowing
granular materials that require drying times of the
long period. Materials that tend to agglomerate
because of wetness may be preconditioned by mixing
with recycled dry product.
•consists of a cylindrical shell into which the wet
material is charged at one end and dry material
leaves at the other end. Drying is accomplished by
contact with hot gases in parallel or countercurrent
flow or with heat
55. • The two most useful classifications are based on
The method of transferring heat to the wet
solids
The handling characteristics and physical
properties of the wet material
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The Rotary Dryer
57. Direct Dryers
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1.Direct contacting of hot gases with the solids is employed for
solids heating and vapor removal.
2.Drying temperatures may range up to 1000 K, the limiting
temperature for most common structural metals. At the higher
temperatures, radiation becomes an important heat-transfer
mechanism.
3.At gas temperatures below the boiling point, the vapor content
of gas influences the rate of drying and the final moisture
content of the solid. With gas temperatures above the boiling
point throughout, the vapor content of the gas has only a slight
retarding effect on the drying rate and final moisture content.
Thus, superheated vapors of the liquid being removed can be
used for drying.
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4.For low-temperature drying, dehumidification of the
drying air may be required when atmospheric
humidity are excessively high.
5.A direct dryer consumes more fuel per pound of
water evaporated, the lower the final moisture
content.
6.Efficiency increases with an increase in the inlet-gas
temperature for a constant exhaust temperature.
7.Because large amounts of gas are required to supply
all the heat for drying, dust-recovery equipment may
be very large and expensive when drying very small
particles.
Direct Dryers
59. Indirect Dryers
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These differ from direct dryers with respect to heat transfer
and vapor removal:
1.Heat is transferred to the wet material by conduction
through a solid retaining wall, usually metallic.
2.Surface temperatures may range from below freezing in
the case of freeze dryers to above 800 K in the case of
indirect dryers heated by combustion products.
3.Indirect dryers are suited to drying under reduced
pressures and inert atmospheres to permit the recovery
of solvents and to prevent the occurrence of explosive
mixtures or the oxidation of easily decomposed
materials.
60. Indirect Dryers
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4. Indirect dryers using condensing fluids as the heating
medium are generally economical from the
standpoint of heat consumption, since they furnish
heat only in accordance with the demand made by
the material being dried.
5. Dust recovery and dusty materials can be handled
more satisfactorily in indirect dryers than in direct
dryers.
61. Elevator
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Bucket Elevators
Spaced-bucket centrifugal- discharge elevators
Spaced-bucket positive-discharge elevators
Continuous-bucket elevators
Super capacity continuous-bucket elevators
Bucket elevators are the simplest and most
dependable units for making vertical lifts. They are
available in a wide range of capacities and may operate
entirely in the open or be totally enclosed. Main
variations in quality are in casing thickness, bucket
thickness, belt or chain quality, and drive equipment.
65. Silo
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A silo is a structure for storing bulk materials. Silos
are used in agriculture to store grain or fermented
feed known as silage. Silos are more commonly used
for bulk storage of grain, coal, cement, carbon black,
wood chips, food products and sawdust. Three types
of silos are in widespread use today - Tower silos,
Bunker silos and Bag silos.
68. Granulation
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Particle size terminology is industry specific. In the
following discussion, particle size enlargement in
tumbling, mixer and fluidized bed granulators is
referred to as granulation. Granulation includes
pelletization or balling as used in the iron-ore industry,
but does not include the breakdown of compacts as
used in some tableting industries. The term pelleting
or pelletization will be used for extrusion processes
only
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Couplings
1.API-671 - Special purpose couplings.
Belt conveyors
1.CEMA - Conveyor equipment
manufacturers association.
2.IS-11592 - Code of practice for selection
and design of belt conveyors.
3.IS-1891 - Specification for rubber
conveyor and elevator belting.
4.IS-8531 - Pulleys for belt conveyors.
5.IS-8591 - Flat belt conveyor.
6.IS-8598 - Idlers and idler sets for belt
conveyors.
APPLICABLE STANDARDS/CODES
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IS-7155 part 3 - Code of recommended
practice for conveyor safety –belt
conveyors and feeders.
IS-4776 part 1 - Troughed belt conveyors
for surface installation.
IS-4776 part 2 - Troughed belt conveyors
for underground installation.
IS-7465 - Portable and mobile
troughed belt conveyors
IS-9295 - Steel tubes for idlers for
troughed belt conveyors.
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Bucket elevator
1. IS-1891 part 1 - Specification for rubber
conveyor and elevator belting –
general purpose belting
2. IS-4240 - Glossary of conveyor terms &
definitions
3. IS-6832 - Fixing screws and fixing washers
for buckets for bucket elevators.
4. IS-6833 - Specification for buckets for
bucket elevator.
5. IS-6834 - Specification for conveyor
chains, chain wheels and attachments.
Part 1 - Chain.
Part 2 - Chain wheel.
Part 3 - Attachments.
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IS-6930 - Dimensions for
fixing arrangements for bucket
for bucket elevators.
IS-7054 - Casing for bucket elevator.
IS-7167 - Code for selection and use
of bucket elevators.
IS-10131 - Round steel link chair
(electric butt welded) for bucket
elevators.
