Report on Bulk Materials Handling Transfer Chute Design Analysis

This report delves into the critical aspects of bulk material handling and transfer chute design, focusing on the selection and evaluation of appropriate chute configurations for industrial applications. It begins by highlighting the importance of material handling in modern industries, emphasizing the significance of transfer chutes in ensuring efficient material flow, particularly for raw materials like iron ore. The report comprehensively examines the physical and mathematical properties of conveyed materials, including particle size, shape, bulk density, angle of repose, and friction coefficients, and their influence on chute design. Two primary chute designs, the rocky box and the hood and spoon chutes, are analyzed and compared based on operating conditions, material characteristics, and performance metrics. The report evaluates the suitability of each design for handling iron ore, considering factors such as throughput, bulk density, and potential for wear and tear. Ultimately, the report concludes that the rocky box transfer chute is the more suitable design for iron ore due to its ability to manage the material's properties effectively. The report also considers the significance of design conditions like steady flow, minimized dust generation, and wear and tear to ensure optimal performance.

BULK MATERIALS HANDLING AND TRANSPORTATION
TRANSFER CHUTE ASSIGNMENT
MATERIAL HANDLING
Material handling and transportation has become a vital part of modern economy.
Modern Industrial plants deals with raw materials like coal, iron ore, cement, coarse aggregates,
rubber, plastics and so on. In such cases the transfer arrangement has become very much
essential without which the productivity of the system lags. Conveyor belt transfer chutes are
more important in handling operations. The work is always a combination of ailments like
crushing, screening, separation, blending etc., An effective material handling process is very
much effective in reducing the labor in operations and increases the productivity of the
manufacturing process. The Material handling has become an identical part of today’s industries
and an enormous amount is used in this system.
The material to be transferred is thoroughly investigates for all its physical, chemical and
mechanical properties. Then to choose the appropriate nature of the conveyor and its chute
arrangement. Bulk materials like coal, iron ore, rocky minerals and aggregates are generally used
in transfer chute arrangements. This might also include granular and powdered materials like M-
Sand, gold dust, Saw dust and so on.
PHYSICAL PROPERTIES OF THE CONVEYED MATERIAL
PARTICLE SIZE AND SHAPE: The size of the particle and its lump to fine material ration
influences the burden surcharge angle of the material. The particle shape can also affect the
material flow and the wear and tear of the chute.
MAXIMUM LUMP SIZE: The presence of large lumps tends to often needs efficient crushers
to crush the lumps to fine particles. This in turn decides the type of crusher used and the type of
conveyor belt used.
BULK DENSITY: It is defined as the weight of the material per unit volume. Generally bulk
density is denoted by γ (includes the voids also). Bulk density is usually measured in tons/cubic
meter or pounds/cubic inch. The bulk density of the material at loose state without compaction is
known as the loose bulk density of the material. It can be determined by weighing samples of a
known volume at different time. The bulk densities of most ores vary due to the impurities
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present on it and its particulate size. Therefore, always a careful consideration of a reasonable
number of samples is needed.
SPECIFIC WEIGHT: The weight of the particles at completely dried condition is known as the
specific weight of the particle. The general temperature is around 100 to 105oC. The specific
weight of materials is very much essential to calculate the capacity of pneumatic and hydraulic
transfer chutes.
COEFFICIENT OF FRICTION: This is generally considered for material used in transfer like
steel, wood, concrete, rubber and so on. The friction coefficient determines the angle of
inclination of walls and the sides or chutes. Also in some cases it determines the maximum
inclination of certain conveyors.
ABRASIVITY: This is nature of bulk materials to wear and tear away with the surface. In other
words, The tendency of an object to reduce the relative motion on a surface in contact is known
as the abrasiveness of the material. The abrasiveness of the material depends on the hardness of
the material, surface of the conveyor, shape and size of the particles. Materials like bauxite, iron
ore, sand and carbon related materials are generally abrasive than other materials. (Minkin)
MATHEMATICAL PROPERTIES OF THE CONVEYED MATERIAL
ANGLE OF REPOSE: The angle between the surface of a pile formed under free fall of
particles through chute and the horizontal surface below is known as the angle of repose. This
says about the mobility of flowability of the material. The angle of repose is usually denoted by
ϕ. This is used as the base value for determining the burden surcharge angle.
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ANGLE OF SURCHARGE: The angle formed with the horizontal where the material is in rest
on a horizontal surface vibrating vertically is known as the angle of surcharge. This in turn
defines the flowable capacity of the material. The general angle of surcharge is 5 to 15o less than
the angle of repose (approx.).
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ANGLE OF DISCHARGE: The angle between the material on free fall and the conveyor belt
at the point of discharge is known as the angle of discharge. (Bharatwaj, 2012)
INTERNAL FRICTION ANGLE: Materials having low internal friction angles will have low
burden surcharge angles and are more likely to slump. In other words, Internal friction angle and
burden surcharge angles are proportional to each other. The internal friction angle can be
determined using the shear test.
SPECIFIC PROPERTIES: The properties like moisture content, stickiness, fragile nature,
toxicity, corrosiveness is known as the specific properties of the conveying machines. Effective
measures must be taken to neutralize this effect. Some of the properties are:
 Moisture Content: The amount of water in vapour or combined form which influences
the burden surcharge angle, slump of the material at the discharge end.
 Cohesion: The amount of interaction between two adjacent particles is known as
cohesion. This is based on the angle of repose since the material on the conveyor tends to
free fall.
 Temperature: Temperature of the material is to be considered during transfer of any
material. If the material temperature is greater than the ambient temperature, then
specifically treated heat resistant rubber must be used as the conveyor belt.
TYPES OF TRANSFER CHUTES
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Depending upon the materials used in Handling and transportation there are several types
of Chute designs. These chutes depend on characteristics of the material transferred using the
chute. Mainly these chute designs fall into 2 major categories. They are
ROCK BOX TRANSFER CHUTE
HOOD AND SPOON TRANSFER CHUTE
ROCKROCK BOX TRANSFER CHUTE
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A rock box transfer is an arrangement where the material is transferred into a large box
like arrangement with horizontal ledges at regular vertical intervals. The material then passes
through the ledge and finally reach the conveyor belt and is transferred to the next stage. A rock
box transfer chute is suitable for free-flowing rocky materials. For sticky and fine materials there
needs to be regular removal of materials from the corner of the ledges.
HOOD AND SPOON CHUTE
A hood and spoon chute are a minimalized design for fine and sticky materials where the
materials is transferred to the chute by a curved edge contouring at certain angle and thereby
increasing the flow of materials in the transfer chute. The transfer chute has an optimized design
with curved base so as to ensure no clogging or plugging of materials on the chute.
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OPERATING CONDITIONS
Operating conditions for the transfer chute are listed below;
 Material-Iron ore
 Throughput – 3000t/h
 Bulk Density – 2500kg/m3 (use default volume solid fraction of 0.6)
 Angle of repose of 25°-27°
 Conveyor velocities – 3.5 m/s (incoming and outgoing)
 Conveyor Belt Widths – 1.4m (incoming and outgoing)
 Delivery Conveyor Idler Troughing Angle - 30° (3-roll)
 Incoming Conveyor Inclination – 5°
 Delivery Conveyor Inclination at Discharge – 8.55°
 Outgoing Conveyor Inclination – 2°
 Iron Ore/Chute Wall Friction Angle – 27° (assume wall friction value of 0.5)
 Iron Ore/Conveyor Belt Wall Friction Angle – 35° (assume wall friction value of 0.7)
EVALUATION OF THE ROCKY BOX TRANSFER CHUTE
Upon considerations of the above operating conditions the following characteristics have
been observed.
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LARGEST MINERAL ORE: Iron ore is one of the largest minerals available in natural
form. The form is always a combination of other minerals such as aluminum, bauxite,
copper etc., accompanied with a small amount of mud, oxygen and carbon.
PROPERTIES AT THE PLANT: The Angle of repose and the angle at discharge
clearly states the need for micro ledges at the transfer chute for the iron ore.
The bulk density of the iron ore being relatively high with 2500kg/m3 and the conveyor
belt width of 1.4m it transports a large amount of ore over a throughput of 3000tonnes
per hour. The transfer must be clearly positioned at the point of discharge to avoid
plugging of materials
Iron ore being slightly sticky due to the its natural form with all the particles around it.
This can be minimized by actively calibrating the velocity and removal of plugging
materials at regular intervals. (Teng, 2016).
MANAGING THE THROUGHPUT: In this case the rocky box transfer chute being a
large open material transfer arrangement with micro ledges at regular vertical intervals is
one the best method.
The rocky box transfer chute has micro ledges at specific intervals and the throughput
manages constant discharge over a period of time.
EVALUATION OF HOOD AND SPOON TRANSFER CHUTE
 The hood and spoon arrangement are the conventional method designed to transfer
materials at constant discharge and also to prevent plugging or cladding of materials.
 The hood and spoon arrangement are suitable for the materials like M-Sand, powdered
particulates, cement and so on.
 The arrangement is mostly used in conventional materials.
 For iron ore the rapid free falling and the point of discharge makes it different.
 The hood and spoon transfer arrangement is likely to have wear for the bulk iron ore
material transportation for the bulk density of 2500kg/m3.
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COMPARISONCOMPARISON BETWEEN ROCKY BOX AND HOOD AND SPOON
TRANSFER CHUTE ARRANGMENTS
PHYSICAL COMPARISON OF CHUTE
BULK DENSITY
The Bulk density of the iron ore is relatively high, and the particle size relatively
varies over a range. For this kind of material, the rocky box as well as the spoon
and chute arrangement are also suitable since the material size is not uniform and
also the material may be plugging or free from other composites. But on careful
consideration of the discharge and the particle size the rocky box chute with the
micro ledges at specific intervals becomes an active choice.
SIZE OF PARTICLES
The particulate matters in iron ore varies from mm to several centimeters. This
makes it difficult for transportation using hood and spoon transfer chute
arrangements. The material under free fall can create a superimposed velocity on
the underlying material and can create an ease of flow.
WEAR AND TEAR
The wear and tear of the conveyor belt is very vital since it need periodical
replacement. The rocky box chute has micro ledges at equal intervals and so the
free fall reduces the natural wear tear on the chute as well as the conveyor belt.
Whereas in the hood and spoon transfer chute the discharge velocity is transferred
to the conveyor belt and, so it adds the possibility of wear and tear in the chute
and conveyor. Since the iron ore has no assurance of smoothened edges the rocky
box transfer chute has become an ideal choice.
DESIGN OF THE TRANSFER CHUTE
An effective design is an active part of the transfer chute. The design must
undergo certain conditions such as the effective minimizing of the wear and tear,
effective free flow of particles, effective considerations of the material transferred
using the chute arrangement etc., (Chen, 2015).
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An effective design must satisfy the following conditions such as Prevent
plugging, Sufficient cross-sectional area, Control the stream, Minimize wear,
Minimize dust generation and Minimize particle attrition
RESULTS AND DISCUSSION
Discussing through the impacts of the material i.e., Iron Ore and the transfer chute
characteristics it is clearly stating that the Rocky Box Transfer chute will be the ideal design of
the transfer chute. The main conditions for Ideal selection of chute is listed below.
Steady flow – The steady flow of material under the conveyor is an important criterion.
In a rocky Box transfer chute, the steady flow is maintained by providing micro ledges
such that the discharge and surcharge are uniform over the time period. (Zhang, 2008).
Minimized dust generation- In rocky box transfer chute the dust generation is generally
high than in the case of hood and spoon transfer chute, but this can be minimized by
providing the agitation at the point of discharge.
Minimized wear and tear – The minimization in wear and tear is provided by the
presence of micro ledges at equal vertical intervals. This controls the gravity of ore under
free fall and reduces further wear and tear on the conveyor belt.(Sherry, 2013)
Velocity of the conveyor belt- Since the conveyor belt velocity is relatively low the free
fall due to gravity for the iron ore is very much efficient for such high amount
transportation.
Sufficient cross sectional area – The cross sectional area in the rocky box transfer chute
is good when compared with the one used in hood and spoon transfer chute.( Franc,
2009).
Through there are many advantages the rocky box transfer chute requires adequate
maintenance at regular intervals to increase the efficiency through active cleaning of plugging
materials in the micro ledges. (Mason, 2016).
Proper agitation with segregation in particle size along with the decrease in the velocity
of conveyor belt at discharge can increase the efficiency of the chute. Appropriate selection of
materials at distinguished selection factors may also increase the efficiency.
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REFERENCES:
Bharatwaj, R.,(2012), Using DEM to Solve Bulk Material Handling Problems. American
Institute of Chemical Engineers 2012 PP 54-58.
Chen, X,.(2015), International Journal of Multiphase flow, Vol-69, PP42-53.
Franc, K., & Mihael, R., (2009), DEM, FME Transactions Vol-37. PP 185-192
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Mason,. & Alex,.(2016), Improved Transfer chute design using DEM software predict
material flow behavious, Retrieved from http://eprints.usq.edu.au/id/eprint/31438
Michael, J., Stephen, R., & Bill. M. Design analysis of underground Mine Ore Process.
National institute of occupational safety and health.
Minkin,. Analysis of Transfer Stations of Belt Conveyors with Help of Discrete Element
Method (Dem) In the Mining Industry. International journal of transport and logistics.
ISSN-1451-107x.
Sherry, L., Kem, C., Kadavy, P., & Gregory, J (2013). Simplistic Design Methods for
Moderate-Sloped Stepped Chutes.
Teng, P., Yang, T., & Pfister, M., (2016). Studies of Two-Phase Flow at a Chute Aerator
with Experiments and CFD Modelling. Modelling and Simulation in Engineering Volume
2016.
Zhang, H., Liu, H., Zhang, D., & Wu, P., (2008), “Numerical simulation of aerated high
velocity flow downstream of an aerator,” Journal of Hydraulic Engineering, vol. 39, no. 12,
PP 1302–1308.
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