Bin & Silos
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Design of Bins and Feeders please see this thread if you are process Engineer http://cementforums.com/community/cement-process-engineers/heat-balance- program-attached-my-personal-program-and/ after reading this topic you should know the following : ======================================= Knowledge of strengths and weaknesses of the three basic bin design concepts Funnel-Flow Bins/Silos - Mass-Flow Bins/Silos - Expanded-Flow Bins/silos § Knowledge of the expanding bin outlet concept § Knowledge of the design criteria for new mass-flow type feed bins § Knowledge of the options for conversion of a funnel-flow type feed bin to a mass-flow type ============================================================================== ========= The Raw Material Preparation Sequence
Transcript of Bin & Silos
Design of Bins and Feedersplease see this thread if you are process Engineer
http://cementforums.com/community/cement-process-engineers/heat-balance-program-
attached-my-personal-program-and/
after reading this topic you should know the following :
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Knowledge of strengths and weaknesses of the three
basic bin design concepts Funnel-Flow Bins/Silos - Mass-Flow Bins/Silos - Expanded-Flow
Bins/silos
§ Knowledge of the expanding bin outlet concept
§ Knowledge of the design criteria for new mass-flow type
feed bins
§ Knowledge of the options for conversion of a funnel-flow
type feed bin to a mass-flow type
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The Raw Material Preparation Sequence
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Bin/FeederSystems in Cement Production
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Problemswith Materials Storage in Bins/Silos
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Bin/Feeder Systems
. Flow patterns in bins
. Analysis for product flow in bins
. Characterization (testing) of a bulk solid flow behavior
. The concept of total outlet activation
. Design criteria for bin/feeder systems
. Measures for improving the flow pattern of existing bins
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Funnel-FlowBins/Silos:
TypicalBin Shapes
Funnel-FlowBins/Silos:
FlowSequence
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OperationProblems
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Concept Valuation
-first-in/last-out flow sequence- cannot be emptied completely (loss of life capacity!)-tends to erratic flow and inconsistent discharge rate-subject to flow stoppages (arching, rat-holing)- nopossibility to correct product segregation-non-flowing zones limiting life volume and favoringproductdegradation+maximized storage volume for a given headroom
+ lowinvestment
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Applications
§ when segregation is unimportant§ when product degradation is not likely to be a problem§ when feed rate consistency is nor of prime importance
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Mass-FlOW Bins/SilOs:
Typical Shapes
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Flow Sequence of Mass-Flow Bins/Silos :
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Concept Valuation
+ first-in/first-out flow sequence
+ total activation of the stored product, absence of non
flowing zones (no product deterioration)
+ consistent discharge rate
+ segregation is corrected while product is reclaimed
+ can be emptied completely (no loss of life capacity)
- limited storage volume for a given headroom
- relatively high investment per storage volume
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Applications of Mass Flow bins
when segregation is important
§ when product degradation is a problem
§ when feed rate consistency is of prime importance
e.g. for feed bins
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Typical Shape
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Concept Valuation Expanded-Flow Bins/silos
+ optimized storage volume for a given headroom
+ moderate investment per storage volume
+ consistent product flow out of the bin
+ partial correction of segregation while product reclaim
- first-in/last-out flow sequence favoring product
degradation
- dead zones favoring product degradation with time
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Applications Expanded-Flow Bins
when segregation is unimportant
§ when product degradation is not likely to be a problem
possible concept to improve the insufficient
flow pattern of a given bin
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Analysis for product flow in bins
Physical Properties of Bulk Materials
Size
Shape / Surface area
Surface texture (roughness, etc)
Porosity / Density
Chemical composition
Hardness
Melting point Grain size distribution
Internal friction
Bulk porosity / density
Compressive / tensile strength
Cohesion Elasticity Uniformity of mix Moisture level Tendency to segregation
Electrostatic charging
Wall friction
Tendency to fluidization
Gas permeability
Chemical / biological reactivity
Hygroscopicity
Particle adhesion,
packing and lump formation
Abrasiveness
(Auto)inflammability Explosibility
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Testing a Materials Flow Behavior (1)
The rotational shear tester
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Testing a Materials Flow Behavior (2)
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Flow Characteristics:Raw Coal
Moisture Content % H2O 7 – 10
Granulometry
§ Minus 5 mm fraction % Residue 95
§ Minus 5 mm fraction % Residue 95
Bulk Solid Strength Pa 5000 – 7000
Effective Angle of Friction deg 47 – 52
Angle of Internal Friction deg 37 – 45
Angles of Wall Friction
§ mild steel deg 27 – 30
§ stainless steel deg 25 – 28
§ UHMW-PE deg 25 – 28
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Bin Design Characteristics for Mass Flow of coal :
Type of Discharge Hopper
Conical type
Wedge type
Maximum Hopper Half Angles
§ mild steel deg
§ stainless steel deg
§ UHMW-PE deg
Bin Outlet Dimensions § shape
§ minimum width required § L / W ratio
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The concept of total outlet activation
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Variable shaft diameter of screw and
variable screw pitch
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Design criteria for bin/feeder systems
Do not abuse feed bins as storage silos, i.e.
,Never control feed rates directly out of large storage silos
卜 Selection of small feed bins
(sizing for less than 30 min of mill operation)
§ Never feed several mills out of a common feed bin
§ Design feed bins for mass-flow
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Þ i.e. consider worst case flow
characteristics of components
Þ select steep discharge hoppers
for flow promotion
Þ select wide outlets to prevent
arching
§ Select sufficiently wide feeders
Þ i.e. reclaim consistency is priority
selection criteria
§ Design bin/feeder interfaces for full
outlet activation
Þ i.e. expanding in direction of
material flow
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Measures for improving the flow pattern of existing bins
Design Criteria for Bin Modifications
Collect the bin’s design data:
§ material mild/stainless steel, liner
§ shape circular, square
§ dimensions diameter/width, height, hopper inclination
§ outlet circular, square, slotted
§ Investigate product flowability
§ In case of excessive hopper half angles § check possibility of a lining
§ check possibility of a bin insert
§ In case that obstructions to flow are a problem
§ check bin outlet/feeder dimensions § check design of bin/feeder interface § check the possibility
of discharge aid
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Outlet Activation by a live Bottom Feeder
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Geroldinger Oszillomat
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Jost type Roller Grate
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Louise type feeder
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Outlet Activation by Aeration
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Funnel-Flow versus Mass-Flow
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Methods of measurement of angle of repose
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Design of Bins and Feeders
