presentacion bulk solid handling

7/29/2019 Presentacion Bulk Solid Handling

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RodrigoGutierrez


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INTRODUCCION,

bulk materials are key operations in a great number and variety of

industries. Such industries include those associated with MINING,

MINERAL PROCESSING, chemical processing, agriculture, power

generation, food processing, manufacturing and pharmaceutical

The foundations of process and handling plant design lies in the

interpretation of these properties in relation to the particular

applications.

The design of bulk solids handling plant requires a knowledge of the

strength and flow properties of the bulk solids under operating.


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The latter conditions include loading and consolidation for

ns an aneous an ex en e me s orage as we asenvironmental factors such as temperature, moisture and

humidit .

There are now well established laboratory test procedures fory w


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DETERMINATION OF BULK SOLIDS FLOW PROPERTIES

Focusing specifically on bin, hopper and stockpile design, the

laboratory tests aim to duplicate field conditions and provide the

designer with such parameters as:

conditions for the range of moisture contents and, as relevant,

temperatures occurring in practice. The flow functions represent the

occurs during storage and flow.

ec ve ang e o n erna r c on e as a unc on o ma or

consolidation stress


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iii Static an le of internal friction t as a function of ma or

consolidation stress

different bin and chute wall materials and finishes.

.

(vi) Solids density.

(vii) Permeability of the solids as a function of major

consolidation stress.


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Jenike Type Direct Shear Tester


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THEORY AND BACKGROUND


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SHEAR TEST RESULTS (Preshear and Failure-Shear)


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INSTANTANEOUS YIELD LOCUS


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EXAMPLE: 3 POINTS FLOW FUNCTION


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INTERNAL FRICTION ANGLES


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CHARACTERISATION FOR HOPPER AND STOCKPILE DESIGN

The procedures for the design of handling plant, such as storage bins,gravity reclaim stockpiles, feeders and chutes are well established and

follow the four basic steps:

(i) Determination of the strength and flow properties of the bulk solids for

the worst likel flow conditions ex ected to occur in ractice.

(ii) Determination of the bin, stockpile, feeder or chute geometry to give

,

characteristics and to ensure that discharge is reliable and predictable

feeders and chutes under operating conditions.

(iv) Design and detailing of the handling plant including the structure and

equipment.


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MODES OF FLOW IN BINS


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COMMON BIN GEOMETRIES


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Jenike postulated that the major principal stress1 in the lower hopper part is proportional to

the distance, r, from the virtual hopper apex

ra a s ress e .

Princi al Stress at an osition in the ho er

A solution of the system of differential equations exists only for

specific combinations of parameters, , e, and x. Thus, only

for these conditions mass flow will occur. If the hopper wall is not

steep enough, no solution exists fulfilling the condition of bulk

solid moving along the hopper wall (mobilization of wall friction),and, thus, a stagnant zone will form (funnel flow).

x: angle of wall friction,


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In the case of conical hoppers, it is recommended that, as a safety precaution, the hopper half angle be, generally, 3o less

than the limiting value.


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MASS FLOW DESIGN DETERMINATION OF MINIMUM OUTLET

Flow Function


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FLOW FACTOR


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CRITICAL ARCHING DIMENSION


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FUNEL FLOW DESIGN

FUNEL FLOW DESIGN


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FUNEL FLOW DESIGN

Lower Bound


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Upper Bound


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The computation of draw-down hD and live capacity involves the following steps:

(a) Determination of the relationship between the rathole diameter Df versuseffective head of solids hf. This determination is derived entirely from the flow

properties of the bulk solid without reference to a particular bin or stockpile

geometry. Usually Df versus hf is expressed in graphical form.

(b) Using the information in (a), the relationship between the rathole dimension Dfan raw- own can e o a ne or a par cu ar n or s oc p e geome ry.

Again, graphical representation is usually used. With this information, the

dimensions of the outlet, or, in the case of expanded flow, the dimensions of the

- - ,

selected.

- ,

shape of the rathole is estimated and this information is used in conjunction with

the Df versus hf relationship of (b) to determine the actual draw-down (d) The

after draw-down has occurred.


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Funnel Flow Design


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Funnel Flow Design

of the rathole diameter have to be determined. The bulk solid is assumed to exhibit no timeconsolidation. The diameter of the silo is D = 3 m, the maximum filling level for filling conditions, i.e.,

before material is discharged, is hf= 6 m .


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Lower Bound

Assuming lin = 30, f(i= lin = 30) = 2.4

Flow factorffp = 1.38. Since ffp should not besmaller than 1.7, it follows ffp = 1.7.

Upper Bound


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Filling height, hf= 6 m;

Ratio of cross-section to perimeter,

A/U= D/4 = 0.75 m.

Wall friction angle, x= 25,

maximum bulk density, b = 980 kg/m3,

K = 0.5

, . .

BIN WALL LOADS


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Pressures Acting in Mass-Flow Bins

Stresses in vertical channels (Janssens approach)


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( pp )


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Hopper Pressures - Flow Case


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presentacion bulk solid handling

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