Quá trình đồng nhất liệu trong silo và hoạt động của chúng

A Survey on Homogenizing and Blending
Silos and their Operation

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© Holcim Group Support Ltd

CMC APAC 2009


Raw Meal Beneficiation

Learning Objectives

 Three major concepts in raw meal blending / homogenisation

 Basic concepts for kiln dust handling

 Kiln feed concepts

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3 Silo Concepts for Raw Meal Beneficiation
Classification according to the kind of the working principle applied :
Multi-Pack gravity systems

Air-fluidized systems
Homogenising

silo

storage
silo

 Air-fluidized systems  Aerated gravity

following the
concept of the fully
agitated batch mixer
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systems
following the concept
of a continuous
blender.

 Multi-pack gravity

systems following the
concept of a continuous
blender.
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Homogenizing Silo System
Batch type,
two store
arrangement

homogenizing silo

storage silo

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Homogenizing Silo System

Aeration System

Aeration
air supply
Lighter material rises in
homogenizing columns

Aeration
quadrant

Blending
air supply

Air cycling
valve

Blending
quadrant
Denser material
moves downward

Aeration
air supply

Homogenizing
air supply

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Homogenizing Silo System

Operation

Performance Diagram of Batch Type Homogenizing Silo
200

S [ Ca O ]

100
2.5
2.0

1.5

Start

1.0
0.5
0.4
0.3

Target

0.1

[ min ]
180

160

140 120 100

80

60

40

20

0

Required homogenizing time
[ kWh/t]

0.3

0.2

0.1

0.0

Spec. energy consumption
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concentration inlet

Homogenizing Silo System

Blending Efficiency

Silo inlet fluctuations

concentration outlet

time

Outlet fluctuations with a batch type homogenizing silo
goal mean
value

time of
one batch
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quality step
between
batches
time
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Homogenizing Silo System

Pros & Cons

 Most efficient raw meal homogenizing system
 Beneficiation potential 10:1

 High energy consumer
 Application limited to about 2000t vessels,

thus sufficient for production lines up to 3000t/d
 High investment for new installations

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Continuous Blending Silos Design concepts

1

8



Spider on top of silo for meal
distribution



Inverted cone concept
 empty cone (IBAU; K-P)

5

4

2

7
3

 center chamber (CPT)


Extraction by pneumatic control
valve

6

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Continuous Blending Silos HGRS Silo Investigation


Material is flowing downwards to the silo outlet in
funnels of much smaller dimension than sector
dimensions



Mixing takes place at material surface by blending
material originating from different horizontal layers (i.e.
material that has been ground at different time)



Flow channels are located over the silo outlet

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Continuous Blending Silo Design
IBAU type blending silo

 No. of sectors:

>D

 Cone/wall distance:

<2m

 Max. air pad length:

< 2.5 m

 Aeration air pad width 200 mm
 Aerated bottom area: >35 %

2
6

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Continuous Blending Silos Operation

 Operate the silos at high filling levels

(> 75 %)

 Activate single sectors at a time rather

than two opposite sectors

 Sector activation sequence preventing

intersection of funnels at material
surface

 Min. aeration air rate > 1 m3/(m2*min)
 Aeration sequence time 5 - 12 min

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Continuous Blending Silo FLS-CF type blending silo

 Max. air pad length: < 2.5 m
 Aeration air pad width:

200 mm

1

8

5

4

2

7
3

6

 Aerated bottom area:

35 – 50 %
 Min. aeration air rate:

1 - 2 m3/min/m2
 Aeration sequence time:

!!!
strictly follow the operation
manual !!!
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13

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Continuous Blending Silos FLS Operation Mode

 No spider required on top of silo

for meal distribution

1

8

 Flat bottom concept with

5

4

2

7
3

6

multiple (7) outlets

 Product discharge at different

rates from the outlets creating
controlled declination of the
layers

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c o n c e n tr a tio n in le t

Continuous Blending Silos

Blending Efficiency

Silo inlet fluctuations

c o n c e n tr a tio n o u tle t

time

Outlet fluctuations with

continuous type blending silo
goal mean
value

range of residual
fluctuations

time

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Continuous blending silos can not blend long term
compositional fluctuations

Silo blending performance

5

1.6
short term fluctuations

long term fluctuations

5

20
16

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CMC APAC 2009


Caused by:
 Addition of kiln

lim e s a tu r a tio n

Continuous blending silos can hardly deal with peaks in
compositional fluctuation

SILO INLET

108
106
104
102
100
98

94
92

lim e s a tu r a tio n

feeder

110

96

dust into a
blending silo
 Starvation of a

112

0

10

20

30

40

50

60

40

50

60

104
102

SILO OUTLET

100
98
96
94
92

0

10

20

30

time [ h ]

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CMC APAC 2009


Continuous Blending Silos

Pros & Cons

 Applicable for wide capacity ranges (5’000 – 20’000t)
 Low energy consumer
 Limited beneficiation potential 5:1
 Decreasing beneficiation potential with increasing raw
meal uniformity ex raw mill

 Insufficient reduction of

- long term fluctuations
- peak and step type disturbances

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Multi-Pack Silo 7+1-Pack-Silo special application
 Subsequent filling of silo cells
 Simultaneous reclaim from all cells
 Separate chamber for kiln dust handling

 Suitable for very critical raw materials  segragation, Q controle
 Low - but fix blending efficiency depending on number of silo
 Limited beneficiation potential 3:1
 Higher Investment cost
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19
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Raw Meal Beneficiation

Learning Objectives

 Three major concepts in raw meal blending / homogenisation

 Basic concepts for kiln dust handling

 Kiln feed concepts

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CMC APAC 2009


Kiln Dust Handling

Problems

 Separation factor



Tendency of a raw meal to cause segregation problems

Indication for high deviation of kiln dust chemistry from raw
meal chemistry

Sf LS 

LS 32 m

or for existing plants

LS RawMeal

LSkiln dust
Sf 
LSkiln feed

Critical

Not Critical

Critical

Sf < 0.8

0.8 < Sf < 1.2

Sf > 1.2

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Kiln Dust Handling

Characteristics

Plant

LS
kiln feed

LS
recirc. kiln dust

0.8 < Sf < 1.2

AL

95.7

119.5

1.25

AP

93.4

110.4

1.18

AP

93.4

110.1

1.18

AT

93.2

88.6

0.95

EC

92.1

81.3

0.88

MI

93.9

97.4

1.04

OZ

93.1

93.9

1.01

PL

90.8

70.8

0.78

UV

90.2

81.3

0.90
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Kiln Dust Handling

Option 1

 Compound operation:

raw mix and kiln dust to blending silo

 Direct operation:

kiln dust to blending silo

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Kiln Dust Management
 Compound operation:

Option 2

raw mix and kiln dust to blending silo

Sf not critical
 compositional

 Direct operation:

kiln dust to kiln feed bin

step variations
between
compound and
direct kiln
operation periods.
 may become

excessive with
out-of-range meal
qualities (0.8 < SF
< 1.2)
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© Holcim Group Support Ltd

CMC APAC 2009


Raw Meal Beneficiation

Learning Objectives

 Knowledge of the three major concepts in raw meal

blending/homogenisation

 Knowledge of the basic concepts for kiln dust handling

 Knowledge of kiln feed concepts

25
© Holcim Group Support Ltd

CMC APAC 2009