Aucun titre de diapositive- Ventilation
- Moisture
Purpose:
· Removal of fine particles risk of coating
· Cooling of the material coating / gypsum dehydration
Usual ranges of ventilation:
Open circuit : 0.8 to 1.2 m/sec Open or closed circuit:
Closed circuit: 1.2 to 1.5 m/sec 0.3 to 0.45 Nm3/kg
Ventilation
Ventilation
Open circuit
Open or closed circuit
A high ventilation
can result in a transportation of uncrushed particles from Cpt 1 to Cpt 2
can have a bad influence on the material level in Cpt 1
is necessary if fresh feed is moist
In general, it is necessary:
. to limit to 20-25 m/sec at mill feed entrance . to limit to 15 - 25 m/sec in the diaphragms . to provide a feeding chute with air passage . to provide an isolation device at mill discharge
Ventilation
Limits
Inlet Chute
Influence of the moisture on the ginding efficiency
Moisture
Solutions to high moisture
- Dry the material
Water injection
coating
not too bad effect
extremely serious
TIME OF EXPOSURE (minutes)
Water injection
Cpt 1
If clinker temperature > 80° C at mill inlet ---> max 1 % H20 (on fresh feed)
The water has to be dropped on the fresh feed or at mill inlet
No spray, just drop
Cpt 2
The water has to be sprayed close to 2nd Cpt inlet
The water can be sprayed from intermediate or outlet diaphragm
A PID regulation and a security device has to be foreseen
Slegten grinding course
Water injection
AIR
WATER
MATERIAL
AIR
WATER
FEED
Water injection
Thermal balance
Water injection
Thermal balance
Basis
Cement temperature: 105° C
2900 kW x 0,85 x 860 Kcal/kW / 97000 kg cem = =
0,19 kcal / kg°C x 90°C = =
0,31 kcal / Nm3 °C x 26900 Nm3/h x 15°C / 97000 kg cem = =
1597 l/h x 15°C / 97000 kg cem = =
21,85 kcal/kg cem
0,19 kcal / kg°C x 105°C = =
0,31 kcal / Nm3 °C x 26900 Nm3/h x 100°C / 97000 kg cem = =
1597 l/h x [ 537 kcal/kg + 100 kcal/kg + 0,44 kcal/kg°C x(100°C - 100°C) ] / 97000 kg cem = =
1,45 “ “
19,95 “ “
8,60 “ “
10,49 “ “
40,49 “ “
Water injection
Thermal balance
FS3
FS2
FS1
BILTOTAL
(vers.2/97)
4/30/02
Company:
Schurovo
Plant:
Schurovo
Mill:
dia (m)
ép (mm)
CH1
CH2
1.6
60.5
4.2
86
Output:
97.0
0
at:
15
178
475
772
1070
0
776
0
776
0
776
48.5
776
537 Kcal
Cp air (Kcal/Nm3 °c)
0
0
0
(SD Case 2:)
dp mill inlet
(SD Case 4:)
dp mill inlet
300
mmH2O
Heat Bal. 1 known: - Air - T mill outlet unknown: - Water - T fines
Heat Bal. 2 known: - Air - Water unknown: - T mill outlet - T fines
Heat Bal. 3 known: - Air - T fines unknown: - T mill outlet - Water
Heat Bal. 4 known: - T mill outlet - Water unknown: - Air - T fines
Initial
&A
Thermal balance
Water injection
% of each component IN and OUT heat balance
according to mill Ø (30 kWh/t - 1,2 m/s - clinker 100°C)
1,8 2 2,2 2,4 2,6 2,8 3 3,2 3,4 3,6 3,8 4 4,2 4,4 4,6 4,8 5 5,2 5,4 5,6 5,8 6
Diameter (m)
Water requested in % according to mill Ø
for different air speeds - 30 kWh/t - clinker 100° C
Thermal balance
Water injection
1,8 2 2,2 2,4 2,6 2,8 3 3,2 3,4 3,6 3,8 4 4,2 4,4 4,6 4,8 5 5,2 5,4 5,6 5,8 6
Diameter (m)
Definition:
Agglomeration of fine particles (on lining and/or on grinding media) grinding efficiency decrease
Reasons:
* Overgrinding (often in O.C., fine cement grinding and limestone addition)
* Too high outlet temperature in Cpt 2 ( > 110 °C at mill outlet)
* Fresh feed moisture
- good separator
* Use grinding aids
* If coating is due to moisture, dry by hot clinker, hot rejects or hot gas
Coating
Rittinger
Purpose : fight coating
in theory, grinding efficiency (cm2/j) constant
in reality, not constant because of agglomeration negative effects
Grinding Aids
Grinding Aids
Function principles:
Coating : due to static electricity on the generated areas make them stick together
G.A.: contain components which neutralize cement grain superficial charges
decrease these electrostatic forces
Grinding Aids
Grinding Aids
Other advantages:
. Improve cement flow
. One can use finer ball charge . Easier cement transport to silos . Silo build up elimination
. Allow a higher amount of additional components other than clinker
. Improve product quality
* Improve cement strengths 1, 2 and 28 days
Way of use:
In general .01 % to .08% are added (250 gr/t)
Quantity (and efficiency) increase with Blaine fineness
Slegten grinding course
Thionvilloise (100 % laitier)
Thyssen (100 % laitier)
Sidmar (100 % laitier)
Atlantic (100 % laitier)
Surface spécifique Blaine
Surface spécifique Blaine
Consommation spécifique (kWh/t)
Consommation spécifique (kWh/t)
Slag Vs Clinker: Grindability
Properties of slag grinding:
- Higher wear (balls / liners)
Slag
Chart1
0
20
40
100
0
25
65
100
Chart2
20
40
100
24.74
57.25
86.25
Chart3
2250
2250
2250
2750
2750
2750
3250
3250
3250
3750
3750
3750
4250
4250
4250
4750
4750
4750
5250
5250
5250
20%
40%
100%
blaine
%
slag influence - increase of the spec.grinding energy vrs slag content and blaine
25
65
100
24.75
57.25
86.25
17.5
45
66.25
15
36.25
50
10
25
35
7.5
16.25
22.5
5
10
10
Sheet1
0
0
20
25
40
65
100
100
0
0
20
24.74
40
57.25
100
86.25
20%
40%
100%
2250
25
65
100
2750
24.75
57.25
86.25
3250
17.5
45
66.25
3750
15
36.25
50
4250
10
25
35
4750
7.5
16.25
22.5
5250
5
10
10
Sheet2
Sheet3
Limestone
Slegten grinding course
Limestone
Chart1
2500
2500
2500
2500
2500
3000
3000
3000
3000
3000
3500
3500
3500
3500
3500
4000
4000
4000
4000
4000
4250
4250
4250
4250
4250
blaine
kWh/t (mill shaft)
Influence of the pozzolana on the specific grinding energy Source Holderbank
22
19
15
12.5
24
31
25
21.5
18.3
33
40
33.3
27.5
23.8
44
50.5
41.3
35
31
58
58
48.6
40
35.5
70
Sheet1
blaine
2500
24
22
19
15
12.5
3000
33
31
25
21.5
18.3
3500
44
40
33.3
27.5
23.8
4000
58
50.5
41.3
35
31
4250
70
58
48.6
40
35.5
Sheet2
Sheet3
content and blaine
Source Holderbank
Basis
3
/h
cem
cem
cem
kg°C x(
fresh air:
18 980 m3/h150 mmWG
Process:97 t/h
500 mmWG100 mmWG250 mmWG
at 91°C
dp mill:200 mmWG
FRESH FEED:T/H:°C:%H2O: