Mill Material Balance
12.2
THE PROJECTION PROGRAM
It was mentioned that the use of the Projection Program or the Planning Program of a complete calculation for mill material balance is best to make the projection of an optimal performance of a milling tandem. The program made through scientific calculation based upon the existing mill tandem and the quality of cane crushed obtaining adequate and reasonable values, which is then used for the operation targets of the sugar factory normally stated in the budgeting purposes; not just taken as average from the previously milling seasons. The program is in one file with w ith the Evaluation Program. The Projection Program also consists of 2 (two) sheets that are: Sheet-III, inputs for the Projection, and Sheet-IV, the result of the Projection. § §
12.2.1 Projection Data
All the inputs for the Projection must be typed in sheet-III, which is identical with sheet-I for the Evaluation inputs. Here all the data must also be typed replacing the blue letters in the red lined boxes only, first the name of the sugar factory, the tandem composition, operational year (crushing season), the period (usually bi-weekly) number or purpose of projection, etc. Then the technical data of the mill rollers in use, the projected mill rotation per hour based upon the drive nominal speed, the hydraulic pressure, the top angle, the shaft dimensions and so on (the same dimensions for the Evaluation Program is used here). M I L L M A T E R I A L B A L A N C E I N P U T F O R P R O J E C T I O N ( a v e r a g e o r t o t a l iz ize d o f d a t a a c h ie ie v e d ) A T T E N T I O N :
Ty p e i n t h e d a t a ( b l u e l e t t e r s ) i n t h e r e d l i n e d s q u a r e b o x e s o n l y .
S u g a r F a c t o r y
E X A M P L E
M ill ill Train Train
2 C C + 5 M I L L S
M i l li li ng ng Se Se a s o n ( y e a r )
1977
P e r io io d o f 1 5 m i l l in in g da da y s , n u m b e r
X
P e rio d d a t e s e v a l ua ua t e d u p t o I .
L a s t d a t e
M I L L R O L L ER S I N U S E ( d i m e n s i on i n m m )
M I L L NO: - - - - - - - - - - - - - - - >
I
II
III
IV
V
t op
1,052. 0
1, 073.0
1, 051.0
1,050. 0
1, 064.0
feed
1,050. 0
1, 069.0
1, 048.0
1,048. 0
1, 052.0
delivery
1,048. 0
1, 066.8
1, 040.0
1,040. 0
1, 048.0
t op
2 5 .0
2 5 .0
1 5 .0
1 5 .0
1 5 .0
feed
2 5 .0
2 5 .0
1 5 .0
1 5 .0
1 5 .0
delivery
2 5 .0
2 5 .0
1 5 .0
1 5 .0
1 5 .0
t op
1,002. 0
1, 023.0
1, 021.0
1,020. 0
1, 034.0
f e ed ed
O u t s i d e d ia m e t e r ( D o ) :
Gr G r o o v e c o r r e c t i o n ( k ) :
M e a n d ia m e t e r ( D k ) :
1,000. 0
1, 019.0
1, 018.0
1,018. 0
1, 022.0
d el e liv e r y
998.0
1, 016.8
1, 010.0
1,010. 0
1, 018.0
L
2,133
2,133
2, 133
2,133
2,133
M il l rolle r s p e e d Hy H y d r a u lic p r e s s u r e
n ph
270 180
270 190
270 200
270 210
270 220
H y d r a u lic ra m d ia .
d
330
330
330
330
330
T r a n s m i s s i o n f a c t o r
r
86
86
86
86
86
dp
420
420
420
420
420 4,220
L e n g t h o f s h e ll
M il l rolle r s h a f t d ia .
l
4,220
4,220
4, 220
4,220
T o p a n g le
M il l rolle r s h a f t l e n g t h
a
78
78
78
78
78
T o p r o l l e r l i f t
t
6.0
6.0
6. 0
6.0
6.0
- o n f e e d o p e n in g
tf
4.7
4.7
4. 7
4.7
4.7
- o n d e liv e r y o p e n i n g
td
4.7
4.7
4. 7
4.7
4.7
The Computer Program Program
XII-11
Mill Material Balance
Then further we have to fill in the projected capacity and the quality of cane together with the projection of mixed juice quantity and its Brix degree, the foam correction factor, imbibition water rate, etc. Finally simulation of Brix degrees for each juice extracted by the mills together with its Pol degrees. Ca n e :
crush ed, to tal
Q
4,800.0 TCD =
cr cr u s hi n g d u r at i o n
jg
24.00 hours
po pol
pt
10.32 %
br brix
bt
fi fiber
f
Mi M ixe d j uice:
gross
13.41 %
Purity =
Gn m
4,800.0 Tons =
2 0 0 ,0 0 0 k g/ g/ h r =
bn m
12.60 %, pol =
10.04 Purity =
dirt corr.
knm Gi
A pp pplied on:
1,581.3 Tons =
b a g as s e 1
0 % 30 %
ba ga ss e 4
6 5 ,8 8 7 ltr/hr =
2 0 5 . 0 0 % fibe r
3 2 .9 4 % c a n e
70 % 1.60000 kg/dm3
bn1/bt =
1.19
M I L L NO: ---------------> brix po p ol
7 9 . 6 8 %
0 %
ba ga ss e 3
Bx B x r a t i o j u i c e # 1 t o c a n e
1 0 0 . 0 0 % can e
1.00308
ba ga ss e 2
Av erag e value of fiber density
7 6 . 9 6 %
16.07 % can e
brix Im I m b ib iti on wate r, t ota l
J ui ce:
2 0 0 .0 0 TC TCH
bn pn
Last Last mill bagasse juice to fiber =
1 0 5 . 0 0 % ----->
I
II
III
IV
V
Unit
1 6 .0 2 1 2 .9 8
9 .82 7 .65
5.6 0 4.0 5
3 .1 0 2 .1 0
1 .90 1 .18
% %
± 100%
gnhs =
32.97 %
khar = PSHK =
97.44 %
1.05 %
During the simulation please observe the values underneath, which shall be met with the limits. J uice:
purity
HK
81.02
77.90
72.32
67.74
62.11
Decreasing from one to the following mills
ex e xtraction
En
53.42
66.12
65.89
66.23
60.72
Best > 60% (decreasing to the following mills)
kB
1.000
0.935
0.830
0.715
0.607
br brix distr. coeff.
Normal value Co C ompression ratio
K
Bagasse: no-void density
0 ,9 , 9 --1 1 ,1 ,1 0 ,8 ,8 --1 1 ,0 ,0 0 ,7 ,7 --0 0 ,9 ,9 0 ,6 ,6 --0 0 ,8 ,8 0 ,5 ,5 --0 0 ,7 ,7
3.24
3.08
3.01
da
1.1851
1.2015
1.2154
1.2232
1.2322 Increasing from one to the following mills
r
1.3501
1.3316
1.3164
1.3081
1.2985 Decreasing from one to the following mills
di ditto, normal
r'
1.3492
1.3380
1.3269
1.3158
1.2962
fi fiber content
kf
29.13
36.25
41.18
44.68
48.78
Increasing from one to the following mills
0.78
Increasing from one to the following mills
abso absorrp.a p.ability fa factor
fi fiber index
c
0.47
0.58
0.66
0.71
re red. fiber loading
q'
134.89
129.41
129.92
130.17
po pol
pa
8.19
4.75
2.90
1.72
2.55
Decreasing from one to the following mills
2.56
126.67 q' = 120-130 gr/dm2 - normal 0.94
q' = 130-140 gr/dm2 - Donnelly chute q' = 140-160 gr/dm2 - light pressure feeder
br brix
ba
11.33
7.51
5.27
3.74
2.58
d ry matter
zk
40.46
43.77
46.46
48.42
51.36
q' = 150-170 gr/dm2 - heavy pressure feeder
When the values match or lies between the limits, then the projection of mill material balance shown on the Projection sheet (sheet-IV, page 1 through page 3) for overall as well as the individual performance is final and good. Otherwise, simulation has to be redoing until all the values are relevant to the limits.
The Computer Program Program
XII-12
Mill Material Balance
12.2.2 The Simulation Steps
To be more clear and speeding up the simulation, the steps below are necessary to be followed during the data inputs: Step 1
Step descriptions Type in the file name.
Remarks First row, say: "Jat-2000" Meaning SF Jatiroto, milling season 2000, or "Jat00-XI"; means SF Jatiroto milling season 2000, period of 15-days, Nr. XI. File name max. 8 digits.
2
Type in the sugar factory name, the mill
Understood.
tandem composition, milling season year, period and the date of evaluation. 3
Type in the data of the mill rollers in
The outside diameter, groove correction,
use.
roller length, projected roller speed (rph) based on 90-95% from the prime mover nominal speed, top roller lift and top angle of triangle formed by the rollers.
4
The cane and its quality.
- Total cane crushed or the milling capacity, in ton per day exclusively within 24 hours or 22 hours. - The projection of cane quality based on the pre-analysis and previous millings. millings.
5
The mixed juice.
- Define the quantity of mixed juice expected (e.g. = 100% cane). - Type in the average dirt correction factor of the mixed juice. - Simulate the brix value of mixed mixed juice to get the value of gnhs around: 30-36% for 5 mills tandem, and 34-42% for 4 mills tandem.
6
Imbibition water (Wi)
- Define the quantity, likely ± 200% fiber, to obtain approx. 100% ratio of juice to fiber in last mill bagasse (nss) and dry matter of
≥
50%. - Define in percentage on which bagasse of each application.
The Computer Program Program
XII-13
Mill Material Balance
7
Simulate the value of Brix degree for
To obtain the value of kB between:
each mill juice.
0.9-1.1 for mill 1 (average = 1.0)
#
0.8-1.0 for mill #2 0.7-0.9 for mill #3 #
0.6-0.8 for mill 4 #
0.5-0.7 for mill 5 During the simulation, observe and try to obtain the followings: a. Increasing value of no-void bagasse density (da), from the first to the last mill. b. Decreasing value of the absorption absorption ability factor (r), from the first to the last mill. c. The value of the the normal normal absorption ability factor (r'), especially for the last mill must be smaller than (r). d. Especially for the first first mill, simulate the juice Brix to obtain kB =1.0 =1.0 #
8
Simulate the value of Pol degree for each juice extracted by every mill.
The purity of juice 1 > than purity of mixed # juice, and the purity of juice 2 is normally 3-4 # points below the purity of juice 1. Hence, gradually decreasing to the last mill, which is about 58-64%. When simulating the Pol degrees, observe and maintain the value of khar < 4% and the PSHK between 96-98%.
9
Finally, check again thoroughly for the whole tandem.
Otherwise, re-do the simulation to maintain the values matching its limitation.
12.2.3 The limit values values
To simplify and speeding up the Projection of mill material balance, the following limit values will be use as guidance for the simulations: 1. The no-void density of mill#1 bagasse Depends on the existence and use of the fore worker and its roller material: 1 Crusher
1.15 - 1.16
1 Unigrator
1.15 - 1.17
1 Crusher + 1 Unigrator
1.15 - 1.18
2 Cane Cutter
1.15 - 1.18
1 Cane Cutter + 1 Unigrator
1.15 - 1.19
2 Cane Cutter + 1 Unigrator/Shredder
1.15 - 1.20
The Computer Program Program
XII-14
Mill Material Balance
2. The absorption ability factor (r) The value of r is between 1.38 – 1.4. Decreasing from the first to the ensuing mills. The value also depends on the fiber content of the cane crushed. For higher fiber content of cane will have a rather high value of r. #
The value of normal absorption ability factor (r’) for any mill (mill n) is lower than its value #
for the ultimate mill (mill n-1). It has decreasing graduation values up to the l ast mill. It is very important to observe, that the value of the normal absorption ability factor r’ for the last mill bagasse must be less than the value of its r. It is anticipated in practice that if the calculated value of r’ > r, then it is definitely juice will spraying off from the last mill’s delivery opening. Decreasing the value of the total mixed juice or the total water imbibition for such condition will retain the last mill’s delivery opening from spraying s praying off juice. 3. Juice extraction (En) The juice extraction (En) for each mill is best when the value in average > 60 %. When the extraction in every mill is less than 60%, then consider adding the amount of imbibitions water. But then reference shall also be made to the capacity of the existing evaporator tandem for the maximum quantity of imbibitions water. 4. The ratio of Ved to Vedo: Ved Vedo
= max. 1. And if > 1, the top roller is deflected.
5. Fiber fraction (kf) of bagasse bagasse in each mill. The following table indicates the ranged value of kf that increasing from the first to the ensuing mills: 4 mill tandem
5 mill tandem
Mill No.1
0.25 - 0.35
Mill No.1
0.25 - 0.35
Mill No.2
0.30 - 0.40
Mill No.2
0.28 - 0.38
Mill No.3
0.35 - 0.45
Mill No.3
0.32 - 0.42
Mill No.4
0.45 - 0.50
Mill No.4
0.37 - 0.47
Mill No.5
0.45 - 0.50
6. The Brix distribution number (kB)
2)
The value of kB is defined from the following formula: Extracted juice Brix weight (Bej) Original juice Brix weight (Bij)
x
Original juice weight (Wij) Extracted juice weight (Wej)
The value of kB is decreasing to the ensuing mills:
2)
Mill No.1
0.900 - 1.100
Mill No.2
0.900 - 1.000
Mill No.3
0.800 - 0.900
Mill No.4/last
0.600 - 0.800
Mill No.5/last
0.500 - 0.700
Extracted from C.R. Murray & J.E. Holt, The Mechanics of Crushing Sugar Cane, 1967
The Computer Program Program
XII-15
Mill Material Balance
#
#
It is advised when simulating the Brix degree of juice 1, the value of kB for mill 1 shall be made equals to 1.0 (one point zero). 7. The ratio of extracted extracted juices between the feed and the delivery openings openings (y): y = positive, juice juice is extracted by by the feed opening. opening. y = negative, juice is not extracted by the feed opening. opening. In the projection the value of y should be positive with an average between 0.10 and 0.30. 8. Coëfficient of friction (µ) (µ) Coëfficient of friction µ between bagasse / cane and the roller surface depends on the number of rotation of the roller, normally between 0.32 and 0.38. 9. The Compression (K) The value of compression K is is between 3.50 and 2.00; defined from the following formula: K
=
Vim Ved
Whereas: Vim
= no-void volume of incoming material per hour.
Ved
= actual escribed volume of delivery opening per hour.
Normally it decreasing from mill#1 to the ensuing mills, but some-times mill #2 has to work #
#
harder than mill 1. In this case the value of K for mill 2 is higher than the value of K for mill#1. It has a straight conformity with the value of fiber index (c). When the value of K is low then the value of (c) also low. Same as the value of K the value of fiber index (c) also indicates the ability of the rollers to grab bagasse / cane feeds efficiently, which depends on the roller shell material in use; whether it made of cast steel or cast iron should posses the ability to perform raw surface and against acid condition.
The Computer Program Program
XII-16
