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1
TRIBHUVAN UNIVERSITY
INSTITUTE OF ENGINEERING
THAPATHALI CAMPUS
A Seminar paper on
Effect of Storage Time and Type of Conditioning on Filling Value of Cut
Rolled Stem of Tobacco
By
Bikram Dahal
A SEMINAR PAPER
SUBMITTED TO THE DEPARTMENT OF INDUSTRAIL ENGINEERING
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE
DEGREE OF BACHELOR IN INDUSTRIAL ENGINEERING
DEPARTMENT OF INDUSTRIAL ENGINEERING
KATHMANDU, NEPAL
SEPTEMBER 22, 2014
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Abstract
Stem of tobacco has to be conditioned either with steam/water or water only
depending on bulking time available and best utilization of machines. Different type
of conditioning have effect on filling value so it’s necessary to find out if there is
significant effect of type of conditioning on filling value. Some batch of CRS are keep
in advance for processing next day in CRS bin. Storage time also effect filling value.
This research paper discuss about effect of storage time and type of conditioning on
filling value Filling power of tobacco has great economic important in tobacco
industries as well as affects every parameter of final cigarettes produce like losses end,
firmness, density, burning rate etc. so the effect of time of storage and type of
conditioning was studied. Result show that type of conditioning have no significant
difference in filling value for two grade of stem whereas remaining one grade’s filling
value is significantly higher when cold conditioned than hot, whereas storage time has
significant effect on filling value. Filling value of CRS kept in advance have greater
filling value than CRS proceed on same day.
Keywords: filling power, CRS, Tobacco Stem.
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1. Introduction
Tobacco leaf is separated into two parts lamina and stem. Stem is the midrib of leaf
and remaining portion is known as lamina. Most cigarette contains approximately 20%
stem by weight. The material is low cost and has a potential, through processing, to
give a high filling value. However, when smoked, stem is typically described as woody,
cellulosic, burnt and acrid with more irritating properties than lamina (Stephenson,
1994). So stem are processed in tobacco industries, first conditioned, bulked, cut into
small piece in 140-160CPI, expanded and then rapidly dryer and mixed with lamina at
ratio of 20:80 to reduce its irritating property. (ITC)
Filling value is define as the ability of a unit weight of the material to occupy space.
Applied to cigarettes, the filling value of tobacco blend is its ability to ‘fill out’ or ‘firm
up’ a cigarette of constant volume i.e. circumference and length constant (Akehurts,
1968). Filling power is intrinsic property of material Firmness is define as a cigarette
rods resistance to compression. Each Manufacture established an internal standard of
firmness of his cigarette brand. One of studies conducted by (Wong, 1976) concluded
that the relationship between cigarette firmness, in term of weight savings, and tobacco
filling power was highly significant (R=0.83). Other researcher also support this facts
(Walker, 1974). To illustrate: The effect of Filling value and cost , Assuming a finished
blend cost of Rs. 2000 per kg, a 4 percent increase in bland filling power will save
manufacturer approximately RS 3.4 crore per billion of cigarettes sold (Semfie ld,
1973). Considering average weight of cigarette of 850mgms per cigarette. And 2%
Increase in filling power is claimed for the Water Treated Stem process compared to
CRS when incorporated at 20% in cigarettes (Grandpre, 1887).
Conditioning is the process of spraying steam/water or water only on dry stem or
lamina to increase moisture for cutting. Conditioning can be done by two method hot
and cold. In hot conditioning steam/water is sprayed over stem in closed chamber at
fixed temperature and pressure and for certain time (as per the standard protocol of
company). And in cold conditioning only water is used instead of steam and water. For
cold conditioning stem has to be bulked for 12 hours and for hot conditioning 2 hours.
(ITC)
If stem has to process next day they are cold conditioned earlier day. So that whole
machines can be fully utilized. I.e. if conditioning is not carried out the day before,
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cutter has to be in ideal time till conditioning and bulking time of CRS. Total of eight
operation can be cold conditioned in Surya Nepal. Presently mostly only two-three
operation are cold conditioned as this two-three operation can be cut during same time,
as hot conditioning and bulking is carried out next day. In similar way CRS are stored
in advance for next day so that lamina dryer line can be operated along with lamina
conditioning line. As conditioned lamina are also kept in advance. So that no machines
are ideal.
So due to these reason it is necessary to know the effect of type of conditioning
and storage time on filling value. So that process variation of filling value can be
explained and best type of conditioning can be found. This help to make necessary
adjustment in program of conditioning type such that most of batch of stem can
conditioned in best conditioning type of conditioning process. Knowing the effect of
storage time will help to explain variation of CRS filling value between two operation
to some extend and make procedure to store cut tobacco at least 12 hours before
processing.
.
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2. Limitation
Filling value where measured at different moisture using moisture
correction factor. Moisture correction factor was best 12%-15%. Few
sample had filling value larger than 15%.
Process variation can be observed so large data were collected to reduce
error.
Temperature of samples were different.
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3. Objective
To find effect of conditioning on filling value.
To find effect of storage time on filling value.
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4. Methodology
CRS’s filling value of two month was collected from data daily report of QUAS of
Surya Nepal. Data collected were categorized as type of stem along with time of
storage and type of conditioning. Addition 10 operation were tracked of GRADE 3
stem. Sample where taken after CRS bin and their filling value were measured and
some portion of same small were kept in humidity cabin, maintained at 21+1 C and
HR 62+2 for two days and it filling value were measured. Filling value of CRS cutter
is measured using MC and height of sample in densimeter. Moisture Content was
measured by weighting 10±0.005 gram of sample in tin box and then keeping tin box
in oven for 3hours.followed by half an hour in silica jell compartment. Finally net
weight of sample was taken.
Moisture content= 10- Net weight of tin after keeping in oven and silica jell.
Height was measure using densimeter. Densimeter consist of graduated cylinder of
radius(R) with a closely fitting plunger and weight. The procedure for measuring
height is a known weight i.e. 20 ±0.05 gm. weight is place in cylinder and plunger is
inserted into cylinder gradually weight of 3 kg is applied. After 30 sec height (H) of
plunger is measure from based of cylinder.
Volume occupied by sample= πR2H.
Filling value = volume* moisture correction factor.
For study of effect of hot conditioning and cold conditioning, effect of storage time
on measure filling value of CRS, first normality of data was tested using Shapiro-wiki
test than for equality of variation Levene test was carried out followed by t-test to find
if two series of data had significant difference.
Shapiro-Wilk test was carried out in each data series to find out if data series were
normal disturbed or not. The null-hypothesis of this test is that the population is
normally distributed. Thus if the p-value is less than the chosen alpha level, then the
null hypothesis is rejected and there is evidence that the data tested are not from a
normally distributed population. In other words, the data are not normal. On the
contrary, if the p-value is greater than the chosen alpha level, then the null hypothesis
that the data came from a normally distributed population cannot be rejected. E.g. for
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an alpha level of 0.05, a data set with a p-value of 0.05 rejects the null hypothesis that
the data are from a normally distributed population (Shapiro, 1965). However, since
the test is biased by sample size, the test may be statistically significant from a normal
distribution in any large samples. Thus a Q–Q plot is required for verification in
addition to the test (Markowski, 1990).
And Levene test for equality of variation was used to test whether variation
between sample were equal or not. Levene's test is an inferential statistic used to assess
the equality of variances for a variable calculated for two or more groups. Levene's test
assesses this assumption. It tests the null hypothesis that the population variances are
equal. If the resulting P-value of Levene's test is less than some significance level
(alpha value), the obtained differences in sample variances are unlikely to have
occurred based on random sampling from a population with equal variances. Thus, the
null hypothesis of equal variances is rejected and it is concluded that there is a
difference between the variances in the population (Levene, 1960).
For normal population, when the sample sizes n1 and n2 are not large and σ1≠ σ2.
We purpose
Null hypothesis H0= there is no significant difference between two mean.
Alternative hypothesis H1= there is significant difference between two mean.
Test statistic “t” = (x̅1−x̅2)−𝛿
√(𝑆1
2
𝑛1−
𝑆22
𝑛2)
Where
x̅1and x̅2 are means of population
s1 and s2 are standard deviation of population.
If calculated p-value is less than significance level α. Null hypothesis H0 is rejected.
If calculated p-value is more than significance level α we fail to reject Null hypothesis.
For comparison of two significant different mean bar graphs are used.
All analysis of tests where were carried out using SPSS tool.
(Rice, 2006)
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5. Literature Review
Stem expansion is favored at high temperatures (up to 250°C) and high moisture
levels (up to 30% m .c.). These factors lead to an increase in the water vapor pressure
inside the cells of the stem and to a more elastic cell structure (Grandpre, 1887).At
these temperatures, heat enhances the production of water from the decomposition of
low molecular weight polysaccharides and sugars so more water is available for
expansion (Reynard, 1985). A high internal pressure in stem is necessary to have good
expansion and, in the build-up of this pressure, the stem cell structure plays an
important role. Four types of cell structure are present in stem: epidermis cells,
collenchyma cells, parenchyma cells and vascular bundle cells. The structure of the
epidermis cells which are circularized and covered with wax, and the collenchyma
cells which are thickened with cellulose, restrict the loss of water during heating, thus
contributing to the build-up of the internal pressure. After expansion the walls of these
cells are rigid enough to keep their new structure. Stems expanded in a vacuum oven
at room temperature showed the same behavior as conventionally expanded stem
indicating that expansion is mainly due to the build-up of internal gas pressure in the
cell walls (Reynard, 1985).Stem are heated in hot conditioning as heating open the
capillary’s that have shrink during drying so moisture can easily penetrate. Hence
bulking time is less for hot conditioning. (ITC)
Longer stem expand more than shorter stem due to pressure drop. (Grandpre, 1887).
Temperature 85 0F at 21.5 % MC of tobacco is best environment for cutting lamina, if
temperature is increase 90-95 there is 0.6-1.2g/cc loss in filling value. Or else MC of
22-22.5% at 110 0F to 115 0F is best for cutting (Morris, 1984).
Each stem have its own instinct property to absorb water. For example consider a
blend made up of equal quantities of two types; one able to absorb water quickly and
the other absorbing more slowly. If we assume that each stem had the same opportunity
to absorb water and that the average moisture of the blend is correct, then we are forced
to accept that 50% of the blend is drier than Intended and 50% wetter than intended.
Steam are passed over series of vibrating conveyer so that they roll. The advantage of
rolling is that enables a better cheese formation at the cutter. The better cheese
formation, the fewer heavies’ pullouts (winnows) and the lower the cheese pressure
which can be used. Lower cheese pressure usually results in higher filling power and
cleaner cutter operation. The disadvantage of rolling is the danger of damage to the
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stem fiber and cell structure. Damage will occur if the stem does not have a sufficient ly
high penetrated moisture content. Any cracking, rupturing or fibrillation of the stem at
rolling is an indication of inadequate conditioning and will lead to loss of filling power
and yield potential, Cutting moistures have in the past been set somewhat arbitrarily
Today the philosophy would be to use as high a penetrated moisture content as possible.
The use of water sprays to lubricate and clean the rollers will impart some surface
moisture to the stem and in effect reduce the penetrated moisture associated with an
out moisture test (Solm, 1993).
t-test is used widely in comparison between two means in physiology to weapons
(Onlinestatbook, 2014).
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6. Result
Following is the result of normality test all data series used for t-test. As significant
value or p-value is greater than 0.05 we failed to reject null hypothesis i.e. data are
normal.
Tables 6.1 p-value of Shapiro-wilk Test
* S = Sample processed on same day A =Sample processed advance
CC =Cold Conditioning HC = Hot Conditioning
Lavene test result show that all value except GRADE 2 after and same have equal
variation. As p-value for all other data series is more than 0.05.
Table 6.2 Levene-s test p_value along with t-test p_value
Grade Stem
Shapiro-Wilk Type Of Conditioning
Shapiro-Wilk
p_value p_value
Filling
value
GRADE 1 "A" 0.353 GRADE 1 "CC" 0.15
GRADE 1 "S" 0.353 GRADE 1 "HC" 0.934
GRADE 2 "A" 0.619 GRADE 3"CC" 0.432
GRADE 2 "S" 0.426 GRADE 3"HC" 0.98
GRADE 3"A" 0.438 GRADE 2 "CC" 0.392
GRADE 3"S" 0.717 GRADE 2 "HC" 0.889
Levene's Test for
Equality of Variances
t-test
F p_value p_value
Filling
value
GRADE 1 "A"/
"S"
Equal variances
assumed
0.02 0.89 0.004
GRADE 2 "A" /"S"
Equal variances not assumed
4.75 0.03 0.019
GRADE 3"A"
/"S"
Equal variances
assumed
0.58 0.45 0.196
GRADE 3"A" /"S" “My samples”
Equal variances assumed
0.07 0.8 0.022
GRADE 1 "CC"/"HC"
Equal variances assumed
0 0.96 0.008
GRADE 3"CC"/"HC"
Equal variances assumed
0.17 0.68 0.417
GRADE 2
"CC"/"HC"
Equal variances
assumed
1.78 0.19 0.092
GRADE 2 "CC"/"HC" "A"
Equal variances assumed
0.02 0.9 0.555
12
t-test result between hot and cold conditioning for different grade of stem shows
that there is no significant different between hot and cold conditioning for GRADE
3and GRADE 2 and for GRADE 1 filling value differ significantly for type of
conditioning. Average filling value of cold conditioning is always greater than that of
hot conditioning.
t-test result of same day and advance show that there is significant difference when
CRS are proceed same day or kept for next day. FV of CRS advance is always greater
than CRS of same day.
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7. Analysis and discussion
From t-test it can be observed that type of conditioning has no significant effect on
filling value from GRADE 3and GRADE 2 but has significant effect on filling value
of GRADE 1. Possible theory for this is that, this is due to size of stem. One type of
stem used in GRADE 1 are longer so it takes more time for water to penetrated as
moisture mostly penetrated through capillary action. As it can be observed that cold
conditioning always has higher filling value than cold conditioned stem this is due to
high temperature can damage some cells and if there is already cracks, holes in stem it
can further damage it. As stem have their own intrinsic property to absorbed water and
blend of steam is mixture of many grade it is possible that for some grade of stem hot
conditioning followed by two hours of bulking is not enough. But cold conditioning
and twelve hour of bulking is enough. Other factor effecting filling value may be
temperature of sample while cutting as hot conditional same have few degree Celsius
higher temperature than cold conditioned sample.
From t-test it is observed that storage time has significant effect on filling value of
CRS. The theory is that once expanded cell need certain time to form rigid structure
that can withstand pressure applied to CRS during measurement of height. As cell
membrane is made of polysaccharides which need time to form a rigid shape. The
temperature of sample where also different as advance sample are process at morning
time when temperature is low. As cell with lower temperature have more rigid cell
wall structure than cell at higher temperature. (Waikato, 2014).
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8. Conclusion
Filling Value of tobacco stem is not effected by type of conditioning process from
all grade except that for GRADE 1 stem. This grade of stem have longer stem size so
cold conditioning provides enough time for penetration of moisture. Time of storage
effect the filling value as expanded tobacco need time to for rigid cell structure. Due
to rapid evaporation tobacco don’t loses their expanded structure but if force is applied
on them their structure collapses. Storage for day provides time for these structure to
be rigid and permanent. Hence the filling value of higher of CRS kept in advance is
higher than filling value of CRS processed same day.
15
References
Akehurts, B. M. (1968). Tobacco.
Grandpre, D. Y. (1887). A Review of Firmness and Tobacco Properties. Montreal:
Imperical Tobacco Limited, R&D Division.
ITC. (n.d.). Standard Operating Procedure . Indian Tobacco Company Limited.
Levene, H. (1960). Contributions to Probability and Statistics: Essays in Honor of
Harold Hotelling. Stanford University Press. pg 278-292.
Markowski, C. A., & Markowski, E. P. (1990). Conditions for the Effectiveness of a
Preliminary Test of Variance. The American Statistician, 44.
Morris, P. (1984). Aspects of Tobacco Processing . Phillips Morris.
Onlinestatbook, (2014). Onlinestatbook Retrieved from the case studies:
http://onlinestatbook.com/2/case_studies/case.html
Reynard, R. J. (1985). Wetting, Heating and Drying Single Tobacco particles, Part II.
British American Tobacco RD. 1994.
Rice, j. A. (2006). Mathematical Statistics and Data Analysis. Duxbury Advanced.
Semfield, D. M. (1973). Tobacco filling Power: part 1. Cigarettes Maufacturing
Techonolgy , 46.
Shapiro, S. S., & Wilk, M. B. (1965). An analysis of variance test for normality
(complete samples). Biometrika, 52.
Solm, E. J., O'connor, L. H., Young, H. J., & Beeson, D. (1993). Drying and
Moisturing of Tobacco Stems. BAT, product Development.
Stephenson, T. A. (1994). Investigation Into the Effect of Stem Moisture Content on
Process & Product Performance. Southampton : British-American Tobacco Co. Ltd.
The University of Waikato, (2014, 20 9). Plant Structure and function. Retrieved from
Science on the Farm: http://sci.waikato.ac.nz/farm/content/plantstructure.html
Walker, E. K., & Voisey, P. W. (1974). Measurement of Cigarette Firmness and Its
Relationship to Filling Value of cut Tobacco. Tobacco 176(2T).
Wong, J. S., & Wilson, T. L. (1976). A Study of Variation in Tobacco Filling Power
and Cigarette Firmness. Amatil Report .
16
Appendix 1: Normality Test Result
Grade Stem Shapiro-Wilk
Df p_value
Filling value
GRADE 1 "A" 14 0.353
GRADE 1 "S" 36 0.353
GRADE 2 "A" 48 0.619
GRADE 2 "S" 67 0.426
GRADE 3"A" 11 0.438
GRADE 3"S" 14 0.717
Type_Of_Conditioning Shapiro-Wilk
df p_value
Filling values
GRADE 1 "CC" 19 0.15
GRADE 1 "HC" 17 0.934
GRADE 3"CC" 23 0.432
GRADE 3"HC" 19 0.98
GRADE 2 "CC" 44 0.392
GRADE 2 "HC" 22 0.889
Shapiro- Wilk Statistics of Type of Conditioning Samples
Shapiro- Wilk Statistics of Same Day and Advance Samples
17
Appendix 2: t-test statistics
Levene's Test
for Equality of
Variances
t-test for
Equality of
Means p_value (2-
tailed)
Mean Differ
ence
95% Confidence
Interval of the
Difference F
p_val
ue t df
Lower Upper
Filling value
GRADE 1
"A"/ "S"
Equal
variances
assumed
0.02 0.89 3.03 48 0.004 2.01 0.68 3.35
GRADE 2 "A" /"S"
Equal
variances not
assumed
4.75 0.03 2.28 85.96 0.025 0.88 0.11 1.64
GRADE
3"A" /"S"
Equal
variances
assumed
0.58 0.45 1.33 23 0.196 0.79 -0.44 2.01
GRADE
3"A" /"S"
Equal
variances
assumed
0.07 0.8 2.47 23 0.022 1.47 0.24 2.71
GRADE 1
"CC"/"HC"
Equal
variances assumed
0 0.96 2.83 34 0.008 1.85 0.52 3.18
GRADE
3"CC"/"H
C"
Equal
variances
assumed
0.17 0.68 0.82 40 0.417 0.39 -0.57 1.36
GRADE 2
"CC"/"HC
"
Equal
variances
assumed
1.78 0.19 1.71 64 0.092 0.76 -0.13 1.66
GRADE 2
"CC"/"HC" "A"
Equal
variances assumed
0.02 0.9 0.59 47 0.555 0.38 -0.92 1.69
t-test Statistics of Type of Conditioning and Time Difference Samples