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Acknowledgement
First, we pay our gratitude to the almighty Allah for giving us the
ability to work very hard successfully. Words actually will never
be enough to express our gratefulness and thankfulness. We
will try our level best to express of our gratefulness towards
some people.
We would like to express our words of appreciation, gratitude
& respect to our honourable Engr. Syed Iqbal Ahmed Rizvi, the
Director General Manager (DGM) Production and Muhammad
Aslam Khanzada, the chief chemist for their constant
guidance, advice, encouragement & every possible help in
the overall duration of our internship.
It is a great and unique pleasure to us that we have got a
chance to thank a large number of individuals for their help
and encouragement to make our internship successful. We’re
also grateful all engineers who guided us constantly, supported
& put up their valuable knowledge during the time of practical
orientation of our internship.
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Background
Larkana Sugar Mills’ foundation stone was first laid by the late
Zulfiqar Ali Bhutto, the ex-prime minster of Pakistan, on 30th of
January 1974. It finally took its inauguration ceremony on 14th
of March 1974. The mill is also known as Naudero Sugar Mills
these days. Naudero Sugar Mills (Pvt) Limited is 20km away
from the district Larkana.
Fundamentally, Sugar is a broad term applied to a large
number of carbohydrates present in many plants and
characterised by a more or less sweet taste. The primary
sugar, glucose, is a product of photosynthesis and occurs in
all green plants. In most plants, the sugars occur as a mixture
that cannot readily be separated into the components. In
some of the plants, the sugar mixtures are condensed into
syrup. Juices of sugarcane and sugar beet (Beta vulgaris) are
rich in pure sucrose, although beet sugar is generally much
less sweet than cane sugar. These two sugar crops are the
main sources of commercial sucrose.
Naudero Sugar Mills stand on 7th number in sugar production
in all over Sindh.
Its per day capacity of production is 6000 bags,
and each bag weighs 50kg.
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Naudero Sugar Mills manufacture the sugar of three different
types of qualities such as R1, R2 and R3.
The R1 quality of sugar is considered as a top quality, which is
mostly exported by the mill, and other two qualities R2 and R3
are sold in the markets domestically.
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Plant Description
Process Flow Diagram
Weighing
Main cane
carrier
Leveller
Cutting Fiberizing Milling
Juice
extraction
Clarification Evaporation
Crystallization Separation Refining
Drying
Finishing and
Packing
Storage
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Weighing
It’s essential to weigh the raw material before it is processed. Hence, the sugar
obtained from the farms are collected and weighed. Naudero Sugar Mills has two
weighing bridges of 40 tonnes and 70 tonnes of weighing capacity.
Cane carrier
The cane carrier is the moving apron which conveys the cane into the factory and
which assures the feed to the mills by transporting the cane from the yard to the
crusher. Since effective feeding of the crusher requires an elevated hopper, and the
cane must be raised to this high level from the level of the yard, where the carrier is
generally in a pit, the carrier always includes a sloping portion. Naudero Sugar
Mills comprises of two cane carriers known as main cane carrier and auxiliary
cane carrier.
Leveller
It’s used to level the raw material more specifically sugar cane so that it should not
face any hindrance for further process of cutting or fiberizing.
Cutting
When the unloaded sugar cane is dropped onto the cane carrier, it’s then passed
through leveller to equalise the sugar cane level and then moved forward to the
cutters. There are two cutters including third else connected by virtue of auxiliary
cane carrier. Cutters reduce the size of cane to required size so that it can be
fiberized well.
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Fiberizer
After the cane has passed cutting steps, then the small pieces are fiberized. The
Fiberizer is a large powerful hammer mill that shreds the cane into a fibrous
material. The cells in the cane stalk containing the sugar juice are ruptured but no
juice is extracted at this stage. Fiberizers run on the steam engine with pressure
required 20-24 bar and temperature required 350ºC-365ºC.
Milling
The shredded or fiberized cane is fed by the help of drag elevator through a series of
crushing mills to extract the sugar raw juice, which is then pumped away for further
processing after the screening. The remaining fibre is called Bagasse. The crushers
consist of two large grooved rollers mounted horizontally, and then one above of the
others. On the upper roller, heavy hydraulic pressure off 2200kg/cm2 is maintained.
There were six milling machines being operated by means of turbines. Those
turbines are more specifically known as Mill turbines. Milling machines run through
the steam turbine, which has the capacity to required the power of 300 kW each.
Every milling machines have its own turbine which is run by the steam taken from
the boilers. Each of them has the same capacity, the required steam temperature is
350 ºC -365 ºC and pressure is a 20-24 bar.
Juice extraction
Juice extraction by milling is the process of squeezing the juice from the cane under
high pressure between heavy iron rollers. Imbibition water is used to improve the
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extraction efficiency of the milling process: Hot water is poured over the cane just
before it enters the last mill in the milling train. The juice squeezed from this cane is
low in sugar concentration and is pumped to the preceding mill and poured onto the
cane just before it enters the rollers, the juice from this mill is the same way pumped
back up the milling train. Mixed juice (that is to say cane juice mixed with the water
introduced at the last mill) is withdrawn from the first and second mills and is sent for
further processing.
Whereas, bagasse as a byproduct of the milling process is used
as energy source for the concerned mill.
Boiler
For sugar making industry, a steam boiler is a necessary
equipment. The sugar mill boiler is used for steaming sugar
canes in the process. As one kind of environmental protection
industrial boiler, biomass fired boiler is widely used in a sugar
factory, which can burn bagasse. When choosing a steam
boiler, both quality and price should be considered to save cost
and ensure stable operation.
The bagasse is recycled as a fuel for the mill boiler furnace
which produces the steam for power generation with the
Turbines. The temperature of the steam is 350 ºC-400 ºC and
22kg/cm2 pressure. There are three types of steam generated
within boiler namely wet-steam, saturated steam and supper-
heated steam.
Bagasse feeds through bagasse carrier and returns carrier. They produce 20-24 bar
pressure steam.
There are four boilers each of them required 18-20 tonne/hr of water to produce steam.
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20 tonne/hr steam is generated. Induced Draft Fans are used to increase burning
efficiency in the furnace and it causes the temperature to reach up to 800 ºC-1200 ºC.
Power House
The powerhouse is one of the essential parts of any process industry. Naudero Sugar
Mills also is privileged to have it. The powerhouse is based on the steam produced by
the boilers. There are two steam turbines connected with dynamo motor. Each
dynamo motor produces 1.5 MW/hr of electricity. It requires 20 bars of pressure to
sustain itself if any decrement is observed it will vary the power generation, causes
the shutdown call occur.
The whole plant is facilitated with electricity from this powerhouse and the colony as
well.
Clarification of juice
The screened raw juice heated in online heater & primary juice heaters. where its
temperature is maintained from 25ºC -75ºC but not greater than 80ºC. Thereafter, the
clear juice is made to pass through the process of Defecation where PH of juice is
maintained 6.5 -7.5 by adding milk of lime (Ca(OH)2) and phosphoric acid (H3PO4) to
maintain the level of phosphate within juice.
Once again, the juice is heated up in secondary juice heater, where its temperature is
increased from 75ºC up to 105ºC. Afterwards, the same juice flows directly towards
flash tank wherein which it reduces the flow rate of juice and exhausts flue gases i.e
ammonia for the clarifier process.
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Now the juice is pumped to a continuous clarification vessel, a large, an enclosed and
heated tank known as Juice Clarifier in which clear juice is at the top and mud settle
down because we add polyelectrolyte (Accofloc A-2125) for the rapid reaction of
mud particles to form mud chunks which settle down at the bottom of clarifier tank.
Mud juice is pumped to rotary vacuum filters, where residual sucrose is washed out
with a water spray on a rotating filter, and the juice from this is sent to the defecation
tank to follow the same process again.
Vacuum filter has two vacua high-pressure vacuum & low-pressure vacuum. Low-
pressure vacuum collects the mud & high-pressure vacuum extract the juice from the
mud. Afterwards, Clarified juice move towards DSM Screen for further clarification
of juice.
Evaporation
Clarified juice is pumped to the vapour cells, where it passes through the 1st
vapour
cell then evaporator and likewise, goes till the final evaporator. Vapour Cell portion
there are presently three vapour cell bodies and at a time only two vapour cell bodies
are functional and considered them as one-unit cell, the vapour cell run on the source
of exhaust (form of steam comes from the boiler) produce 1st
vapour to run primary
and secondary heaters and evaporators & Pan station too according to the situation
we use them. The pressure of 1.2-1.5 bar exhaust steam is required in the first vapour
cell. The 1st
vapour cell produces 1st
vapour steam having 110 ºC -112 ºC.
There are five evaporator bodies and likewise, the 2nd
vapour produced from 2nd
of
evaporators having temp 80ºC -85ºC. Last two bodies of evaporators having contain
vacuum & vacuum shared to other bodies of evaporator 1st
2nd
& 3rd
vacuum
produces right to left in evaporator portion.
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Evaporation increases the juice box from 14 Brix to about 65 Brix which is syrup. By
passing through all the vapour cells 75% of water is evaporated
Finally, we obtained syrup which is through from the last evaporator to pan station.
The final syrup temperature from the last body of the evaporator is 65 ºC.
Crystallisation
Then in the crystallisation process, the syrup is boiled at low temperatures under
partial vacuum and some seedlings are added which causes the development and
growth of sugar crystals and the outcome is called massecuite (raw sugar crystals
mixed with molasses). After evaporation process, the syrup will come in syrup tank.
the crystallisation process takes place in vacuum pans which boil the juice at low
temperature under vacuum.The first step of crystallisation is in A-PAN where the
desired shape of crystals are formed and called A-massecuite. Here we get A-sugar
and A-heavy from A-centrifugal machines. A-sugar is conveyed through the conveyor
to the remelter where it is melted and pumped to the Buffer tank for storage purpose
and then pumped to the reactor tank for the further process carried out there.
Talo refinery where mud is removed. In talo there is four chemical is used named as
(COLOUR QUEST) (LIME SCURATE) (PHOSPHORIC ACID) & (TALO FLOAT
A-100) these four components reacted at reaction tank at the temp of 80 ºC -85 ºC.
Then fine liquor pumped to the Fine liquor tank from where it further pumped to the
Refining pan which gives us the R1, R2 and R3 sugar series wise. R1 sugar is made up
from fine liquor, R2 sugar is made up from R1 molasses called 1st
run off & R3 sugar
is made up from R2 molasses called 2nd
run off. And A-heavy pumped to the B-pan
which gives us B-massecuite from which we get B-seed and B-heavy through B-
centrifugal machines. B-seed is used in A-PAN with A-sugar and B-heavy is pumped
to the C-pan. C-pan gives C-massecuite that goes to a vertical crystallizer, where its
temperature down in order to make the strong structure of crystals. By adding spirit
(ETHANOL- C2H6O) with refined sugar in large amount. Then massecuite sends to re-
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heater afterwards C-massecuite sends to C-fore worker machines that give C-magma
and final molasses. Final molasses is sent to pitch. Final molasses also used in distillery
& other industries for making alcohol and other require materials. and C-magma
further gives us C-light and C-seed from C-after worker machines. C-light has used
again in C-pan and C-seed is used in B-pan.
In Talo refinery, four types of chemicals are added to the melted sugar, those are
(COLOUR QUEST) (LIME SCURATE) (PHOSPHORIC ACID) & (TALO FLOAT
A-100) By which density of melted sugar increased which
go down and pumped to the fine liquor tank and mud float
at the surface where it can be easily removed.
Mud or sludge goes down towards defecation. after the re-
melting process, there are 900 colours (Icumsa) in melted
sugar. In Talo refinery, 65% of colours are removed that is
350 colour(Icumsa) i.e. liquor having ph is 6.1-6.8.
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Separation and Refining
The sugar crystals are separated from the refine massecuite of (R1, R2
& R3) left in the centrifuges, cylindrical equipment that rotates at a
high speed. The molasses passes through the sugar crystal, the crystals
are trapped within the centrifuges and then washed with water. The
sugar is then transferred to the drying and cooling process.
Separation is done by the centrifugal machine/Refine machine.
There are three types of refining sugar. Named as R1, R2 & R3
respectively.
R1 sugar required (Icumsa) colour is below <35.
R2 sugar required (Icumsa) colour is below <50.
R3 sugar required (Icumsa) colour is below <70.
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Drying
The mixture of sugar crystals and liquor (massecuite) is centrifuged to
separate the white sugar crystals. The separated liquor which still
contains significant amounts of sugar is sent to a second, and then a
third crystallisation stage to extract more saleable sugar from the
syrup. The separated white sugar crystals discharged from the
centrifuges still contain some moisture. This is removed by passing
the sugar into a rotating two-stage dryer, through which filtered,
heated air is passed. The moisture level of the sugar at this stage is
about 0.06%. Further drying occurs during conveying to the silos or
packing areas and in conditioning silos. In the centrifuge process,
condensate water is used to wash sugar, which results in a humidity
between 0.3% and 0.6%; therefore, it is necessary to pass it through
the drying process to reach levels between 0.2% for raw sugar and 0.03% for white
sugar. The temp: of final sugar is 35 ºC.
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Finishing and Packing
When the sugar is completely dried, it’s packed into bags and checked the
temperature through thermometer of every bag, if any bag does not fulfil its
requirement then is sent back for reprocessing; it is strictly instructed that they
have to maintain the temperature of each bag up to 35 ºC maximumly. Then
after, packings are checked for its balance for each bag by digital weighing
machine and sealed each and every bag for markets. Naudero Sugar Mills has a
good production of sugar in every season.
Storage
The ready bags are then stored for
transportation as per their demand of markets.
Conclusion
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Conclusively saying, we would like to suggest as have been interns over there in the
plant. Rather fleeing ammonia as waste, it’s supposed to be utilised so as to make the
process very useful.
Proper maintenance is the essential key concepts for the industry at the time of
processing of any equipment. Maintenance always increases the life of plant as well as
efficiency. Proper management is very much important. During our internship period,
we observe the plant face three times shutdown calls. Undoubtedly, Human Resource
department will have to face the deficiency in production that causes a loss of the
economy of the industry and its reputation as well.
The department can improve the workers’ skills by giving them one-day training from
renowned consultants and trainers before the start of the season.
Workers were not following the proper safety precautions, which can cause any
accident in future. Life measures a lot. Worker’s life is worth concerning that has to be
under one's consideration.
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Contact Information
Third Year Chemical Engineer from the department of
Chemical Engineering Mehran University of Engineering
and Technology, Jamshoro.
Name
Aamir Ali Seelro
Cell
+923333604638
Email
aamiraliseelro@yahoo.com
15ch31@students.muet.edu.pk
