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POLYESTER PLANT
Submitted To Mr. Raza Ali
(Area Manager Polymer Section)
Submitted By Abdul Hayee
M. Nasir
Aaqib Ali
Junaid Aftab
Usman Saleem
Date Of Submission 12-07-2014
Discipline Chemical Engineering
IBRAHIM FIBRES LTD.
Internship Report
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DECLARATION
Mr. Waleed
Manager Training
Ibrahim Fibers Limited, Polyester Plant.
Dear Sir:
Submitted for your review is our internship report for
Ibrahim Fibers Limited, duly completed within the
deadline. We hereby declare that the report is submitted
in long report format, as per the guidelines and is based
on peer reviewed information as guided by our
instructors and supervisors at the plant facility.
Regards
AbdulHayee| M.Nasir|Aaqib Ali |Junaid Aftab|Usman
Saleem|
Institute Of Chemical Engineering (ICET)- University Of
Punjab-Quiad e Azam Campus-Lahore
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ACKNOWLEDGMENTS
We are thankful to Almighty Allah for His
unlimited blessings and bounties; for keeping us
sane, sound and successful, Our parents for all their
support and trust in us, Our Instructors Mr. Saeed
and Mr. Haseeb in the Polymer Section. Mr.Faqeer
Muhammad, Senior Deputy Manager Utilities. Mr.
Ahamd Aata Area Manager, Spinning and Fiber
Line 1 for all his guidance and help. We are also
thankful to all the shift engineers, operators and
every individual who has helped us even a bit for
the completion of this report.
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1. Polymer & Polymerization:-
Poly mean many and mer mean molecules. The
process in which smaller molecule unit (monomers) combines to form larger
molecule unit(polymer) is said to be polymerization.
Monomers ---------------------------- Polymer
1.1 Types of Polymers:-
There are following typesof polymers
1. Thermoplastic polymers
2. Thermosetting plastic polymers
The polymer which can be reheated and remolded several times
without significant change in their properties is said to be thermoplastic
polymers. It is manufactured by addition polymerization reaction.
The polymer whichcan be heated and molded once and cannot be reuse
again is said to be thermosetting plastic polymers .it is manufactured by
condensation polymerization.
1.2 Types of polymerization:-
There are followingtypes of polymerization.
1. Addition polymerization.
2. Condensation polymerization.
3. Ring openingpolymerization.
When small molecules joined together in the presence of heat, catalyst
or radiations with the elimination of small molecule such as water or
alcohol then the polymerization is said to Addition polymerization. e.g.
formation of PVC.
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When the polymer is formed with the elimination of small molecule
such as water or alcohol then the polymerization is said to be
condensation polymerization. e.g. formation of Polyester
The formation of polymer by the opening of ring such as those of others
e.g. Formation of nylon 6 from caprolactan.
2. Polyester:-
Polyesters are polymers that contain ester linkage groups along
their main chains. The International Standard Organization (ISO) defines
polyester fibers as those from polymers based on a diol and a
terephthalic acid. PET is a polycondensation product of ethylene glycol
and tere phthalic acid (or dimethyl tere phthalate). Polymerization of PET
proceeds a two-step process in which the first step is a reaction between
a 2-to-1 ratio of ethylene glycol and terephthalic acid (or di- methyl
terephthalate) that leads to the formation of bis(hydroxyethy1)tercph-
thalate (BHET). In the second step, trans esterification of BHET yields
PET.
↓
CH2 CH2 CH2 CH2
O O
O
C
O
C O O
C
O
OH
C
O
OH
CH 2 CH 2 OHHO
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2.1 Properties of Polyester:-
1. Extreme versatility in process.
2. Excellent heat and chemical resistance.
3. Good electrical and mechanical properties.
4. The surfaceof fiber is rough.
5. The fiber of polyester is static in nature.
2.2 Uses of polyester:-
1. Major use of polyester is in textile industry.
2. It is used in aeronautical parts.
3. It is used in laminates.
4. Polyester used in the manufactureof synthetic resins.
3. Industrial Preparationof Poyester
Raw material used for the preparation of polyester.
1. Pureterepthalic acid (PTA)
2. Mono ethylene glycol (MEG)
There are two additivesused in the polyester industry.
1. Titanium dioxide (TDO)
2. Antimony triacetate as a catalyst
HTM oil Sanotherm used as a heat transfer in polyester industry.
3.1 Pure Terepthalic Acid (PTA):-
Pta is a petroleum product in powder form. Pta is bi-carboxlic
acid formed by the oxidation of para-xylene in the presence of acetic acid. It is
white crystalline powder and it is explosive when it is exposed to air therefore
we use nitrogen as conveying medium. Different brands of Pta are Mitsui
(Japan),Amoco(USA),T-Kong(Korea),ICI(Pakistan,UK),inter quisa(spain).
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Properties & Structure ofPTA
Color White powder
Molecular weight 166.14 g/mole
Particle size 70~160 micron
Moisture <0.2%
Impurities Acetic acid,Mo,Cr,Ni,Fe
ph 2.16
3.2 PTA Transportation:-
PTA is imported at Karachi port from there Pta is sent to
polyester plants either through bags or either through container. Each trailer
contain 35~50 bags.PTA bags is unloaded and stored in warehouse of
capacity of ~6500 bags. Each bag carry 1100 kg of PTA and container has
capacity of 22000kg. from warehouse PTA is stored in Storage silos according
to desire circumstances. Each bag is pneumatically charged to the main
storage silos. Ibrahim fibers use PTA manufactured by following two
companies.
1. Lotte Pakistan
2. Siam mitsui
The plant produces 600 tons/day of PET. Whereas the PTA required is 860
kg/ton of PET. Therefore, daily consumption of PTA is 516 tons/day.
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3.3 PTA Handling:-
Ibrahim Fibers Limited uses PTA in pure form instead of impure form.
This pureform ensuresthe achievement of high quality products.PTA ishighly
explosive so extra care is needed for handling of PTA . Storage of PTA requires
special precautionary measures Protection of PTA from moisture is also
necessary otherwise agglomeration will take place and the quality of the
product may decrease.
3.4 PTA Conveying :-
PTA is highly explosive when it came in contact with 5%
oxygen. It will form a mixture by reacting with oxygen which is extremely
explosive therefore we cant use pure air as a conveying medium because air
also contain 21% of oxygen by volume. We need inert source by conveying
PTA. The rest 79% of air by volume is nitrogen and it is inert and it will not
react with PTA and do not disturb the equilibria during conveying.
Nitrogen is separated from air by utility department and provide
it for the conveying of PTA. Nitrogen gas is first filtered in a bucket-type filter
and is then compressed in rotary type compressors. After passing through
these compressors, both the temperature and the pressure of nitrogen are
increased. This nitrogen is then passed through a shell & tube heat exchanger,
where cooling water is present on the shell side and nitrogen is present in the
tubes. The temperature of nitrogen is reduced from 240oC to about 55oC. This
compressed and cooled nitrogen is again filtered to remove any PTA particles
present. Nitrogen gas is then used for conveying of PTA.
3.5 PTA Charging:-
There are two charging system used for the charging of PTA into main
silos.
1. Bag charging system.
2. Container charging system.
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Which charging system is in use depend upon the circumstances.
In bag charging the polymeric bag the hoist lift the polymeric bag to
charging station. Bag is lifted toward the feeder where the bag is cut
from bottom and discharge of PTA from bag start taking place. Feeder
contain vibrating mesh plate to avoid the transportation of any coarse
particle. There is rotary feeder/valve in the conveying line of PTA from
feeder whose rpm are controlled to adjust the flow rate of PTA toward
the buffer silo. Feeder feed the PTA in buffer silo 1204-V01. At the
discharge of buffer silo there is rotary feeder provide path to PTA
toward conveying nitrogen line which convey PTA toward the main
storage silos 1204-T01, 1204-T11 and 1204-T12. Storageof PTA in desired
silos is controlled by using divergence valve. After conveying PTA
nitrogen is filtered and compressed in compressor for again conveying
of PTA toward storage silos. After compression the temperature of
nitrogen shoot up and then it is cooled by using heat exchanger. The
amount of oxygen is controlled by using interlocks.
PTA imported from Thailand comes in containers. A container charging
system is therefore presentfor charging of PTA from containers.
Container is loaded on the charging station. Inclination is provided and
PTA is introduced in the feeder 1204-X57 after screening of any
undesired particles. From the feeder, compressed Nitrogen (N2) carries
PTA to the silos 1204-T01, 1204-T11 and 1204-T12.
Silos are large vessels cylindricalin shape with conical bottom. PTA feed
is stored in these silos. IFL-1 has one silo named as 1204-T01, IFL-2 has
two silos named as 1204-T11 and 1204-T12. Also IFL-3 has two silos
named as 1214-T11 and 1214-T12. These silos are equipped withlevel
transmitters which show an alarm if PTA level reaches high or low set-
pointlevel. PTA is transferred from these silos to the feed vessels/day
silo with the help of compressed nitrogen when required. Storage silos
is provided withpseometer ringused for the purgingof PTA stored in
main silos this is doneto maintain pressurein the silo and to avoid the
Agglomeration of PTA in the storage silos. There is Rotary feeder
presentat the bottom of the Storage silos which control the flow of PTA
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toward the conveyingnitrogen which carry PTA toward the Day silo for
further operations.
Schematic Flow Sheet Of PTA Section
4.Mono-Ethylene Glycol(MEG):-
Mono Ethylene Glycol raw material for PET manufacture, is a crude oil
refinery product in liquid form, mostly imported from two countries.
1. Mobil (Saudi Arabia)
2. Equate(Kuwait)
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MEG is transported from these countries by ships, from where it is off-
loaded at Port Qasim Karachi. From there, MEG is sent to IFL Plant site on
MEG tankers of capacity of 40.0 tons. Each MEG tanker has two chambers 20
tons each chamber.
Properties & Structure of MEG
Molecular weight 62.03 g/mole
Boiling point 197 centigrade
color NO
taste Mild sweet
Specific gravity 1.116
4.1 MEG Unloading & Transportation:-
Unloading of MEG starts with the arrival of the container trucks to the
unloading area of MEG. MEG is unloaded from tankers with the help of
a centrifugal pump assembly. Two centrifugal pump assemblies are
present in case if one pump malfunctions then other pump is utilized.
Each centrifugalpump assembly can be isolated by closing the butterfly
valveswhile the MEG passes through a fully opened butterfly valve into
a strainer which containsa mesh to remove any solid particles from the
feed of MEG.. It then passes through a globe valve where the flow rate
of MEG can be adjusted. Then globe valve is used to adjust the flow rate
of the feed .Flow rate of MEG is determined by passing it through Micro
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Motion a flow rate sensor, after which MEG is filtered again by a bucket
type filter which contains a fine mesh to remove the undesired
impurities from MEG.
MEG then enters a 3 way valve. The valve directs it to one of the two
MEG storage tanks, 1107-T01, and 1107-T02for IFL-1. One tank is filled
at one time. The total capacity of the tanks is 2000 tons/each. Each tank
is equipped with level transmitters which generate the low level alarm
and High level alarm if MEG level in tanks reaches the fixed set-points.
The tanks are filled up to a maximum level of 90%. Prior to the storage,
MEG is pumped to a flow meter that shows both flow rate and quantity.
The flow rate of pump is 2000 kg/hr.
The sample of MEG is taken from sampling point and send to chemical
lab for testing of moisture and for the determination of viscosity. The
moisture content of MEG is determined as it should not exceed 1%.if it
exceed 1% then it will not suitable for processing.
The PET produced in esterification requires 340 kg/ton of MEG. The
daily production of PET is 600 tons/day. Hence, 201 tons of MEG is
required each day. MEG is transported from the storage tanks to the
processing section in the building by pumping through centrifugal
pumps.
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4.2 Ethylene Glycol Recovery:-
The MEG produced in thesecond reaction contains moisture, aldehyde
and monomer the combine mixtureof these componentsis said to be
SLUG. From this sludge, we are concerned with the distillation of MEG and
water. The boiling pointof MEG is 197oC; henceit is recovered as bottom
product. Water is obtained overhead and is drained and this typeEG is
called as Spent EG.
1. The spent-EG is introduced to kettle type evaporator. The evaporator is
fed form the MEG storage vessel 3101-V01. This evaporator heats the
feed by the Heat Transfer Media (HTM) moving in coils. The
temperature of this kettle type evaporator is maintained at 165oC. SEG
and other low boilers are vaporized, while very high boilers settle down
as sludge which is discharged continuously with the residue pump into
the waste barrel each weighing 225 kg. The MEG and H2O vapors in the
kettle are then introduced at the sixth plate of a bubble-cap type
distillation column.
2. The distillation column in EGR section has 16 plates with a bubble-cap
arrangement which ensures the maximum possible separation of SEG
and H2O. They are assembled in bubble cap arrangement with average
tray temperature of 120oC. The whole column is operated under
vacuum conditionsof 300 mbar. This vacuum is created with the help of
eccentric type vacuum pumps. The water is evaporated and is collected
at the top in a condenser 3101-D01. Thecondenser is a shell & tube type
heat exchanger with vapors at the shell side. Part of the condensed
water is refluxed while remaining is sent for treatment. At the top, the
water vapors escaping from the distillation column are sent to the shell
side of a condenser (3101-E02) and are condensed by cooling water
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present in the tube side. The vapors condense and go inside a reflux
vessel 3101-V02.
3. This condensateis used as reflux in the distillation column. A pneumatic
operated control valve controls the amount of reflux entering the
distillation column. The reflux vessel is equipped with a sight glass to
see the level. A fixed level is maintained and the overflow is drained off
into a vessel 3101-V03. A vacuum pump assembly removes the
uncondensed water vapor from thecondenser. The vacuum pump sucks
the uncondensed vapors through the condenser. These vapors enter the
shell side while the chilled water enters the tubes of the condenser and
partially condenses the vapors while some are still left uncondensed.
The mixture of the vapor and liquid water then is forced into a knock-
out drum where the left over vapors are also condensed and then the
condensed water goes inside a storage tank 3101-V03. A fixed level is
maintained in the vessel and the overflow is drained. Recovered
ethylene glycol (REG) is removed from the bottom of the distillation
column and is collected in the sump. The level of the sump is maintained
at 70% while the overflow is drained into the vessel 3101-V04.
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5.HTM & Furnace:-
Processing (esterification or polycondensation) are endothermic
so heat is require for processing we need any source for heat transfer
therefore we use HTM oil we have to achieve >250 centigrade
temperature. The process is very sensitive and a change of even 0.3oC
can cause drastic effects on the process. There should be following
properties of HTM.
1. Low viscosity
2. High thermal conductivity
3. Low freezing point
4. Thermally stable
5. High flash point
6. Non flammable
7. High density
There are two HTM used in IFL.
1. Liquid – Santo therm (PhenylBenzene) is used for primary heating.
The heating of HTM is carried in 3007-F11/12/13
2. Vapor – Dow therm (BiphenylEther) is used for secondary heating. It
have 258 boiling point.
Properties of Sanotherm
Avg Mol weight ~240
Pour point < -10oC
Boiling point 340oC
Auto ignition temperature ~380
Flash point ~170oC
Properties of Dowtherm
Molecular weight 165.76
Freezing point 12.3oC
Flash point 115oC
Boiling point 2560C
Ignition temperature 615oC
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The HTM is heated in a top fired furnace which is fired with the help of
either Natural Gas or Bunker’s Crude Oil (BCO). This BCO is stored in an
1127 vesselfrom whereit is moved to 3007-V03. The level of this vessel
is maintained from 50-80%. Positive displacement pumps are used for
its transfer.
Two furnaces are being used for the heating of HTM vessel. 3007-F01 &
3007-F02. One of these is standby furnace. It must be noted that the
standby furnace in this section is not kept completely out of order. The
furnace in operation is fed at 343 m3/hr. whereas standby furnace
receives 20 m3/hr. of HTM. The temperature of the furnace is 327oC.
In the furnace, Natural Gas is used in the furnace while Santo therm is
used in the coils. Natural Gas enters in a ball valve and then through a
strainer to remove any solid particles and impurities. It then passes
through a Pressure Regulating Valve (PRV). Then it reaches furnace
through a Blocking Tightness Control.
This system consists of two XV valves. The gas through first XV valve
and is closed. The pressure of the gas is measured. If pressure of the gas
does not change then it is sent through second valve for ignition. The
furnace is ignited with the help of LPG when ignited for the first time as
LPG has higher burning value.
The flue gases from the furnace are passed to an economizer which is a
Shell & Tube heat exchanger system for heating the air. Flue gases pass
through tubes while air passes through the shell side. The temperature
of the air is raised up to 200oC before entering the furnace. After
heating, stack gases are emitted into the atmosphere.
HTM is built up in a 3007-V01 vessel and is constantly heated to reduce
viscosity. Its level is checked with the help of a Magnetic Level Indicator.
It is then moved to 3007-V02 vessel at 25 m. If the level of 3007-V01
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falls, then barrels of HTM are charged each weighing 230 kg. The level of
3007-V02 is maintained at 50%. If there are any leakages in the HTM
system, then they are directed to 3007-V04 at 0 m. The lines entering
the furnace are also provided with steam tracing for easy flow and good
atomization of HTM.
In any operation, HTM is used as two systems. In coils as liquid and in
vessel boundaries as vapors. Santo therm is used in the primary cycle
where it is heated in the furnace. This Santo therm then moves in coils
to a secondary cycle where it is used to convert Dow therm into vapor
state in an evaporator. This Dow therm is used in the linings of the
vessel to maintain the temperature of the mixture and to make sure
efficient heat transfer throughout.
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6.Additives
Two additivesused in polyester industry.
1. Titanium dioxide
2. Catalyst
6.1 Titanium dioxide:-
Titanium dioxideis a white powdered solid .In fiber making
process, it is used as dullingagent in the second stage of esterification process.
It is used to make productsof differentbrightness.
For making a semi-dull product, the concentration of TDO in the
solution is 10% and 0.3% by weight of PET in the final product. On the
other hand, a bright product must have 3% concentration of TDO in
solution and 0.03% by weight of PET in the final product.
TDO bags are added through 20 small bags of 25 kg each or 1 big bag of
500 kgin the feeder. TDO is then directed to 1307-V01 vesselwhere it is
agitated for 4 hours. This mixture then moves to 1307-V07 where 1610
L of EG are added. It is again mixed for 1 hour before moving it to
centrifuge (1307-A02). In centrifuge, the concentration of TDO is 18%
and mixture enters at a set point of 452 L. The centrifuge separate
oversize and undersize particles. The coarse particles are produced due
the agglomeration caused by the charges developed due to
agglomeration.
Peelers in the centrifuge remove coarse particles and send them to
1307-V08 and then to the Pearl Mill (1307-A01). Pearl Mill grinds the
oversize particles by using a Muller which has fine particles of
Zirconium dioxide of diameter 0.8 micron. Ground particles form pearl
mill are again moved to 1307-V01 vessel.
Mixture from 1307-V02 is now separated into two lines for making
products of different properties i.e. semi-dull and bright. 1307-V03 is
used for making semi-dull product of 10% TDO concentration. Bright
product is made up in 1307-V04 vessel from where it enters 1307-V05
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vessel in which 4363 L of EG are added to reduce the concentration of
TDO up to 3%.
TDO has followingadvantages for the finalproduct.
1. TDO providesmattfinish to the final product.
2. It increases the durability of the product.
3. TDO also gives hardnessto the product
6.2 Catalyst:-
The process of fiber making is an endothermic reaction. It means that the
energy required to start reaction is high. To lower this energy, called as
activation energy, catalyst is used. Catalyst lowers the activation energy by
associating itself with the reactants which also helps in reducing the residence
time.
The catalyst used is Antimony Triacetate Sb(CH3COO)3 or Di-antimony
Triacetate Sb2(CH3COO)3. It helps the reaction in the stage of
polycondensation which will be discussed later. It is imported in the
form of bags, each weighing 15 kg, from USA. It occurs in the form of
granules and is fed as two catalyst vessels. Antimony triacetate is
imported from USA in the form of white crystalline powder in 12.5 kg
buckets. Active site of catalyst is Sb+++.
1. Feed vessel
2. Catalyst vessel
Solution of catalyst is prepared by mixing filtered ethylene glycol and
Sb(CH3COO)3 in a vessel at a temperature about 75-80oC. The solution is
agitated constantly for 4 hours in the vessel, while 1 hour is provided as
settling time. At the end, an analysis is done to ensure that the
concentration of the catalyst in the solution is 3%. The preparation of
the catalyst solution is done batch-wise. A number of batches of catalyst
solution are prepared to ensure that continuous process of plant does
not stop.
Prepared patch of catalyst solution is filtered and a fixed amount of is
introduced in the paste preparation unit (170-180ppm of catalyst in
product is desired). The amount of catalyst in the final product is so low
that a process for recovery of catalyst is not feasible.
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7.1 Paste Preparation:-
After the preparation of all the raw materials and catalysts, the
process is now taken to next stage of paste preparation in which all the
components are mixed in such a way that they form a paste which is then
further taken to the main reaction vessel
The PTA prepared in the PTA section is stored in day silos. From these
silos, PTA is carried by pressurized N2 to a day silo at 25 m top of the
IFL-1. The mixture is filtered prior to its entry into the silo. In the day
silo, PTA settles down while N2 leaves the silo through nitrogen
discharge system. The PTA then enters a Schenk System which consists
of a motor operated rotor assembly. This system is attached for the
proper distribution of PTA in the paste tank. PTA enters the tank at a
mass flow rate of 7000 kg/hr.
Mono-ethylene glycol from these three lines enters the paste making
vessel which also contains crystalline PTA. The mole ratio of the
reactants is very important. In the paste making vessel the mole ratio of
MEG to PTA is maintained at about 1.12. This ratio is also called E/T
ratio i.e.
𝐸
𝑇
𝑅𝑎𝑡𝑖𝑜 =
𝑀𝑜𝑙𝑒𝑠 𝑜𝑓 𝑀𝐸𝐺
𝑀𝑜𝑙𝑒𝑠 𝑜𝑓 𝑃𝑇𝐴
= 1.12
A solution of catalyst (antimony tri-acetate) in MEG, is present in
catalyst feed vessel 1402-V01. Screw pumps are used to transport the
catalyst solution from the feed vessel to the paste tank. On its way to the
paste tank, the catalyst solution passes through strainers in order to
remove any suspended particles. The preparation of the catalyst
solution will be discussed later in the report.
As the reactants and the catalyst solution enter the paste vessel, they
are agitated with the help of a fix speed agitator. The residence time for
the paste is about 3 hours. The temperature in the vessel is 45oC and the
capacity of the vessel is 29m3. From this vessel, the paste is pumped to
the esterification reactor with the help of screw pumps.
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7.2 Esterification:-
Esterification reaction is the main reaction taking place in
polyester plants. In an esterification reaction, an acid reacts with alcohol to
form ester. In our case, pure terepthalic acid reacts with mono-ethylene glycol
to form Bis-hydroxyethyl terephthalate. The reaction is given as:
2(HO-CH2-CH2-OH) + HOOC-C6H4-COOH (HO-H2C-H2COOC-C6H4-COOCH2-CH2-OH)+2H2O
The paste from the previous section is transferred to the esterification
reactor-1 (ES-1) in which the esterification reaction takes place. It is a
continuous stirred tank reactor (CSTR) which has a capacity of 50m3.
Inside the reactor are spiral coils through which Santo-therm
(Therminol-66) passes and heat the system to about 258oC. Pressure is
maintained at 0.16 bar. The reactor is jacketed and Dow-therm is passed
through the jacket, which heats up the wall of the reactor to prevent
scaling. The agitator provides continuous mixing and improved heat
transfer.
The reaction taking place in esterification reactor is endothermic and
thus the rate of reaction is enhanced at higher temperatures. the
reaction time is about 4 hours and about 90-95% conversion of
reactants into product takes place. Water and MEG vapors emitted in
the reaction are constantly removed and are transferred to the process
distillation column for distillation.
The product formed in ES-1 is then divided into two lines, each line
entering separately in two esterification reactors named as
esterification reactor 2 (ES-2) in each line (14&15). They are coded as
1421-R02 and 1521-R02 respectively. These are also jacketed vessels
equipped with agitators. Spiral coils are present inside the reactor
through which Santo-therm moves and raises the temperature. Dow-
therm maintains high temperature at the reactor walls.
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ES-2 reactors have relatively less capacity than that of ES-1 (11.8 m3).
An important step in the ES-2 reactors is the introduction of dulling
agent Titanium Di-oxide (TDO). TDO is introduced in each reactor
depending upon the level of brightness of product required. Semi-dull
product is produced by introducing 0.3% TDO in ES-2. Semi-dull
product is being made in line 14. Similarly, for bright product 0.03%
TDO is added in ES-2. Bright product is being formed in line 15.Water
and MEG vaporized in each ES-2 reactor is also transferred to internal
distillation column where it is fed at the sump of distillation column.
SEG is obtained from the distillation column.
MEG vapors obtained from ES-1 as well as ES-2 reactors, if contain less
amount of impurities are recovered in a distillation column located
insidethe buildingnamed as process column. It is a 16 plate, bubble-cap
type distillation column which is being operated at atmospheric
pressure. HTM is used for heating. The bottom temperature is
maintained at 180oC and the top temperature is set at 100oC. SEG
obtained from the process column is then fed to the paste vessel.
7.3 Polycondensation:-
When the polymer is formed with the elimination of small
molecule such as water or alcohol then the polymerization is said to be
condensation polymerization. e.g. formation of Polyester. Poly-condensation
reactions are playing important role in modern industries especially their use
in manufacture of synthetic fibers. Polyester is formed by poly-condensation
of Bis-hydroxyethyl terephthalate (BHET). Poly-condensation reactions are
temperature and pressures sensitive therefore a good control over the
reaction conditions is very important. The generation of monomers as well as
controlling the chain length are some important factors in the polymerization
reaction. Our fiber formation process, monomer formed in ES-1 and ES-2 is
transferred to polymerization reactors in which poly-condensation takes
place with the release of MEG vapors. Three polymerization reactors are
present in IFL-1 named as PP-1, PP-2 and DRR (Disk Ring Reactor).Water
formed in polycondensation is removed through distillation.
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Polymerization in PP-1 is carried out at temperature of about 257.2oC.
Heating media is Santo-therm present in coils within reactor while
Dow-therm is present in the reactor jacket. Vacuum pressure of 118
mbar is maintained with the help of vacuum pumps. No agitator system
is provided in PP-1 reactor, although due to presence of vacuum a
swirling movement is induced in the feed. The level in the reactor is
maintained at 35% and a capacitor type level indicator is being used to
measurethe level in the reactor. Duringthe polymerization, MEG vapors
are produced which are constantly being fed to a scrapper condenser in
which liquid MEG (condensed) is showered and MEG vapors are
condensed. A scrapper is present in the condenser which removes any
solid deposited on the condenser surface.
Vacuum is created in the PP-2 reactor and a pressure of about 15 mbar
is maintained. Pre-polymer solution from PP-1 is brought to the PP-2
reactor. An agitator is employed in PP-2 for proper mixing, as the
intrinsic viscosity of the mixture increases. The temperature is
maintained at 259.7oC and the level in the reactor is set at about 35%.
The level in PP-2 reactor is measured by capacitor system as well as
radio-active level measuring system. MEG vapors produced in PP-2 are
removed and condensed by a jet system discussed later in the report.
The mixture from PP-2 is then filtered in candle type filters and is then
transferred to the final poly-condensation unit (DRR).
DRR is a horizontal plug flow reactor operated at about 282oC and a
vacuum pressure of about 0.8-1.4 mbar. A horizontal agitator having
discs is used for proper mixing. The level in DRR is maintained at 31%
and is measured using radioactive level measuring system. Molecular
PET is poly-condensed to high molecular PET in the final poly-
condensation reactor. In DRR, pre-polymer is brought to its final
viscosity and properties. Intrinsic viscosity is used to as a parameter for
determining the chain length. The degree of poly-condensation and thus
viscosity is set to the desired final value by maintaining vacuum,
temperature, agitator speed and residence time at an appropriate level.
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Ethylene glycol vapors produced during poly-condensation in PP-2 as
well as DRR are removed from these reactors and condensed with the
help of a jet system. In jet system, blast EG is passes through a jet to
which both PP-2 and DRR are attached. Vapors of MEG produced in
these reactors are taken to the jet. This blast EG then enters a 3-stage
condenser system in which condensed MEG is being showered.
Vaporized MEG enters the first condenser where some part of it is
condensed. It then enters the 2nd cooler where again some part of it is
condensed. It then enters the third condenser and further condensation
of vaporstakes place. By usingthis condensation phenomena, vacuum is
created and maintained in PP-2 and DRR. The remaining un-condensed
vapors are then vented to the atmosphere.
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8. Spinning Section
8.1 Spinning Discription:-
Melt polymer at the temperature of 285-289oC comes from poly-
condensation plant through insulated pipe. The melt polymer is heated
through HTM (therminol). The temperature of polymer is controlled by
HTM used in pipes co-currently.
In IFL-1 this polymer come in five simultaneous beams each beam
consist of six packs which sums up to 30.contacted to gear pumps.
Because of viscous liquid we use this pump at fix RPMs to through melt
polymer in spin packs. Each pump have its own pack which through
melt into spinnerets .Below each pump, there is spin pack.
On top of spin pack, a plate is kept containing 3750 holesin IFL-1. Outer
diameter of each hole is 0.25 micro meter. Pressurized molten polymer
at 288Centigrade and 70 bar is passed through the plate.
Holes are in radial formation. There is fiber formation. These fibers are
at 288Centigrade temperatures. The molten polymer is pressurized so
that fiber formation can be given to it.
Throughput for semi dull is 98 ton/day and for bright is 95 ton/day.
Each pump is controlled by attached reducer. It controls the speed of
pump. It also increases torque.
8.2 Pumping of Melt:-
Five beams assembly which contain six gear pumps in each beam used
to pump the melt toward the spin pack. Gear pumps are used for the
pumping of viscous liquids and it is the type of positive displacement
pump.
There are 2 lines in IFL 1 each line contain 30 pumps . the rpms of each
pump is fixed to produce a pressure of 70 bars and for the proper
distribution on melt in each spin pack.
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8.3 Formation of Fiber:-
The melt from each gear pump is pump toward the spin pack this is the
portion from where the formation of fiber take place after the series of
operations. Spin pack is circular assembly contain spinneret.
Spinneretcontain 3750 holeswith the outer diameter of
0.25micrometer. meltpenetratethese hole and tae a shape of fiber after
the formation of fiber the temperatureis reduced suddenly by usingthe
quench air.
8.4 Spin wall:-
Spin wall is an importantoperation in spinningsection. In spin
wall there are differentfunctionsdoneby differentpartsas given below in
detail:
a) Slub catcher
b) Slot oiler
c) Convergenceguide(v guide)
d) Suction cutting device( nozzleand cutter)
e) Drip detector
f) Deflector roller
g) Supportguide
h) Entanglingdevice
i) Dia-bolo rollers
j) Finger guide
k) Rollers
l) Sun flower
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It is a device used to fix positions of filaments. It is used to catch drip in
the sub-tow coming from spin pack. Before thread oiler devices, there is
ceramic coated rod called slub coater, which holds the filaments bundle
for each position. Each position is provided with suction and cutting
device, as is used to cut the position as per requirement and waste
through hose pipe at the back of the wall. Suction cutting device is
operated at air pressure of 6 bars.
Spin finish oil is showering on the sub-tow coming from the slub catcher
to make it friction free and antistatic to avoid dripping. The distance
between slub catcher to slot oiler is 190mm. After solidification, the
filaments pass through the ring oiler device. The oil is applied to
filaments in order to maintain 30% moisture content. Ring oiler device
also applies S.F. Oil to the filaments in order to remove the static charge.
V-guide is used to guide sub-tow towards suction and cutting device, it
makes sub-tow handling feasible for suction and cutting device.
Distance of v-guide to thread oiler is 160mm.
When drip is detected in drip detector, cutter used to cut sub-tow and
the remaining sub-tow is sucked on the principle of ejector through
suction device. Distance between v-guide and suction device is 50mm.
When drip is detected in drip detector cutting device is used to cut the
sub-tow line coming right from the slub catcher. Distance between
suction device and cutting device is 50mm.
If there is drip in the sub-tow line is detected, drip detector detects and
generates a signal toward alarm. Distance between drip detector to
cutting device is 100mm. clearance of drip through drip detector is 0.5
mm. The filamentsthen passed through drip detector. Whenever drip or
plastic comes with filaments, it operates the drip detector and signal
comes at the local panel with alarm.
Then the filaments are deflected from vertical to horizontal direction
with deflector roller. The deflector rollers are un-driven and one
deflector roller is for one position. These filaments are guided with
ceramic coated guides. The filaments are gathered from each position in
the form of sub tow. Then the sub tow travels at godet rollers and
sunflower unit and collected into two at can traversing area.
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Sub-tow comingfrom the drip detector is deflected towards the dia-bolo
rollers. These are used to change the vertical position to horizontal
position of sub-tow. Distance of deflection roller to drip detector is
115mm.It is used to provide stretch to the sub-tow to make it part of
already or continuous running sub-tow.
It used to align the new sub-tow with the continuous running sub-tow
by providing a 6.5 bars pressure. These are used to change the direction
of continuous running sub-tow towards the finger guide. They are free
to move therefore they have highest rpm in the spin wall.
It is used to provide the sub-tow adjustment on the motor operated
rollers. The six motor operated rollers are used to draw sub-tow from
spin walls. Size of each roller is 0.5mm higher than its preceding roller.
Sunflower rollers are used to nip the sub-tow towards the cans in those
sub-tows is filled. There are teeth on the rollers which are used to nip
the sub-tow.
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9. Quench air section:-
As concern with quenching of air, the blowers in quenching section
picks up air from spinning section which is actually comfort air at a
temperature of 30-35oc.
After this a part of this air about 30% exhausted and in other part called
dampers fresh air is entered at same amount 30%. In winter season
environment temperature is 20-25oc, in this situation we take 100%
fresh air from environment and the dampers are automatically closed.
These dampers twirled automatically which are adjusted with humidity
factor.In summer season these dampers operated automatically.
This air send to the bag filters which removes dust particles from air.
There are some steam coils which heats up air in winter season as per
required our required temperature. after this some dust particles
remain in the air which is removed by another section which is washer
tank. In washer tank water mixed with some chemicals, air enters and
passed.
Washer tank contain a rotary tank which picks up all dust particles.
After this air is cooled for further process cooling coils are used which
contain chilled water which comes from utility section. After this
process air is cooled approximately 18-20oc, then this section divided
into two lines one is of comfort air and other one of quench air. Because
quench air is used for cooling of polymer which require more efficient
and must be dust free for this again this air passes through bag filters
which removes dust particles from air. This air through a duct reaches
to the spin packs to cool the polymer.
When quench air comes in contact with polymer its temperature is
about 20oc. this air is humidify at 85%, because of little residence time
of air with melt high amount of air must be there for their proper
solidification. After solidification the temperature of air approximately
50oc. this air exhausted through a duct. If our humidity level is lower
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than as given above after solidifying the melt air temperature reaches at
150oc which is inefficient process.
Quench air temperature is important factor, if temperature is increases
then in draw line desired properties cannot be achieved. Another
important factor in quenching is uniformly distribution of air to all
filaments, in case proper supply of air and velocity of is most important.
There are 15 lines of holes in spinneret if velocity is lower than the last
one lines will not solidify as we need therefore 2.50m/s velocity is
efficient for proper heat transfer. If air velocity is high then this can
cause filaments fuse with each other.
Blower(comfor
t air)
dampers
Bag filter
Washer tank Cooling coils
Comfort air
duct
Ste
am
coil
s
Chilled water
Quench air
duct
Bag filter
Spinnig
section(quenc
hing)
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10. CTR:-
Can contains sub-tow coming from spinningsection also called as UDY
(undrawn yarn).
Followingare the operations which are existing in the CTR.
1) Conveyer whichcarries the cansis called as carriage.
2) The motion of carriage is controlled by synchronization strip. It is also
called as brain of carriage.
3) Sensors are used to definethe intake and outtake boundary of can and
generates a signal to the synchronization strip.
4) Weight of an empty can is 1 ton.
5) Capacity of can to carry weight is 5-5.5 ton.
6) One can is filled in 58 minutes.
11. Auxiliary section:-
Auxiliary section in polymer section is an important part. In this section
spinneret pack which are used to convert to polymer into fiber is repaired or
reassemble. The parts of spin pack which are assemble are given below:
a) Housing
b) Filling ring
c) Ring distribution
d) Perforated plate
e) Cover
f) Spinneret
g) Supportring
h) Filters ( 5 & 3 fold)
i) Gas kits (small & large)
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11.1 Cleaning of spin pack parts:-
In TEG tank five chocked spinneret placed in tank at a temperature of
270oc for 16hours. After this these spinneret withdraw from tank sunk
in 5% NaoH solution bath for 1hour then these spinneret placed in
other tank of demineralized water. After this cleaning spinneret are
cleaned but somehow there holes may blocked, for this we placed it into
weave bath. Now this spinneret is go for inspection which is done by a
machine on computer. All the holes of spinneret inspected, if found any
blocked hole then operator with the help of air or with needle cleaned it
out.
Other parts of spin pack like housing, distribution plate, cover etc are
cleaned in another section called vacuum pyrolysis. Firstas all spin pack
disassemble then spinneret send to TEG section and other parts are
placed in vacuum pyrolysis where at -0.5 to -0.7 bar and at temperature
of 450oc for specific time at which cracking of polymer takes place. Then
these parts washed with demineralized water for there further cleaning
by using max power as a detergent.
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12. Textile lab
Manufactured fiber can be tested in textile lab, followingtests are
tested as:
a) Denier
b) Tenacity
c) Elongation
d) Crimp no
e) Crimp removal
f) Shrinkage
g) Electric resistance
h) O.P.U
i) Miscut
j) Fiber length
k) Deep dyeeffect
l) Moisture
m)Colors(L & b)
n) Bulk density
Now we are going to explain these tests one by one on the basis of their
operating functions.
As we have taken different samples from different lines like 71 & 73. As
denier given by per line lab attendant check its denier with the help of
vibroscop.These two terms also tested with help of viscometer.
Crimp number of selected fiber found as, fiber attached with scotch tape
then with the help of microscope find its crimp number. A fiber of
denier 1.4 must have crimp number 12-13 inches.
Weight attached to the fiber and we find its length after and before
attaching weight in this way we find its crimp removal it must be >15%.
In this process we take our sample into oven for 20 minutes at a
temperature of 180oc.
For this we use static voltmeter, sample 2g is taken and current of 150V
passes through it, if its resistance is less than 1*1011 ohm then this fiber
is good to use.
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In O.P.U test we take 5g sample in flask which contain 40% solution of
methanol and place it in a heating medium and did this process for 20
minutes after this take out flask and place in oven at 120oc for 20
minutes.
Then this sample place in desicator after this due to weight difference
which is being measured after and before this process we found out %
of oil absorbed in the oil which must be from 0.130-0.140%
This length is checked is checked with the help of slap glass, two points
of fiber connected with scotch tape and with the help of scale we found
out our required length given by process section.
In this test Illuminesweaving plate is used for test which is connected to
electric supply. Fiber placed between plates then if the fiber is hard
colored its stretching is not possible this is called deep dye effect.
5g of sample taken and weight it. Then this sample placed in oven at a
temperature of 60oc for 1 hour, after this weight it then we found the
%moisture by using formulas, its maximum rang 0.39 %.
13. Utility section:-
In utility section operations are performed given as below:
1. Water treatment
2. Cooling water
3. Chillers
4. Boilers
5. Nitrogen compressors
13.1 Water treatment:-
Water is a major need of industry. Asweknow, in IFL plantscanal water
is not available therefore weuse ground water here.. On the other hand
ground water contain TDS(total dissolved solid) which are not easy to
remove. Conductivity of water in Faisalabad is about3000-3300μS.
Initially we are tried to reduceconductivity of this water.
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Ground water is pumped through 3 turbines & stored in an overhead
tank with a capacity of 5300 gallons then supplied to Water Treatment
Plant for purification. Two pumps pump the water to the top of the two
multilayer filters, which have beds of sands, having three layers of sand
of decreasing particle size. These filters are used primarily to remove
the suspended particles from the raw water.
After filtration dozing of water is donein a tank. For dozing 33% HCL is
added in filtered water through control valve. Heredozing is done justto
maintain PH of water at 6.3. HCL react with carbonates and removeits
hardness, thereaction are given as below:
HCl + CaCO3 CaCl2 + H2CO3
HCl+MgCO3 MgCl2 + H2CO3
H2CO3 +Air H2O + CO2 +Air
The filtered water at a pH 6.3 is passed through candle filters called as bag
filters. The water is then pumped through multi-impeller pumps, which
generate 25-bar pressureoutput, which is used as a feed for the Reverse
Osmosis unit. In the RO unit we have 6 banks in which filters are fitted.
Here almost 70% of the water passes through the cellulose membrane
whoseconductivity is very low (100 μS), called as Permeate.
The remaining 30% water whoseconductivity is very high (10,000-11,000
μS) is disposed off. The softwater is sent to the hydro-cyclones wherethe
air is blown with the help of a blower, which after absorbing CO2 fromthe
water is discharged to the atmosphere. Here 80-85% of CO2 is removed &
water is sent to the storagetank. Here softwater used in process section,
cooling towers, and in chillers. But in boiler only demineralized water is
used.
13.2 Cooling tower:-
In cooling tower water is cooled up to 25-30oc. Soft water from process
pump to cooling tower section at 35oc. the basic working principle of
cooling tower is the hot water through from the top of cooling tower as
shown in the figure below.
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This hot water comes down and air from lowers enter cooling tower,
when air and water comes in contact with each other evaporation
process carried out, and we know evaporation causes cooling effect.
This Air picks up high energy molecules and with the help of fan at the
top sucks it to environment.
At the inner side of lowers there are fillings which prevent the
splashing or loose of water. At the bottom of the tower there is slumn
which collects the cooled water. This water send to operation with the
help of pump and water recycle again.
As we know this is not demineralized water therefore there is definitely
chance of attach of fungus and turbidity. To remove it we add some
chemicals in it with their trade names. We maintain level of water in
slumn in cooling tower. In any case if some water loose in splashing and
in evaporation then at the bottom there is vent which is called as make
up water. Its function is to fulfil level.
Fan on the top is motor driven at fix RPMs. RPMs of fan play an
important role in cooling. Its RPMs will be change under environmental
consideration, and it also depends upon wet or dry bulb temperature,
cool water the at lower RPMs of fan rather than if difference is lower.
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13.3 Chillers:-
Chillers are used to chill the soft water. In IFL water is chilled
up to 6-7oc. The chilled water circulates in the plantthrough a closed loop. The
water returnsto the chillers at a temperatureof 11-12oC. Wehavethree
Water Cooled Centrifugalchillers of 2000 kW coolingcapacity. The chilling
operation is like a refrigeration cycle. It has mainly 4 parts given as below:
a) Evaporation
b) Compression
c) Condensation
d) Expansion valve
In evaporation shell & tube heat exchanger is used, wherechilled water
on tube sideand refrigerant is n shell side. The WC (chilledwater)
stream from the process(11-12oC)entersthe evaporator in the tubes &
is discharged at a temperatureof 6-7oC. It is present in the liquid form
& when the WC stream passes through the evaporator tubes, the
refrigerantgets heat from the water and evaporates.
After this it send into compression chamber. The compressor should be
of such capacity that it should intake same amountof vaporsfrom the
evaporator as being produced in it if the capacity is low then the
pressurein the evaporator will increase & thus the saturation
temperatureof refrigerantwill increase. When the vaporsare
compressed their temperature& pressureincreases.
After compression this water is send into condensation chamber where
cold water is on shell side for cooling purpose.Herethe vaporsare
discharged at the same pressurebut at lower temperature& sent to the
economizer.
A nozzleis fitted in the economizer, which acts as an expansion valve.
Here the vaporsaresprayed so their pressuredecreasesdueto sudden
expansion cooling occurs& most of the vaporsgo to liquid form. From
the economizer these streams are discharged.
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compression
condensation
evaporation
Evaporation
Valve
13.4 Compressor:-
Compressorsareused to increase the pressureof a gas. Compressorsare
very importantin industry becauseat many places in processwe require
air at pressurehigher than the atmospheric pressure. At IFL, the purposeof
installing a compressor is,
1. For nitrogen generation
2. For PTA charging
Screw typecompressorsare used here in positive displacement types of
compressors. Five double stage screw type compressors are installed
here of capacity 1339 m3/hr, having maximum working pressure 10.5
bar. One compressor is used for normal consumption, and one is stand
by, whereas remaining are used depending upon load. There are also
four air refrigerant driers.
Double stage screw type compressor takes air from the atmosphere. This
air is pre filtered and then it passes through intake filters in order to
remove dust and other suspended impurities. In first stage, this air is
compressed to 2.7 bars, its temperature rises to 240oC. This
compressed air passes through intercooler (Shell and tube type), where
water is used as cooling media.
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Temperature of air falls to 35oC. Now it passes through the second
stage, where it is compressed to 9.5 bars and its temperature rises to
245oC. It is passed through after cooler where water is used as cooling
media and temperature of air becomes again to 30oC. Now this
compressed air at 9.5 bars and 30oC enters in air refrigeration dryers.
This air enters into an evaporator, where moisture of air condenses by
giving its heat to refrigerant causing it to vaporize. The condensed
moisture is drained off. This moisture free air enters again in air to air
heat exchanger, where it takes heat from the incoming compressed air.
The vaporized refrigerant is compressed in reciprocating compressor.
This refrigerant enters the condenser where water is used as cooling
media. This condensed refrigerant is again ready for moisture removal
in evaporator.
The compressed, dried air is stored in compressed air storage. From the
supply of compressed air to process; one stream is taken into the
instrument air dryers. They contain two cylinders filled with
hygroscopic compound (Al2O3). One cylinder operates at a time, when
its pressure becomes high and temperature becomes low and it
becomes saturated, its pressure falls and refrigeration occurs.
Meanwhile, at the same time other cylinder become active and prepares
instrument air. The instrument air produced is stored in vessel.
13.5 Boilers:-
The boilers are used for the production of steam, which is then used on
many typesof equipmentsin the plant. The basic consumption of steam is
in the fiber draw line, heavy furnaceoil & polymerization section. There
are basically two types of boilers,
i. Fire Tube Boilers
ii. Water Tube Boiler
Three fire tube boilers are used in the IFL. One is stand by while 2 are in
operation.
Fuel for boiler:
i. Natural gas (mostly used)
ii. Furnaceoil (stand by)
The steam condensate (70%)returningfrom the plantcomes to the feed
water tank wherea de-aerator is also attached to removethe air from
the steam condensate. In this vesselchemicals are added to condensate.
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i. Hydrazine -for removalof free oxygen
ii. Caustic soda - for maintaining pH
iii. Ammoniagas - also added for maintainingpH
After the feed water tank the condensate is pumped by two pairs of
pumps (one pump of each pair is standby) to the boiler. The condensate
along with 30% de-mineralized water enter the boiler on the shell side
and converts to the vapors form by heat transfer from the fire entering
from the tube side. The level of water in Boiler is 2/3 of total volume of
boiler. The steam from the boiler then enters the super-heater at 25-bar
pressure and the steam form the super-heater exits at about 250oC.
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13.6 Nitrogen Generation :-
Nitrogen required for the processmust be at high pressureand low
temperature. Nitrogen produced at IFL is classified into followingtwo types.
i. Technical nitrogen
ii. Purenitrogen
13.7 Technical Nitrogen Unit
NT is produced in a pressureswingadsorption unitconsisting of
1. Air compressor
2. Chilled water air cooler
3. PressureSwing Adsorption (PSA)Unit
A two stage air compressors giving compressed air at a pressure of
about 8 bar. Currently unit is operated is at external supply.
Compressed air passes through pressure relieving valve where its
pressure reduces from 9.4 bar to 8 bar. This air then passes through
chilled water cooler. The water supplied lowers the temperature from
30oC to 12oC, also moisture trapped is removed. This air is transferred
to Buffer Vessels containing cyclones, which remove moisture.
Air from the buffer vessel, reaches adsorber-1 through the bottom and
flows through the carbon molecular sieve bed. During this process the
oxygen of the process air is adsorbed that is attached to the CMS at a
high pressure and low temperature. The nitrogen reaches into technical
storage tanks
Downstream of anti-storage tanks tubing, takes sample gas to the
analyzer for the measurement of O2 contents in the NT produced. The
NT flows to the storage vessel or to the atmosphere depending on its O2
contents. If O2 contents exceed the set point, then N2 vents to
atmosphere. If O2 contents are within a range, then it flows to NT
storage vessel. The regeneration process is of 1 min cycle.
First pressure equalization occurs of both absorbers then the absorber
to the regenerator releases adsorbed O2 to the atmosphere and the
other come in operation to absorb oxygen. The NT producefrom plant A
and B is stored. The NT produce must contain O2 <1%. The production
of NT takes place at a rate of 195 m3/hr. in each section.
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13.8 Pure Nitrogen Unit
It also contains 2 units. Each stream is divided into further two streams;
one for each plant. There are two hydrogen cylinders for each plant.
A highly exothermic reaction occurs, forming N2 and H2O vapors. The
reaction of hydrogen and oxygen occursat 195oC and in the presenceof
Palladium used as catalyst in a De-Oxo Reactor. The reactors maximum
allowable pressure is 13 bars and maximum allowable temperature is
240oC.
This stream containing NP and water vapors is passed through finned
type heat exchanger to lower its temperature. It is cooled down in the
exchanger resulting in the condensation of water vapors releasing NP.
The production of nitrogen is 10 m3/hr.
14. Draw Line
In this unitoperation section the UDY(undrawn yarn)isconverted
into DY(Drawn yarn)withphysicalproperty change
In this area the can are placed and the sub tow is used to form a larger
tow. 25 cans are being used in each line at same time. The formed tows
are arranged and guided on rollers. Tow is dipped in dippingboth which
contain SF oil. Tow is dipped to achieve uniform temperatureof 24C and
pre-lubrication of tow to avoid slippage and entangle.
The draw frame is used for the drawing of the polymer along its length.
In which first roller is also attached to a nip roller to drip off spin finish
oil from the dipping bath. The treatment of the tow starts here. The
roller speed is kept 62 m/s approximately this is first stage drawing
which is also called soft drawing. This is a closed tank where the spin
finish oil at 80oC is showered on the tow. The steam in the plate type
heat exchanger heats the spin finish oil.
This is the second draw frame present in the fiber line. It has 7 rollers
having a rotational speed of 198.5 m/min. Therollersof this draw frame
are provided with steam at 95oC to heat them. The drawing is done at
glass transition temperature 79oC. At glass transition temperature, the
drawing of fiber is done maximum.
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Between DF-II and DF-III, steam is showered to achieve rest of 13%
drawing. In DF-III, rollers speed is 235m/min. In this chamber the
properties achieved by the tow are stabilized. It has 12 rollers and is
divided in to two parts each containing 6 rollers. There rotational speed
is 234 m/min. The temperature of tow is kept about 207oC.
This unit consists of seven rollers rotating at 232 m/min. The purpose
of the DF-IV is to grip the tow and make a speed control for the next
units. This unit overlaps the three tows used in the drawing & forms a
single tow whose width is comparable to the width of the crimper
intake.
The unit maintains the tension of the roller & again sent to the steam
unit to gain the cotton like property. Now tow is crossed through the
crimper unit. This unitinduces crimps on the fiber at a rate of 14 crimps
per inch. The crimps are made for necessary fiber flexibility & cohesion
The tow leaves via traversing unitwhere spin finish oil is sprayed on the
crimp tow depending on the type of product. The traversing chute
spreads the tow on the tow drier plate. In this section the tow is dried &
cooled. 10-bar steam is supplied for the heating zone.
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15. Cutter & Baler
Fiber tow formed in spinningis at high temperature. It should be cooled,
before it is sent to baler and cutting section. Fiber from dryer, moves on
chain. In chain there are small holes on chain through which air from
atmosphere is sucked by pump. This air cause cooling of fiber.
There may be knots in tow which may damage cutter. Two rollers above
another are used in assembly line. As they passes through them , one
roller will rise which give alarm. This knotwill be cut down by operator.
To grip the tow, two rollers are used. These are assembled one above
another. They are also called gripper.
The tow coming from tension roller will wind around the cutter. The
cutter is circular which contain blades on edge in circular form. These
blades will cut down the tow.As tow is cut down, the fiber will fall down
on plate that is called free pin. This will be close when plate below it will
be opened.
As plate of freepin falls down, it will be collected wear pin. This plate
weight the fiber. Upon 50 kg batch , plate will be opened. Fiber is
pressed in pushpin section. 300 kgpressed batch is prepared. Thisis
packed in polypropylene.
49. Polyester Plant 2014
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16. SAFETY PRECAUTIONS
In order to avoid the hazards on the plant, company train its employees for
the safe handling and operation of materials and units installed on plant
Smoking is strongly prohibited on all areas of the plant because at
different places different flammable materials are under process and some
leakages may occur and so serious damage can occur.
Over speeding is prohibited on the roads because staff is always
crossing the roads and also tanks with explosive materials are present
at different places and anything hitting them may cause a serious
danger.
Mobile phone is not allowed in plant area because electromagnetic
waves may disturb the sensitive control system. For the training of
internees, schedules are issued that means that for every unit some
guider is provided for the specific period of time and we are not allowed
to go in any area according to our desire.
