INTERNSHIP REPORT

IBRAHIM FIBRES LIMITED

Polyester Plant

SUBMITTED BY:

MUHAMMAD IRFAN SHAHZAD (04-POLY-34)

HAFIZ MUHAMMAD ASGHAR ALI (04-POLY-45)

B.Sc. Polymer & Process Engineering

UET, LAHORE

1

Misbah Ahmed Qureshi

2K5-CHEM-152

B.Sc. Chemical Engineering

NFCIET, Multan

Table of Contents

PLANT CAPACITY................................................................................................................................................................... 5

PLANT START-UP..............................................................................................................................................................5

SAFETY PRECAUTIONS........................................................................................................................................................6

UTY PLANT................................................................................................................................................................................ 7

Utility Section........................................................................................................................................................................... 8

WATER TREATMENT PLANT......................................................................................................................................8

CHILLERS.............................................................................................................................................................................. 9

COMPRESSORS................................................................................................................................................................ 11

Process Design............................................................................................................................................................12

2

Cooling Tower.................................................................................................................................................................. 13

BOILERS.............................................................................................................................................................................. 14

NITROGEN GENERATION...........................................................................................................................................15

TECHNICAL NITROGEN UNIT..............................................................................................................................15

PURE NITROGEN UNIT...........................................................................................................................................16

Polymer Section....................................................................................................................................................................17

Raw Materials...................................................................................................................................................................17

PTA (Pure Terephthalic Acid)..............................................................................................................................17

MEG (Mono Ethylene Glycol)...............................................................................................................................18

HTM Section...................................................................................................................................................................... 19

EGR (Ethylene Glycol Recovery) Section..............................................................................................................20

Paste Preparation........................................................................................................................................................... 22

Esterification.................................................................................................................................................................... 23

Polycondensation........................................................................................................................................................... 24

PP-I (Pre-Polycondensation-I)............................................................................................................................25

PP-II (Pre-Polycondensaton-II)...........................................................................................................................26

DRR (Disc Ring Reactor)........................................................................................................................................26

SPINNING.................................................................................................................................................................................28

Definition:.......................................................................................................................................................................... 28

Introduction:.....................................................................................................................................................................28

Description:....................................................................................................................................................................... 28

QUALITY CONTROL:......................................................................................................................................................30

SPIN PACK REGENERATION......................................................................................................................................31

TEG SECTION.............................................................................................................................................................. 31

Ultrasonic Bath...........................................................................................................................................................31

AIR DRYING DEVICE................................................................................................................................................32

SPINNING AUXILIARY:............................................................................................................................................32

PACK ASSEMBLING.................................................................................................................................................. 32

3

FIBRE DRAW LINE.............................................................................................................................................................. 33

Creel area........................................................................................................................................................................... 33

Y02 tow formation unit:..............................................................................................................................................34

Y03 tow guiding frame:................................................................................................................................................34

Y04 Dipping Bath:...........................................................................................................................................................34

Draw frame 1:...................................................................................................................................................................34

Draw bath:......................................................................................................................................................................... 34

Draw Frame II:.................................................................................................................................................................34

Thermosetting Unit:......................................................................................................................................................34

Tow Cooler:....................................................................................................................................................................... 34

Draw Frame IV:................................................................................................................................................................35

Over lapper & Three Roller Frame:........................................................................................................................35

Tension roller:..................................................................................................................................................................35

Crimper Unit:....................................................................................................................................................................35

Traversing Unit:.............................................................................................................................................................. 35

Tow Drier:.......................................................................................................................................................................... 35

Bailing & Cutting............................................................................................................................................................. 36

Cutting operation:.....................................................................................................................................................36

Bailer:............................................................................................................................................................................. 36

Spin Finish Oil Preparation:.......................................................................................................................................36

4

PLANT CAPACITY

The plant has two units, IFL1 and IFL2 line no. 14 and 15 are for IFL1 and can produce up to 196 tons/day. Line no 17 is for IFL 2 and it can produce 400 tons/day.

PLANT START-UP

1. IFL1;

Line no. 14 26 Feb.1997

Line no. 15 29 Dec.1996

2. IFL2;

Line no. 17 02 June, 2002

5

SAFETY PRECAUTIONS

In order to avoid the hazards on the plant, company train their employees for the safe handling and operation of materials and units installed on plant. So for this company follow following steps

Give knowledge

Give training

Trouble shooting

Authorization

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Even a small mistake on the plant can cause a serious damage so MMM (man, machine, material) is very important.

Smoking is strongly prohibited on all areas of the plant because at different places different flammable materials are venting out and also 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.

Running is also banned because it may divert the attention of workers and as a result, their work may be ignored.

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.

Yellow marks are there on the steps that are odd as compared to other to prevent injury of workers.

Yellow borders are also provided in front of computer control systems to prevent the tripping of systems as they are very sensitive.

Treated water is provided for the workers for their better health as water in that area is of very high conductivity.

Environment is made green in order to provide better environment for the workers.

MSDS (material safety data sheets) are provided with every material for the safe handling and storage of the materials.

SOPs (standard operating procedures ) are provided for the safe operations.

Remedial measures

Different water, gas and sand exhaust systems are provided for overcoming fire.

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CHECKED BY

UTY PLANT

UTILITY SECTION

In this section all the utilities supplied to the process are maintained, e.g. steam water, demin water, compressed air, chilled air, cooling water, soft water, de-mineralized water etc.

The utility section is composed of six areas

Water treatment plant (1 & 2)

Boilers

Chillers

Cooling towers

Nitrogen generation

Compressors

For all these supplies water is the major requirement, which is pumped from ground. The conductivity of the ground water is very high i.e. 3300-3500, so the water is treated initially to reduce its conductivity in the water treatment plant.

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WATER TREATMENT PLANT

In this plant the ground water is treated through physical & chemical processes to make it useful in the processing.

The water is pumped from the depth of 350 ft through 3 turbines & stored in an overhead tank with a capacity of 5500 gallons. 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.

The filtered water is then passed through an HCL dosing unit where its pH is maintained at 6.3 by dosing 33% HCL through a control valve. The HCL reacts with the carbonates & thus removes the hardness. The reaction occurring here is as follows,

HCl + CaCO3 CaCl2 + H2CO3

H2CO3 H2O + CO2

The filtered water at a pH 6.3 is passed through candle filters also called as bag filters. The water is then pumped through multi-impeller pumps, which generate 25-bar pressure output, which is used as a feed for the RO unit.

In the RO unit we have 6 banks (lines) in which fine spiral filters are fitted. Here almost 70% of the water passes through the cellulose membrane whose conductivity is very low (i.e. 100

S), called as Permeate. The remaining 30% water whose conductivity is very high (i.e. 10,000-μ11,000 S) is disposed off. The soft water is sent to the hydro-cyclones where the air is blownμ with the help of a blower, which after absorbing CO2 from the water is discharged to the atmosphere. Here 80-85% of CO2 is removed & water is sent to the storage tank.

The permeate is soft water which is then divided into three lines

To the cooling tower as a make up stream

To the process

To the mixed bed for De-mineralization

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Then the soft water is treated through a mixed bed ion exchange process in a De-mineralizer where we get the water whose conductivity is less then 1 S. This water is called De-mineralizedμ water.

The soft water is also used to make a drinking water, so a soft water line is passed through a re-mineralize to add necessary minerals (Ca-hydro lit) in the water to make it potable .The drinking water is then sent to the storage tank of 5 ton capacity.

CHILLERS

This unit is used to cool the temperature of the water to 6-7 oC .The water is cooled by passing through the chiller. The chilled water circulates in the plant through a closed loop. The water returns to the chillers at a temperature of 11-12 oC. The chilling operation is like a refrigeration cycle. It has mainly 4 parts.

Evaporator

Compressor

Condenser

Expansion valve

The evaporator is basically shell & tube heat exchanger in which the chilled water is on the tube side & the refrigerant (R-134a) is on the shell side. The heat exchanger used here is a 1-2 pass heat exchanger. The wcc (chilled water) stream from the process (11-12 oC) enters the evaporator in the tubes & is discharged at a temperature of 6-7 oC. The boiling point of refrigerant is –26 oC. It is present in the liquid form & when the wcc stream passes through the evaporator tubes, the refrigerant gets heat from the water and evaporates.

The vapors of the refrigerant are sent to the two-stage compressor. The compressor should be of such capacity that it should intake same amount of vapors from the evaporator as being produced in it if the capacity is low then the pressure in the evaporator will increase & thus the saturation temperature of refrigerant will increase. When the vapors are compressed their temperature & pressure increases (approx 45 oC).

The compressed stream is sent to the condenser in the tubes, where cooling water is circulated for the cooling purpose in the shell side. There are two types of condensers on the characteristics of the cooling medium.

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o Water-cooled condenser

o Air-cooled condenser

For large capacity systems water-cooled & for the small capacity systems air cooled condensers are used.

Here the vapors are discharged at the same pressure but at lower temperature & sent to the economizer. A nozzle is fitted in the economizer, which acts as an expansion valve. Here the vapors are sprayed so their pressure decreases due to sudden expansion cooling occurs & most of the vapors go to liquid form. From the economizer these streams are discharged.

To the evaporator (in liquid form)

To the evaporator (in the vapor form)

To the 2nd stage of compressor as an inter cooler (in vapor form)

COMPRESSORS

Compressors are very important in industry because at many places in process we require air at pressure higher then the atmospheric pressure. The purpose of installing a compressor is

For the generation of the instruments air which is used to activate the instrument valves

To supply air for cleaning purposes

For resin mixing

For nitrogen generation (if required)

For PTA charging

There are two types of compressors

1. Centrifugal compressors

2. Positive displacement compressors

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Screw type compressors are used here in positive displacement types of compressors. Five double stage screw type compressors are installed here (K01, K02, K03, K04, K05) of capacity 1339 m3/hr, having maximum working pressure 10.5 bar , rational speed 1485 r/min.

One compressor is used for normal consumption, and one is stand by, where as remaining are used depending upon load. There are also four air refrigerant driers of capacity 1952 m3/hr. Two types of air is produced here having following specifications.

PLANT AIR: 9.5 bar, 35 oC, Dew point < 4 oC, Dust content < 1ppm,

Oil content < 1ppm

INSTRUMENT AIR: 6 bar, 35 oC, Dew point < -20 oC, Dust content < 1ppm,

Oil content < 0.01ppm

Air compression cycle

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PROCESS DESIGN

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 bar, its temperature rises to 240 oC. This compressed air passes through intercooler (Shell and tube type), where water is used as cooling media. Temperature of air falls to 35 oC. Now it passes through the second stage, where it is compressed to 9.5 bar and its temperature rises to 245 oC. It is passed through after cooler where water is used as cooling media and temperature of air becomes again to 30 oC. Now this compressed air at 9.5 bar and 300 oC enters in air refrigeration dryers.

First of all it passes through an air to air heat exchanger, so that its temperature falls down. Now 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 compressed refrigerant passes through oil trapper to become oil free. This oil free 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 (4300-v01). From the supply of compressed air to process; one stream is taken into the instrument air dryers. They contain two cylinders filled with moisture removing 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 (4300-V02).

COOLING TOWER

Cooling tower is used to cool the process water. Cooling towers are designed on the basis of wet bulb temperature. The cooling tower cools the water by direct contact of water to the air so the water can not be cooled below the wet bulb temperature of the area.

The cooling towers are of three basic types

1. Natural Draft cooling Tower

2. Forced Draft cooling tower

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3. Induced Draft cooling tower

The induced draft cooling tower is the one in which the fan is placed on the top of the tower and air enters into the tower from side slits. So the induced draft cooling tower is more efficient.

In the IFL induced draft cooling tower is used.

The water from the process returns to the top of the tower where it is spread all over on the tower through the distribution nozzles onto the wood fills, where the air coming through the louvers cools the water due to heat transfer. Wood fills are used to increase the contact area of air and water. The cooled water is then passed through vertical mesh strainer to remove any external objects and comes to the pit. Then there is a suction strainer present before pump for further filtration. Corrosion inhibitors, such as sodium or zinc based are added in the water to reduce corrosion in the piping. The zinc reacts with access oxygen and a superficial layer of oxide is developed which prohibits rusting and corrosion. Scaling does not occur in this stream due to low temperature.

BOILERS

The boilers are used for the production of steam, which is then used on many types of equipments in the plant. The basic consumption of steam is in the fibre draw line and in the polymer section.

There are basically two types of boilers

1. Fire tube boilers

2. Water tube boiler

Fire tube boilers are used in the IFL.

The steam condensate returning from the plant comes to the feed water tank where a de-aerator is also attached to remove the air from the steam condensate. In this vessel four types of chemicals are added to condensate.

Hydrazine--------------------for removal of free oxygen

Caustic soda----------------for maintaining pH

Di-sodium phosphate---------it precipitates total dissolve solids (TDS)

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Ammonia gas-------------------also added for maintaining pH

After the feed water tank the condensate is pumped by two pairs of pumps (one pump of each pair is stand by) to the boiler.

The condensate enters the boiler on the shell side and converts to the vapors form by heat transfer from the fire entering from the tube side. The steam from the boiler then enters the super-heater at 25-bar pressure and the steam form the super-heater exits at about 245 oC.

The steam at 25 bar pressure is then divided in to 3 different pressures

25-bar

10-bar

6-bar

NITROGEN GENERATION

There are two units to produce nitrogen

Technical nitrogen

Pure nitrogen

TECHNICAL NITROGEN UNIT

It consists of plant a & b, the NT is produced in a pressure swing adsorption unit consisting of

Air compressor

Chilled water air cooler

PSA unit

A two stage air compressors giving compressed air at a pressure of about 8- bar prepare air required.

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Currently unit is operated is at external supply. Compressed air passes through pressure releaving valve where its pressure reduces from 9.5-bar to 8.3-bar. This air then passes through chilled water cooler. This water is supplied from 3851 it lowers the temperature from 30 oC to 12 oC, also moisture trapped is removed. This air is transferred to BUFFER VESSELS (b01, b02) each of 750 liter 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

(v09 , v10 ) of 3000 liters.

Down stream 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 produce from plant A and B is stored in 4400-v07. The NT produce must contain O2 <1%.

PURE NITROGEN UNIT

It also contain 2 units plant A &B. stream towards 4400-v07 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 in the presence of Palladium as a catalyst. The reactors maximum allowable pressure is 13 bar and maximum allowable temperature is 240 oC.

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. This NP then pass through dryers containing Ecosorb to remove any further moisture present in it. Capacity of this unit is 10 m3/ hr.

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CHECKED BY

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POLYMER SECTION

The product of IFL Polyester Plant is PET (Polyethylene Terephthalate) staple fibre or chips (textile grade). The capacity of IFL-1 is 200 T/day. Polymer section is automatically controlled by DCS (Distributive Control System).

RAW MATERIALS

Basic raw materials for the PET production are

PTA (Pure Terephthalic Acid)

MEG (Mono Ethylene Glycol)

PTA (PURE TEREPHTHALIC ACID)

Chemical Formula COOHC6H6COOH

Molecular Weight 166.14

Color White (Powder)

Particle Size 70-160 micron

Moisture Content <=0.2 wt%

Amount of PTA 860 kg/Ton of PET

Sources of PTA:

Siam Mitsui Thailand

PPTA (ICI) Pakistan

etc.

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PTA is in the form of

1000 Kg or 1 Ton Bags

22 Ton Containers

700 Containers can be kept in the container storage area.

From here PTA is discharged into Silos or vertical buffer vessels by Rotary feeders. All the conveying of PTA is done under pressure with the help of Nitrogen which is an inert conveying medium. Technical Nitrogen for this purpose is prepared in the utilities section. Pressure is almost 1.0~3.0 bar maintained. It must be noted that the amount of O2 must not exceed than 5% because it can form explosive medium and if conveying medium contains O2 more than 4% system trips itself. There are five screw type double stage compressors used in PTA section for compression of Nitrogen. Due to compression the temperature increases to 240 oC. It is reduced to 40 oC or less with the help of cooler. Water is used as a coolant before nitrogen is sent to compressors, bag filters are used in compressors inlet.

The capacity of the main silo is 500 m3. At the upper side of the silo there are two filters which allow N2 to pass through it. In this way N2 is recycled in compression section. From main silo PTA falls down into the rotary feeder. PTA is conveyed to day silo with conveying action of N2. If system pressure is down fresh N2 can be taken from “UTY” to maintain the system pressure. Day silo then supplies PTA to polymer section.

MEG (MONO ETHYLENE GLYCOL)

MEG is a refinery product which is in liquid form and its suppliers are

MOBIL Saudi Arabia

Equate Kuwait

etc.

Its properties are

Molecular Formula HO-CH2-CH2-OH

Molecular Weight 62.07

Colorless, Transparent Liquid

Boiling Point 197.6 oC

Flash Point 134 oC

Amount of MEG 337 Kg/ Ton of PET

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Tank yard

HTM SECTION

HTM stands for “Heat Transfer Media”. HTM is used as a source of heat for different units of plant. Sentotherm and Dowtherm are used as HTM. HTM is heated in the furnaces Natural Gas is being used as a fuel in the furnace. There is also supply of Bunker Crude Oil (occasional use) as well.

When HTM is introduced into the furnace its temperature is about 290-295 oC, it is heated upto 325-330 oC in the furnace. The heated HTM is again sent back to different section i.e.

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Esterification Unit, Poly condensation Unit and Spinning Unit. 1 furnace is in working and other is on standby. Flue gases from furnace are passed through the economizer for preheating of entering air and finally are exposed to atmosphere at a temperature of 200-250 oC. Air enters the furnace at the top and combustion occurs. As a result of which heat is produced. Here air-fuel ratio is 12:1 flue gases are passing in the tubes of economizer and outside the tubes air is supplied with Force Draft fans. The remaining flue gases are vented through chimney. If flue gas temperature leaving the system is 420 oC, then the system is tripped automatically. It means required temperature of HTM has not been attained and heat is going to be wasted.

EGR (ETHYLENE GLYCOL RECOVERY) SECTION

In the polymer section temperature becomes quite high as 250 to 260 oC after reaction with PTA. Remaining MEG evaporate along with water vapors as its boiling point is 196 oC. This EG is recovered as it is not in pure form. It is very economical to recover it rather than to drain it, so we use a recovery unit.

DEG from polymer section comes back to EGR section in the vessel. The level of the vessel is maintained at 40%. From vessel EG is pumped to an evaporator, where mixture is evaporated at 160 oC. Here vacuum is maintained to lower the boiling point of EG. The system is being heated with HTM, which circulates in a jacket. From the bottom of the evaporator sludge is drained as it has high boiling point and does not evaporate. Vapors of mixture enter in the distillation column which has horizontal plates inside it.

Temperature is kept below EG boiling point. So that water evaporates from top and EG settles down. Now water vapors enter reflux condenser, this reflux condenser has two paths of tubes. Here water vapors condense. Water now enters reflux condenser. In between reflux condenser and vessel, the system is provided with vacuum pump. From reflux vessel some water is re-entered in the distillation column and some fraction is discharged.

Now at the bottom of the distillation column EG is settled down with the help of centrifugal pumps. This EG has temperature almost 157 oC so it is cooled in the cooler to lower its temperature. From cooler EG is collected in a vessel from that vessel sample is tested. If EG meets our requirement it is taken to the storage tank with the help of a pump, if not than it is re-distilled. From storage tank EG is ready to supply to polymer section.

21

Ethylene glycol Recovery Unit

22

PASTE PREPARATION

Paste is prepared in a mixer. PTA and MEG come from respective storage vessels in the mixing tank 1413-V01 in a mole ratio of 1:1.2 respectively. Here mixing is done with the help of agitator and catalyst solution is also added. PTA powder is continuously used into paste preparation vessel via a dosing system. The composition of the paste is 70% PTA and 30% MEG. Now after the formation of paste, the paste with the help of screw pumps is transported to a reactor for the Esterification. Paste tank level is maintained at 92% and residence time is 182 minute.

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Paste tank

ESTERIFICATION

Esterification is a process in which acid reacts with alcohol to form ester. At IFL PTA (Pure Terephthalic acid) and MEG (Monoethylene Glycol) are mixed in the paste vessel. In vessel mixing

24

is facilitated with the help of agitator. In this vessel, fresh EG, recovered EG from EGR, EG from the distillation column and catalytic EG is mixed with PTA.

In this process Sb(CH3COO)3 is being used as catalyst. Its quantity is 165 ppm/ton of the product. This paste from paste vessel is transported to Esterification vessel ES-I by screw pumps. At a time both of the pumps are in operation. ES-I is jacketed vessel, in jackets HTM (Dowtherm vapor heating medium) circulates in the coils and heats the mixture. Here pressure is maintained at 0.39 bar. At this pressure and temperature MEG reacts with PTA to form monomers as follows

ACID + ALCOHOL →ESTER +WATER

2HO-CH2-CH2-OH +HOOC-C6H4-COOH HO-CH2-CH2-O-CO-C6H4-CO -O-CH2-CH2-OH+2H2O

As a result of Esterification H2O evaporates as boiling point of MEG and H2O are 197 oC and 100 oC respectively. This EGR and H2O mixture is taken to Process Column where EG is recovered.

Here level of vessel is kept almost 60%. Almost 97% reaction is completed here. NT is also injected to have level indication of reactor. Residence time is 233 min and reaction temperature is 258 oC.

From ES-I this mixture is taken to Esterification unit II (ES-II) by gravity. Here temperature is kept between 265-270 oC and at 0.17 bar. HTM is used for heating. Inlet temperature of HTM is 330 oC and outlet temperature of HTM is almost 315 oC. Fresh EG is also added. Residence time is 77 min. Here reaction is 99% completed. H2O and MEG evaporates at these conditions which are taken to distillation column, level is kept at 40%.

In the ES-II unit TDO is added to give color to paste which is formed after the reaction. The color of the paste after reaction is bright or semi dull. It can be given four different shades which are super bright, bright, semi dull and dull. Then this esterification product is taken to the Poly condensation section.

POLYCONDENSATION

This process completes in three different reactors which are PP-I, PP-II and DRR. In this process monomers are polymerised to form polymers. In Esterification unit some monomers are converted to polymer but most of the polymerization takes place in the Poly condensation section.

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POLYCONDENSATION

PP-I (PRE-POLYCONDENSATION-I)

26

In this reactor vessel material comes from Esterification unit by gravity which consists of mostly monomers. When under pressure material goes to vacuum agitation occurs itself. A vacuum of 120 mbar is maintained here. The vessel is jacketed, where heating coils heat the material to 262 oC. Here heating media is Sentotherm and dowtherm. Sentotherm is in the coils while dowtherm is outside the jacket. Residence time of the material is 55 minutes. Here a definite level is maintained in the vessel with the help of level controller.

Here reaction is as follows;

BHET (Bi Hydroxy Ethylene Terepathalate) Polymers + (n-1) EG

PP-II (PRE-POLYCONDENSATON-II)

The material from PP-I comes by gravity to PP-II that is in the form of paste. In PP-II spiral baffles are located. This vessel is also jacketed. Here heating medium is dowtherm. Agitation is done with the help of paddle type agitator. Agitation is at 50% of the speed of the motor. Here vacuum is maintained at 20 bar. Temperature for PP-II is 270 oC. Residence time is 60 minute in the vessel. From here material is taken to the DRR. But before DRR material is filtered by passing it through candle filter which is perceptible to polymers only. Filtration is necessary because during polymerization some olegomer or TDO concentrate may form. The size of pore in filter is 20µm.

DRR (DISC RING REACTOR)

Polymer from PP-II after filtration comes to DRR. In this reactor a series of set of disc is arranged. The first discs are larger in diameter and also greater in number than the later one. There are 44 discs in the vessel. Baffle plates are placed horizontally. These discs are arranged on a shaft, which is being moved by motor. Here vacuum is maintained at 0.5-1.5 bar. Temperature is maintained at 280-282 oC. Santotherm circulates in coils. Level is at 24% in coils. Level is 24% in the vessel chain length increases from 35-105.

In the initial stage when the material enters the vessel the diameter of discs occupied is 31% of vessel diameter and at the later stage it is 18%. Shaft is being rotated at 4.75 rpm, (75% of the speed of the motor). Residence time in disc vessel is 240 minutes.

From this material is passed through candle filter, which remove the contamination and unwanted product formed during the polymerization. Than gear pump moves this material to the spinning section.

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CHECKED BY

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SPINNING

DEFINITION:

It is a process in which the states are changed that becomes crystalline from amorphous state

INTRODUCTION:

There are two product lines at spinning plant as line no 71 & 73, each with design capacity of 100 ton/day. We are running the plant at 98t/d for the semi-dull product and 95 ton/day for the circular bright product and trilobel bright product. Normally we are producing semi-dull product on line 71 and circular bright and trilobel bright on line 73 spinning.

DESCRIPTION:

The polymer melt coming from the polymer plant through a jacketed pipe system, passes through a polymer heat exchanger 7199-EO1/EO3 enters to the spinning manifold 7137 & 7337.

The process line is heated with HTM liquid in order to maintain the product (PET) temperature constant through the manifold area as 289 oC for circular bright.

From the polymer melt exchanger, the polymer melt passes through a distribution pipe system, which guaranties the equal residence time of polymer melt to each spinning position.

There are five spinning manifolds on each line. Before entering to the spinning manifold, melt enters to the static mixer. After the polymer heat exchanger the temperature of product is kept uniform by static mixer and HTM vapor, heating system before distribution.

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The spinning manifold consists of three double cells, each double cell has two spinning positions, so total No of positions are 30.

Manifold is designed for the bottom heating of spin pack. Spin pumps are located on the top of the manifold. Each spinning position has its separate spin pump and spin pack.

The spin pump feeds measured quantity of polymer melts to the spin pack at a uniform flow rate. Before each spin pack pump, a freezing valve fitted applied with the process air, so that each spinning position can shut down individually.

The polymer melt is converted in to filaments extrusion by spin pumps. The extrude filaments passed through a quenching duct in which these filaments are cooled and solidified by uniform flow of quenching air.

Each spinning position has a separate vertical quenching tube supplied by quench air at temperature of 19 oC and relative humidity of 83%.

After solidification, the filaments pass through the ring oiler device.

Ring oiler device applies S.F Oil to the filaments in order to remove the static charge and aging required moisture to the filaments.

Ring oiler pumps are inverter driven pumps through DCS and one RO pump applies S.F oil for the two spinning positions.

In the lower part of the quench air duct, there is a quench air exhaust duct. The vapor containing and monomer component with the hot air, tend to escape through the exhaust duct and exhausted to the atmosphere by monomer scrubber unit showered with soft water, which dissolves the monomer contents and make the air pollution free and hazard free.

Then the filaments reach the spinning wall where the final amount of S.F oil is applied to the filaments for the required moisture content, as 30% moisture with the help of thread oil devices.

All thread oiler devices are coated with ceramic coating. Thread oiler pumps are also inverter driven and one pump applies S.F oil to for positions.

Before thread oiler devices, there is ceramic coated rod called slub coater, which holds the filaments bundle for each position. Each position s 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 bar.

The filaments then passed through drip detector. Whenever drip or plastic comes with filaments, it operated 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 undriven 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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QUALITY CONTROL:

In spinning section we are achieving following properties of the filament.

1. Tensile property

2. Position denier

3. Mono filaments denier

4. Moisture contents

5. Elongation

SPINNING CYCLE

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SPIN PACK REGENERATION

Spin pack is most important unit in the spinning section. The spin pack is charged after 48 days for semidull product and after 38 days for circular bright. After this we regenerate the spin pack in auxiliary workshop.

So in the first step, spin pack is removed out from specified spinning position with the help of pack manipulator. Then it is brought to the auxiliary workshop by a trolley and placed on dis-assembling device. Here hydraulic machine operated at 500 bar hydraulic pressure , disassemblies spin pack.

After disassembling sand, gaskets, all fibres , Sleeve, joint ring are wasted. While the following pack parts are charged in vaccum pyrolysis unit for cleaning these parts.

1. Perforated plates

2. Distribution plates

3. Sports rings

4. Ring distribution plates

The polymer melt stick on these parts is removed out by heating at 350/450 oC. After this these parts are washed with DMW zip cleaner.

Five packs are cleaned in one batch, as spinneret is the most important perforated plate, which has five fine holes.

TEG SECTION

The spinnerets are cleaned in TEG bath. I n TED bath, Tri-Ethylene Glycol is charged in TEG bath. A batch of five spinnerets is charged in TEG bath.

The cleaning process continues for 480 min at temperature of 270 oC.

After cleaning the spinnerets batch is removed out from the TEG bath and charged in 5% NAOH bath. Here cleaning is carried out for 60 min at temperature 70 oC. Then it is charged to DMN washing bath for 60 min at oC. after 5 no of batches used TEG is drained and fresh TEG is charged in TEG bath. 5 spinnerets can be charged in one batch of TEG bath.

ULTRASONIC BATH

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A 5% solution of deconex with DMW is filled into ultrasonic bath.

The solution is heated up to 75 oC. spinnerets after TEG cleaning is charged into ultrasonic bath for 30 min.

Also we clean the distributed plates and S-fold filters for 15 min each. All these parts are charged individually.

AIR DRYING DEVICE

The spinnerets and other parts of the ultrasonic cleaning are dried in this device with the application of the process air.

Then cover the dry spinnerets in polythene sheet and placed in store for inspection while 5-fold filter and ring distribution plate are placed in assembling room.

SPINNING AUXILIARY:

The dry spinneret is brought into spinneret inspection room.

For inspection we have following programs

1. For 3750 holes spinneret for IFL-1

2. For TL spinneret for IFL-II

3. For 5250 holes spinneret for IFL-II

4. Hollow fibre spinneret for IFL-II of 1320 hole is done.

The holes are magnified inspected of individual hole is done.

If any hole is choked, then the spinneret is recharged in TEG bath or in ultrasonic bath.

Or dust is removed out from choked hole by compressed air or needle.

The pack body or pack lousing, bolts & filling rings are cleaned with brass brush.

PACK ASSEMBLING

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Pack parts for pack assembling are

Pack housing

Fitting ring

Cover

Perforated plate

Fold filter 1, 4 & 5

Silica sand

Distribution plate

Joint ring

Small gasket and large gasket

Spinneret

2.6 kg of sieved silica sand is filled as a filter media, also packed with other packing of line filters.

The foreign particles from polymer melt are filtered in this filter media and the melt is extruded through spinneret holes in form of filaments.

The assembled spin packs are placed in pre-heating ovens at 310 oC.

After 24hrs charged in oven the spin pack is ready for install at spin position. 18 spin packs can be charged in one spin pack pre-heating oven.

FIBRE DRAW LINE

CREEL AREA

In this area the can are placed and the sub tow is used to form a larger tow. In this area 72 cans can be placed, 18 cans on either side can be on stand by and 36 cans in the middle area are placed, from where required no of canes are used.

The no of canes operating at a time are dependent on the no of positions operating in the spinning area.

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The same force pulls off each sub tow but the speed is adjusted by provided more hindrance to close cans.

Y02 TOW FORMATION UNIT:

Here the sub tows coming from the cans are arranged in three bands.

Y03 TOW GUIDING FRAME:

This unit consists of 7 rollers rotating at a speed of 61.2 m/min.

Y04 DIPPING BATH:

Here we have a bath of spin finish oil at a temperature of 20-22 oC to Pre-lubricate the tow and maintain the temperature of all the tows coming to a constant level.

DRAW FRAME 1:

The draw frame is used for the drawing of the polymer along its length.

It has 7 rollers, 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.

DRAW BATH:

This is a closed tank where the spin finish oil at 80 oC is showered on the tow. The steam in the plate type heat exchanger heats the spin finish oil.

DRAW FRAME II:

This is the second draw frame present in the fiber line. It has 7 rollers having a rotational speed of 198.5 m/min. The rollers of this draw frame are provided with steam to heat them.

THERMOSETTING UNIT:

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 chamber is supplied with 250 bar steam supply that is used as a 15.5 bar steam supply.

TOW COOLER:

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The tow from the thermosetting unit is passed through the cooler where spin finish oil is sprinkled by 12 nozzles arranged at a 30 angle having 6 nozzles on both sides.

The tow is cooled to 90-100 oC.

DRAW FRAME IV:

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.

OVER LAPPER & THREE ROLLER FRAME:

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.

TENSION ROLLER:

The unit maintains the tension of the roller & again sent to the steam unit to gain the cotton like property.

CRIMPER UNIT:

Now tow is crossed through the crimper unit.

This unit induces crimps on the fiber at a rate of 13 crimps per inch.

The crimps are made for necessary fiber flexibility & cohesion.

TRAVERSING UNIT:

The tow leaves via traversing unit where 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.

TOW DRIER:

In this section the tow is dried & cooled.

This section consists of four zones, one of which is cooling zone while other is heating zone.

10-bar steam is supplied for the heating zone.

After being dried the tow is transported to the cutter vertically to free roller.

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BAILING & CUTTING

CUTTING OPERATION:

The tow is directed through deflector rollers & breaker rollers. Then the tow reaches to cutter after passing from the V-guide.

The cutter consists of a circular plate and circular blade. The tow is wrapped around the cutter plate and when circular plate touches the cutter then the fiber in specific length is cut down.

BAILER:

The fiber after cutting comes to the prebin chamber attached to a weigher bin. When the weight of the fiber reached to 50 kg a pusher comes and pushes it to the pressure area where the fiber is pressed with a hydraulic system.

When the weight of the fiber becomes 300 kg the fiber is rotated to the main press where hydraulic system is used to press it and form a bail.

SPIN FINISH OIL PREPARATION:

In the preparation of the spin finish the oils used are HC19 and TD8. The purity of the HC19 is 40% and is aqueous compound of potassium alkyl phosphate .The density is 1.157 and pH is 10-10.5. The color is white, the spillage, the liquid binding material such as sand dolomite, acid binders and sawdust.

The purity of the TD18 is 98-100%. It is a compound of non-ionic emulsifiers. The dangerous compound is alkyl phenol, poly-glycol ether 45.55% and ethoxylated fatty amine 20-30%. The pH is 10-11, the color is bright, concentration is 0.7. The spillage is same as HC19.

These two oils are used in the spin finish area.

The mixing ratio of the components is as follows,

HC19 = 70%

TD18 = 30%

CHECKED BY

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