POLYESTER FILAMENT YARN

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PROCESS DESCRIPTION

1.0 Continuous P.T.A. - Esterification :
Esterification occurs continuously in two series connected esterification reactors (C-050, C-052).
The PTA/EG-Paste is fed continuously into the first reactor C-050 by means of a level control. The reaction water occurring during esterification is separated from the ethylene glycol in a fractionation column K-050 above the reactor. The esterification is completed in reactor II (C-052). Both reactors are located on the same level. The reaction water is condensed in the condenser (W-053) and the divided in a reflux separator into 2 streams. One stream is reflux to the column while the other is routed to waste water.
The stabilizer at dulling agent is dissolved in preparation vessels and charged from a surge drum into the esterification reactor II C-052 respectively before filter F-054 by means of a metering pump.

Throughput variations due to downstreams polycondensation are handled by level control in the reactors and compensated by varying the relative proportions of the feed steams.

From reactor II C-052 the esterification product is conveyed by means of a pump P-054 through a precondensate filter F-054 to first polycondensation autoclave C-100 of the polycondensation step. The filter F-054 is heated with Dowtherm vapour from Dowtherm evaporator W-056.

2.0 Continuous DMT-Transesterification :
The liquid DMT is constantly transferred from the daily work tank B-46 by a pump P-049 to the transesterification reactor I C-050. A flow controller is provided for accurate proportioning.

Ethylene glycol is supplied from elevated tank B-052 through a preheater to the mixing chamber of transesterification reactor C-050.
Catalyst for accelerating the transesterification reaction is fed to the same chamber of the reactor. The methanol vapour occurring during reaction is separated from the glycol in a column K-050 above the reactor. In reactor C-051 and C-052 the transesterification product is heated and reaction occurs until approximately 99 % of the product is reacted into prepolymer.

The catalyst and stabilizer required for polycondensation are dissolved in a preparation vessel and charged from a surge drum to esterification reactor C-052 by means of a metering pump. Operation of the plant is fully automated. DMT glycol and transesterification catalyst solution are charged continuously to transesterification reactor C-050 and polycondensation catalyst and stabilizer to reactor C-052 at predetermined relative proportions. Throughput variations in polycondensation are handled by level control in the reactors and compensated by varying the relative proportions of the feed streams.

From reactor C-052 the esterification product is conveyed by means of a pump through a precondensate filter to the first polycondensation autoclave of the polycondensation step. The filter is heated with Dowtherm vapour from a Dowtherm evaporizer.

3.0 Continuously Polycondensation :
Polycondensation of the precondensate from the esterification section occurs continuously in 3 series-connected autoclaves. The product from the precondensate filter F-054 is fed into polycondensation autoclave I C-100. This autoclave is heated by means of an incorporated Dowtherm evaporator.

Reaction in the autoclave takes place under a vacuum of approx. 70 mbar. This vacuum is generated by a glycol jet V-100. The glycol set free during reaction is condensed in the spray condenser W-100 of the glycol jet and fed into the recovery via a glycol receiver B-100. The glycol used for the spray condenser W-100 is removed from the glycol receiver B-100 by means of a pump P-103, cooled down by a cooler W-104, fed into the spray condenser and flows then back to the glycol receiver together with the condensed reaction glycol. The product leaving autoclave I C-100 has a degree of polymerisation of Pn = 12 - 15.

In the autoclave II C-101 the reaction takes place under a vacuum of approx. 7 mbar generated by glycol jet V-101. The autoclave is heated by means of a Dowtherm evaporator W-107. The autoclave is equipped with an agitator R-101. The glycol set free during reaction is condensed in a spray condenser W-101. The product leaving autoclave II C-101 has an average degree of polycondensation of Pn = 40.
The final viscosity of the product is reached in the finisher (autoclave C-102) which is designed as a disc cage type reactor. The autoclave C-102 is equipped with driven disc cage. The product passes consecutively through all rotating discs, which guarantees a defined product residence time. Polycondensation in the finisher occurs under a high vacuum. The vacuum is generated by means of steam jets V-102 - V-105. Condensation of reaction glycol occurs in two inline arranged spray condensers W-109, W-110. The finisher is heated by means of Dowtherm vapour W-108.

When the polymer has reached its final viscosity in the finisher it is continuously discharged by means of a special gear pump P-102. The melt is fed to the chips production unit and is also connected directly to the spinning section through melt pipes. The throughput of the polycondensation has to be kept as constant as possible in order to prevent product variations. To meet this requirement, the feeding is controlled backwards from the end of polycondensation.

4.0 Chip Production and Storage :
For chips production, the polymer produced in the finisher is converted into chips in an underwater granulator. Continuous discharging of the polyester out of the vacuum of the finisher and feed to the extrusion head X-150 is achieved by means of a special discharge pump P-102. The extrusion head and the melt outlet valve are heated with Dowtherm, which is evaporated in a Dowtherm evaporator W-108.
The strands of molten polyester emerging from the nozzles of the extrusion head X-150 are gravity fed to a guide plate with longitudinal slots, which is supplied with overflow water from a weir. The still molten strands are transported - surrounded by water - by gravity to the feed rolls of a chip cutter A-150. On their way down cooling and solidification occurs, starting from the surface.

The feed rolls of the cutter A-150 catch the strands and guide them to the cutting tools. Cutting occurs between a fixed terminal strip and a revolving rotor. After the cut the chips are floated out of the machine with water and thereby furthermore cooled down. The demineralized water necessary is supplied by pump P-150. During chipping, the demineralized water temperature is kept constant by cooling and chilled water through demineralized water cooler W-150, W-151. The chips are floated to a water separator where the main part of the water is removed in the dryer T-150 the water content is reduced to approx. 0.5 wt %. Before the chip drop into the analysing silo B-151 A/B the chips will be removed from fines in a sieving machine S-150. From the analysing silos the chip will be transported by a pulsation-conveying device X-152 into a chip storage and blending silo B-158.

5.0 High Speed Spinning of Polyester Melt into Pre-Oriented Filament ` (POY) :
From the final autoclave the melt is supplied through distribution pipes via one common non-stop filter to the spinning boxes with two spinning positions each. Each spinning position is associated with 2 four-fold spinning pumps and 8 spinnerets. Each four-fold spinning pump meters the melt to 4 spinnerets.

Downstream of the spinning pumps the melt is filtered and is then pressed through the boreholes of the spinneret plates in the form of filaments. The route of the melt from the final autoclave to the spinnerets is short which ensures uniform properties of all filaments.
The spinning boxes are heated with Dowtherm vapour which is generated in a vaporizer. The temperature is maintained at a constant level. The filament bundles leaving the spinnerets are cooled in blow ducts by a horizontal current of air Dowtherm of the blow ducts the filaments are guided through spinning tubes to the winders of the take-up machine. The spun filament is provided with finish oil by means of precision metering pumps, which are located below the quench duct.

The finish oil gives the filament the necessary antistatic properties, good sliding properties, proper adhesion of the individual filaments and adequate moisture and facilitates the subsequent further processing. Static inverters with high precision frequency adjustment feed the drive rolls of the winding heads. The grooved rolls and the traverse motion devices are also fed by static inverters with frequency adjustment and sweep generators for varying the speed periodically. The filament (POY) produced on this type of machine is pre-oriented, which means that it can be stored and transported without the need of special climatic conditions. It can further be processed on such texturing machine which allow to draw the yarn in the first heater simultaneously with a ratio of upto 1 : 2. Four spinning lines each with 12 spinning positions are provided.

6.0 AUXILIARY UNITS :
6.1 PTA Storage, Conveying and Pasting :
The basis is that the PTA is supplied in 1 t bags, which are unloaded into a funnel B-001. From the funnel, the PTA is fed with a screw convey H-001 into a hopper B-002 from where it is supplied by a pneumatic conveying system to the PTA-storage silo B-050. The PTA and the EG are well mixed in the paste mixer B-051 by an agitator of special design. The paste produced is discharged by means of a paste pump P-052 feeding into the esterification reactor I C-050. For homogenization, part of the paste is recycled. The catalyst required for the polycondensation is also charged into the paste mixer B-051 by means of a metering pump.

6.2 Glycol Storage System :
Two storage tanks B-020 1/2 are provided for the storage of ethylene glycol. The ethylene glycol is supplied from the storage tanks by a centrifugal pump P-020 into the daily work tank B-021 and from there with pump P-022 via filter F-020 to the glycol elevated tank B-052.

6.3 DMT Melting, Storage and Conveying System :
The basis is that the DMT is supplied in bags of 25 or 50 kg, which are unloaded manually. In the melter B-045 the solid DMT is molten. The heating of the melter is done by steam, N2 blanketing is foreseen for protection of discoloring of the liquid DMT. With a circulation pump P-048 a certain quantity of molten DMT is pumped into the DMT daily work tank B-046, while the other amount is recirculated back into the melter. On this route the molten DMT is passing a heat exchanger W-049. The daily work tank has N2 blanketing, for same reasons as provided for the melter. From the daily work tank, the molten DMT is transferred through a candle type filter F-049 to the transesterification reactor-C-050.

6.4 Central Dowtherm heating System :
A central heating system supplies the heat requirements for the overall plant. The heat is generated in a Dowtherm heater which is equipped with oil-fired burner and then carried to the various consumers by circulation of the heat transfer fluid.

Primary Dowtherm System

The primary Dowtherm system is forced circulation system.
The heat transfer medium is circulated by the primary Dowtherm pump P-700 and heated in the tubular heater D-700. It transfers its heat, as required, to the various consumers in the transesterification, polycondensation and spinning section. To ensure adequate flow and temperature in the heater during commissioning or in the event of low heat requirements, a direct connection with control valves is provided between supply and return line parallel to the consumers.

The entire system is pressurized with nitrogen to prevent vaporization of Dowtherm in the primary system ( hazard of cavitations in circulation pumps). The nitrogen connection is provided at the Dowtherm expansion vessel B-701 which is connected to the Dowtherm system at the suction side of primary Dowtherm pumps.

A Dowtherm storage tank B-700 and a Dowtherm slop tank B-702 are provided for partial or complete draining of the Dowtherm system. All Dowtherm heat exchangers can be isolated and drained or filled separately. The drain line is also used for filling. Filling is accomplished by a Dowtherm reloading pump P-702 from the slop tank.

The Dowtherm storage tank B-700 is connected directly to the atmosphere via a Dowtherm condenser W-700, Hot ascending Dowtherm vapours are condensed in this condenser. Dowtherm losses and air pollution are so avoided. The tubular heater D-700 is a vertical cylindrical unit with refractory lining and is fired with fuel oil. The Dowtherm flows through coils and the heater walls of the combustion chamber and is heated by convection and radiation. Combustion air is taken in from the atmosphere by a fan V-700 and passes to the combustion chamber.

The tubular heater is equipped with a flow-controlled by-pass to assure that the same flow rate passes through the tubular heater
independent of the heat. The primary consumers are supplied with hot Dowtherm from the heater supply line and return it at lower temperature to the heater return line.

Secondary Dowtherm System

The secondary system is connected directly to the primary system by a supply and return line. The supply line, in which a control valve is installed, connects the primary discharge side with the secondary suction side. The return line connects the primary suction side with the secondary discharge side.

The temperature of the secondary system is controlled by mixing the hotter heat transfer medium from the primary system with that from the colder secondary system. The heat transfer medium is circulated by pump P-704.

6.5 Glycol/Methanol Recovery :
The by-products from the (trans)-esterification and polycondensation stage are accumulated in a receiver B-240 from where they are charged to a discontinuous recovery unit for distillate treatment. Glycol is recovered from the multicomponent mixture of such high purity that it can be reused as feedstock for (trans)-esterification. Also methanol of technical grade can be recovered. The other components are waste products.

From the receiver the feedstock is pumped to the still B-242 of the sieve tray column K-240. The batch is heated whereby methanol is removed. Distillation occurs under vacuum in order to ensure gentle separation of glycol (at high temperatures it decomposes into di- and tri-glycol). When glycol and methanol (methanol is only gained if DMT is used as raw material) are removed, the other components are discharged as residue via pump P-242 into a residue tank B-241. From there it can be transferred to the Dowtherm heater for burning with the help of the special residue burner.

6.6 Cleaning Unit for Filter (F-054) and Non-stop Melt filter :
The contaminated precondensate filters and non-stop melt filter are boiled out in TEG and then rinsed with water in a separate tank.
The filters are finally subjected to ultrasonic cleaning.

6.7 Cleaning Unit for Spinnerets, Spinning Pumps, Filters and Spinneret Testing Device :
A burnout furnace serves for the cleaning of spinnerets, spinneret packs and spinning pumps. A glycol-cleaning unit serves for the cleaning of filters and spinnerets. An ultrasonic set is used for final cleaning of the spinnerets. The spinnerret testing unit serves for testing the cleaned spinnerets with special projector. This eliminates the use of insufficiently cleaned spinnerets and cuts down the amount of waste.

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POLYMER SECTION WAS COMMISSIONED IN 1994-95.
YARN PLANT WAS COMMISSIONED IN 1991-92 ON EXTRUDERS.
DMS (DIRECT MELT SPINNING) WAS COMMISSIONED IN 1996-97.

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SPANDEX YARN PLANT

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6. MATERIAL BALANCE :
The complete material balance showing the inputs and outputs is shown at Table 1.1. The storage conditions of various raw and auxiliary materials is provided at Table 1.2

7. BLOCK DIAGRAM :
The basic block diagram indicating process flow is given below :
 

MATERIAL BALANCE OF SPANDEX PLANT
MDI 196 Kg		Product{(975+25 Oil)+30 Oil} Kg
PTG 764 Kg		Waste Yarn (82+20 Oil) Kg
CEA 29 Kg		Waste Oil 15 Kg
ADD.A 77 Kg		Waste Dope } Solid 8 Kg                     } DMF 11 Kg

SPANDEX PLANT
                    

ADD.B 15 Kg		Exhaust DMF 26 Kg Drainage DMF 26 Kg
ADD.C 20 Kg		Distillation Residue (DMF 114 Kg+ADD A,B & C 35 Kg)} Polymers (1 Kg)
DMF X+200 Kg		Others DMF 23 Kg Recolleted DMF X Kg

Table 1.2

8.

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NYLON PLANT

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CENTRALISED UTILITIES

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UTILITIES :

(CENTRALISED & SPECIFIC UTILITIES)
Petrofils Co-Operative Ltd., Naldhari Complex comprises of 3 grass root plants viz.
1. Nylon-6 and Draw Twisting Yarn Plant
2. DMT/PTA-Polyester Filament Yarn Plant
3. Spandex Yarn Plant

Centralised Utilities have been provided to cater to the demand of individual plants. In addition; certain specific utilities have been housed within the boundries of individual plants on the consideration of economy.
The other relevant details about the utilities are described as under.
CENTRALISED UTILITIES

1.01 ELECTRICAL POWER
Electrical Power for the entire complex has been brought through two independent 132 KV conductsors from GEB grid Achhalia situated around 28 Kms from Valia. From Valia two independent lines feed the power to Petrofils Switch Yard and is step down to 6.6 KV through two independent 10 MVA Transformers. This step down power is fed to PCCs and MCCs to either High Tension (6.6 KV) consumers OR LT consumers by further steping down the voltage to 440 volts.
The major electrical installations are by M/s. EEC, M/s. NGEF and M/s. L&T etc.

1.02 EMERGENCY POWER
To cater to the critical need of process lighting etc. in case of power failure two DG sets of 1278 KVA each have been provided. The distribution of power for the critical equipments has been provided as shown in the SLD.

1.03 WATER REQUIREMENT
The water requirement of the complex is met from the GIDC water which is pumped by GIDC Authorities from Jolly Reservoir through pipe line situated at a distance of 8 Kms. To store Raw Water two concrete sumps of 1500 M3 each capacity have been constructed. Thus at any time 3000 M3 water is available for use.

1.04 WATER TREATMENT PLANT
Separate facilities have been provided to treat the Raw Water according to the quality including clorination treatment etc.

1.05 COOLING WATER
Requirement of Cooling Water for heat exchangers etc. is met through 4 cooling water concrete cells having a total circulation capacity 4000 M3/hr constructed by M/s. Simplex.

1.06 STEAM
The requirement of steam is met from three installed Boilers of 10 MT/hr capacity each having pressure rating of 16-17 kg/cm2.
Two Boilers have been supplied by M/s. Nestler and one by M/s. Thermax..

1.07 NITROGEN
Nitrogen requirement is met by Plant supplied by M/s. BHPV which operates on liquification of Air having capacity of 125 NM3/hr in terms of gas production.

1.08 COMPRESSED AIR
There are batteries of compressors generating compressed air at 8 kg/cm2 pressure. The total generation capacity 18,100 NM3/hr, moisture free air. The compressors are supplied by M/s.

1.09 EFFLUENT TREATMENT PLANT
The Effluent from all the three plants is collected and treated in a centralised treatment plant which is having treatment capacity of 850 M3/day. The trreated effluent conforming to GPCB norms is utilised in-house for gardening and irrigation of green belt planted inside the campus. The plant is supplied by M/s. Paramount.

1.10 DM WATER & BOILER FEED WATER
Requirement is met from a 30 M3/hr DMW plant supplied by M/s. ION Exchange. The same plant supplies BFW-Boiler Feed Water to Boiler as well.
1.11 FIRE FIGHTING/HYDRANT SYSTEM
All the three Plants, Stores, Ware Houses are covered through a network of Fire Water Pipings, Water Hydrants, Water Hosereels & Fixed Monitors etc duly designed by EIL and approved by BRC. The water lines are laid above ground and remains always energised through jockey pumps at the pressure of 8.0 kg/cm2. There is a separate DG Set operated pump which energies the entire system in absence of GEB power.

1.12 SMOKE DETECTORS
For early detection of fire the smoke detectors have been installed in the entire building and plants of PFY and NFY which generate alarm in case of any fire.

2 SPECIFIC UTILITIES-PLANT WISE

2.01 CHILLED WATER - NYLON PLANT
To cater to the need of Air Conditioning and Process, 60C Chilled Water is produced. There are 3 centrifugal machines of 600 TR each operating on 6.6. KV supplied by M/s. VOLTAS and are situated in the premises of Nylon plant.

2.02 CHILLED WATER - PFY & SPANDEX
Requirement of Chilled Water for Air Conditioning and Process for PFY and Spandex plant is met through 3 centrifugal chiller of 400 TR capacity each, supplied by M/s. BLUE STAR. Three machines operate on 6.6 KV electrical power and are housed in the premises of PFY Plant.

2.03 -130*C CHILLED WATER - SPANDEX PLANT
The process requirement of spandex plant is met through a 100 TR screw compressor refrigeration machine supplied by M/s. Kirlosakar. The Chiller operates on 440 V and is housed in the spandex building.

2.04 -50*C MDI & SAS COLD STORAGE ROOM
This facility is specifically provided for storage of MDI & SAS and is supplied by M/s. Blue Star by providing two 5 TR refrigerating machine.

2.05 DIPHYL HEATING
Requirement of Diphyl heating for Polymer and Spinning units except Nylon spinning where extruders are installed, is met through
(i) Two independent HTM units of 2.65 Mkcal/hr each in Polyester Plant.
(ii) Two units of 0.75 Mkcal/hr each for Nylon plant.
All the four units supplied by M/s. BHPV and
(iii) One unit of 0.3 Mkcal/hr supplied by M/s. ISOTAX for Spandex Plant.
The requirement of Spandex Plant can also be met from the heating unit of Polyester Filament Yarn plant for which supply and return lines of hot fluid has been laid.

3.0 CENTRALISED WORKSHOP FACILITIES
To carry out minor repairs the following facilities have been provided to cater to the need of Plants.