process description(final)[1]

7/16/2019 Process Description(Final)[1]

http://slidepdf.com/reader/full/process-descriptionfinal1 1/27

中中中中中中中中中CHINA TEXTILE INDUSTRIAL

ENGINEERING INSTITUTE

中中中中PROJECT

NOVATEX LTD. BOTTLE GRADE AMORPHOUS POLYESTER PLANT

中中UNIT

PET MAIN PLANT

中中DISCIP.

中中PHASE

中中DATE

PROCESS DESCRIPTION 中中DWG.NO.

803-01-1903

中 1 中中 23 中SHEET 1 OF 23PROCESS BASIC DESI. 2005.09

1 Process principle

1.1 Chemical reactions

Esterification is the reaction between terminal hydroxyl and terminal carboxyl. In esterification

process the dominant side reaction is the reaction among the free terminal hydroxyls and DEG. is the

product of the reaction. Acetaldehyde is also the by-product from the reactions.

Poly-condensation is the reaction among terminal hydroxyls of molecular chains polymer. In

poly-condensation process the thermal degradation reaction takes place. When temperature exceeds

285 , degradation is accelerated obviously. Acetaldehyde is the by-product from degradation.℃

1.2 Esterification process

Esterification reaction takes place between the terminal hydroxyl and the terminal carboxyl and

the poly-condensation reaction starts to take place in the meantime.

The esterification reaction is a reversible balance reaction. Under a definite temperature,

pressure and molar ratio between EG and PTA/IPA the maximum esterification degree which the

reaction can reach is called balancing esterification degree. Pressure in the system has strongest effect

on the balancing esterification degree. When pressure is decreased, the balancing esterfication degreeis increased. The esterification takes place in two stages. The high esterification degree can be reached

while pressure in the second stage is decreased near to atmosphere. Under low pressure the quantity of

evaporated EG is increased so that the load for separating EG is increased and the energy consumption

is increased in the meantime.

Temperature in the system has little effect on the balancing esterificaion degree but has strong

effect on the reaction rate constant. When temperature is increased the esterification reaction is

accelerated but in the meantime the side reaction in which DEG is generated is also accelerated.

When the ratio between EG and PTA/IPA is increased the balancing esterification degree is

increased and the reaction is accelerated. But higher is the ratio between EG and PTA, higher is the

load for separating EG.

In esterifation it is required to reach about 97% esterification degree.

中中中CTIEI中中, 中中中中

Copyright Reserved by



CTIEIA1

中中DESCRIPTION 中中DESIGN 中中CHKD. 中中APPR. 定审 F.APPR. 中中REV.

中中中中中中中中中CHINA TEXTILE INDUSTRIAL ENGINEERING INSTITUTE

中中中中PROJECT


中中UNIT

PET MAIN PLANT

中中DISCIP.

中中PHASE

中中DATE


803-01-1903


1.3 Poly-condensation process

In poly-condensation process the reaction among the terminal hydroxyls takes place and the

esterification reaction continues to take place in the meantime.

The poly-condensation reaction is also reversible balance reaction. The reaction can continue to

take place only when the product with low molecular weigh is taken out of the reaction materials. The

poly-condensation process consists of two steps including the reaction and the devolatilazation of the

product with low molecular weigh and the process rate depends on the step with lower speed. Poly-

condensation takes place under vacuum so that the resistance for the product with low molecular

weigh to be taken out is decreased. While the reaction continues the viscosity of the polymer is

increased gradually and it increases the resistance for the product with low molecular weigh to be

taken out. In a final polycondensation reactor with disc rings the rate of devolitilaztion is ten times

faster than the reaction rate when the intrinsic viscosity of polymer is lower than 0.62 and the process

rate is determined by the reaction rate. When the intrinsic viscosity of polymer is higher than 0.62 the

rates of the devolitilazation and the reaction are in the same quantity order level but the

devolitilazation rate is still faster than the reaction rate so that reaction rate has stronger effect on the process rate than devolitilazation rate.

Temperature has strong effect on both reaction rate and devolitilazation rate. It is the most

effective measurement for accelerating the poly-condensation process to increase the temperature.

Pressure has strong effect on the balancing condition in the reaction. When pressure in the system is

decreased the intrinsic viscosity of the polymer in the balancing condition is increased so that the

motive force of the reaction is increased. In the other hand it should be noticed that the speed in which

the product with low molecular weigh is taken out of the reaction materials is inverse proportion to

pressure in the system. While pressure in the system is decreased quantity of material taken out of the

reactor by the product with low molecular weigh is increased.

The specific surface of polymer melt in a reactor which corresponds with melt surface created of

the definite gravity of polymer has effect on the devolitilazation rate. The specific surface has no effect

on the reaction rate. When revolution of the disc ring in a final reactor is increased the specific





CTIEIA1



中中中中PROJECT


中中UNIT

PET MAIN PLANT

中中DISCIP.

中中PHASE

中中DATE


803-01-1903




opened and mixed vapor of water and EG is drained to 13-T03. Nitrogen pipe is connected to gases

pipe of the reactor. In emergency case nitrogen is fed to the reactor. PAH-12023 of 12-V01 is used to

send a signal to interlock to close the valve on primary HTM pipe to stop heat supply. If pressure goes

up continuously relieve valve PSV-12024 is opened and vapor is drained to 23-T03.

3.3 Second stage of esterification

See drawing 803-01-1203

13-R01 is a reactor with inner and outer chambers. Under pressure difference between 12-R01

and 13-R01 material flows to the outer chamber and then enters to the inner chamber through slim gap

on wall of the inner chamber. Material flows out of the reactor from the inner chamber. Pressure is

decreased in 13-R01 so that balancing esterification degree is increased and motive force of the

reaction is increased. Material is heated by coil installed in the inner chamber and temperature is

increased. Reflux EG and heat stabilizer are added to the inner chamber so that molar ratio is increased

there. A sampling valve is installed on discharge pipe. HTM circulation pumps 13-P01A/B are used to

supply HTM to coil of 13-R01 and jacket pipe between 12-R01and 13-R01. HTM evaporator 14-V01

is used to generate vapor to heat body jackets of 13-R01and 14-R01 and jacket pipe of gases attached

to the two reactors.

Esterification degree in 13-R01 reaches 96.5% ~ 97.0%.

3.4 Separation of EG and water

See drawings 803-01-1204/1205

Column 13-C01 is used to separate mixed vapor of water and EG coming from the two

esterification reactors and condensate coming from the two scraper of the two poly-condensation

reactors. Separated light part in the column is condensed in the top condenser 13-E01 and collected in

13-T01. A part of condensate is fed back to the column as reflux and other part flows by gravity to

vessel 47-T01 and is treated by stripping. Separated heavy part in the column is conveyed by the pump

13-P02A/B. Part of them is sent back to the two reactors and other part is sent to the spent EG

collection tank 17-T03. Sampling valves are installed on discharge pipe of 13-P03 and reflux pipe to

13-C01 respectively. Coil in the bottom of the column is heated by HTM liquid. The HTM



CTIEIA1



中中中中PROJECT


中中UNIT

PET MAIN PLANT

中中DISCIP.

中中PHASE

中中DATE


803-01-1903

中 8 中中 23 中



SHEET 8 OF 23PROCESS BASIC DESI. 2005.09

circulation pump 17-P05A/B is used to supply HTM to the column and the EG evaporator 17-V03.

Temperature in the bottom of the column is controlled by regulating amount of HTM fed to coil.

Temperature of vapor in the top of the column TR-13051 and pressure difference in the column PDR-

13062 are shown on screen in the central control room. TRC-13060 is used to regulate amount of

reflux to control the result of separation. Material level in the bottom of the column LRC-13065 is

used to regulate amount of EG conveyed to 17-T03.

EG content in the condensate on top of the column is controlled below 0.5%wt and water

content of EG in the bottom of the column is controlled below 1.5%wt.

Pressure alarm PAHH-13063 is used to send a signal to interlock to shut down the motors of the

pumps 12-P01A/B/C and 13-P01A/B and close the valve on HTM pipe in order to stop heat supply

and at the same time close the valve on discharge pipe of 13-P02 in order to stop EG feed to the

column. If pressure goes up continuously relieve valve PSV-13074 is opened and vapor is drained to

13-T03.

EG collection tank 13-T02 has two functions. In normal production condensate from 14-E01

and 15-E01 and drained EG from equipment in the plant are collected into the tank 13-T02. The pump

13-P03 is used to convey EG which contains a quantity of water to the column 13-C01 for separation.

Level LIC-13107 is used to regulate amount of EG conveyed to 17-T03. When the plant is shutdown

EG stored in the tanks 14-T01 and 15-T01 and 17-T01/02/03 is drained to 13-T02 in order to clean the

tanks. EG is conveyed by the pump 13-P03 from 13-T02 to 17-T03 for storing EG.

Amount of EG is stored in the tank 13-T03. Pipe led from 12-R01 and 13-C01 and 17-E03 is

immersed under the EG level. In emergency case vapor drained into 13-T03 is condensed by EG liquid

in the tank.

3.5 First stage of poly-condensation


14-R01 is a vertical tank reactor with inner and outer chambers. Coil heated by HTM liquid is



CTIEIA1




中中中中PROJECT


中中UNIT

PET MAIN PLANT



中中DISCIP.

中中PHASE

中中DATE


803-01-1903


installed inside the inner chamber. Material flows under pressure between 13-R01 and 14-R01 into the

inner chamber of 14-R01 and is discharged out of the reactor from the outer chamber. It is in vacuum

condition for 14-R01. EG produced from poly-condensation reaction and water produced from

esterification reaction are eliminated from material so that material in the reactor is in boiling state. Inthis way material is mixed completely and it is not necessary to install an agitator for mixing. The

HTM circulating pump 14-P01A/B is used to supply HTM to coil in both 14-R01 and 15-R01 and

jacket pipe between 13-R01, 14-R01 and 15-R01. Body jacket of the reactors and jacket pipe of gases

is heated by HTM vapor. The HTM evaporator 14-V01 is shared by both 13-R01 and 14-R01. Mixed

vapor from the reactor is led to the oligomer scraper 14-E01 and counter-flows with spray EG liquid.

Most of EG and part of water in vapor are condensed. A rotating blade installed at the inlet of vapor in

the oligomer scraper is used to prevent build-up of material carried by gases. Scraped material is

collected in the basket of the oligomer scraper. The basket is taken out for cleaning at regular intervals.

EG liquid in 14-T01 is conveyed by the pump 14-P02A/B through the filter 14-F01 and the heat

exchanger 14-E02A/B and then sprinkled into the oligomer scraper 14-E01 and is circulated in the

system. EG condensate in this system contains amount of water and is not proper to be used directly

and is sent to the tank 13-T02. The pump 14-P03A/B is used to generate vacuum for the reactor 14-

R01. Off-gas from the oligomer scraper 14-E01 is sucked into 14-P03A/B and part of gases is

condensed and uncondensed gases is vented out of the vapor-liquid separator. Cooling water is used

for the heat exchanger of the pump. Amount of virgin EG is added to the separator and then flows tothe tank 17-T03 by overflow.

Intrinsic viscosity of material at the outlet of the reactor reaches about 0.13.

The controlled parameters in 14-R01 include temperature and pressure and level. Material

temperature TRC-14004 is controlled by regulating amount of HTM fed to coil. Pressure PRC-14005

is controlled by regulating opening of the valve through which amount of gas is sucked into 14-

P03A/B. Material level LIC-14002 in the reactor is controlled by regulating the opening of the valve

installed on feeding pipe. Material level in 14-T01 is kept stable by regulating amount of EG fed to 13-

T02. It is not necessary to control temperature and flow rate of sprinkled EG liquid strictly.


Copyright Reserved byCTIEIA1


中中中中中中中中中中中中中

PROJECT


中中 PET MAIN PLANT



CHINA TEXTILE INDUSTRIAL


UNIT

中中DISCIP.

中中PHASE

中中DATE


803-01-1903


Indication of temperature of spray EG TI-14054 is shown on screen in the central control room and

indication of flow rate of EG PIS-14053 is shown in the site.Two sets of level indicator are installed for 14-R01. LRC-14002 is used for controlling and

setting alarm. LAHH-14003 is used to send a signal to interlock to close the valve installed on feeding

pipe in order to stop feed and at the same time close the valves on second HTM loop and primary

HTM pipe in order to stop heat supply.

3.6 Second stage of poly-condensation

See drawings 803-01-1208/1209

Material flows from 14-R01 into 15-R01 under pressure difference between tow reactors. 15-R01

is a horizontal reactor with disc rings. Material between two discs is mixed completely by stir of

rotating discs. 15-R01 is equal to a series of completely-mixed reactors in function so that reaction rate

in the reactor is increased. With disc rotation temperature of material goes about 2 from the inlet to℃

the outlet of the reactor. A piece of heating coil is installed in the side of the inlet of the reactor.

The HTM circulation pump 14-P01A/B is shared by coil in 15-R01and coil in 14-R01. The HTM

evaporator 15-V01 is used to generate HTM vapor to heat body jacket of the reactor 15-R01 and the

front part jacket of 17-R01. Process flow and control principle of the system of 15-R01 including 15-

E01, 15-T01, 15-P01A/B, 15-F01, 15-E02A/B is similar to the system of 14-R01. In order to prevent

material carried by off-gas to be condensed and then stuck to the wall of the pipe off-gas pipe is

designed to be jacket form and is heated by HTM vapor. Amount of virgin EG is added through

metering to 15-E01 for spray. Off-gas from 15-E01 is led to the jet pump 17-J01. 15-M01 is used for

lubrication in gear box of 15-R01. 15-M02 is used for cooling shaft seal of 15-R01.

Intrinsic viscosity of material at the outlet of 15-R01 is controlled about 0.25 ~ 0.30.

The controlled parameters in 15-R01 include temperature, pressure, level and revolution of disc.

Two temperature regulators are installed in the sides of the inlet and of the outlet in the reactor

respectively. TRC-15005 is used to regulate HTM temperature in the second loop. TR-15007 is used to

regulate the temperature of HTM vapor. Electrical current IR-15002 is used to be a parameter to

regulate pressure in the reactor. PRC-15024 is used to regulate amount of EG vapor sucked into



CTIEIA1






中中中中PROJECT


中中UNIT

PET MAIN PLANT

中中DISCIP.

中中PHASE

中中DATE


803-01-1903


the additional jet stage. Material level in the side of outlet in the reactor LRC-15006 is used to regulate

opening of the valve installed on feeding pipe. Revolution of disc is controlled by an inverter .

3.7 Filtration of pre-polymer

See drawings 803-01-1210

The filter 16-F01 is installed between 15-R01 and 17-R01. It has two chambers and one is in

operation and the other stands by. Pressure difference in front of the filter and behind the filter is

shown by the indicators PRC-16022 and PR-16023. The filter candles are lifted by the pneumatic hoist

16-L01. 16-P01.1/2 is a gear pump. Revolution of the pump is controlled by an inverter. The two

pumps are in operation so that it will not interrupt normal production even one of them is not in order.

PAH-16012/16013 is used to send a signal to interlock to close the motors of 16-P01.1/2 to protect the

pumps. Pressure in front of the filter PRC-16022 is used to regulate opening of the valve on feeding

pipe to control pressure of material fed to 17-R01. The HTM circulation pump 18-P02A/B is used to

supply HTM to heat body jacket of the filter and jacket pipe of material between 15-R01 and 17-R01.

Temperature of HTM liquid is set based on process requirement. Sampling valves are installed on

discharge pipe of the pumps.

3.8 Third stage of poly-condensation

See drawings 803-01-1211/1212/1213/1214/1215

The final polycondensation reactor 17-R01 is a horizontal reactor with disc rings driven by

double shafts. In the side of the inlet surface of the disc rings is not covered completely by polymer

melt and in the side of the outlet surface of the disc rings is covered completely by polymer melt so

that material level in the side of the inlet is higher than in the side of the outlet. With rotating disc rings

material temperature goes up about 4 from the side of the inlet to the side of the outlet. The HTM℃

evaporator 17-V01 is used to generate vapor to heat body jacket of the reactor. 17-M01 is used for

lubrication of the gear box of the reactor. 17-M02 is used for cooling shaft seal of the reactor.

The controlled parameters of 17-R01 include temperature, pressure, material levels and revolution

of the disc rings. Temperature records TR-17019/17020/17022 are installed at the inlet, in





CTIEIA1



中中中中PROJECT


中中UNIT

PET MAIN PLANT

中中DISCIP.

中中PHASE

中中DATE


803-01-1903


the middle and at the outlet respectively. Polymer temperature in the outlet can be controlled by

regulating temperature of HTM vapor. Electrical current of double shafts IR-17014/17027 and polymer

viscosity in discharge pipe measured by viscometer VRC-18020 are used to be the parameters to

control pressure in the reactor. Pressure in the reactor PRC-17024 is used to regulate amount of EG

vapor sucked to the first stage of 17-J01.The material level records LR-17017/17023 are installed in

the side of the inlet and the side of the outlet respectively. LIC-17016 is used to regulate revolution of

16P01.1/2 to keep stable level in the reactor. The double shafts in the final polycondensation reactor

are driven by inverters. Revolution of the disc rings is set based on process requirement.

Process flow and control principle of the system of 17-R01 including 17-E01, 17-T01, 17-F01,

17-P01A/B, 17-E02A/B, 17-E04A/B are similar to the system of 14-R01. Operation pressure in 17-

E01 is quite low. Temperature of sprinkled EG TIC-17080 is controlled by regulating amount of

chilled water fed to 17-E04A/B. Virgin EG is added by metering to17-E01. Level in 17-T01 LIC-

17078 is used to regulate amount of EG fed to 17-T03. High level alarm LAH-17078 of 17-T01 is used

to send a signal to interlock to close the valve on pipe through which virgin EG is added to 17-E01.17-J01 is a unit with four stages of EG vapor jet and three condensers. Off-gas from 17-E01 is

sucked by the first jet stage. Pressure of off-gas discharged from the third condenser is about 10 kPa.

The liquid ring pump 17-P03A/B is used to discharge off-gas from 17-J01 to atmosphere. Off-gas from

15-E01 is sucked by the additional jet stage in the unit and its vapor including sucked off-gas is led to

the second condenser. Sucked pressure of a jet corresponds with amount sucked by the jet. Volume of

off-gas from an oligomer scraper is variable in production. It is realized to keep pressure stable in the

final polycondensation reactor by regulating amount of EG sucked. Body jacket of 17-J01 is heated by

HTM vapor. HTM evaporator 17-V02 is used to generate vapor to heat body jacket of 17-J01 and

jacket pipes of gases connected to 14-R01, 15-R01 and 17-R01. 17-T02 is a liquid seal tank for 17-

J01. 17-P02A/B is a circulation pumps. 17-E03A/B is a heat exchanger in the system. Temperature of

sprinkled EG TIC-17109 is used to regulate amount of cooling water fed to





CTIEIA1



中中中中PROJECT


中中UNIT

PET MAIN PLANT

中中DISCIP.

中中PHASE

中中DATE


803-01-1903


17-E03A/B. Alarms of low flow in the three condensers FAL-17110/17111/17112 and flow of the third

condenser FIT-17112 are shown on screen in the central control room. Flow of the first and second

condenser FIS-17110/17111 is shown in the site. Level LIC-17122 of 17-T02 is used to regulate

amount of EG fed to the pump 17-P03A/B.

The liquid ring pump 17-P03A/B is used to discharge off-gas from 17-J01 to atmosphere. Chilled

water is used as cooling medium for heat exchanger of the pump. Pressure of off-gas from the third

condenser of the jet unit PRC-17141 is controlled by regulating amount of gas sucked. Part of off-gas

from 17-P03A/B is used to be sucked by the pump and the other is led to the sprinking tower 24-C01.

The EG evaporator 17-V03 is used to generate vapor to supply 17-J01. A separator 17-G01 is

installed on EG vapor pipe and a piece of pipe is designed to be jacket with HTM liquid in order to

eliminate any liquid drop in vapor fed to the jet. 17-V03 is heated by HTM liquid and is shared the

pump 17-P05A/B with 13-C01. The pump 17-P02A/B is used to convey EG condensate back to 17-

V03 and EG liquid is circulated in the system. In order to improve the quality of jet vapor certain

amount of virgin EG is added to 17-V03. FRC-17185 is used to regulate amount of virgin EG added to

17-V03. FRC-17186 is used to regulate amount of EG drained out of the evaporator. Level in 17-V03

LIC-17175 is used to regulate amount of EG circulated in the system in order to balance EG in the

evaporator. Temperature of HTM liquid fed to the evaporator is set based on process requirement.

Temperature of EG vapor TIC-17177 is controlled by regulating amount of HTM flow in heating coil

of 17-V03. Pressure alarm PAH-17172 is shown on screen in the central control room. If pressure goes

up continuously the relieve valve PSV-17173 is opened and vapor is discharge to collection tank 13-

T03.

The spent EG collection tank 17-T03 is used to collect all of spent EG including EG overflowed

from 14-P03A/B, 17-P01A/B, the system of 17-J01, EG condensate by 13-C01 from 14-E01and 15-

E01. The pump 17-P04A/B is used to convey spent EG to 11-TA01 for PTA/IPA paste preparation.

Level FRC-17149 in 17-T03 is used to regulate amount of virgin EG fed to 17-E01 so that amount of

EG in the plant can be kept in balance.

Sampling valves are installed on discharge pipe of 17-P04A/B and 17-V03.

3.9 Filtration of polymer melt





CTIEIA1




中中中中PROJECT


中中UNIT

PET MAIN PLANT

中中DISCIP.

中中PHASE

中中DATE PROCESS DESCRIPTION 中中

DWG.NO.

803-01-1903




See drawings 803-01-1216/1217

The filter 18-F01 is installed behind the polymer conveying pump 18-P01.1/2. It has two

chambers and one is in operation and the other stands by. The pneumatic hoist 18-L01 is used to lift

candles. 18-P01.1/2 is a gear pump and controlled by an inverter. In normal condition two pumps are

in operation and production can not be interrupted even in case one of them is not in order. Polymer

melt is distributed to the die heads of six chip cutters 18-CU01~06 by the four way valve 18-M04A/B

which is driven by a motor. The HTM circulation pump 18-P02A/B is used to supply HTM liquid to

body jacket of the filter 16-F01 & 18-F01 and jacket pipe of polymer & pre-polymer. Sampling valves

are installed on discharge pipe behind the pumps.

Revolution of 18-P01.1/2 SIK-18010 is used to regulate revolution of the pump 16-P01.1/2 and

drawing speed of stripe19-CU01~06 SRC-19004 & SRC-19007 to keep stable level in the final

polycondensation reactor and regulate the capacity of the cutters. High pressure alarm PAH-

18012/18014 on discharge pipe behind the pumps is used to send a signal to interlock to shut down the

motors of 18-P01.1/2 respectively in order to protect the pumps. A viscometer VY-18020 is installedon polymer pipe and measured value is used to be a parameter to control pressure in the final

polycondensation reactor. PDR-18025 is used to record the pressure difference between in front and

behind of the filter. Temperature in HTM loop of the pump 18-P02A/B is set based on process

requirement.

3.10 Chip production

See drawings 803-01-1218/1219/1220

Demi-water is used as cooling medium for a granulator. Polymer melt is sprayed out of die heads

into water and form stripes. Stripes are cut by rotating blades under water to be chip particles in 19-

CU01~06. Mixture of chips and water is separated by a sieve and chips are fed to the dryer 19-D01~06

and water flows back by gravity to the tank 19-T01. The pumps 19-P01A/B/C are used to convey

water to six cutters. Two pumps are in operation the other stands by. The heat exchangers 19-

E01A/B/C are used to cool demi-water. Temperature of demi-water TIC-19012 is controlled by

regulating amount of cooling water fed to 19-E01A/B/C. 19-F01 is used for filtration of demi-water.



CTIEIA1



中中中中PROJECT


中中UNIT

PET MAIN PLANT

中中DISCIP.

中中PHASE

中中DATE

PROCESS DESCRIPTION 中中 803-01-1903



DWG.NO.中 15 中中 23 中

SHEET 15 OF 23

PROCESS BASIC DESI. 2005.09

Some water is carried away by chips so that demi-water is supplemented to the system. Level in 19-

T01 LIC-19021 is used to regulate amount of demi-water added to 19-T01. Water on surface of chips

is taken away by blown air in 19-D01~06. The vibration sieves 19-G01~06 are used to separate

particles with off-grade size from chips. Chips from six chip production lines are collected in the chip

intermediate silo 19-H01 and 19-H02. High and low level alarms LAH-19001/LAL-19002 and LAH-

19003/LAL-19004 are installed in 19-H01 and 19-H02.

3.11 Conveying of chip

Compressed air is used as medium to conveying chip. Chip is conveyed in dense phase.

Conveying capacity is constant in operation. Low level in 19-H01 and 19-H02 is used to send a signal

to shut down the motor of the feeder and at the same time close the valve on compressed air pipe. High

level in 19-H01 and 19-H02 is used to open the valve on compressed air pipe at first and then turn on

the motor to convey chips.

3.12 Preparation of catalyst solutionSee drawing 803-01-1223

Preparation of catalyst solution is operated in batch and 10 hr/batch to meet consumption of the

plant for a day. Antimony triacetate is added through the feeding device 21-M01 to the preparation

tank 21-TA01. Virgin EG is added through the flow-meter FIQ-21005 to 21-TA01 to prepare solution

with concentration of 2%wt. Antimony triacetate is dissolved in EG at temperature about 60 .℃

Heating jacket is installed outside 21-TA01 and steam is used as heating medium. Temperature of

solution is controlled by regulating amount steam fed to jacket. Low level alarm LAL-21006 of the

tank 21-TA01 is used to send a signal to interlock to close the motor of 21-A01 to protect the agitator.

A sample is taken from 21-TA01. If concentration of solution is qualified solution is drained through

the filter 21-F02 into the tank 21-T02. Level record LR-21008 of 21-T02 is shown on screen in the

central control room. Catalyst solution is conveyed by the pump 21-P01A/B to 11-TA01. 21-P01A/B

are metering pumps. Quantity of solution added to 11-TA01 is controlled by the regulation valve FRC-

21009 on feeding pipe and the inverter. FRC-21009 is controlled by added PTA powder WT-11005.



CTIEIA1

中中DESCRIPTION

中中DESIGN

中中CHKD.

中中APPR.

定审F.APPR.

中中REV.



中中中中PROJECT


中中UNIT

PET MAIN PLANT



中中DISCIP.

中中PHASE

中中DATE


803-01-1903


3.13 Distribution of virgin EG


Virgin EG is conveyed to the plant from the storage vessel in tank farm. 21-F01 is used for

filtration of EG. The flow-meter FIQ-21003 is used to record quantity of EG fed to the plant. In

production EG is continuously fed to the liquid ring pump 14-P03, the scraper condensers 15/17-E01

and the EG evaporator 17-V03. In addition EG is added in batch to the preparation tanks 21-TA01 and

41-TA01/42-TA01/43-TA01.

3.14 Preparation of red toner solution


Preparation of red toner solution is operated in batch and once per 30 hours to meet consumption

of the plant. Red toner is added through the feeding nozzle to the preparation tank 41-TA01. Virgin EG

is added through the flow-meter FIQ-41001 to 41-TA01 to prepare solution with concentration of

1%wt. Red toner is dissolved in EG. Low level alarm LAL-41002 of the tank 41-TA01 is used to send

a signal to interlock to close the motor of 41-A01 to protect the agitator. A sample is taken from 41-

TA01. If concentration of solution is qualified solution is drained through the filter 41-F01 into the

tank 41-TA02. Level indicate LI-41004 of 41-TA02 is shown on screen in the field. Red toner solution

is conveyed by the pump 41-P01A/B to 11-TA01. 41-P01A/B are metering pumps. Quantity of

solution added to 11-TA01 is controlled by the regulation valve FRC-41007 on feeding pipe and the

inverter. FRC-41007 is controlled by added PTA powder WT-11005.

3.15 Preparation of blue toner solution


Preparation of blue toner solution is operated in batch and once per 30 hours to meet consumption

of the plant. Blue toner is added through the feeding nozzle to the preparation tank 42-TA01. Virgin

EG is added through the flow-meter FIQ-42001 to 42-TA01 to prepare solution with concentration of 0.04~0.09%wt. Blue toner is dissolved in EG. Low level alarm LAL-42002 of the tank 42-TA01 is

used to send a signal to interlock to close the motor of 42-A01 to protect the agitator. A sample is taken

from 42-TA01. If concentration of solution is qualified solution is drained through the filter



CTIEIA1



PROJECT






中中UNIT

PET MAIN PLANT

中中DISCIP.

中中PHASE

中中DATE


803-01-1903


3.18 HTM heating

See drawings 803-01-1225/1226/1227The equipment in the plant is heated by HTM liquid or HTM vapor. HTM liquid sent from the

furnaces in HTM station to the plant is called as primary HTM. HTM vapor is generated by heating of

primary HTM. The HTM circulation loops are designed to meet requirement of different equipment

for different temperature. Circulated HTM in the loop is called as second HTM. HTM temperature in a

second loop is controlled by regulating amount of primary HTM fed to the second loop. There are five

of second loop and five HTM evaporators in the plant. The equipment and jacket pipe heated by HTM

liquid or HTM vapor are shown in the table below.

heated by HTM liquid

No. Item No. of HTM pump heated equipment and jacket pipe

1 12-P01/02/03 inner coil of 12-R01

2 13-P01A/B inner coil of 13-R01 and jacket pipe between 12/13-R01

3 14-P01A/B inner coil of 14/15-R01 and jacket pipe between 13/14/15-R01

4 17-P05A/B inner coil of 13-C01 and 17-V03

5 18-P02A/B body jacket of 16-F01 and jacket pipe between 15/17-R01 body jacket of 18-F01 and jacket pipe behind 17-R01

heated by HTM vapor

No. Item No. of evaporator heated equipment or jacket pipe

1 12-V01 body jacket and jacket pipe of vapor of 12-R012 14-V01 body jacket and jacket pipe of vapor of 13/14-R01

3 15-V01 body jacket of 15-R01 and front body jacket of 17-R01

4 17-V01 behind body jacket of 17-R01

5 17-V02 body jacket of 17-J01 and jacket pipe of gas connected to14/15/17-R01



CTIEIA1






中中中中PROJECT


中中UNIT

PET MAIN PLANT

中中DISCIP.

中中PHASE

中中DATE


803-01-1903

中 19 中中 23 中SHEET 19 OF 23


In start up of the plant cool HTM liquid is fed to the second loops and is heated by primary HTM

fed to the loop step by step.

HTM collection vessel 23-T02 is used to collect drained HTM liquid from equipment. HTM

liquid in 23-T02 is conveyed by the pump 23-P02 to the collection tank in HTM station. High and low

level alarms LAH/LAL-23017 are used to send a signal to interlock to turn on and shut down the

motor of the pump 23-P01 respectively.

The expansion tank of HTM 23-T01 is installed on the roof of the building of the plant. A piece

of pipe extending to 23-T01 is connected to returning pipe of primary HTM. During start-up of the plant temperature in the second loops goes up step by step and expansion quantity of HTM liquid is

taken in by the tank 23-T01. In production gas generated from degradation of HTM is vented to 23-

T01. Material with low boiling in gas is condensed by cooling water in the jacket pipe and is drained

out at regular interval. HTM liquid in 23-T01 is covered with nitrogen in order to prevent degradation

of HTM at high temperature. Pressure alarm PIS-23003 and level alarm LAH/LAL-23008 of 23-T01

are shown on screen in the central control room.

The drained valves are installed on feeding and returning pipe of primary HTM. In case of

emergency HTM liquid is discharged to the collection tank in HTM station by opening the valves.

HTM VP-1 which is changed to HTM vapor at high temperature is stored in the collection tank 23-

T03. The pump 23-P02 is used to convey it to the evaporators. In production gas in HTM vapor is

vented to the tank 23-T03. Material with low boiling in gas is condensed in the condenser 23-E01 and

collected and drained out at regular interval. In case of accident the relieve valve installed in the

evaporators is opened and HTM vapor is discharged to the tank 23-T03. HTM VP-1 in the evaporators

can be drained to 23-T03 by opening the valves installed on pipe of vapor condensate.





CTIEIA1



中中中中PROJECT


中中UNIT

PET MAIN PLANT

中中DISCIP.

中中PHASE

中中DATE


803-01-1903

中 20 中中 23 中SHEET 20 OF 23




3.19 Cleaning of filter candles

See drawings 803-01-1228/1229

The filter candles of 16-F01and 18-F01 are cleaned in the way of hydrolysis at high temperature.

Cleaning procedure consists of hydrolysis, cleaning with alkaline liquid, cleaning with water, cleaning

with ultrasonic wave and testing with bulb.

In the cleaning tank 28-T01 polymer attached to the candles is hydrolyzed by superheated steam

whose temperature is higher than the melted point of polymer. Pressure of steam with 0.3 MPa is

decreased by a relive valve to atmosphere and is led to the heater 28-E01. 28-E01 and 28-T01 are

heated by electricity. Steam is heated by electricity in 28-E01 and temperature of steam is increased to

about 350 . Temperature of steam TIC-28016/28013 is controlled by regulating electrical power of ℃

28-E01and 28-T01 respectively. Product of hydrolysis is collected in a basket. Steam is led to the

spray tower 28-C01 and is condensed by sprinkled fresh water. Condensate is drained out as clean

waste water and off-gas is vented to atmosphere at the top of the building. Pipe between 28-T01and

28-C01 is heated by electricity in order to prevent steam to be condensed. The cover of 28-T01 can beopened only when temperature in it is decreased below 90 .℃

The electrical hoist 28-L01 is used to lift the candles out of 28-T01. The water gun with high

pressure 28-M04 is used to flush the candles. Then the candles are put into the tank 28-T03. Cleaning

agent is dissolved by demi-water in 28-T03. Temperature of cleaning solution is kept at about 120℃

in 28-T03 so that the candles are cleaned by boiling solution. Function of alkaline cleaning is to

eliminate impurity such as additive on the surface of the candles. Steam out of 28-T03 is condensed in

the condenser 28-E02 and condensate flows back to 28-T03. Cooling water is used as cooling medium

fed to 28-E02.

The candles cleaned by alkaline liquid are flushed by the water gun again and then is cleaned by

water. Demi-water is added to the tank 28-T04 and temperature of water is kept at about 100 by℃

heating coil. The candles are cleaned in boiling condition in order to remove remained impurities and

cleaning agent. A piece of jacket pipe through which cooling water is fed is used to cool steam.



CTIEIA1



中中中中PROJECT


中中UNIT

PET MAIN PLANT

中中DISCIP.

中中PHASE

中中DATE


803-01-1903

中 21 中中 23 中




The tank 28-T05 is used to collect drained liquid from 28-T03/04. Cooling water fed to coil in

28-T05 is used to decrease temperature of drained liquid. The pump 28-P01 is used to convey drained

liquid which contains alkali to the waste water pre-treatment station.

The candles cleaned by water are flushed by the water gun again and then is cleaned by

ultrasonic wave in 28-M05.

The cleaned candles are put into isopropyl alcohol solution in 28-M06 to be tested by bulb.

3.20 Stripping of esterification water


The tank 47-T01 is used to store esterification water which is the product of esterification coming

from 13-T01 is sprinkled on the top of the stripper and steam is fed to the stripper in the bottom of the

stripper. 47-C01 is a stripper with packing. In the stripper water is contacted with steam thoroughly.

The pump 47-P01A/B is used to convey the water to the stripper 47-C01. The water and acetaldehyde

is eliminated from water and is taken away by steam. The steam contained acetaldehyde is led to theHTM furnace to be burned out. Water in the bottom of the stripper is sent to the waste water pre-

treatment station by the pump 47-P02A/B. Esterification water is heated by the water from the bottom

of stripper in the heat exchanger 47-E01 and temperature of the water is decreased.

Level LIC-47001 in 47-T01 is used to control amount of water fed to 47-C01. Quantity of steam

fed to the stripper FIC-47014 is controlled to keep temperature of steam on the top of the stripper

stable(about 98 ). Level LIC-47010 is used to controlled amount of water conveyed out of the℃

stripper to keep stable operation. Record of waste water flow FIQR-47021 is shown on screen in the

central control room. Steam coil is installed on the top of the stripper to prevent steam to be

condensed. When the HTM furnace is shut down the relief valve installed on off-gas pipe connected to

the top of the stripper is opened automatically. A flame arrestor is installed at the end of off-gas pipe to

prevent fire spark in the furnace from entering into the pipe.



CTIEIA1




中中中中PROJECT


中中UNIT

PET MAIN PLANT



中中DISCIP.

中中PHASE

中中DATE


803-01-1902


3.21 Treatment of process off-gas


Off-gas from the condenser 13-E01 and the liquid ring pumps 14-P03A/B, 17-P03A/B contains

acetaldehyde , EG , air and water. It come into the sprinkling tower which is filled with packing and issprinkled by the fresh water of 18~20℃. Then most of organism inside of off-gas is taken out by

water. The waste water from the bottom of tower come into the tank 47-T01 for stripping. The gas

from the top of tower will be vented to atmosphere.

4. Safety and health data

4.1 Typical properties of the raw materials

material usage state typical properties

melt point( )℃

boil point( )℃

relativedensity

1 PTA raw material powder 300 / 1(air)

2 EG raw material liquid 中13.2 197.5 1.11(water)

3 PET product solid 260 / /

4 Therminol 66 heating medium liquid / 359 /

5 Therminol VP-1 heating medium gas / 257 /

6 Acetaldehyde by-product gas 123.8 20.8 1.52(air)

4.2 The safety data

material opera. tem.( )℃

flash point( )℃

fire point( )℃

low limita.of explosion

high limita.of explosion

1 PTA Atm. 147 678 0.03g/l /

2 EG < 80 110 / 3.2% (vol.) 15.3%(vol.)

3 Therminol 66 ~ 300 177 194 / /

4 Therminol VP-1 ~ 290 116 127 / /

5 Acetaldehyde 中 40 中39 140 4.0%(vol.) 57.0%(vol.)


Copyright Reserved byCTIEIA1



PROJECT


中中 PET MAIN PLANT





UNIT

中中DISCIP.

中中PHASE

中中DATE


803-01-1903


In production the above materials is sealed in equipment and pipe. The equipment and pipe is

regarded as released source of dangerous material. In normal operation the materials can not be

released from the equipment and pipe. In case of accident it is possible for leakage of material to

emerge but it lasts only for short time so that the equipment and pipe is regarded as the released source

of the second class according to the relevant code. The whole area of the building of the plant is

designed to be area 2 for explosive gas. The area around unloading of PTA is designed to be area 11

for explosive powder.

4.3 The health data

material taken in LC50

(mg/m3

)

through skin LD50

(mg/kg)

through mouth LD50

(mg/kg)

harm grade

1 PTA / / 3,200 medium

2 EG / 5,900~13,400 / light

3 Therminol 66 4,700 2,000 10,000 medium

4 Therminol VP-1 2,660 5,010 2,050 medium

5 Acetaldehyde 37,000 / 1,930 medium

4.4 Other harm

Radioactivity: Co60 is used to measure level in 15-R01 and 17-R01. In the area by the level

meters prevention from radioactivity is taken.

Corrosion: All material used in the production is not corrosive.



CTIEIA1



PROJECT






中中UNIT

PET MAIN PLANT

中中DISCIP.

中中PHASE

中中DATE


803-01-1902


surface of melt is increased but power consumption of disc rotating is increased greatly.

The catalyst with stibium has obvious effect on accelerating the poly-condensation rate. The

content of stibium in PET polymer has effluence on the color of the product.

2 The characteristics of the CTIEI process

2.1 Stable esterification degree is kept in esterification

In the process of two stages of esterification the esterification degree in the first stage plays an

important role for keeping the process under stable condition. In the CTIEI process it is required to

reach esterification degree about 91% in the first stage. While the esterification degree is close to the

balancing esterification degree the reaction rate becomes lower and lower so that fluctuation of the

process parameters ,such as temperature and material level in the reactor and quantities of reflux EG,

has only little effect on the change of the esterification degree. It is useful to keep esterification in

stable condition.

2.2 Pressure in poly-condensation is decreased step by step

In poly-condensation the material which is taken out of the reactors by the product with low

molecular weigh is stuck to the wall of the piping. It is a serious problem for the plant to run in stable

operation. Amount of the material taken out of the reactors depends on operation pressure and

viscosity of the polymer. Lower is pressure in the reactors and viscosity of the polymer, more is

amount of the material taken out of the reactors. In CTIEI process pressure in the three poly-

condensation reactors is controlled under 10 kPa, 1 kPa, 0.1 kPa respectively and intrinsic viscosity in

the first reactor and at the outlet of the second reactor are controlled to reach about 0.13 and 0.28

respectively. It is valid to decrease amount of the material taken out of the reactors.

2.3 Low temperature in the final polycondensation reactor

In poly-condensation temperature is a key factor to accelerate the process. But when temperature

exceeds 285 , degradation reaction rate accelerates obviously and it puts worse effect on spinning of ℃

polymer melt. In CTIEI process temperature at the outlet of the final polycondensation reactor is

controlled lower than 285 . Resident time of material in the reactors is increased due to low℃

temperature.



CTIEIA1






中中中中PROJECT


中中UNIT

PET MAIN PLANT

中中DISCIP.

中中PHASE

中中DATE


803-01-1902


2.4 EG circulation in the system

Virgin EG is fed to the oligomer scraper for the purpose of better condensation of EG and to the

EG evaporator for better jet steam quality instead of feeding it to the PTA/IPA slurry preparation tank.

The used EG called spent EG is used to prepare PTA/IPA slurry.

2.5 Two pumps for transferring material

The pumps used for transferring material including PTA/IPA slurry transferring pumps and pre-

polymer transferring pumps and polymer transferring pumps are installed for two. In this way the

material in the reactors can be discharged out when one of the pumps is out of order so that great loss

in production can be avoided.

2.6 EG vapor jet is used for generating vacuum

In the vapor jet unit one more stage is added to suck off-gas from the second poly-condensation

reactor. Compared with introducing off-gas to the first condenser blockage of polymer material in the

regulating valve on sucked pipeline is avoided. Using EG vapor as motive vapor, its condensate can be

reused in the system so that no any waste fluid is drained out of the system. It is better for environment

protection compared with using water vapor as motive steam. In addition, energy consumption togenerate EG vapor is lower than to generate water vapor.

2.7 Esterification water and process off-gas is treated

Esterification water is the product of esterification reaction and it contains acetaldehyde and other

organics from side reactions. In treatment of waste water acetaldehyde damages anaerobic bacteria. A

stripper is installed to treat esterification water. Drained water from the stripper contains no

acetaldehyde and is sent to the waste water treatment station. Off-gas from the stripper is led to the

HTM furnace to be burned out.

Process off-gas including un-condensed off-gas from the top condenser of the column and un-

condensed off-gas from the three poly-condensation reactors contains acetaldehyde. A sprinking tower

is installed to spray and absorb acetaldehyde. The waste water also is sent to the stripper for treatment.

The other un-absorbed off-gas is vented directly to the atmosphere.

3. Process flow and control

3.1 Preparation of PTA/IPA slurry





CTIEIA1



中中中中PROJECT


中中UNIT

PET MAIN PLANT

中中DISCIP.

中中PHASE

中中DATE


803-01-1902


See drawing 803-01-1201,1240

PTA as a raw material is stored in the shift silo 11-H01. Nitrogen is sent to the conical part of the

silo to prevent build-up of PTA powder. PTA doing unit consists of a rotary feeder and a vibration

sieve and a mass flow meter. PTA powder is dosed by the feeder and foreign matter in PTA powder is

separated out by the sieve. PTA powder is weighed continuously by the mass flow meter and fed to the

paste preparation tank 11-TA01.

IPA as a raw material is stored in the shift silo 40-H01. Nitrogen is sent to the conical part of the

silo to prevent build-up of IPA powder. IPA powder is weighed continuously by IPA doing unit to the

paste preparation tank 11-TA01.

PTA/IPA powder is mixed with added EG and catalyst & additive solution thoroughly to form

homogenized slurry suspension with the help of the propel type impeller 11-A01. The paste pumps 11-

P01.1/2 are screw type. Tow pumps are in operation at the same time. Slurry is fed to the first

esterification reactor 12-R01. A flush valve is installed on pipe line to flush with EG liquid in order to

prevent blockage on slurry pipe. A sampling valve is installed on the slurry pipe.

Molar ratio in slurry is controlled for preparation of PTA/IPA slurry. Amount of EG and catalystsolution fed to 11-TA01 is controlled by dosing of WT-11005. A density meter DI-11023 is installed on

slurry pipe to indicate molar ratio.

Low low level alarm of 11-TA01 is used to send a signal to interlock to close the agitator.

High pressure alarm PAHH-11018/11020 on slurry pipe is used to send a signal to interlock to

shut down the motors of 11-P01.1/2 to protect the pumps.

3.2 First stage of esterification


Slurry fed to 12-R01 is heated by coils installed inside of the reactor and temperature of material

is increased. Water produced from the reaction with vaporized EG is led to 13-C01 to be separated.

Heat consumption of 12-R01 is the maximum one in the plant. Heating coil is heated by HTM liquid.

Three pumps (12-P01A/B/C) are installed in the second HTM loop. Two of them are in operation and

the other stands by. The body jacket of the reactor and jacket pipe of mixed gas are heated by HTM





CTIEIA1



中中中中PROJECT


中中UNIT

PET MAIN PLANT

中中DISCIP.

中中PHASE

中中DATE


803-01-1902




vapor. Main function of 12-A01 is to strengthen heat transfer. Revolution of 12-A01 is adjustable. A

sampling valve is installed on discharge pipe of 12-R01.

Esterification degree in 12-R01 is controlled to be about 91%.

A little of degradation of HTM liquid takes place in usage. Ventilation pipe is installed at the

highest point in the second HTM loops. The valves should be opened at regular interval to vent out

materials with low boiling. In emergency case the valves located in the bottom of the strainer of the

HTM pumps can be opened so that HTM liquid in the second loop is drained to the collection tank 23-

T02.

A HTM evaporator is heated by primary HTM. Vapor is led to the heated equipment and

condensate flows back to the evaporator by gravity. Ventilation pipe is installed at the highest point in

the loop. A vapor-liquid separator is used to separate them. Condensate flows back to the evaporator

and gases is led to 23-T03.

The controlled parameters in 12-R01 include temperature and pressure and material level and

molar ratio. Temperature of material in the reactor is the key parameter for controlling esterificationdegree. Temperature of material is controlled by putting material temperature TRC-12012 with HTM

temperature TIC-12004 in series to regulate amount of primary HTM fed to the second loop.

Temperature of HTM vapor is controlled by regulating amount of primary HTM fed to 12-V01.

Pressure PRC-12013 in the reactor is controlled by regulating opening of the regulate valve. LIC-

12009 is used to keep stable level in 12-R01 by regulating speed of 11-P01 to control amount of fed

slurry.

Two sets of level indicators are installed so that material level in the reactor is supervised all the

time. LAHH-12009 is used to send a signal to interlock to close the three-way valve on slurry pipe and

the valve on EG reflux pipe in order to shut down feeding. LALL-12019 is used to send a signal to

interlock to shut down the motor of 12-A01 to prevent damage of the impeller. PAHH-12013 is used to

send a signal to interlock to close the valves installed on primary HTM pipe and the valve installed on

primary HTM pipe of 12-V01 and shut down the motors of 12-P01A/B/C at the same time so that no

heat is supplied to the reactor. If pressure goes up continuously relieve valve PSV-12031 is



CTIEIA1



中中中中PROJECT


中中UNIT

PET MAIN PLANT

中中DISCIP.

中中PHASE

中中DATE


803-01-1903

中 17 中中 23 中




42-F01 into the tank 42-TA02. Level indicate LI-42004 of 42-TA02 is shown on screen in the field.

Blue toner solution is conveyed by the pump 42-P01A/B to 11-TA01. 42-P01A/B are metering pumps.

Quantity of solution added to 11-TA01 is controlled by the regulation valve FRC-42007 on feeding

pipe and the inverter. FRC-42007 is controlled by added PTA powder WT-11005.

3.16 Preparation of heat stabilizer solution


Preparation of heat stabilizer solution is operated in batch and once per 30 hours to meet

consumption of the plant. Heat stabilizer is added through the feeding nozzle to the preparation tank

43-TA01. Virgin EG is added through the flow-meter FIQ-43001 to 43-TA01 to prepare solution with

concentration of 1%wt. Heat stabilizer is dissolved in EG. Low level alarm LAL-43002 of the tank 43-

TA01 is used to send a signal to interlock to close the motor of 43-A01 to protect the agitator. A

sample is taken from 43-TA01. If concentration of solution is qualified solution is drained through the

filter 43-F01 into the tank 43-T02. Level indicate LI-43004 of 43-T02 is shown on screen in the field.

Heat stabilizer solution is conveyed by the pump 43-P01A/B to 11-TA01. 43-P01A/B are metering

pumps. Quantity of solution added to 13-R01 is controlled by the regulation valve FRC-43007 on

feeding pipe and the inverter. FRC-43007 is controlled by added PTA powder WT-11005.

3.17 Preparation of DEG


DEG is conveyed to the plant from the storage vessel in tank farm. Quantity of solution added to

11-TA01 is controlled by the regulation valve FRC-44004 on feeding pipe and the inverter. FRC-

44004 is controlled by added PTA powder WT-11005.



CTIEIA1


process description(final)[1]

Documents

polycondensation reaction

reaction materials

reversible balance reaction

thermal degradation

reaction rate constant

maximum esterification

high esterification

polycondensation process