The polyester reactor is the core equipment in the polyester synthesis process, and its operational details directly affect product performance, production efficiency, and safety. The following elaborates on the key points of use from the aspects of equipment preparation, operation process, parameter control, safety maintenance, etc.

1、 Equipment preparation and inspection

1. Material confirmation

-The main body of the reaction vessel should be made of corrosion-resistant materials (such as 316L stainless steel or titanium alloy) to resist the acidic environment in polyester reactions (such as by-products produced by PTA oxidation).

-Components that come into contact with materials, such as agitator blades, condenser tubes, and temperature probes, should be regularly inspected for corrosion to avoid contamination or leakage caused by material degradation.

2. Sealing test

-Before feeding, it is necessary to conduct pressure tests on the sealing parts such as flanges, valves, and pressure gauges of the reaction kettle (usually 1.1 times the design pressure) to ensure no leakage.

-High temperature resistant silicone grease should be applied to the mechanical seal, and the cooling water circulation system should be checked for smoothness to prevent leakage of high-temperature melt.

3. Cleanliness guarantee

-The inner wall of the reaction vessel needs to be cleaned with solvents (such as ethylene glycol or specialized cleaning agents) to remove residues and avoid impurities from the previous batch affecting the new reaction.

-After cleaning, it is necessary to blow with nitrogen to remove moisture and residual oxygen.

2、 Feeding and Reaction Control

1. Feeding sequence and ratio

-Main raw materials: Accurately weigh ethylene glycol (EG) and terephthalic acid (PTA) according to the formula ratio, and give priority to adding EG to dissolve PTA and reduce dust flying.

-Catalyst: Evenly disperse and add (such as antimony acetate or antimony trioxide) to avoid excessive local concentration that may cause side reactions.

-Additives: Stabilizers (such as triphenyl phosphate) and matting agents need to be added at specific stages to prevent high-temperature decomposition.

2. Temperature and pressure control

-Esterification stage: carried out at low temperature (180-250 ℃), recovering volatile EG through reflux condenser, controlling pressure of 0.1-0.3 MPa to prevent severe boiling.

-Condensation stage: gradually raise the temperature to 270-290 ℃, reduce the pressure to ≤ 100Pa, promote the discharge of low molecular weight substances (such as water), and at the same time, start strong stirring (speed 100-200rpm) to prevent local overheating.

-PID temperature control system: using proportional integral derivative algorithm to adjust heating power in real time, with temperature difference controlled within ± 2 ℃.

3. Mixing and heat transfer

-The agitator blade shall be of propelling or turbine design to ensure uniform mixing of materials and avoid local gel or degradation.

-The temperature of the jacket heat transfer oil or steam should be slightly higher than the material temperature (if set at 285 ℃, the temperature of the heat transfer oil should be controlled at 290 ℃), and temperature control should be assisted by a serpentine cooling coil.

3、 Key operational details

1. Nitrogen protection

-Introduce inert nitrogen gas (flow rate 5-10L/min) throughout the entire process to eliminate oxygen and prevent oxidative degradation, while suppressing EG evaporation.

-A filter should be installed at the nitrogen inlet to prevent impurities from blocking the pipeline.

2. Fractional recovery

-The mixture of water and EG generated by esterification reaction is recovered through a condenser, and after separation, EG can be recycled to reduce raw material consumption.

-Regularly clean the condenser pipes to prevent polymer blockage.

3. Monitoring of melt viscosity

-Real time monitoring of melt flowability through online viscometer. When the viscosity suddenly increases, it is necessary to reduce the stirring speed or supplement EG to avoid motor overload.

4、 Safety and emergency response

1. Overpressure and explosion protection

-Install safety valves (with a popping pressure ≤ 1.2 times the design pressure) and rupture discs to automatically release pressure when the pressure loses control.

-Configure an emergency cooling system that can lower the temperature to below 200 ℃ within 30 seconds.

2. Power outage and fault response

-In case of sudden power outage, immediately turn off the heating system and activate the backup power supply to maintain stirring and prevent melt solidification.

-If the mixing stops, manually clean the semi molten material in the kettle within 1 hour to avoid clumping and damaging the equipment.

3. Personnel protection

-Wear insulated clothing, corrosion-resistant gloves, and a face mask during operation to avoid contact with high-temperature melt or steam.

-Regularly monitor the concentration of EG in the air around the reaction vessel (occupational exposure limit ≤ 20ppm) to prevent poisoning.

5、 Maintenance and upkeep

1. Post reaction processing

-After discharging, use a scraper to clean the polyester residue adhering to the kettle wall while it is hot, rinse with cold water, and dry for later use.

-Disassemble and inspect vulnerable parts such as mixing shafts and sealing rings every 50 batches, and replace aging components.

2. Long term suspension management

-Inject anti rust oil to seal the reaction vessel, disconnect the power supply, and mark the "disabled" status.

-Start a no-load operation once a month to prevent seal adhesion.

6、 Quality Control and Records

1. Parameter recording

-Continuously record temperature, pressure, stirring speed, nitrogen flow rate, and other data to form trend curves for analysis.

-Sampling and testing of color (b value), viscosity (IV value), carboxyl end group content, and other indicators for each batch, optimizing process parameters.

2. Abnormal analysis

-If bubbles or gel particles appear in the product, it is necessary to backtrack whether the mixing speed and heating rate are abnormal.

-Regularly calibrate temperature sensors and pressure gauges with an error of less than ± 0.5%.