This facility manufactures amorphous PET resin, PET bottle chip, and polyester staple.
This plant uses a continuous process to produce polyester staple fiber and chips with the basic raw materials being ethylene glycol, Terephthalic acid and a catalyst. Production is maintained by three separate monomer trains located in Building H. The monomer trains feed 12 Polymer lines.
There are several ducts on various roofs that are insulated with polyurethane insulation. Polymer lines 1– 7 produce approximately 500,000,000 lbs. per year of polymer used in the production of polyester staple. Polymer lines 8 and 9 produce approximately 145,000,000 lbs. per year of amorphous polymer.
Polymer line 8 produces amorphous chip for use in fiber production. Line 8 is currently shutdown and is to be converted to produce amorphous chip for bottle resin. Polymer line 9 currently produces amorphous resin for bottle chip; however, this line is rarely run due to limited capacity in the SSP Plant.
Polymer lines 10 – 12 produce approximately 500,000,000 lbs. per year of polymer with approximately 420,000,000 supplying the solid state polymerization process and approximately 80,000,000 being sold to an outside customer.
Polymer Production: The chemical process to produce polyester from ethylene glycol and terephthalic acid is done in three separate monomer trains of continuous process equipment located in Building H.
The ethylene glycol and terephthalic acid are pumped into the primary esterifier which is heated by an HTF (heat transfer fluid) jacket to about 260°C at 40 psig pressure. The vessel is provided This facility manufactures amorphous PET resin, PET bottle chip, and polyester staple.
This plant uses a continuous process to produce polyester staple fiber and chips with the basic raw materials with a rupture disc and a relief valve in series. The mixture is continuously agitated and the small amount of water formed during the reaction is removed. This is an endothermic reaction. Excessive vibration switches and alarms are provided. The material (bishydroxy ethylene, BHET) is pumped to the secondary esterifier, which operates at 3 psig pressure at about 275°C with a HTF jacket. The excess unreacted ethylene glycol is boiled off, vapors condensed and recovered. The BHET monomer is transferred to one of 12 polymer lines. There are cross connections after the esterification process to allow each esterifier line to feed any of the polymerization lines.
Polymer lines 1 – 12 each begin with a low polymerizer (LP) which operates under a slight vacuum at 295°C. Ethylene glycol and off gas are removed from the LP vessel by steam jet vacuum and piped to the glycol recovery unit in the yard. For polymer lines 1 – 7 the in-process polymer is transferred to a high polymerizer (HP) which operates at 290°C under a vacuum with off gas being condensed in the steam jet vacuum system and then sent to glycol recovery. The two polymerizers are mounted horizontally on concrete pillars.
The polymer then flows to an extruder, which increases the pressure to 400 psi to feed a manifold of spinnerets. These seven polymer production lines feed spinning machines for staple production. Polymer lines 8 – 12 have an intermediate polymerizer between the high polymerizer and the low polymerizer. The intermediate polymerizer operates in the same way as the LP and HP except the operating temperature and pressure is between the temperature and pressures used on the LP and HP. On these lines the polymer is pumped through spinnerets which produce strands of polyester, which are cooled in a water bath.
The strands are chopped, then conveyed pneumatically to silos in the yard for storage and then either further processed in the solid state polymerization or processed through a crystallizer prior to being stored in silos prior to shipment. The crystallizer is a heated oven that the pellets pass through on a conveyor to alter their intrinsic viscosity and enhance their molding properties. From the crystallizer the pellets are pneumatically conveyed to storage silos for bulk shipment by road mainly to another plant.
The remainder of the pellets passes through a series of pre-crystallizers, similar to crystallizers, prior to being pneumatically conveyed to the solid state polymerization plant.
Staple Fiber Production: From the extruders, molten resin is fed to a total of seven fiber spin beams in Building H. Each spin beam has a total of 24 spin packs, which are heated using the heat transfer fluid system. The spin packs are dies with many small holes and each pack receives a metered supply of polymer paste, which is forced through the holes to form fiber strands of the proper size. The strands of polymer paste then fall by gravity to a take up unit. As the strands fall they are air cooled and a spin finish is applied. The fibers are then gathered together to form a tow band which is then transferred to creel cans in Building J to await further processing.
The tow bands are then pulled from the creel cans and routed overhead to draw machines where it is heated, washed, and stretched. The tow is crimped, and then deposited 1-in. to 2-in. high on a metal conveyor and passes through a steam-heated oven. The tow is cut to the desired length on a rotary cutter and then pneumatically fed into a bale press. The bales are transported by automatic conveyors to Building W.
Sprinkler protection in Building J is designed to provide 0.20 gpm/sq. ft. over 3,000 sq. ft. The spin pack and quench section of Building H are provided with hose station for manual fire fighting and no automatic sprinkler protection.
Solid State Polymerization: Solid state polymerization (SSP) process takes place in the SSP Building. There are three SSP production lines in this area. Chip from the amorphous chip silos is transferred to feed bins for the SSP process. The SSP process involves heating the chips with hot air and nitrogen to increase the polymer chain length and to remove impurities.
The chip is first fed into a pre-crystallizer feed silo then is metered into the pre-crystallizer where the chip is heated to approximately 150°C with a chip residence time of approximately 15-minutes. The chip is then fed into the crystallizer where the chip is heated to approximately 185°C with a residence time of approximately 30-minutes. Both the Precrystallizer and the crystallizer are heated using steam-heated air.
The chip is then fed into the preheater feed hopper and then to the pre-heater where the chip is heated to approximately 220°C and has a residence time of approximately 8-hours.
The chip is then fed into the reactor feed hopper and metered into the reactor. The reactor maintains a temperature of approximately 200°C with a residence time of approximately 18-hours. The pre-heater and reactor use hot nitrogen to heat the chip. The chip is then cooled in a product cooler. The finished product (polyester bottle chip) is pneumatically conveyed from the SSP plant to outside storage silos. From the storage silos the bottle chip is shipped, mainly for the production of PET bottles, in bulk via road or rail.
The nitrogen gas used in heating the chip in the preheater and reactor has to be cleaned prior to being reused in the process. In the process, a certain amount of water vapor is created in the nitrogen gas stream, which is removed in platinum bed reaction scrubbers. Air is introduced in this stage and nitrogen and oxygen leave the platinum bed reaction scrubber. The oxygen in this gas stream must be removed prior to reusing the nitrogen in the gas stream.
To remove the oxygen, a small amount of hydrogen is fed into the nitrogen gas stream prior to going through a palladium catalyst bed scrubber. The hydrogen supply is automatically shutdown upon hydrogen detection. Gaseous hydrogen is fed to the process from bulk gaseous hydrogen trailers to the process at a very low flow rate. The first floor area where hydrogen is used is open-sided, has LEL detectors and classified electrical equipment. There is no heat transfer media used in this building. Due to minimal combustible loading, sprinkler
protection is not needed in this area. An automatic carbon dioxide gaseous protection system is provided beneath the raised floor in the SSP control room.