For the fourth time since it was built in 1964, Elf Atochem's plant in Calvert City, KY has undergone an expansion. The most recent project arose from growing worldwide demand for polyvinylidene fluoride (PVDF) resin. The plant is the only vertically integrated fluorochemicals operations in the world.Atochem mines its own fluorspar and converts it into hydrogen fluoride, a key raw material in the production of fluorocarbons and fluoropolymers. The company chose to concentrate the manufacture of its PVDF engineering polymer at this site by increasing capacity 35%. The expanded facility features increased drying and extrusion capacity and a more efficient distributed control system. New automated packaging equipment allows product shipment in more sizes to suit customer requirements more easily.
Atochem's Kynar PVDF is often used in high-purity applications such as pharmaceutical and semiconductor manufacturing. Accordingly, the plant needed to ensure that strict quality standards are maintained in every step of the process. A deionized (DI) water rinse removes residual catalysts and surfactants from the latex that contains the polymer. This is a crucial part of the operation. So that impurities from corrosion of metal components do not enter the DI water stream the prime contractor, Apex Engineering Inc., used only solid PVDF or PVDF lined components.
Roger Smith, project manager for Apex says, "When building a system for washing a high-purity polymer like PVDF it makes perfect sense to construct it using the same resin." Some material is manufactured from homopolymers and some from copolymers made with hexafluoropropylene and vinylidene fluoride. The copolymer has greater flexibility with chemical resistance comparable to that of the homopolymer.
The water is deionized in three ion-exchange vessels. First it flows through a vessel containing a cation resin bed. The water then passes through an anion bed. The third vessel contains both cation and anion resins for trace-ion removal. Because this last mixed-resin bed is regenerated with alternating rinses of hydrochloric acid and 4% caustic, the vessel is PVDF copolymer-lined steel. The systems piping includes solid schedule 80 PVDDF pipe, as well as lined steel pipe and fittings. Fabricated PVDF spaacers are used for instrument adapters and sample point fittings. The effluent ultrapure deionized water has a typical resistivity exceeding 18 megohms (by comparison typical pharmaceutical-grade DI water has a resistivity of 10, and ordinary drinking water has less than 1. Eventually this value declines and the bed must be regenerated. Normally, regeneration is required only about once a month.
Having been through so many startups in the past, plant personnel experienced the usual anxiety when the new facilities were to be brought on line. The DI water system performed flawlessly from the beginning. Startup of the Kynar unit was scheduled for a particular day in July.
"We came in at 5 a.m. on the day of the startup," says Jack Sturm, staff project engineer with Atochem. "We put the process on the DCS, and it took off. By 9 a.m. our first batch came off and it was in spec. It was the most fantastic startup we've ever had."