Installation of the Halar/FRP Liner
Tunetanken, the Danish FRP fabricator, was selected to do the fabrication of the Halar inner liner. The 4.3-m-diameter/112-m-high stack was relined with seven modular sections, each about 14 m high. The Halar/FPR sections were prefabricated using 2.3-mm-thick Halar fiber-backed sheets from Quadrant (formerly Symalit), which were assembled to a total height of 92 m. The individual prefabricated sections were introduced and lowered into the chimney from the top by a crane capable of operating at heights of 120 m or higher (Figure 6).
6. Stack gets stacked liner. Seven prefabricated stack liner sections, each about 14 meters high, were dropped into place by crane to line the entire stack. Courtesy: Solvay Solexis
Each Halar module was constructed with a male socket sleeve at the bottom, which fit the female top of the section below. These sockets were then bonded in place with high-temperature adhesive, and the various modules were welded together by experienced PRP welders, operating from scaffolding platforms mounted inside the stack. (In 1995, Tunetanken was relatively new to Halar lining and welding; consequently, Halar expertise was provided by subcontractor PRP from Finland.) The total weight of Halar ECTFE resin used to produce the fiber-backed sheet of 2.3-mm nominal thickness for this project was estimated to be 5 metric tons.
Initial work started at the end of August 1995, and by October 1995 the stack was ready to enter service.
Liner Performance
Start-up of the power station with its new stack liner took place in November 1995. Since then, the plant has operated between 80% and 90% of the time. No maintenance or repairs have been performed since the liner was installed. Inspection of the chimney stack performed by Tunetanken personnel in September 2006 confirmed that the Halar liner was in excellent condition and looks practically new (Figures 7 and 8).
7. Just like new. The light brown discoloration of the Halar polymer at the inlet of the chimney and on part of the flexible joint was caused by exposure to the high-temperature gases exiting the furnace. However, this discoloration did not affect the polymer properties, and the liner maintained its excellent corrosion protection properties. The black stain visible on the edge of the inlet is a paint used for other parts of the chimney. The white residue present on the bottom of the inlet was easily wiped off. Courtesy: Solvay Solexis
8. Smooth sailing. Inspections of the manhole and the bottom part of the chimney during a September 2006 inspection confirmed that all parts of the liner showed no signs of chemical attack on the ECTFE resin by the chemically aggressive exhaust gas and that no cracking was present on the surface of the liner. Courtesy: Solvay Solexis
The liner was further evaluated by the Danish Technological Institute (DTI) in 2008. Results of the DTI evaluation showed that the liner was in excellent condition after approximately 13 years of service. The DTI’s conclusions were summarized in the May 2009 letter from Mr. Torben Martens Knudsen, project manager of DTI’s Plastics Technology: "Samples taken from the ECTFE lining of the stack at Nordjyllandsvaerket Power Plant have been tested last year. Two drilled out samples were taken at level 24 and analyzed using infrared-spectroscopy at test samples taken from inside surface and from the middle part of the lining. There were no signs of degradation of the polymer. Polished cross-sections of the samples were examined in microscope; a darker color was observed in a depth of 0.1 mm from inside surface. The joint between lining and glass fiber-polyester layer was fully intact. It was concluded that the ECTFE-lining was not influenced by the service conditions after approx. 13 years of service."
-Contributed J. Karol Argasinski (karol.argasinski@solvay.com), market development manager for Solvay Solexis Inc. and Marcel E. Loosbergh, director of M.E.L. Consultants, Overijse, Belgium
[Editors' note: Minor corrections in product naming were made to the online version of this article 12/10/09.]
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