Conference on developments in desalination technology
Project Date: 2016
Products: ECTFE sheet glass fabric backed 2,3 mm thickness, ECTFE sheet natural 10 mm thickness, ECTFE welding rod 3 / 4 mm, ECTFE Pipe 25 / 32 / 63 / 90 / 110 mm SDR 21, ECTFE Stub Flange 32 / 63 / 90 / 110 mm SDR 21, ECTFE Union connection 32 mm SDR 21, ECTFE Bend 90° / 110 mm SDR 21, ECTFE Tee 32 mm SDR 21
Medium: Industrial exhaust gases
Plant engineering company: HESON Metall- und Kunststofftechnik GmbH
The neutralisation of industrial exhaust gases is a laborious matter. The contaminated exit air arising in the production of certain chemicals must often be cleaned in a “scrubber” before it is emitted into the environs. Until recently, one chemical company used an internally rubberised steel tank filled with plastic balls for the task. At a certain temperatures, the gas condenses on the plastic balls and then collects at the bottom of the tank in liquid form. Although the cleaning of the exhaust air worked perfectly with this method, the rubberised inner lining of the tank had to be serviced and partly renewed at relatively short intervals due to the aggressiveness of the medium. In order to eliminate these cost-intensive maintenance intervals and increase plant availability, the company sought a long-term and reliable solution. The plant engineers at HESON in Vorchdorf, Austria, were charged with the task and delivered a solution using the extremely chemical-resistant fluoroplastic ECTFE. HESON decided to work together with AGRU Kunststofftechnik GmbH because the specialist in synthetic materials from Bad Hall, Austria, is the only supplier worldwide that provides ECTFE plate or sheet materials (with and without lamination), piping, fittings and valves from a single source. This joint project resulted in the development of a gas scrubber “made in Upper Austria”.
The tank with a diameter of 1.05 m and height of 12 m was made as a dual laminate construction. In this design, an inner lining of laminated ECTFE sheeting provides highest chemical resistance. Thanks to its thermoformability and good weldability, ECTFE can be processed simply and safely, and boasts optimum chemical resistance at temperatures up to 140 °C. On the outside, glass fibre reinforced plastic (GRP) gives the construction the necessary stability.
The dual laminate construction thus lends the gas scrubber its high strength and robustness, while simultaneously reducing its weight significantly in comparison to a solution with a steel tank. The inner lining of ECTFE offers long-term protection against exhaust gases and chemicals, increases operational reliability and only needs replacement after years of continuous duty. Due to its high operational reliability and long service life, the ECTFE scrubber offers the best price-performance ratio, because the somewhat higher initial investment in the ECTFE scrubber pays off in the long run thanks to the low costs for maintenance and repair.
The gas scrubber column was designed and planned by HESON. AGRU clarified the question of ECTFE chemical resistance and delivered all the ECTFE components needed to manufacture the column such as glass-backed laminated plates, natural plates, welding rods, piping and fittings. Due to its overall height of 12 m, the tank was constructed in 4 segments and joined together with leak-tight screw connections. For the GRP composite construction, glass-backed ECTFE liners were shaped by thermoforming and welding. Due to the low inherent stability of the 2.3 mm thick foil, a framework was used to give internal support. In a further processing step, a GRP reinforcing complex was applied to the fabric backing facing the outside. In order to be able to test the leak tightness of the lining laminate by means of high voltage, carbon fibres were laminated into the construction next to all welds as an electrically conductive layer. After successful testing of the leak tightness and quality of the welds, HESON installed the tank at the customer’s facility. Just two months after placing its order, the chemicals company was able to commission the gas scrubber “made in Upper Austria” in October 2016.
Due to their high chemical resistance and broad operating temperature range, the fluoroplastics PVDF, ECTFE, FEP and PFA processed by AGRU are ideal for high-end applications in apparatus construction and plant engineering. The fluoroplastics are characterised by the following properties:
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