Rockwood rises to the challenge
Because the manufacturing process releases wastewater containing salts, the Seveso 2 class plant had to alter its facilities. Alterations have been so efficient that ADEME awarded a national second prize to the company for economical and clean technologies, at the 2003 Pollutec Show last December. Semiconductor manufacturers use ultra pure chemical products to etch their silicon wafers. The job of the Saint-Fromond-based Rockwood Electronic Materials plant in the Manche département is to make the widely known chemicals, called hydrochloric and nitric acids, ammonia, and ammonium fluoride. "Our expertise is to ultra purify the products with distillation processes or with specially powered ion-exchange resin beds," explained Philippe Calot, Director for Operations of the group in France. He is in charge of all the plants and ultra pure chemical depots in the country. At the Seveso 2 class Saint-Fromond facility six to seven million liters of the ultra pure chemical products are produced every year, amounting to roughly 10,000 tons. The only problem is that production generates approximately eighty tons of washing and flushing wastewater containing salt to the amount of 50 grams per liter. Recycling 90% of the Wastewater The problem is critical because since 1982 the plant has been located in an environmentally sensitive area that was incorporated into the Contentin and Bessin Wetlands Park in 1990. Direct discharges into the park are prohibited. So every year until 2002, 40 to 45 tanks of wastewater were conveyed to a plant in Lillebonne (Seine-Maritime département). The yearly cost of the operation amounted to 171,000. However, Philippe Calot found the solution economically and environmentally unsatisfactory. "How can you agree to pay that kind of money when you know that only one-third of the salt load was being eliminated and the rest was being dumped in the Seine Bay," he explained. In the late nineties, the decision was made to work with a German company to develop an original process. Because of the very high initial salinity of the wastewater, the reverse osmosis process was trashed. They opted for evapoconcentration, a standard solution that is tricky to implement because of the aggressive products in the wastewater. "We opted for a carbon exchanger, or more accurately, a resin with a high carbon content," explained Philippe Calot. The first tests were disappointing. Crystallization formed in the fragile exchanger, breaking the tubes that had to be constantly fixed. Numerous laboratory tests had to be run before an original solution was found to prevent crystallization in the tubes. More details about the process will not be forthcoming since Philippe Calot will say no more about it to protect a know-how that might interest his customers. It took six long months of hard work to make the necessary adjustments of the equipment. "It wasnt easy to find a balance. The result couldnt be too alkaline lest we release ammonia or too acid lest we release hydrochloric acid, for instance." In any case, the results prove the efficiency of their solution. Only four tanks of wastewater left the Saint-Fromond plant in 2003. "We recycle virtually 90% of our wastewater. The water we produce is even a bit better than city water," he pointed out. The operation, which was subsidized by the region, cost 275,000 including 220,000 for the evapoconcentration equipment. Always one step ahead in technology The operation has received several prizes, including the ADEMEs national second Prize for economical and clean technologies awarded at the 2003 Pollutec Show. The operation is part of the overall strategy of the plant that is the only facility in France with true ultra purification capabilities. "Our goal is to always be a step ahead in the technology of our field. That is why four people out of the fifty working at the plant are assigned to R & D," explained Philippe Calot. The chemical engineer added that technologists accounts for 60% of the staff at Saint-Fromond. The facility also has one of Frances two or three best equipped laboratories for ultra pure product screening. Rockwood actually ranks number one in analytical capabilities of ultra pure water. "We have analysis contracts with the biggest names in semiconductors that send us samples, especially from the South of France. We accomplish technological feats daily for them so they can have results in record time." The small facility nestled in an outstanding environment can rightly be proud of its performance. Contact,Philippe Calot, Director for Operations, France,Rockwood Electronic Materials,Phone +33 (0)2.33.75.64.00 Fax. +33 (0)2.33.55.45.27,e-mail: pcalot@rockemat.com,http://www.rockemat.com/ Source : ScienceTech Basse-Normandie Newsletter,http://www.basse-normandie.net/lettre,free subscription: http://listes.cru.fr/wws/info/sciencetech.basse-normandie.en
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