Products Finishing

JAN 2013

Products Finishing magazine is the No. 1 industrial finishing publication in the world. We keep our readers informed about the latest news and trends in plating, painting, powder coating, anodizing, electrocoating, parts cleaning, and pretreatment.

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PartscleANiN g Mechanical Vapor Recompression Evaporation Eco-fRiEndly wastEwatER tREatMEnt pRocEss is undERutilizEd in finishing. By Robert Burns M echanical vapor recompression evaporation (MVRE) has been used in the manufacturing industry for decades for such purposes as desalinating sea water, concentrating juices and treating wastewater on large industrial scales. During that time, the technology has evolved somewhat, specifically in Europe where water and energy conservation are more regulated. As it stands, MVRE is underutilized in the treatment of industrial wastewaters that are typical of metal fabricating and finishing industries. Until recently, businesses have relied on technologies such as membrane filtration, atmospheric evaporators, chemical treatment and flocculation, and others. Increasing energy costs, rapidly decreasing freshwater resources and growing sensitivity towards the environmental impact of industrial management practices are the driving forces in the development of more sustainable technology. distillation pRocEss REcoVERs watER MVRE is essentially a distillation process designed to reduce wastewater volumes by recovering most of the water in the waste. Typically the waste is concentrated by as much as 20:1, and the concentrated waste can then be hauled away by local authorities, or dried and buried in a landfill. The recovered water or distillate is of good quality and can be used in a variety of industrial applications, from rinse water to boiler feed water, or it can be simply disposed of into the sewer. Distillation in itself is a separation process, separating components in a mixture by making use of the fact that some components vaporize more readily than others. The vapors produced by heating the mixture contain the more volatile components of the original mixture, and so a separation process occurs. MVRE takes the process one step further by using a compressor to increase the pressure of the water vapor, or steam, produced. An increase in vapor pressure increases the condensation temperature of the steam, rendering it usable to heat the original mixture in a heat-transfer apparatus. It is this resulting temperature difference produced by compressing the steam that enables a highly efficient heat transfer to occur. As the steam condenses in the heating chamber, it releases its latent heat of vaporization to further heat the original Mechanical vapor recompression process diagram. (Image courtesy of Proceco Ltd.) 30 JANUARY 2013

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