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Pollution Prevention and Control Technologies for Plating Operations
Section 3 - Chemical Recovery
3.2 ATMOSPHERIC EVAPORATORS
3.2.2 Development and Commercialization
Atmospheric evaporators are essentially adjuncts to plating tank evaporation. They increase the head room in the plating tank, thereby increasing the quantity of rinse water/drag-out that can be recovered using recovery rinsing. The use of recovery rinsing in the plating industry was documented more than 50 years ago. The use of evaporators for chemical recovery extends back more than 40 years (see reference list in ref. 1). Most of the early evaporators used by the plating industry were the vacuum type, which was basically a technology transfer from the chemical processing industry. These were large units, often with capacities of 400 to 600 gph (1,500 to 2,300 l/hr). Large units were used because water conservation and pollution control were less important at that time, resulting in higher flow rates. Also, energy was much less expensive at that time and therefore there was less incentive to minimize flows prior to evaporation. In 1974, with the advent of rapidly rising energy costs, there began a movement to down-size recovery systems (ref. 300). Coupled with the Federal pollution control standards, first promulgated in 1979, plating shops turned to the small and inexpensive atmospheric evaporators for chemical recovery. Based on the results of the Users Survey, it is apparent that purchases of this technology have continued into the 1990's.
There are approximately 25 companies that manufacture evaporative recovery equipment applicable to the plating industry. This includes vacuum and atmospheric evaporators for both chemical recovery and waste concentration (ref. 421). The firms most often mentioned in the Users Survey were Poly Products Corporation, Techmatic Inc. and NAPCO.