Metal finishing plants

U.S. PSES for All Metal Finishing Plants Except Job Shops and Independent Printed Circuit Board Manufacturers... 

The Maipo River in central Chile runs past a metal finishing plant in the town of Puente Alto, where 100 kg of carbon tetrachloride (CCI4) are accidentally spilled into the river. Other compounds were also included in the spill, but the environmental health officials are most concerned about the CCI4. They have decided that all water supply plants on the river should be shut down if the concentration of the pulse is greater than 5 ppb. At what time and how far downstream will this occur ... 

Numerous plating and metal finishing plants use chemical oxidation methods to treat their cyanide wastes cyanides and heavy metals are often present together in plating industry waste. Their concentration and their value influence the selection of the treatment process. If the cyanide and heavy metals are not economically recoverable by a method such as ion exchange, the cyanide radical is converted either to the less toxic cyanate or to carbon dioxide and nitrogen by oxidation, while the heavy metals are precipitated and removed as sludge. 

A wide range of polyurethane-type products has become available in recent years for coating applications. These include simple solutions of linear polyurethanes, two-pot alkyd-isocyanate and polyether-isocyanate systems and a variety of prepolymer and adduct systems. The coatings can vary considerably in hardness and flexibility and find use mainly because of their toughness, abrasion resistance and flexibility. Uses include metal finishes in chemical plant, wood finishes for boats and sports equipment, finishes for rubber goods and rain-erosion-resistant coatings for aircraft. One type of coating is potentially competitive with PVC leathercloth. Both alkyd-di-isocyanate and adduct-diisocyanate compositions may be coated on to fabrics from solutions of controlled viscosity and solids content. Such coated fabrics are soft, flexible and, unlike PVC leathercloth, free from plasticisers. 

Table 9.3 displays the ranges of flows in the metal finishing industry. Approximately 81% of the plants have flows between 1.9 and 57 m3/h (67-2000 ft3/h). For those plants with common metals waste streams, the average contribution of these streams to the total wastewater flow within a... 

Chromium levels are elevated in soil, air, water, and biota in the vicinity of electroplating and metal-finishing industries, publicly owned municipal treatment plants, tanneries, oil drilling operations, and cooling towers... 

Recycling and resource recovery includes technologies that either directly use waste from one process as raw material for another process or recover valuable materials from a waste stream before the waste is disposed of. Some of the spent chemical process baths and much of the rinsewater can be reused for other plant processes. Also, process chemicals can be recovered from rinsewaters and sold or returned to the process baths. This section describes some of the recycling and resource recovery technologies available to the metal finishing industry. 

The more thoroughly a metal finisher understands the chemistry of his waste streams, the better able he is to assess their potentials for reuse as raw materials, or in other applications. Successful recycling requires an attitudinal change on the part of management and plant staff, to view their waste streams as resources, rather than as something to be thrown away. 

USEPA. 1982. Control and Treatment Technology for the Metal finishing Industry In-Plant Changes. 

U.S. Army Belvoir Research Development Center (1984), "Pilot Plant Demonstration of a Sulfide Precipitation Process for Metal Finishing Hastewater Treatment."... 

EPA. January 1982. Control and Treatment Technology for the Metal Finishing Industry—In-Plant Changes. Industrial Environmental Research Laboratory, Cincinnati, Ohio. EPA 625/8-82-008. 

Today, Low-Btu Gas (LBG) is expected to be preferred in small demand applications for single users located outside of downtown metropolitan areas. Specific industries in which LBG is expected to be most competitive include primary metals, iron ore beneficia-tion, metal finishing, lime brick refractory, and food industries. Another potential market for Low-Btu Gas is in combined cycle power generation. Cleaned Low-Btu Gas may be particularly advantageous when a plant has many separate combustors which, because of the anticipated new environmental standards, would require either multiple scrubbers or a flue gas collection system. Cleaned Low-Btu Gas is also one of the few options available to a user planning a plant expansion in a non-attainment area. 

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