Sierra Aluminum Co., Riverside, CA
Aluminum Hydroxide


Many of the company's processes involve acid cleaning and etching of aluminum. The resulting waste solution is neutralized and precipitated out as aluminum hydroxide. After squeezing out the excess moisture in a filter press, what remains is a filter cake with approximately 70 percent free moisture. Because the filter cake was quite sticky and difficult to handle, continuous drying was sure to be a daunting task. The continuous drying system they needed seemed out of reach - that is, until the company tested a TURBO-DRYER® from Wyssmont Co., Fort Lee, N.J. The 32-shelf rotary tray dryer is fed 70 percent wet filter cake at the top of the dryer and discharges a primarily granular product at uniform product moisture below 10 percent at its discharge. The complete drying system consists of a 12' dia. 18' tall dryer; a filter-cake-breaking feeder; discharge rotary air-lock; external gas-fired heating system; exhaust cyclone and fan; and interconnecting ductwork. Sierra found that Wyssmont was able to provide a drying system that could be efficient in terms of operating costs while meeting the stringent emission requirements of Southern California. The heating system was required to have an ultra-low NOx gas burner (20 ppm maximum NOx emission) with less than 2 million BTU/hr capacity. "The Wyssmont design team was able to meet this requirement by implementing an exhaust recycle loop that increased the efficiency of the system through heat recovery." The result is a drying operation with efficiency in the range of 1,200 to 1,300 BTU per pound of water evaporated.


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