Kason Separator Recovers Brass From Waste Slag
American Brass, Headland, Ala., recycles scrap brass into ingots, which are sold to manufacturers of plumbing fixtures and other hardware.
To make the ingots, the scrap brass is loaded into rotary furnaces and melted down. Borax is added to the molten brass, causing impurities to rise to the surface and form slag that's skimmed off and cooled. The process generates about 40,000 pounds of slag per day.
When slag hardens, it traps small beads of pure brass, valued at approximately $.50 per pound. American Brass wanted to recover this brass by crushing the slag and separating the dust from the larger, brass-Iaden chunks. The company already had the necessary size reduction equipment, but needed a screener. Limited space and housekeeping concerns dictated that the new screener be compact and dust-tight.
Dale Knepp, Vice President and Plant Manager for American Brass thought the Kason VIBROSCREEN might meet the plant's needs, so he called Kason and arranged a screening test. Henry Alamzad, a Kason Test Center engineer, asked Knepp to send two 55-gallon drums (about 300 pounds) of slag to the Test Center. Knepp then arranged to visit the Test Center to witness the screening tests.
When the Test Center received the slag, Alamzad analyzed its angle of repose, bulk density, particle size distribution, and particle shape to prepare for the test session. For the tests, a screw feeder discharged slag into a 24 in. diameter vibrating circular screener fitted with a 20-mesh screen.
Based on his experience with similar materials, Alamzad installed plow blades to catch material that collected along the edge of the screen and direct it through the discharge spout. This prevented oversize material from accumulating on the screen deck. He also installed reverse tie-downs to pull the center of the screen up. This created a sloped screening surface and prevented heavy material from collecting in the middle of the screen.
After the first separation test, Alamzad found that too much dust was being discharged with the overs. To remedy this, he replaced the 20-mesh screen with an 18-mesh screen. Tests also showed that the screener operated more efficiently when a 10-mesh screen was placed above the 18-mesh screen. This reduced the load on the 18-mesh screen and increased the available screening area.
The largest two fractions ( everything bigger than 18 mesh) constituted 30 percent of the slag and contained about 30 percent brass. The fines constituted 70 percent of the slag and contained almost no brass.
"I was very impressed with the way the vibrating circular screener worked," says Knepp. " After seeing the test results, I saw no reason to look any further the screener did exactly. what we needed it to do." In December, American Brass purchased and installed a double-deck, 72 in. vibrating circular screener with 10-mesh and 18-mesh stainless steel screens.
The new screener handles as much as 12,000 pounds of slag per hour, with an average throughput of 40,000 pounds per day. Reducing and screening the slag allows American Brass to recover from 35,000 to 45,000 pounds of brass per month.
Screen Tips - Volume 5, Number 1 Fall 1990