Twittern

HighTech

• The length/width ratio of the screening machinein...

• The principle of the 5-deck Stack Sizer^TM from...

• Conventional spraying

• Repulp principle

• Screen surface on the feed end and behind the...

• Repulp screening machine

• Machine of special steel in a sand classifying...

• Combination of HI-G^® Dryer and cyclone screen

• Dewatering of a scoop wheel overflow

• Flow diagram showing fine sand recovery by means...

• Overall view of a fine sand classifying plant

• For comparison: Screen surfaces from Derrick and...

• Pyramid^TM screen surface from Derrick

• Conventional flat screen surface for comparison

• The principle of the compound dry screening...

• Single-deck machine (l.) with split pan (r.)

• Dry screening of sand and iron ore in arid...

• Dry fine screening of iron ore

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Summary: It was interesting to witness the development of wet and dry screening of fine materials in the last few years. Today, screening machines have become established in mineral processing fields, which in the past were the exclusive domain of hydraulic ­classifiers and separators. Screens are used together with cyclones and hydraulic classifiers or to complement them. Fine screens are installed to retrofit existing plants for the im­provement of screening efficiency. The development in the field of screening surfaces has advanced at high speed. Finer and finer screen cloths with higher open areas and longer life are offered on the market. Fine screening, often unrecognized and ridiculed, has become a high-tech process, which has become established more and more in the sand and mineral industries, as the following article will show.

1 General development

Screening of granular materials is as old as mankind. Already early Egyptian drawings show the screening of grain and salt in the dim and distant past. The development of the screening practice is closely connected with the history of technology. At the beginning, the screens with nettings of wood, bamboo or grass were mainly moved by hand. Then industrial screening, as described by Agricola, first developed rapidly to become a basic process in mining during the Middle Ages. The development of the screening machines themselves went hand in hand with a continuous...