Separating sand with RHEWUM Machines
Processing of casting sand for reuse
Sand is the perfect material to shape liquid metals. The sand is screened, mixed with binding agents and then formed to the dead-mould. This sand core later on shapes the metal. Usually clay is used as binder as well as sorts of sand with a high clay content, the so called foundry sand.
After hardening of the moulded article the sand is removed from the mould and separated from binder and resin as well as undesired finest sand by crushing and screening. Then the sand is formed to sand cores again.
Since the foundry sand must not react with other chemical components only high grade sand can be used which is mainly quartz sand or glass sand. Quartz sand for foundry industry normally has a particle size between 0.1 mm and 0.8 mm.
The binder for the foundry sand have to be chosen regarding to the requirement that the mould should fall to pieces by the heat of the founding process. Nowadays binders are also utilizable for metals with a high fusion point. During the founding process they evaporate, melt out or decompose (polystyrene). Another method is the melting out before casting which is made when using wax and synthetic resin.
Modern separating systems for silica sand
Silica sand mostly consists of silicon dioxide (SiO2). After washing and fine screening silica sand is used in glass industry for the production of flat and round glass and in the foundry industry for mould making. Sand containing less than 0.023% iron is suitable for the production of translucent (white) glass. For this mostly very fine silica sand of a particle size between 0.1 and 0.4 mm and a humidity of less than 5% is used.
Besides this silica sand is used for the production of ceramics and fibre glass, in the chemical industry and in abrasives, as moulding sand as well as nonplastic material resp. filler.
In ceramic industry silica sand as nonplastic material reduces the drying loss but at the same time downgrades the ductility of the ceramics and it becomes brittle. Mostly silica sand is used as very fine sand with a high purity to avoid unwanted discolourings. Fibre glass is used as glass fibre cable for data transmission and for the production of glass fibre reinforced plastics by spinning fine fibres with a defined diameter.