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Sand, bentonite clay and organics recovered as foundry waste from
a green sand mold foundry are reclaimed for reuse in making new
green sand molds and mold cores by a multi-step process involving
both hydraulic and mechanical separation steps.
Given green sand is obtained by a mixing operation that is carried
out for a short period of time. Discarded sand is supplied as supplementary
sand to a sand processing line, so that molding sand can be recycled.
Green sand for a molding is used for facing sand or the pocket sand.
Bentonite-covered sand is made by mixing reproduced sand, new sand,
and discarded sand or any or all of them. The bentonite-covered
sand is added to collected sand to supplement it. Also, the bentonite-covered
sand is mixed with water, and used for facing sand or the pocket
sand.
Sand, bentonite clay and organics recovered as foundry waste from
a green sand mold foundry are reclaimed for reuse in making new
green sand molds and mold cores by a multi-step process involving
both hydraulic and mechanical separation steps.
A process for treating a bentonite having a montmorillonite content
of at least 85% which, when activated with sodium ions dried and
ground, does not swell more than about 2.5-fold when gradually added
to deionised water at room temperature and when crushed dried and
calcined to an LoI of less than 4% at 190.degree. C. absorbs 16
to 22% by weight of water in a controlled environment at 25.degree.
C. and a relative humidity of 40% by weight, which process comprises
the following steps in the following order: i) drying to a moisture
content from 25 to 35% by weight; ii) conditioning by crushing,
mixing and/or extruding; iii) addition of water to form an extrudable
paste having a moisture content of 25 to 40% by weight; iv) extrusion
through a die preferably from 4 to 10 mm in diameter; v) drying
to a moisture content from 10 to 14% by weight; vi) calcining at
120 to 250.degree. C. to an LoI of less than 4% at 190.degree. C.;
and vii) reduction to particles.
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