Sand making apparatus, sand making method, and made sand

1. A sand making apparatus comprising:

a crusher configured to crush crushed materials;

a first sorter configured to sort the crushed materials obtained from the crusher into coarse particles, fine particles, and powders through air sorting by air blowing and screening by sorting with a screen, the first sorter including a first collection port for collecting the fine particles sorted by the first sorter;

a negative pressure collection unit configured to suck and collect at least a portion of the powders sorted by the first sorter;

a second sorter disposed between the first sorter and the negative pressure collection unit, the second sorter configured to sort the powders into coarse powders and fine powders by sucking the powders through negative pressure of the negative pressure collection unit so as to transmit the fine powders in a direction of the negative pressure while allowing the coarse powders to be dropped by gravity, the second sorter including a second collection port for collecting the coarse powders dropped by gravity, and wherein an average particle size for sorting the powders into the coarse powders and the fine powders is 20 μm to 75 μm; and

a recovering passage configured to mix the coarse powders collected by the second collection port of the second sorter and the fine particles collected by the first collection port of the first sorter,

whereby a mixture of the coarse powders and the fine particles is collected through the recovering passage, while the fine powders are discharged in such a manner that the fine powders are sucked and collected by the negative pressure collection unit.

2. A sand making method comprising:

crushing crushed materials by a crusher;

sorting the crushed materials obtained from the crusher into coarse particles, fine particles, and powders through air sorting by air blowing and screening by sorting with a screen, and collecting the fine particles that are sorted;

sucking and collecting the sorted powders by a negative pressure collection unit;

sorting the sucked and collected powders into coarse powders and fine powders by sucking the powders through negative pressure of the negative pressure collection unit so as to transmit the fine powders in a direction of the negative pressure while allowing the coarse powders to be dropped by gravity, and collecting the coarse powders that are dropped by gravity, wherein an average particle size for sorting the powders into the coarse powders and the fine powders is 20 μm to 75 μm; and

mixing the collected coarse powders with the collected fine particles by a recovering passage,

whereby a mixture of the coarse powders and the fine particles is collected through the recovering passage, while the fine powders are discharged in such a manner that the fine powders are sucked and collected by the negative pressure collection unit.

3. A sand making method comprising:

crushing crushed materials by a crusher;

sorting the crushed materials obtained from the crusher into coarse particles, fine particles, and powders through air sorting by air blowing and screening by sorting with a screen, and collecting the fine particles that are sorted;

sucking and collecting the sorted powders by a negative pressure collection unit;

sorting the sucked and collected powders into coarse powders and fine powders by sucking the powders through negative pressure of the negative pressure collection unit so as to transmit the fine powders in a direction of the negative pressure while allowing the coarse powders to be dropped by gravity, and collecting the coarse powders that are dropped by gravity; and

mixing the collected coarse powders with the collected fine particles by a recovering passage,

whereby a mixture of the coarse powders and the fine particles is collected through the recovering passage, while the fine powders are discharged in such a manner that the fine powders are sucked and collected by the negative pressure collection unit, and a made sand is formed, the made sand comprising:

fine particles sorted as having particle sizes in a range of 5 mm to 20 μm, the fine particles being 75 to 85 weight percentages out of a total amount of the crushed materials; and

coarse powders sorted as having particle sizes in a range of 300 μm to 20 μm, the coarse powders being 3 to 15 weight percentages out of the total amount of the crushed materials.