| 摘要 |
Coal mine waste is utilized by separating it into a coal-rich fraction and a coal poor fraction by crushing the material, suspending it in water, and passing it through a hydrocyclone under controlled conditions of grain size and density of suspension. According to the invention the density of the suspension is adjusted, by the addition of water, to 1.22-1.45 kg. per litre and the grain size of the material is not greater than 20 mm. Also, according to the invention, at least 40% by weight has a grain size not greater than 1 mm. and the distribution of grain size under 1 mm. is: 10-30%, 0-0.05 mm.; 20-40%, 0.05-0.5 mm.; 30-70%, 0.5-1 mm. A suitable excess pressure for the hydrocyclone is 0.5 atmosphere. Crushing to a grain size of 20 mm. follows preliminary screening to separate a grain size not greater than 80 mm. If crushing to an overall grain size of 20 mm. does not yield the required percentage of grain size under 1 mm. a return and refeeding process may be employed; or material of this grain size may be added, obtainable from the coal poor fraction, or from the crushing of pieces in excess of 80 mm. grain size. The fraction having a grain size under 1 mm. may also be used as an additive in the manufacture of cement. The coal poor fraction may be further divided, by screening, into fractions of grain size less, and greater, than 2 mm. The finer can be used as an additive to raw clay in the manufacture of bricks. The coarser can be used for mine-filling operations; also as an additive for low-density concrete. Detailed examples are given. Specification 913,178 is referred to. |
