PURPOSE: To obtain refined coal low in ash content by a simple apparatus, by supplying coal after flotation to a sedimentation tank provided with a barrier plate for promoting the sedimentation of coal particles and treating the same in a liquid adjusted to predetermined pH.
CONSTITUTION: A slurry containing a mixture of refined coal, obtained after residual coal is removed in an removing tank, and water is sent to a sedimentation tank 4 through a pipeline 3. A pH controller B composed of an acid such as sulfuric acid or alkali such as sodium hydroxide is added to the slurry in the sedimentation tank 4 through a pipeline 7 so as to adjust pH of the slurry to 7W11. The refined coat sedimented in the sedimentation tank 4 provided with a barrier plate is taken out of the tank 4 through a pipeline 8 and further dehydrated if necessary using a centrifugal separator 9. The suspension containing a large amount of ash particles in the sedimentation tank 4 is again returned to the de-ashing 2 from a pipeline 10 or sent to a sedimentation tank 6 to be discarded along with residual coal.
TAKEZAKI HIROSHI
OTANI YOSHINORI
SHOJI KAZUMICHI
