Patent ID: 8522793

Claim:
A flash dryer for drying a particulate material comprising: a gas flow path; air-blowing means for producing a one-way dry gas flow in said gas flow path, the dry gas flow having a given temperature; a feeding section disposed in said gas flow path and capable of feeding a particulate material to be subjected to a drying process into said gas flow path by means of the dry gas flow, the particulate material being transferred along with the dry gas flow and dried in the transferring process; and a separating section located in said gas flow path, downstream from said feeding section, said separating section including a tangential separator which has a horizontal axis for separating the dried particulate material from the dry gas flow and discharging the material from the gas flow path; the flash dryer wherein: said gas flow path includes a drying duct for connecting said feeding section to said tangential separator and allowing the particulate material fed from said feeding section to smoothly flow toward said tangential separator together with the dry gas flow, without staying in the drying duct, wherein in order to minimize fracturing of the particulate material in the drying duct said drying duct includes: a single upstream-side duct portion formed as a substantially straight member which is directly connected to a venturi of said feeding section, the single upstream-side duct portion sloping upwardly at a given elevation angle θ with respect to a horizontal plane, the given elevation angle θ with respect to a horizontal plane being adapted to generate a sharp rise in the dry gas flow; and a single downstream-side duct portion formed with a curved-shape having a uniform radius from one end of the curve to the other, the single downstream-side duct portion having an upstream end directly and smoothly connected to a downstream end of said upstream-side duct portion which extends upwardly at the elevation angle θ, and a downstream end directly and smoothly connected to a horizontally extending inlet at a top portion of a periphery of said tangential separator, wherein a length of the uniform curvature radius ranges from 6 to 20 m, and wherein the horizontally extending inlet of the tangential separator is located in a position at a higher level than a downstream end of the upstream-side duct portion, wherein the single downstream-side duct portion of said drying duct curves in a convex shape so that a curvature from the upstream end of the single downstream-side duct portion to the downstream end thereof is limited to an angle that is substantially equal to the elevation angle θ.