PURPOSE: To reduce the pressure loss of cyclon, by gradually decreasing the flowing speed of gas and making ease of raw material in gas to be fallen down by inertia.

CONSTITUTION: The cyclon 1 consists of the cylinder 2 and hopper 3 and provides the inlet duct 4 and the outlet duct 5. This inlet duct 4 is tilted down toward inlet in tangential direction, the opening is made larger for the lower side than the upper side, enabling gradual spread toward up and down, and it is connected to the cylinder side over the entire length. The cement raw material 6 goes upward along the flow of kiln exhaust gas 10 and enters the cyclon 1 via the inlet duct 4. Since the flowing speed is gradually decreased at the extension part of the inlet duct 4, the material falls down at the prestage of cyclon inlet with inertia and drops on the hopper 3. On the other hand, since the outlet duct 5 is gradually shrinked upward, the flowing speed of gas is gradually increased and discharged from the outlet duct with contraction.