PURPOSE: To assure high dust collecting efficiency, regardless of the whirling up of the caught raw material, and to assure the low pressure loss without reducing the revolution number, through the use of V-shaped cyclon.

CONSTITUTION: The inlet duct 3 and outlet duct 4 are provided in tangential direction at the both ends of the V-shaped bent cylinder 2 of the cyclon 1, and the hopper 5 is located at the lower part of the bent. The cylindrical inlet and outlet 2a, 2b of the bent cylinder are tilted so that the cement raw material can be fallen downward. This part is constituted as the same diameter, gradually expanded from the bent 2c to both ends, or gradually contracted toward the outlet. The cement raw material enters the cyclon 1 via the inlet duct 3 together with the kiln exhaust gas 10, it is caught by the revolving centrifugal force of the gas at the inlet cylinder 2a, dropps to the hopper 5, and further it is caught at the outlet cylinder 2b by the revolving centrifugal force of the gas. In this case, the radius of the revolution of the gas is changed to adjust the dust collecting efficiency.