Particulate material collecting apparatus

A particulate material collecting apparatus comprising:

• a cylindrical member defining therein a spiral flow chamber having a horizontal center axis, said spiral flow chamber having a horizontal length of about 0.8-2.0 times the inner diameter of the spiral flow chamber;
• an inlet duct connected to one end of said cylindrical member tangentially to the inner circumferential surface of the cylindrical member;
• an outlet duct connected to the other end of said cylindrical member and having a cylindrical portion projecting into the spiral flow chamber coaxially therewith, said cylindrical portion projecting a length of about 0.1-0.2 times the inner diameter of the spiral flow chamber and having a diameter of about 0.7-0.8 times the inner diameter of the spiral flow chamber;
• a hollow inverted pyramidical member connected to the lower portion of said cylindrical member including walls converging downwardly;
• a spiral flow guide plate located near the boundary between said cylindrical member and said hollow inverted pyramidical member so as to define two openings, said openings substantially extending along the entire length of the cylindrical member parallel to the horizontal center axis thereof, one of said openings being disposed closer to the inlet duct than the other opening as measured along a spiral line following the configuration of the spiral flow chamber from the inlet duct to the outlet duct so that the openings are respectively located at the upstream and downstream sides of spiral flow of gas in said spiral flow chamber when the gas is first introduced thereinto through the inlet duct;
• and
• a collected material guide plate mounted in the hollow inverted pyramidical member to define a material collecting space communicating with said one opening located at the upstream side of the spiral flow of gas.