A screening device for separating dry granular material into a fine fraction and a coarse fraction is provided. The screening device includes a drum screen defined by an open rotatable frame, which frame defines a circumferential wall, and a sheet-like screen arranged over the circumferential wall of the frame. The screening device also includes a driving device by means of which the drum screen is rotatably driven, a feed opening at a short end of the drum screen and a discharge opening at the opposite short end of the drum screen. The screening device further includes a vibration device which rotates along with the drum screen, which vibration device includes one or more vibrating elements mounted to the drum screen, which set the drum screen vibrating in use. A method for separating dry granular material into a fine fraction and a coarse fraction is also provided.

A screening device for separating dry granular material into a fine fraction and a coarse fraction is provided. The screening device includes a drum screen defined by an open rotatable frame, which frame defines a circumferential wall, and a sheet-like screen arranged over the circumferential wall of the frame. The screening device also includes a driving device by means of which the drum screen is rotatably driven, a feed opening at a short end of the drum screen and a discharge opening at the opposite short end of the drum screen. The screening device further includes a vibration device which rotates along with the drum screen, which vibration device includes one or more vibrating elements mounted to the drum screen, which set the drum screen vibrating in use. A method for separating dry granular material into a fine fraction and a coarse fraction is also provided.

The present invention relates to a screening device for separating dry granular material into a fine fraction and a coarse fraction. The device comprises a drum screen defined by an open rotatable frame, which frame defines a circumferential wall, and a sheet-like screen arranged over the circumferential wall of the frame, a driving device by means of which the drum screen is rotatably driven, a feed opening at a short end of the drum screen and a discharge opening at the opposite short end of the drum screen. The screening device comprises a vibration device which rotates along with the drum screen, which vibration device comprises one or more vibrating elements mounted to the drum screen, which set the drum screen vibrating in use. The invention further relates to the screening of granular material using such a device.

The present invention relates to a screening device for separating dry granular material into a fine fraction and a coarse fraction. The device comprises a drum screen defined by an open rotatable frame, which frame defines a circumferential wall, and a sheet-like screen arranged over the circumferential wall of the frame, a driving device by means of which the drum screen is rotatably driven, a feed opening at a short end of the drum screen and a discharge opening at the opposite short end of the drum screen. The screening device comprises a vibration device which rotates along with the drum screen, which vibration device comprises one or more vibrating elements mounted to the drum screen, which set the drum screen vibrating in use. The invention further relates to the screening of granular material using such a device.

Provided is a method for producing a polyacrylic acid (salt)-based water absorbent resin in which the physical properties (especially liquid permeability) are improved and maintained even in large scale production. The method for producing a polyacrylic acid (salt)-based water absorbent resin, which sequentially includes a polymerization step, in which a monomer aqueous solution having acrylic acid (salt) as a main component is polymerized, a drying step, in which a water-containing gel-like crosslinked polymer obtained in the polymerization step is dried, and a classification step, in which a polymer obtained in the drying step is classified, wherein a rocking-type sieve classification apparatus is used in the classification step, and the rocking-type sieve classification apparatus has a sieve net having a trajectory and a rotation speed in the following ranges; radial gradient R: from 5 to 40 mm, tangential gradient T: from 0.1 to 25 mm, eccentric gradient E: from 40 to 80 mm, and rotation speed F: from 60 to 600 rpm.

A method for producing a water absorbent resin, the method including a polymerization step, a drying step, a classification step, and a surface crosslinking step. The classification step carried out before or after the surface crosslinking step requires use of a tapping material and a metal sieve mesh, in which the tapping material being heated at 40 C. to 100 C. is installed below the metal sieve mesh, and the metal sieve mesh has an area of 1 to 10 m.sup.2/sheet. The classification step further requires introducing a classification aid particle, which has a specific gravity different from that of the water absorbent resin, to the metal sieve mesh; and monitoring the presence or absence of damage to the metal sieve mesh.

A method for producing a water absorbent resin, the method including a polymerization step, a drying step, a classification step, and a surface crosslinking step. The classification step carried out before or after the surface crosslinking step requires use of a tapping material and a metal sieve mesh, in which the tapping material being heated at 40 C. to 100 C. is installed below the metal sieve mesh, and the metal sieve mesh has an area of 1 to 10 m.sup.2/sheet. The classification step further requires introducing a classification aid particle, which has a specific gravity different from that of the water absorbent resin, to the metal sieve mesh; and monitoring the presence or absence of damage to the metal sieve mesh.