Process for removing ink from wastepaper

Claim 1

A process for removing ink from wastepaper, comprising; introducing an aqueous slurry of wastepaper into a treating vessel; blowing a number of air bubbles into the wastepaper pulp slurry in the treating vessel to cause the air bubbles to absorb ink particles from the wastepaper pulp slurry while rising to the surface of the wastepaper pulp slurry; and removing the resultant ink-absorbed froth from the wastepaper pulp slurry, which process is characterized in that, in said airblowing step, air is blown into the wastepaper pulp slurry through a number of orifices formed on and projecting in the form of short pipes or tubes from a peripheral surface of at least one horizontal cylinder located in a bottom portion of the treating vessel, while the horizontal cylinder is rotated around the horizontal axis thereof to agitate the wastepaper pulp slurry, and the amount of the blown air is controlled to a level satisfying the relationships (I) and (II): G/L≧5.0 (I) and 0.5≦g/A≦2.0 (III) wherein L represents the volume in m 3 of the wastepaper pulp slurry in the treating vessel and G represents the total volume in Nm 3 of the air bubbles blown into the wastepaper pulp slurry, g represents a blowing rate of air in Nm 3 /min and A represents a horizontal cross-sectional area of the treating vessel in m 2 .