US 5,131,980 A · Hydrocyclone removal of sticky contaminants during paper recycling

Abstract

The removal of sticky contaminants during the production of recycled paper is accomplished utilizing a hydrocyclone froth flotation process. Paper having sticky contaminants from labels, tapes, hot melts, and other tacky substances, is reduced to a finely comminuted liquid solids suspension of about 1-4% consistency. The suspension is introduced into a first end of a vortex in a hydrocyclone, and the air is sparged radially inwardly into the suspension vortex by passing it through a porous inner wall of the hydrocyclone. Ligher weight sticky contaminants move to the center of the hydrocyclone, facilitated by the radially inward movement of the sparging air, and hydrophobic sticky contaminants attach to the air bubbles and form a foam. The foam and lightweight sticky contaminants are removed from the first end of the vortex, while the pulp which has had sticky contaminants removed therefrom is discharged from the second end of the vortex, opposite the first end. A plurality of vertical axis hydrocyclones may be connected together in series, with a plurality of the series connected in parallel, to provide the most effective treatment. Removal of sticky contaminants can be practiced prior to or simultaneously with deinking.

Claims19

Dependent claims

A method of removing sticky contaminants from recycled paper cellulosic pulp containing such contaminants, comprising the steps of continuously:

(a) reducing paper having lightweight and hydrophobic sticky contaminants associated therein to a finely comminuted liquid-solids suspension flow having a solids consistency of about 1-4%;
(b) introducing the suspension into a first end of a vortex;
(c) sparging air radially inwardly into the suspension in the vortex, to cause the lightweight sticky contaminants to move radially, and to cause the hydrophobic sticky contaminants to attach to air bubbles and move toward the fist end of the vortex;
a foam having a solids and liquid content being formed while cellulosic pulp moves to the second end, opposite the first end, of the vortex;
and
(d) removing foam and lightweight sticky contaminants from the first end of the vortex, while pulp with sticky contaminants removed is discharged from the second end of the vortex, using only the vortex and sparged air.

3 more elements

A method of manufacturing recycled paper, comprising the steps of continuously:

reducing cellulosic paper having lightweight and hydrophobic sticky contaminants associated therewith to a finely comminuted liquid-solids suspension flow having a low solids consistency;
screening the suspension to remove reject particles;
subjecting the suspension to froth flotation to produce a pulp;
washing and thickening the pulp;
and making paper from the thickened pulp;
wherein said froth flotation step is practiced with suspension having a solids consistency of over 1.5%, by:
(i) introducing the suspension into a first end of a vortex;
(ii) sparging air radially inwardly into the suspension in the vortex, to cause the lightweight sticky contaminants to move radially upwardly and the hydrophobic sticky contaminants to attach to air bubbles and move toward the first end of the vortex, a foam being formed while cellulosic pulp moves to the second end, opposite the first end, of the vortex;
and
(iii) removing foam and lightweight sticky contaminants from the first end of the vortex, while pulp with sticky contaminants partially or completely removed is discharged from the second end of the vortex.

7 more elements

Dependencies are inferred from the claim text.

Hydrocyclone removal of sticky contaminants during paper recycling

Life of this patent

Hydrocyclone removal of sticky contaminants during paper recycling

Life of this patent

Abstract

Claims19