Patent DE-102009011981-A1 (DE)
Title: Purifying recycled water occurring during paper/cardboard production, comprises guiding the recycled water to an inlet side of a flat, conical and/or cylindrical sieve, in which the undesirable materials are retained, by a feeding device
Inventor: KOESTER SOEREN
IPC: D21F1/66
Filed: 2009-03-05
Abstract: The method comprises guiding a recycled water (W) to an inlet side of a flat, conical and/or cylindrical sieve (1), in which undesirable materials are retained, by a feeding device (3) during the purified water passes through sieve openings (2) and again discharges from the sieve openings to an outlet side of the sieve, where a relative movement is carried out from time to time between the sieve and parts of the feeding device. The retained materials of the sieve are transported from the feeding device. The purified recycled water is supplied to a head box of a paper- or cardboard machine. The method comprises guiding a recycled water (W) to an inlet side of a flat, conical and/or cylindrical sieve (1), in which the undesirable materials are retained, by a feeding device (3) during the purified water passes through the sieve openings (2) and again discharges from the sieve openings to an outlet side of the sieve, where a relative movement is carried out from time to time between the sieve and parts of the feeding device. The retained materials of the sieve are transported out from the feeding device. The purified recycled water is supplied to a head box of a paper- or cardboard machine, is led into a closed system up to the head box, and is mixed with a highly consistent fiber suspension and then supplied to the head box in the closed system. The recycled water to be purified has a solid content of 0.3-0.6%. The portion of the material separated from the recycled water per hour is 0.01% related to the quantity of the recycled water. The material, whose particle size exceeds to 1.6 mm, is separated from the recycled water. The speed of the relative movement is adjusted to 1-20 m/minutes. The direction of the relative movement is reversed from time to time. A pressure is adjusted at the inlet side of the sieve and is 2 bar higher than at the outlet side. The recycled water is treated in the feeding device or sieve by a turbulence generator, where the turbulence is generated, by which the fiber agglomerates present in the recycled water is dissolved. The turbulence generator is flow channels, each of which has stage diffusers. The recycled water is supplied into the flow channels with an average speed of 2 m/s. A pressure loss in the flow channels is adjusted to 0.5-3 bar. The feeding device is a closed inlet channel, and is fixed. The sieve is movable and fixed. A scraper of the feeding device is movable. The recycled water reaches from the sieve openings into a collecting device (4). A rotating sealing roller is used for sealing between the sieve and the feeding device and between the sieve and the collecting device, and for generating the relative movement. The sieve has a projection protruding at the inlet side. The material of the sieve is transported from the feeding device into a rejection chamber. The material of the sieve in the rejection chamber is removed from the sieve by a back-rinsing device. An independent claim is included for a sieving device for purifying recycled water occurring during paper or cardboard production.