Recovery of waste water from the fourdrinier section of a papermaking machine takes the water sprays into an initial zone for deceleration and air extraction to be passed into a second zone as a suspension for further air separation

摘要

To carry waste water caught in a spray from the fourdrinier section of a papermaking machine, and extract any air within it, the spray flow of the waste waster (SW) is braked into an initial zone (1) so that the water (SW) forms a closed phase limit layer (3) to air. The majority of the incorporated air is separated and extracted. The resulting suspension (S) flows into a second zone (2) and the suspension (S) vol. flow is registered. The air carried by the waste water (SW) into the first zone (1) is extracted by suction and at least 60% of the air (10) present is separated and extracted in the first zone (1). In the first zone (1), the waste water (SW) is moved into a rotating movement path, and air (10) is extracted from the core of the rotating water. The waste water (SW) is delivered at a tangent within a cylindrical sieve (11), to pass out at least partially in a radial direction through the sieve openings, and is collected at the base of the structure which contains the sieve (11). The rotary movement is developed by a water separator (6), where a suspension (S) is collected at the base to be transferred to the second zone (2) by a channel immersed in the gutter (12). The second zone (2) is formed by a waste water gutter (12), where the waste water flows in as a suspension (S) to be formed into a rotating flow, with the air (10) extracted by suction from its core. The water level at the water separator (6) is over the waste water gutter (12) to give a water level difference between them of at least 0.8 m. The separate spray flows of fourdrinier waste water (SW) each pass to their individual initial zones (1). Waste water recovered from the papermaking machine which is not in a spray flow (SW',SW) is passed to the second zone (2).