| 摘要 |
<p>To separate foreign particles from the paper fibers in a suspension, by flotation, the flotation action starts with an upwards flow into the flotation vessel (1). The dividing walls (6,6',6) in the vessel (1) are vertical and are next to each other. The paths of the upwards and downwards flows extend over at least one-half of the height (H1) of the suspension filling the flotation vessel (1). The cleaned suspension (S') is taken from the lower section of the vessel (1). The vertical component of suspension (S,S') flow speed on an upwards direction (3) is 2-12 cm/sec. and 1-7 cm/sec. on a downwards flow direction (2). The vertical component of the suspension flow speed in the final downwards direction (2) is 1-4 cm/sec. The suspension (S) is initially mixed with gas bubbles, and added to the suspension already present in the flotation vessel (1). At least part of the gas (G) for the bubbles is mixed with the suspension at the direction change point from a downwards flow (2) into an upwards movement. The bubbles formed by the gas (G) are significantly larger than the bubbles already present in the suspension. The bubbles in the upwards flow (3) are smaller than those in the downwards flow (2). The height (H1) of the suspension (S) in the vessel (1) is at least equal to the max. horizontal width of the base (8). The flotation vessel (1) is oval or round, and the suspension (S) is fed into the center. The cleaned suspension (S') is led outwards to give a main flow from the radially inner zone radially outwards. The circular movement of the suspension (S) in the peripheral direction of the vessel (1) is at a speed of at least 1 cm/sec. The inlet (9) is at the lower section of the vessel (1), at the center of the base, and the outflow (10) for the cleaned suspension (S') is radially outwards, to lie opposite each other. Part of the dividing walls (6,6',6) is tightly bonded to the base (8) of the flotation vessel (1) and the other part forms a flow passage round it, with the sealed and open parts alternating in the main flow direction. The free end of the dividing wall (6) is below the level of suspension (S) in the vessel (1). The vessel (1) has a vertical side wall (7), and the side wall (7) and dividing walls (6, 6',6) are concentric. The dividing wall (6,6',6) height (H2) over the vessel base (8) is at least twice the max. horizontal width of the vessel (1). The vessel base (8) has connections for the feed of flotation air or a mixture of liquid and air, at the flow passage openings (4) or directly downstream of them.</p> |
