Method and device for mixing suspensions

Abstract

A watery dilution fluid (2), e.g. recycled papermaking water, is mixed with thicker fibrous suspension (1) arising as reject material (12) from suspension preparation. A closed mixer (4) is used. This has no mechanically-driven components to assist mixing. Its mixing tube includes at least two inlets and at least one outlet. The thick suspension (1) feed, flows more slowly into the watery dilution fluid. The latter enters at a velocity which is at least 5 m / s, preferably at least 10 m / s greater than the main flow velocity. After mixing-in the dilution fluid, the flow enters a straight cylindrical pipe section (6) with a length 5 times its diameter. The dilution fluid is fed along the axis of the pipe as a central driving jet, into the flow of thicker suspension. No pump is used to transfer the mixture into the next processing stage, which takes place in closed apparatus. The diluted suspension is fed to a pressurized screen (7, 8) without using a further pump. The thicker fibrous suspension is supplied to a cleaning plant (e.g. cyclones removing heavy contaminants) using a pulp suspension pump (9). It is fed for dilution into the mixing unit and thence to a further cleaning plant. In neither of these cases is a further pump used. An independent claim is included for the corresponding mixing equipment.

Description

technical field

[0001] The present invention relates to a method for mixing suspensions having different components and a mixing device for carrying out the method. Background technique

[0002] Such a method is mainly used to reduce the material concentration of fibrous material suspensions during pulp preparation in paper mills. It is known that such a device adjusts the treated fibrous material suspension to a defined concentration when carrying out most of the process steps, which is very interesting, since the optimum effect of these process steps can basically be achieved by only one process in each case. The determined concentration is reached. In cases where the concentration should be reduced, a diluent, eg return water, is incorporated into a thicker fibrous material suspension. This is usually done in an intermediate pulp tank or by means of a pump into which the ingredients to be mixed are introduced together. When using pulp troughs, it is tolerable to instal...

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