FI85750B - Method for pumping highly concentrated fibre suspension using centrifugal pump - Google Patents

Description

1 85750

Method for pumping a high-density fiber suspension with a centrifugal pump - Förfarande för pumpning av högkoncent-rerad fiberuspension med centrifugal pump 5 However, a centrifugal pump 10 is not suitable for a thicker mass, because the pump becomes clogged due to the mass f 1. Therefore, expensive pumps based on the displacement principle have been used for pumping thick masses (e.g. 8-15%).

The object of the invention is to provide a method by means of which a centrifugal pump can be used for pumping considerably thicker masses than has hitherto been possible.

This object is achieved by the method according to the invention in that the fiber suspension flowing in the suction line in front of the impeller blades of the pump is fluidized for centrifugal pumping by circulating the fiber suspension and thus subjecting to shear forces by rotating a suction line of non-circular cross-section. sa non-circular rotor.

By the method according to the invention, both circumferential and radial shear forces are generated in the pulp immediately before the pump blades, the force-generated turbulence of which extends over the entire flow range effectively prevents the formation of bonds between the fibers and thus maintains the fluidized state of the pulp. -in fiber suspension behaves hydrodynamically in the same -.35 way as water, whereby the pulp can be pumped by means of a centrifugal pump. To maintain the complete turbulence required for such fluidization, a relative ··· is required. a particularly large amount of energy that increases as the consistency increases.

Known centrifugal pumps with their associated accessories do not use sufficient energy to generate a turbulent flow of 2 85750 to prevent flocculation of the thick mass in the suction duct and immediately before the pump vanes.

For example, a propeller located at the beginning of the intake manifold is inefficient for this purpose because it is relatively short in the flow direction and far from its pump vanes relative to its axial dimension, and does not generate significant radial flow components. In addition to this modest effect of turbulence, the long axial distance between the propeller blades and the rotor blades of the pump causes the fibers to dislocate before they reach the rotor blades, One purpose for operating the propeller has been to mix air 15 into the pulp to make it easier to pump the pulp. Thus, it has been possible to slightly facilitate the pumping of even thicker masses (e.g. 6 - 8%), but it has been practically impossible for them to pump air-free thick masses (8 - 15%).

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Numerous centrifugal pumps are also known, in which co-operating grinding pieces or blades are arranged on the impeller of the pump and on the fixed wall of the flow channel, which come so close to each other as to produce a grinding effect on the fibers. First, the power requirement of grinding in relation to the amount of mass passing through is considerably higher compared to · *. , for pumping only. Second, these refining pumps cannot be used to grind and pump the thick mass, because the fibers of the thick mass upstream of the refining blade are allowed to bind relatively freely, so that the rigid lump formed by flocculation does not advance to the refining blade, which would thus remain empty. these refiner pumps would be attempted:.: 35 to pump a thick mass. The present invention does not relate at all to refining pumps, but to a method by which a centrifugal pump is made to pump the so-called thick cellulose pulp without the risk of clogging due to flocculation V:.

.:. 40 3 85750

The following is an example of a pump structure with which the method according to the invention can be carried out.

Fig. 1 shows an embodiment of the invention in a vertical section and Fig. 2 shows a section of Fig. 1 along the line A-A.

In Figures 1 and 2, reference numeral 1 denotes a pump housing 10 comprising a suction line 2. The housing has, in a manner known per se, a rotatably mounted impeller 3 with vanes 4 and a rear wall 5. The other side of the impeller is open and the inner surface 6 of the pump housing has a wing edge shape. acts as a flow controller.

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A non-circular rotor 11 is arranged in the suction line 2 of the pump, the cross-sectional contour 8 of which is non-circular, which promotes the circulation and fluidization of the fiber suspension in the suction channel 2a.

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In order to implement the method, the mutual arrangement of the parts must simultaneously meet the following requirements: 1. The axial length of the rotor 11 is relatively large compared to the length of the suction channel 2a.

25 2. The rotor 11 must not be longer than its axial length from the front edge of the pump blades 4.

3. The outer edges of the rotor 11 must be at such a considerable distance from the inner wall of the suction channel or its projection that, in all positions of rotation of the rotor, the mass can flow freely in the circumferential direction freely around said outer edges.

*. As shown in Figures 1 and 2, the said requirements ·: · are met.

• * · 4 85750 before the impeller and can be accessed without hindrance by the impeller wing-sol.

In the tests performed, it has been found that the pump according to the invention can easily pump various pulps of the paper and cellulose industry in the consistency range of 8 to 10%. Pumping of even thicker masses is possible. At consistencies below 6%, the pump operates at 2 ... 3 mpp lower inlet pressure than a conventional pulp pump.

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The invention is not limited to the embodiments shown, but numerous modifications may be made therein without departing from the scope of the invention. Thus, for example, the rotor 11 15 fitted to the suction line shown in Figures 5 and 6 may be a circular impeller and / or rotate at a different angular speed relative to the impeller.

• · * · * m

Claims (1)

A method for pumping a high-density fibrous suspension by a centrifugal pump, characterized in that the fibrous suspension flowing in the suction line (8) in front of the blades (4) of the impeller (3) of the pump 5 is fluidized for centrifugal pumping. (8) non-10 circular rotor (11). For pumping of high concentration fiber suspensions 15 with a centrifugal pump, rotating the suspension, to the fiber suspension, the flow and the solids (8) of the fluid (3) or (4) after fluidization of the centrifugal pump and the genome of the fiber suspension The genome is shown in Figure 20 as a single rotor (8) rotor and a rotor (11). # <·