Abstract:
The invention refers to a device for distributing suspensions, particularly pulp suspensions, in a tank 1, particularly a bleaching tower. It is characterized by a disc 6 being provided near the base 3 of the tank with at least one opening 7 so that the suspension is fed to the tank 1 and distributed in cycles over the tank cross-section near its base 3.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is the national phase of International Application No. PCT/EP97/02996 filed Jun. 9, 1997. 
     BACKGROUND OF THE INVENTION 
     The invention refers to a device for distributing suspensions, particularly pulp suspensions, in a tank, particularly a bleach tower. 
     In order to prevent the pulp from caking on the walls of a tank, particularly a bleach tower, the suspension must be distributed over the cross-section. A device is known, for example, in which a rotating, horizontal tube is provided to distribute the suspension over the cross-section. This design has the considerable disadvantage that the horizontal tube has to be moved through the suspension in the tank, which demands very high drive power. A further design is known from U.S. Pat. No. 4,621,507, where the suspension is distributed by a rotating cylinder which has web plates or paddles in its inner chamber. The common denominator of the devices of the state of the art mentioned above is that practically the entire quantity of suspension is accelerated, which leads to high energy input, i.e. the distribution elements require high drive power. 
     SUMMARY OF THE INVENTION 
     The aim of the invention is thus to create a simple and energy-saving device for distributing the suspension when it is fed into a tank. 
     According to the invention, this is achieved by providing a disc near the base of the tank with at least one opening so that the suspension is fed to the tank and distributed in cycles over the tank cross-section near its base. Since the suspension is fed into the tank in cycles over the cross-section of the tank base, there is no need to accelerate the suspension, particularly in radial direction. 
     An advantageous further development of the invention is characterised by a stationary body, in particular a conical body, being provided in the area above the disc, where stationary web plates are provided between the stationary body and the wall of the tank, which form channels with the stationary body and the tank wall. With this arrangement it is particularly easy to divide the flow and distribute the pulp suspension over a larger circumference. This design prevents the pulp from being intermixed and due to the stationary body, particularly a conical body, it is also prevented from settling. 
     A favourable further development of the invention is characterised by a rotating device, for example paddle blades, being provided underneath the disc to help feed the suspension to the opening. This improves distribution of the suspension on the one hand, and on the other, it prevents the pulp from caking underneath the disc. 
     A particularly favourable configuration of the invention is characterised by the disc rotating, where a chamber which is connected to the suspension feed pipe can be provided underneath the rotating disc. With this configuration, the energy input for distribution is reduced to a minimum because only one disc has to be rotated and because the suspension is distributed in the tank in a simple way, for example from a distribution area located underneath the disc, and through the opening which is now rotating. If there are also a stationary body and web plates available which form channels, the suspension can be distributed in the tank in a favourable way and without high energy input. 
     An alternative configuration of the invention is characterised by the disc having several openings which are connected to an annular channel or a feed chamber for the suspension and which can be closed or opened by means of regulating elements, such as butterfly, slide or disk valves, where the regulating elements clear the openings in a particular sequence, especially in a continuous sequence in the sense of rotation. This configuration not only permits a continuous suspension feed in the sense of rotation, but practically any other feed sequence as well, thus providing even better distribution. Even if one of the actuating drives fails, adequate distribution of the suspension is still guaranteed. 
     An advantageous configuration of the invention is characterised by the base of the tank being formed with twin cones. This design, which is of special advantage when used with regulating elements, permits a particularly favourable tank arrangement without requiring additional built-in elements. 
     The invention is used primarily for feeding pulp suspensions in the medium-consistency range, i.e. between approximately 8 and 15% consistency, however it can also be used in ranges beyond this. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     In the following the invention will be described using examples shown in the drawings, where 
     FIG. 1 shows one configuration of the invention, 
     FIG. 2 illustrates a section through the line II--II in FIG. 1, 
     FIG. 3 shows a further configuration of the invention, 
     FIG. 4 contains a variant of the invention with regulating elements, 
     FIG. 5 shows a further variant of the invention with regulating elements and 
     FIG. 6 contains a variant of the invention with twin cones forming the base of the tank. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a bleach tower 1 in the pulp industry, with the walls 2 in the lower section converging in a truncated cone shape and a base 3. The pulp suspension, preferably in the medium consistency range between approximately 8 and 15%, is fed in through a pipe and a connection piece 4 into a feed chamber 5 which is located above the actual base of the tank 3. The feed chamber 5 is closed off from the inside of the bleach tower 1 with a disc 6. The disc 6 has an opening 7 and is connected to a drive 9 by a shaft 8. The shaft 8 is also secured to walls or scrapers 10 which have holes 11 in order to avoid setting the entire suspension in rotation. 
     Above the disc 6 there is a stationary, conical body 12, which is spherical on the underside. It can, however, take different shapes, e.g. a truncated cone. The bottom section of the stationary body 12 is connected by several web plates 13, which can be straight or curved, to the wall 2 of the tank, such that flow channels are formed between the wall 2 of the tank, the stationary body 12 and the web plates 13. The pulp suspension is now fed in through the connection piece 4 into the feed chamber 5. Due to the rotation of the disc 6, the opening 7 is moved in cycles past each point in the cross-section of the tank so that the suspension exits into the bottom section of the tank, spread evenly over the cross-section. It is then directed upwards through the flow channels formed by the web plates 13. Due to these web plates 13, the suspension is always forced to move upwards and thus, there is practically always an upward flow prevailing and caking on the walls 2 of the tank is avoided. This is further assisted by the fact that the suspension always flows through the opening 7 upwards and thus, is not braked by being deflected. 
     FIG. 2 illustrates a section through the line marked II--II in FIG. 1 and shows the rotating disc 6 with the opening 7 and the shaft 8. Here, the illustration also indicates the walls 10, which prevent caking in the feed chamber 5. Furthermore, as shown in FIG. 2, an additional web plate 14 can be provided to prevent caking in the gap between the disc 6 and the base of the stationary body 12. 
     FIG. 3 shows a variant of the invention which is similar to the variant illustrated in FIG. 1. The difference here is that the pipe 4 in the shape of a quarter bend is mounted on the base 3 of the tank from below. This is a particular advantage with large quantities of suspension. In addition, the scraper 10 only covers a small area of the feed chamber 5 and the bottom section of the stationary body 12 has the shape of a truncated cone. The suspension is fed in here through a circular ring cross-section into the bleach tower 1. 
     FIG. 4 shows a further variant of the invention, where the disc 6 is stationary and has several openings 7. The openings 7 are closed here by disk valves 15 which are adjusted by cylinders 16. Pneumatic cylinders, hydraulic cylinders or servomotors can be used to drive the disc valves 15. The regulating elements here can be controlled such that the valves open one after the other in the direction of rotation. If necessary, the regulating elements can also be controlled in any particular sequence, not necessarily in the order in which they are arranged. As an alternative to lateral feed through the connection piece 4, the suspension can also be fed in through a pipe bend 4&#39; mounted axially. 
     The openings 7 can also be opened and closed by slide 17 or butterfly valves 18, as shown in FIG. 5, with a slide valve 17 on the left and a butterfly valve 18 on the right. 
     FIG. 6 shows a variant of the invention where a bleach tower 1 has a twin-cone base section. At the tank wall 2 which converges in a truncated cone shape, a cone 19 is mounted coaxially and oppositely oriented to form twin overlapping cones so that a ring 20 forms. The annular disc 6 surrounds the cone 19 and constitutes a ring shaped base plate 3&#39;. The suspension is fed in through the connection piece 4 into an annular channel 21. The openings 7 in the circular ring base 3&#39; are closed in cycles using, for example, disk valves 15. 
     The number of revolutions by the rotating disc is approximately 1 to 10 r.p.m., which means a cycle of 1 to 10 times per minute for the other variants.