RU2177362C2 - Centrifugal mixer - Google Patents

Abstract

FIELD: continuous preparation of mixtures of loose materials; food-processing, chemical and other industries. SUBSTANCE: centrifugal mixer has vertical cylindrical housing, drive shaft with rotor made in form of disk which is secured on this shafts; besides that, it is provided with hollow truncated thin-walled cones mounted concentrically on it; height and angle of inclination relative to generatrix to base increase from central part to periphery. For smooth distribution of flow of material in all cones, one row of ports with baffle plates is added to available row of ports. Reflectors have torus surfaces for forming the return recirculation. Reflectors have torus surfaces fro forming the return recirculation loop. EFFECT: intensification of mixing process; improved quality of mixture. 2 cl, 3 dwg

Description

 The invention relates to devices for the continuous preparation of mixtures of bulk materials and can be used in food, chemical and other industries.

 A known mixer [1], comprising a housing with a rotor placed in it on a vertical shaft, made in the form of concentric truncated cones with working surfaces and a base, while the height and angle of inclination of their generatrix to the base of the rotor increase from the central part to the periphery. Mixing in the specified mixer occurs as a result of the sequential passage of material on the surfaces of three cones under the action of centrifugal forces. However, insufficient discharge flows and lack of recirculation do not allow to obtain high-quality mixtures.

 A known mixer [2], containing three cones, in which the height and angle of inclination of the generators to the base increases from the central part to the periphery, while on the surfaces of the inner and middle cones there are windows through which part of the material moving along the inner conical surface, ahead of the flow hits the surface of the next cone. In addition, a reflector in the form of a volumetric Archimedes spiral is installed above the cones, which partially returns the material coming down from the cone back.

 In the study of the operation of this mixer revealed its shortcomings. Thus, the bypass windows of the inner and middle cones are arranged in such a way that they are bounded on all sides by a conical surface. Because of this, as was established during the experiment, the flow of material moving from the bottom up at the moment of descent from the bottom edge of the window has a velocity that is tangential to the surface of the cone. This leads to the fact that part of the flow of material descended from the edge of the window, again falls on the surface of the cone above the window. At the same time, for rotation frequencies differing by 20-30% (within acceptable values), the overflow coefficient equal to the percentage of the amount of material passed through the windows to the total amount of material fed to the cone differs by 1.5-2 times. Also, the overflow coefficient is not the same for materials with different properties. In addition, it should be noted that the descent of the material from the surface of the reflector does not occur in a circle, but in a spiral line, which leads to an uneven distribution of the material on the surface of each cone. In addition, the lower parts of the surfaces of the middle and outer cones are not involved in the mixing process.

 The purpose of the invention is the intensification of the mixing process, increasing the smoothing ability of the mixer and, as a result, improving the quality of the mixture. Achieving this goal is due to the presence on the surfaces of the inner and middle cones of two rows of windows: lower and upper. At the same time, the lower row of windows facilitates the distribution of the input flow over all cones at once, and the upper row of windows with visors installed above them ensures a stable flow of material from the inner cone to the middle and from medium to external. Also, the goal is achieved due to the presence of reflectors above the inner and middle cones having a torus surface, which ensure the return of material coming off the top edge of the cone back to its base, i.e. reverse recirculation.

 In FIG. 1 shows a general view of a continuous centrifugal mixer; in FIG. 2 shows a diagram of the distribution of the input stream over the surface of the disk, along the cones; in FIG. Figure 3 shows the basic construction of the inner and middle cones in an axonometric image.

 The mixer consists of the following elements: a vertical cylindrical body 1, in which a receiving and guiding device 2 is conical, a cover 3 with inlet pipes 4, a bottom 5 with a discharge pipe 6, a drive shaft 7, on which the discharge blades 8 and the rotor 9 are mounted. The rotor is a disk with three hollow truncated thin-walled cones 10, 11, 12 concentrically mounted on it, which face down with smaller bases. The height and angle of inclination of the forming cones to their bases increase from the central part to the periphery. On the surfaces of the inner 10 and middle 11 cones there are windows: lower 13 and upper 14. Windows 13 are bounded below by the surface of the rotor disk, and windows 14 are bounded on all sides by a conical surface, with visors 15 mounted above them. Reflectors are located above the inner and middle cones 16 having a torus surface. They are attached to the bottom surface of the receiving and guiding device. The drive shaft 7 is mounted in the bearing units 17 and 18 and is driven into rotation by a V-belt drive 19 from the engine 20.

 The operation of the centrifugal mixer is as follows.

 Bulk components are dispensed by the dispensers through the loading nozzles 4 and fall on the surface of the receiving and guiding device 2. Sliding along it, they are evenly poured onto the rotor disk through the annular gap between the device outlet and the drive shaft 7. Under the action of inertia forces, material particles spread over the disk surface while the flow path relative to the disk (as well as the cones) is twisted in the direction opposite to the direction of rotation (Fig. 2). Due to the fact that the windows 13 are bounded from below by the surface of the disk, only part of the flow passes to the surface of the inner cone 10, and the other (60-70%) moves through the windows to the middle cone 11. The material stream that reaches it is again divided into two parts. One of them (30-40%) passes through the windows 13, located in the same way as on the inside, and moves on, and the other goes to the surface of the middle cone (Fig. 2). Since the windows 13 below are limited by the surface of the disk, it is possible to achieve almost constant throughput. Therefore, the overflow coefficient practically does not depend on the rotor speed and on the physico-mechanical characteristics of the materials. The part of the input stream that has passed to the surface of the inner cone moves along it from the bottom up, with the mixing of the components. Due to the presence on the surface of the inner cone of the upper windows 14, part of the material passes through them to the surface of the middle cone 11. Due to the presence of visors 15 over the windows 14, the material flow coming from the lower edge of the window almost completely passes to the surface of the next cone. Thus, the throughput of the upper windows 14 is also practically independent of the rotor speed and material properties. The part of the stream that has not passed through the windows is discharged from the surface of the cone and the reflector 16 returns to its lower base, thereby achieving reverse recirculation of the mixture.

 On the middle cone 11, the same thing happens as on the inner 10. The mixture that fell on the continuous outer cone 12 from the middle, moving along it from the bottom up, is discharged towards the wall of the body and then is poured on the bottom of the mixer. From the mixer, the mixture is unloaded by discharge blades 8 through the nozzle 6. The mixer will work in the optimal mode if 60-70% of the input flow passes through the lower windows 13 of the inner cone 10, and 30-40% of the material amount through the corresponding windows of the middle cone 11 rolling over to it from the rotor disk. For this, it is necessary that the ratio of the width of the windows 13 to the width of the jumpers between them be in the range of 1.8-2.0 for the inner cone and 0.3-0.4 for the average. The relative width of the upper windows 14 of the inner and middle cones will determine the value of the coefficient of reverse recirculation on them, the value of which is not advisable to take more than 20%. Therefore, the ratio of the width of the upper windows 14 to the width of the jumpers between them for the inner and middle cones should be in the range of 0.9-1.1. The number of lower windows 13 on the inner and middle cones should be 3 or 4, and the upper windows 14, respectively, 6 or 8. The height of the windows should be 30-40% of their width.

 So, we can say that the intensification of the mixing process is achieved by redistributing the input stream over three cones. Good smoothing of fluctuations in the input flows is achieved due to the redistribution of the input stream over the three cones and the use of direct and reverse recirculation. This, as well as the use of the entire surface of each cone and the movement of material flows in rarefied layers, improves the quality of mixing the components.

Sources of literature
1. A.S. SU 1546120, A1, 1971, B 01 F 7/26.

 2. A.S. RU 2132725, C1, 1999, B 01 F 7/26.

Claims (2)

 1. A centrifugal mixer of bulk materials containing a vertical cylindrical body, loading and unloading nozzles, a receiving and guiding device, a reflector, a drive shaft with a rotor mounted on it in the form of a disk, with hollow, truncated truncated thin-walled cones with height and angle mounted on it the inclination of the generatrix to the base increases from the central part to the periphery, while windows are made on the surfaces of the inner and middle cones, characterized in that in the lower part of the inner and dnego cones made even one row of windows, the lower bounds of the rotor disc surface, and above the upper windows mounted visors.  2. The mixer according to claim 1, characterized in that it is equipped with an additional reflector, while the reflectors have a torus surface.

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