RU2091150C1 - Mixing apparatus - Google Patents

Abstract

FIELD: mixing viscous liquids or loose materials containing solid inclusions. SUBSTANCE: mixing apparatus includes vessel and cutter-type agitator. Vessel contains balls made from material whose density exceeds density of medium being mixed. Diameter of balls exceeds clearance between agitator and bottom of vessel but is lesser than radius of agitator. EFFECT: enhanced efficient. 2 dwg

Description

 The proposed device relates to the field of chemical engineering and is intended for mixing viscous liquids or bulk materials with large pieces of solid inclusions. The invention can be used in chemical, petrochemical, pharmaceutical, food, cement and other industries. Known apparatuses for mechanically mixing liquids or bulk solids contain vessels in which stirrers of any type are placed. So, for liquids with high viscosity, frame mixers with a low number of revolutions (20-60 r / s) are used. (Strenk F. F. Mixing and apparatuses with stirrers. L. Chemistry, 1975, p.63). The shape of the mixer follows the shape of the bottom of the vessel. Such mixers are ineffective if sufficiently large solid pieces are found in the liquid that are not broken by the mixer, but rotate with it.

 At the same time, situations often arise in the practice of chemical production when the quality of the available raw materials is significantly lower than that required by the technological regulations, i.e. solid fractions are heterogeneous, there are large pieces. To solve such problems, apparatuses with a stirrer in the form of a disk (cutter) located at the bottom of the vessel are known (ibid. P. 66). According to most design features, this device is taken as a prototype. Such an apparatus is used for mixing solid particles with viscous liquids or for crushing solid particles, because Its stirrer provides high shear stresses. However, the efficiency of this apparatus is very small due to the small capture of the volume of mixing of the medium per unit time.

 Also known apparatus for grinding a solid fraction ball mill (Kasatkin A.G. The main processes and apparatuses of chemical technology, M. Chemistry, 1971, S. 736-737). This apparatus is a rotating drum in which a set of balls and milled material are placed. When the drum rotates, the balls, rolling along its inner surface, grind pieces of grinding material. A ball mill, in principle, ensures the grinding of the solid fraction and its mixing with liquid. However, the difficulties of supplying and removing heat of a chemical reaction to a rotating vessel preclude its use as an apparatus in the chemical industry.

 Thus, the task of effectively mixing a viscous liquid with large pieces of solid inclusions in the apparatus of chemical production remains relevant.

 This problem is solved by the proposed apparatus for mixing, which, like the prototype, contains a vessel and a milling mixer. Unlike the prototype, balls of material whose density is higher than the density of the medium being mixed and the diameter of each ball does not exceed the radius of the stirrer disk, but more than the distance between the bottom of the vessel and the stirrer are additionally introduced into the vessel.

 The device is schematically depicted in figure 1. Figure 2 presents the milling mixer, top view. The apparatus is a vessel 1 with an elliptical or conical bottom. At the bottom of the vessel 1, at a distance h from it, there is a mixer 2 in the form of a milling cutter with blades 3. The mixer is connected to the drive 4. Balls 5 are introduced into the container 1 in the amount of 8-10 pieces. The balls should be made of a material whose density is higher than the density of the components being mixed. Naturally, strength requirements are also imposed on the material of the balls. OX18H10T steel is well suited for most mixed media. In the case of aggressive mixed media, when choosing the materials of the balls, their chemical resistance is taken into account. The number of balls depends on the capacity of the device. For each capacity rating, there is an optimal number of balls, determined experimentally. So, for an apparatus with a capacity of 0.15 cubic meters. the optimal number of balls is in the range of 8-10 pieces. With the number of steps less than 8, the mixing and grinding efficiency of the standard milling mixer increased slightly. With the number of balls over 10, no further increase in efficiency was observed, but the motor was overloaded.

 Ball sizes were selected from the following considerations. The diameter of the ball d should be greater than the gap h between the disk 2 of the mixer and the bottom of the vessel 1, so that the balls could not fall into this gap and jam the mixer. On the other hand, the diameter d of the ball must be less than the radius R of the disk of the mixer, otherwise it will not be effectively captured by the blades 3 of the mixer 2.

 The optimal size of the balls in this range, depending on the capacity of the apparatus and the parameters of the mixed medium, is selected using the estimated calculations traditionally used for drum mills (Bilenko L.F. Patterns of grinding in drum mills, M. Nedra, 1984).

The device operates as follows. When the mixer 2 rotates from the drive 4 by the blades 3, the kinetic energy is transmitted to the balls 5. Balls 5 fly from the blades 3 of the mixer 2 to the walls of the vessel 1, breaking and mixing lumps in a viscous medium. After extinguishing the kinetic energy by grinding and mixing, the balls 5, under the action of gravity, sink to the bottom of the container 1. In order for this weaving to occur, the density of the material of the balls must be higher than the density of the moving components, otherwise the balls will be captured in rotation with the medium and will not fall to the bottom of the vessel
Having descended, the balls 5 again touch the blades 3 of the rotating mixer, again they receive a portion of kinetic energy and the process repeats. Thus, intensive mixing and grinding of fractions takes place.

As an example, we give the results of work for a standard milling mixer with the following parameters:
the capacity of the apparatus is 0.15 m3 the bottom is elliptical;
electric motor power 3 kW;
speed 80 rpm;
number of blades 6 pieces, reinforced blades;
balls are made of steel OX18H10T with a diameter of 65 mm;
the number of balls is 8 pieces;
distance from the mixer to the bottom of the vessel 30 mm;
the radius of the stirrer disc is 100 mm.

 Grinding and mixing the copper phthalocyanine pigment in liquid paraffin from a fraction (from 50 to 1) mm to a fraction (from 1 to 0.1) mm was carried out in 20 minutes. A standard device with the same parameters solves this problem in 60-80 minutes.

 Thus, the productivity of a standard apparatus with a milling mixer can be increased by a factor of 3 quite simply and at minimal cost by mixing heterogeneous fractions.

Claims (1)

 An apparatus for mixing, comprising a vessel and a milling mixer, characterized in that balls of material are additionally introduced into the vessel, the density of which exceeds the density of mixing of the medium, and the diameter of the balls exceeds the gap between the mixer and the bottom of the vessel, but is smaller than the radius of the mixer.

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