RU2188064C1 - Mixer - Google Patents

Abstract

FIELD: production of multiple component mixtures. SUBSTANCE: mixer has housing widened in direction of component flow and equipped with charging and discharge branch pipes, shafts with blades, and spraying nozzle. Mixer is further provided with three sequentially arranged chambers. High-speed shaft with two spirals of different diameters is mounted in first chamber and low-speed shafts are mounted in second and third chambers. Low-speed shaft mounted in second chamber has conical blades and low-speed shaft mounted in third chamber has single-thread auger with cleaning blade. Rotary trapezium-shaped frame blades mounted on inner surface in lower part of second chamber are equipped with pyramidal channels, whose smaller base are oriented in direction of rotation. Nozzles for supplying liquid and viscous components are positioned in upper part of second chamber, whose lower part is made conical. Mixer of such construction in used in the branches of industry using procedures of mixing bulk components and adding liquid components and allows time for producing ready mixture to be reduced. EFFECT: reduced power consumption, improved homogeneity of resultant mixtures and increased efficiency. 3 dwg

Description

 The invention relates to the production of multicomponent mixtures and can be used in industries that use the mixing of bulk components with the addition of liquid ingredients.

The known design of a twin-shaft feed mixer [ed. St. USSR 919719, MKI ⁴ V 01 F 7/04, decl. 04/22/86, application 4061043 / 31-26, publ. 04/23/89, BI 15, 1989], in which removable sections of spiral tapes are attached to the ends of the fingers using brackets, and each shaft of the mixer is equipped with two spiral tapes of opposite winding, the diameter of one spiral being larger than the diameter of the other spiral.

 The disadvantage of the mixer is significant specific energy consumption, insufficiently uniform distribution of components in the resulting mixture and a significant duration of the mixing process.

Known mixer blade for liquid and / or bulk materials [ed. St. USSR 1473823, MKI ³ B 01 F 7/02, A 23 N 17/00, decl. 03.10.80, application 2989747 / 30-15, publ. 04/15/82, BI 14, 1982], which is made in the form of a set of diverging truncated hollow pyramids, the smaller bases of which are interconnected.

 The disadvantage of the mixer blade is the increased metal consumption, as well as the fact that its design does not provide uniform mixing.

 An object of the invention is to reduce specific energy consumption while achieving the best mixing uniformity due to the implementation of a progressive mixing method based on mechanical fluidization in combination with cross counterflow. Thus, the use of the invention will reduce the time to obtain the finished mixture, and therefore, to reduce the specific energy consumption for mixing with the best uniformity of the resulting mixture. The proposed design of the mixer blade provides uniform mixing.

 The problem is achieved in that in a mixer containing a housing with loading and unloading nozzles, expanding in the direction of movement of the components, shafts with blades, a spray nozzle, new is that it has three cameras in series, in the first of which a high-speed shaft with two spirals of different diameters, and in the second and third chambers a low-speed shaft is installed, equipped with cone-shaped blades in the second chamber, and a single-feed screw with a cleaning blade in the third, on the inner erhnosti bottom of the second chamber mounted rotating frame trapezoidal blade having pyramidal channels, smaller bases of which face in the direction of their rotation, and the top of the second chamber set nozzle for supplying liquid and viscous components, the lower portion of the second chamber has a conical shape.

 In FIG. 1 shows a General view of the mixer, figure 2 is a cross section of a second chamber of the mixer, figure 3 is a General view of a trapezoidal frame blade.

 The mixer (Fig. 1) contains a housing 1 with loading 2 and discharge 14 nozzles located in the housing high-speed 3 and low-speed 4 shafts, each of which has an individual drive (not shown in figure 1).

 The mixer has three successive chambers 7, 8 and 9. In the first chamber 7 there is a high-speed shaft 3 with two twin-helical spirals 5 and 6 of different diameters. A slow shaft 4 passes through the second 8 and third 9 chambers of the chamber 4. It is equipped with cone-shaped blades 10 (FIG. 2) located in the second chamber 8, and a single-auger screw 11 with a cleaning blade 15 in the third chamber 9. The configuration and shape of the blades 10, 12 and 15 is selected taking into account the state of the mixed mass, its volume, layer thickness, productivity, ratio of mixed components, degree of homogeneity, method of loading components and unloading the mixture and technology requirements.

 The lower part of the second chamber 8 has a conical shape, and rotating trapezoidal frame blades 12 are mounted on its inner surface, having pyramidal channels, the smaller bases of which are turned in the direction of their rotation (Fig. 3). They rotate with a large circular frequency and are designed to create a dusty multiphase mixture into which it is convenient to introduce finely dispersed liquid components. Moreover, if the blades rotate about their central axis, then the smaller base of the pyramidal channels located on one side of the axis will be directed to the direction of rotation, and located on the other side of the axis will be directed opposite to the direction of rotation. In the upper part of the second chamber 8, nozzles 13 are installed for supplying liquid and viscous components.

 The proposed mixer operates as follows.

 The initial bulk components are loaded into the mixer through the loading nozzles 2. The drive is turned on and the shafts 3 and 4 are rotated. High-speed shaft 3 with the help of two two-way helical spirals 5 and 6 of different diameters begins to capture and move the bulk components of the resulting mixture. Due to the fact that in the first chamber 7 two two-way helical spirals 5 and 6 of different diameters are formed on the high-speed shaft 3, they provide a direction of flow of the mixture flows towards each other in the direction from the end walls to the center of the mixer. Thus, the direction of movement of the mixture in the first chamber 7 of the mixer has the form of a cross countercurrent.

The analysis shows that mixing conditionally consists of three elementary processes:
- convective mixing is the movement of groups of particles from one volume of a mixture to another by the introduction and sliding of layers;
- diffusion mixing is the gradual movement of particles of various components through the newly formed boundaries of their separation;
- segregation is the concentration of particles similar in shape, mass and size in different places of the mixer.

 If mixing time is divided into three intervals, then in the first convective mixing prevails, in the second - diffusion mixing, in the third - segregation. The first two processes contribute to the uniform distribution of particles in the mixture, the latter prevents this. Therefore, it is advisable to complete the process at the end of the second mixing interval.

 The mixing efficiency is evaluated by such an indicator as the homogeneity of the mixture obtained, and the coefficient of heterogeneity is used for the quantitative assessment. A mixture is considered practically homogeneous in which the content of the components in any volume does not differ from the set content for the entire mixture.

 The mixing efficiency is affected by the density of the starting components, particle size distribution (shape, size, dispersion size distribution for inhomogeneous components) of the particles of the mixture components, moisture of the components, surface state of the particles, friction and adhesion of particle surfaces, etc.

где σ_c - среднее квадратичное отклонение содержания основного компонента, %; с_cp - средняя массовая доля основного компонента в смеси, %; с_i - массовая доля основного компонента в i-пробе, %; n - число проб.To determine the degree of homogeneity of the resulting mixture, the coefficient of heterogeneity of the mixture k _c (%) is used, which is the ratio of the content of the main component to its average mass fraction of the mixture

where σ _c is the standard deviation of the content of the main component,%; with _cp is the average mass fraction of the main component in the mixture,%; с _i - mass fraction of the main component in the i-sample,%; n is the number of samples.

The smaller k _c , the more uniform the mixture, which characterizes the efficiency of the mixers, with k _c <10% the efficiency of the mixture is considered good.

 With a large difference in the density and particle size distribution of the components, the achievement of the required degree of mixing is difficult and requires considerable time.

 Then the mixture of bulk components is sequentially moved to the second chamber 8 of the mixer, in which it is captured by rotating cone-shaped blades 10 located on a low-speed shaft 4. At the same time, the drive is turned on and the trapezoidal frame blades 12 are brought into rotation, having pyramidal channels.

 If necessary, liquid and viscous components are supplied from the spray nozzles 13 located in the upper part of the second chamber 8.

The movement of the mixture in the second chamber 8 of the mixer is even more complex. It can be conditionally divided into three types:
- the first is the movement and mixing of the mixture by means of rotating cone-shaped blades 10;
- the second is a circular movement with the help of rotating trapezoidal frame blades 12, which have hollow pyramidal channels, the smaller bases of which are turned in the direction of their rotation (figure 3);
- third - irrigation of the resulting dust-like mixture with liquid and viscous components from nozzles 13 located in the upper part of the second chamber 8.

 It is possible to control the intensity of movement of the material in the mixer by changing the angle of rotation of the cone-shaped blades 10 in a plane perpendicular to the axis of the shaft 4.

 Then the mixture enters the third chamber 9 of the mixer, in which, using a single-auger screw 11 with a cleaning blade 15, it is additionally mixed and discharged from the mixer through the discharge pipe 14.

Thus, the use of the invention will allow:
- to optimize the process of mixing different in particle size distribution and physico-mechanical properties of the feedstock by maintaining the rational nature of the movement in each of the three working chambers, depending on their functional purpose;
- expand the scope due to the achieved universalization of the mixing mechanism, taking into account the characteristics of the physico-mechanical properties of the starting components;
- to obtain homogeneous multicomponent mixtures of high quality due to the solution of the problem of uniform introduction of liquid and viscous components into the mixture of bulk materials.

 The application of the proposed design of the three mixing chambers 7, 8 and 9, as well as the original design of the rotating trapezoidal frame blades 12 will also increase the heterogeneity of the resulting mixture and thereby improve the quality of multicomponent mixtures.

Claims (1)

 A mixer comprising a housing with loading and unloading nozzles, expanding along the components, shafts with blades, a spray nozzle, characterized in that it has three chambers in series, in the first of which there is a high-speed shaft with two spirals of different diameters, and in the second and a low-speed shaft is installed in the third chambers, equipped with cone-shaped blades in the second chamber and a single-auger screw with a cleaning blade in the third, mounted on the inner surface of the lower part of the second chamber These are rotating trapezoidal frame blades having pyramidal channels, the smaller bases of which are turned in the direction of their rotation, and nozzles for supplying liquid and viscous components are installed in the upper part of the second chamber, while the lower part of the second chamber has a conical shape.

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