RU2388528C2 - Device to produce homogeneous systems in turbulent flow - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to apparatuses intended for mixing inhomogeneous media and can be used in chemical, construction, light, food and other industries. Proposed device comprises vertical housing with mixer, concrete-sand mix feed branch pipe with tight cover, water and air feed branch pipe and discharge branch pipe. Concrete-sand mix feed branch pipe with diametre d₁ is arranged at angle α and varies in optimum range α=35°-50°. Flexible mixing elements are fitted on shaft with variable pitch between them. Pitch t₁ of the first pair of mixing elements equals t₁=N×(D/s), where D is diametre of flexible mixing elements, s is thickness of said elements, N is correction factor with its magnitude varying from 7 to 10. Pitch t₂ of the second pair of mixing elements makes t₂=N×(D/s)+Δ₁, where Δ₁=2N. Pitch t₃ of the third pair of mixing elements makes t₃=N×(D/s)+Δ₂, where Δ₂=3N. Pitch t_n of the last pair of mixing elements makes t_n=N×(D/s)+ Δ_n, where Δ_n=n×N, where n - amount of pairs of disks.

EFFECT: higher efficiency of producing inhomogeneous gas-filled systems.

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Description

The invention relates to apparatus for mixing liquid inhomogeneous media, can be used in chemical, construction, light, food and other industries.

The closest technical solution to the claimed object is a device for producing homogeneous systems according to SU No. 1749050 A2, publ. 07/23/1992, containing a vertical housing with a mixing device and a sealed cover, a pipe for supplying cement-sand mixture, located at an angle to the axis of the body, pipes for supplying water and air, a drain pipe.

A disadvantage of the known device is the relatively low productivity of mixing gas-filled, homogeneous and inhomogeneous media, for example, foam concrete type, due to the fact that at high rotor speeds a hydraulic shock occurs in the system, which leads to a loss of productivity. The main brake on the optimization of the foaming process in the mixer is the process of converting the solution into foam concrete and changing its hydrodynamic properties as they transform.

EFFECT: increased productivity of obtaining heterogeneous gas-filled, homogeneous systems, for example, foam concrete type, by using elastic-elastic elements of a rapidly rotating mixer and the formation of an optimal cellular structure of a foam concrete stone.

This is achieved by the fact that in a device comprising a vertical housing with a mixing device and an airtight cover, a pipe for supplying cement-sand mixture, pipes for supplying water and air, a drain pipe, and the pipe for supplying cement-sand mixture with a diameter of d ₁ is located at an angle "Α" to the axis of the housing, according to the invention, the angle "α" lies in the optimal range of values: α = 35 ° ... 50 °, and the elastic mixing elements are located on the shaft with a variable pitch relative to each other, and the step t _{1 of the} location of the first pair of elastic of mixing elements is equal to t ₁ = N × (D / s), where D is the diameter of the elastic mixing elements, s is the thickness of the elastic mixing elements, N is the correction coefficient, the value of which lies in the range 7 ... 10, the step t _{2 of the} location of the second pair mixing disks is equal to t ₂ = N × (D / s) + Δ ₁ , where Δ ₁ = 2N, the step t _{3 of the} location of the third pair of mixing disks is t ₃ = N × (D / s) + Δ ₂ , where Δ ₂ = 3N, and the step t _{n of the} location of the last pair of mixing disks is t _n = N × (D / s) + Δ _n , where Δ _n = n × N, where n is the number of pairs of disks.

Figure 1 shows a diagram of a device for producing homogeneous systems in a turbulent mode, figure 2, 3 - arrangement of elastic altering elements under different modes of mixing.

The device comprises a vertical housing 1, for example, in the form of a hollow cylinder with a hermetically sealed cover 2 located in the upper part and bottoms 3 in the lower part. On the side surface of the housing 1, under the cover 2, a pipe 4 with a diameter of d ₂ is located perpendicular to the axis of the housing water supply, and on the opposite side, at an angle "α" to the axis of the housing, there is a pipe 6 with a diameter of d ₁ with a sealed cover 13 to fill the device with a cement-sand mixture. On the inner side surface of the housing 1 are placed elastic blades 14. In addition, on the cover 2 there is a fitting 5 with a diameter of d ₃ for supplying compressed air under a pressure reaching 3 ... 16 atm. To work under high pressure, all the joints at the nozzles and other nodes interacting with the housing 1 are sealed. A drain pipe 7 of diameter d is located coaxially with the housing 1 in the bottom 3, the shape of which can be made in the form of a surface of at least a second order, for example spherical.

The device is equipped with a turbulent mixer with a rapidly rotating mixing device, which consists of a shaft 8 coaxially located with the housing 1, receiving rotation from an electric motor 9, mounted on the cover 2 coaxially to the housing 1 and connected to it by a coupling 10 through a bearing assembly. On the shaft 8 coaxially, with a variable pitch t relative to each other, there are mixing disks 11 with elastic mixing elements 12 of thickness s and diameter D. The elastic mixing elements 12 can be made in the form of an elastic metal brush, elastic metal rods located at least , in one row, as well as in the form of elastic disks, which are elastic petals located concentrically relative to the axis of the shaft 8. As the material of the elastic mixing elements 12 can be used: polyurethane foam ethane, rubberized elastic elements, composite elastic materials, etc.

Obtaining homogeneous systems, such as foam concrete, in a turbulent flow is as follows.

The resulting foam concrete has unique technical properties, such as low thermal conductivity, high sound absorption, low heat capacity, in addition, it is vapor-permeable, radio-transparent, refractory, environmentally friendly. The properties of foam concrete listed above are due to its internal homogeneous cellular structure, with each air cavity being hermetically separated from neighboring cells by partitions that make up the supporting frame of the foam concrete stone, determine its mechanical and thermophysical properties. The proposed device allows to solve the problem of forming the correct (optimal) cellular structure of foam concrete stone. For example, if we compare two materials with the same bulk density, but ten spheres of different diameters will be formed per cubic centimeter in one foam-stone, and one hundred spheres of the same diameter in the other, we will get the compressive strength of the latter ten times higher than the previous one, those. it is necessary to form stable regular spheres in foam concrete stone of the smallest possible diameter, and their volume in each cubic centimeter of the total volume to regulate the bulk density and strength of the building material. The cavitation principle of producing foam concrete is possible at high speeds of rotation of the shaft 8 of the turbulent mixer, which causes turbulent flows and fluid fluctuations.

Upon receipt of homogeneous systems, including foam concrete, the principle of changing the geometry of a rapidly rotating turbulent mixer depending on the medium and shaft rotation speed 8. The so-called "elastic blades" are used, which are elastic mixing elements 12 of thickness s and diameter D. Their functional purpose and the main work consists in damping a hydrodynamic shock and changing the linear velocity of the end of the working surface of the elastic mixing elements 12 at a constant angular shaft rotation speeds 8. At the same time, turbulence and fluctuation processes develop to increase the dynamic pressure aimed at homogenizing the mixture with the subsequent transition to the active phase of cavitation. At the time when the hydrodynamic medium exerts maximum resistance, the linear velocity of the ends of the elastic mixing elements 12 is minimal, but the maximum power on the shaft allows the development of turbulent flows in the mixture.

As the substance is homogenized in a turbulent mixer, the hydrodynamic resistance of the medium decreases and the linear velocity of the working surface of the elastic mixing elements 12 increases, creating conditions for the maximum development of cavitation processes, i.e. a system of interactions is implemented, the main working tool of which is the mixture itself, the particles of which interact with each other.

A turbulent mixer with elastic mixing elements 12 acts as the master generator of the process, which is required for the preparation of a homogeneous mixture with desired characteristics. The rotating mixture interacts with the inner surface of the housing 1, on which the blades 14 are located, capable of changing the angle of attack and the area of resistance, trying to direct the flow in a given direction. Depending on the tasks to be solved, the blades 14 can be rigid, flexible, as well as with a fixed and variable angle of attack (not shown). For torsion damping of the shaft 8, the transmission to the engine 9 is carried out through an elastic coupling 10. This reduces the load on the drive and significantly extends its life. All systems are designed to operate at an internal pressure in a turbulent mixer and a flexible pipe up to 16 atm. Liquids do not compress and transfer pressure to everything that is in them, while the effect on the mixture being prepared is carried out at the molecular level, which is almost impossible in other types of mixers. The cavitation process under pressure saturates the mixture with air, which at the pouring site, freed from excess pressure, turns into bubbles that are evenly distributed throughout the mass of the mixture.

In a turbulent mixer it is possible to create a high degree of rarefaction and produce on it not only foam concrete, foam gypsum, but also a whole gamut of materials, including paints, refractories, self-leveling floors, hard putties, etc.

Filling with monolithic foam concrete significantly increases the bearing capacity of the metal frame, its resistance to longitudinal and transverse bending and torsion. Moreover, the joint work of metal structures and foam concrete is related to fire safety, as metal insulated with foam concrete does not lose its bearing capacity, whereas in the event of a fire, even reinforced concrete slabs and ceilings from high temperature curl up like burning paper.

Currently, the applicant has manufactured a cavitation-type turbulent mixer with a productivity of 15 ... 30 m ³ per shift, on which experimental foam concrete samples with a bulk density of 360 kg / m ³ and compressive strength were obtained: with smaller air bubbles - 0.71 MPa; with larger air bubbles of 0.1 MPa. The experimental filling of the under-roof space with foam concrete with a density of 360 kg / m ³ , strength of 0.71 MPa and thermal conductivity of 0.08 W / m · K was successfully carried out.

For the optimal operating mode of the device for producing homogeneous systems in a turbulent flow, the parameters of its structural elements are made in the following ratios.

The ratio of the diameter d _{3 of the} nozzle for supplying compressed air to the diameter d _{2 of the} nozzle for supplying water with a foaming agent lies in the optimal range of values: d ₃ / d ₂ = 0.9 ... 2.7, the ratio of the diameter d _{1 of the} nozzle for supplying cement-sand mixture to the diameter D of the elastic mixing elements 12 lies in the optimal range of values: d ₁ / D = 0.20 ... 0.25, the ratio of the diameter d of the drain pipe to the diameter D of the elastic mixing elements 12 lies in the optimal range of values: d / D = 0 05 ... 0.25.

A pipe for supplying a cement-sand mixture with a diameter of d ₁ is located at an angle “α” to the axis of the housing 1, which lies in the optimal range of α = 35 ° ... 50 °.

The elastic mixing elements 12 are located on the shaft 8 with a variable pitch relative to each other, and the step t _{1 of the} location of the first pair of elastic mixing elements 12 is t ₁ = N × (D / s), where D is the diameter of the elastic mixing elements 12, s is the thickness elastic mixing elements 12, N is a correction coefficient, the value of which lies in the range 7 ... 10, step t ₂ , the location of the second pair of mixing disks is t ₂ = N × (D / s) + Δ ₁ , where Δ ₁ = 2 N, step ₃ t arrangement of the third pair of mixing disk ₃ is t = N × (D / s) + Δ _2, where Δ 3 ₂ = N, and step t _n at location Lednov pair of kneading disks is _{t n = N × (D /} s) + Δ n, where Δ _n = _n × _N, where n - the number of pairs of discs.

A cement-sand mixture is poured into the housing 1 through the pipe 6 with the sealed lid 13 open, and water with the foaming agent is supplied through the pipe 4. When the motor 9 is turned on, the shaft 8 rotates with elastic mixing elements 12 and the cement-sand mixture is prepared. The air supply to the housing 1 is carried out by a compressor (not shown) through the pipe 5 under a pressure of 5 ... 6 atm. With a further rotation of the shaft 8 with elastic mixing elements 12, the cement-sand mixture is enriched with air and foam concrete is formed. The blades 14 on the inner surface of the housing 1 allow, together with the rotation of the shaft 8 and the elastic mixing elements 12, to achieve the preparation of a more uniform foam concrete mixture.

The initial mixture has a high density. This circumstance prevents, in the case of mixing elements being rigid, the operation of the mixing device at high speeds with the development of turbulent flows and, as a result, the production of a homogeneous homogeneous foam concrete mixture of a cellular structure. And in the proposed device, the implementation of the elastic mixing elements eliminates this drawback due to the fact that they work in various modes, from completely straightened with a diameter D ₂ (see figure 2) to folded into a smaller diameter D ₃ (see figure 3) . In this case, the self-tuning of the parameters of the elastic mixing elements under the physicomechanical properties of the mixture at the current time of the preparation of the foam concrete mixture occurs. When straightening the mixing elements, speeds develop that contribute to the turbulization of the flows of the homogeneous mixture. In the case where the mixture is denser, the elastic mixing elements bend towards the axis of the shaft, and in the case of a less dense mixture, they straighten and develop higher linear speeds, for example, when the shaft rotates at 3000 rpm and the initial diameter D _{2 of the} mixing element of 400 mm, have the following ratio of linear velocities: V _{1 2} = wD / 2 = (3000/60) × (0,4 / 2) = 10 m / s; V ₂ = wD _3/2 = (3000/60) × (0,2 / 2) = 5 m / c.

Claims (1)

A device for producing homogeneous systems in a turbulent flow, comprising a vertical casing with a mixing device, a sealed cover located at an angle “α” to the casing axis of a pipe with a diameter of d ₁ for supplying a cement-sand mixture, a pipe for supplying water and air, and a drain pipe, characterized in that the angle «α» lies in an optimum range of values: α = 35 ° ... 50 °, and the elastic elements are arranged on the agitating shaft of the variable pitch relative to each other, wherein the arrangement pitch t ₁ of the first pair of elastic agitating lementov equal to t ₁ = N · (D / s) ,
where D is the diameter of the elastic mixing elements;
s is the thickness of the elastic mixing elements;
N - correction factor, the value of which lies in the range 7 ... 10, step t ₂ location of the second pair of mixing disks is
t ₂ = N · (D / s) + Δ ₁ ,
where Δ ₁ = 2N,
the step t _{3 of the} location of the third pair of mixing disks is t ₃ = N · (D / s) + Δ ₂ , where Δ ₂ = 3N,
and the step t _{n of the} location of the last pair of mixing disks is equal to t _n = N · (D / s) + Δ _n ,
where Δ _n = n · N, where n is the number of pairs of disks.

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