RU2496605C1 - Method of plasticiser feed and device to this end - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to powder metallurgy, particularly, to continuous production of pelletised plasticised material. It can be used for making articles from inductile powders with poor mouldability. Powder with plasticising agent solution on vacuum filter including perforated grate with taper holes arranged on filtration material, taper hole vertices being directed along solution flow. Powder is filled on said perforated grate to plasticiser solution to be poured thereon. Pelletising is performed by filtration in vacuum unless solution release is terminated. Pelletiser comprises vacuum filter with perforated grate with taper holes arranged on filtration material, taper hole vertices being directed along solution flow, filtration material and vacuum pump.

EFFECT: uniform distribution of pelletiser and reduced consumption thereof.

3 cl, 9 dwg, 4 ex

Description

The technical field to which the invention relates.

The present invention relates to powder metallurgy, in particular to a method for introducing a plasticizer into a powder or a powder mixture of non-plastic materials having poor formability.

The level of technology. A known method of introducing a plasticizer into a powder mixture of components in the form of a solution when mixed, followed by drying [G.A. Libenson et al. / Powder metallurgy processes. Volume II Molding and sintering. M: - MISIS. - 2002. p. 53].

A device for drying and distillation is known, which is a two-tier screw apparatus, with a “jacket”, figure 1 (1 - cylinder distiller, 2 - cylinder mixer, 3 - granulator (wipe), 4 - hollow shaft, 5 - hollow blades, 6 - a shaft with blades, 7 - a nozzle for supplying water, 8 - a nozzle for supplying plasticizer, 9 - a nozzle for discharging steam, 10 - a nozzle for supplying water vapor, 11 - a nozzle for discharging water, 12 a collection of granulate) [G.A. Libenson, B.C. Panov / Equipment for powder metallurgy workshops. M .: Metallurgy. 1983. p. 107, Fig. 64].

The closest technical solution is a method of kneading a powder mixture with a plasticizer in solution and subsequent spray drying [B.C. Panov, A.M. Chuvilin / Technology and properties of sintered hard alloys and products from them. M: - * MISIS *. - 2001. p. 354-355 /].

When sprayed, a drop of pulp in flight is heated by an inert gas. A granule is formed from a drop of pulp. It is known that upon evaporation, the dissolved substance will be concentrated in the solution, i.e. plasticizer. This will lead to the appearance of a plasticizer layer on the surface of the granule, while inside, according to A.V. theory Lykova, part of the solution may remain, Figure 2.

Figure 2 shows the motion of moisture and heat in the surface layer of a capillary-porous body: 13 — slip flow, 14 — Stefan flow, q — heat flow, j — moisture flow [A. Lykov Heat and mass transfer in capillary-porous bodies. M .: Gostekhizdat. 1954. 296 p.].

The disadvantages of the closest technical solution are: the distribution gradient of the plasticizer in the granule volume, the inability to apply it to small-tonnage production, the duration of the process, the high consumption of plasticizer solution

Object of the invention: the development of a method of granulation of material of small tonnage production

The technical result achieved is:

- uniform distribution of plasticizer;

- reduction in the consumption of plasticizer solution.

To achieve a technical result, in a method for producing granular plasticized material, comprising mixing a powder material having poor formability with a plasticizer solution on a vacuum filter containing filter material and a vacuum pump, the powder is poured onto a perforated grid with conical holes placed on the filter material, the tops which are directed towards the movement of the solution, pour the plasticizer solution, turn on the vacuum pump and carry out the zeroing by filtration until the solution ceases to isolate.

The present invention became possible after the authors found that drying by evaporation of sprayed pulp occurs according to the theory of A.V. Lykova.

Figure 2 schematically shows a diagram of a possible mechanism of moisture transfer in a layer of a capillary-porous body that heats up (heat flux is directed from right to left) [Lykov A.V. Heat and mass transfer in capillary-porous bodies. M .: Gostekhizdat. 1954. 296 p.].

A device for producing granular plasticized material containing a vacuum filter containing filter material, a perforated grating placed on it with conical holes, the vertices of which are directed towards the movement of the plasticizer solution, and a vacuum pump.

A perforated grid gives the granules a shape. Conical holes granulate the material as a plasticizer solution passes through it and allow the granules to spontaneously spill out. Evacuation ensures the passage of the solution, removes its excess, compresses the granules and dries with air, which sucks the vacuum pump.

To achieve this goal, a perforated metal mesh with 1.0 mm conical holes is installed on the filter material, the vertices of which are directed in the direction of movement of the plasticizer solution.

Granules larger than 1.0 mm will not uniformly fill the cavity of the matrix when filling their mold.

Example 1. (Method prototype). 100 g of a mixture of BK8, with a particle size of 1-3 μm, were mixed with 10 ml of a 4% aqueous solution of polyvinyl alcohol. Stirred until smooth for 10 minutes.

Dried at a temperature of 70-80 ° C, wiped through a 0.4 mm sieve.

The final, second, drying was carried out with constant pouring.

Example 2. (The proposed method). On a Bochner funnel, Figure 3, on a filter with a white strip, 100 g of a VK8 mixture, with a particle size of 1-3 μm, Figure 4 was poured, then an aqueous 4% solution of polyvinyl alcohol was poured on top and the vacuum pump was turned on, Figure 5.

After 2 minutes, the solution was filtered, and the mixture on the filter was plasticized and partially dried by passing air through the sediment layer.

The filtrate is a pure solution of polyvinyl alcohol that does not contain particles of the mixture, Figure 6.

The plasticized material removed from the filter, Figure 7, without additional drying, in the state of capillary retained moisture, was directed to wipe through a 0.4 mm sieve.

Example 3. (The proposed method). According to the condition of Example 2, before placing the mixture on the filter paper, they placed a grate with a hole diameter of 0.5 mm, Figure 8. The figure shows that the holes have a conical shape, the apex of which is directed toward the filtrate. The diameter of the top of the truncated cone is 1 mm. This allows the removal of sediment (plasticized mixture) in the form of granules.

Example 4. Copper powder was poured onto a vacuum filter, fractions 0.63 + 0.4 mm, which has a scaly shape of particles and does not flow, Figure 9 [Preparation of copper powder from mill scale and its properties / T.V. Loginova et al. Deposited at VINITI on December 28, 2018) No. 564-V2011].

As a plasticizer was a 4 percent aqueous solution of polyvinyl alcohol.

The device operates as follows. A grid with conical holes is placed on the surface of the paper filter. The tops of the cones are facing in the direction of movement of the filtrate, and a layer of powder is poured onto it, then the solution is poured and the vacuum pump is turned on, which creates a vacuum in the flask.

The plasticizer solution is filtered through a layer of powder. After filtration, a thin layer of solution will remain on each particle. The thickness of this layer will be equal to the boundary layer (Ludwig Prandtl's theory).

After filtration, the material is removed from the holes in the perforated grid. For this, the perforated grate is turned over, the granules are poured out under the action of their own weight and the conical shape of the holes.

You can use vacuum filters with a descending cloth. The proposed method is competitive with spray drying.

Claims (3)

1. A method of producing granular plasticized material, comprising mixing a powder material with a plasticizer solution on a vacuum filter containing a perforated grating placed on the filter material with conical holes, the vertices of which are directed in the direction of movement of the solution, while the powder material is poured onto the perforated grating, the plasticizer solution is poured and carry out filtration in vacuo until the solution ceases to produce granular plasticized of material by extracting it from a lattice of holes. 2. A device for producing granular plasticized material containing a vacuum filter configured to mix powder material with a plasticizer solution, containing filter material and a perforated grid placed on it with conical holes, the vertices of which are directed toward the movement of the plasticizer solution, and the diameter allows plasticized removal material in the form of granules. 3. The device according to claim 2, characterized in that the conical holes have a vertex diameter of 1 mm.

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