RU2344992C1 - Method of obtaining burnt and graphited carbone materials - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: carbonic filler, for instance, crashed coke, and bake binding agent in amount 20-25% of total press-mass amount are mixed in intensive mixer. Then from obtained press-mass work piece is formed and crashed by broaching pressing. Crashed mass is put in heated mixer with Z-like blades, 2-5% of total amount of binding agent is added, and is mixed again during 60-90 minutes. From press-mass work piece is formed again by broaching pressing, which is burnt, impregnated with bake, burnt again and graphited. Obtained burnt and graphited material has high physical-mechanic characteristics: cubic density of "green" work pieces - 1.73 g/cm³, cubic density after graphitisation - 1.76 g/cm³, flexural strength- 20.1 MPa.

EFFECT: high physical-mechanic characteristics of material.

3 ex

Description

The invention relates to electrode production, in particular to the production of graphite electrodes and nipples, and can be used in the smelting of electric steel in the metallurgical industry and structural materials for nuclear and electrothermal technology.

A known method of producing graphitized material described in clause of the Russian Federation No. 2252190 by class. СВВ 31/02, СВВ 35/52, declared 03/12/04, publ. 05/20/05.

The known method involves mixing crushed shale tar coke to a fractional composition, in which the fraction of a fraction of less than 0.09 mm is at least 97 wt.% And the fraction of a fraction of less than 0.045 mm is at least 91 wt.%, With coal tar pitch and an organic additive at a temperature of 120-130 ° С, mass formation with its subsequent grinding into a press powder, pressing in blanks of blanks with a density higher than 1.0 g / cm ³ , burning blanks at a temperature of 800-1300 ° С and graphitization at temperatures up to 3000 ° C, as organic obavki apply sterically hindered phenols and / or fenilfosfity blanks compressed to a density of 1.01-1.06 g / cm ^3, and the starting components are taken in the ratio (wt.%):

coal tar pitch 35-40,

organic additive 0.015-1.5,

tar shale coke - the rest.

The disadvantage of this method is as follows.

The resulting mass after cooling and grinding is pressed into a mold, the mass is not suitable for piercing pressing. The blanks pressed in the mold have a low bulk density (1.01-1.06 g / cm ³ ) and limited size compared to piercing pressing. The patent does not contain information on the possibility of impregnation of fired blanks with pitch or other impregnates in order to increase physical and mechanical properties.

A known method of producing high-strength graphitized material described in clause of the Russian Federation No. 2160704 by class. СВВ 31/04, declared 05/21/98, 12/20/2000

The known method consists in the fact that 62.3 wt.% Non-calcined coke of shale resin fine fraction with a particle size of 0.02-0 mm is not less than 80%, 0.09-0.02 mm - the rest is mixed in a horizontal mixer with SM blades -2000 with a rotor speed of 22.4 and 12.9 rpm with 37 wt.% Coal tar pitch and 0.7 wt.% Organic surfactant at a temperature of 120-130 ° C, then the mixture is molded under pressure up to 3 5 MPa, cooled, crushed, the obtained powder is pressed out of the preform with density 1,08-1,15 g / cm ^3, calcined at a temperature of 800-1300 ° C, graphitizable When 2500-3000 ° C.

In mixers of this type, the maximum value of the shear deformations of the pitch-carbon mass is achieved in the gap between the rotating blade and the casing; in the remaining parts of the volume, the shear stresses are much lower. In the gap between the blade and the wall, overgrowth of large grains of the filler occurs, which leads to an undesirable and uncontrolled change in the given particle size distribution of the “dry” mixture. The consequence of the non-uniformity of the shear strain field is the inhomogeneous distribution of the gas phase (air inclusions and volatile components of the binder) in the mass. After cooling and grinding, the mass is pressed in a mold, and not by a piercing method, and “green” blanks with a low bulk density (1.08-1.15 g / cm ³ ) are obtained. Uneven mass density is one of the possible reasons for the deterioration of the formability of the mass, the occurrence of internal defects in the workpiece during extrusion pressing or vibroforming. Structuring the mass in such a mixing machine is practically not provided.

There is a method of preparing pitch-carbon mass for the subsequent production of calcined and graphitized carbon materials, described in the book by A.M. Tsyganok et al. "The choice of a new design of the mixer for the production of pitch-carbon masses" Collection of scientific papers "Technological processes and equipment for electrode production" Research Institute of Graphite, GosNIIEP, M., 1989, pp. 24-32.

The method includes preparing a mixture of pitch and / or petroleum coke and coal tar pitch, dosing cokes and pitch and mixing them when heated.

Mixing of coke and pitch is carried out in an intensive mixer with vertically arranged working bodies with a rotation speed of 48 rpm and up to 71 rpm at a pitch and charge temperature of 110 to 135 ° C with a binder content of 16 to 20%, with high shear stresses in the mixed mass with the formation of the extremely destroyed coagulation structure to give the mass the corresponding structural-mechanical (rheological) properties under the action of mass-sealing forces. As a result of the destruction of the initial structure of the pitch and the creation of a new structure of the binder layer, the physicochemical properties of the pitch-carbon mass as a highly filled dispersed system, leading to an increase in the physicomechanical properties of carbon materials, change. When using intensive mixers with vertically arranged working bodies, there is no crushing of filler grains, because shear stresses are realized due to mechanical stresses created by counter mass flows, and not due to the passage of the mixed components through the gap between the blade and the mixer wall.

Intensive mixing makes the press mass homogeneous, with low ductility, with the formation of a structured layer of coal tar pitch on the surface of the filler grains. The resulting structured layer does not have the ability of plastic flow, it seems to acquire some properties of solids, which does not allow to obtain "green" blanks with high density during piercing pressing. When firing “green” billets, pressed by a piercing method, from a mass prepared using an intensive mixer, a carbon material with a finely porous structure without channel pores is obtained, which has low gas permeability and does not provide complete impregnation of the billets, which can lead to the appearance of internal stresses that reduce the strength characteristics.

There is a method of obtaining calcined and graphitized materials described in the collection of scientific papers (Collection No. XVII "Structural materials based on carbon", V. A. Filimonov and others. "The study of the effect of mixing on improving the quality of graphite material", M., Metallurgy, 1983 g., pp. 12-15).

In the known method, a press pulp is prepared by mixing finely divided petroleum coke with coal tar pitch in a continuous mixer of the type SN-100, the working parts of which are mounted on the shafts of the nozzle in the form of direct and reverse feed screws. The screws are located in two mating cylinders. The raw material is commercial petroleum coke, crushed to a particle size of less than 0.15 mm with a fraction content of less than 0.09 mm - 90%, as well as coal tar pitch with a softening temperature of 70 ° C, which is heated to 115-120 ° C. The ratio of the components of the "coke": "pitch" = 3: 2. Mixing is carried out at a temperature of 150-160 ° C. The mixing time is about 5 minutes (mixer performance about 100 kg of mass per hour).

The coke pitch pitch coming out of the mixer is cooled, crushed, and ground in a vibrating mill. From the obtained press powder, 230 × 170 × 100 mm blocks (block No. 1) and 115 × 115 × 200 mm (block No. 2) are molded in a mold, which are fired and graphitized in industrial furnaces according to the accepted regimes.

In the mixer used, the components are mixed in a relatively small volume, free from nozzles, mainly at the junctions of the forward and reverse turns of screws. The movement of mass in a limited volume occurs under the action of large oppositely directed forces. This movement provides intensive mixing of the components and compaction of the mass, intensive displacement makes the mass homogeneous, and compaction contributes to its structuring.

The disadvantage of this method is that the resulting mass after cooling and grinding is suitable for pressing in the mold, and not piercing pressing, to obtain blanks with a low density of 1.12-1.14 g / cm ³ and small overall dimensions of 230 × 170 × 100 mm m 115 × 115 × 200 mm.

Closest to the technical nature of the claimed is a method for producing fine and fine-grained graphitized material described in the same patent of the Russian Federation No. 2035395 in class. СВВ 31/04, declared 06/20/91, publ. 05/20/95 and selected as a prototype.

A known method is as follows.

A press mass is prepared from calcined petroleum pyrolysis coke, milled to a grain size of less than 40 microns, and high-temperature coal tar pitch with a softening temperature of 135-150 ° C at a ratio of components, wt.%: Coke 65-72, pitch 35-28, mixed in paddle mixer at a temperature of 250-280 ° C, grind the obtained coke-pitch composition to a grain size of less than 150 microns, form blanks from the obtained powder powder by cold pressing, burn the formed blanks, impregnate medium-temperature coal boiled pitch, and then re-fired and graphitized.

The disadvantage of this method is as follows.

The use of a paddle mixer in the preparation of the press mass leads to the fact that the maximum value of the shear deformations of the pitch-carbon mass is achieved in the gap between the rotating blade and the body, and in the remaining parts of the volume, the shear stresses are much lower. In the gap between the blade and the wall, overgrowth of large grains of the filler occurs, which leads to an undesirable and uncontrolled change in the given particle size distribution of the “dry” mixture. The non-uniformity of the shear strain field results in an inhomogeneous distribution of the gas phase (air inclusions and volatile components of the binder) in the mass discharged from the mixer. So, with an average bulk density of the finished mass of 1.15-1.25 g / cm ³ , individual lumps have an apparent density of up to 1.45 g / cm ³ . Uneven mass density is one of the possible reasons for the deterioration of the formability of the mass, the occurrence of internal defects in the workpiece during extrusion pressing or vibroforming, which leads to a deterioration in the physical and mechanical characteristics of the material, such as strength characteristics. Structuring the mass in such a mixing machine is practically not provided.

The objective of the proposed method is to improve the physico-mechanical characteristics of calcined and graphitized materials.

The problem is solved in that in the method for producing calcined and graphitized carbon materials, a press mass is prepared by mixing the carbon filler with a pitch binder in a mixer when heat is supplied, crushed, pressed, calcined pressed workpiece, impregnated with pitch, re-calcined and graphitized, according to the invention the mass is mixed in an intensive vertical mixer, after which it is molded by piercing pressing, the formed workpiece is crushed, after crushing the formed workpiece to measure For the pulped mass, a pitch binder is added, the components are mixed in a heated horizontal mixer with Z-shaped blades and only then pressed, and when the press mass is first mixed, 20-25% of the binder of the total mass of the press mass is introduced into the mixture, and with the second stirring - 2-5% of the binder of its total amount.

Intensive mixing results in a homogeneous press mass with low ductility, with the formation of a structured layer of coal tar pitch on the surface of the filler grains. The resulting structured layer does not have the ability of plastic flow, it acquires some properties of solids, which does not allow to obtain "green" workpieces with high density during piercing pressing. When firing “green” billets, pressed by the piercing method, from the mass prepared using an intensive mixer, a carbon material with a finely porous structure, without channel pores, which has low gas permeability and does not provide complete impregnation of the billets, is obtained, which can lead to the appearance of internal stresses that reduce strength characteristics.

Repeated mixing of the crushed workpiece in a horizontal mixer with the addition of pitch eliminates the stagnant zones in the press mass, makes it more plastic, allowing the pitch to evenly distribute throughout the volume and creates favorable conditions for subsequent processing of the material.

When firing "green" billets to temperatures of 800-1200 ° С, volatiles are released and pitch coking is promoted, which promotes the formation of channels similar to wormholes, the cross section of which can remain at the level of "structural gaps". The impregnation efficiency is determined by the value of porosity, i.e. the number and size of these gaps. The additional impregnation of such calcined billets with pitch ensures complete impregnation due to channel pores, which increases the mechanical strength and electrical conductivity of the material.

EFFECT: obtaining a homogeneous mass with the formation of a structured layer of coal tar pitch on the surface of the filler grains, increasing the plasticity of the mass, providing more complete impregnation, obtaining a more dense and durable material.

The inventive method has a novelty in comparison with the prototype, differing from it by such significant features as the use of the first mixer intensive mixer and 20-25% pitch of the total amount of press mass, molding after the first mixing, adding to the mass of crushed billet of pitch in the amount of 2 -5% of its total amount and re-mixing of the press mass in a horizontal mixer with Z-shaped blades, which together ensure the achievement of a given result.

The applicant is not aware of technical solutions that have the indicated distinguishing features, which together ensure the achievement of a given result, therefore, he believes that the claimed method meets the criterion of "inventive step".

The inventive method can be widely used in the metallurgical industry, and therefore meets the criterion of "industrial applicability".

The inventive method is as follows.

A carbon filler pre-prepared by known technology, for example, crushed coke, as well as pitch binder in an amount of 20-25% of the total amount of press material, is mixed in an intensive mixer, after which a preform is crushed from it to be crushed. Then the crushed mass is poured into a heated mixer with Z-shaped blades, 2-5% of the total amount of the binder is added and mixed again for 60-90 minutes. A blank is formed from the press mass by piercing pressing, which is subjected to calcination, impregnation with pitch, then re-calcination and graphitization.

The implementation of the method is illustrated by the following implementation examples.

Example 1

Filler - calcined petroleum coke, crushed to a particle size of 0-2.5 mm - 77% by weight. Binder - coal tar pitch with a softening temperature of 70 ° C - 23% by weight.

The components were mixed for 5 min at a temperature of 130-140 ° C in an intensive mixer with vertical rotors with a speed of 210 and 260 rpm. The resulting mass was cooled in a mixer to 100-110 ° C, then billets of 225 mm diameter, 1520 mm long were extruded by extrusion. The billets were fired, impregnated with coal tar pitch, re-fired and graphitized.

Example 2

Filler - calcined petroleum coke, crushed to a particle size of 0-2.5 mm - 77% by weight. Binder - coal tar pitch with a softening temperature of 70 ° C - 23% by weight.

The components were mixed for 1 hour in a heated mixer with a capacity of 2000 l with a rotation speed of Z-shaped blades 23.3 and 14.7 rpm at a temperature of 130-140 ° C. The resulting mass was cooled in a mixer to 100-110 ° C, then the workpieces were pressed by extrusion method with a diameter of 225 mm, a length of 1520 mm. The billets were fired, impregnated with coal tar pitch, re-fired and graphitized.

Example 3

Filler - calcined petroleum coke, crushed to a particle size of 0-2.5 mm - 77% by weight. Binder - coal tar pitch with a softening temperature of 70 ° C - 23% by weight.

The components were mixed for 5 min at a temperature of 130-140 ° C in an intensive mixer with the above parameters. The resulting mass was cooled in a mixer to 100-110 ° C, then billets of 225 mm diameter, 1520 mm long were extruded by extrusion. The blanks were pressed after pressing, then crushed to a fraction of 0-30 mm. The crushed fraction of 0-30 mm was loaded into a heated horizontal mixer with Z-shaped blades, stirred for 1-1.5 hours at a temperature of 130-140 ° C with the addition of a binder in an amount of up to 5%. The resulting mass was cooled in a mixer to 100-110 ° C, then billets of 225 mm diameter, 1520 mm long were extruded by extrusion. The billets were fired, impregnated with coal tar pitch, re-fired and graphitized.

After pressing, the bulk density of the preforms was determined; after graphitization, the bulk density and strength (ultimate tensile strength). The data obtained are shown in the table below.

Example Bulk density of green blanks, g / cm ³ After graphitization Bulk density, g / cm ³ Bending Strength, MPa one 1,66 1.70 15.1 2 1.70 1.72 18.3 3 1.73 1.76 20.1

Obtained by the present method, calcined and graphitized carbon materials have higher physical and mechanical characteristics.

In comparison with the prototype of the inventive method can improve the physico-mechanical and electrophysical characteristics of calcined and graphitized materials, such as bulk density and bending strength.

Claims (1)

The method of obtaining burnt and graphitized carbon materials, which consists in the fact that the press is prepared by mixing the carbon filler with a pitch binder in a mixer when heat is supplied, crushed, pressed, calcined pressed billet, impregnated with pitch, re-fired and graphitized, characterized in that the press mass is mixed in an intensive vertical mixer, after which it is molded by piercing pressing, the formed workpiece is crushed, after crushing the formed workpiece to the ground mass add a pitch binder, mix the components in a heated horizontal mixer with Z-shaped blades and only then press, and during the first mixing of the press mass, 20-25% of the total amount of the press mass is introduced into the mixture, and 2-5 % binder of its total amount.