RU2264981C1 - Electrode mass for self-roasting electrodes - Google Patents

Abstract

FIELD: electrical production of ferro-alloys and steel; manufacture of self-roasting electrodes.

SUBSTANCE: proposed electrode mass contains thermo-anthracite, coal-tar pitch and modifying agent in form of polymers of benzene separation at the following ratio of components, mass-%: thermo-anthracite, 70-79; coal-tar pitch, 20-28; polymers of benzene separation (wastes of by-product coke industry), 1-2. Ratio of fractions of thermo-anthracite in electrode mass, mass/%: -16+6 mm, 11-21; -6+0.063 mm, 28-38; the remainder being lesser than +0.063 mm. Benzene separation polymers have the following ratio of components, mass-%: agents not soluble in toluene, 2.0-4.0; water, 0.05-0.10; ash, 0.10-0.15; the remainder being aromatic hydrocarbons. Mechanical strength of electrodes is equal to 19.7-22.3 Mpa and porosity of electrodes is equal to 19.8-20.6%.

EFFECT: enhanced efficiency.

3 cl, 2 tbl

Description

The invention relates to electrothermal processes, namely to electroferroalloy and steelmaking, and is intended for use in the manufacture of continuous self-firing electrodes.

Known electrode mass for self-firing electrodes of ore-reducing electric furnaces (B. Strunsky. Ore-melting furnaces. M., Metallurgy, 1972, p. 165), containing thermal anthracite 30-60%, coke 20-55%, coal tar pitch 20-28 %

However, self-firing electrodes made of known mass have insufficiently high physical and mechanical characteristics in terms of electrical resistivity and compressive strength.

The closest in technical essence and the achieved result is the carbon mass for the production of self-burning electrodes, containing the following components, wt.%: Semi-coke 20-45, coal tar pitch 20-28 and thermoanthracite - the rest (USSR Author's Certificate No. 704896, IPC С 01 В 31 / 02, publ. 25.12.79).

However, the known mass, due to the content of semicoke in its composition, has high porosity, which negatively affects the resistance of the working end of the self-calcining electrode and reduces its mechanical strength.

The basis of the invention is the task of increasing the mechanical strength and reducing the porosity of the electrodes by introducing into the composition of the electrode mass, as a modifying additive, polymers of the benzene compartment, which are wastes of coke production.

The problem is solved in that the electrode mass for self-burning electrodes, including thermoanthracite and coal tar pitch, according to the invention, additionally contains, as a modifying additive, polymers of the benzene compartment, in the following ratio of components, wt.%:

thermoanthracite 70-79 coal tar pitch 20-28 benzene polymers 1-2

The ratio of fractions of thermoanthracite in the electrode mass is, wt.%:

-16 + 6 mm - 11-21 -6 + 0.063 mm - 28-38 less than +0.063 mm - the rest

In addition, the polymers of the benzene compartment have the following composition, wt.%:

toluene insoluble substances 2.0-4.0 water 0.05-0.10 ash 0.10-0.15 aromatic hydrocarbons rest

A causal relationship between the totality of the features of the claimed invention and the technical result that can be achieved is that introducing into the composition of the electrode mass for self-firing electrodes of polymers of the benzene compartment changes the nature of pitch carbonization due to physicochemical properties and, first of all, for due to the content of high molecular weight aromatic hydrocarbons. Aromatic hydrocarbons, in turn, have a positive effect on the formation of structures that contribute to better pitch coke formation. The binder molecules under thermal influence are able to decompose into weak structural units into large structural units - radicals, which subsequently, as a result of carbonation, pass into products of various forms. Deepening the carbonization process leads to the accumulation of high molecular weight compounds, due to which there is a better wetting of the filler and the formation of a thinner adsorption film. This circumstance, as well as the adsorption of a binder on the surface of the filler, provide the best sintering of disparate components of the mixture into one monolithic system. In addition, the ash of the polymers of the benzene compartment contains oxides of the type R ₂ O ₃ , that is, oxides of iron, aluminum and titanium, which in turn cause the development of the polycondensation process, increase the yield of coke residue and sharply reduce the activation energy of the system. The polymer content of the benzene compartment less than 1 wt.% Does not significantly affect the physico-mechanical characteristics of the electrode mass. An increase in the polymer content of the benzene compartment in excess of 2 wt.% Causes an increase in the yield of volatile substances.

One of the factors ensuring the thermal and operational stability of the working end of the self-firing electrode is the optimal content of the solid carbon filler — thermoanthracite and binder — coal tar in the composition of the proposed electrode mass. An increase in the thermal anthracite fraction of -16 + 6 mm more than 21 wt.% Entails a decrease in the mechanical strength of the working end of the electrode, and a decrease in its fraction below 11 wt.% Leads to a decrease in the electrically conductive frame. When the content of thermoanthracite fraction -6 + 0,063 mm more than 38 wt.% Decreases cementation of the grain frame and the wettability of larger fractions, and the content of less than 28 wt.% Leads to a decrease in the mechanical strength of the electrode.

An increase in coal tar pitch more than 28 wt.% Requires a significant expenditure of electrical energy for coking the electrode, and a decrease of less than 20 wt.% Does not provide a strong connection between the components.

The mismatch of the composition of the polymers of the benzene compartment to the claimed leads to significant changes in their properties, which, in turn, affects the physical and mechanical characteristics of the electrode mass.

The electrode mass is prepared as follows. Thermoanthracite is calcined at 1200-1300 ° C, and then subjected to crushing, followed by sieving on drum sieves or screens. The prepared materials are dosed according to the particle size distribution in accordance with a given mass recipe, then loaded into a mixer, into which at the same time an appropriate amount of initial coal tar pitch is fed, and they are thoroughly mixed. The polymers of the benzene compartment are heated to a temperature of 40-60 ° C, and then served in the mixer. After mixing in the mixer, the electrode mass is unloaded, molded into briquettes and delivered to the finished goods warehouse in the form of briquettes.

To prepare the electrode mass used:

- thermoanthracite with an ash content of not more than 5.0%, moisture - not more than 1.5% and with a specific electrical resistance of not more than 1000 Ohm · mm ² / m;

- coal tar pitch, having the following indicators:

softening temperature, ° C 67-73 ash content,% no more than 0.3 water content in pitch,% no more than 0.5 yield of volatiles,% 58-63

The content of the components in the compositions of the electrode masses are given in table 1.

Table 1 Components The composition of the electrode mass, wt.% Prototype 1 2 3 4 5 6 Thermoanthracite (fractions, mm): - according to the prototype * 27-60 - proposed 70-79 - -16 + 6 21.5 21 twenty eleven 21 10 - -6 + 0,063 26 28 24 28 28 37 - less than +0.063 33 thirty thirty 31 21 35 Semi-coke 20-45 - - - - - - Coal tar pitch 20-28 19 twenty 24 28 28 fifteen Polymers 0.5 1,0 2.0 2.0 2.0 3.0 benzene compartment * According to the prototype thermoanthracite contains: fractions, mm content, wt.% twenty 10 10-20 30-35 4-10 25-30 1-4 30-40

The test results of samples of electrode masses are shown in table 2.

table 2 Indicators The composition of the electrode mass Prototype 1 2 3 4 5 6 Mechanical strength, MPa 17.7-19.3 19.6 20.8 22.3 22.0 20,0 19.7 Porosity,% 20.9-24.1 20.9 19.8 19.5 20.5 20.3 20.6 Electrical resistivity, Ohm · mm ² / m 92.3-93.4 90.3 86.0 82.6 84.5 84.8 86.2

As a result of the tests, it was found that the samples of the mass made from the proposed composition (options 2-5) have higher mechanical strength and lower porosity, as well as lower electrical resistivity as compared to the mass made from the known composition. Therefore, self-baking electrodes made of the proposed mass will have higher mechanical strength and lower porosity, as well as lower electrical resistivity compared to electrodes made of known mass.

Along with improving the performance of self-baking electrodes, the use of the invention will expand the raw material base by introducing small fractions of thermoanthracite into the mass and using, as a modifier, polymers of the benzene compartment, which are waste products of coke production.

The claimed invention is based on experimental data obtained in laboratory conditions of the enterprise OJSC "Ukrgrafit".

Claims (3)

1. The electrode mass for self-firing electrodes, including thermoanthracite and coal tar pitch, characterized in that it further contains polymers of benzene compartment as a modifying additive in the following ratio of components, wt.%: Thermoanthracite 70-79 Coal tar pitch 20-28 Polymers of the benzene compartment 1-2 2. The electrode mass according to claim 1, characterized in that the ratio of fractions of thermoanthracite in it is, wt.%: -16 + 6 mm 11-21 -6 + 0.063 mm 28-38 Less than +0.063 mm Rest 3. The electrode mass according to claim 1, characterized in that the polymers of the benzene compartment have the following composition, wt.%: Toluene Insoluble Substances 2.0-4.0 Water 0.05-0.10 Ash 0.10-0.15 Aromatic hydrocarbons Rest