RU2243817C1 - Method of electrocalcination of loose carbon material - Google Patents

Abstract

FIELD: electrode industry; production of carbon-graphitic materials.

SUBSTANCE: the invention is dealt with methods of calcination of granular carbon materials, for example - an anthracite, and may be used in an electrode industry for production of carbon-graphitic materials with the help of high-temperature heating by an electric current. Substance: the method of electrocalcination of a loose carbon material includes loading a source material in the electrocalciner, its passing sequentially through the extended both narrowed zones of the electrocalciner and discharge of the final product. At that in the narrowed most heated zone of the electrocalciner, the diameter of which makes 0.25-0.6 of the diameter of the extended zone, they make concentration of the current field lines causing natural mixing of the loose carbon material. At that passing of the peripheral mass of the loose carbon material from the extended zone into the narrowed zone is realized on the surface, inclination of which is by 2-10 degrees less than angle of friction of the loose carbon material and the surface. The invention ensures improvement of quality of produced loose carbon material and decreased consumption of the electric power used for realization of electrocalcination.

EFFECT: the invention ensures improved quality of produced loose carbon material and a decrease of electric power input for the process of electrocalcination.

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Description

The invention relates to methods for calcining bulk carbon materials, such as anthracite, and can find application in the electrode industry for producing carbon graphite materials using high-temperature electric current heating.

The crushed anthracite is subjected to high-temperature calcination — electrocalcination — to obtain conductive carbon-graphite material, which serves as a raw material for the manufacture of, in particular, high-temperature carbon-graphite electrodes.

Existing methods of electrocalcination of anthracite do not provide a sufficient level of yield of product, i.e. carbon-graphite material having homogeneous properties, namely electrical resistivity.

A known method for the continuous calcination of bulk carbon material is loaded into a furnace — a shaft-type electric calciner with lined walls and heated by an electric current passing between two electrodes — the upper and lower and the mass of the specified bulk carbon material — and discharged after passing through the entire space of the furnace (Electrothermal equipment. Handbook edited by A.P. Altthausen (Moscow: Energia, 1980, p.194-208).

The disadvantage of this method of electrocalcination is the irrational expenditure of electrical energy. The electric current flowing from one electrode to another through the masses of the processed material is distributed in the space of the furnace, while, as a rule, it forms certain channels for its passage. Such sewage prevents the uniform heating of the entire mass of the calcined material, which causes heterogeneity of the properties of the finished product, reduces its performance. In addition to the above, the uneven distribution of the current channels leads to local overheating of the furnace lining and its premature failure.

The closest is the method of calcination of bulk carbon material, implemented by Auth. St. No. 1434224 “Continuous electrocalciner”, IPC ⁴ F 27 B 3/08, publ. 10.30.88, BI 40, including loading the source material into the electrocalciner, passing the material sequentially through several expanded and narrowed zones of the electrocalciner while heating the material by passing electric current and unloading the finished product. The narrowed zones are formed by the annular protrusions of the lining of the electrocalciner, on which the peripheral mass of the bulk material hangs, which leads to a decrease in the yield of the product, since not all the loaded material passes through the high-temperature heating zone, and spontaneous channels of the flow of electric current or its dissipation by the mass of calcined material, which increases energy consumption, causes local overheating of the lining with its subsequent failure, as well as incomplete thermal processing of material that is located either outside the zones of spontaneous sewage of electric current, or in areas with insufficient density of electric current if it is scattered by the mass of bulk carbon material.

The disadvantage of this method is the heterogeneity of the finished product according to the main characteristic of the specific electrical resistance and loss of electricity.

The basis of the invention is the task of improving the quality of the obtained bulk carbon material, such as anthracite, by reducing the electrical resistivity, as well as reducing unproductive energy costs for the implementation of the electrocalcination process.

The problem is solved in that in the method of electrocalcification of bulk carbon material, which includes loading the source material into the electrocalciner, passing the material sequentially through the expanded and narrowed zones of the electric calciner with simultaneous heating by electric current and unloading the finished product according to the invention in the narrowed most heated zone of the electric calciner, the diameter of which is 0.25-0.60 of the diameter of the expanded zone, the concentration of the power lines of the stream and the natural trans mixing of particulate carbon material such as anthracite, the transition of the peripheral mass of said material from the wide area in the narrowed carried on the surface of which inclination angle is 2-10 degrees less than the angle of friction of the bulk material of the carbon material surface.

The passage of the mass of bulk carbon material through the narrowed zone and its mixing before entering this zone will increase the uniformity of the properties of the obtained material due to the fact that the entire processed anthracite passes through the zone of greatest heating of the electric calcinotor, in this zone the greatest concentration of streamlines occurs. If the diameter of the narrowed zone is less than 0.25 of the diameter of the expanded zone, then the carbon material will crack and grind, if more than 0.6, then the peripheral masses of the processed material will fall into the zone of the electric calciner, subject to less heat, and the material will not receive necessary heat treatment.

The mixing of the initial anthracite and its unhindered entry into the narrowed, most heated zone is also facilitated by the fact that the peripheral masses of the carbon material flow from the expanded zone to the narrowed along an inclined surface. If the angle of inclination of the surface is less than 2 degrees from the angle of friction of anthracite on the surface material, carbon material will accumulate on the throttle surface. If the angle of inclination of the surface is more than 10 degrees from the angle of friction of the carbon material on the surface material, then the mass of carbon material will rapidly converge with possible surface damage.

After the narrowed zone, the heat-treated material enters the expanded zone again, where it is additionally mixed, averaged, and gradually cooled before unloading.

The drawing shows a diagram of the method.

The bulk mass of carbon material, such as anthracite, is loaded into the electrocalciner through the upper loading device (not shown in the drawing). Subsequently, the mass moves in the electric calciner under the action of gravitational forces at a speed that is controlled by the removal of the processed material through the lower discharge device (not shown in the drawing). The loaded material is first heated by heat transfer from the hot gases of the dry distillation of the carbon material, and then, when the heated carbon material acquires sufficient electrical conductivity, by generating electrical contact heat at the points of electrical contact between the individual pieces of bulk material when an electric current is passed through the furnace between the top 1 and bottom 2 electrodes from the power source 3. The highest temperature (up to 2500 ° C) is concentrated along the axis of the power lines of the stream (indicated by arrows). With distance from the axis, the temperature of the mass decreases.

The loaded mass of carbon material (indicated by dashed lines in the drawing) falls into the expanded zone 4, where it is preheated, then the mass flows into the narrowed most heated zone 5, while the peripheral masses of the carbon material are poured to the central part, the mass is naturally mixed before hit in the narrowed area of the electrocalcinator. Then, all the material calcined at high temperature passes into the expanded zone, where it is subjected to cooling before unloading the finished carbon-graphite material.

Example 1

The next time the lining was replaced, a choke made of a special carbon material was installed in the upper half of the shaft type electrocalciner. The throttle is made of sections forming a continuous hole, the diameter of which is 500 mm, which is a quarter of the inner diameter of the lining. The upper surface of the throttle sections is made with a slope of 58 geometric degrees to the horizontal, which is 2 geometric degrees less than the angle of friction of anthracite on a special carbon material, which is 60 degrees.

Before the electrocalcinator was put into operation, its internal volume was fully loaded with thermoanthracite with a particle size of 6-8 mm. Then the power supply was turned on by electric current and a voltage of 60 V was applied to the electrodes. The current flows from one electrode to another through the mass of anthracite and heats it. In the upper expanded zone, anthracite is heated to a temperature of 800 ° C, then the treated anthracite enters the narrowed zone, where the temperature reaches 2500 ° C, while the peripheral masses of anthracite flow over the inclined surface of the throttle, mixing with the bulk. In the lower expanded zone, the mass of anthracite is pinned due to its heat content and subjected to forced cooling to 500 ° C.

The continuous movement of the mass of anthracite in the electrocalciner occurs under the influence of gravity at a speed of 600 kg per hour. This mass movement of coal was supported by unloading calcined anthracite from the lower part of the electrocalciner in portions of 100 kg every 10 minutes. The residence of the material in the furnace from loading to unloading was 15 hours.

The resulting calcined anthracite was tested. The electrical resistivity determined in accordance with GOST 23776-79 was 500 μOhm · m. The specific energy consumption was 750 kWh / t.

Example 2

The next time the lining was replaced, a choke made of a special carbon material was installed in the upper half of the shaft type electrocalciner. The throttle is made of sections forming a continuous hole, the diameter of which is 950 mm, which is 0.5 of the inner diameter of the lining. The upper surface of the throttle sections is made with a slope of 54 geometric degrees to the horizontal, which is 6 geometric degrees less than the angle of friction of anthracite on a special carbon material, which is 60 degrees.

Before the electrocalcinator was put into operation, its internal volume was fully loaded with thermoanthracite with a particle size of 6-8 mm. Then the power supply was turned on by electric current and a voltage of 65 V was applied to the electrodes. The current flows from one electrode to another through the mass of anthracite and heats it. In the upper expanded zone, the anthracite was heated to a temperature of 1000 ° C, then the peripheral masses of the anthracite flow along the inclined surface of the throttle into the narrowed zone, mixed with the bulk of the anthracite, and heat up to 2700 ° C. Then the mass falls into the expanded zone under the throttle. In the lower expanded zone, the mass of anthracite is pinned due to its heat content and subjected to forced cooling to 500 ° C.

The speed of anthracite movement in the electrocalciner was maintained at 650 kg per hour. The stay of the material in the furnace from loading to unloading was about 15 hours.

The resulting calcined anthracite was tested. He had a specific electrical resistance of 560 μΩ · m. The specific energy consumption amounted to 770 kWh / t.

Example 3

The next time the lining was replaced, a choke made of a special carbon material was installed in the upper half of the shaft type electrocalciner. The throttle is made of sections forming a continuous hole, the diameter of which is 1150 mm, which is 0.6 of the inner diameter of the lining. The upper surface of the throttle sections is made with an inclination of 50 geometric degrees to the horizontal, which is 10 geometric degrees less than the angle of friction of anthracite on a special carbon material, which is 60 degrees.

Before the electrocalcinator was put into operation, its internal volume was fully loaded with thermoanthracite with a particle size of 6-8 mm. Then the power supply was turned on by electric current and a voltage of 65 V was applied to the electrodes. The current flows from one electrode to another through the mass of anthracite and heats it. In the upper expanded zone, anthracite was heated to a temperature of 1200 ° C, then along the inclined surface of the throttle, the peripheral masses of anthracite flow into the narrowed zone, mixed with the bulk of the anthracite, and are heated to 3000 ° C. In the lower expanded zone, the mass of anthracite is pinned due to its heat content and subjected to forced cooling to 500 ° C.

The speed of anthracite movement in the electrocalciner was maintained by constant discharge at the level of 700 kg per hour. The stay of the material in the furnace from loading to unloading was 16 hours.

The resulting calcined anthracite had a specific electrical resistance of 700 μOhm · m. The specific energy consumption amounted to 770 kWh / t.

Obviously, the installation of a throttle (narrowing of a part of the volume of the electrocalciner) had practically no effect on the unit's performance due to rationally selected parameters of the narrowed zone, in which, according to well-known physical laws, an increase in the linear velocity of anthracite movement occurs, which compensates for the smaller cross section of the hole in the throttle.

The test results of products manufactured according to the prototype and the claimed method, as well as the cost of electricity are given in table 1.

Table 1 Electrocalcination process parameters Prototype method The inventive method Electrical resistivity (average), μOhm · m 900-1000 No more than 800 Specific energy consumption, kW · h / t 1100 700-750 Duration of the overhaul period, rel. 1 1,2- 1,5

From table 1 it can be seen that the use of the proposed method of electrocalcification of bulk carbon material in comparison with the known method can improve the quality of the resulting bulk carbon material, for example anthracite, by reducing the electrical resistivity by 1.2-1.3 times, and also reduce unproductive consumption electricity for the implementation of the electrocalcination process in 1.4-1.7 times.

In addition, the inventive method additionally allows to increase the length of the overhaul period and increase the durability of existing types of lining or to use a lining with lower indices of durability, and therefore, cheaper.

Claims (1)

The method of electrocalcification of bulk carbon material, including loading the source material into the electrocalciner, passing the material sequentially through the expanded and narrowed zones of the electrocalciner and unloading the finished product, characterized in that in the narrowed most heated zone of the electrocalciner, the diameter of which is 0.25-0.6 of the diameter the expanded zone, carry out the concentration of streamlines and the natural mixing of bulk carbon material, and the transition of the peripheral mass of bulk carbon material from the expanded zone to the narrowed is carried out on a surface whose angle of inclination is 2-10 ° less than the angle of friction of the granular carbon material on the surface material.