SU1642214A1 - Electrical resistance oven for graphitizing carbon blanks placed into core in a layer of heat insulating charge - Google Patents

Abstract

The invention relates to electric resistance furnaces and can be used in the electrode industry for high temperature processing (graphitization) of electrode products. The purpose of the invention is to save the charge and increase productivity when loading and unloading the furnace. For this, carbon blanks 3 are laid in the core in the heat insulating charge layer 7. The side walls 5 and the furnace 6 bottom are made in a curvilinear form according to the dependence x2 / (hK / 2 + а) 2 + у2 / (Ьк / 2 + а) 2 - 1 relative to the furnace center, where x is the vertical axis of the furnace cross section: y is the horizontal axis of the cross section of the furnace. chi; hx - core height; Bk is the core width, and is the thickness of the heat insulating layer. The temperature at each point on the inner surface of the furnace has the same value, which is equal to the maximum. 6 Il.

Description

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The invention relates to electric resistance furnaces and can be used in the electrode industry for high temperature processing (graphitization) of electrode and other products.

The purpose of the invention is to save the charge and increase productivity when loading and unloading the furnace.

FIG. 1 shows an electric resistance furnace for graphitizing carbon blanks; in fig. 2-6 are various embodiments of the side walls of the furnace and the bottom.

An electric resistance furnace for graphitization of carbon blanks laid in a core in a heat insulating charge layer contains end walls 1 with current leads 2 installed in them. Carbon blanks 3 with overflow 4 are laid in a core. The curvilinear shape of the side walls 5 and the bottom 6 is made according to the dependence relative to the center of the furnace

X2 y2

) 2 + (+ 7) 2 1

where x is the vertical axis of the furnace cross section;

y is the horizontal axis of the furnace cross section;

hx - core height;

Bk is the core width;

a is the thickness of the heat insulating layer. The core of the carbon blanks 3 is surrounded on all sides by a layer of heat insulating charge 7. The furnace design rests on reinforced concrete panels 8 and columns 9. From the top, the furnace is covered with an umbrella 10. Channels 11 are air.

The temperature distribution at various points on the inner surface of the furnace is described by a differential heat equation with an internal heat source. As a result of experimental and theoretical studies, it has been established that the isotherms in this case have the shape of a curve described by the equation of the ellipse, i.e.

- +

., l

(- f + a) 2 (- + a) 2

When the elements of the side walls and bottom of the furnace are made along a curve in a form equivalent to the isotherm, the temperature at each point of the internal surface of the furnace has the same value equal to the maximum.

The center of the furnace is taken as the geometric center of the cross-section of its core, formed from the grafted blanks assembled in a packet, through which

held horizontal (x) and vertical (y) axis. The ratio of the cross-sectional dimensions of the furnace core may be as follows

PI bk;

Bk bk - bk bk

An electric resistance furnace for graphitization of blanks placed in the core in the heat insulating charge insulation layer works as follows.

On the bottom of the furnace with a curved inner surface, a layer of heat insulating charge 2 is poured in

5 that its thickness along the vertical axis of the center of the furnace is equal to a. Then, along the longitudinal axis of the furnace, metal shields (not shown) are installed at a distance of the side thermal insulation layer and fixed by means of

0 t g to the upper parts of the side walls. The space between the side walls is filled with a heat insulating charge. Carbon blanks 3 are placed between the shields at a distance from each other (along

5 of the longitudinal axis of the furnace) and the pouring of the 4 - coke nut is poured, i.e. a furnace core is formed between the shields. The shields are then removed using a crane and a layer of heat insulating charge 6 is poured over the core of the furnace. An umbrella 10 connected to the gas removal system is installed on top of the furnace. The oven is ready to be connected. When the furnace is connected to a power source, electric energy is introduced into the furnace according to a predetermined power schedule. As a result of the current flowing through the furnace core, almost all Joule energy (95-99%) is released in the transfer layer 4, and the billet by means of heat conduction

0 warmed up from the charge. The billet is heated to 2400-3000 ° C depending on the required quality of the graphitized billets. After reaching the set temperature (after 40-60 hours of heating), the furnace

5 is cooled for 6-12 days until the temperature of the blanks reaches 800 ° C, after which the furnace is discharged.

After switching off the furnace from the current, the pattern of heat distribution in the cross section of the furnace does not change. For some time (10--30 h) the temperature at the boundary of the heat-insulated charge - the lining is growing. Therefore, the heat insulation layer is chosen so that the highest temperature on the surface of the lining is

5 did not exceed 1100-1200 ° С.

In the proposed furnace design, the inner surface of the cross-section of the bottom and side walls is made in the shape of an ellipse, so the temperature on the surface of these elements is the same. By reducing the cross-sectional area, the amount of heat insulating charge loaded into the furnace is 4-15% less than in the prototype. This makes it possible to reduce the volume of loading and unloading operations and to provide savings in thermal insulation materials.

Claims (1)

Claims of the Invention An electric resistance furnace for graphitization of carbon blanks stacked in a core in a heat and solvent mixture layer, comprising end walls with current leads installed in them, side walls and a curvilinear bottom, characterized in that. what with the purpose Fig 5 saving the charge and increasing productivity when loading and unloading the furnace, the curvilinear shape of the bottom and side walls is made according to - +  one () 2 () 2 iv 2 relative to the center of the furnace, where x is the vertical axis of the furnace cross section; y is the horizontal axis of the furnace cross section; hk - core height; bk - core width; a is the thickness of the heat insulating layer. Fig 6