RU2259528C1 - Electric furnace for burning of pottery - Google Patents

Abstract

FIELD: periodic-action electric furnaces for burning of pottery.

SUBSTANCE: the electric furnace has a vertical lined heating chamber, installed along side walls of which are one above another by the method of "Well" are carborundum heaters, movable bottom with double sand lock, spiral wire heater located in the grooves of the bottom, boms for installation of the product, mechanisms for bottom lifting, lowering and rotation. The heating chamber is made hexahedral, tables are installed on the furnace bottom for rotation about its own axis, each table is made in the form of a heat-resistant sleeve, installed in which is a power ceramic support with a ceramic centering plug, and installed on the upper end face of the support is a ceramic power support, on which the boms is installed at the height of the bottom, equal 0.4 to 0.6 diameter of the boms, but not lower than the second row of wall heaters.

EFFECT: enhanced furnace capacity and enhanced quality of burnt products.

1 note, 1 tbl, 2 dwg

Description

The invention relates to batch electric furnaces for high-temperature firing of large-sized, complex-shaped ceramic products such as nose dielectric cones of aircraft.

A known furnace for heat treatment of hollow, dimensional, thin-walled ceramic products (Autosvid. USSR No. 853328, class F 27 B 9/06, 1979), consisting of a lined heating chamber, on the walls of which are mounted wire heating elements, and placed on a trolley ceramic frame with slots in which the wire heater is laid. A fired product is installed on this ceramic frame, on top of which a metal frame is installed. The gaps between the product, ceramic and metal frames are filled with a powdery filler.

The disadvantages of this furnace include the low realizable temperature (1000-1100 ° C), which wire heaters are able to provide, the inability to heat-treat closed-shape products, the difficulty in manufacturing frames of the corresponding shapes, the fragility of the metal frame due to high temperatures.

The closest technical solution is an electric furnace for firing quartz ceramics (Malashenko V.P., Rudenko P.V. et al. Electric furnace for firing quartz ceramics. // Glass and ceramics, No. 8, 1971. - S.29-30), containing a vertical lined heating chamber of square cross section, along the side walls of which a "well" carbide-silicon hearth heaters with a double sand shutter are stationary installed one above the other, a bombs for installing a large-sized complex ceramic product located in the center of the hearth, a spiral wire heater located in the grooves of the hearth, the mechanisms for raising, lowering and rotating the hearth.

The disadvantage of the design of this electric furnace is that the heating chambers of the furnaces of this type perform a square section. This embodiment of the heating chamber leads to the fact that under the furnace has small dimensions. The small dimensions of the hearth of the furnace determine its low throughput, since the workpiece is located alone in the center of the hearth on the bomb, so only one workpiece is burned in one mode of the furnace, which is unacceptable in mass production, since there is a need to increase the fleet of furnaces.

Another disadvantage is that the baked billets are mounted on a bomb located on the bottom of the furnace, and due to significant heat losses through the under from the massive refractory, large heat accumulation by the hearth lining, which removes heat from the bottom of the heating chamber, uneven heat flow can occur the height of the product and, as a consequence, the uneven sintering and crystallization of the workpieces throughout the volume, the occurrence of local stresses in them, which can lead to the conclusion of the workpieces into marriage. This disadvantage is due to the fact that the hearth of the prototype is 25% of the area of the side walls of the working chamber, and the power of the hearth heater, which can be made only of wire spirals, is only 7%, which leads to the fact that it remains colder under the furnace compared to the walls of the heating chamber. The low power of the hearth heater of the prototype is also due to the inability to place a larger number of spirals on a small surface of the hearth.

The objective of the present invention is to increase the productivity of kilns for firing ceramic products, reducing specific energy consumption per unit of production and improving the quality of fired large-sized complex products.

This object is achieved by the fact that the proposed electric furnace for firing ceramic products, containing a vertical lined heating chamber, along the side walls of which are installed one above the other "well" silicon carbide heaters, movable under with a double sand shutter, a spiral wire heater located in the grooves of the hearth, a bomb for installation of the product, mechanisms for raising, lowering and rotating the hearth, characterized in that the heating chamber of the furnace is hexagonal, installed on the hearth of the furnace There are tables with the possibility of rotation around their own axis, each table is made in the form of a heat-resistant glass in which a ceramic power support with a ceramic centering plug is inserted, and a ceramic power substrate is installed on the upper end of the support, on which a bomb is mounted at a height from the hearth of 0, 4-0.6 diameter bombs, but not lower than the second row of wall heaters.

The authors experimentally established that the implementation of the hexagonal heating chamber can significantly increase the hearth area and expand the technological capabilities of the electric furnace.

The enlarged under allows you to install tables on its surface that are rotatable around its own axis, which hold the fired products on the bombs, while only one product is installed on each table. The number of installed tables is limited only by the dimensions of the fired ceramic products. Thus, due to this embodiment of the heating chamber and the furnace hearth, the consumption of electric energy per unit of production is significantly reduced, and the throughput of the furnace is also significantly increased.

It was experimentally established that the execution of tables for the installation of a bomb with a product in the form of a heat-resistant glass, in which a ceramic power support with a ceramic centering plug is inserted, and a ceramic power substrate on which a bomb is mounted, is installed on the upper end of the support, while the height from the surface of the hearth to the firing the product should be 0.4-0.6 of the diameter of the bomb, provides a stable rotation of the table and eliminates the obstruction of the product during the firing process.

It was established that the implementation of the tables so that the fired products were located at a height from the hearth equal to 0.4-0.6 of the diameter of the bomb on which they are installed, but not lower than the second row of wall heaters, leads to a more uniform supply of heat flux along the height of the product . In addition, the proposed implementation of the tables allows you to free most of the surface of the hearth under the placement of a more powerful heater, which also leads to the achievement of the stated result.

It was also found that in the proposed furnace, the products are located closer to wall heaters than the prototype, thereby providing a more uniform supply of heat flux to their surface and a more uniform distribution of properties over the volume.

The invention is illustrated by the following drawings:

figure 1 is a schematic vertical section of a furnace; figure 2 is a vertical section of a table for installation and rotation of the product; figure 3 - layout tables with a hexagonal section of the heating chamber (for seven tables).

An electric furnace for firing ceramic products consists of a heating chamber 1, a movable hearth 2, which tightly closes the heating chamber from below by means of a double sand shutter 3, tables 4 are installed on the hearth of the furnace, each of which consists of a heat-resistant glass 5, ceramic power support 6, ceramic centering tube 7, ceramic power substrate 8; bombs 9; the mechanism of raising and lowering the hearth 10; hearth rotation mechanisms in total 11 and each table separately 12; silicon carbide heaters 13 mounted one above the other in a “well” manner along the side walls of the heating chamber; a spiral wire heater 14 located on the hearth.

An electric furnace for firing ceramic products is as follows.

The heating chamber 1 is made so that when lifting the hearth 2 there is a dense closure of the working volume of the electric furnace. Sand shutter 3 provides the required air tightness of the working volume both in a stationary state and during rotation.

Before firing the products, each is set on its own table 4, mounted on the surface of the hearth, while the number of tables is limited only by the dimensions of the fired ceramic products. The rotation of the tables is transmitted through a heat-resistant glass 5, which carries a ceramic power support 6 with a ceramic centering plug 7, and a ceramic power substrate 8 is installed on the upper end of the support, onto which a bomb 9 of a certain diameter is installed, depending on the dimensions of the product. This embodiment of the rotary table provides a stable rotation of the fired product, and the centering of the bombs with the substrate and the substrate with support by means of a centering ceramic plug 7 provide an even supply of heat to the surface of the fired product. Using the mechanism of raising and lowering the hearth 10 under rises and closes the heating chamber. The hearth rotation mechanism 11 is turned on, and the rotation mechanism of each individual table 12 is automatically activated, the rotation from which is transmitted to the heat-resistant glass 5. Voltage is applied to silicon carbide heaters 13 located on the side surface of the heating chamber and to the spiral wire heater 14 located on the hearth . After completion of the heat treatment mode, it is lowered and the calcined products are removed.

The effectiveness of the invention is illustrated by the presented example.

Example

A batch of 7 large-sized complex-shaped products (product height 650 mm, base diameter 250 mm) of the nose dielectric cone type of an aircraft was molded from the same slip of lithium aluminum silicate glass.

Product No. 1 was fired in a furnace similar to the prototype, according to the following mode: drying the shell at a temperature of 200 ° C for 2 hours; step firing at a rate of temperature rise in the furnace of 60 ° C / hour, first to a nucleation temperature of 650 ° C and holding at this temperature for 5 hours, and then to the upper crystallization temperature of 1250 ° C with holding at this temperature for 6 hours, after which inertial cooling of the furnace to a temperature of 250 ° C was carried out.

Products No. 2, 3, 4, 5, 6, 7 were fired in a furnace made according to the proposed solution. Each product was installed on a separate desktop (the installation diagram of the blanks is shown in figure 3), located on the edge of the hearth. This was followed by firing in the above mode.

Samples were made from technological allowances for the calcined products and the basic physical and technical properties were determined, which are presented in the table.

The results presented in the table indicate that the use of the proposed electric furnace can significantly increase the performance of firing furnaces, more than three times reduce the specific energy consumption per unit of output, as well as improve the quality of fired products.

Sources of information

1. Autosvid. USSR No. 853328, cl. F 27 B 9/06, 1979.

2. Malashenko V.P., Rudenko P.V. and others. Electric furnace for firing quartz ceramics. // Glass and ceramics, 1971, No. 8. - S.29-30.

Claims (1)

An electric furnace for firing ceramic products, containing a vertical lined heating chamber, along the side walls of which are installed one above the other “Well” method; silicon carbide heaters, movable under with a double sand shutter, a spiral wire heater located in the grooves, a bushing for installing the product, lifting mechanisms , lowering and rotation of the hearth, characterized in that the heating chamber of the furnace is hexagonal, tables are installed on the hearth of the furnace, with the possibility of rotation around the actual axis, each table is made in the form of a heat-resistant glass, into which a power ceramic support with a ceramic centering plug is inserted, and a ceramic power substrate is installed on the upper end of the support, on which a bomb is installed at a height from the hearth of 0.4-0.6 diameter bombs, but not lower than the second row of wall heaters.

Images