JPS6023780A - Rotary hearth type electric furnace - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotary hearth type electric furnace, and particularly to a rotary hearth type electric furnace suitable for calcination or firing of ceramics.

In general, a rotary hearth type electric furnace used for calcination and firing of ceramics rotates a cylindrical hearth tube that passes through the furnace body at low speed, while at the same time enclosing the hearth tube within the furnace body. External heat that heats the inside of the furnace core tube using metal heaters such as nichrome wire or Kanthal wire arranged concentrically, or heaters with a large number of silicon carbide rod-shaped heating elements arranged in parallel grids around the furnace core tube. Formula structure is adopted. In this type of electric furnace, the furnace core tube is made of a material that does not contaminate the material to be calcined or fired (hereinafter referred to as the object to be fired), such as alumina or zirconia. However, in the case of alumina, the maximum length is 1500 mm, and in the case of zirconia, it is currently difficult to manufacture a tube with a length exceeding 500 mm, and it is almost impossible to use it as a furnace core tube. Therefore, a short furnace core tube must be used, its inclination angle should be small, and it must be rotated at low speed, making it difficult to mass-produce objects to be fired, and the objects to be fired inside must be supplied through the furnace core tube. The amount of heat dissipated to the outside through the furnace wall is greater than the amount of heat, and in order to maintain the hearth temperature at about 100 to 1400'C1, which is necessary for calcination or firing of the object to be fired, a large number of heaters are required. The amount of heat supplied must be increased by using the heater, which increases power consumption, and requires a plurality of heater control circuits, resulting in an expensive control device. Moreover, these factors are reflected in the cost of ceramic products and become a factor in their price rise.

The present invention aims to reduce the power consumption of a rotary hearth type electric furnace and the cost of its control device, and also enables mass production.
The aim is to reduce the cost of ceramic products.

The rotary hearth type electric furnace according to the present invention includes a furnace body, a hearth consisting of a plurality of hearth tubes fixed in the furnace body and connected in series, and a hearth formed of a plurality of hearth tubes fixed in the furnace body and connected in series with each other, and The furnace is characterized by comprising a heater disposed in the furnace, and a drive source for rotationally driving the furnace body.

That is, in order to solve the problem that the furnace core tube cannot be made large in diameter or long due to the material of the layer of the present invention, a plurality of large diameter and/or short furnace core tubes are joined together in the main furnace body to create a long furnace. Forming a bed and fixing it to the furnace body while rotating the furnace body 1
This enables the hearth to rotate integrally with the furnace body, and in order to reduce firing costs, a rod-shaped heater is disposed inside the furnace core tube along its axis line, and the object to be fired is heated by radiation and convection. In addition to direct heating, the furnace body is insulated to reduce heat loss.

Hereinafter, the present invention will be specifically described with reference to the accompanying drawings.

The figure shows an embodiment of a rotary hearth type electric furnace according to the present invention,
For example, la, lb, and Ic have an outer diameter of 160+++m and an inner diameter of 1
The furnace core tubes are made of alumina and have a diameter of 40 mm and a length of 1.000 mm, and are joined in series within the furnace body 3 and fixed to the furnace body 3. The furnace body 3 is made of insulating bricks or ceramic wool, and has a plurality of rotating rollers 2 attached to a frame 4.
A plurality of furnace core tubes 1a integrally formed with the furnace body 3,
The hearth 1 consisting of 1b and lc rotates together with the furnace body 3, but in order to move the objects to be fired that are fed into the hearth 1, the supply port A side is slightly higher than the discharge port E side. The end of the supply port side has a supply port A.
An automatic quantitative feeder 6 for automatically feeding a fixed amount of the object to be fired from the hopper 5 is disposed adjacent to the hopper 5. Further, a chute 7 is provided on the discharge port E side of the hearth, and is suspended below the chute 7. A rod-shaped heater 9 is disposed coaxially with the core tubes 1a, lb, and lc, and is connected to a power source (not shown) through a heater terminal 10 at each end. ing. The material of this rod-shaped heater 9 is selected depending on the purpose of use, but the firing temperature is 10
When the temperature is around 00°C, a heating element material such as nichrome or Kanthal metal wire is used, and when the temperature exceeds 1000°C, a heating element material such as silicon carbide is used. Note that the shapes of the furnace core tube and heater can be arbitrarily changed as necessary.

When using the rotary hearth type electric furnace having the above structure, the hopper 5
An object to be fired, such as a ceramic molded product, is placed in a
A predetermined amount is supplied to the inside of the hearth 1 by an automatic quantitative feeder 6, and the inside of the furnace core tubes 1a, lb, lc, which rotate integrally with the furnace body 3 driven by an electric motor via the rotating roller 2, is connected to the supply port A. From there, move toward discharge port E. In the furnace core tube 1, the object to be fired is first heated to the firing temperature in a preheating zone B, then fired for a predetermined time in a soaking zone C, which is maintained at the firing temperature, and then gradually heated to a predetermined temperature in a cooling zone. It is cooled down, becomes a product, and is discharged from the discharge port E into the container 8. In addition.

The soaking zone is secured by 1/2 to 1/3 of the heater heat generating section.

Example The furnace core tubes 1a and lc have an outer diameter of 160 mm and an inner diameter of 140 mm.
The fin is made of alumina with a length of 1000 mm, and the furnace core tube 1b is made of two zirconia furnace core tubes with an outer diameter of 160 mm, an inner diameter of 140 fl, and a length of 500 + ym, and is made of ceramic wool. It was fixed to the furnace body 3.

The heater 9 is arranged coaxially with the axis of the furnace core tube so that the heat generating part of the heater is in the center of the hearth, and the temperature of the soaking zone C is set to 1400℃.
The ceramic disks were fired at a temperature of The heater 9 has a diameter of 35 mm, a heat generation length of 1500 +++ m, and a total length of 27 m.
It was a rod-shaped silicon carbide heater with a diameter of 0.00 mm, and terminal conductors were spliced to both ends to connect the heater terminals with 10 holes. Comparing the results with the conventional one, the rotary hearth type electric furnace according to the present invention reduced the firing cost (power consumption) to 115%, the manufacturing cost of the control device to 1/3, and the cost of ceramic products. can be reduced by 10-20%, and its processing capacity is 5.
It was more than double that.

As is clear from the above description, according to the present invention, the furnace core tube can be formed to have a diameter and length that are as large as possible for the material, and can be used by joining them together. Even if the length of the pipe becomes shorter than the conventional small diameter and long pipe as a result of making the pipe larger, it is also possible to make a pipe with a larger diameter and longer length as a whole even if it is impossible to make a long pipe due to the material. ,
Therefore, it is possible to increase the rotational speed of the furnace and increase the input amount, thereby significantly increasing the throughput. In addition, the heater is placed in the center of the furnace core tube, and the object to be fired is directly calcined or fired using radiant heat and convection, which reduces heat loss and significantly reduces power consumption. equipment costs can be reduced, and the manufacturing cost of ceramic products can be significantly reduced.

[Brief explanation of the drawing]

The figure is a schematic cross-sectional view of a rotary hearth type mis furnace according to the present invention. 1 - Hearth 1a, lb, lc - Hearth tube, 2 - Rotating roller, 3 - Furnace body, 4 - Frame, 9 - Heater. Patent applicant: Murata Manufacturing Co., Ltd. Representative patent attorney: Aohaku Hoshi and 1 other person

Claims (1)

[Claims] (1) A furnace body rotatably supported by rotating rollers;
a hearth consisting of a plurality of furnace core tubes fixed to the furnace body and connected in series; a heater disposed within the furnace core tube along its axis; and a drive for rotationally driving the furnace body. A rotary hearth type electric furnace consisting of a source and a rotary hearth type electric furnace.