JPS61197407A - Method for reducing inorganic oxide and apparatus therefor - Google Patents

Abstract

PURPOSE:To carry out the reduction of inorganic oxide powder in a manner to enable the stable production of uniform product for a long period, by supplying an inorganic oxide powder to the heating zone of a stationary cylindrical reducing furnace, and heating at a temperature below the melting point in a reducing gas atmosphere. CONSTITUTION:The raw material to be reduced is charged to the receiving hopper 1 by opening the valve 2 deg., and the air in the hopper 1 is purged with N2 after closing the valve 2 deg.. The valve 2' is opened to transfer the raw material to the feeding hopper 1', and to charge at a constant rate by the constant-rate feeder 3 to the reducing calcination furnace 14. The reducing gas is supplied to the furnace through the inlet 10. The raw material is pushed into the reducing and calcining zone 6 with the pusher 5 driven by a piston, and heated with the external heating furnace 7 to a temperature below the melting point of the raw material. The reduced and calcined product is pushed with the pusher 5 into the product tank 8. The product having uniform degree of reduction can be produced by repeating the above procedures. The adhesion of the raw material to the inner wall of the furnace, and the formation of pills can be prevented by this process.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method and apparatus for reducing inorganic oxide powder.

(Prior art and its problems) A method of reducing an inorganic oxide under heating has been conventionally known.

For example, there is a method in which the reducing raw material is reduced at high temperature in a reducing gas atmosphere using a rotary furnace. However, fibrous materials that tend to agglomerate the reduced raw materials have the disadvantage that they are agglomerated by rotation and are not reduced uniformly.

Particularly in the case of an external heat type furnace, reduced raw materials and reduced products adhere to the inner wall of the furnace, forming a so-called "ring" and making it impossible to obtain uniform reduced products.

(Means for Solving the Problems) The present invention provides a method for efficiently obtaining a uniform reduced product by preventing agglomeration from occurring and from adhering to the inner wall of a furnace in a method for reducing inorganic oxides. As a result of conducting research on the above, the present invention was arrived at.

The first aspect of the present invention is to supply an inorganic oxide powder to a non-rotating cylindrical reduction furnace, place it in the heating area of the inorganic oxide powder, and then reduce the inorganic oxide powder under a reducing gas atmosphere. A second invention is a method for reducing an inorganic oxide, which is characterized by heating at a temperature below the melting point of # Nakasu: A method for reducing an inorganic oxide, which comprises placing the inorganic oxide in its heating area and then heating the inorganic oxide at a temperature below the melting point of the inorganic oxide in a non-oxidizing gas atmosphere. An apparatus for heating and reducing a powder in a reducing gas atmosphere or a mixture powder of an inorganic oxide and a reducing agent in a non-oxidizing gas atmosphere, which is equipped with an outside air blocking means for receiving the raw material powder and a nitrogen purging means. A storage device for the raw material of the mold and a device connected to the storage device for quantitatively supplying the raw material to the reduction furnace are provided at the upper end of the externally heated non-rotating horizontal cylindrical reduction furnace, and furthermore, the position of the end is provided. A piston-type pushing device is provided at the tip of which has a cross section approximately equal to the inner diameter of the reduction furnace for charging the quantitatively supplied raw material into the heating area of the furnace and discharging the reduced product, and at the other end of the reduction furnace. This is an inorganic oxide reduction device consisting of a device with a cooling and storage function for the reduced product in the lower part.

The present invention will be further explained in detail below.

The first invention of the present invention is a method of reducing an inorganic oxide powder by heating it at a temperature below the melting point in a reducing gas atmosphere, and the second invention is a method of reducing an inorganic oxide powder by heating it at a temperature below the melting point. This invention relates to an apparatus used in a method of reducing by heating at a temperature below the melting point in a non-oxidizing gas atmosphere.

The inorganic oxide powder used in the present invention may be any known inorganic oxide powder, and in particular, the reduction temperature is such that when reduced in a rotary reduction furnace, it produces "pills" or forms "a ring" on the furnace wall. Specific examples of inorganic oxides with similar melting points include powders such as potassium titanate and titanium oxide.

In the first invention, an inorganic oxide powder is used as a raw material, which is placed in an externally heated non-rotating horizontal cylindrical reduction furnace without being pressurized, and is heated and reduced at a temperature below the melting point in a reducing gas atmosphere. Specific examples of the reducing gas include gases such as hydrogen and hydrocarbons, and in addition to using one or more of these gases, a gas such as nitrogen may be added as a diluent gas.

The second invention is a method of adding a reducing agent to the inorganic oxide powder in the first invention and carrying out thermal reduction after disembarkation in a non-oxidizing gas atmosphere. Specific examples of the reducing agent include carbon such as carbon black, calcium carbide, etc. Carbides such as carbides, and lower oxides such as bitumen can be found. In this case, if the reducing agent is contained in a desired amount, thermal reduction is carried out in a non-oxidizing atmosphere, but depending on the case, thermal reduction may be further carried out in a reducing gas atmosphere. The amount of reducing agent added is sufficient as long as it reduces the inorganic oxide.

Next, the device of the sixth invention will be explained.

The apparatus of the present invention is an externally heated non-rotating horizontal cylindrical reduction furnace, which is equipped with the raw material storage device (hereinafter referred to as hopper) and a fixed-quantity supply device connected thereto at the upper end of the furnace. is supplied to the reduction furnace, and the raw material supplied into the furnace is charged into the heating area by a piston-type push plate and reduced, and then it is stored at the bottom of the other end of the furnace with cooling and storage functions. is configured to be received by a device having a

Further, the apparatus will be explained with reference to the drawings. The drawings are cross-sectional views illustrating a reduction furnace that is an embodiment of the present invention.

The receiving hopper 1 for the reduced raw material has a structure that can be opened and closed to the outside air by a valve holder. The hopper 1' is moved through the valve 2' to the reducing furnace 1 in accordance with the operation of the push plate 5 of the piston-type pushing device.
4.It is designed to be discharged into the inside.

The piston-type pushing device consists of a piston rod 4, a pushing plate 5, and a piston case 15. The piston is heated to the desired temperature by the transfer furnace 7, as shown at positions 5.5' and 5'' on the push plate.The heat source may be an electric heating element, gas, or liquid fuel. It's okay.

The reduced product is stored in product tank 8. This tank has an air-cooled or water-cooled structure. It is also equipped with a device that can replace the inside of the tank with inert gas such as N2. If the reducing agent is a gas or liquid as in the first invention, the inlet pipe 10
An exhaust purge pipe 9 is required.

To further explain this, open valve 2° and close valve 2' (if flammable gas is mixed in hopper 1, replace and purge the combustible gas with an inert gas, such as N2), and then remove the reducing raw material. and when completed, close valve 2.
Close and purge the air with N2. Next, open valve 2' and put 10 pieces into the hopper. Next, the reduced raw material introduced by the piston-type pushing device is sent to the reduction firing zone 6. The number of times of feeding is determined based on the relationship between the amount of feed and the capacity of the firing zone. The temperature of the reduction firing zone 6 may be any temperature necessary for the reduction raw material. If the material is heat-resistant steel, the maximum temperature of the furnace is 100
If it is made of heat-resistant ceramic of about 0'C, the temperature can be further increased. Therefore, it is natural that the temperature to be adjusted should match the reduction temperature of the reducing raw material.

Further, the reduction time is determined in relation to the difficulty of reducing the reducing raw material and the reduction temperature. The stroke length of the piston rod when sending the reducing raw material to the reducing firing zone is configured to be changeable, and the raw materials are sequentially charged from before the reducing firing zone. When the charging of the reducing raw material into the reduction firing zone is completed, the operation of the piston is stopped, the push plate returns to the original position 5, and remains stopped until the reduction firing time has elapsed. The storage feeder 3 can perform intermittent operation in conjunction with the operation of the piston.

When the reduction firing is completed, the piston pushing device operates again.
The reduced product in the reduction firing zone 6 is of the same type as the inner wall of the product tank 8, that is, it has the same disk structure as the furnace shape.
When passing through the furnace, the material to be treated that has adhered to the inner wall of the furnace is scraped off to prevent the formation of an adhesion layer. If the inside of the furnace cannot be cleaned and an anti-adhesion layer is formed on the inner wall of the furnace, heat transfer from the external heating furnace 7 to the reduction firing zone 6 is also prevented. Therefore, it is necessary to further increase the temperature of the external heating furnace 7 in order to maintain the temperature of the reduction firing zone at a specified level, and increasing the temperature promotes the formation of an adhesion layer and reduces heat transfer. Such a vicious cycle often makes work impossible, but the present invention solves this problem.

Furthermore, since the reduction firing furnace 14 of the present invention is of a non-rotating, stationary type, it has the advantage of fewer moving parts and less seal leakage. In conventional reduction furnaces, various types of seals are used to keep the inside of the furnace in a reducing atmosphere, which allows for reliable sealing and safe operation.

In particular, when the reducing raw material is inorganic fiber, etc., it easily becomes pilled (agglomerate) when subjected to rolling action, impairing heat transfer.
Since the reduction furnace of the present invention is a non-pressurized stationary type, the raw material is not subjected to rotational action and is processed in the normal state at the time of charging, allowing efficient reduction. Furthermore, to describe the features of the furnace of the present invention, the reduction firing time can be strictly controlled by the operation of the piston, and unlike other continuous furnaces, there is no rapid flow or slow flow of the reduced material. Since no such phenomenon occurs, a uniform reduced product can be obtained.

The cylindrical shape of the furnace advantageously guides deformation due to heat and piston operation, and facilitates replacement of furnace materials.

Next, the present invention will be described in detail with reference to examples.

Example 1 White potassium titanate fiber (trade name 1-Tl5M0-D J manufactured by Otsuka Chemical Industries, Ltd., from which pilling had been removed in advance) was used as the reducing raw material.The reducing apparatus was a furnace having the structure shown in the drawing. The inner diameter was 3 () Q mm, and the length of the reduction firing zone was 650 mm.

First, the reducing raw material was put into hopper 1 at 9:50, and after evacuating the outside air with a valve, N2 was introduced to expel the air and completely replace it. Next, 15 # of the reduced raw material was sent to the hopper 1' (the hopper 1', the reduction furnace 14, and the product tank 8 were not contaminated with outside air during operation). Hydrogen was introduced into the reduction firing furnace 14 from the reducing gas supply port 10 . The temperature of the reduction firing zone 6 is controlled by an external heating furnace 7 using electric heat.
The temperature was adjusted to 900'C. The potassium titanate fiber in hopper 1 is fed by constant feeder 3 to 2 JC.
9. Supplied into the furnace, constant supply +! 3 was stopped. Next, the potassium titanate fibers are reduced and fired in a firing zone 6 using a piston device.
I sent it to the second half of . Furthermore, the second reduced raw material was sent to the first half in the same manner. Note that the equal weight of the firing zone was 4 to 4 grams of potassium titanate fiber. Immediately after the charging was completed, the temperature of the reduction/calcination zone 6 decreased by 8°C, but by adjusting the temperature of the external heat furnace 7, it recovered to the predetermined temperature of 900°C in about 5 minutes. After charging the potassium titanate fibers, the fibers were reduced and fired in a hydrogen stream for 20 minutes, and the piston-type pushing device was operated again to move the reduced product from the firing zone to the product tank, where it was cooled. The cooled product was dark blue and had no pilling at all.

Potassium titanate fibers are known to have strong infrared reflectivity, and if a pill is present, heat transfer will be insufficient inside the pill, and the color will remain white or turn pale blue, and the purple-dark blue color of the outer layer will deteriorate. However, according to the present invention, the product exhibited a uniform dark blue color, and when observed under a microscope, it showed uniform properties without deformation of the fiber shape.

Example 2 15 parts by weight of acetylene black were uniformly mixed with 100 parts by weight of the potassium titanate fiber used in Example 1. Acetylene black was used as a reducing agent. As in Example 1, 4 kg of the mixture was charged into the reduction firing zone, and the mixture was reduced and fired in a nitrogen stream at a reduction firing temperature of 850°C and a reduction time of 25 minutes. After cooling the product in a tank, it was taken out and residual carbon was removed using kerosene to investigate the reduction status. The product was as good as Example 1.

Example 6 Fuji Titanium Co., Ltd.! ! Anatase-type titanium oxide (trade name) TA-100J (5 kg) was charged in the same manner as in Example 1 into a reduction firing zone, and was heated in an air stream containing equal amounts of hydrogen gas as a reducing agent and nitrogen gas as a reducing agent. The reduction temperature was set to 7500 G. After reduction and cooling, the titanium oxide was taken out and observed. The color was pale blue, and under the microscope, there was almost no crystal growth. Fine particles of semiconducting hihi titanium were obtained as F4.The conductivity was measured using a method of measuring electrical resistance of conductive oil black, and a value of 1060 was obtained.

(Effects of the present invention) According to the present invention, compared to other reducing devices, there are extremely few movable parts on the groove structure of the device, and even the town a part takatsuba moves intermittently, so it is difficult to maintain the reducing atmosphere and pass it into the outside air. It is easy to prevent reducing gas leakage, and the equipment is easy to operate.The most important thing is that the raw material is completely prevented from sticking to the furnace inner wall, and uniform products can be stably produced over a long period of time. -Also, even if the raw material is a fibrous material that is prone to pilling, it can prevent pilling and produce a product with a uniform degree of reduction.

[Brief explanation of drawings]

The drawing is a top view illustrating an apparatus used in an embodiment of the present invention. Code 1...Raw material receiving hopper 1'...Raw material supply hopper 2.2°, 2'...Shutoff valve 3...Raw material quantitative feeder 4...Piston rond 5, etc., 5... Lu, cheat scale 6...Reduction firing zone 7...External heating furnace 8...Product tank 9...Exhaust hole 10...Reducing gas supply port 11.12...Gas seal device 13... 1 piece of raw material return hopper... Reduced fried rice

Claims (3)

[Claims] (1) Supplying inorganic oxide powder to a non-rotating cylindrical reduction furnace,
A method for reducing an inorganic oxide, the method comprising heating the inorganic oxide at a temperature below the melting point of the inorganic oxide in a reducing gas atmosphere after placing the inorganic oxide in the heating region. (2) A mixture of inorganic oxide powder and a reducing agent is supplied to a non-rotating cylindrical reduction furnace, placed in the heating area, and then heated at a temperature below the melting point of the inorganic oxide in a non-oxidizing gas atmosphere. A method for reducing an inorganic oxide, characterized by: (3) In an apparatus for heating and reducing an inorganic oxide powder under a reducing gas atmosphere or a mixture powder of an inorganic oxide and a reducing agent under a non-oxidizing gas atmosphere, an outside air blocking means for receiving the raw material powder and nitrogen substitution are provided. a closed type storage device for the raw material provided with a means, and a device connected to the storage device for quantitatively supplying the raw material to the reduction furnace; Further, a piston-type pushing device is provided at the end thereof, the tip of which has a cross section approximately equal to the inner diameter of the reduction furnace, which charges the quantitatively supplied raw material into the heating area of the furnace and discharges the reduced product. An inorganic oxide reduction device consisting of a device equipped with a cooling and storage function for the reduced product at the bottom of the other end of the reduction furnace.