JPH0379984A - High heat resistant rotary kiln - Google Patents

Abstract

PURPOSE:To easily and safely bake high purity powder in a reactive gas atmosphere by supporting a high heat resistant material, an inner cylinder and an outer cylinder in a coaxial double structure in a high heat resistant rotary kiln, feeding inert gas, etc., in a space between the inner and outer cylinder, and heating it from the outside of the cylinders. CONSTITUTION:Inner and outer cylinders 1 and 2 of high heat resistant material are formed in a double structure through a predetermined interval, and both ends are coaxially secured to different-diameter gland seals 4 of an inner rotary casing 3. The casing 3 is rotatably supported into a stationary casing 5 fixed to a foundation 7 via ball bearings 6, and sealed for burning gas in the inner cylinder, inert gas between the inner and outer cylinders and the exterior via thrust packings provided at three positions. The inert gas is fed through an inlet nozzle 9 and an outlet nozzle 10, the burning gas guided into the inner cylinder via a supply nozzle 11, and discharged from an outlet nozzle 12. Material powder to be burned is supplied from a supply port 13 into the inner cylinder via a screw feeder 14, moved while burning, and discharged from a discharge port 15. A tubular heating furnace 16 is mounted outside the center of the outer cylinder to indirectly heat a kiln.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a highly heat resistant rotary kiln.

[Prior art]

Rotary kilns are one of the most suitable industrial devices for uniformly high-temperature treatment of large amounts of raw materials, and are widely used for cement pit bottoms, alumina pit bottoms, magnesia pit bottoms, etc. There are various classifications depending on the heating method.

The main parts of the structure are composed of a body, a support device, a rotary drive device, a bottom hole cover at the end of the shaft, and a supply section.

The cylindrical body is made of metal, and the inner surface of the cylinder is generally lined with a refractory material to protect it from high temperatures.

Furthermore, for high-temperature treatment of objects to be treated, it is common to use internal combustion gas produced by blowing hot air or fuel.

(Problem to be solved by the invention) However, when a metal material is used for the cylindrical body, the maximum operating temperature is relatively limited. For example, if the sum of the contents of nickel, chromium, etc. excluding iron in the cylindrical material is 30% or more. Even for heat-resistant alloys, the limit is 1000°C in consideration of corrosion resistance and high-temperature strength.

However, direct blowing of combustion gas or hot air is the most common heating method, but it is not suitable for heat treatment and manufacturing of fine ceramics such as high-purity nitride powder for lining with refractory materials. do not have.

[Means to solve the problem]

The present inventors have conducted extensive research to solve the above problems,
This has led to the completion of the present invention.

That is, the highly heat-resistant rotary kiln of the present invention supports an inner cylinder and an outer cylinder made of highly heat-resistant material in a coaxial double structure, and also allows an inert gas or the like to flow through the space between the inner cylinder and the outer cylinder. It is characterized by a structure that heats from the outside, and has a gland seal structure with different diameters at both ends, and an internal rotating casing that hermetically separates the inner cylinder and outer cylinder and supports them coaxially, and the internal rotating casing is rotatable. It is characterized by having a structure in which both ends are supported and fixed by a fixed casing which is supported by a thrust packing and whose interior is divided into an inner cylinder circulation chamber and an outer cylinder circulation chamber.

In the present invention, airtight oxide-based ceramics such as mullite, aluminum, and zirconia are preferably used for the inner and outer cylinders made of highly heat-resistant materials.In particular, carbon materials other than those mentioned above are used for the inner cylinder. can also be used, as long as it is heat resistant and airtight. In the coaxial double structure of the cylinder and the outer cylinder in the present invention, the gap between them only needs to be about 2 to 10 mm, and the gap is further vented with inert gas, and the inner and outer double cylinders are driven by the same rotating shaft. Ru. The inert gas is not particularly limited as long as it does not interact with the firing atmosphere gas. For example, the most common and economical nitrogen gas such as nitrogen, argon helium, etc. is preferably used.

Next, the inner casing, which supports the inner cylinder and the outer cylinder coaxially, is rotatably supported by a pole bearing with respect to the external fixed casing, and the outer cylinder and the inner cylinder are coaxially attached to the different diameter gland seal parts of the inner casing. Fixed.

The backing material for this different diameter gland seal part can be made of a general heat-resistant material, and the temperature at both ends of the kiln can be maintained at a relatively low level of about 200 to 300 degrees Celsius even during firing operation.
For example, asbestos treated with Teflon or graphite can be sufficiently resistant.

Further, the thrust packing that is fixed to the fixed casing and contacts the inner casing to seal inert gas between the inner cylinder and the outer cylinder is made of the same material as the different diameter gland seal,
Alternatively, heat-resistant rubber can be used, and the inner cylinder circulation chamber and the outer cylinder circulation chamber are cut off, and the firing gas in the inner cylinder is double-sealed from the outside.They are provided at three locations.

The outer casing securely supports the entire kiln on the foundation.

The rotary kiln of the present invention is heated from the outside using a tubular electric heating furnace, a combustion furnace, or the like.

Hereinafter, it will be explained in more detail with reference to the drawings. Fig. 1 shows a cross-sectional view of an embodiment of the highly heat-resistant rotary kiln of the present invention. In Fig. It has a double structure with a gap, and both ends are coaxially fixed to the different diameter gland seal part 4 of the internal rotating casing 3. Internal rotating casing 3 is the base! ! It is rotatably supported by ball bearings 6 in a fixed casing 5 fixed to 7, and thrust packings 8 provided at 3 m locations prevent firing gas in the inner cylinder, inert gas between the inner cylinder and outer cylinder, and against the outside. It is sealed. Inert gas is introduced through nozzle 9
The firing gas flowing through the outlet nozzle 10 is introduced into the inner cylinder through the supply nozzle 11, and the firing raw material powder, which is led out from the outlet nozzle 12, enters the screw feeder 14 through the supply port 13 and is fed into the inner cylinder while being fired. move,
A tubular heating furnace 1G is attached to the outside of the central portion of the outer cylinder, which is taken out from the discharge port 15, and indirectly heats the kiln.The kiln's tilt adjustment device and rotation device are not shown.

(Example〕 The present invention will be explained in more detail with reference to Examples.

Example 1 The rotary kiln shown in Fig. 1 has a double structure consisting of an airtight alumina inner cylinder with an inner diameter of 80 m and a length of 1800 m, and an airtight mullite outer cylinder with a gap of about 3 alIl, and a tubular type silicon carbide. The kiln is heated to 1500°C with an electric furnace as a heating element, the angle of inclination is 3 degrees, and the rotation speed is 0.2 per minute.
Set to rotate, and apply nitrogen gas to the gap between the inner cylinder and outer cylinder.
It was circulated at 1/Hr.

Under the above conditions, the amorphous material of silicon nitride was 30g/Hr, and the ammonia gas was 135Nj! The crystalline silicon nitride was continuously supplied at a rate of /Dr, and crystalline silicon nitride was discharged in '1-NO hours after the start of supply, after which operation was continuously carried out for about 500 hours. During operation, the temperature of the outer casing at both ends of the kiln was measured with a surface thermometer, and it was 181'C.
The ammonia concentration in the nitrogen gas was analyzed by gas chromatography, but no ammonia was detected on either the inlet or outlet sides.

During the 500 hours of continuous operation mentioned above, no equipment troubles occurred at all, and after the operation, the equipment was disassembled and the gaskets etc. were inspected, but no abnormality was found.

The metal in the crystalline silicon nitride obtained above was measured using a high frequency emission spectrometer, but almost no impurities due to the kiln material were detected, and the crystalline silicon nitride was extremely pure.

(Effects of the Invention) According to the present invention, even highly heat-resistant materials, which are considered to have relatively low mechanical strength, can be fully fllffled as a rotary kiln by creating a double structure, and therefore can be heated to extremely high temperatures from the outside. Moreover, the firing treatment of high-purity powder in a reactive gas atmosphere can now be performed easily and safely, which is extremely beneficial to industry.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the highly heat-resistant rotary kiln of the present invention. 1. Inner cylinder, 2. Outer cylinder, 3. Internal rotating casing 4, different diameter gland seal, 5. Fixed casing 6, ball bearing, 7. Basics 8, Thrust Packkin, 9. Inert gas introduction nozzle 10
, inert gas outlet nozzle 11, firing gas introduction nozzle 12, firing gas outlet nozzle

Claims (2)

[Claims] (1) A structure in which an inner cylinder and an outer cylinder made of highly heat-resistant material are supported in a coaxial double structure, and an inert gas or the like is passed through the gap between the inner cylinder and the outer cylinder to heat the cylinder from outside. This is a highly heat-resistant rotary kiln. (2) An internal rotating casing with gland seals of different diameters at both ends, the inner and outer cylinders are airtightly separated and coaxially supported, and the internal rotating casing is supported rotatably and is internally sealed with thrust packing. 2. The highly heat-resistant rotary kiln according to claim 1, wherein both ends are supported and fixed by a fixed casing divided into a cylinder circulation chamber and an outer cylinder circulation chamber.