JPH03263586A - Bulkhead plate for indirect heating type rotary furnace - Google Patents

Abstract

PURPOSE:To prevent damage upon reducing the pellet of chrome ore containing carbon reducing agent and elongate the life of the title furnace by a method wherein bulkhead plates, made of carbon, zirconia or the like, are provided at the side of a reaction chamber while the bulkhead plates, made of silicon carbide or the like, are provided at the side of a combustion chamber. CONSTITUTION:Ceramics bulkheads are arranged in the shape of a hexahedron to constitute a reaction chamber 10 while carbon bulkhead plates 17 are used at the side of the reaction chamber 16 and silicon carbide bulkhead plates 18 are used at the side of a combustion chamber 3. Supporting bricks 14 are arranged at the circumferential ends of respective surfaces of the carbon bulkheads 17 and the silicon carbide bulkheads 18 while steps 20 are provided at the top 19 of the supporting bricks 14 and the circumferential ends of the bulkhead plates 17, 18 are fitted into the steps. The mating surfaces between the bulkhead plates 17, 18 are bonded by silicon carbide mortar and the deterioration of heat transfer is prevented by air gaps between the mating surfaces. According to this constitution, an article 12 to be treated is heated and reduced indirectly under a condition that the article 12 is intercepted from the combustion chamber 3 while being passed through a furnace hearth 16 whereby products, of which the reducing rate of 95% or more of the chrome ore is maintained, can be obtained stably for a long period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement of a partition plate that isolates a reaction chamber and a combustion chamber of an indirectly heated rotary furnace.

[Conventional technology]

Generally, rotary furnaces dry powder or granular materials.
It is used to perform heat treatments such as sintering, synthesis, or reduction. An inexpensive solid, liquid, or gaseous fuel is used as a heat source for heating, and the object to be fired is directly or indirectly heated by combustion gas from a burner.

A method in which the object to be fired is directly heated with combustion gas is called an internal heating method, and is a method in which a finished product is obtained by heating in an atmospheric atmosphere.

Thermal efficiency is good because combustion energy is used as is.

Next, a method in which the object to be fired and the combustion gas are heated indirectly through a partition wall without direct contact is called the external heating method, which heats the object to be fired without causing it to react with oxygen, carbon dioxide, etc. in the combustion gas. It's a method.

For example, when reducing ores by heating, a method is used in which the ores are isolated from high-temperature combustion gas for heating and heated in a reducing atmosphere such as carbon monoxide gas.

Generally, in such a rotary furnace, the cylindrical furnace body is placed on its side at a slight slope from horizontal, and the cylindrical furnace body is slowly rotated continuously in the same direction, and the material to be processed is passed through the furnace. It is used by heating it while heating it.

In the case of an external heating type structure, heat-resistant steel can be used for the partition wall that separates the combustion gas and the object to be fired if the heat treatment temperature is about 800°C or less, so it is possible to obtain a long, long-diameter integral cylinder. A structure in which a heating chamber fixed to the outside of this heat-resistant steel cylinder is provided and heat treatment is performed while only the heat-resistant steel cylindrical furnace body is rotated is often used.

If the heat treatment temperature is about 800° C. or higher and a heat-resistant steel partition cannot be used, a ceramic partition is required, but it is difficult to obtain a long, long-diameter cylindrical ceramic partition by itself. For this reason, the present inventor previously proposed a structure as shown in Figs. 2 and 3 for an external heating rotary furnace that requires heat treatment at a high temperature of approximately 800°C or higher (
Japanese Patent Publication No. 64-63781). That is, the furnace body 4 is provided with a combustion chamber 3 configured by a lining refractory 2 and a ceramic partition wall 11 inside a cylindrical steel shell 1.
It is installed on a receiving roller 9 together with a drive device 8 with an inclination such that the inlet 6 side is slightly higher than horizontal with respect to the output lower side with respect to the axis 5 of the roller. A burner lO is attached to the combustion chamber 3 and rotates slowly together with the furnace body 4.

The combustion gas from the burner 10 is transferred to the lining refractory 2 of the combustion chamber 3.
Then, the ceramic partition wall 11 is heated, and the object to be treated 12 is indirectly heat-treated via the ceramic partition wall 11 . Second
In the example shown in the figure, the reaction chamber is arranged in the center and the combustion chamber is arranged in the outer periphery, but the reaction chamber and the combustion chamber may be arranged oppositely.

Next, the structure of the refractory lining 2 and the ceramic partition wall 11 of the furnace main body 4 will be described by way of example. In other words, in Fig. 2, the inside of the cylindrical steel shell 1 is lined with refractory bricks 13, but the height of the refractory bricks 13 is not uniform and varies, and supporting refractory bricks 14 are placed at appropriate intervals. has been done. The supporting refractory bricks 14 are for supporting the ceramic partition plate 15. With this configuration, the reaction chamber 1G is made up of a polyhedron surrounded by the ceramic partition plate 15 and the supporting refractory bricks I4.
A plurality of combustion chambers 3 surrounded by refractory bricks 13, supporting refractory bricks 14, and ceramic partition plates 15 are constructed on the outer periphery.

With this structure, the reaction chamber 16, the combustion chamber 3, and the burner 10 rotate together to indirectly heat-treat the object 12 passing through the reaction chamber 16.

[Problems to be Solved by the Invention] Conventionally, in an externally heated rotary furnace having a structure as shown in FIG.
A material with high thermal conductivity and high hot strength, ie, charcoal-silicon (SJC) material, was mainly used in the form of a plate. However, when used for the reduction of chromium ore pellets containing a carbonaceous ring agent, the charcoal-silicon ceramic partition plate 15 will reduce the chromium ore in the vicinity of the hottest skin near the burner IO of the reaction chamber 16 at about 1450°C. It was difficult to operate for a long period of time because it gradually wore out due to a reduction reaction with metals produced by reducing chromium ore.

If the ceramic partition plate 15 is damaged, combustion gas will flow into the reaction chamber 16, making it impossible to maintain a reducing atmosphere.
The external heating rotary furnace will stop functioning. In addition, since the furnace body structure is complicated, the furnace repair period and cost are both longer than that of an internal heating rotary furnace.

For this reason, there is a strong desire for measures to extend the life of the ceramic partition plate 15 by preventing damage to it. It should be noted that parts other than the hottest skin near the burner IO are rarely damaged and are relatively stable.

[Means for Solving the Problems] The present invention provides a ceramic partition plate 15 that isolates a reaction chamber 16 and a combustion chamber 3 of an externally heated rotary furnace used at temperatures of 800° C. or higher.
The shape and material of the chromium ore pellets are improved to prevent damage during reduction of chromium ore pellets containing a carbonaceous reducing agent and extend the life of the chromium ore pellets.

Conventional silicon carbide ceramic partition plate 1 shown in Fig. 3
Regarding the damage to No. 5, the wear on the surface on the reaction chamber 16 side is significantly greater than the state of the damaged object, and the wear on the surface on the combustion chamber 3 side is extremely small. Table 1 shows a comparison of the usage conditions between the reaction chamber 16 side and the combustion chamber 3 side.

In other words, the usage conditions of the ceramic partition plate 15 are different between the reaction chamber 16 side and the combustion material 3 side. On the side of the reaction chamber 1B, the ceramic partition plate 15 made of silicon carbide undergoes the formation of composite carbide in a high-temperature carbon oxide atmosphere in the presence of a carbonaceous reducing agent, a chromium ore pellet, and objects 12 to be treated such as metals produced by reduction. The strength of the surface decreases, and at the same time, the object 12 to be treated is worn and damaged due to movement as the furnace body rotates. On the side of the combustion chamber 3, an oxide film is formed on the surface under a high temperature oxidizing combustion gas atmosphere, and this protects the inside, thereby preventing a decrease in strength and making it stable.

In this invention, as shown in FIG. 1, the materials of the partition plates on the reaction chamber 16 side and on the combustion chamber 3 side are adapted to suit the respective usage conditions. In other words, the quality characteristics commonly required for the reaction chamber 16 side and the combustion chamber 3 side under the usage conditions shown in Table 1 are 1.
It has heat resistance at temperatures above 550°C, structural strength during heat resistance, and high thermal conductivity due to heat treatment efficiency. In addition, on the reaction chamber I6 side, reducing atmosphere resistance and abrasion resistance are
On the combustion chamber 3 side, resistance to oxidation and resistance to rapid heating and rapid cooling are required.

For this reason, the partition plate was made into a two-layered shape. The material is the reaction chamber l
On the B side, the partition plate 17 is made of a material such as carbonaceous zirconia or fused alumina, which is safe in a high-temperature reducing atmosphere, has high hot strength, high thermal conductivity, and has high abrasion resistance. Next, on the combustion chamber 3 side, a partition plate 18 made of silicon carbide or fused alumina, which is stable in a high-temperature combustion gas atmosphere and has high hot strength and thermal conductivity, is made of the same material as the conventional one.

The material on the reaction side may be selected as appropriate depending on the substance to be treated. On the combustion chamber side, charcoal-fired silicon and fused alumina have strong resistance against combustion gas, but silicon carbide is better. Fused alumina has a certain degree of resistance both on the reaction chamber side and on the combustion chamber side.

[For production]

As explained above, the ceramic partition plate 15, which has conventionally been a single-layer plate made of silicon carbide, is exposed to the reducing atmosphere generated by the workpiece 12 at high temperature in the reaction chamber IB and the high-temperature combustion gas generated by combustion of fuel in the combustion chamber 3. As a ceramic partition plate made of a material that can withstand the atmosphere, that is, a two-layer partition plate consisting of a carbon partition plate 17 and a silicon carbide partition plate 18, it is possible to correspond to the respective usage conditions,
This extends the life of the partition plate compared to the conventional one.

〔Example〕

Reaction chamber 1B of an external heating rotary furnace with a combustion treatment temperature of 1450°C, which is equipped with a combustion chamber 6 in a furnace body with an outer diameter of 2.5 ms and a total length of 10 m.
The conventional ceramic partition plate 1 is located in the approximately 2 m section from the lower position of the heat-treated material outlet toward the inlet 6, that is, in the highest temperature section.
The present invention was applied to a range where 5 is easily damaged, and good results were obtained. The remaining approximately 8m area from this part in the 6 directions of the entrance remained the same as the conventional materials and structure.

The structure in which this invention is implemented is shown in FIG.
The ceramic partition wall 6 was made into a hexahedron, and a carbonaceous partition plate 17 was used on the reaction chamber 16 side, and a carbonaceous silicon partition plate 18 was used on the combustion chamber 3 side. The shape was a plate, and the length was 500 mm, the width was about 500 mm, and the thickness was made of carbon material of 40 mm and silicon carbide material of 60 II 11.

These carbon partition plates 17, silicon carbide partition plates 18 (
Support bricks 14 are arranged at the circumferential ends of each surface (hereinafter referred to as partition plates 17 and 18), and a step 20 is provided at the top 19 of the support bricks 14, and the circumferential ends of the partition plates 17 and 18 are Insert. Due to the slope of the circumferential ends of the partition plates 17.18, this structure does not allow the partition plates 17.18 to come off even if transferred. During this assembly, ceramic fiber thin plates are inserted into the 20 steps of the support bricks 14 to form the partition wall plate 17. It is designed to absorb the thermal expansion of is in the circumferential direction. Additionally, the overlapping surfaces of the partition plates 17 and 18 were adhered with silicon carbide mortar to prevent a decrease in heat transfer due to voids between the joining surfaces. Further, in the axial direction, the connecting joints of the partition plates 17 and 18 are arranged so as not to be in the same position, thereby preventing combustion gas from leaking from the combustion chamber 3 to the core chamber 16.

By carrying out this invention, the object to be treated 12 is indirectly heated and reduced while passing through the furnace core chamber 1B while being isolated from the combustion chamber 3, resulting in a product that maintains a reduction rate of 95% or more of chromium ore. can now be obtained stably over a long period of time. In other words, conventional burner lO after approximately 3 months of operation.
The partition plate 15 was damaged at the highest temperature point near the
As a result of adopting this invention, it was possible to increase the lifespan to more than 6 months.

As a result, the number of restoration works was also reduced, making it possible to save on construction costs and increase production by more than 15%.

In the embodiment of the present invention, in order to isolate the reaction chamber 16 and the combustion chamber 3, a carbonaceous partition plate 17 and a silicon carbide partition plate 1 are used.
8 was bonded with silicon carbide mortar, but the surface of each partition plate may be coated with a highly reduction-resistant or oxidation-resistant material by thermal spraying, or lined with a monolithic refractory. It is also possible to make it into a single piece using the method described below. Further, the reaction chamber 16 may be a polyhedron other than a hexahedron.

Next, in the description of this invention, the carbonaceous partition plate 17 was used on the reaction chamber 16 side, but it may also be used as an electroformed bulky material such as alumina or zircon, which is resistant to reducing atmospheres and other conditions. .

Further, in this invention, the present invention is applied to a predetermined range from before the burner, but by applying the invention to the entire length of the furnace core chamber, further extension of the life can be expected.

[Brief explanation of drawings]

Fig. 1 is a sectional view perpendicular to the rotation axis showing an example of the partition plate structure according to the present invention, Fig. 2 is a sectional view parallel to the rotation axis showing an example of the conventional structure of an external heating rotary furnace, and Fig. 3 is a cross-sectional view perpendicular to the rotation axis, showing an example of a conventional partition plate structure.

Claims (1)

[Claims] 1) A partition plate used in an indirect heating rotary furnace having a reaction chamber and a combustion chamber that are shielded from each other, wherein the reaction chamber side is made of reduction-resistant ceramic and the combustion chamber side is made of oxidation-resistant ceramic. A partition plate characterized by having a two-layer structure of a different quality ceramic. 2) The partition plate according to claim 1, wherein the reduction-resistant ceramic is one of carbon, zirconia, and fused alumina, and the oxidizing ceramic is silicon carbide. 3) The partition plate according to claim 1, wherein the reduction-resistant ceramic is carbon or zirconia, and the oxidation-resistant ceramic is fused alumina.