JPH0544050A - Method for ceramic thick film lining on inner wall of tube - Google Patents

Abstract

PURPOSE:To line the inner surface of a tube with a ceramic thick film by use of thermite reaction. CONSTITUTION:The inner surface of a tube is lined with a ceramic thick film by use of thermite reaction. The tube is filled with a mixture powder prepared by adding Al and iron oxide as the reaction agent to SiO2 by 10-40wt.% of the total powder weight. The tube is vertically disposed, to which initial heat source is applied from the upper part so that the thermite reaction proceeds successively from the upper part. Thus, the ceramic as the reaction product is deposited to line the inner wall of the tube.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for lining ceramics on the inner surface of a pipe, and can be advantageously applied to the production of pipes such as coal ash transport pipes of coal-fired boilers, which require heat resistance and wear resistance on the inner surface of the pipe. Regarding the method.

[0002]

2. Description of the Related Art In the conventional method of ceramic lining the inner surface of a tube by utilizing a thermite reaction, a mixed powder of only Al and iron oxide is filled in the tube and the tube is erected vertically and an initial heat source is applied from the upper part to the thermite. The reaction was started and allowed to proceed.

[0003]

According to the conventional method, the thickness of the ceramic layer lined on the inner surface of the pipe is about 2 to 3 mm, but the thickness of 5 mm or more is required for the use where abrasion resistance and corrosion resistance are required. Was requested. That is, the thicker the film, the longer the life will be, even if abrasion or corrosion occurs.

The film thickness of the lining is determined by the reaction rate, and in the conventional method, the reaction rate is about 300 mm / mi.
n is fast, the molten Al ₂ O ₃ formed by the heat of reaction is cooled by the tube wall and solidified for a short time,
That is, the formed film thickness was limited.

In view of the above-mentioned state of the art, the present invention aims to provide a method capable of lining a ceramic having a large film thickness in a tube.

[0006]

According to the present invention, when the ceramic layer is lined on the inner surface of the tube by utilizing the thermite reaction, Al and iron oxide powders are used as reactants and SiO ₂ powder is 10 to 40% of the total weight of the powder. After filling the inside of the tube with a mixture of 100% by weight, the tube is erected vertically and an initial heat source is applied from the top to allow the thermite reaction to proceed sequentially from the top, and the reaction product ceramics is lined on the inner surface of the lined tube. Is a method for lining a ceramic thick film on the inner surface of a pipe.

[0007]

The SiO ₂ mixed in the reaction agent does not directly contribute to the thermite reaction, but suppresses the amount of heat generated during the reaction and slows down the progress rate of the reaction. That is, since the thermite reaction occurs in Al and iron oxide,
By mixing ₂ with each other, the weight of Al and iron oxide contributing to the reaction is reduced, and the calorific value is proportional to the weight of the reactant, so S
The more the iO ₂ is mixed, the more the calorific value is suppressed. When the amount of heat generation is suppressed, the progress of the reaction is transmitted by heat transfer, so the heat transfer rate becomes slower and the reaction progress rate becomes slower.

[0008] The present invention in the lining process is in the state in which Al ₂ O ₃ and Fe thermite reaction is a reaction product during the course is melted by the heat of reaction, high Al ₂ O ₃ melting point of the melt The portion cooled to the melting point or lower by the pipe wall becomes a film.However, if the reaction progressing speed is slow, the residence time of the melt becomes long and the cooling time at the pipe wall becomes long, that is, the solidified layer forms. Get thicker. Due to such an action, when SiO ₂ is added, the film thickness to be lined becomes thick.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a view showing a state in which the inside of the lined pipe 1 is filled with the reactant 2 of the present invention. The components of the reactants are Al powder, iron oxide powder and SiO ₂ powder. As the iron oxide, one having a composition of Fe ₂ O ₃ , Fe ₃ O ₄ , FeO or the like can be used, and the following thermite reaction occurs respectively. _{2Al + Fe 2 O 3 → Al} 2 O 3 + 2Fe + 840KJ ··· (1) 2Al + 3 / 4Fe 3 O 4 → Al 2 O 3 + 9 / 4Fe + 820KJ ·· (2) 2Al + 3FeO → Al 2 O 3 + 3Fe + 846KJ ··· (3)

The compounding ratio of the reactants was set to the amount ratio shown in the reaction formulas (1) to (3), and SiO ₂ powder was compounded to this in an amount of 10 to 40% of the total weight of the reactants. The content of 10% or more is for realizing the thick film which is a feature of the present invention, and the content of 40% or less is such that when more SiO ₂ is mixed, the amounts of Al and iron oxide contributing to the reaction are increased. This is because the amount of heat is reduced and the calorific value is insufficient to stop the reaction.

The lined pipe 1 thus prepared is suspended.
Stand upright and apply an initial heat source from the top with a gas burner etc.
Then, as shown in Fig. 2, the thermite reaction proceeds in a chain.
It In FIG. 1, Al formed by the reaction₂O₃And Fe
And become a molten state due to the heat of reaction, and due to the difference in specific gravity, molten Al
₂O₃4 is floated on the molten Fe 5. This
High melting point Al₂O₃4 is cooled by the lined pipe 1
Is solidified, Al₂O ₃A film 3 is formed. Reaction is above
The reaction progresses in a chain from the bottom to the bottom, and the reaction is
When reaching the lower end of the inning pipe 1, the reaction residue falls down
And the reaction ends. In that state, as shown in FIG.
Al on the entire inner surface of the tube 1₂O₃The film 3 is formed.

The film thickness obtained by the present invention is shown in Table 1, and it was found that the film thickness can be increased as compared with the conventional method.

[Table 1]

[0013]

According to the present invention, when the ceramic layer is lined on the inner surface of the pipe by utilizing the thermite reaction, 5
It became possible to line thick ceramic layers of mm or more. By increasing the thickness of the film to be lined, for example, when the pipe obtained by the present invention is used for a pipe having abrasion resistance on the inner surface such as a coal ash transport pipe, the effect of extending the life can be obtained. It was

[Brief description of drawings]

FIG. 1 is an explanatory view showing a state in which a reactant is filled in a tube according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a state when the thermite reaction is in progress in one example of the present invention.

FIG. 3 is an explanatory view of a ceramic thick film forming tube manufactured according to an embodiment of the present invention.

Claims (1)

[Claims] 1. When a ceramic layer is lined on the inner surface of a pipe by utilizing a thermite reaction, Al is used as a reaction agent.
And iron oxide powder with SiO ₂ powder 10 to 10% of the total weight of the powder.
After filling a 40% weight mixture inside the tube, the tube is erected vertically and an initial heat source is applied from the top to allow the thermite reaction to proceed sequentially from the top, and the reaction product ceramics is lined on the inner surface of the lined tube. A method for lining a ceramic thick film on a pipe inner surface, which is characterized in that: