JPH02160896A - Method for preventing adhesion of carbon to coke oven wall surface - Google Patents

Abstract

PURPOSE:To form a thin strong coating layer on the surface of the central wall of a coke oven to thereby prevent the adhesion of carbon to the wall surface by flame spraying a specified flame spraying material with a plasma jet using an Ar gas as main working gas. CONSTITUTION:A mixture of 80-20wt.% fine SiO2 or Cr2O3 powder having a particle diameter of 0.1-50mum and 20-80wt.% Si and/or Cr, both having a particle diameter of 50-10mum, is granulated to give a flame spraying material having a particle diameter of 50-200mum. This material is sprayed on the surface of the central wall of a coke oven by operating a plasma jet using an Ar gas having an He to Ar ratio of 5:100 or less as main working gas at a travelling speed of 10-30m/min, thus forming a coating layer having a thickness of 5mm or less.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for preventing the adhesion of carbon such as tar produced during carbonization on the inner wall surface of a coke oven, and in particular to a method for preventing carbon adhesion on the inner wall surface of the coke oven. It is characterized by forming a thin and strong coating layer.

(Prior Art) In a coke oven, a large amount of hydrocarbon liquids and gases, mainly tar, are produced during the carbonization process of coal. These particles enter the gaps in the furnace wall inside the carbonization chamber and the open pores of the furnace body members, forming a strong carbon adhesion layer, often causing operational troubles such as kiln unloading abnormalities. For this reason, in daily operations, air or oxygen gas is blown in to burn off the kiln, but with this method the work area is limited to the vicinity of the kiln mouth. For this reason, operations are periodically suspended for the entire area, including the center of the furnace, and the furnace is left in an empty state to burn off the area. However, the burn-off work itself is a severe and high-temperature work, and the combustion heat during burn-off brings about local high heat conditions to the bricks of the furnace body, which is a remote cause of damage to the furnace body.

In response to this situation, various studies have been made on bricks and methods for treating brick surfaces to which carbon is difficult to adhere. That is, for example, there are bricks made by applying a glaze to fired bricks and heat-treated as in JP-A No. 59-174585, or bricks made by applying a glaze at the base stage and firing as shown in JP-A-63-236783.

These are designed to eliminate air permeability on the surface of the bricks and create a smooth surface to prevent adhesion. All of these are designed to protect the area near the kiln mouth, especially the inner wall of the furnace lid, from thermal shock caused by the opening and closing of the furnace lid. The material is made with consideration.

On the other hand, as a method for treating the entire area of the carbonization chamber including the central portion, there is a method of spraying an inorganic binder and a finely powdered refractory into the furnace (for example, Japanese Utility Model Publication No. 55-4276).

This is a method of clogging the joints in the furnace wall with powder.
In terms of covering the brick surface, the adhesive strength is poor and the reliability is poor. Furthermore, Japanese Utility Model Application Publication No. 54-19243 proposes that the carbon adhesion rate can be significantly reduced by providing a glass coating layer with an apparent porosity of 5% or less. However, high temperature (9
In the center of the furnace where temperature fluctuations are small (00 to 1100°C), the so-called glass whose main component is 5iOtA1zOff-CaO easily devitrifies and flakes off, and its melting point is easily lowered by alkali vapor in the carbonization gas. The life of the film itself is short.

By the way, -M has a low porosity oxide coating layer (hereinafter referred to as "skin").
Thermal spraying, which is a method for obtaining a LiO □ and MgO
It is similar to the above-mentioned glaze in that it is a high silicic acid material containing glazes such as glazes. That is, since the heat source is a combustion flame and the material must have a low melting temperature, the fire resistance is poor in the central part of the furnace. In particular, since the main focus is on furnace wall repair, the material particles are coarse (and a thin, smooth film cannot be obtained.The present inventors also disclosed a repair method using plasma in Japanese Patent Laid-Open No. 5E3-49889, etc.). However, the reality is that a film that is fully satisfactory in terms of film smoothness has not been obtained.

Therefore, the present inventors investigated various coating treatments for brick surfaces as a method of coating the entire interior of the coke oven during operation to prevent carbon adhesion, and found that conventional methods or materials,
In other words, coating by coating and baking on brick surfaces, coating by spraying or blowing in a hot state, or diversion of flame spraying results in poor fire resistance and adhesion of the coating, and it is not possible to expect sustained coating reduction. I've come to a conclusion. In addition, conventional coating materials tend to suffer from melting point depression and exhibit an adhesive effect on coke cake, which can easily cause operational troubles.

Therefore, it was found that film thickness adjustment and film smoothness are important.

(Problems to be Solved by the Invention) The following describes the results of arranging the problems that arise when applying the conventional coating method for preventing carbon adhesion to the central part of the furnace and considering countermeasures.

(2) Coating process: The conventional method of coating during the brick manufacturing process is only effective for a certain period of time after the furnace is built, and is not suitable for the coke oven body, which has an oven life of 20 to 30 years. Therefore, the method must be such that it can be coated repeatedly at any necessary location during operation.

Means of O0 coating: Wet spraying and coating methods have poor adhesion. In addition, the flame spraying method is a method of overlaying the wall surface of the kiln opening, and since it is a relatively low melting point material and contains coarse particles, it is easy to overlay overlay, leading to trouble when unloading the kiln. Therefore, the method must have a high melting point and a thin film.

Materials forming the O11 coating: Conventional thermal spray repair materials are highly silicic, but these form highly viscous droplets, resulting in poor coating smoothness. Furthermore, in order to improve adhesion, the running speed of the thermal spray gun is slow, which promotes unevenness of the coating. Therefore, it is necessary to set the material composition and construction conditions to improve the smoothness of the film.

O1 material particles: In order to improve the smoothness of the coating by thermal spraying,
The particles supplied to the thermal spray gun are preferably fine powders, but problems in supplying them to the gun are likely to occur due to differences in specific gravity and humidity. Therefore, there is a need for a method for smoothly supplying fine powder particles.

(2) Coating condition: When coating the central part of the furnace, there is a concern that the extrusion resistance of coke will increase, and the coating must be strictly controlled. Specifically, it is necessary to form a highly adhesive film with a thickness of 5IIl[Il or less, ideally 3M or less.

The present invention has been made in view of the above problems, and
The purpose is to prevent carbon adhesion by coating the wall surface of the central region of the carbonization chamber during operation, and to avoid operational troubles.

Furthermore, the life of the reactor is extended by suppressing damage to the reactor body. Therefore, a method for forming a dense, high-performance coating layer by gas plasma spraying is provided.

(Means for Solving the Problems) The present inventors have conducted research on coke oven furnace bricks and experimental studies on plasma spraying, and have found that, regarding the application of a thin coating layer to silica bricks, The following findings were obtained.

(2) On the surface of the furnace wall facing the carbonization chamber during operation, penetration of alkali, Fe2O, Al2O3, and CaO originating from coal is observed, and the fire resistance gradually decreases. For this reason, 5i
High refractory Cr that has a solid solution relationship with Ot or 5in2
It is necessary to form a film containing z03 as the main ingredient.

(2) The thermal spraying method is superior to coating methods in terms of film adhesion, and the amount of pores is 1 to 10%, with many having sealed cells.

■ High viscosity and poorly soluble SiO is used to obtain a smooth film.
It is effective to use Si or Cr in combination to make □ or Cr20= into a highly fluid melt.

■ In order to form a thin film with high adhesion, it is effective to increase the running speed of the thermal spray gun and use plasma gas at a higher temperature than the conventional combustion flame. and Cr are integrated by diffusion and oxidation into the brick.

■ To create fine droplets and create a smooth film,
The material particles preferably have a diameter of 50 μm or less, and the granulated particles stabilize the material supply to the thermal spray gun.

The present invention has been made based on the above knowledge, and the first is that unlike conventional thermal spray repair, it increases the running speed of the gun and uses Ar gas plasma as a heat source to create a strong thermal sprayed coating with a thin film thickness. It can be formed and repeatedly applied to any required location. The second method uses fine particles of 5iOz, Crz (h, Si, Cr mixture, compound) as raw materials, and by thermal spraying a fine particle mass made by mixing and granulating these, a film with high adhesion and excellent smoothness is created. The purpose is to make it easy to integrate with silica bricks.

That is, the first aspect of the present invention is to operate a plasma jet using Ar gas as the main working gas at a running speed of 10 to 30 m/mi.
This is a method for preventing carbon adhesion on a coke oven wall surface, the gist of which is to thermally spray the coating to a thickness of 5IIlff1 or less while operating within the range of n.

The second aspect of the present invention is that the thermal spray material used in the first aspect of the present invention is SfO□ or C with a particle size of 50 to 0.1 μm.
r, 0.0 fine powder is 80-20-1%, the rest is particle size 50
~10μm of St, Cr or a mixture thereof,
This is a method for preventing carbon adhesion on a coke oven wall surface, the gist of which is sizing particles to a particle size range of 200 to 50 um.

(for production) The reasons for limitations in the method of the present invention will be explained below.

First, a known plasma spraying device is used in the method of the present invention. In this case, Ar is used as the primary gas for thermal spraying. The reason is Ar
This is because Heas plasma is ultra-high temperature and high-speed plasma, so it is easy to correct the smoothness of the coating and excessive overlay after construction. Further, the secondary gas is not particularly limited, but He is desirable, for example. And H as a secondary gas
When using e, the amount of He added is He/Ar ratio 5/
The flow rate ratio shall be 100 or less. This is because He speeds up the plasma flow and improves the adhesion of droplets, but if the amount added exceeds 5/100, the voltage will become high and the gun and electrode itself will be likely to be damaged. Note that He is expensive, and it is desirable to use it depending on the economic effect. Next, the running speed of the plasma gas is set in the range of 10 to 30 m/min. 10m/mi
If it is less than n, splash will occur and unmelted particles will be trapped, impairing the smoothness of the film.

Moreover, if it exceeds 30 i/mtn, the adhesion rate will be extremely low, making it uneconomical.

Next, the thickness of the thermal spray coating by the method of the present invention is 5- or less. This is because if the central part of the oven is coated, there is a concern that the extrusion resistance of coke will increase, which will adversely affect the operation of the coke oven.

Ideally, it is desirable to form a highly adhesive film with a thickness of 3 m+n or less.

Next, regarding the particle form of the raw material for thermal spraying, SiO□ or Cr2O3 particles are in the range of 50 um to 0.1 μm, preferably 20 to 0.5 μm. This is because if it is less than 0.1 μm, it tends to aggregate, making it difficult to handle and uniform mixing. On the other hand, if the diameter is 50 μm or more, the number of unmelted particles increases, resulting in poor adhesion and smoothness.

The St or Cr particles have a size in the range of 50 μm to 10 μm. This is because if the thickness is less than 10 μm, it will be easily oxidized by the outside air drawn into the plasma jet, and the required performance will not be exhibited. On the other hand, if the thickness exceeds 50 μm, the oxidation process inside the film causes a large volume change, which may cause the film to peel off.

Next, the material composition is SiO2 powder or CrzO
*The powder should be in the range of 80-20-t%. This is because if it exceeds 80wt%, the contact area between the metal phase of the film and the furnace wall will be small, and the adhesive strength due to integration after construction will be poor. On the other hand 20
This is because if it is less than %, the molten metal will splash violently and efficient film formation will not be possible.

Next, 200% of the thermal spray raw materials having the particle size and mixing ratio described above were added.
The reason why the particle size is rectified in the range of ~50 μm is that if the particle size exceeds 200 μm, it cannot be thermally sprayed with Ar gas in a plasma apparatus. On the other hand, if the thickness is less than 50 μm, clogging will occur in the plasma device.

The granulator can be manufactured using any of the well-known centrifugal flow granulators, stirring and mixing type granulators, or mixing-extrusion granulators. For example, the raw materials may be mixed by adding an aqueous solution of an organic sizing agent such as PVA or CMe, followed by drying with hot air after granulation, and after drying, the particles may be sized to a particle size range of 200 to 50 μm.

Coating is performed by the method of the present invention under the above-mentioned combination of thermal spray gun operating conditions and materials, and carbon is sufficiently burnt off as pretreatment of the substrate surface for thermal spraying. The effectiveness of the plasma gun according to this method for burn-off is known from Japanese Patent Application Laid-open No. 6, filed earlier by the applicant.
It was already disclosed in the publication No. 0-235986. It is desirable for Group Evaturn to be repeatedly laminated with films of 1 mm or less. Repeated lamination corrects the unevenness of the old wall, but it is more effective in reducing the diameter of the pores in the membrane.

(Example 1) Oxide powder with a particle size of 15 to 0.1 μm and 50 to 10
A 5% pvA aqueous solution was added to the powder, and the mixture was stirred and mixed to form granules. This was dried with hot air, and the particles with a diameter in the range of 150 to 75 μm were recovered and used as a thermal spray material.

A gas mixture ratio: He/Ar = 0/100 to 3/10 was placed on the surface of a silica brick heated to 1000°C in an electric resistance furnace.
0, outlet current: 850-900 A, gun running speed: 15-20 m/win, spraying distance: 60 mm, a thermal sprayed coating with a thickness of 2.5 mm was formed, and the state and properties of the coating were investigated.

For comparison, a mixed powder having a particle size of 150 to 55 μm was thermally sprayed under the same conditions to form a film, and a similar investigation was conducted.

Table 1 below shows the compounding conditions of the materials and the investigation results of the film.

As a result, superior film adhesion yield, brick adhesion (adhesive strength), and smoothness were obtained compared to conventional methods.

(Example 2) Two types of thermal spraying materials obtained in Example 1, ■ and ■, were prepared, and they were sprayed directly under the central coal charging hole of furnace group A (furnace height: 5 m, furnace temperature: 1250°C). The furnace wall surface was coated to a thickness of 5 mm or less. It was decided that the covering area would be applied to two areas of 20 to 35 levels above the hearth, each with no seams, and then contrasted with the furnace wall on the opposite side. A follow-up investigation was conducted during periodic inspections, and the state of carbon adhesion and peeling of the film were mainly examined visually.

The raw materials used were commercially available materials with a purity of 97% or more, and the particle size was divided into a range of 44 to 1 μm.

In addition, for comparison, a material B having almost the same composition as the furnace mouth sprayed material was prepared from a reagent and a film was formed by plasma spraying.

Thermal spraying conditions during construction are gas mixture ratio:)le/Ar=0/1
00, Output current: 900A, Gun running speed: 15
~20 m/sin, thermal spraying distance: 45 to 50 M, but in the case of material B, the running speed of the gun was lowered to 1.5 m/min to ensure a sufficient film thickness.

In addition, carbon was burnt off from the wall surface before construction by leaving it in an empty state for 20 hours from the previous day. The wall temperature before and after construction varied only by 975-1030°C. Second
The table shows the construction location and inspection results.

Table 2 As a result, after one month, carbon adhesion was observed at the joints of the furnace wall that was not coated, and after three months, the adhesion layer had expanded and it became difficult to distinguish between the joints. Also, during the 6-month inspection, abnormalities in the unloading of the kiln began to occur frequently, so the kiln was immediately vacated.

On the other hand, the treated wall surface to which the method of the present invention was applied had almost no adhesion of carbon, and no peeling was observed even by thermal shock caused by the voids. However, in the case of the treatment of the comparative example, adhesion at the vertical joints became noticeable, and the adhesion tendency increased after the voids were formed due to peeling of the film.

(Effects of the Invention) As explained above, according to the method of the present invention, the coating treatment to prevent carbon adhesion, which was conventionally limited to the vicinity of the kiln mouth, can be extended to the central part of the furnace, and the number of cavity operations for removing adhesion can be reduced. Productivity improves by reducing Furthermore, by suppressing the progression of damage to the reactor body, the life of the reactor can be extended.

Claims (2)

[Claims] (1) A method for preventing carbon adhesion on a coke oven wall surface, which comprises thermally spraying a coating to a thickness of 5 mm or less while operating a plasma jet using Ar gas as the main working gas at a running speed of 10 to 30 m/min. . (2) SiO_2 or C with a particle size of 50 to 0.1 μm
A claim characterized in that the thermal spray material is composed of 80 to 20 wt% of r_2O_3 fine powder and the remainder is Si, Cr, or a mixture thereof with a particle size of 50 to 10 μm, sized to a particle size range of 200 to 50 μm. Item 1. The method for preventing carbon adhesion on a coke oven wall surface according to item 1.