JP3016106B2 - Repair method for thermal spraying of kiln - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for repairing a thermal spray of a kiln,
For example, the present invention relates to a method for repairing a damaged portion of an inner wall surface of a kiln such as a coke oven by thermal spraying. In particular, in a method in which oxidizing particles in the repair material react with O ₂ to generate heat enough to melt the refractory particles, and thereby adhere to the surface of the repair target, the above phenomenon occurs within a required spraying distance. The present invention relates to a method for improving workability and improving a repair effect by defining a ratio between a powder material and a discharge gas, that is, a solid-gas ratio and a method of mixing the ratio in order to achieve the above.

[0002]

2. Description of the Related Art Various heating furnaces and reaction smelting furnaces lined with refractories are used in a steel manufacturing process, and they are operated continuously for a long period of time. In order to extend the life of the equipment, the furnace inner wall is repaired at high temperatures even during operation. Conventionally, when damage has been found, refractory particles have conventionally been sprayed to repair the inner wall. At that time, a binder containing an inorganic binder and water was used as a binder required for adhesion.

Recently, a technique for spraying refractory particles has been adopted. For this purpose, there are flame spraying method using flammable gas, plasma spraying method, and a kind of thermite reaction method in which metal powder mixed with refractory powder is transported in an oxygen stream and ejected into a hot atmosphere to create a flame.
(Example: See Japanese Patent Publication No. 49-46364).

[0004] Unlike conventional wet methods, these thermal spray methods can be classified as dry methods, have no adverse effects due to added water, and have exhibited excellent repairing effects. However, on the other hand, unlike the wet method, the configuration of the attached equipment became complicated in terms of flame generation and ensuring its stable control, and the equipment to be repaired was used differently, naturally lacking versatility, and tended to function differently. Furthermore, because the repair effect is high, it is necessary to expand the application to the area where it was previously considered impossible to repair, the demand for flame generation and its stable sustainability has increased, and the repair machine itself has been further mechanized. Automation has been promoted, and the development of software that satisfies these requirements has become a development issue. In particular, it is essential to keep the distance between the wall and the repair nozzle (spray distance) within a certain adjustment range to form a flame.

[0005] In a coke oven during a recent steelmaking process, inclined production has been performed to increase production in a specific furnace group from the viewpoint of improving productivity. For this reason, damage was progressing in the furnace group where the operation load became large, and it was necessary to shorten the repair time. On the other hand, in a furnace with a reduced load, the frequency of load change itself tends to increase from the viewpoint of fine adjustment of production adjustment, and the repair amount tends to increase. In particular, as the furnace age progresses, these damages in the central part of the furnace lead to the generation and growth of wall cracks, and a new repair system has to be constructed.

On the other hand, as already disclosed,
No. 93384) The present inventors have developed a fully automatic remote controllable apparatus, device and system for repairing the above-mentioned central part of the furnace. However, this device incorporates various sensors such as an observation eye, a position recognition eye, and a distance meter from the viewpoint of achieving smooth mechanical control, and has a cooling structure. It is necessary to provide. In particular, the coking chamber has an average furnace width of 400 mm in the case of a coke oven having a so-called oven height of 4 m, and has a taper of ± 30 mm in the longitudinal direction in consideration of the extrudability of coke. At the same time,
It has a trapezoidal cross section with a taper of about 10 mm. In addition, each of the coal inlets has a small diameter of 400 mmφ, and these dimensions change slightly as the furnace ages. Under such circumstances, the effective size of the repair arm is significantly limited to 300 mm or less. As described above, since the inside of the carbonization chamber has a narrow configuration, the spraying distance becomes extremely short.
In order to achieve the repair under such dimensional restrictions, that is, to form a flame, it was necessary to thoroughly study materials, heat sources, and the structure of the nozzle.

[0007]

In view of these circumstances, the present inventors have paid attention to the flame method based on the thermite reaction method in view of the situation of the relative increase in the amount of repair. The setting of various conditions was examined as a completely different thermal spraying method.

The details of the conventional thermal spraying method using the thermite method are described in JP-B-49-46364 or JP-B-49-463.
This is clear from the '56831 publication. In each case, the refractory particles, oxidizing particles and oxygen gas of the main material are only discharged from the nozzle in a simple mixed state, and the appropriate value of the spraying distance is 10
Between 0 and 200 mm. An example is schematically shown in FIG. 2. According to this, pure oxygen 10 and powder + carrier gas 12 are mixed in a mixing chamber 14 which is a lance, and are constituted by a discharge port 16 provided at the tip thereof. Is sprayed from the spray nozzle 18.

[0009] Such a conventional method is suitable for visual construction by hand operation, but does not consider the safety of work for remote operation. In particular, if the distance is set to less than the required 80 mm, ignition is unstable and spraying cannot be maintained. During the airflow at the discharge port depending on the mixing of the powder carrier gas
O ₂ concentration fluctuates greatly and flashback occurs frequently before and after thermal spraying work. When a part of the inert gas is mixed, the degree of the flame misfiring during the thermal spraying increases. Due to the excess gas, the amount of heat of the ignition and the flame is consumed to increase the gas temperature, lowering the melting efficiency, increasing the heat load on the water-cooled structure, and easily causing equipment trouble. It is difficult to form a stable thermal spray frame by the conventional method of transporting thermal spray material by airflow, and it is not possible to achieve sufficient repair.

Here, an object of the present invention is to provide a method for repairing a kiln by a thermal spraying method, which can solve the problems of the prior art as described above. Further specific objects of the present invention are:
In particular, it is a thermite reaction spraying method that can repair the coke oven wall remotely by securing a stable flame formation over a short distance to obtain a dense sprayed repair layer and greatly reduce the occurrence of flashback and misfire Accordingly, it is an object of the present invention to provide a method for repairing a thermal spray of a kiln, which can improve operability and reliability.

[0011]

Means for Solving the Problems The present inventors have made various studies in order to achieve such an object. As a result, it has been found that there is a certain critical operation range in the mixing ratio and the mixing form (shape) of the gas body and the powder to be transported.

Here, the present invention provides a system in which a pure oxygen gas stream and a powder carrier gas stream are sent to a spraying nozzle on separate lines and mixed in a mixing chamber and a stirring chamber provided in front of the nozzle discharge port. A method for repairing a thermal spray of a kiln performed by a thermal spray method,
The ratio between the weight of the powder fed to the thermal spray nozzle and the total gas weight is adjusted to 0.5 to 2.9, and the inlet of the pure oxygen gas flow is opened in the mixing chamber, and the downstream side of the mixing chamber is provided. The stirring chamber is provided, and the spraying nozzle is set to T
This is a method for repairing the thermal spraying of a kiln, comprising a discharge port branched in a letter shape.

In a preferred embodiment of the present invention, a gas in which the oxygen concentration in the gas is adjusted to 21 to 73% by volume is used as a powder carrier gas, and a gas between the pure oxygen gas amount and the powder carrier gas amount is used. In addition, by adjusting the amount of the powder carrier gas in the range of the flow ratio of 1: 0.3 to 1: 0.7 by volume ratio, the amount of construction can be adjusted. Thus, according to the present invention, it is possible to perform the work restricted to the spraying distance of 60 ± 15 mm to the repair target.

[0014]

FIG. 1 is a schematic explanatory view showing a configuration example of a spraying nozzle device used in the present invention. In the drawing, a spraying discharge nozzle device 20 has a substantially T-shaped curved pipe shape, a mixing chamber 22, and a lance shape. Powder carrier gas air flow inlet pipe 24, oxygen gas inlet pipe
26, comprising a nozzle discharge port 28 and a stirring chamber 30. Mixing room 22
And the stirring chamber 30 are formed of the same pipe, and the stirring chamber 30 is provided with the downstream side of the mixing chamber 22 as a blind wall. A thermal spray nozzle 32 is branched and connected in a T-shape between the stirring chamber and the mixing chamber (boundary portion).

The oxygen gas introduction pipe 26 is provided on a separate line from the powder carrier gas air flow introduction pipe 24, and is connected to the side wall of the mixing chamber. The angle between the axis of the mixing chamber and the oxygen gas introduction pipe, that is, the oxygen gas inflow angle θ is set to 10 to 90 degrees.

The discharge diameter (a) of the spray nozzle 32 varies depending on the amount of material supplied. However, in the feed range of 350 ± 100 g / min, 7.
5 mmφ is appropriate. If it is less than 5.5 mmφ, nozzle clogging is liable to occur, and if it exceeds 12 mmφ, the bead width of spray deposits is 20 mm.
As described above, the filling of the target region crack deep portion is likely to be incomplete.

The discharge nozzle length (n ₀ ) was suitably 75 mm. In particular, if the diameter is less than 40 mm, the gas-powder mixed fluid cannot be completely rectified, which is inconvenient for flame (flame) formation. The spray nozzle 32 is connected at right angles to the axis of the mixing chamber. Connection angle
(θ) is preferably within 90 ° ± 10 °. Of course, it is indispensable to drive the nozzle discharge port 28 by three-dimensional control with respect to the repair wall which is the repair target. The condition is formed, the repair finish is poor, and the required effect cannot be obtained.

The diameter (R) of the mixing chamber is not particularly limited, but usually needs to be about 1 to 1.5 times the discharge port diameter (a) of the nozzle. This means that if R / a is less than 1/1, it is difficult to obtain a uniform mixture, and the generation of frames will fluctuate. On the other hand, if R / a exceeds 1.5 / 1, it will affect uniform mixing. However, this is because the generation of the flame varies depending on the inflow position of the oxygen gas.

The length (m) of the stirring chamber is preferably longer than the discharge port diameter (a) of the nozzle and shorter than the diameter (R) of the mixing chamber. This is because if the length (m) of the stirring chamber is shorter than the nozzle diameter (a), the refractory particles (coarse particles) that make up the powder
This is because metal and metal powder (fine powder) are separated, which hinders thermal spraying. In particular, when the length (m) of the stirring chamber is less than 5 mm, the wall of the stirring chamber is worn and causes a trouble. On the other hand, if the length (m) of the stirring chamber is longer than the diameter (R) of the mixing chamber, the material will be remarkably retained in the stirring chamber, causing nozzle clogging and flashback.

The length (l) of the mixing chamber is structurally determined by the oxygen gas inflow angle φ. That is, the oxygen gas inflow angle φ
In the range of 10 to 90 degrees, the length (l) of the mixing chamber is usually preferably 90 mm or less. The reason is that the length exceeding 90 mm does not affect the mixing of powder and gas, but is unnecessary due to other built-in parts such as piping, nozzle cooling jacket, nozzle drive etc. omitted in the drawing This is because

Here, according to the present invention, the spraying repair of the kiln is performed by using such a nozzle spraying apparatus. In this case, a pure oxygen gas stream 10 and a powder carrier gas stream 12 are used. Is supplied to the spraying discharge nozzle device 20 on a separate line, and is mixed in the mixing chamber 22 and the stirring chamber 30 provided before the spraying nozzle. At this time, by adjusting the ratio of the weight of the powder fed to the spray nozzle to the total gas weight to be 1.1 to 2.9, it is possible to perform the construction in which the spray distance to the repair target is controlled to 60 ± 15 mm.

Preferably, a gas in which the oxygen concentration in the gas is adjusted to 21 to 73% by volume is used as a powder carrier gas, and the volume ratio between the pure oxygen gas amount and the powder carrier gas is 1: 1: 0.3
The construction amount may be adjusted by adjusting the amount of the powder carrier gas in the flow rate range of 〜1: 0.7. Next, the reason why the spraying conditions are limited as described above in the present invention will be described in more detail in relation to its operation.

First, the present invention is intended mainly for repairing a damaged portion on the furnace wall in the central part of a coke oven. Unlike the damage on the kiln opening, the main work is to form a linear beat. It is. Therefore, the repair operation is performed by an automatic operation under a powder supply of 150 to 500 g / min, preferably 300 g / min. For this reason, from the viewpoint of enhancing operability and securing safety, the spraying machine used uses a method in which the pure oxygen gas stream, the powder gas stream, and the powder carrier gas stream are separately transported and assembled before discharging. Each air flow is individually controlled.

The refractory particles used are composed of calcined silica having an SiO ₂ purity of 95% or more and oxidizable particles in consideration of the above-mentioned applications.
It is preferable to use an existing material in which Al and Si powders are mixed. However, in consideration of the heat generation rate and melting rate of the material, the particle size composition is generally limited to a particle size of 200 μm to 0.2 μm. If it is less than 0.2 μm, fume loss easily occurs,
This is because particles exceeding 0 μm are incompletely melted, and the yield of adhesion is rapidly deteriorated.

In the present invention, in order to maintain the spraying within the spraying distance of 60 ± 15 mm, the ratio of the powder weight to the total gas weight (solid-gas ratio) is generally 0.5 to 2.9, particularly 1.1 to 1.5. It is desirable to control the amount of cutting. Thermal spraying is possible even in the solid-gas ratio range of 0.5 to 2.9, but it is necessary to vary the spraying distance in a width of 40 to 85 mm, which is not preferable in terms of automation. In particular, if it is less than 0.5, a porous repair layer is easily formed and adhered at a low flow rate, and it is necessary to adjust both the distance and the gun traveling speed at the same time, so that control becomes virtually impossible. If the solid-gas ratio exceeds 2.9, the molten particles from the nozzle outlet will be strongly dispersed, easily misfiring and widening the adhesion area, making it impossible to fill cracks accurately. In particular, in order to eliminate misfires (extinction of flame during thermal spraying), it is necessary to limit the solid-gas ratio to a range of 1.1 to 1.5.

In the preferred embodiment of the present invention, the oxygen concentration in the powder carrier gas stream is limited to the range of 21 to 73% (volume) in order to secure required ignitability and adhesion. That is, if it is less than 21%, it is difficult to achieve thermal spraying due to lack of oxygen. On the other hand, if it exceeds 73%, the ignition meltability is generally good. However, since the supply of powder is controlled for the required construction amount, excessive oxygen The gas is rather consumed for producing NOx, etc.
This is because it does not contribute to melting but rather increases the risk of flashback.

Further, it is preferable to adjust the substantial amount of the oxygen gas and the amount of the carrier gas by adjusting the opening ratio of the powder conveying system so as to have a flow ratio of 1: 0.3 to 1: 0.7.
If the carrier gas falls below 0.3, the breathing phenomenon in the mixing chamber (described later) tends to occur, and flashback tends to occur. If it exceeds 0.7, the mixing in the mixing chamber becomes uneven and misfiring easily occurs.

On the other hand, in order to avoid the risk of flashback, it is essential to remove the moisture in the gas, so the dew point of the carrier gas is adjusted. The controlled temperature is preferably 5 to 14 ° C., but a mist separator is provided at the piping including the purged inert gas piping, and the moisture is controlled so that the operation can be performed at a normal temperature of 1% or less. That is, these piping systems are partly or entirely adjacent to the heat-resistant water-cooled jacket or cooling piping system.

[0029]

Next, the operation and effects of the present invention will be described more specifically with reference to the following examples. (Example 1) A test furnace preheated to 950 ° C under the gas setting conditions shown in Table 1 by changing the shapes of the mixing chamber 22, the stirring chamber 30, the nozzle 32, etc. using the thermal spray discharge nozzle device 20 shown in FIG. A thermal spray test was performed. As a comparative example, a case where thermal spray repair was performed using the apparatus shown in FIG. 1 is also shown. The results are also shown in Table 1.

In this embodiment, a siliceous material (SiO ₂ : 95.5%) containing 1% of Al powder and 12% of Si powder as metal powder was fed. The running speed of the thermal spraying apparatus 20 was set to 1.0 m / min, and the amount of oxygen gas was adjusted within a range of 1.0 to 2.0 in a solid-gas ratio to form a bead-like construction having a length of 1.5 m on the inner wall of the test furnace. In addition,
The oxygen concentration in the powder carrier gas was adjusted by separately adding oxygen gas. The material of the thermal spray nozzle was SUS304. The spraying distance was 60 ± 15 mm.

As is clear from the results shown in Table 1, in the conventional thermal spray discharge nozzle apparatus having no stirring chamber, the beads (in height) formed on the inner wall of the test furnace are not uniform due to poor ignition, and The unevenness of the finished surface is remarkable due to the occurrence of brushing. On the other hand, according to the method of the present invention, ignitability, adhesion, and thermal spraying conditions were good, a dense bead was formed with a triangular cross section, and the finished surface of the construction was also good.

When a spraying nozzle having no stirring chamber is used even if the mixing chamber and the nozzle long part have a curved tube shape (for example, and), the stability of ignitability is poor and the adhesion rate is extremely high. Because of the decline, it is difficult to form the construction body,
Misfires and flashbacks occurred frequently. In the example of the present invention, none of these troubles occurred during the seven times of construction.

(Example 2) Thermal spraying was performed under the gas setting and gas-mixing form shown in Table 1, and the amount of powder carrier gas was changed.
The state of adhesion was grasped. The spraying conditions for obtaining the adhesion amount of adhesion index 100 were as follows: the material cut-out amount was 300 g / min, and oxygen-added air having an O ₂ concentration of 25% in the carrier gas was used. Therefore, by adjusting the amount of carrier gas, the actual amount of material discharged can be reduced as shown in FIG.
It becomes like the horizontal axis. Further, the adhesion state was investigated by changing only the O ₂ concentration in the carrier gas. As a result, as apparent from FIG. 3, it was found that the comparative deposition yield was stable when the flow rate ratio of the carrier gas was in the range of 0.3 to 0.7, and that the feed rate could be easily adjusted. When the O ₂ concentration was less than the required range, the adhesion rate itself rapidly deteriorated, and flame formation was unstable. Increasing the O ₂ concentration drastically improved the amount deposited, but the yield deteriorated due to flashback or splash.

[0034]

[Table 1]

[0035]

As described above, according to the present invention,
Since the mixing state of powder and gas discharged from the spray nozzle can be properly and stabilized, not only can ignition failure and frame generation fluctuation be prevented, but also trouble such as flashback is eliminated. This provides an excellent effect that the thermal spraying can be performed efficiently and stably. Therefore, repairs such as cracks in the central part of the coke oven, which could not be sufficiently repaired by the conventional thermal spray repair system using the thermite reaction method, can be repaired accurately and efficiently, and the life of the furnace can be extended. It greatly contributes to.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing a nozzle structure in the method of the present invention.

FIG. 2 is a schematic explanatory view showing a nozzle structure in a conventional method.

FIG. 3 is a graph showing a relationship between a gas distribution ratio and adhesion when powder feeding conditions are changed.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Makoto Numazawa 4-5-33 Kitahama, Chuo-ku, Osaka City Inside Sumitomo Metal Industries, Ltd. (72) Takao Yamazaki 4-5-33 Kitahama, Chuo-ku, Osaka Sumitomo Sumitomo (56) References JP-A-6-81119 (JP, A) JP-B1-56831 (JP, B2) JP-A-4-502937 (JP, A) (58) Fields surveyed ( Int.Cl. ⁷ , DB name) F27D 1/16 C21B 7/06 303 C23C 4/12

Claims (2)

(57) [Claims] 1. A kiln for performing a spraying method of a method in which a pure oxygen gas stream and a powder carrier gas stream are sent to a spray nozzle on separate lines and mixed in a mixing chamber and a stirring chamber provided in front of the nozzle discharge port. A method for repairing a thermal spray of a furnace, wherein a solid-gas ratio between a weight of the powder fed to the thermal spray nozzle and a total gas weight is 0.5 to 2.
9, and the inlet of the pure oxygen gas stream is opened in the mixing chamber, and the stirring chamber is provided downstream of the mixing chamber,
A method for repairing a thermal spray of a kiln, wherein the thermal spray nozzle comprises a discharge port branched in a T-shape from between the two chambers. 2. A gas in which the oxygen concentration in the gas is adjusted to 21 to 73% by volume is used as a powder carrier gas, and the volume ratio between the pure oxygen gas amount and the powder carrier gas is 1: 0.3. ~ 1: 0.7
The method according to claim 1, wherein the amount of the powder carrier gas is adjusted within the range of the flow rate ratio to adjust the amount of construction.