JPH0559352B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for repairing damaged parts of inner walls (lining refractories) in industrial furnaces such as coke ovens and smelting furnaces by plasma spraying. The inner walls of industrial furnaces such as coke ovens and smelting furnaces are usually
Because they are exposed to high temperatures of over 1000℃, they not only suffer from penetration of high-temperature substances and melt damage, but also damage such as thermal cracking and peeling. A common method for repairing such damaged areas is to spray monolithic refractories onto the damaged areas; however, with this spray repair method, steam explosion occurs during the heating process of the monolithic refractories after construction. There is a disadvantage that stable adhesion cannot be obtained if the binder (binding agent) in the monolithic refractory becomes unevenly distributed during spraying. Therefore, as a way to eliminate these drawbacks,
The inventors developed a method for repairing the inner wall of a furnace by plasma spraying (Japanese Patent Application Laid-open No. 49889/1989). This furnace wall repair method uses a plasma jet with Ar and _N2 gas as working gas, and repairs the furnace wall by thermally spraying refractory powder such as ceramics while heating the furnace wall with the jet frame. (Thermal spraying) At the same time, strength comparable to bricks can be obtained, welded to the base material brick and has a strong adhesive strength, the construction material is dense and does not allow gases such as CO gas and water vapor to pass through, and the temperature of the construction wall surface due to rapid cooling It has the following advantages: it does not cause deterioration and has no adverse effect on the base brick, it allows for free selection and combination of refractory materials, and it does not require a special binder. However, in the case of the above plasma spraying method,
The distance between the thermal spray gun and the furnace wall greatly affects the adhesion efficiency of thermal spray materials such as ceramics. On the other hand, in most cases, the damaged part of the furnace wall of a kiln is not a smooth surface but has an uneven surface, and the depth of the cracks also differs. Therefore,
When repairing furnace walls using plasma spraying,
It is necessary to adjust the position of the thermal spray gun to correspond to changes in the shape of the damaged area. Conventionally, the method of achieving this is to mechanically move the spray gun to ensure the spraying distance, but this mechanical method requires a complicated control mechanism and a huge amount of incidental equipment, and the equipment It has the disadvantage of being very expensive. Therefore, the inventors investigated various ways to maintain the spraying distance constant in response to changes in the unevenness of the damaged part of the furnace wall and the depth of defects without using mechanical means. In particular, we have found that changing the frame length due to changes in the gas mixture ratio can respond to changes in the shape of the damaged area. The method for repairing a furnace according to the present invention uses a plasma jet made by adding _N2 gas to Ar as a working gas, and repairs the damaged part of the furnace wall by thermally spraying it with refractory powder while heating the damaged part of the furnace wall with the jet frame. In the method,
The spraying distance is measured according to the unevenness of the damaged part of the furnace wall, and the scratch depth is detected, and the amount of N ₂ gas is adjusted to a certain amount of Ar gas according to the depth of the scratch in the damaged part of the furnace wall. By adding in the range of 0 to 10% in terms of external application rate, an appropriate thermal spray distance can be obtained, and by adjusting the running speed of the thermal spray gun in the range of 0.5 to 3.0 m/min, the heating state of the damaged area can be controlled. It is characterized by ensuring that This invention method will be explained in detail below. First, the elements that make plasma spraying work will be explained. In order to obtain an ideal thermal spray coating, it is necessary to satisfy many factors to be considered (References, for example, "Research on plasma spraying method" by Okada)
(1968)). Basically, materials must be selected according to the purpose of construction, and plasma gas, arc current, arc voltage, gun running speed, spraying distance, and powder feed rate must be set. Moreover, although it is necessary to set the variation range narrowly in order to obtain an ideal film, it must be set as an allowable range in response to changes in the process of use, such as changes in arc voltage due to electrode wear. It won't happen. In particular, as mentioned above, the damaged part of the furnace usually does not have a smooth surface but has an uneven surface. For this reason, when the thermal spray gun moves along a certain straight line on the damaged area, the length of the perpendicular line connecting the gun tip and the damaged surface at the shortest distance, that is, the thermal spraying distance, is not constant. As a method for keeping the spraying distance constant when the spraying distance fluctuates in this way, the present invention employs a method of varying the length of the spraying frame by changing the mixing ratio of working gases (Ar, _N2 gas). This is because in the case of plasma spraying, the working gas has the greatest effect on the heating state of the flying particles and the heating state of the base material. In other words, in plasma spraying, the most effective way to change the heating and melting state of flying particles and form a film on a base material located at a long or short distance is to adjust the amount of gas. Here, the relationship between the gas amount and the frame length will be explained. FIG. 1 shows the relationship between the N ₂ gas addition amount ratio and the spraying distance, which was found through experiments conducted by the inventors. That is, the frame length is set to a ₀ when the primary gas (Ar) amount Vo is a constant amount. In this case, the appropriate spraying distance L=a ₀ +Δa, and the spraying distance l ₀ that is allowable in terms of adhesion is in the range of a ₀ ≦l ₀ ≦a ₀ +2Δa. Δa here is the distance between the frame tip and the base material surface, and almost coincides with the distance adjustment range. Furthermore, when the amount of secondary gas (N ₂ ) is given as v ₀ and the frame length is a, the allowable spraying distance l is a≦l≦a+
The relationship is 2△a. From these relationships, the mixing ratio of Ar and _N2 gas is
For a constant Ar gas flow rate of 100 parts, the N ₂ gas flow rate to be added should be 10 parts or less, that is, the gas mixture ratio N ₂ /A
The limit is to add r at an external rate of 0 to 10%. For example, as shown in FIG. 2, when the Ar gas flow rate is 55 l/min, the N ₂ gas flow rate can be added up to 5.5 l/min, and the length of the plasma flame becomes 28 mm to 53 mm. Further, |Δa| is about 5 mm, and in this case, almost the same coating can be obtained even if the spraying distance varies within the range of 28 mm to 63 mm. In addition, in FIG. 2, the thermal spraying distance range indicated by the hatched area is the result of taking into account not only the adhesion rate but also the state of melting and solidification of the deposited material and its influence on the base material.
Under the conditions in the upper region of the shaded area ( _N2 amount, spraying distance), the adhered material is poorly melted, and under the conditions in the lower region, the base material tends to be eroded. The sprayed material and base material are waxite powder and silica brick, respectively. If you increase the amount of _N2 gas, lengthen the frame length, and bring the frame tips too close together, excessive heat will be supplied to the damaged area, which may cause thermal shock or melt the inner wall. . Also, _N2
If the amount is reduced too much, the tip of the frame will be too far apart, and the flying particles that have passed through the frame will be cooled down, resulting in incomplete adhesion at the damaged area. Therefore, in this invention, it was decided to add the additional secondary gas (N ₂ ) flow rate in the range of 0 to 10% with respect to the fixed amount of primary gas (Ar) flow rate, and within this mixing ratio range. Then, position the thermal spray gun and adjust the amount of _N2 gas so that the above phenomenon does not occur. In addition, in this invention, the running speed of the thermal spray gun is set to 0.5
It is characterized by adjustment within the range of ~3m/min.
This is because if the running speed of the thermal spray gun is less than 0.5 m/min, the adhering thermal spray material will turn into a splash and reduce the adhesion efficiency, and if it is over 3 m/min, the preheating of the base material by the frame will be insufficient. This is because the adhesion of flying particles becomes poor and efficiency decreases. Next, an example of the configuration of an apparatus for carrying out the method of the invention will be explained based on FIGS. 3 and 4. In Fig. 3, 1 is a thermal spray gun housed in a cooling container with a water-cooled structure, 2 is an imaging device equipped with a television camera and a light emitting device, 3 is a mount to which the imaging device and thermal spray gun are fixed, and A is a control system a. Therefore, the thermal spray gun operating device controls the working gas (Ar, _N2 gas), DC power, electrode cooling water, and feeding powder, and B is the wall surface on which the control system b performs imaging, image reproduction, and spraying distance detection control. An observation device, C a spray gun drive device for positioning and driving the spray gun by control system c, and D a cooling device for cooling the spray gun, television camera, and mount. 4 indicates the repaired wall surface. As a method of measuring the spraying distance, for example, the fourth
As shown in the figure, if two television cameras 12 are used to detect the difference in the position of the two television cameras in the playback screen when spot light emitted from the light emitting device 13 is applied to the repaired wall surface 4, each Since the angles θ ₁ and θ ₂ of the television camera 12 and the mutual distance l' are fixed, the distance L from the television camera 12 to the position of the spot light on the wall surface can be calculated. Therefore, by moving the light emitting device 13 near the damaged area, the depth and width of the damaged area can also be detected. 14 is a reproduction device, 15 is a spot position detection circuit, and 16 is a spraying distance calculation circuit. The thermal spray gun drive device C has a mechanism for moving the thermal spray gun 1 in three axes: The structure is such that the spray gun is driven according to the irregularities (irregularities, crack depth). When using the above-mentioned repair device to repair, for example, a horizontal crack in a part of the wall of a certain furnace by thermal spraying, the thermal spray gun driving device C positions the thermal spray gun 1 at a predetermined height, and , give an appropriate spraying distance depending on the condition of the sprayed wall surface. Thereafter, while measuring the width and depth of the crack with the furnace wall surface observation device B, the thermal spray gun driving device C moves the thermal spray gun 1 at a predetermined speed in the X-axis direction, and a predetermined amount of refractory powder is applied from the thermal spray gun. Thermal spraying is carried out, and the length of the thermal spraying frame is adjusted by controlling the flow rate of N ₂ gas by the thermal spraying gun operating device A according to the flaw depth measured by the furnace wall observation device B, following the movement of the thermal spraying gun. . In this case, the amount of N ₂ gas is adjusted so that the mixture ratio of N ₂ /Ar is within the range of 0 to 10% in terms of external ratio.
Further, the moving speed of the thermal spray gun 1 is adjusted within the range of 0.5 to 3.0 m/min. Note that as the refractory powder, oxides, carbides, nitrides, and composites thereof having a melting point can be used, so a compound of the same type as the lining material of the repair furnace is selected. Specifically, SiO ₂ , Al ₂ O ₃ , ZrO ₂ ,
MgO, _Cr2O3 , CaO, _{Y2O3 , B2O3 , TiO2 ,}
There are TiC, SiC, etc. Further, these may be used alone or in combination of two or more depending on the purpose of use, such as fire resistance, viscosity, strength, and stabilization of the mineral phase. Table 1 shows the results of repairing furnace walls using the above-mentioned apparatus, and the target furnaces are a coke oven lined with silica and a rotary kiln. In order to compare the conventional method and the method of the present invention, the damage area and scale were the same. In both furnaces, the damage was due to breakage and peeling of the furnace walls due to cracks. The work involved repairing cracks with an average length of 2.5m (width 10mm). 5 and 6 show construction patterns in this embodiment, with FIG. 5 showing the conventional method and FIG. 6 showing the method of the present invention. Note that all crack depth profiles are those of Example 1. In the conventional method, the tip of the thermal spray gun was operated by moving along the chain line in FIG. 5B with respect to the profile in the gun driving direction shown in FIG. 5A. The shaded area in FIG. At this time, the output current was also kept constant at 1000A. In this case, it can be seen that the position of the thermal spray gun was changed six times in the depth direction of the crack. On the other hand, in the method of the present invention, the thermal spray gun is moved only twice in the profile shown in FIG. 6A compared to the profile shown in FIG. 6B. At this time, the amount of _N2 was changed as appropriate using a flow meter as shown in Figure C. Also, the output current is
It held 1000A. Here, the vertical axis (distance) in FIGS. 1 to 6 is expressed as an index, with the frame length a ₀ obtained by the Ar amount Vo being 100. Thus, it is clear that the method of the present invention reduces the number of times the thermal spray gun is mechanically driven and improves work efficiency. Furthermore, although the spraying distance tolerance under each _N2 addition condition is approximately ±5 mm, by adjusting the _N2 amount, it is essentially not necessary to move the spray gun to cope with the profile irregularities of ±15mm. be. Therefore, it can be said that intermittent movement of the spray gun in the direction of the crack depth at intervals of 10 to 15 mm is sufficient. As is clear from the above results, it can be seen that the method of the present invention not only reduces working time but also significantly increases the amount of work done per unit time, and efficiently achieves work with high repair effects.

[Table] As explained above, according to this invention method,
By adjusting the amount of _N2 gas added, it is possible to secure a spraying distance that corresponds to the condition of the crack, allowing welding to the deep part of the crack with a constant distance between the spray gun and the repaired wall surface, resulting in almost complete spraying. Repairs can be made. Furthermore, the method of the present invention does not require a complicated mechanical control mechanism for causing the thermal spray gun to follow changes in the crack depth, so it has the advantage of simplifying the apparatus and reducing costs.

[Brief explanation of the drawing]

Figure 1 is a chart showing the relationship between the N ₂ gas addition amount ratio and the spraying distance in plasma spraying using Ar and N ₂ gases as working gases, and Figure 2 is a chart showing the relationship between the N 2 gas addition amount ratio and the spraying distance in the plasma spraying method using Ar and N ₂ gases as working gases.
A chart showing the relationship between the amount of gas added, the spraying distance, the state of melting and adhesion of the sprayed material, and the state of base material erosion. Figure 3 is a block diagram showing an example of the configuration of an apparatus for carrying out the method of this invention, and Figure 4 is the same as above. FIG. 5 is a block diagram showing a thermal spray distance measuring device in the apparatus, FIG. 5 is a chart showing a construction pattern of the conventional method in an embodiment of the present invention, and FIG. 6 is a chart showing a construction pattern of the method of the present invention. 1... Thermal spray gun, 2... Imaging device, 3... Mount, 4...
Repair wall surface, 12...TV camera, 13...Light emitting device, 14...Reproducing device, 15...Spot position detection circuit, 16...Distance calculation circuit, A...Thermal spray gun operating device, B...Wall surface observation device, C...Thermal spray gun driving device ,
D... Cooling device, a, b, c... Control system.

Claims (1)

[Claims] 1. In a method of repairing by thermally spraying refractory powder while heating the damaged part of the furnace wall with the jet flame using a plasma jet with Ar and _N2 gas as the working gas, the By measuring the spraying distance and detecting the depth of scratches, the amount of _N2 gas is added in the range of 0 to 10% to a certain amount of Ar gas depending on the depth of the scratches on the damaged part of the furnace wall. Adjust the length of the frame to a range of 28 to 53 mm to obtain an appropriate spray distance, and adjust the running speed of the spray gun to a range of 0.5 to 3.0 m/min to ensure heating of the damaged area. A method for repairing a kiln, which is characterized by the following.