JPS6135466B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of repairing a refractory-lined structure. Refractory lined structures used in high-temperature furnaces deteriorate, become brittle, and wear out due to thermal or chemical atmospheres during use. For this reason, refractory-lined structures are generally subjected to localized intermediate repairs in order to extend their service life. Normally, intermediate repairs of these refractory-lined structures are carried out by pouring and molding a monolithic refractory made by mixing powdered refractories with water, or by spraying it onto the surface to be repaired. In order to carry out the work, thermal spalling of the refractories due to the temperature drop and rise of the high-temperature building is unavoidable, and the strength of the repaired part is weak. Also, if you try to do this hot, you will have to apply it to the surface to be repaired in the high temperature area.
Poor adhesion, high porosity due to water evaporation,
Fire resistance is poor. In addition, in recent years, as a new method of repairing refractories,
Thermal spray repair methods using refractory powder are being adopted for some refractory structures, but up to now powder spraying methods have mainly been carried out using gaseous fuels and solid fuels. Ta. In powder spraying methods that use gaseous fuel, low molecular weight hydrocarbon compounds such as LNG, LPG, and acetylene are used as fuel, so the flame temperature is generally low and MgO
Because it cannot melt high-melting-point refractories such as
The range of application was limited due to the relatively small capacity of about 500 kg/H. Additionally, there is a danger associated with abnormal combustion of the gaseous fuel and the combustion-supporting mixture such as oxygen. On the other hand, in thermal spraying methods that use solid fuels such as coal and coke powder, the reaction time required for the combustion reaction is long, resulting in the formation of a long flame at a low temperature, making it impossible to melt high melting point materials such as MgO. In addition, ash (SiO ₂ ,
(Fe ₂ O ₃ , Al ₂ O _3, etc.), i.e. refractoriness〓〓〓〓
It had the disadvantage of a decrease in As mentioned above, conventional methods for repairing refractory-lined structures are inherently low in fire resistance when wet repairing monolithic refractories, and conventional thermal spray repair methods cannot melt high-melting point materials. For,
It is not possible to form a construction body with low porosity, high density, high melting point, and high fire resistance, and although it is superior to the wet method in terms of corrosion resistance, it still has drawbacks such as frequent repairs and a small range of application. The present invention relates to a method for repairing a refractory lined structure that improves the drawbacks of the conventional thermal spraying method as described above and forms a refractory repair surface having low porosity, high density, high melting point, and high fire resistance. . The present invention provides for the repair of refractory-lined structures,
Liquid fuel is sprayed from a nozzle at a spray pressure of 1 Kg/cm ² -G (hereinafter simply referred to as 1 Kg/cm ² ) or more in the pipe, and oxygen is added as a combustion agent for the sprayed liquid fuel at a flow rate of 200 m/s or more. Use a powder sprayer with a three-fluid nozzle hole that supplies refractory powder carried by oxygen into the flame discharged from the nozzle and burned at a carrier gas velocity of 10 m/s or more and 90 m/s or less. By repairing the refractory material, a refractory repair surface having low porosity, high density, high melting point, and high fire resistance is formed. Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a powder spraying apparatus according to an embodiment of the present invention. In the figure, 1 is a nozzle for a combustion supporting agent such as oxygen, and 2 is a powder injection nozzle that discharges refractory powder conveyed by oxygen or air. 3 is a liquid fuel injection nozzle, and in order to reduce the diameter of the atomized droplets, the powder is distributed to each nozzle by the distributor 5. A nozzle with a swirler at the tip and a constricted tip is used. It will be done. 4
is a cooling cylinder, which includes a flow path for cooling water. In order to melt the refractory powder in a flame in a powder sprayer and adhere it to the refractory lining, it is necessary to raise the flame temperature above the melting point of the refractory powder. Incidentally, the combustion condition of liquid fuel, that is, the properties of the flame, are determined by the condition of the atomized fuel droplets and the mixing condition of the droplets and the combustion support agent.In order to increase the flame temperature, the diameter of the fuel droplets must be adjusted. It is necessary to make the area of contact with the combustion support agent small by increasing the contact area with the combustion support agent, and to improve the mixing of the fuel and the combustion support agent. Therefore, in order to spray high melting point refractory powder,
In a liquid fuel type thermal sprayer, it is necessary to set nozzle conditions that reduce the diameter of atomized liquid fuel droplets and improve the mixing of the fuel and combustion agent. In addition, the discharge conditions for the refractory powder include ensuring sufficient residence time in the flame, and ensuring a velocity that provides sufficient kinetic energy when colliding with the surface of the refractory to be repaired. It is necessary to set the refractory powder discharge nozzle conditions to achieve this. As a result of various experiments carried out by the present inventors from these points of view, in a liquid fuel type thermal sprayer, the liquid fuel nozzle has a fuel nozzle discharge pressure of 1 kg/cm ² or more,
A repair work with excellent fire resistance can be achieved by setting the flow velocity of the combustion support agent to 200 m/s or more, and setting the discharge velocity of the powder carrier gas to 10 m/s or more and 90 m/s or less as a condition for the powder discharge nozzle. We found that it is necessary to obtain The effects of each of the above conditions will be explained below. First, the atomization state of a liquid fuel nozzle is determined by the aperture, flow rate, and shape of the nozzle, and the relationship therebetween is generally expressed by the following equation. Q=kcd ² .√ Here, Q is the flow rate (m ³ /min), k is the coefficient (-), c is the flow coefficient (-), d is the nozzle diameter (mm), and p is the pressure in the pipe in front of the nozzle ( kg/cm ² ). The nozzle used to atomize liquid is a pressure-type atomizing nozzle, which generally has a structure in which the fluid is swirled within the nozzle in order to reduce the atomized particle size, but the atomization characteristics of the nozzle are The pressure inside the nozzle is dominant. That is, in order to form a high flame temperature, which is a necessary characteristic in a thermal sprayer, it is necessary to increase the pressure inside the nozzle to a certain level or higher. FIG. 2 shows the relationship between the nozzle internal pressure, the center temperature of the flame, and the adhesion rate (hereinafter referred to as the adhesion rate) with respect to the amount of powder supplied, based on experimental results. Note that other conditions in this experiment were according to the present invention. As seen in the figure, the flame temperature increases as the nozzle internal pressure of the liquid increases, and the adhesion rate indicates that refractory material adheres at a point where the nozzle internal pressure is 1 Kg/cm ² or more. 〓〓〓〓
Next, the effect of the combustion stabilizer is shown in Fig. 3. Oxygen was used as the combustion agent in FIG. 3, and other conditions were in accordance with the present invention. In this experiment, a discharge speed of 200 m/s or more was effective for the formation of high-temperature flames and the adhesion of refractories. In addition, if the velocity of the powder carrier gas is less than 10 m/s, sufficient momentum will not be obtained when it collides with the surface to be repaired, so a good adhesion state will not be obtained, and if the velocity exceeds 50 m/s, the Since sufficient residence time cannot be secured, the powder collides with the surface to be repaired in an unmelted state, and the powder is repelled from the surface to be repaired. Further, in the embodiments of the present invention, the structure shown in FIG. 1 has been described, but the present invention does not refer to the number of nozzles, the arrangement method, or the structure of the thermal sprayer. Next, an example will be shown to compare the actual amount of repaired parts of the present invention and the conventional method. It can be seen from this that a repaired part with particularly low porosity and excellent slag corrosion resistance can be formed compared to the conventional method. Example: The refractory powder mainly composed of MgO shown in Table 1 was transported by oxygen, and the delivery flow rate of O ₂ for transport was 30 m/s.
Then, kerosene was sprayed from a nozzle at a spray pressure of 1.5 kg/ ^cm2 , and combustion was caused by combustion-supporting oxygen discharged from the nozzle at a flow rate of 250 m/s to melt the refractory powder and adhere it to the refractory structure. . The amount of kerosene used at this time was 1400/H, and the total amount of oxygen was 2800 Nm ³ /H. Of these, the oxygen for powder transportation was 400Nm ³ /H, and the amount of refractory powder was 4T/H. Incidentally, the thickness of the repair layer was 20 to 40 mm, which showed almost the same corrosion resistance as the dolomite bricks used to construct the refractory lining. Table 2 shows the physical properties and corrosion resistance data of this repair layer sample. This shows that the repaired area according to the present invention has superior corrosion resistance and strength compared to the conventional method.

【table】

【table】 [Brief explanation of the drawing]

Fig. 1 shows a thermal spraying apparatus according to an embodiment of the present invention, in which a is an axial sectional view, b is a sectional view orthogonal to the axial direction, and Fig. 2 shows nozzle internal pressure, flame center temperature, and powder. FIG. 3 is a relationship diagram showing the effect of the combustion-supporting agent. DESCRIPTION OF SYMBOLS 1... Combustion support agent discharge nozzle, 2... Powder discharge nozzle, 3... Liquid fuel nozzle, 4... Coolant flow path, 5... Powder inlet, 6... Liquid fuel inlet, 7...
... Combustion agent inlet, 8... Coolant inlet, 9... Coolant outlet. 〓〓〓〓

Claims (1)

[Claims] 1. In the construction of refractory-lined structures, liquid fuel is sprayed from a nozzle at a spray pressure of 1 kg/cm ² or more, and oxygen is discharged from the nozzle at a flow rate of 200 m/s or more as a combustion support agent for combustion. The refractory powder transported by gas was
1. A method for repairing a refractory-lined structure, characterized in that the repair is carried out using a powder sprayer having a nozzle discharge hole for supplying three types of fluids through a nozzle at a speed of not less than 100 m/s and not more than 90 m/s.