JP3613006B2 - How to repair the wall of a bulkhead furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for repairing a furnace wall of a partition-type furnace having a partition in the furnace, such as a partition-type heat exchanger.
[0002]
[Prior art]
A furnace having a partition in the furnace is generally known as a partition type heat exchanger, and a coke furnace is a typical furnace among them. The coke oven is a furnace for producing coke by dry distillation of coal, and a carbonizing chamber for storing coal and a combustion chamber for generating heated gas are alternately arranged via partition walls made of refractory. In the furnace, the partition walls are heated by the heated gas in the combustion chamber, and the heat is transmitted to the carbonization chamber on the opposite side of the partition walls. Coal in the carbonization chamber is pyrolyzed by heating, generating coke oven gas and proceeding with dry distillation.
[0003]
In general, dry sealing methods and thermal spraying methods have been developed as repair methods for refractories, and are also applied to repair of partition walls of partition-type furnaces. The dry sealing method is a method in which a refractory powder having sinterability is fed into a cracked portion of a partition wall and sintered in the crack for repair.
[0004]
In the thermal spraying method, the powder of the refractory is made into a semi-molten or molten state in a flame composed of oxygen and fuel gas or by burning aluminum or silicon, and is adhered to the damaged part of the refractory. For example, Japanese Patent Publication No. 62-15508 proposes a flame sprayed material applied for such a purpose.
[0005]
Japanese Patent Application Laid-Open No. 6-81119 proposes a thermal spraying method for preventing ignition failure during thermal spraying work, fire extinguishing during repairing, and the like. This technique uses a thermal spraying machine in which a pure oxygen stream and a powder carrier gas are supplied to a thermal spray nozzle on separate lines and mixed in front of the nozzle discharge port.
[0006]
As a repair method based on a completely different principle from these methods, a method using a vapor deposition reaction (hereinafter abbreviated as CVD) has been proposed. Japanese Unexamined Patent Publication No. 9-71781 discloses a method for repairing a partition wall of a partition wall heat exchanger. In this technique, a gas containing silicon tetrachloride is supplied to one space of the partition wall, and a gas containing water vapor is supplied to the other space.
[0007]
In this technique, silicon dioxide SiO ₂ is precipitated by the reaction of silicon tetrachloride and water vapor in the gas. According to this principle, when a gas containing silicon tetrachloride and a gas containing water vapor come into contact with each other in a crack or the like of a refractory material of a partition wall, SiO ₂ , that is, a refractory material is precipitated inside the crack or the like due to a reaction between the _two . Cracks are repaired.
[0008]
[Problems to be solved by the invention]
However, the conventional repair methods have the following problems. First, in the repair work by the dry sealing method, there is a problem that it is difficult to enter the interior of the crack because the supply of the repair material is performed by blowing powder. In addition, since sintering of refractory powder is used, there is a problem that cracks occur again because the shrinkage occurs in the cracks as the sintering progresses during temperature rise or operation in the repaired empty kiln. is there.
[0009]
In the technique using thermal spraying as described in Japanese Patent Publication No. 62-15508 or Japanese Patent Laid-Open No. 6-81119, work is performed by inserting the nozzle of the thermal sprayer into the furnace from the furnace port of the furnace. bad. In particular, when a nozzle is inserted from a charging inlet as in a coke oven, there is a problem that the nozzle does not reach the interior of the furnace and the repairable range is limited.
[0010]
Further, in the thermal spraying method, the composition of the sprayed body is often different from that of the base material, and the bond between the sprayed body and the base material is insufficient. Furthermore, when the base material is altered and the strength is reduced, cracks develop from the base material side and the thermal spray repaired body falls off.
[0011]
In applying the above thermal spraying method, it is necessary to specify a damaged portion to be repaired in advance. However, the damaged part is not limited to a part that can be observed from the outside. If there is no wide opening such as a coke oven charging port, it is difficult to observe the inside of the furnace and identify the damaged part. In addition, since these methods perform work without lowering the furnace temperature, the repair work is performed in a high temperature environment and the work environment is not good.
[0012]
On the other hand, the technique described in JP-A-9-71781 is a method using CVD, and enters a crack by supplying a gas containing a reactive gas such as metal vapor and water vapor. Therefore, it is possible to reliably supply the repair material to the portion where the gas flows inside the partition wall, that is, the crack or the like, without specifying the damaged portion such as the crack position.
[0013]
Thus, although this technique is an excellent method in principle, there is a problem that the thickness of the repair layer is thin, and depending on conditions, there is a problem that the time until the airtightness is improved becomes long. In addition, the formation of the repair layer by CVD in the partition wall may be non-uniform.
[0014]
The present invention has been made to solve the above-described problems, can be repaired hot, can be easily implemented without specifying a damaged portion, and can efficiently form a uniform repair layer. It is an object of the present invention to provide a method for repairing a wall of a partition wall furnace.
[0015]
[Means for Solving the Problems]
According to the present invention, in a furnace wall repair method for a partition-type furnace having a partition wall in a furnace, a gas containing silicon tetrachloride is supplied to one side of the partition wall so that the concentration of silicon tetrachloride in the atmospheric gas is 18%. The gas pressure containing the water vapor is supplied to the other side of the partition wall so that the concentration of water vapor in the atmospheric gas is 220 mg / Nl (normal liters) or more, and the pressure of the atmospheric gas on both sides of the partition wall By alternately pressurizing and reducing pressure, silicon tetrachloride and water vapor are reacted in the partition wall to deposit silicon dioxide, which is a method for repairing a furnace wall of a partition-type furnace.
[0016]
The present invention is a method for depositing a refractory by a gas reaction using CVD. First, by supplying a gas containing silicon tetrachloride from one side of the partition and a gas containing water vapor from the other side, these gases enter the crack from both sides of the partition. . Therefore, it is possible to reliably supply the repair material to the portion where the gas flows inside the partition wall, that is, the crack or the like, without specifying the damaged portion such as the crack position. When silicon tetrachloride and water vapor or the like come into contact with each other in the crack of the refractory material of the partition wall, SiO ₂ is precipitated inside the crack or the like by the reaction of both, and the crack portion is repaired.
[0017]
In the present invention, the concentration of silicon tetrachloride contained in the gas containing silicon tetrachloride (dilution gas) is 18% or more. This is because the reaction rate is too slow when the concentration of silicon tetrachloride is less than this. Here, silicon tetrachloride SiCl ₄ may be used only with a gas of silicon tetrachloride, or may be diluted with a gas that does not react with silicon tetrachloride. For example, N ₂ or Ar may be used as the dilution gas.
[0018]
The density | concentration of the water vapor | steam contained in the gas (dilution gas) containing water vapor shall be 220 mg / Nl (normal liter) or more. This is because the reaction rate is too slow when the concentration of water vapor is less than this. As a gas (dilution gas) containing water vapor, H ₂ O and N ₂ pure gas may be mixed, but various combustion gases may be used. As the combustion gas, any gas obtained by burning natural gas, liquefied petroleum gas, kerosene, heavy oil, coal, coke oven gas, blast furnace gas, converter gas, or the like with air or oxygen can be used. Moreover, you may use the exhaust gas of various heating furnaces as needed.
[0019]
The gas containing silicon tetrachloride reacts with the gas containing water vapor to deposit silicon dioxide. This reaction is shown in the following formula (1).
SiCl ₄ + 2H ₂ O → SiO ₂ + 4HCl (1)
[0020]
The deposited silicon dioxide constitutes the main part of the refractory material of the partition wall, and the thermal expansion coefficient and the like are substantially equal to the refractory material of the partition wall to be repaired.
[0021]
The appropriate reaction temperature of the gas containing silicon tetrachloride and the gas containing water vapor is preferably 600 ° C. or higher. This is because the reaction rate is too slow below 600 ° C.
[0022]
In the present invention, in order to secure the reaction rate, it is necessary to set the furnace temperature of the partition-type furnace to the reaction temperature, and this may be achieved by using the residual heat after the operation of the furnace as it is. This means that it is not necessary to wait for a long time for the furnace temperature to decrease, and the downtime of the furnace can be greatly shortened by repair work. In addition, the time required for raising the temperature of the furnace after the shutdown is greatly shortened, and the reduction in the operating rate of the furnace can be minimized.
[0023]
In this invention, since the lower limit is provided for both the concentration of silicon tetrachloride and the concentration of water vapor, the reaction is promoted even inside the crack, and the SiO ₂ precipitates in the depth direction after the crack is plugged. The situation becomes uniform. Therefore, it is possible to repair almost the entire crack in the depth direction.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the coke oven will be described. The furnace wall (partition wall) of the coke oven is usually made of silica brick, and as shown in FIG. 1, in the combustion chamber 3 on both sides of the carbonization chamber 2, iron making such as blast furnace gas is used as coke oven gas or coke oven gas. A gas mixed with gas generated in the station is burned.
[0025]
Here, the water vapor as the reactive gas is the atmosphere in the combustion chamber adjusted to an appropriate water vapor concentration by adding the water vapor in the combustion exhaust gas in the combustion chamber 3 or the enrichment of water vapor forced into the combustion chamber 3. Is the source. This water vapor is supplied to the inside of the partition wall 1 by depressurizing the adjacent carbonization chamber 3. In addition, silicon tetrachloride as a raw material gas is blown into the carbonization chamber 2 together with a non-reacting gas such as dry nitrogen or dry air so as to obtain an appropriate concentration in the form of gas or mist, and pressurizing the carbonization chamber 2 To supply the inside of the partition wall 1.
[0026]
In this way, as shown in FIG. 2, the repair cycle in which water vapor and silicon tetrachloride are alternately supplied into the partition walls is repeated to repair the partition walls. In addition, a dry seal can be applied before carrying out this repairing method to improve the repairing efficiency.
[0027]
【Example】
Using the experimental apparatus shown in FIG. 3, the CVD repair effect with respect to changes in the silicon tetrachloride concentration and the water vapor concentration was investigated. In this experimental apparatus, a double pipe is inserted into an electric furnace, and a sample (a cracked quartz brick) is fixed to a tip of the inner pipe with a quartz mortar. Sample 11 was processed into a cylindrical shape having a diameter of 20 mm and a length of 100 mm (corresponding to the thickness of the actual furnace partition wall), then cut in the longitudinal direction and sandwiched with a dry sealing material (sintering temperature 950 ° C.), and again The thing assembled in the column shape was used.
[0028]
Between the outer tube and the inner tube was a mixed gas atmosphere of water vapor and nitrogen, and the inner side 12 of the inner tube was a mixed gas atmosphere of silicon tetrachloride and nitrogen. In this way, by alternately depressurizing and pressurizing the inner side 12 of the inner tube, specific concentrations of water vapor and silicon tetrachloride can be supplied into the cracks in the sample 11. In this experimental apparatus, the inner side 12 of the inner tube corresponds to the carbonization chamber, and the outer side of the inner tube, that is, the inner side 13 of the outer tube corresponds to the combustion chamber.
[0029]
The reaction conditions were an atmospheric temperature of 1000 ° C., a silicon tetrachloride concentration of 8 to 26% by volume, a water vapor concentration of 140 to 300 mg / Nl (normal liters), and 50 CVD repair cycles in which the inner tube was alternately depressurized and pressurized were performed. Thereafter, the supply of silicon tetrachloride was stopped, and the time during which the differential pressure of the inner tube 12 with respect to the outer tube 13 decreased from +100 to +10 mmH ₂ O (hereinafter referred to as pressure reduction time) was measured, and the airtightness was compared. At the same time, the sample 11 was cut in the longitudinal direction, the state of the repair layer was observed with a microscope, and the uniformity was investigated.
[0030]
As a result, it can be seen that when the water vapor concentration is 220 mg / Nl (normal liters) or more, as shown in FIG. 4, the pressure reduction time after the CVD repair is remarkably increased, and the airtightness of the cracked portion of the sample can be increased. It can also be seen that when the silicon tetrachloride concentration is 18% by volume or more, as shown in FIG. 5, the pressure reduction time after the CVD repair is remarkably increased and the airtightness of the cracked portion of the sample can be increased.
[0031]
According to the result of observation of the repair layer with a microscope, the individual particles of the dry sealing material are connected to each other, and although there are pores, continuous passages tend to decrease. On the other hand, when the dry sealing material is merely sintered, the individual particles of the dry sealing material are clearly seen, and the appearance of being connected to each other is not seen. It was also confirmed that the sample brick could be repaired uniformly over the entire lengthwise direction (equivalent to the thickness of the coke oven partition wall).
[0032]
Based on the above investigation results, CVD repair was performed using a test coke oven (250 kg type, carbonization chamber volume: about 0.5 m ³ ).
[0033]
First, a dry sealing material (inorganic powder sintered at 800 to 950 ° C. containing fused quartz fine powder as a main component) was blown into the carbonization chamber to pre-fill the cracks in the partition walls.
[0034]
Thereafter, the inside of the carbonization chamber was sucked with a water vapor ejector and reduced to −40 mmH ₂ O with a pressure difference from the atmosphere, thereby supplying water vapor in the combustion exhaust gas into the cracks in the partition walls. Next, the exhaust line of the carbonization chamber is closed with a water seal, silicon tetrachloride is diluted with nitrogen gas (8 to 13 vol.%), And blown into the carbonization chamber, and the pressure is increased to a maximum of 150 mmH ₂ O by the pressure difference from the atmosphere. did. In this manner, a series of operations (cycles) for generating the reaction shown in the above-described formula (1) and generating silicon dioxide were repeated.
[0035]
The effect of the CVD repair was evaluated by changing the gas sealing property by closing the exhaust line of the carbonization chamber with a water seal, blowing nitrogen gas into the carbonization chamber at a flow rate of 50 Nl / min, and measuring the differential pressure from the atmosphere. . When the CVD repair cycle is repeated, as shown in FIG. 6, the gas sealability is improved, that is, the differential pressure with respect to the atmosphere in the carbonization chamber due to nitrogen gas blowing is increased, and the airtightness of the carbonization chamber can be improved.
[0036]
As shown in FIG. 7, the durability of the repair effect is from a few hours to 1 in the case of only dry seal (conventional technology) from the time-dependent change (airtightness) of the pressure in the carbonization chamber measured in the state of the furnace after repair. In the case of CVD repair, there is almost no decrease in airtightness, whereas the airtightness is halved in about days.
[0037]
Moreover, in order to evaluate the durability at the time of actual operation of CVD repair (coal dry distillation), the carbonization chamber gas leakage resistance pressure was measured. Here, the carbonization chamber gas leakage resistance pressure refers to a limit pressure at which the carbonization chamber is pressurized during dry distillation and a flame blows out to the combustion chamber side. As the conditions for the CVD repair, the case where the water vapor concentration was enriched to 250 mg / Nl and the case where the water vapor concentration was not enriched (combustion exhaust gas only) were measured.
[0038]
As shown in FIG. 8, the measurement results confirmed that the CVD repair durability was improved by enriching the water vapor concentration to 250 mg / Nl.
[0039]
【The invention's effect】
By repairing a kiln that is heated through a partition wall by the method of the present invention, the repair effect is increased as compared with the conventional method, and the repair efficiency is improved because the airtightness is well obtained in the same repair time. And it can repair uniformly over the whole repair site | part in a partition.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing the structure of a coke oven.
FIG. 2 is an explanatory diagram of a repair cycle.
FIG. 3 is a cross-sectional view of an experimental apparatus for investigating a CVD repair effect.
FIG. 4 is a diagram showing the influence of water vapor concentration on hermeticity (pressure reduction time) after CVD repair.
FIG. 5 is a diagram showing the influence of silicon tetrachloride concentration on hermeticity (pressure reduction time) after CVD repair.
FIG. 6 is a diagram showing a change in gas sealing performance with repeated CVD repair cycles.
FIG. 7 is a diagram showing durability of repair effect (airtightness in an empty furnace state).
FIG. 8 is a diagram showing the durability of the repair effect (carbonization chamber gas leakage during dry distillation).
[Explanation of symbols]
1 Bulkhead 2 Carbonization chamber 3 Combustion chamber

Claims (1)

In a furnace wall repair method for a partition-type furnace having a partition wall in the furnace, a gas containing silicon tetrachloride is supplied to one side of the partition wall so that the concentration of silicon tetrachloride in the atmospheric gas is 18% or more, and The gas containing water vapor is supplied to the other side of the partition wall so that the concentration of water vapor in the atmospheric gas is 220 mg / Nl (normal liters) or more, and the pressure of the atmosphere gas on both sides of the partition wall is alternately applied. A method for repairing a furnace wall of a partition-type furnace, wherein silicon tetrachloride reacts with water vapor in the partition to precipitate silicon dioxide.

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