JP7502547B1 - Method for removing deposits on blast furnace walls and method for operating a blast furnace - Google Patents

Abstract

[Problem] A method for removing deposits on the walls of a blast furnace and an operating method are proposed. [Solution] A method for removing deposits on the walls of a blast furnace, in which the upper surface of the charge to the blast furnace is lowered to below the deposits, exposing the deposits, and then watering the exposed deposits to remove them. In this method, it is preferable to perform intermittent water spraying with intervals between water sprays, and to adjust the water spray time per spray, the interval time, the water spray flow rate, and the total water spray amount to maintain a specified furnace heat level, and to remove the deposits. This is a method for operating a blast furnace, which includes a step of reducing the amount of charge to the blast furnace to below the deposits during operation or during a cessation of air flow, and removing the deposits on the furnace walls by the above-mentioned method for removing deposits on the walls of a blast furnace. [Selected Figure] Figure 1

Description

The present invention relates to a method for removing deposits adhering to the walls of a blast furnace and a method for operating a blast furnace. In this specification, the unit "t" representing mass represents 1000 kg.

The mechanism by which the deposits that adhere to the walls of a blast furnace are formed is thought to be as follows. First, alkalis such as Zn (zinc) and Na (sodium) contained in the ore evaporate in the lower part of the blast furnace, where the temperature is high, and condense on relatively low-temperature parts such as the shaft and the furnace wall near the throat. This condensate acts as a binder to solidify the ore and coke that are charged, forming a strong deposit.

When this deposit grows on the furnace wall, the shape of the furnace interior becomes distorted and the gas flow inside the furnace becomes unstable. This leads to poor lowering of the contents inside the furnace and poor ventilation inside the furnace, which in turn reduces the productivity of the blast furnace. On the other hand, if the deposit collapses, the furnace temperature drops due to a lack of heat caused by the remelting of the deposit. This leads to a deterioration in the coke rate and ultimately a decrease in productivity.

For these reasons, when operating a blast furnace, the amount of zinc and alkalis in the raw material charge has been strictly restricted in order to reduce the amount of zinc, alkali, and other substances circulating within the furnace, or deposits on the furnace walls have been removed.

Conventional methods for removing deposits involve reducing the size of the raw material charge during shutdowns or during operation, allowing the deposits to cool and cause a thermal shock, which then peels off and removes them. Patent Document 1 also discloses a method in which the charge is either left in the mine or reduced in size and then blasted with explosives such as dynamite to remove the deposits.

Patent Document 2 also discloses a method of detecting adhesions, reducing the size of the charged materials, suspending airflow, and blowing in gas as a refrigerant to cool the materials, causing a sudden change in the physical properties of the adhesions, such as thermal expansion, to cause cracks and allow the adhesions to fall off and be removed. Patent Document 3 also discloses a method of detecting the occurrence of adhesions, reducing the size and suspending airflow, and then removing the adhesions by colliding the charged materials with the adhesions when operation is resumed.

Japanese Patent Publication No. 42-026377 Japanese Patent Application Laid-Open No. 54-033808 Japanese Patent Application Laid-Open No. 55-115903

However, the above-mentioned conventional techniques have the following problems.
First, strictly restricting the zinc and alkali content in the raw material charge in the conventional method narrows the range of raw material choices and leads to a rise in product prices, making it economically difficult to adopt. Also, simply leaving the deposits to cool has the problem that the amount of material that peels off is small and the effect is small. In particular, the time required for reduction during operation is short, so the effect of removing the deposits is small.

In addition, although the method described in Patent Document 1 is effective in terms of removing deposits, there is a high risk of damage to surrounding equipment, such as the furnace body, such as the iron shell and bricks, due to the blast.

The techniques described in Patent Documents 2 and 3 are based on the premise that the furnace is shut down, and are not intended to be applied during operation. Shutting down the furnace is done once every few months, and the frequency is limited, which raises the risk of causing the deposits to thicken. In addition, the gas cooling method described in Patent Document 2 has a small heat capacity, and there is an issue that it takes a long time for the cooling effect to be exerted. Furthermore, when cooling using air, unless the combustible gas in the furnace is replaced with a non-combustible gas during the shut down, there is a risk of explosion, and therefore it cannot be applied during operation.

In addition, the method described in Patent Document 3 in which the charge material is collided with the attached material has the risk of the charge material colliding with the bricks and damaging them after the attached material is removed.

The present invention was made in consideration of the above-mentioned problems of the conventional technology, and its purpose is to propose a method for removing deposits from the furnace walls of a blast furnace and an operating method that can effectively remove deposits from the furnace walls during cessation of blowing and operation.

The inventors discovered that deposits can be removed efficiently by exposing them and then spraying water under appropriate conditions to cool them.

The method for removing deposits from the walls of a blast furnace according to the present invention, which advantageously solves the above problem, is characterized by lowering the top surface of the charge into the blast furnace to the bottom of the deposits, exposing the deposits, spraying water on the exposed deposits, and removing the deposits.

The method for removing deposits from a blast furnace wall according to the present invention is as follows:
a. The watering is performed intermittently with an interval between waterings;
b. In the water spraying, the water spraying time, interval time, water spray flow rate and total water spray amount are adjusted so as to maintain a predetermined furnace heat level, and the deposits are removed;
c. The water is sprayed in a number of times, with each spray time in the range of 30 to 120 seconds, the interval between sprays in the range of 60 to 240 seconds, the water spray flow rate per ¹ m3 of furnace volume in the range of 8 to 23 kg/h, and the total amount of water sprayed per ¹ m3 of furnace volume in the range of 13 to 39 kg, thereby removing the deposits;
would be a more preferable solution.

The method of operating a blast furnace according to the present invention, which advantageously solves the above problems, is characterized by including a deposit removal step in which, during operation or during cessation of operation, the charge into the blast furnace is reduced to the bottom of the deposits, and the deposits on the furnace walls are removed by any of the above-mentioned methods for removing deposits on the blast furnace walls.

The blast furnace operating method according to the present invention further includes a step of detecting deposits on the walls of the blast furnace, and when the deposition of the deposits on the walls of the blast furnace is detected, a more preferable solution is to carry out the deposit removal step.

According to the present invention, the adhesions can be removed not only during the shutdown period but also during operation, which has resolved the problems mentioned above. In addition, by reducing the length, it has become possible to remove adhesions from the shaft section.

FIG. 1 is a schematic cross-sectional view showing an upper vertical section of a blast furnace. 2A and 2B are diagrams showing an example of water spray conditions according to an embodiment of the present invention, in which FIG. 2A is a schematic cross-sectional view taken along the line XX in FIG. 1, and FIG. 2B is a diagram showing a water spray pattern. 1A is a schematic cross-sectional view taken along the line XX in FIG. 1; and FIG. 1B is a diagram showing a water spray pattern.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 is a schematic sectional view showing an upper vertical section of a blast furnace to which a method for removing deposits from a blast furnace wall according to the present invention is suitable.
The blast furnace 1 according to this embodiment is a facility for producing pig iron and ferromanganese using iron ore and manganese ore as the main raw materials. It is particularly suitable for application to a blast furnace 1 that produces ferromanganese using manganese ore as the raw material. The furnace wall deposits 6 of a blast furnace 1 using manganese ore as the raw material are characterized by having a high Na (sodium) and K (potassium) content and a low Zn (zinc) content. Therefore, the deposits of a blast furnace using manganese ore as the raw material have a large hydration expansion of Na ₂ O and K ₂ O.

In the method for removing deposits from the furnace wall of a blast furnace according to this embodiment, the detection of the occurrence of the deposits 6 is not particularly limited, but it is preferable to detect the occurrence of the deposits 6 adhering to the furnace wall 2 in the vicinity of the furnace throat 3 by any of the following methods.
(1) The load S inside the blast furnace 1 is reduced in size 7, that is, lowered from the load level SL0 before reduction to the load level SL after reduction, and the inner surface of the furnace wall 2 is observed visually or by photographic images to directly grasp, for example, the height and thickness of the deposits 6 on the water-cooled shaft stave 5.
(2) Detecting the occurrence of deposits 6 on the furnace wall 2 from the circumferential temperature difference and the change in temperature over time measured by a thermometer installed outside the furnace body.
(3) The occurrence of deposits 6 is detected from a change in temperature of the cooling water that cools the furnace body.

In this embodiment, for example, in order to compensate for the temperature of the blast furnace 1 decreasing due to the water spray 4A from the water spray nozzle 4 during operation, the operating temperature is set higher than usual in advance, and the upper surface of the furnace load S (charge level SL) is lowered to the bottom of the deposits 6 on the furnace wall 2 to expose the deposits 6. Water is then sprayed on the exposed deposits 6 under specified conditions. The deposits 6 are then removed 8 by cracks that occur in the deposits 6 due to differences in thermal expansion caused by cooling, and the progression of the cracks mainly due to hydration expansion caused by the reaction between water that has entered through the cracks and alkali. It is also possible to spray water during the reduction and cooling period. A similar effect of removing deposits can be obtained.

In the water sprinkling method of this embodiment, it is preferable to provide intermittent water sprinkling 4A for a predetermined time ts and an interval time ti during which no water sprinkling is performed between each water sprinkling. By providing an interval time ti, the deposit 6 is more likely to crack due to contraction caused by cooling caused by the water sprinkling and expansion caused by reheating. It is also preferable to adjust the water sprinkling conditions to keep the furnace heat level of the blast furnace 1 within a predetermined range. Here, the furnace heat level of the blast furnace 1 is evaluated using the operating temperature of the blast furnace 1 and the component fluctuations of the product. By keeping the operating temperature of the blast furnace 1 within a predetermined range, it is possible to keep the concentration fluctuations of the product, such as Si, a component of ferromanganese, within a predetermined range.

The water spray time ti per time is preferably in the range of 30 to 120 s. Below the lower limit, the effect of removing the deposits 6 may be too small. Above the upper limit, the furnace heat may be lowered too much, and hydrogen gas may be generated by the water-gas reaction. The interval time ti is preferably in the range of 60 to 240 s. Below the lower limit, the furnace heat may not be fully restored. Above the upper limit, it may take a long time to completely remove the deposits 6. The interval time ti is preferably about twice the water spray time ts. The furnace heat can be restored and thermal shock to the deposits 6 can be expected. The water spray flow rate per ¹ m3 of furnace volume is preferably in the range of 8 to 23 kg/h. Below the lower limit, the effect of removing the deposits may be too small. Above the upper limit, the furnace heat may be lowered too much, and hydrogen gas may be generated by the water-gas reaction. The total amount of water sprayed per ¹ m3 of furnace volume is preferably in the range of 13 to 39 kg. Below the lower limit, there is a concern that the deposits 6 may not be completely removed. If the upper limit is exceeded, the furnace heat may be too low, which increases the reducing agent rate and increases the silicon concentration, hindering the stability of operation.

The sprinkler nozzle 4 according to the present embodiment can be arranged as a single nozzle that can adjust the direction of the water spray 4A toward the deposits 6, or as a plurality of nozzles arranged in the circumferential direction of the furnace throat 3. The plurality of sprinkler nozzles 4 arranged in the circumferential direction of the furnace throat 3 can uniformly and efficiently remove deposits by spraying water one by one or in sequence, with the order of spraying water being determined in advance.
FIG. 1 shows the arrangement of the sprinkler nozzles 4 aimed at the deposits 6 on the furnace wall 2. FIG. 2(a) is a schematic diagram showing eight sprinkler nozzles 4 arranged at equal intervals on the furnace throat 3 as seen in the X-X cross section of FIG. 1. The sprinkler order 4B is indicated by italicized numbers. FIG. 2(b) is a pattern diagram showing the manner in which the sprinkler nozzles 4 are continuously sprinkled in a clockwise direction with interval times ti aimed at deposits at predetermined locations. In this way, water can be sprinkled evenly, and the deposits can be removed uniformly and efficiently. In FIG. 2(b), ts represents the sprinkler time, and ta represents the total sprinkler time. Water is sprinkled during the periods shaded in black in the pattern diagram.

Also, if there is an attachment 6 on a part of the furnace wall 2, a water spray nozzle 4 can be selected to target it and used for water spray 4A. Figure 3(a) shows that water spray nozzles C and G are not used because there is no attachment 6 in the opposing position, and water spray nozzles A, B, D, E, F, and H are selected. Figure 3(b) shows an example in which water spray nozzles 4 are used to target attachment 6 in a predetermined location in an opposing position, with an interval time ti that is twice the water spray time ts. In this way, attachment 6 unevenly distributed on the furnace wall 2 can be removed uniformly and efficiently.

The method of operating a blast furnace according to this embodiment includes a step of reducing the amount of material charged to the blast furnace to below the deposits during operation or during refueling, and removing the deposits attached to the furnace wall by the furnace wall deposit removal method. The removed deposits descend into the blast furnace together with the charged materials such as raw materials. The raw material components in the deposits are dissolved as they are in the lower part of the furnace. The volatile components in the deposits, such as alkali, are gasified and rise. Some of the gasified components are captured by the raw materials and circulated within the furnace. The rest are discharged to the outside of the system as dust, etc.

The blast furnace operating method according to this embodiment includes a step of detecting deposits on the walls of the blast furnace, and it is preferable to execute the deposit removal step when the deposition of deposits on the walls of the blast furnace is detected. The above-mentioned three methods (1) to (3) are exemplified for detecting deposits.

Example 1
A blast furnace with an internal volume of ⁴⁵⁰ m3 was used, and eight dedicated water sprinkler nozzles for removing deposits from the furnace walls were installed around the circumference of the furnace body. The direction of the water sprinkler nozzles was adjusted so that they could sprinkle water on the deposits, and the pipe diameter of the water sprinkler nozzle was selected to satisfy the water sprinkler flow rate below. A single-pipe nozzle was selected for the water sprinkler nozzle so that its direction would not change depending on the wind speed inside the furnace, and the following checks were performed.

Detection of adhesions on the furnace walls inside a blast furnace was carried out by a furnace body thermometer installed in the furnace body, or by changes in the temperature of the cooling water installed in the furnace body. In addition, whether the adhesions had been removed was determined by changes in the temperature measured by the furnace body thermometer, or by changes in the temperature of the cooling water. If the adhesions could not be removed, there would be no change in temperature, and if the adhesions were removed, the measured temperature would rise. In this example, detection was carried out by changes in the temperature of the cooling water installed in the furnace body.

The amount of deposits on the furnace body was estimated to be 5.8 t based on the change in the furnace body cooling water temperature. In this state, during a cooling off period, the top surface of the charge in the blast furnace was lowered to the bottom of the deposits, exposing the deposits. Each nozzle sprayed water for 60 s at a spray flow rate of 8 t/h. At this time, the interval time for each nozzle was 420 s. After two hours of spraying water, the estimated amount of deposits was reduced to 0.6 t. In other words, the removal of approximately 90% of the deposits was confirmed.

<Comparative Example 1>
Using the same equipment as in Example 1, the scale was reduced when the wind was turned off and the deposits were left to cool for about 24 hours without spraying water. The thermal shock removed about 40% of the deposits.

<Comparative Example 2>
Using the same equipment as in Example 1, the scale was reduced during operation while the deposits were still attached, and the deposits were left to cool for about 5 hours without spraying water. The thermal shock achieved the effect of removing about 30% of the deposits.

Example 2
Using the same equipment as in Example 1, the amount of deposits inside the furnace was estimated to be 9.7 t based on the furnace body cooling water temperature. Under this condition, the furnace was scaled down during operation, and intermittent water spraying was performed for 5 hours toward the deposits. The water spraying conditions were 60 s of water spraying followed by an interval of 120 s. The water spray flow rate was 10 t/h. The total amount of water sprayed was approximately 17 t. As a result, the estimated amount of deposits could be reduced to 1.0 t. As in Example 1, the effect of removing 90% of the deposits was confirmed.

Example 3
Using the same equipment as in Example 1, the amount of deposits inside the furnace was estimated to be 6.8 t based on the furnace body cooling water temperature. Under this condition, the furnace was scaled down during operation, and intermittent water spraying was performed for 1 hour toward the deposits. The water spraying conditions were 50 s of water spraying followed by an interval of 120 s. The water spray flow rate was 8 t/h. The total amount of water sprayed was approximately 3 t. As a result, the estimated amount of deposits could be reduced to 4.1 t. The effect of removing approximately 40% of the deposits was confirmed.

Example 4
Using the same equipment as in Example 1, the amount of deposits inside the furnace was estimated to be 7.9 t based on the furnace body cooling water temperature. Under this condition, the furnace was scaled down during operation, and intermittent water spraying was performed on the deposits for 3 hours. The water spraying conditions were 45 s of water spraying followed by an interval of 120 s. The water spray flow rate was 6 t/h. The total amount of water sprayed was approximately 5 t. As a result, the estimated amount of deposits could be reduced to 4.0 t. The effect of removing approximately 50% of the deposits was confirmed.

Example 5
When water is sprayed inside the furnace, the temperature of the raw materials and molten material in the furnace may drop, which may result in a drop in furnace heat. It was thought that it was necessary to prevent the water-gas reaction, which is an endothermic reaction, from occurring. Therefore, the exhaust gas analysis of the blast furnace was carried out continuously to determine the water spraying conditions that would not generate hydrogen gas associated with the water-gas reaction. Using the same equipment as in Example 1, the preferable conditions were confirmed by spraying water from one of the eight nozzles. The results are shown in Table 1.

The water spray time and water spray flow rate were gradually increased, and under conditions where hydrogen gas was generated, the water spray flow rate was lowered to test whether hydrogen gas was generated. It was found that water could be sprayed without generating hydrogen gas if the water spray time was 120 seconds or less and the water spray flow rate was 10 t/h or less. Since the water spray flow rate at which the furnace heat is reduced varies depending on the furnace volume, it was found that the water spray flow rate for ¹ m3 of furnace volume is preferably 23 kg/h or less.

Example 6
Next, a test was conducted to determine the watering conditions for efficiently removing the deposits, that is, the watering time and watering flow rate. Using the same equipment as in Example 1, six of the eight removal watering nozzles were used to spray water for a total of one hour each, and the removal effect was confirmed under the six conditions in Table 2. The test was conducted in the following order: treatment No. 1 was performed for one hour, then treatment No. 2 was performed for one hour, and finally treatment No. 6 was performed for one hour. The determination of whether the deposits were removed was made by checking the change in the furnace body temperature measured by a thermocouple installed in the furnace body. In other words, if the deposits could not be removed, the temperature was judged to be "none", and if the deposits were removed, the temperature was judged to be "increased". The interval time was fixed at twice the watering time.

In all of the treatments No. 1 to 6, no hydrogen gas was generated due to the water-gas reaction. From the results in Table 2, it was found that in order to remove the deposits, it is necessary to ensure that the water spray time is 30 seconds or more and the water spray flow rate is 4 t/h or more. Therefore, it was found that the water spray flow rate per ¹ m3 of furnace volume is preferably 8 kg/h or more.

The method for removing deposits from the walls of a blast furnace and the operating method of the present invention are highly effective when applied to blast furnaces, particularly those that use manganese ore as a raw material, and are industrially useful because they improve productivity.

1 Blast furnace 2 Furnace wall 3 Furnace mouth 4 Sprinkler nozzle 4A Sprinkler 4B Sprinkler order 5 (Water-cooled) shaft stave 6 (Furnace wall) deposit 7 Reduction in length 8 (Deposition) falling off/removal S (Inside furnace) Charge SL Charge level SL0 (after reduction) Charge level ts (before reduction) Sprinkler time ti Interval time ta Total water spray time

Claims (6)

A method for removing deposits from the walls of a blast furnace, which involves lowering the top surface of the material being charged to the blast furnace to the bottom of the deposits, exposing the deposits, and spraying water on the exposed deposits to remove them. The method for removing deposits from the walls of a blast furnace according to claim 1, wherein the water spraying is performed intermittently with intervals between sprays. The method for removing deposits from the walls of a blast furnace as described in claim 2, in which the water spraying time, interval time, water spray flow rate, and total water spray amount are adjusted to maintain a predetermined furnace heat level, and the deposits are removed. The method for removing deposits on a furnace wall of a blast furnace according to claim ³ , wherein the water is sprayed in a plurality of times, the water spray time is in the range of 30 to 120 seconds, the interval time between water sprays is in the range of 60 to 240 seconds, the water spray flow rate per ¹ m3 of furnace volume is in the range of 8 to 23 kg/h, and the total amount of water sprayed per 1 m3 of furnace volume is in the range of 13 to 39 kg, thereby removing the deposits. A method for operating a blast furnace, comprising a step of reducing the amount of material charged to the blast furnace to below the deposits during operation or during cessation of operation, and removing the deposits from the furnace walls by a method for removing deposits from the furnace walls of a blast furnace as described in any one of claims 1 to 4. Further, the method includes a step of detecting deposits on a wall of the blast furnace,
6. The method for operating a blast furnace according to claim 5, further comprising the step of: executing the deposit removing step when adhesion of the deposit to a furnace wall inside the blast furnace is detected.

Images