Method for removing deposit on furnace wall of blast furnace and method for operating blast furnace

Abstract

The present invention provides a method for removing a deposit on a furnace wall of a blast furnace and a method for operating a blast furnace. In the method for removing a deposit on a furnace wall of a blast furnace, the upper surface of the material loaded into the blast furnace is lowered to the lower part of the deposit to expose the deposit, and water is sprayed onto the exposed deposit to remove the deposit. In this method, it is preferable to intermittently spray water by providing an interval between each spraying of water, and to remove the deposit while adjusting water spraying time, interval time, water spraying flow rate and total water spraying amount per spray so as to maintain a predetermined furnace heat level. The method for operating a blast furnace comprises a deposit removal step in which, during operation or when idle, the material loaded into the furnace is reduced to the lower part of the deposit and the deposit on the furnace wall is removed by the aforementioned method for removing a deposit on a furnace wall of a blast furnace.

Description

Method for removing deposits on the wall of a blast furnace and method for operating a blast furnace

[0001] The present invention relates to a method for removing deposits adhering to furnace walls in a blast furnace and a method for operating a blast furnace.In this specification, the unit "t" representing mass represents 1000 kg.

[0002] The mechanism by which deposits adhere to the walls of a blast furnace 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 charged, forming a strong deposit.

[0003] If this deposit grows on the furnace wall, the shape of the furnace becomes distorted, causing the gas flow inside the furnace to become unstable. This leads to poor loading 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 required to remelt the deposit. This leads to a deterioration in the coke rate and ultimately to a decrease in productivity.

[0004] For these reasons, in the operation of a blast furnace, in order to suppress the amount of zinc, alkalis, etc. circulating in the furnace, the content of zinc and alkalis in the raw material charge has been strictly limited, or deposits on the furnace walls have been removed.

[0005] In a conventional method for removing deposits, the raw material charge is reduced during cooling periods or during operation, and the deposits are allowed to cool, causing a thermal shock, which peels them off and removes them. Patent Document 1 also discloses a method for removing deposits by blasting them with explosives such as dynamite, either while the charge is still in place or after it has been reduced.

[0006] Patent Document 2 discloses a method for detecting deposits, reducing the size of the charged materials, suspending airflow, and blowing gas as a refrigerant to cool the deposits, thereby rapidly changing the physical properties of the deposits, such as thermal expansion, to cause cracks and allow the deposits to fall off and be removed. Patent Document 3 discloses a method for detecting the occurrence of deposits, reducing the size and suspending airflow, and then, when returning to operation, causing the charged materials to collide with the deposits to remove them.

[0007] JP-A-42-026377, JP-A-54-033808, JP-A-55-115903

[0008] However, the above-mentioned conventional techniques have the following problems. First, strict restrictions on the zinc and alkali content in the raw material charge in the conventional method narrow the range of raw material choices and lead to higher product prices, making it economically unfeasible. Also, simply allowing the deposits to cool results in a small amount of material being removed, resulting in little effect. In particular, the reduction in length during operation is short, so the effect of removing the deposits is small.

[0009] Furthermore, although the method described in Patent Document 1 is effective in terms of removing deposits, there is a high risk of damaging surrounding equipment, such as the furnace body, including the iron shell and bricks, due to the explosion.

[0010] Furthermore, the techniques described in Patent Documents 2 and 3 are based on the premise that the furnace is halted from operation, and are not intended to be applied during operation. The halt of operation is performed once every few months, which limits the frequency and risks causing the buildup of deposits. Furthermore, the gas cooling method described in Patent Document 2 has a problem in that it has a small heat capacity and takes a long time to achieve its cooling effect. Furthermore, when cooling using air, unless the combustible gas in the furnace is replaced with a non-combustible gas during the halt of operation, there is a risk of explosion, and therefore the method cannot be applied during operation.

[0011] Furthermore, in the method of causing the charge material to collide with the deposits described in Patent Document 3, there is a risk that the charge material will collide with the bricks and be damaged after the deposits have been removed.

[0012] The present invention has been made in consideration of the above-mentioned problems of the prior art, and its object 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 ventilating periods and during operation.

[0013] The inventors have found that deposits can be efficiently removed by exposing the deposits and then cooling them with water spray under appropriate conditions.

[0014] The method for removing deposits on the walls of a blast furnace according to the present invention, which advantageously solves the above-mentioned problems, is characterized by lowering the upper surface of the charge into the blast furnace to the bottom of the deposits, exposing the deposits, and spraying water on the exposed deposits to remove them.

[0015] The method for removing deposits on the furnace wall of a blast furnace according to the present invention comprises the steps of: a. providing an interval between water sprays and spraying water intermittently; b. adjusting the water spray time, interval time, water spray flow rate and total water spray amount per water spray so as to maintain a predetermined furnace heat level, and removing the deposits; c. performing the water spraying in multiple steps, with the water spray time in the range of 30 to 120 seconds and the water spray interval time in the range of 60 to 240 seconds, and ３ The water spray flow rate is set to the range of 8 to 23 kg / h, and the furnace volume is set to 1 m ３ A more preferable solution is to remove the deposits by setting the total amount of water sprayed to the range of 13 to 39 kg.

[0016] The method of operating a blast furnace according to the present invention, which advantageously solves the above-mentioned problems, is characterized by including a deposit removal step in which, during operation or during a cessation of airflow, the charge into the blast furnace is reduced to below the deposits, and the deposits on the furnace wall are removed by any of the above-mentioned methods for removing deposits on the furnace wall.

[0017] In addition, the method for operating a blast furnace according to the present invention further includes a step of detecting deposits on the furnace wall of the blast furnace, and when the deposition of the deposits on the furnace wall inside the blast furnace is detected, the deposit removal step is carried out, which is a more preferable solution.

[0018] According to the present invention, the deposits can be removed not only during the shutdown period but also during operation, which has resolved the above-mentioned problems. In addition, by reducing the length, it has become possible to remove deposits on the shaft.

[0019] 1A is a schematic cross-sectional view showing an upper vertical cross section of a blast furnace. It is a diagram showing an example of water sprinkling conditions according to an embodiment of the present invention, where (a) is a schematic cross-sectional view taken along line X-X in FIG. 1, and (b) is a diagram showing a water sprinkling pattern. It is a diagram showing another example of water sprinkling conditions according to the above embodiment, where (a) is a schematic cross-sectional view taken along line X-X in FIG. 1, and (b) is a diagram showing a water sprinkling pattern.

[0020] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an upper vertical section of a blast furnace suitable for applying the method for removing deposits from a blast furnace wall according to the present invention. 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 material. In particular, it is suitable for application to a blast furnace 1 that produces ferromanganese using manganese ore as the raw material. The deposits 6 on the furnace wall of a blast furnace 1 using manganese ore as the raw material are characterized by being high in Na (sodium) and K (potassium) content and low in Zn (zinc). Therefore, the deposits on a blast furnace using manganese ore as the raw material are characterized by being high in Na (sodium) and K (potassium) content and low in Zn (zinc). ２ O and K ２ O has a large hydration expansion.

[0021] In the method for removing deposits on the furnace wall of a blast furnace according to this embodiment, the detection of the occurrence of deposits 6 is not particularly limited, but it is preferable to detect the occurrence of deposits 6 on the furnace wall 2 near the furnace throat 3 by one of the following methods: (1) By reducing the size 7 of the charge S inside the blast furnace 1, that is, by lowering it from the charge level SL0 before reduction to the charge level SL after reduction, the inner surface of the furnace wall 2 is observed visually or by photographic images, and the height and thickness of the deposits 6 on the water-cooled shaft stave 5 are directly grasped, for example. (2) The occurrence of deposits 6 on the furnace wall 2 is detected from the circumferential temperature difference of a thermometer installed outside the furnace body or the change in temperature over time. (3) The occurrence of deposits 6 is detected from the temperature change of the cooling water that cools the furnace body.

[0022] In this embodiment, for example, to compensate for the temperature drop of the blast furnace 1 due to the water spray 4A from the water spray nozzles 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, exposing the deposits 6. Water is then sprayed onto the exposed deposits 6 under predetermined conditions. The deposits 6 are then removed 8 by cracks that develop in the deposits 6 due to differences in thermal expansion caused by cooling, and by the propagation of cracks due mainly to hydration expansion caused by the reaction between water that penetrates through the cracks and alkalis. Water spraying can also be performed during a scale reduction / outage. A similar deposit removal effect can be achieved.

[0023] In the water sprinkling method of this embodiment, it is preferable to sprinkle water intermittently by providing a predetermined time ts of water sprinkling 4A and an interval time ti during which no water sprinkling is performed between water sprinkles. By providing an interval time ti, cracks are more likely to occur in the deposits 6 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.

[0024] The water spray time ts per time is preferably in the range of 30 to 120 seconds. Below the lower limit, the effect of removing the deposits 6 may be too small. Above the upper limit, the furnace heat may be reduced 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 seconds. Below the lower limit, the furnace heat may not be sufficiently 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. This is expected to restore the furnace heat and cause a thermal shock to the deposits 6. Furnace volume 1 m ３ The water spray flow rate is preferably in the range of 8 to 23 kg / h. Below the lower limit, the effect of removing deposits may be too small. Above the upper limit, the furnace heat may be too low, and hydrogen gas may be generated by the water-gas reaction.３ It is preferable that the total amount of water sprayed relative to the total amount of water is in the range of 13 to 39 kg. Below the lower limit, there is a concern that some of the deposits 6 may not be removed. Above the upper limit, there is a risk that the furnace heat will be reduced too much. A reduction in furnace heat increases the reducing agent rate, which increases the Si concentration and impairs the stability of operation.

[0025] In this embodiment, the sprinkler nozzle 4 can be arranged as a single nozzle with the spray 4A adjustable toward the deposit 6, or multiple nozzles can be arranged circumferentially around the furnace throat 3. The multiple sprinkler nozzles 4 arranged circumferentially around the furnace throat 3 can be sprayed one by one or multiple by multiple in a predetermined spray order, allowing for uniform and efficient removal of deposits. Figure 1 shows the arrangement of sprinkler nozzles 4 aimed at deposits 6 on the furnace wall 2. Figure 2(a) is a schematic diagram showing eight sprinkler nozzles 4 evenly spaced around the furnace throat 3 as viewed from the X-X cross section of Figure 1. The italicized numbers indicate the spray order 4B. Figure 2(b) is a pattern diagram showing the sprinkler nozzles 4 continuously spraying water in a clockwise direction, with intervals ti set, targeting deposits in predetermined locations. This allows for even spraying of water, resulting in uniform and efficient removal of deposits. In Figure 2(b), ts represents the spray time, and ta represents the total spray time. Watering is carried out during the periods marked in black on the pattern diagram.

[0026] Furthermore, if there is an attachment 6 on a part of the furnace wall 2, a sprinkler nozzle 4 can be selected to target that part and provide the sprinkler 4A. Figure 3(a) shows a state in which sprinkler nozzles A, B, D, E, F, and H are selected, while sprinkler nozzles C and G are not used because there is no attachment 6 in the opposing position. Figure 3(b) shows an example in which sprinkler nozzles 4 are used to target attachment 6 in a predetermined location opposite the attachment 6, with an interval time ti set that is twice the sprinkler time ts. This allows attachment 6 unevenly distributed on the furnace wall 2 to be removed uniformly and efficiently.

[0027] The method for operating a blast furnace according to this embodiment includes a deposit removal step in which, during operation or during refueling, the charge material to the blast furnace is reduced to below the deposits, and the deposits adhering to the furnace wall are removed by the above-described method for removing deposits on the furnace wall. The removed deposits descend into the blast furnace together with the charge material, such as raw materials. The raw material components in the deposits are dissolved as they are in the lower part of the furnace. Volatile components, such as alkalis, in the deposits are gasified and rise. Some of the gasified components are captured by the raw materials and circulate within the furnace. The rest are discharged to the outside of the system as dust or the like.

[0028] The method for operating a blast furnace according to this embodiment preferably includes a step of detecting deposits on the walls of the blast furnace, and when the deposition of deposits on the walls of the blast furnace is detected, the deposit removal step is preferably carried out. The above-mentioned three methods (1) to (3) are exemplified for detecting deposits.

[0029] Example 1: Internal volume 450 m ３ A blast furnace was used, and eight dedicated sprinkler nozzles for removing deposits from the furnace walls were installed around the circumference of the furnace body. The direction of the sprinkler nozzles was adjusted so that they could spray water onto the deposits, and the pipe diameter of the sprinkler nozzle was selected to satisfy the following sprinkler flow rate. A single-pipe nozzle was selected for the sprinkler nozzle so that its direction would not change depending on the wind speed inside the furnace, and the following checks were carried out.

[0030] The detection of deposits on the furnace walls inside the blast furnace was carried out by a furnace thermometer installed in the furnace body or by detecting changes in the temperature of the cooling water installed in the furnace body. Whether the deposits had been removed was also confirmed by checking the change in the temperature measured by the furnace thermometer or the change in the temperature of the cooling water. If the deposits could not be removed, there would be no change in temperature, and if the deposits had been removed, the measured temperature would rise. In this example, detection was carried out by checking the change in the temperature of the cooling water installed in the furnace body.

[0031] Based on the change in the furnace body cooling water temperature, it was estimated that the mass of deposits on the furnace body was 5.8 t. In this state, during a refrigeration stop, the top surface of the charge in the blast furnace was lowered to the bottom of the deposits, exposing them. Each nozzle was sprayed for 60 seconds at a spray flow rate of 8 t / h. The interval time per nozzle was 420 seconds. After two hours of spraying, the estimated amount of deposits was reduced to 0.6 t. In other words, the removal effect of approximately 90% of the deposits was confirmed.

[0032] Comparative Example 1 Using the same equipment as in Example 1, the scale was reduced when the wind was stopped and the deposits were left to cool for about 24 hours without spraying water. The thermal shock was effective in removing about 40% of the deposits.

[0033] Comparative Example 2 Using the same equipment as in Example 1, the scale was reduced during operation with deposits still attached, and the deposits were allowed to cool for about 5 hours without spraying water. Thermal shock achieved a removal effect of about 30% of the deposits.

[0034] 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 reduced in size during operation, and intermittent water spraying was performed for 5 hours on the deposits. The water spraying conditions were a 60-second water spray followed by a 120-second interval. The water spray flow rate was 10 t / h. The total amount of water sprayed was approximately 17 t. As a result, the estimated deposit amount was reduced to 1.0 t. As in Example 1, 90% of the deposit removal effect was confirmed.

[0035] 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 reduced in size during operation, and intermittent water spraying was performed for one hour toward the deposits. The water spraying conditions were a 50-second water spray followed by a 120-second interval. The water spray flow rate was 8 t / h. The total amount of water sprayed was approximately 3 t. As a result, the estimated deposit amount was reduced to 4.1 t. The effect of removing approximately 40% of the deposits was confirmed.

[0036] 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 reduced in size during operation, and intermittent water spraying was performed for 3 hours toward the deposits. The water spraying conditions were a 45-second water spray followed by a 120-second interval. The water spray flow rate was 6 t / h. The total amount of water sprayed was approximately 5 t. As a result, the estimated deposit amount was reduced to 4.0 t. The effect of removing approximately 50% of the deposits was confirmed.

[0037] <Example 5> When water is sprayed inside the furnace, the temperature of the raw materials and molten material inside the furnace may drop, resulting in a decrease in furnace heat. It was thought necessary to prevent the water-gas reaction, which is an endothermic reaction. Therefore, continuous analysis of the exhaust gas from the blast furnace was carried out to determine the water spraying conditions that would prevent the generation of 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 pipes. The results are shown in Table 1.

[0038]

[0039] 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 reduced to test whether or not hydrogen gas was generated. It was found that water spraying was possible 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. The water spray flow rate at which the furnace heat would decrease varies depending on the furnace volume, so it was tested for a furnace volume of 1 m ３ It was found that the water spray flow rate is preferably 23 kg / h or less.

[0040] Example 6 Next, a test was conducted to determine the watering conditions for efficient removal of deposits, i.e., the watering time and watering flow rate. Using the same equipment as in Example 1, six of the eight removal watering nozzles were used, and water was sprayed from each nozzle for a total of one hour. The removal effect was confirmed under each of the six conditions shown in Table 2, Treatment Nos. 1 to 6. The test was conducted in the following order: Treatment No. 1 was performed for one hour, followed by Treatment No. 2 for one hour, and finally Treatment No. 6 for one hour. The success or failure of the deposits was determined by checking the change in furnace body temperature measured using a thermocouple installed in the furnace body. In other words, if the deposits could not be removed, the temperature was judged to be "no change," and if the deposits were removed, the temperature was judged to be "increased." The interval time was fixed at twice the watering time.

[0041]

[0042] 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 was necessary to ensure that the water spray time was 30 seconds or more and the water spray flow rate was 4 t / h or more. For this reason, it was necessary to ensure that the furnace volume was 1 m ３ It was found that the water spray flow rate is preferably 8 kg / h or more. Industrial application fields

[0043] The method for removing deposits from the wall of a blast furnace and the operating method thereof according to the present invention are highly effective when applied to blast furnaces, particularly blast furnaces that use manganese ore as their raw material, and are industrially useful because they improve productivity.

[0044] 1 Blast furnace 2 Furnace wall 3 Furnace throat 4 Sprinkler nozzle 4A Sprinkler 4B Sprinkler order 5 (Water-cooled) shaft stave 6 (Furnace wall) Deposit 7 Reduction 8 (Deposit) Falling off / removal S (Inside furnace) Charge SL Charge level (after reduction) SL0 Charge level (before reduction) ts Sprinkler time ti Interval time ta Total spraying time

Claims

1. A method for removing deposits from the walls of a blast furnace, comprising lowering the top surface of the material being charged into the blast furnace to the bottom of the deposits, exposing the deposits, and spraying water on the exposed deposits to remove them.

2. A method for removing deposits on the walls of a blast furnace as set forth in claim 1, wherein the water spraying is performed intermittently by providing intervals between sprays.

3. A method for removing deposits on 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 remove the deposits.

4. The watering is carried out in multiple steps, with the watering time in the range of 30 to 120 seconds, the interval between watering in the range of 60 to 240 seconds, and the furnace volume of 1 m ３ The water spray rate is set to 8 to 23 kg / h, and the furnace volume is set to 1 m ３ The method for removing deposits on a blast furnace wall according to claim 3, wherein the deposits are removed by setting a total amount of water sprayed on the furnace wall in the range of 13 to 39 kg.

5. A method for operating a blast furnace, comprising a step of reducing the charge 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 blast furnace walls as claimed in any one of claims 1 to 4.

6. A method for operating a blast furnace as claimed in claim 5, further comprising a step of detecting deposits on a furnace wall of the blast furnace, and when the deposition of said deposits on the furnace wall of the blast furnace is detected, said deposit removal step is carried out.

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