Method for removing deposits from the walls of a smelting furnace and method for operating a smelting furnace

Abstract

A method for removing deposits from the walls of a smelting furnace and a method for operating a smelting furnace are proposed. The method for removing deposits from the walls of a smelting furnace, in which the upper surface of the charge loaded into the smelting furnace is lowered to the lower part of the deposits, the deposits are exposed, and water is sprayed on the exposed deposits to remove the deposits. The method is preferably adjusted in such a way that the spraying is performed intermittently with intervals between the spraying and the spraying, the spraying time, the interval time, the spraying flow rate, and the total spraying amount per spraying are adjusted to maintain a predetermined furnace heat level, and the removal of the deposits is performed. The method for operating a smelting furnace includes a deposit removal process in which the charge loaded into the smelting furnace is reduced to the lower part of the deposits during operation or during a blowdown period, and the deposits on the walls are removed by the above-mentioned method for removing deposits from the walls of a smelting furnace.

Description

Technical Field

[0001] This invention relates to a method for removing deposits adhering to the walls of a smelting furnace and to the operation of the smelting furnace. In this specification, the unit of mass "t" represents 1000 kg. Background Technology

[0002] The formation mechanism of the deposits adhering to the furnace wall inside the ore melting furnace is believed to be as follows: First, alkalis such as Zn (zinc) and Na (sodium) contained in the ore evaporate in the lower part of the high-temperature ore melting furnace and condense in the lower-temperature parts of the furnace body and furnace wall near the furnace opening. This condensate becomes a binding material, solidifying the loaded ore and coke to form a firm deposit.

[0003] If the deposit grows on the furnace wall, the furnace interior will become distorted, and the airflow will become unstable. This will lead to poor material feeding and deterioration of furnace ventilation, resulting in reduced furnace productivity. On the other hand, if the deposit breaks off, the furnace temperature will drop due to insufficient heat for remelting. This will worsen the coke ratio, further reducing productivity.

[0004] In view of this situation, in order to suppress the circulation of zinc, alkali and other substances in the furnace during the operation of the smelting furnace, the content of zinc and alkali in the raw materials has always been strictly limited. In addition, the deposits on the furnace walls are removed.

[0005] Conventional methods for removing deposits involve reducing the amount of material loaded during shutdown or operation, cooling the deposits, and then applying thermal shock to peel them off. Alternatively, Patent Document 1 discloses a method of removing deposits by blasting with explosives such as danamit while the material is still loaded or with the material reduced.

[0006] Furthermore, Patent Document 2 discloses a method of detecting deposits, reducing the amount of material in the container and stopping the airflow, and then using gas as a refrigerant to cool the deposits, causing a rapid change in the physical properties of the deposits, such as thermal expansion, resulting in cracks, which cause the deposits to detach and be removed. Patent Document 3 discloses a method of controlling the formation of deposits, performing a material reduction and airflow stoppage operation, and then removing the deposits by colliding the material in the container with the deposits during the resumption of operation.

[0007] Existing technical documents Patent documents Patent Document 1: Japanese Patent Publication No. 42-026377 Patent Document 2: Japanese Patent Application Publication No. 54-033808 Patent Document 3: Japanese Patent Application Publication No. 55-115903 Summary of the Invention

[0008] The problem that the invention aims to solve However, the aforementioned prior art has the following problems.

[0009] First, the strict limitations on the zinc and alkali content in the raw materials used in existing methods narrow the range of raw material choices, leading to soaring product prices and making them uneconomical. Furthermore, simply cooling the adhering material results in a small amount of material being removed and a limited effect. Especially regarding material reduction during operation, the time is short, and the removal effect on the adhering material is minimal.

[0010] In addition, although the method described in Patent Document 1 is effective in removing the attached material, there is a high risk of damaging surrounding equipment such as sheet metal, furnace bricks and other furnace body due to the explosion.

[0011] Furthermore, the technologies described in Patent Documents 2 and 3 are based on the premise of shutdown, and do not envision their application during operation. Shutdown is an operation that occurs only once every few months, and its frequency is limited, posing a risk of deposit growth. In addition, in the case of gas cooling described in Patent Document 2, there are problems with low heat capacity and the long time required to achieve a cooling effect. Moreover, in the case of air cooling, if the combustible gases in the furnace are not replaced with non-combustible gases during shutdown, there is a risk of explosion, making it impossible to apply during operation.

[0012] Furthermore, in the method described in Patent Document 3 for causing the loading material to collide with the attached material, there is a risk that the loading material may be damaged by colliding with the furnace bricks after the attached material is removed.

[0013] Therefore, the present invention was made in view of the above-mentioned problems of the prior art, and its purpose is to provide a method and operation method for removing furnace wall deposits of ore smelting furnaces that can effectively remove furnace wall deposits during shutdown and operation.

[0014] Methods for solving problems The inventors of this application have discovered that by spraying water on the exposed material and cooling it under suitable conditions, the material can be removed efficiently.

[0015] The method for removing deposits from the furnace wall of a smelting furnace according to the present invention, which advantageously solves the above-mentioned problems, is characterized in that the upper surface of the charge being fed into the smelting furnace is lowered to the lower part of the deposit, exposing the deposit, and water is sprayed onto the exposed deposit to remove the deposit.

[0016] It should be noted that, in the method for removing deposits from the furnace wall of the smelting furnace involved in this invention, the following are more preferred solutions: a. In the aforementioned sprinkling, sprinkling is carried out intermittently by setting intervals between sprinkling sessions; b. During the aforementioned water spraying, adjust the spraying time, interval, spraying flow rate, and total spraying volume for each spraying in a manner that maintains the specified boiler hot water level, in order to remove the aforementioned adhering substances; c. The aforementioned water spraying is divided into multiple sessions, with each spraying session lasting 30–120 seconds and the interval between spraying sessions lasting 60–240 seconds, relative to a furnace volume of 1m³. 3 The water spray flow rate is set in the range of 8-23 kg / hour, which is relative to a furnace volume of 1m³. 3 The total amount of water sprayed is set to be in the range of 13 to 39 kg, thereby removing the aforementioned attached substances.

[0017] The operating method of the smelting furnace of the present invention, which advantageously solves the above-mentioned problems, is characterized by including: an attachment removal step, wherein, during operation or shutdown, the amount of charge put into the smelting furnace is reduced to the lower part of the attachment, and the attachment on the furnace wall is removed by any of the above-mentioned smelting furnace wall attachment removal methods.

[0018] It should be noted that, in the operating method of the smelting furnace of the present invention, the following is a more preferred solution: it further includes a step of detecting the deposits adhering to the furnace wall of the smelting furnace, wherein, if the aforementioned deposits are detected adhering to the furnace wall inside the smelting furnace, the aforementioned deposit removal step is performed.

[0019] Invention Effects According to the present invention, deposits can be removed not only during shutdown periods but also during operation, thus solving the problems listed above. Furthermore, deposits on the furnace body can also be removed by reducing the amount of fuel used. Attached Figure Description

[0020] [ Figure 1 This is a schematic cross-sectional view showing the upper vertical section of the smelting furnace.

[0021] [ Figure 2 [A diagram illustrating an example of sprinkling conditions according to an embodiment of the present invention, wherein (a) is] Figure 1 (a) is a schematic cross-sectional view of XX, and (b) is a diagram showing the water spraying pattern.

[0022] [ Figure 3 [A diagram illustrating other examples of sprinkling conditions related to the above embodiments, wherein (a) is] Figure 1 (a) is a schematic cross-sectional view of XX, and (b) is a diagram showing the water spraying pattern. Detailed Implementation

[0023] Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. Figure 1 A schematic cross-sectional view of the upper vertical section of a suitable smelting furnace to which the method for removing deposits from the furnace wall of the smelting furnace to which the present invention relates is applied.

[0024] The smelting furnace 1 described in this embodiment is a device for producing pig iron and ferromanganese using iron ore and manganese ore as the main raw materials. In particular, it is suitable for smelting furnace 1 that uses manganese ore as raw material to produce ferromanganese. The deposits 6 on the furnace wall of smelting furnace 1 using manganese ore as raw material are characterized by high Na (sodium) and K (potassium) content and low Zn (zinc) content. Therefore, in terms of the deposits of smelting furnace using manganese ore as raw material, the hydration expansion of Na2O and K2O is large.

[0025] In the method for removing deposits from the furnace wall of the smelting furnace involved in this embodiment, the detection of the generation of deposit 6 is not particularly limited. It is preferred to detect the generation of deposit 6 on the furnace wall 2 near the furnace opening 3 by any of the following methods.

[0026] (1) By reducing the material S inside the furnace 1, that is, by lowering the material level SL0 before the material reduction to the material level SL after the material reduction, the inner surface of the furnace wall 2 can be observed by visual inspection and photographic images, and the height and thickness of the adhering material 6 on the water-cooled furnace cooling wall 5 can be directly grasped.

[0027] (2) The generation of deposits 6 on the furnace wall 2 is detected by the temperature difference in the circumferential direction of the thermometer set outside the furnace body and the temperature change over time.

[0028] (3) The generation of deposits 6 is detected based on the temperature change of the cooling water used to cool the furnace body.

[0029] In this embodiment, for example, to compensate for the decrease in temperature of the molten metal furnace 1 during operation due to water spraying 4A from the water spray nozzle 4, the operating temperature is set higher than usual beforehand. Based on this, the upper surface of the furnace charge S (charge position SL) is lowered to the lower part of the deposits 6 on the furnace wall 2, exposing the deposits 6. Then, water is sprayed onto the exposed deposits 6 under specified conditions. Next, the deposits 6 are detached / removed based on cracks generated in the deposits 6 due to the difference in thermal expansion caused by cooling, and the crack progression mainly caused by the hydration expansion resulting from the reaction of water seeping into the cracks with the alkaline components. It should be noted that water spraying can also be performed during reduced-volume shutdown. The same deposit removal effect can be obtained.

[0030] In the water spraying method of this embodiment, it is preferable to spray water intermittently by designing a water spraying time 4A of a predetermined time ts and an interval ti during which water spraying is not performed. By setting the interval ti, due to the contraction caused by cooling in the water spraying and the expansion caused by reheating, cracks become more likely to enter the deposited material 6. In addition, it is preferable to adjust the water spraying conditions to set the furnace water level of the smelting furnace 1 to a predetermined range. Here, the furnace water level of the smelting furnace 1 is evaluated using the operating temperature of the smelting furnace 1 and the compositional variation of the manufactured product. It is possible to make the operating temperature of the smelting furnace 1 fall within a predetermined range and to make the concentration variation of Si, etc., which is a component of the manufactured product such as ferromanganese, fall within a predetermined range.

[0031] The spraying time ts for each application is preferably set in the range of 30–120 s. If it is less than the lower limit, there is a risk of insufficient removal of the deposited material 6. If it is greater than the upper limit, there is a risk of excessive cooling of the furnace and the generation of hydrogen gas due to the reaction of water-based gases. The interval time ti is preferably set in the range of 60–240 s. If it is less than the lower limit, there is a risk of insufficient furnace heat recovery. If it is greater than the upper limit, there is a risk that complete removal of the deposited material 6 will take a long time. The interval time ti is preferably set to approximately twice the spraying time ts. This allows for better furnace heat recovery and thermal shock to the deposited material 6. (Relative to a furnace volume of 1 m³) 3 The preferred water spray flow rate is set within the range of 8–23 kg / h. Below the lower limit, there is a risk of insufficient removal of adhering substances. Above the upper limit, there is a risk of excessive furnace heat reduction and hydrogen production due to water-based gas reactions. It is preferable to use a flow rate relative to a furnace volume of 1 m³. 3 The total water spray volume is set within the range of 13–39 kg. If it is less than the lower limit, there may be residual residue from removing the adhering substance 6. If it is greater than the upper limit, there is a risk of excessive reduction in furnace heat. A decrease in furnace heat leads to an increase in the reducing material ratio and Si concentration, which impairs operational stability.

[0032] Regarding the water spray nozzle 4 according to this embodiment, one nozzle may be configured to adjust the direction of water spraying 4A toward the attached material 6, or multiple nozzles may be configured along the circumference of the furnace opening 3. For multiple water spray nozzles 4 configured along the circumference of the furnace opening 3, the order of water spraying is determined in advance, and water is sprayed one nozzle at a time or multiple nozzles at a time, thereby removing the attached material evenly and efficiently.

[0033] Figure 1 The illustration shows a situation where the attachment 6 facing the furnace wall 2 is configured with a water spray nozzle 4. Figure 2 (a) in the example shows the... Figure 1 A schematic diagram of eight equally spaced water spray nozzles 4 on the furnace opening 3 as observed in cross-section XX. The spraying sequence 4B is shown in italics. Figure 2(b) is a schematic diagram showing a scenario where the water nozzle 4 continuously sprays water clockwise at predetermined intervals ti, targeting a pre-determined location for the attached material. By operating in this way, uneven watering can be avoided, and the attached material can be removed evenly and efficiently. Figure 2 In (b) of the diagram, ts represents the watering time, and ta represents the total watering time. Watering is carried out during the period when the diagram is shaded.

[0034] In addition, if there is an attachment 6 on a part of the furnace wall 2, a water spray nozzle 4 can be selected to aim at it and spray water 4A. Figure 3 (a) shows the case where water nozzles C and G are not used because there is no attachment 6 in the relative position, and water nozzles A, B, D, E, F, and H are selected. Figure 3 Example (b) is as follows: water is sprayed by aiming the water nozzle 4 at a predetermined location on the deposit 6 at a location relative to the deposit 6, and setting an interval ti that is twice the spraying time ts. By doing so, the deposit 6 that is biased against the furnace wall 2 can be removed evenly and efficiently.

[0035] The operating method of the smelting furnace according to this embodiment includes: an adhering material removal process, in which the amount of charge entering the smelting furnace is reduced to the lower part of the adhering material during operation or shutdown, and the adhering material adhering to the furnace wall is removed by the aforementioned furnace wall adhering material removal method. The removed adhering material descends in the smelting furnace together with the raw materials and other charge. The raw material components in the adhering material are directly melted in the lower part of the furnace. The volatile components such as alkali components in the adhering material are vaporized and rise. A portion of the vaporized components is captured by the raw materials and circulated within the furnace. The remaining portion is discharged outside the system in the form of furnace dust or the like.

[0036] In the operation method of the smelting furnace involved in this embodiment, it is preferable to have a step of detecting the deposits adhering to the furnace wall of the smelting furnace. If the deposits are detected to be adhering to the furnace wall inside the smelting furnace, the above-mentioned deposit removal step is performed. The detection of deposits can be exemplified by the three methods (1) to (3) mentioned above.

[0037] Example <Example 1> Used internal volume 450m 3 The ore melting furnace has eight dedicated water spray nozzles installed around its circumference for removing deposits from the furnace walls. The nozzles are adjusted to spray water onto the deposits, and the nozzle diameter is selected to meet the following water flow rate requirements. The single-pipe nozzles were selected to ensure their direction does not change due to the furnace's internal airflow velocity, and the following verification was performed.

[0038] Regarding the detection of deposits adhering to the furnace walls inside the smelting furnace, detection is based on changes in the temperature of either a furnace body thermometer or the cooling water installed in the furnace body. Furthermore, the determination of whether the deposits have been removed is also based on temperature changes measured using the furnace body thermometer or the cooling water temperature. If the deposits have not been removed, there is no temperature change; if the deposits have been removed, the measured temperature rises. In this embodiment, detection is based on changes in the temperature of the cooling water installed in the furnace body.

[0039] Based on the changes in furnace cooling water temperature, the estimated mass of deposits on the furnace body was 5.8 tons. Under these conditions, during a shutdown period, the upper surface of the charge inside the furnace was lowered to expose the deposits. Water was sprayed from one nozzle at a time for 60 seconds, at a flow rate of 8 tons per hour. The interval between nozzles was 420 seconds. After 2 hours of spraying, the estimated deposit mass was reduced to 0.6 tons. This indicates that approximately 90% of the deposits were removed.

[0040] <Comparative Example 1> Using the same equipment as in Example 1, with the deposits still attached, the material was reduced during the ventilation period, and the deposits were allowed to cool for approximately 24 hours without being sprayed with water. Approximately 40% of the deposits were removed through thermal shock.

[0041] <Comparative Example 2> Using the same equipment as in Example 1, with the deposits still attached, the material was reduced during operation, and the deposits were cooled for approximately 5 hours without being sprayed with water. Approximately 30% of the deposits were removed through thermal shock.

[0042] <Example 2> Using the same equipment as in Example 1, the estimated amount of deposits inside the furnace was 9.7 t, based on the furnace cooling water temperature. Under these conditions, feed was reduced during operation, and intermittent water spraying was applied towards the deposits for 5 hours. The spraying conditions included a 120-second interval after each 60-second spray. The water flow rate was set to 10 t / hour. The total water spraying volume was approximately 17 t. As a result, the estimated deposit amount was reduced to 1.0 t. A 90% removal rate of deposits was confirmed, similar to Example 1.

[0043] <Example 3> Using the same equipment as in Example 1, the estimated amount of deposits inside the furnace was 6.8 tons based on the furnace cooling water temperature. Under these conditions, feed was reduced during operation, and intermittent water spraying was applied to the deposits for 1 hour. The spraying conditions included a 120-second interval after each 50-second spray. The water flow rate was set to 8 tons / hour. The total water spraying volume was approximately 3 tons. As a result, the estimated deposit amount was reduced to 4.1 tons. Approximately 40% of the deposits were removed.

[0044] <Example 4> Using the same equipment as in Example 1, the estimated amount of deposits inside the furnace was 7.9 tons, based on the furnace cooling water temperature. Under these conditions, feed was reduced during operation, and intermittent water spraying was applied to the deposits for 3 hours. The spraying conditions included a 120-second interval after each 45-second spray. The water flow rate was set to 6 tons / hour. The total water spray volume was approximately 5 tons. As a result, the estimated deposit amount was reduced to 4.0 tons. Approximately 50% of the deposits were removed.

[0045] <Example 5> When water is sprayed into the furnace, the temperature of the raw materials and molten material inside the furnace may decrease, and the furnace heat may decrease. It is considered necessary to prevent the water-based gas reaction, which is an endothermic reaction. Therefore, exhaust gas analysis of the smelting furnace was continuously performed to determine the water spraying conditions that do not result in the generation of hydrogen associated with the water-based gas reaction. Using the same equipment as in Example 1, the preferred conditions were confirmed based on the water spraying of one out of eight furnaces. The results are shown in Table 1.

[0046] [Table 1] The water spraying time and flow rate were gradually increased, and the flow rate was reduced after hydrogen production was observed. Experiments were conducted to investigate the presence or absence of hydrogen production. It was found that water spraying could be performed without hydrogen production when the spraying time was below 120 seconds and the flow rate was below 10 t / hour. The water spraying flow rate that reduces furnace heat varies with the furnace volume; therefore, it can be determined that the flow rate relative to a furnace volume of 1 m³ is... 3 The preferred water flow rate is below 23 kg / hour.

[0047] <Example 6> Next, experiments were conducted to determine the optimal watering conditions, namely watering time and water flow rate, for efficient removal of deposits. Using the same equipment as in Example 1, six out of eight removal nozzles were used, with each nozzle spraying water for one hour. The removal effect was confirmed under six conditions, namely treatments No. 1 to No. 6 in Table 2. The experiments were conducted in the following order: treatment No. 1 for one hour, then treatment No. 2 for one hour, and so on, until treatment No. 6 for one hour. The determination of whether deposits were removed was based on the change in furnace temperature measured using thermocouples installed in the furnace body. That is, if deposits were not removed, the temperature change was determined to be "none," and if deposits were removed, the temperature was determined to be "rising." It should be noted that the interval time was fixed at twice the watering time.

[0048] [Table 2] No hydrogen production based on water-based gas reactions occurred in treatments No. 1 through No. 6. According to the results in Table 2, to remove the deposits, the water spraying time must be at least 30 seconds and the water flow rate at least 4 t / hour. Therefore, it can be concluded that relative to a furnace volume of 1 m³... 3 The preferred water flow rate is 8 kg / hour or higher.

[0049] Industrial availability The method and operation method for removing deposits from the furnace wall of the smelting furnace involved in this invention are applicable to smelting furnaces, especially in the case of smelting furnaces using manganese ore as raw material, where the effect is great and the productivity is improved, and therefore it is useful in industry.

[0050] Explanation of reference numerals in the attached figures 1. Ore smelting furnace 2 Furnace wall 3. Furnace opening 4. Sprinkler nozzles 4A Sprinkler 4B Sprinkling Sequence 5 (Water-cooled) Furnace body cooling wall 6. (Furnace wall) deposits 7. Reduced ingredients 8. (Removal) of attached substances S (furnace contents) SL (after material reduction) loading position SL0 (before material reduction) material loading position ts Sprinkling time ti interval time Total watering time

Claims

1. A method for removing deposits from the furnace wall of a smelting furnace, wherein, The upper surface of the charge being fed into the smelting furnace is lowered to the lower part of the adhering material, exposing the adhering material. Water is then sprayed onto the exposed adhering material to remove it.

2. The method for removing deposits from the furnace wall of a smelting furnace as described in claim 1, wherein, In the water spraying process, water spraying is carried out intermittently by setting intervals between spraying sessions.

3. The method for removing deposits from the furnace wall of a smelting furnace as described in claim 2, wherein, During the spraying process, the spraying time, interval, flow rate, and total amount of water are adjusted to maintain a specified boiler water level in order to remove the attached material.

4. The method for removing deposits from the furnace wall of a smelting furnace as described in claim 3, wherein, The water spraying is performed in multiple sessions, with each spraying session lasting 30–120 seconds and the interval between spraying sessions lasting 60–240 seconds, relative to a furnace volume of 1m³. 3 The water spray flow rate is set to a range of 8–23 kg / hour, which is relative to a furnace volume of 1 m³. 3 The total amount of water sprayed is set to be in the range of 13 to 39 kg, thereby removing the attached material.

5. Operating methods for the ore melting furnace, including: The attachment removal process, wherein during operation or shutdown, the amount of material fed into the smelting furnace is reduced to the lower part of the attachment, and the attachment on the furnace wall is removed by the furnace wall attachment removal method of any one of claims 1 to 4.

6. The method for operating a smelting furnace as described in claim 5 further includes a step of detecting deposits adhering to the furnace wall. in, If the deposits are detected adhering to the furnace wall inside the smelting furnace, the deposit removal process is performed.

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