Method for estimating accumulation shape of blast furnace inner filling and method for replacing blast furnace inner coke

Abstract

This invention provides a method for estimating the shape of the furnace packing material after the coke inside the blast furnace has been consumed by a burner during startup in a blast furnace with the charge-falling face shut down. The method for estimating the shape of the furnace packing material after the coke inside the blast furnace has been consumed by a burner inserted into the furnace through the taphole and used during startup in a blast furnace with the charge-falling face shut down includes: a step of estimating the shape of the furnace packing material during the charge-falling face shut down; a step of estimating the coke filling area inside the furnace based on the shape of the furnace packing material estimated in the previous step and the shape of the solidified layer at the bottom of the furnace; a step of estimating the amount of coke consumed by the burner; and a step of estimating the shape of the furnace packing material after the coke consumption based on the amount of coke consumed.

Description

Technical Field

[0001] This invention relates to a method for estimating the packing shape of blast furnace filling materials and a method for replacing coke inside a blast furnace. Background Technology

[0002] In a blast furnace, iron ore and coke are charged from the top, high-temperature air is blown in through tuyeres located at the bottom, and molten iron and slag are discharged through the taphole. The reducing gases such as high-temperature CO and H2 generated at the tuyeres rise within the furnace, heating, reducing, and melting the descending iron ore to produce molten iron. During stable operation, high-temperature air is continuously supplied to the furnace. However, due to unstable conditions such as furnace repairs or operational malfunctions, a temporary halt to air supply—known as a shutdown—is sometimes implemented. In this situation, the temperature of the furnace packing decreases due to heat exhaust from the furnace body and air extraction from the tuyeres.

[0003] If the furnace temperature decreases, the viscosity of the molten material increases, causing it to solidify and become difficult to discharge from the taphole. If air is supplied from the tuyeres under these conditions, the amount of molten slag retained in the lower part of the furnace increases because the reduced molten slag is not discharged. With the temperature rise in the lower part of the furnace caused by the dripping slag, the retained slag can sometimes be discharged. However, if the temperature rise in the lower part of the furnace is insufficient, the difficulty in discharging the slag continues, and the amount of retained slag further increases. If the slag level (the height of the molten slag surface) reaches the tuyeres due to the significant increase in retention, it can cause tuyeres to melt and tuyeres to become blocked. In this situation, because air cannot be supplied to the furnace, the heat input to the furnace disappears, leading to a furnace cooling accident.

[0004] Here, a furnace cold snap refers to a significant drop in the heat level inside the blast furnace, making it impossible to discharge molten iron and slag from the tapholes, thus making stable operation difficult. In such an incident, furnace conditions are restored through the following methods: First, by blowing oxygen or similar methods, the solidified material between a specific taphole and the tuyeres directly above it is melted and discharged, ensuring an outlet for the molten material. Then, air is supplied to the aforementioned taphole and 2-3 tuyeres directly above it, using the generated molten material to gradually melt the surrounding solidified layer while bringing the number of tapholes and tuyeres used closer to a stable operating level. It typically takes 2-3 months from a furnace cold snap to a stable operating level; therefore, the amount of molten iron produced is significantly reduced during this period. Furthermore, the risk of operators being exposed to high-temperature molten material and toxic gases is high during the recovery process. Therefore, a furnace cold snap can be considered an operational failure with significant economic and safety losses and high risks.

[0005] As mentioned earlier, during startup operations following a shutdown, the low heat level inside the furnace increases the risk of the aforementioned furnace cold-related accidents. Therefore, previously, the coke ratio was increased before shutdown to raise the heat level inside the furnace and reduce the risk of furnace cold-related accidents. However, as the shutdown period lengthens, heat compensation based on the increased coke ratio gradually becomes insufficient to maintain the heat level inside the furnace. In this situation, as... Figure 1 As shown, the following method is adopted: Under conditions of high coke ratio, after reducing the volume of the blast furnace packing from the upper part of the blast furnace belly to the level of the tuyeres, a shutdown is implemented. From the shutdown until the start-up, raw materials are re-charged under conditions of high coke ratio, and then blast is restarted. This type of shutdown is called a lowered packing shutdown. Lowered packing shutdown is implemented during large-scale equipment repairs and long-term shutdowns of blast furnace operation, but compared with a normal shutdown, it becomes a long-term shutdown, further increasing the risk of furnace cooling during startup.

[0006] As a means to reduce the risk of furnace cooling during such shutdowns or reduced burden level shutdowns, such as Figure 1 As shown, a method is proposed in which the burner is inserted into the tap hole and oxygen and fuel are blown in before air is supplied, and air is supplied after the heat level between the tuyeres and the tap hole is sufficiently increased (Patent Document 1). In addition, in order to improve the ventilation and liquid flow in the lower part of the furnace, a method is proposed to remove a portion of the pulverized / strength-reduced coke (degraded coke) in the lower part of the furnace and replace it with new coke (Patent Document 2).

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2016-30833

[0010] Patent Document 2: Japanese Patent Application Publication No. 5-295415

[0011] Non-patent literature

[0012] Non-Patent Literature 1: Yoshikawa Bunmei et al., 5, "Estimation of Refractory Erosion and Solidification Layer Distribution in Blast Furnace Hearth and Its Application in Operation", Iron and Steel, No. 15, 1987, pp. 2068-2075 Summary of the Invention

[0013] The problem that the invention aims to solve

[0014] The method described in Patent Document 1 is effective in improving the thermal level of the lower part of the blast furnace. However, from the perspective of reducing the risk of furnace cooling accidents, it is believed that simultaneously using the method described in Patent Document 2, which replaces the pulverized / strength-reduced deteriorated coke with fresh coke, can ensure further ventilation and liquid flow in the lower part of the furnace, thereby reducing the risk of furnace cooling accidents. In addition, by removing a portion of the coke in the lower part of the furnace midway, the packing material above it partially descends, and the layering structure of the subsequently charged raw materials becomes uneven. Therefore, there are concerns about adverse effects on operation, such as deterioration of ventilation in the upper part of the furnace and poor raw material reduction.

[0015] The purpose of this invention is to provide a method for estimating the shape of the packing material in a blast furnace after the coke inside the furnace has been consumed by a burner during the start-up of the blast furnace when the charge surface is lowered and the furnace is shut down.

[0016] In addition, the present invention aims to provide a method for replacing coke in a blast furnace using the aforementioned estimation method.

[0017] Methods for solving problems

[0018] The present invention has the following structure.

[0019] [1] A method for estimating the packing shape of blast furnace filler, wherein, in a blast furnace with reduced charge surface and shut-down operation, during the start-up of the blast furnace, the packing shape of the filler after inserting a burner into the furnace through the tap hole and consuming the coke in the furnace using the burner is estimated, the method for estimating the packing shape of blast furnace filler has the following features:

[0020] The process of estimating the accumulation shape of the furnace packing material during the downburst blast;

[0021] The process of estimating the filling area of ​​coke in the furnace based on the stacking shape of the furnace packing material estimated in the above process and the shape of the solidified layer at the bottom of the furnace;

[0022] The process of estimating the amount of coke consumed in the furnace using the aforementioned burners; and

[0023] The process of estimating the shape of the furnace packing material after the coke in the furnace is consumed based on the amount of coke in the furnace mentioned above.

[0024] [2] A method for replacing coke inside a blast furnace, which is a method for replacing coke inside a blast furnace that uses the method for estimating the packing shape of the blast furnace packing as described in [1] above.

[0025] Specifically, coke is filled into the blast furnace in a manner that suppresses the changes in the shape of the furnace filler during the aforementioned material reduction and blast shutdown, and the changes in the shape of the furnace filler after the consumption of coke in the furnace.

[0026] Invention Effects

[0027] According to the present invention, in a blast furnace with a reduced charge level and no blast, when starting up the blast furnace, it is possible to estimate the shape of the packing material in the furnace after the coke (deteriorated coke) in the furnace has been consumed by the burners.

[0028] According to the present invention, the changes in the packing shape of the furnace filler associated with the consumption of deteriorated coke are estimated, and coke is then filled into the blast furnace based on these estimates. This allows for the replacement of deteriorated coke in the furnace filler with fresh coke during downtime at the lower charge level, while mitigating the changes in the packing shape associated with coke replacement, thereby improving the ventilation and liquid flow in the lower part of the furnace. As a result, the blast furnace can be stably started up from a downtime state to a stable operating state. Attached Figure Description

[0029] [ Figure 1 ] Figure 1 This is a schematic diagram showing an example of the packing shape inside a blast furnace during a downburst blast, and the state of the burner being inserted into the furnace from the tap hole.

[0030] [ Figure 2 ] Figure 2 This is a diagram showing the presumed coke filling area in the furnace in this embodiment.

[0031] [ Figure 3 ] Figure 3 This is a diagram showing the stacking shape of the furnace packing after the presumed consumption of coke in the furnace in this embodiment. Detailed Implementation

[0032] This invention is implemented in a blast furnace. A blast furnace is an industrial furnace that uses iron ore, sinter, and other main raw materials containing iron oxide, and reducing materials such as coke containing carbon and hydrogen to produce molten iron. The main raw materials and reducing materials are charged in layers from the top of the furnace, and hot air containing oxygen and reducing materials such as pulverized coal are fed into the furnace through the tuyeres. As the CO and H2 generated by the gasification of the reducing materials near the tuyeres flow upwards into the furnace, the main raw materials charged from the top are heated, reduced, and melted to produce molten iron. The generated molten iron drips down into the furnace and accumulates in the hearth, and is discharged from the furnace through the taphole located on the lower side of the blast furnace. The internal volume, raw material charging mechanism, number of tuyeres, and other equipment designs of blast furnaces vary depending on the specific furnace body, but this invention can be applied regardless of the aforementioned differences in equipment design.

[0033] Furthermore, in blast furnace operation, various materials can be used as the main raw material, reducing material, and reducing material blown in from the tuyeres. Examples of main raw materials include iron ore, sinter, pellets, scrap iron, and reduced iron. Examples of reducing materials charged from the top include lump coke, coke particles smaller than lump coke, and iron coke. Examples of reducing materials blown in from the tuyeres include combustible gases containing at least one of carbon or hydrogen atoms, such as pulverized coal, coke powder, plastics, and natural gas, as well as liquid fossil fuels. This invention can be applied regardless of the type of raw material or reducing material used.

[0034] In this invention, it was discovered that by estimating the packing shape of the blast furnace filler during a downburst shutdown (hereinafter also referred to as the initial packing shape), the shape of the solidified layer at the bottom of the furnace (solidified layer shape), the consumption behavior of coke (degraded coke) in the furnace, and the packing shape of the furnace filler after the consumption of degraded coke, it is possible to estimate the change in the packing shape of the furnace filler before and after the consumption of degraded coke. Furthermore, it was discovered that by appropriately determining the amount and location of newly filled coke based on the aforementioned estimation results of the packing shape change, it is possible to suppress the change in the packing shape of the furnace filler before and after the replacement of coke filled into the furnace during a downburst shutdown and the replacement of newly filled coke during startup from the downburst shutdown.

[0035] <Method for estimating the packing shape inside a blast furnace>

[0036] The method for estimating the packing shape of blast furnace filler of the present invention comprises: a step of estimating the packing shape of blast furnace filler during a downburst blast; a step of estimating the filling area of ​​coke in the furnace based on the packing shape of blast furnace filler estimated in the aforementioned step and the shape of the solidified layer at the bottom of the furnace; a step of estimating the amount of coke in the furnace consumed by the burner; and a step of estimating the packing shape of blast furnace filler after coke consumption based on the aforementioned amount of coke in the furnace.

[0037] (The process of estimating the shape of the furnace packing material during the downdraft and blast shutdown)

[0038] In the process of estimating the packing shape of the furnace filler during the blast furnace shutdown at the lowering surface, the initial packing shape of the furnace filler during the shutdown at the lowering surface is estimated. As a method for estimating the initial packing shape, one example is using a rangefinder to measure the distances from multiple points from the top of the blast furnace to the surface of the furnace filler during the shutdown at the lowering surface, and estimating the initial packing shape based on the results. The rangefinder is not particularly limited; non-contact rangefinders, such as laser rangefinders, can be used. Furthermore, the packing shape can be estimated three-dimensionally by measuring the distances from multiple points to the surface of the furnace filler using the aforementioned rangefinder. However, the method for estimating the initial packing shape is not limited to this, and the technology of the present invention can be implemented without relying on a method for estimating the initial packing shape.

[0039] (The process of estimating the filling area of ​​coke in the furnace)

[0040] In the process of estimating the coke filling area in the furnace, the coke filling area in the furnace is estimated based on the packing shape (initial packing shape) of the furnace packing material estimated in the aforementioned process of estimating the initial packing shape, and the shape of the solidified layer at the bottom of the furnace. In a blast furnace with a reduced charge level and no blast, a solidified layer grows at the bottom of the furnace. In this process, the shape of the solidified layer present at the bottom of the furnace is estimated. As a method for estimating the shape of the solidified layer at the bottom of the furnace, a method based on the boundary element method can be cited, for example, the method described in Non-Patent Document 1. In the method described in Non-Patent Document 1, the solidified layer interface is assumed to be the isotherm of the solidification temperature of pig iron (1150°C), and heat transfer calculations are performed based on the boundary element method. Then, the solidified interface with the smallest error between the measured value of the furnace bottom temperature measured by thermocouples in the actual furnace and the temperature calculation result based on the boundary element method is calculated sequentially. The shape of the solidified layer at the bottom of the furnace can be estimated from the solidified interface calculated in this way. It should be noted that thermocouples are usually installed at multiple locations along the circumference and height of the blast furnace, at the bottom of the furnace, which is lower than the tuyeres.

[0041] As described above, after estimating the shape of the solidified layer at the bottom of the furnace, the filling area of ​​coke in the furnace is estimated. As a method for estimating the filling area of ​​coke in the furnace, the area other than the shape of the solidified layer and the filling area of ​​coke in the furnace can be estimated based on the initial stacking shape estimated in the above manner and the shape of the solidified layer at the bottom of the furnace.

[0042] (The process of estimating the amount of coke consumed in the furnace by using the burner and the process of estimating the packing shape of the furnace packing after the coke is consumed based on the above-mentioned amount of coke in the furnace)

[0043] In the process of estimating the amount of coke consumed in the furnace using burners, the amount of coke consumed by the burners inserted into the furnace from the taphole of the blast furnace is estimated. As a method for this estimation, for example, one could consider the flow path in the coke-filled layer (the coke-filled area in the furnace) using combustion gases blown into the furnace from the burners and the composition of the combustion gases, assuming that all the combustion gases blown in from the burners react with the coke. However, since the temperature of the combustion gases gradually decreases as they rise in the furnace, there is a possibility that it may be lower than the temperature at which the reaction occurs in the coke-filled layer. Furthermore, even if the temperature of the combustion gases is the temperature at which the reaction occurs, the reaction rate varies depending on the temperature. Therefore, it is desirable to estimate the consumption behavior of coke (deteriorated coke) in the furnace based on consideration of heat transfer between the combustion gases and the coke in the furnace, and the temperature dependence of the reaction rates of various reactions.

[0044] The gas used in the burner inserted through the tap hole can be the gas itself or the gas consumed by the combustion of the gas in the furnace to react with the coke. The inventors of this application used LNG and oxygen as the aforementioned gas, but the types of gases that can be used in the technology described in this invention are not limited to these.

[0045] As described above, in the process of estimating the furnace packing shape after the coke consumption by estimating the amount of coke consumed by the burner (furnace coke consumption area), the furnace packing shape after the coke consumption is estimated based on the aforementioned estimated amount of coke in the furnace. Regarding the packing shape after the coke consumption, as follows... Figure 3 As shown, the area outside the aforementioned void area can be estimated as the accumulation shape of the furnace packing material after the coke in the furnace has been consumed, based on the void area created by the combustion gases in which the coke (deteriorated coke) in the furnace is consumed.

[0046] <Methods for replacing coke inside a blast furnace>

[0047] The blast furnace coke replacement method of the present invention uses the aforementioned method for estimating the packing shape of the blast furnace packing. Specifically, based on the packing shape of the packing during the downburst blast (initial packing shape) and the packing shape of the packing after the coke consumption, new coke is added to the blast furnace in a manner that suppresses changes in the packing shape, replacing the coke in the downburst blast with new coke. That is, in terms of the amount and location of the newly added coke, it is desirable to fill in a way that reproduces the initial packing shape of the packing. Examples of methods for adding new coke include, for instance, filling from the top of the furnace as in normal operation, or inserting a belt conveyor into the furnace from the tuyeres and filling via that belt conveyor. The greater the height difference between the location of the new coke and the packing, the higher the likelihood of finer-grained propagation of the new coke. Therefore, it is desirable to fill the furnace with new coke from a location with the smallest possible height difference from the packing.

[0048] As explained above, by using the method of the present invention, the change in the packing shape associated with the consumption of coke (degraded coke) in the blast furnace during a downburst is predicted, and coke is then filled into the blast furnace based on this predicted result. This allows for the replacement of degraded coke with new coke while mitigating the change in the packing shape associated with the replacement of coke in the blast furnace, thus improving the ventilation and liquid flow in the lower part of the furnace. Consequently, a blast furnace can be started up more stably from a downburst state until it reaches a stable operating state.

[0049] Example

[0050] The present invention is illustrated below with specific examples. However, the present invention is not limited to the following examples.

[0051] In this embodiment, for a commercial blast furnace that has been in a state of long-term material reduction and shutdown, the accumulation shape of the furnace packing after the consumption of deteriorated coke is estimated based on the above implementation method. Then, new coke is filled and air is supplied from the tuyeres to start the blast furnace.

[0052] First, the initial packing shape of the blast furnace packing is estimated based on the distance data measured from the top of the blast furnace at the bottom of the blast furnace using a non-contact rangefinder (in this embodiment, a laser rangefinder). Then, using data from a thermometer located at the bottom of the blast furnace, the shape of the solidified layer at the bottom of the blast furnace is estimated using the boundary element method, following the method described in the aforementioned embodiment. The results of estimating the packing area of ​​coke in the furnace based on the above method are shown below. Figure 2 It should be noted that, Figure 2 (a) is a diagram showing the estimated coke filling area in the furnace from an oblique angle. Figure 2 (b) shows Figure 2A vertical cross-sectional view (schematic) of the iron outlet (2th) of (a).

[0053] Next, it is envisioned that a burner is inserted into the blast furnace through the taphole at the bottom of the furnace and combustion gas is blown into the furnace. Using the method described in the above embodiment, the change in the shape of the furnace packing material accompanying the consumption of coke (deteriorated coke) caused by the blowing of the combustion gas is estimated. The estimated results of the shape of the furnace packing material after the consumption of deteriorated coke are shown below. Figure 3 It should be noted that, Figure 3 (a) is a diagram showing the packing shape of the furnace fill after the estimated consumption of deteriorated coke, viewed from an oblique angle. Figure 3 (b) shows Figure 3 A vertical sectional view (schematic) of the tap hole (2th) in (a). Figure 2 , Figure 3 A comparison reveals that, from near the taphole upwards, the degraded coke is consumed, forming grinding-mortar-like cavities. Additionally, utilizing... Figure 2 , Figure 3 The estimated results were compared, and the weight of new coke required to fill the cavity was calculated based on the volume of the cavity.

[0054] Based on the aforementioned weight calculations, a burner is inserted through the tap hole to consume the deteriorated coke in the furnace. After new coke is filled into the cavity through the tuyeres, coke and main raw materials are loaded from the top of the furnace to the portion above the tuyeres' liquid level. Then, when air is supplied from the tuyeres for startup, the molten iron slag is discharged smoothly from the tap hole, allowing the furnace to return to a stable operating state without major malfunctions such as the inability to discharge molten iron slag and the residual slag remaining at the tuyeres level (tuyeres' height).

[0055] Based on the above results, it can be seen that the present invention can mitigate the changes in the packing shape of the furnace packing associated with coke replacement in the blast furnace, while replacing deteriorated coke with new coke to improve the ventilation and liquid flow in the lower part of the furnace, so as to stably start up the blast furnace from the down-feed state to a stable operating state.

[0056] Explanation of reference numerals in the attached figures

[0057] 1. Blast Furnace Body

[0058] 2 air outlets (supply air outlets)

[0059] 3 Iron outlet holes

[0060] 4 coke

[0061] 5. Solidification layer

[0062] 6 burners

Claims

1. A method for estimating the packing shape inside a blast furnace, wherein, In a blast furnace undergoing a down-feeding shutdown, during startup, the shape of the furnace packing material after the burner is inserted into the furnace through the taphole and used to consume the coke is estimated. The method for estimating the shape of the furnace packing material includes: The process of estimating the accumulation shape of the furnace packing material during the downburst blast; The process of estimating the shape of the solidified layer at the bottom of the furnace, and estimating the filling area of ​​coke in the furnace based on the estimated stacking shape of the furnace packing material and the shape of the solidified layer at the bottom of the furnace in the process described above. A process for estimating the amount of coke consumed in the furnace when using the burner; and The process of estimating the shape of the furnace packing material after the coke in the furnace is consumed based on the amount of coke in the furnace.

2. A method for replacing coke inside a blast furnace, wherein the method for estimating the packing shape of the blast furnace packing as described in claim 1 is used, wherein... Coke is filled into the blast furnace in a manner that suppresses changes in the shape of the furnace packing material during the downburst blast and the shape of the furnace packing material after the coke in the furnace is consumed.

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