JP7063159B2 - Quality control method for coke for blast furnace - Google Patents

Description

The present invention relates to a method for controlling the quality of coke charged into a blast furnace.

In a blast furnace, hot air is normally supplied from below the blast furnace to iron raw materials (sintered ore and iron ore) and coke charged in layers inside the blast furnace, and a reducing gas is generated by the reaction between the hot air and coke. Then, the iron raw material is reduced to metallic iron by the generated reducing gas to produce molten pig iron.

In the high temperature zone at the bottom of the blast furnace, coke is the only solid. Therefore, the air permeability and liquid permeability in the blast furnace depend on the properties of coke in the high temperature zone. For example, when coke in a high temperature zone is pulverized, air permeability and liquid permeability deteriorate, and blast furnace operation malfunction occurs. Therefore, in the operation of the blast furnace, it is important to properly evaluate the quality of coke and control the quality of coke.

The coke for quality control is generally collected in the middle of the transport route before the coke is extruded from the coke oven and charged into the blast furnace. This control index is determined to control the quality of coke, but the average particle size of coke and the drum strength index, which are considered to correlate with the air permeability in the blast furnace, are used as control indexes. .. Then, by considering the past operation results of each blast furnace, the lower limit of the average particle size of coke and the lower limit of the drum strength index of coke are empirically determined as management indexes.

In coke quality control, when the average particle size and drum strength index of the collected coke do not meet the control index, the coke manufacturing conditions are changed. For example, the quality of coke is improved by increasing the blending ratio of strong coking coal and increasing the amount of coking material added.

In Patent Document 1, the ore particle size on the outlet side of the storage tank, the coke particle size on the outlet side of the storage tank, the particle size reduction rate peculiar to the apparatus, and the correction coefficient according to the strength of each particle are used in the furnace. A particle size control method for estimating the particle size of the charge inside and controlling the ratio of the harmonized average diameter of ore / coke to a predetermined value or more is disclosed.

Japanese Unexamined Patent Publication No. 61-1196808

Since the control index is only empirically determined based on the past operation results of each blast furnace, even if the average particle size of coke and the drum strength index meet the control index, the air permeability in the blast furnace remains. It may get worse. In addition, even if the average particle size of coke and the drum strength index do not meet the control index, the air permeability in the blast furnace may not have deteriorated. In this case, over-engineered coke must be manufactured. This has led to cost deterioration. Since the properties of coke fluctuate daily, it is not preferable to determine the management index empirically and uniquely in order to control the quality of coke on a daily basis.

In the invention described in Patent Document 1, the particle size reduction rate peculiar to the apparatus is required when estimating the particle size of the charged material in the furnace, but this value is the furnace at the time of filling before the blast furnace is fired. It must be obtained by sampling the charge inside, and it cannot be applied to a blast furnace in operation.

Therefore, an object of the present invention is to provide a quality control method for coke for blast furnace, which can appropriately control the quality of coke on a daily basis.

The present invention is a quality control method for controlling the quality of coke charged into a blast furnace. First, using a coke pulverization model assuming that the dough strengths are the same, the correlation between the average particle size of coke and the strength index is obtained in advance, and the strength index of coke is the average particle size of coke in this correlation. It is defined as a management index for controlling the quality of coke that it is equal to or higher than the strength index corresponding to. In this correlation, the larger the average particle size, the lower the intensity index. Then, the average particle size and strength index of coke collected in the middle of the transport path for transporting coke to the blast furnace are measured, and it is determined whether or not the average particle size and strength index satisfy the control index.

When the intensity index is the drum intensity index, the above correlation can be expressed by the following formula (I).

In the above formula (I), MS is an average particle size (mm), DI is a drum strength index (%), and MS ₀ is a reference value (mm) of the average particle size. Further, DI ₀ is a reference value (%) of the drum strength index, and α is a coefficient. The coefficient α shown in the above formula (I) can be, for example, −0.07.

In the above formula (I), the reference value MS ₀ of the average particle size can be set to the lower limit value of the average particle size determined from the past operation results when the operation of the blast furnace is stable. Further, the reference value DI ₀ of the drum strength index can be set to the lower limit value of the drum strength index determined from the past operation results when the operation of the blast furnace is stable.

On the other hand, in the above formula (I), the reference value MS ₀ of the average particle size can be the average particle size when the aeration resistance index of the blast furnace is equal to or less than a predetermined value. Further, the reference value DI ₀ of the drum strength index can be a drum strength index when the ventilation resistance index of the blast furnace is equal to or less than a predetermined value.

According to the present invention, by using a control index determined based on the correlation between the average particle size and the strength index of coke having the same dough strength, appropriate control for daily control of coke quality is performed. It can be performed.

It is a figure which shows the correlation of the average particle diameter of coke and the drum intensity index. It is a figure which shows an example of the transport path of coke. In this embodiment, it is a figure which shows the control index (average particle diameter and drum strength index) for controlling the quality of coke. It is a figure which shows the control index (average particle diameter and drum strength index) for controlling the quality of coke in the modification of this embodiment. In the past, it is a figure which shows the control index (average particle size and drum strength index) for controlling the quality of coke. It is a figure which shows the coke which satisfies the control index determined in this embodiment, and the coke which does not satisfy this control index in the coordinate system of a draft resistance index and a drum strength index. It is a figure which shows the coke which satisfies the control index determined by the modification of this embodiment, and the coke which does not satisfy this control index in the coordinate system of a draft resistance index and a drum intensity index. It is a figure which shows the coke which satisfies the control index which was determined conventionally, and the coke which does not satisfy this control index in the coordinate system of a draft resistance index and a drum intensity index.

A quality control method for coke for blast furnace, which is an embodiment of the present invention, will be described. note that. Blast furnace coke is coke used in a blast furnace, and is hereinafter simply referred to as coke.

In the quality control method of the present embodiment, first, the correlation between the average particle size of coke and the strength index when the dough strength of coke is constant is obtained in advance. Then, the average particle size and the intensity index specified by this correlation are used as the standard of the control index for controlling the quality of coke. Specifically, when the coke intensity index is equal to or higher than the intensity index corresponding to each average particle size in the above correlation, it is a control index for controlling the quality of coke.

The dough strength is a strength that depends on the original substrate strength of coke and the influence of pores, and is a strength that does not depend on the influence of cracks and defects. The dough strength is expressed by the crushing strength and the Brinell hardness measured by removing the influence of cracks and defects by reducing the sample size, and the substrate strength is expressed by the micro Vickers hardness.

The fact that the dough strength is constant or the same means that the correction coefficient δ is constant in the coke pulverization model described later, but it does not necessarily have to be exactly the same.

As the average particle diameter, for example, a mass average diameter, an arithmetic average diameter, or a median diameter can be used. When determining the correlation between the average particle size and the intensity index, one of the mass average diameter, the arithmetic average diameter, and the median diameter may be specified.

The coke strength index means a rotational strength index or a drop strength index. As the rotational strength index, for example, the drum strength index DI specified by JIS, the tumbler strength index TI specified by ASTM and the tumbler strength index TI specified by JIS, the Mycam strength index M specified by ISO and DIN, or the ilcied strength index I specified by NF and ISO are used. be. As the drop intensity index, for example, there is a shutter intensity index SI specified by JIS. When determining the correlation between the average particle size and the intensity index, specify one of the drum intensity index DI, the tumbler intensity index TI, the Mycam intensity index M or the ilcid intensity index I, or the shutter intensity index SI. Just do it.

In the following description, the drum strength index DI, which is a rotational strength index, is used among the strength indexes. Unless otherwise specified, the drum strength index DI is the drum strength index DI ¹⁵⁰ ₁₅ defined in JIS K2151, and the mass percentage (%) of coke having a particle size of 15 mm or more in coke after 150 rotations of the drum. Is. However, the particle size that defines the drum strength index DI is not limited to 15 mm. For example, considering the particle size (6 to 15 mm) of the powder generated by the volume destruction of coke described later, the drum strength index DI is specified. The particle size to be formed may be a value within the range of 6 to 15 mm. Further, the rotation speed of the drum is not limited to 150 rotations, and may be 30 rotations or other rotation speeds. In the case of the tumbler strength index TI, the tumbler strength index TI ¹⁴⁰⁰ ₆ , which is the mass percentage on the sieve of 6 mm after 1400 rotations in the tumbler tester, can be used. In the case of the Mycam intensity index M, M ¹⁰⁰ ₁₀ can be used, and in the case of the ilcided intensity, I ⁵⁰⁰ ₁₀ can be used. Furthermore, for the same reason, in the case of the shutter intensity index SI, the mass percentage on the sieve of 6 to 15 mm may be used.

Since the coke drum strength index DI depends on the coke average particle size and the dough strength, the coke dough strength is constant and the grain size is constant in order to obtain the correlation between the coke average particle size and the drum strength index DI. It is necessary to prepare multiple types of coke that differ only in the distribution (that is, the average particle size).

It is generally difficult to prepare multiple types of coke with a constant dough strength, and the correlation between the average particle size of coke and the drum strength index DI was experimentally determined using samples with varying dough strength. Even if it is obtained, it does not accurately represent the correlation between the average particle size and the drum intensity index DI, and is not very good for ensuring the accuracy of the control index. According to a logical simulation simulating a coke drum test, it is preferable because the correlation between the average particle size of coke and the drum strength index DI can be obtained after keeping the dough strength constant. In this embodiment, the correlation between the average particle size of coke and the drum intensity index DI was specified by using the coke pulverization model described below. The coke pulverization model is not limited to the method described below, and for example, the particle size distribution after coke pulverization can be predicted using the model of Arima et al. (Iron and Steel (1992), pp. 1101-1108). good.

(Coke powdering model)
Next, the coke pulverization model will be described. Hereinafter, a method of calculating the average particle size MS of coke and the drum intensity index DI from the particle size distribution of the coke sample subject to quality control using the coke powdering model will be described.

First, coke subject to quality control is collected in the middle of the transport route described later, and the initial particle size distribution of the collected coke is measured. The initial particle size distribution can be measured using a sieve, and for example, a sieve according to JIS Z8801 can be used. Then, the Rosin-Rammler equation represented by the following equation (1) is applied to the initial particle size distribution to statistically reproduce the initial particle size distribution. The initial particle size distribution is a measurement result using a sieve, and the particle size classification of coke is defined according to the sieve size. Therefore, in order to eliminate the roughness of the particle size division and obtain a continuous particle size distribution, the Rossin-Rammler equation is applied to statistically reproduce the initial particle size distribution.

In the above formula (1), R (D _p ) is a sieve (residual) distribution (%), D _p is the particle size of coke, a is a constant, and n is an equal number (more than 1). Is.

Next, among the initial particle size distributions obtained by the above formula (1), the following formulas (2) to (7) are applied to each particle size from 1 mm to the maximum particle size to obtain particles having a single particle size. , The particle size distribution after applying the impact energy when the drum is rotated 150 times is obtained for each particle size.

In the above formulas (2) to (7), R (Dp, t) is the subsieving ratio (%) of the coke crushed powder to which the impact energy is applied, and Dp is the coke before the impact energy is applied. The particle size (mm). Dp _max is the maximum particle size (mm) of the coke crushed powder to which impact energy is applied, and Φ is the pulverization index. β is the particle size distribution index of the uncrushed particles, and γ is the particle size distribution index of the crushed particles. e is the impact energy (J / kg), and t is the rotation speed of the drum (150 rev.). Dp _s is the subsieving particle diameter (mm) of the coke before impact energy is applied, and V is the speed at which the coke collides with the drum (referred to as collision speed) (m / s). [E / M] is the pulverization resistance energy (J / kg), and x is the number of times the coke collides with the drum (referred to as the number of collisions) by rotating the drum once.

By calculating the impact energy e based on the above formula (3) and calculating the pulverization resistance energy [E / M] based on the above equation (7), the pulverization index is calculated based on the above equation (4). Φ can be calculated. Then, by substituting the pulverization index Φ, the particle size distribution index β calculated from the above formula (5), and the particle size distribution index γ calculated from the above formula (6) into the above formula (2), it is simple. The subsieving ratio R (Dp, t) after applying impact energy to particles having a particle size Dp can be calculated.

The particle size distribution index β is a parameter that determines the particle size distribution of the coke mass, and the larger the particle size distribution index β, the more likely the coke remains as a mass. The particle size distribution index γ is a parameter that determines the particle size distribution of the crushed particles, and the larger the particle size distribution index γ, the easier it is for fine powder to be generated. Since each particle size distribution index β and γ depend on the subsieved particle size Dps of coke and the number of revolutions _t before applying impact energy, they are represented by the above equations (5) and (6). The pulverization resistance energy [E / M] is the energy required to generate a powder having a unit mass, and the larger the pulverization resistance energy [E / M], the more the pulverization is suppressed. Since the pulverization resistance energy [E / M] depends on the subsieved particle diameter Dps and the rotation speed _t of the coke before the impact energy is applied, it is represented by the above formula (7).

The number of collisions x and the collision velocity V in the above equation (3) can be calculated by motion analysis of coke particles in the drum by the discrete element method (DEM). For example, the number of collisions x is 1.5 times. The collision speed V can be 5.0 (m / s). Further, since the maximum particle size Dp _max of the crushed powder is not more than 1/2 of the particle size Dp, the maximum particle size Dp _max of the crushed powder can be 1/2 Dp. Further, δ in the above equation (7) is a correction coefficient, and is used to match the calculated value of the drum intensity index DI with the actually measured value. By setting the correction coefficient δ to be constant for a plurality of types of coke, the dough strength of the plurality of types of coke can be regarded as constant on the coke pulverization model.

Next, the particle size distribution (sub-sieving ratio R (Dp, t) calculated from the above formula (2)) after applying impact energy to particles having a single particle size is described above based on the following formula (8). By weight apportioning with the initial particle size distribution specified by the equation (1), the particle size distribution of coke after applying impact energy can be obtained.

In the above formula (8), R (Dp, t) is the subsieving ratio (%) after applying impact energy to coke, and R (Dp, t) _ij is impact on particles having a single particle size. It is the subsieving ratio (%) after applying energy. X is the weight ratio (initial weight ratio) of coke before applying impact energy. Subscript i is the particle size (mm) of the coke before the impact energy is applied, subscript j is the subsieved particle size (mm) of the coke after the impact energy is applied, and k is the initial particle size distribution. Is the maximum particle size of. As the subsieving ratio R (Dp, t) _ij , the value calculated by the above formula (2) is used. As described above, the particle size i is a value from 1 mm to the maximum particle size k in the initial particle size distribution. Further, as described above, since the maximum particle size Dp _max of the crushed powder was set to 1/2 Dp, the subsieved particle size j is a value from 0.5 mm to the maximum particle size k in the initial particle size distribution.

If the particle size distribution R (Dp, t) of coke after applying impact energy is obtained, the average particle size MS and the drum intensity index DI can be obtained based on this particle size distribution R (Dp, t). For the drum strength index DI, for example, the mass percentage of coke having a particle size of 15 mm or more may be calculated in the particle size distribution R (Dp, t).

The correlation between the average particle size of coke and the drum intensity index DI is expressed by the following equation (9).

In the above formula (9), MS ₀ is the average particle size (reference value) [mm] of coke, and DI ₀ is the drum intensity index (reference value) [%] of coke. DI is the drum intensity index [%], and MS is the average particle size [mm] of coke. α is a coefficient [% / mm].

FIG. 1 shows the correlation between the average particle size MS of coke and the drum intensity index DI. The white circles (◯) shown in FIG. 1 indicate the values obtained by calculating the drum intensity index DI using a coke pulverization model for a plurality of types of coke having different average particle diameters. Further, the straight line (dotted line) L shown in FIG. 1 represents the above equation (9). In the example shown in FIG. 1, a coke sample was collected on the exit side of a coke dry fire extinguishing system (CDQ, Coke Dry Quenching), and the coefficient α at this time was −0.07.

Here, in order to specify the correlation between the average particle size of coke and the drum intensity index DI, the position where coke is collected will be described below.

The position for collecting coke may be in the middle of the path (referred to as the transfer path) for transporting the coke extruded from the coke oven to the blast furnace, and can be appropriately determined in consideration of the position where it is easy to collect. Here, the transport path of coke will be described with reference to FIG. FIG. 2 is a diagram showing an example of a coke transport path.

The transport path 10 is a path until the coke is extruded from the coke oven 11 and transported to the stock level (predetermined position) 16a of the raw material inside the blast furnace 16. In the transport path 10, the coke is first extruded from the coke oven 11 that produces the coke. The coke (red hot coke) extruded from the coke oven 11 is conveyed to a coke dry fire extinguishing system (CDQ, Coke Dry Quenching) 12 and cooled. The coke cooled by the CDQ 12 is carried out from the CDQ 12 and carried into the raw material tank 13. The raw material tank 13 carries out the coke at a predetermined speed so that a predetermined amount of coke is maintained inside the raw material tank 13. The coke carried out from the raw material tank 13 is carried into the relay hopper 14.

When a predetermined amount of coke is brought in, the relay hopper 14 carries out all the brought in coke. The coke carried out from the relay hopper 14 is carried into the furnace top bunker 15. Similar to the relay hopper 14, the furnace top bunker 15 carries out all the brought-in coke when a predetermined amount of coke is brought in. Then, the coke carried out from the furnace top bunker 15 falls and is charged inside the blast furnace 16 to reach the stock level 16a inside the blast furnace 16. In the transport path 10, coke travels between the coke oven 11 and the CDQ 12, between the CDQ 12 and the raw material tank 13, between the raw material tank 13 and the relay hopper 14, and between the relay hopper 14 and the furnace top bunker 15. It is conveyed by a belt conveyor. In addition to coke, an iron raw material is charged inside the blast furnace 16.

When coke is collected by the transport path 10 shown in FIG. 2, for example, coke can be collected at the collection position P1 between the CDQ 12 and the raw material tank 13 or the collection position P2 between the raw material tank 13 and the relay hopper 14. ..

When the coke is transported from the coke oven to the blast furnace, the coke is shocked. For example, the impact energy received by coke includes drop impact energy and moving impact energy. The drop impact energy is the impact energy received when the coke falls and collides with a falling surface (for example, a belt conveyor or a stock level 16a). The coke falls, for example, when the coke transfers between belt conveyors having different heights and when the coke is charged from the furnace top bunker 15 into the blast furnace 16. The moving impact energy is the impact energy received when the coke moves downward inside each of the raw material tank 13, the relay hopper 14, and the furnace top bunker 15.

When the coke is impacted, the coke is destroyed. In particular, the larger the particle size of coke, the more likely it is that coke destruction (particularly volume destruction) will occur. Fracture of an object (particle) is roughly divided into volume destruction and surface destruction. Volume destruction is a volumetric destruction that divides particles into large pieces, and surface destruction is the compression of the surface of particles to produce fine particles. It is the destruction that occurs. Volumetric fracture occurs from cracks and defects in coke, for example, volumetric fracture produces powder having a particle size of 6 to 15 mm. Therefore, the more likely the volume of coke is to be destroyed, in other words, the larger the particle size of coke, the lower the drum strength index DI of coke.

As described above, since the coke is subjected to a plurality of impacts while moving along the transport path, the measured average particle size and the drum strength index change depending on the coke collection position. When coke is collected on the upstream side of the transport path, the coke is not easily affected by the volume breakdown in the transport process from the coke oven to the sampling position, so that the particle size of the coke is greatly reduced by the volume breakdown by the drum test. Therefore, the absolute value of the coefficient α in the above equation (9) becomes large, and the slope of the straight line (dotted line) L descending to the right becomes large. When coke is collected on the downstream side of the transport path, the coke particle size does not significantly decrease even in the drum test because the coke is already strongly affected by the volume destruction in the transport process from the coke oven to the sampling position. Therefore, the absolute value of the coefficient α in the above equation (9) is small, and the slope of the downward-sloping straight line (dotted line) L is small. According to the coke pulverization model, the coefficient α is smaller than 0 and can be any value within the range of −0.07 or more.

When determining whether the quality of the collected coke meets the criteria of the control index, similarly, the coke is collected in the middle of the transport path, and the average particle size MS and the drum intensity index DI are measured for the collected coke. do. Then, it is determined whether or not the measured average particle size MS and the drum intensity index DI satisfy the control index determined based on the above equation (9). That is, when the measured drum intensity index DI is equal to or greater than the intensity index DI corresponding to the average particle size MS measured in the correlation represented by the above equation (9), the control index is satisfied. On the contrary, when the measured drum intensity index DI is less than the intensity index DI corresponding to the average particle size MS measured in the correlation shown in the above equation (9), the control index is not satisfied.

As described above, since the coke receives a plurality of impacts while moving along the transport path, the average particle size MS and the drum intensity index DI change depending on the coke collection position. Therefore, as the coefficient α, the average particle size (reference value) MS ₀ , and the drum intensity index (reference value) DI ₀ shown in the above formula (9), values corresponding to the coke collection position are preferably used, and coke is preferable. The coke sample collection position for determining the correlation between the average particle size MS and the drum intensity index DI and the coke collection position for determining whether the quality of the collected coke meets the criteria of the control index are It is better to make it the same.

Here, when the average particle size MS and the drum strength index DI of the collected coke satisfy the control index, it is determined that a process for improving the quality of the coke (referred to as a quality improvement process) is unnecessary. On the other hand, when the average particle size MS and the drum strength index DI of the collected coke do not satisfy the control index, it is judged that the quality improvement treatment is necessary. In the quality improving process, for example, a process for improving the drum strength index DI of coke is performed, and a known process can be appropriately adopted. For example, the drum strength index DI of coke can be improved by increasing the blending ratio of the strong caking coal or increasing the addition amount of the caking material.

The average particle size (reference value) MS ₀ and the drum strength index (reference value) DI ₀ can be determined based on the past operation results when the operation of the blast furnace was stable. Conventionally, when determining the management index (average particle size MS and drum strength index DI) in consideration of the operation results of the blast furnace, the lower limit values of the average particle size MS and the drum intensity index DI are determined, so this lower limit value is used. The drum strength index (reference value) DI ₀ and the average particle size (reference value) MS ₀ can be set.

According to the past operation results of the blast furnace, for example, as a control index for controlling the quality of coke, the drum strength index DI is 84.5% or more, and the average particle size is 52 mm or more. Therefore, the drum strength index (reference value) DI ₀ can be set to 84.5%, and the average particle size (reference value) MS ₀ can be set to 52 mm. Since the control index (average particle size MS and drum intensity index DI) changes according to the operating conditions of the blast furnace, the average particle size (reference value) MS ₀ and the drum intensity index (reference value) DI ₀ are described above. It is not limited to the value.

On the other hand, the drum strength index (reference value) DI ₀ and the average particle diameter are taken into consideration, not from the past operation results of the blast furnace, which is whether or not the operation was stable, but by considering the ventilation resistance index KR (1 / m) of the blast furnace. (Reference value) MS ₀ can be determined. The aeration resistance index KR is an index showing the aeration in the blast furnace when the entire blast furnace is regarded as a solid air packed bed, and is a value that does not depend on the flow velocity in the blast furnace. The draft resistance index KR is expressed by the following equation (10).

In the above equation (10), ΔP is the pressure loss in the blast furnace (kg / m ² ), L is the height of the blast furnace (m), g _c is the gravity conversion coefficient (kg · m / kg · sec ² ), and μ is The mixed gas average viscosity coefficient (kg / m · sec), ρ is the average gas density (kg / m ³ ), u is the average gas flow velocity (m / sec), and β is the correction coefficient (−). The correction coefficient β varies depending on the operating conditions of the blast furnace, but can be, for example, 0.6.

The lower the aeration resistance index KR, the better the aeration in the blast furnace. In other words, the higher the aeration resistance index KR, the worse the aeration in the blast furnace. Therefore, as a control index for controlling the quality of coke, the drum strength is in a state where the air permeability in the blast furnace is not deteriorated, that is, when the air flow resistance index KR is lower than a predetermined value. The values of the exponent (reference value) DI ₀ and the average particle size (reference value) MS ₀ may be adopted. The predetermined value can be appropriately determined in consideration of the fact that stable operation of the blast furnace is maintained. For example, the draft resistance index KR can be determined to be 13000 [1 / m] or less.

Specifically, after confirming that the draft resistance index KR is lower than the predetermined value in the actual operation of the blast furnace, the drum strength index DI and the average particle size MS of the coke charged into the blast furnace at this time are used. Should be specified. Then, the specified drum intensity index DI can be set to the drum intensity index (reference value) DI ₀ , and the specified average particle size MS can be set to the average particle size (reference value) MS ₀ . For example, the drum intensity index (reference value) DI ₀ can be set to 84.8%, and the average particle size (reference value) MS ₀ can be set to 52 mm.

When controlling the quality of coke, the production of coke is such that the average particle size MS and drum intensity index DI of the collected coke are located in the region R1 shown by hatching in FIG. 3 or in the region R2 shown by hatching in FIG. Control the condition. In FIG. 3, the region R1 is a region where the drum intensity index DI is higher than the boundary line L1, and the boundary line L1 is a management index specified by the above equation (9). In FIG. 4, the region R2 is a region where the drum intensity index DI is higher than the boundary line L2, and the boundary line L2 is a management index specified by the above equation (9).

With respect to the boundary line L1 shown in FIG. 3, the coefficient α shown in the above equation (9) is −0.07, the average particle diameter (reference value) MS ₀ is 52 mm, and the drum intensity index (reference value) DI ₀ is. It is 84.5%. With respect to the boundary line L2 shown in FIG. 4, the coefficient α shown in the above equation (9) is −0.07, the average particle diameter (reference value) MS ₀ is 52 mm, and the drum intensity index (reference value) DI ₀ is. It is 84.8%.

When controlling the quality of coke based on the control index shown in FIG. 3, first, the average particle size MS and the drum strength index DI of the coke produced from the coke oven are measured. If the average particle size MS and the drum intensity index DI are located in the region R1 shown in FIG. 3, it is not necessary to change the coke manufacturing conditions. On the other hand, if the average particle size MS and the drum intensity index DI are located outside the region R1 shown in FIG. 3, the coke manufacturing conditions are changed.

When the average particle size MS and the drum intensity index DI are located outside the region R1, the average particle size MS and the drum intensity index DI are increased by increasing the average particle size MS and the drum intensity index DI. Can be located within region R1. Therefore, the coke manufacturing conditions may be changed so that the average particle size MS becomes large and the drum strength index DI becomes high.

When controlling the quality of coke based on the control index shown in FIG. 4, first, the average particle size MS and the drum strength index DI of the coke produced from the coke oven are measured. If the average particle size MS and the drum intensity index DI are located in the region R2 shown in FIG. 4, it is not necessary to change the coke manufacturing conditions. On the other hand, if the average particle size MS and the drum intensity index DI are located outside the region R2 shown in FIG. 4, the coke manufacturing conditions are changed.

When the average particle size MS and the drum intensity index DI are located outside the region R2, the average particle size MS and the drum intensity index DI are increased by increasing the average particle size MS and the drum intensity index DI. Can be located within region R2. Therefore, the coke manufacturing conditions may be changed so that the average particle size MS becomes large and the drum strength index DI becomes high.

Conventionally, when controlling the quality of coke, the lower limit of the average particle size MS of coke and the lower limit of the drum strength index DI of coke have been uniquely determined. In this case, the coke manufacturing conditions are controlled so that the average particle size MS and the drum intensity index DI of the coke are located within the region R3 shown by hatching in FIG. The region R3 is a region in which the average particle size MS is the lower limit value MS_low (here, 52 mm) or more, and the drum intensity index DI is the lower limit value DI_low (here, 84.5%) or more. The lower limit value MS_low shown in FIG. 5 is the same as the average particle size (reference value) MS ₀ shown in FIG. 3, and the DI_low shown in FIG. 5 is the same as the drum intensity index (reference value) DI ₀ shown in FIG.

According to the conventional management method, when the average particle size MS of coke is lower than the lower limit value MS_low, it is necessary to change the manufacturing conditions of coke so that the average particle size MS of coke is equal to or more than the lower limit value MS_low. .. According to the management method of the present embodiment, as can be seen from FIG. 3, even if the average particle diameter MS of coke is lower than the average particle diameter (reference value) MS ₀ , the drum intensity index DI of coke is shown in FIG. If it is located in the region R1, it is not necessary to change the coke manufacturing conditions. That is, even if the coke has an average particle size MS and a drum intensity index DI outside the region R3 shown in FIG. 5, it is not necessary to change the coke manufacturing conditions. Even when the management index shown in FIG. 4 is used, it is the same as when the management index shown in FIG. 3 is used.

Further, according to the conventional management method, when the coke drum strength index DI is lower than the lower limit DI_low, it is necessary to change the coke manufacturing conditions so that the coke drum strength index DI is equal to or higher than the lower limit DI_low. there were. According to the management method of the present embodiment, as can be seen from FIG. 3, even if the drum intensity index DI of coke is lower than the drum intensity index (reference value) DI ₀ , the average particle size MS of coke is shown in FIG. If it is located in the region R1, it is not necessary to change the coke manufacturing conditions. That is, even if the coke has an average particle size MS and a drum intensity index DI outside the region R3 shown in FIG. 5, it is not necessary to change the coke manufacturing conditions. Even when the management index shown in FIG. 4 is used, it is the same as when the management index shown in FIG. 3 is used.

Furthermore, when the control index shown in FIG. 4 is used, according to the conventional management method, even if the coke is located in the region R3 shown in FIG. 5, that is, the average particle size MS of the coke is the lower limit. Even if the value is MS_low or more and the coke drum intensity index DI is the lower limit DI_low or more, the coke average particle size MS and the coke drum intensity index DI may not be located in the region R2. In other words, the control index has been partially tightened, and it is determined that coke that meets the control index with the conventional management method does not meet the control index because it causes deterioration of the air permeability of the blast furnace, and the coke manufacturing conditions. Need to be changed.

Next, examples of the present invention will be described, but the present invention is not limited thereto.

6 to 8 show the relationship between the coke drum strength index DI and the blast furnace aeration resistance index KR analyzed using past operation data in an actual blast furnace. The draft resistance index KR was calculated based on the above equation (10). Here, the aeration resistance index KR depends on the tapping ratio and coke ratio of the blast furnace, but in order to eliminate these effects as much as possible, constraint conditions are set for the tapping ratio and coke ratio, and the tapping ratio and coke ratio are set. The aeration resistance index KR was calculated based on the data when the coke ratio satisfied the constraint condition. Here, as a constraint condition of the tapping ratio, the tapping ratio is 2.0 [t / d / m ³ ] or more, and as a constraint condition of the coke ratio, the coke ratio is 360 [kg / pt] or less. ..

In FIG. 6, white circles (◯) are operation data in blast furnace operation using coke located in the region R1 shown in FIG. 3, that is, coke satisfying the control index, and black circles (●) are shown in FIG. It is the operation data in the blast furnace operation using the coke located outside the region R1, that is, the coke that does not satisfy the management index.

In FIG. 7, white circles (◯) are operation data in blast furnace operation using coke located in the region R2 shown in FIG. 4, that is, coke satisfying the control index, and black circles (●) are shown in FIG. It is the operation data in the blast furnace operation using the coke located outside the region R2, that is, the coke that does not satisfy the management index.

In FIG. 8, white circles (◯) are operation data in blast furnace operation using coke located in the region R3 shown in FIG. 5, that is, coke satisfying the control index, and black circles (●) are shown in FIG. It is the operation data in the blast furnace operation using the coke located outside the region R3, that is, the coke that does not satisfy the management index.

Comparing FIGS. 6 and 8, in the present embodiment (FIG. 6), the draft resistance index KR is within a range lower than that of the conventional case (FIG. 8) (specifically, a range of 12500 [1 / m] or less). (Inside), the number of black circles is decreasing. As described above, the lower the ventilation resistance index KR, the better the ventilation in the blast furnace. Therefore, by setting the control index as in the present embodiment, the ventilation resistance index KR is compared with the conventional case (FIG. 8). Since the number of black circles is reduced within a low range (specifically, within a range of 12500 [1 / m] or less), it is possible to suppress unnecessary quality improvement processing. Therefore, according to the present embodiment, the quality control of coke is more appropriate than in the past.

Comparing FIGS. 7 and 8, in the modified example (FIG. 7) of the present embodiment, the draft resistance index KR is within a range lower than that of the conventional (FIG. 8) (specifically, 12500 [1 / m]]. The number of black circles is decreasing in the following range). As described above, the lower the ventilation resistance index KR, the better the ventilation in the blast furnace. Therefore, by setting the control index as in the modified example of the present embodiment, the ventilation is improved as compared with the conventional case (FIG. 8). Since the number of black circles is reduced within the range where the resistance index KR is low (specifically, within the range of 12500 [1 / m] or less), it is possible to suppress unnecessary quality improvement processing. Therefore, according to the present embodiment, the quality control of coke is more appropriate than in the past.

In FIG. 7, the number of black circles increases within the range where the draft resistance index KR is higher (specifically, in the vicinity of 15000 [1 / m]) as compared with FIGS. 8 and 6. This is because the management index has been partially tightened, and it has been determined that coke that meets the management index with the conventional management method does not meet the management index because it causes deterioration of the air permeability of the blast furnace. Black circles in the range where the aeration resistance index KR is high (specifically, around 15000 [1 / m]) are cases where the drum strength index DI is near the conventional lower limit DI_low, but the aeration resistance index KR is high. Operation data. As described above, the higher the ventilation resistance index KR, the worse the air permeability in the blast furnace. Therefore, by setting the control index as shown in FIG. 4, the ventilation resistance index KR is within a high range (specifically,). , 15000 [1 / m]), the number of black circles increases, and the quality of coke can be improved by the quality improvement process.

10: Transport route, 11: Coke furnace, 12: Coke dry fire extinguishing equipment, 13: Raw material tank,
14: Relay hopper, 15: Furnace top bunker, 16: Blast furnace, 16a: Stock level,
P1, P2: Collection position

Claims (5)

It is a quality control method that controls the quality of coke charged in the blast furnace.
Using the coke pulverization model when the dough strength is the same, the correlation between the average particle size of coke and the strength index is obtained in advance, and the strength index of coke corresponds to the average particle size of coke in the correlation. It is defined as a management index for controlling the quality of coke that it is equal to or higher than the strength index.
The average particle size and strength index of the coke collected in the middle of the transport path for transporting the coke to the blast furnace are measured, and it is determined whether or not the average particle size and the strength index satisfy the control index.
The correlation is a quality control method characterized in that the larger the average particle size, the lower the intensity index. The intensity index is a drum intensity index, and the correlation is represented by the following formula (I).

Here, MS is the average particle size (mm), DI is the drum intensity index (%), MS ₀ is the reference value (mm) of the average particle size, and DI ₀ is the drum intensity index. Is the reference value (%) of, and α is a coefficient.
The quality control method according to claim 1. The quality control method according to claim 2, wherein the coefficient α is −0.07. The reference value MS ₀ of the average particle size is the lower limit value of the average particle size determined from the past operation results when the operation of the blast furnace is stable.
The second or third claim, wherein the reference value DI ₀ of the drum strength index is the lower limit value of the drum strength index determined from the past operation results when the operation of the blast furnace is stable. Quality control method. The reference value MS ₀ of the average particle diameter is the average particle diameter when the aeration resistance index of the blast furnace is equal to or less than a predetermined value.
The quality control method according to claim 2 or 3, wherein the reference value DI ₀ of the drum strength index is a drum strength index when the ventilation resistance index of the blast furnace is equal to or less than the predetermined value.

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