JP5455813B2 - Method for evaluating reduced powder properties of sintered ore - Google Patents

Description

  The present invention relates to a method for evaluating reduced powdering properties of sintered ore, and more specifically, reduced powdering properties due to changes in reducing conditions when the sintered ore charged in the blast furnace descends in the blast furnace. It relates to a method for accurately evaluating changes over time, and in particular, to accurately evaluate changes in the reduced powdering properties of sintered ore when changing the blast furnace operating conditions, such as hydrogen injection from the tuyere. The present invention relates to a method for evaluating reduced powdering properties.

  It is known that the sinter charged in the blast furnace is pulverized by the volume expansion that occurs when the hematite in the sinter is reduced and magnetite is produced at the initial low temperature stage of reduction. . This pulverization phenomenon significantly hinders ventilation in the blast furnace, causing unloading failure and shelves. Therefore, the stable operation of the blast furnace can reduce the pulverization of the sintered ore charged in the blast furnace. It is extremely important to accurately grasp the properties, particularly the reduction powder rate and the change with time of the reduction rate.

By the way, as a method for evaluating the reduced powdering property of sintered ore, an “iron ore-low temperature reduced powdering test method” defined in JIS M8720 is known. In this evaluation method, iron ore adjusted to a size of 10 to 15 mm is heated to a temperature of 550 ° C., isotherm reduced with a mixed gas of CO: 30 vol% and N ₂ : 70 vol%, cooled, and then rotated at room temperature. After rolling using a drum, sieving and obtaining a ratio (%) of 3 mm or less, the degree of pulverization (reduction pulverization rate: RDI) under conditions simulating a low temperature reduction zone of a blast furnace It is something to evaluate.

  However, since the method defined in JIS M8720 performs a reduction test using a mixed gas having a constant temperature of 550 ° C. and a constant component composition, it is used in a blast furnace during actual operation, particularly at a high temperature of 550 ° C. or higher. There is a problem that the reduced powdering properties of sintered ore cannot be evaluated correctly.

In view of this, several methods have been proposed for evaluating the reduced powdering properties of sintered ore in consideration of the conditions in the blast furnace during actual operation.
For example, in Patent Document 1, in the method for evaluating the reduction powdering property of raw material sintered ore supplied to a blast furnace, each of the constant reduction time and constant reduction potential of the sintered ore set to a predetermined value in advance is described. For the constant reduction time, a `` heat transfer model '' is set to evaluate the heat transfer between gas and solids in the blast furnace interior and gas. The temperature distribution in the blast furnace is estimated using the conditions, and the sinter retention time required for the raw material sintered ore to pass through the temperature range of 500 to 600 ° C. in the furnace is calculated. The standard reduction time is calculated by correcting the time, and for the constant reduction potential, a “general material balance model” for the blast furnace shaft during actual operation is set, and the shaft gas composition and shaft gas are calculated using the actual operation conditions. Flow rate Estimate and calculate the reduction potential in the shaft, correct the constant reduction potential according to this result, calculate the standard reduction potential, and then calculate the conditions for the properly corrected standard reduction time and standard reduction potential. A test method is disclosed in which a reduction test is performed to evaluate reduced powdering properties of sintered ore.

In addition, high temperature properties and softening and melting behavior of sintered ore in a blast furnace are examined using a test furnace that simulates a blast furnace shaft portion. For example, in Non-Patent Document 1, in the load reduction test method based on approximate blast furnace conditions, the effects of load, gas flow rate, sample particle size and packed bed height on the test results and their appropriate combinations are comprehensively described. The results of the study are reported. Specifically, a mixed gas of N ₂ —CO—CO ₂ controlled to a predetermined composition and flow rate by a gas mixing / supplying device is introduced into a Tamman furnace through a gas preheating furnace, and a graphite crucible in the Tamman furnace is introduced. It describes that the high temperature property of the blast furnace charge is measured by reducing the sample filled in the sample under a predetermined load and temperature condition (1100 ° C., 1300 ° C., 1400 ° C.).

  Also, Non-Patent Document 2 describes an experimental apparatus that can comprehensively simulate reactions such as reduction, softening, and melting along the blast furnace height direction in order to investigate the reduction behavior of sintered ore under blast furnace approximate conditions. (Blast furnace reaction simulator (BIS)) has been developed, and an example of investigating the reduction behavior of sintered ore simulating the conditions in the blast furnace using the experimental equipment has been reported.

The BIS is composed of an upper furnace and a lower furnace, and the upper furnace simulates a blast furnace block, which is vertically movable along a stainless steel reaction tube and divided into four zones. It consists of an electric furnace capable of temperature control independently for each zone, and the lower furnace is a furnace corresponding to a load softening test device from the lower end of the massive band to the fusion and dripping zone. A graphite sample crucible and an electric furnace , Consisting of a load device and a drop finder.
In this BIS, after charging sintered ore and coke as a sample in a reaction tube, a temperature distribution corresponding to the blast furnace lumps is given to the electric furnace while flowing N ₂ gas. By lowering at a constant rate, the lower furnace sample is given a reduction history from the top of the furnace to the bottom of the massive band, and then softening, melting, and dripping at any heating rate set in the lower furnace. By proceeding with the test, it is possible to simulate the in-furnace reaction from the top of the blast furnace to the molten dripping.

In Non-Patent Document 2, a mixed gas of N ₂ : 55 vol%, CO: 41 vol%, H ₂ : 4 vol% is introduced into the apparatus using the BIS, and rapidly from the furnace top to 1000 ° C. Two types of temperature distribution: a distribution having a relatively long heat storage zone at 1000 ° C., a distribution having a low temperature heat storage zone of 600 ° C., and a distribution having two stages of heat storage zones of 1000 ° C. Reported that the reduction behavior, reduced powdering behavior and pore structure change of the massive band were investigated.

JP-A-11-61284

Yojiro Yamaoka, Hirohisa Horita, Shinji Kajikawa, “Method of measuring high temperature properties of blast furnace charge”, Iron and Steel, Japan Iron and Steel Institute, 66th (1980), p. 1850-1859 Okamoto, Satoshi Naito, Katsuya Ax, Yoichi Hayashi, Yoshihiro Inoue, "Reduction behavior of sintered ore under approximate conditions in blast furnace", Iron and Steel, Japan Iron and Steel Institute, 72nd (1986), p. 1529-1536

Although the evaluation method of Patent Document 1 described above evaluates the reduced powder properties of sintered ore in consideration of the conditions in the blast furnace, the N ₂ —CO—CO ₂ —H ₂ mixed gas having a constant composition is used. The reduction test is conducted only at a temperature of 550 ° C. However, when the reduction temperature and gas composition are fixed, the reduction powder property changes at a temperature of 550 ° C. or higher, or the reduction powder property change when the gas composition fluctuates, that is, the sintering charged in the blast furnace. In the process of ore descending in the blast furnace, it is not possible to fully grasp how the reduction rate and reduction powdering rate change due to changes in the temperature in the furnace and the reducing atmosphere in the furnace.

  Further, although the evaluation method of Non-Patent Document 1 performs a reduction test at a temperature other than 550 ° C., the reduction test is performed at a high temperature of 1000 ° C. or higher and only at a constant temperature and a constant gas composition. Therefore, it is still not an evaluation method reflecting the change of the reduction conditions in the process of the sintered ore charged in the blast furnace descending the blast furnace.

In addition, although the evaluation method of Non-Patent Document 2 conducts tests under conditions simulating the conditions in the blast furnace, since the composition of the reducing gas is still constant, for example, blast furnace operation such as hydrogen injection is performed. It is not possible to sufficiently evaluate the change in reduced powder properties of sintered ore when the conditions are changed.
Therefore, since the conventional method for evaluating the reduced powdering property of sintered ore cannot fully grasp the change in the reduced powdering property that occurs in the blast furnace, the blast furnace trouble due to the change in the reduced powdering property is prevented in advance. It is impossible.

  The present invention has been made in view of the above-described problems of the conventional evaluation method for reducing powder properties, and the purpose thereof is sintering by changing the reduction conditions over time when the sintered ore descends in the blast furnace. To propose a method for evaluating the reduced powdering properties of sintered ore that can accurately evaluate changes in the reduced powdering properties of ores and changes in reduced powdered properties of sintered ores due to changes in blast furnace operating conditions. is there.

  The inventors have intensively studied to solve the above problems. As a result, the time-dependent change in the reduction conditions when the sinter charged in the blast furnace descends in the blast furnace, that is, the reducing gas composition and the reduction temperature that change with the elapsed time after charging, are summarized in the overall heat mass balance. If the sinter ore reduction test is performed under conditions that accurately estimate the model and partial balance model, etc., and simulate the time-dependent changes in the reduction conditions, the reduced powder properties of the sinter charged in the blast furnace As a result, it was found that not only the change with time but also the change in reduced powdering properties of sintered ore due to changes in blast furnace operating conditions can be accurately evaluated, and the present invention has been completed.

  That is, the present invention estimates the time-dependent change of the reduction condition when the sintered ore descends in the blast furnace in evaluating the reduced powdering properties of the sintered ore used for blast furnace operation, and the estimated reduction condition This is a method for evaluating the reduced powder properties of sintered ore, characterized by performing a reduction test of sintered ore simulating the time-dependent change of sinter and measuring and evaluating the reduced powder rate of sintered ore after reduction. .

The evaluation method of the reduced pulverization property of the sintered ore of the present invention is a sintered ore that simulates the change over time of the reducing conditions when the sintered ore descends in the blast furnace by the following treatments (A) to (C). The reduction test conditions are set, and the reduction test of the sintered ore (D) below is performed.
(A) A general heat mass balance model for analyzing the blast furnace operation from both the material balance and the heat balance is set, and the blast furnace operation conditions are calculated by inputting the blast furnace operation conditions into the general heat mass balance model.
(B) The inside of the blast furnace is divided into meshes, partial balance models for calculating the mass balance and heat balance are set for each mesh, and the blast furnace operating conditions calculated in (A) above are calculated for the partial balance model. Input the operation specifications and calculate the temperature distribution and gas composition distribution inside the blast furnace and the descending speed in the charging furnace.
(C) Based on the temperature distribution and gas composition distribution inside the blast furnace calculated in (B) above, and the descending speed in the charging furnace, the time-dependent change in the reduction condition of the sintered ore descending in the blast furnace is estimated, and the estimated firing Simulating the time-dependent change of the reduction condition of the ore, the reduction gas composition and the reduction temperature are set with respect to the reduction time in the reduction test of the sintered ore.
(D) Under the conditions set in (C) above, the sintered ore reduction test is performed to a temperature of 900 ° C. or lower while the temperature is raised from the blast furnace top temperature.

  Moreover, the evaluation method of the present invention is characterized in that the reduction test of the sintered ore is performed while applying a load to the sintered ore.

According to the present invention, the change over time of the reduction condition when the sintered ore charged in the blast furnace descends in the blast furnace is accurately grasped, and the reduction test of the sintered ore is performed by simulating the condition. By measuring the reduced powdering rate, it is possible to accurately evaluate and predict the change over time of the reduced powdered property charged in the blast furnace. In particular, according to the present invention, in addition to the introduction of coke from the top of the furnace, the blowing of pulverized coal from the tuyere, which was a common method for supplying reducing material to a conventional blast furnace, the blowing of hydrogen from the tuyere was performed. Even if the blast furnace operating conditions are changed as expected, it is possible to accurately predict changes in the reduction conditions within the blast furnace, so the changes in reduced pulverization properties accompanying changes in the blast furnace operating conditions can be accurately evaluated and predicted. can do.
Furthermore, by applying the evaluation method of the present invention to the actual operation of the blast furnace, the blast furnace operating conditions are optimized according to the reduced powdering properties of the sintered ore charged in the blast furnace, or in accordance with the blast furnace operating conditions. Since it is possible to use sintered ore with the optimal reduced powdering properties, it is possible to predict and prevent blast furnace operation troubles in advance, which can greatly contribute to the stabilization of blast furnace operation. it can.

It is a figure explaining the evaluation method of the reduced powdering property of the sintered ore concerning this invention. It is a figure explaining the mesh used for calculation of the partial balance model. It is a schematic diagram of the blast furnace shaft part simulation test apparatus used for a reduction test. It is a figure which shows the temperature distribution in the blast furnace obtained using the partial balance model. It is a graph which shows the temperature rising pattern used for the reduction test of an Example. It is a graph which shows the load pattern loaded on the sintered ore in the reduction test of an Example. Reducing the maximum temperature in the CO reduction and CO + H ₂ reduction and is a graph showing the relationship between reduction rate. It is a graph showing the relationship between reducing the upper limit temperature and the reduction degradation rate of CO reduction and CO + H ₂ reduction.

  The present invention accurately evaluates the change over time of the reduced powdering property of the sinter in the blast furnace by simulating the reduction conditions in the blast furnace in the actual operation of the blast furnace and conducting the reduction test of the sintered ore while raising the temperature. By applying the evaluated results to actual blast furnace operation, it is possible to accurately predict changes in the reduction status in the blast furnace and to prevent problems that occur in the blast furnace. Technology. In particular, in the present invention, hydrogen is blown from the tuyere in addition to conventional coke charging from the top of the furnace and pulverized coal blowing from the tuyere, which was a general reducing material supply system to the blast furnace. This is an extremely effective technique for evaluating changes in the reduced powdering properties of sintered ore when the blast furnace operating conditions are changed.

  In the present invention having the above features, as shown in FIG. 1, the general heat mass balance model for analyzing the blast furnace operation from both the material balance and the heat balance is first set. Enter the blast furnace operating conditions to calculate the blast furnace operating specifications, then cut and divide the mesh into blast furnaces, and set the partial balance model to calculate the mass balance and heat balance of each mesh, this partial balance model In addition, the blast furnace operating conditions input in the above general thermal mass balance model and the calculated blast furnace operating specifications are input to calculate the gas composition distribution and temperature distribution at each position in the blast furnace and the descending rate in the charging furnace. Next, from the temperature distribution and gas composition distribution of each position in the blast furnace calculated previously and the descending speed in the charging furnace, the time-dependent change in the reduction condition of the sintered ore descending in the blast furnace, that is, the sintered ore is the blast furnace. Estimate the relationship between the elapsed time after charging and the reducing gas composition and the reducing temperature, and simulate the time course of the estimated reducing conditions to reduce the sinter ore reduction test conditions, that is, the reducing gas with respect to the reducing time. By setting the composition and reaction temperature, performing a reduction test of the sintered ore while raising the temperature under the set conditions, measuring and evaluating the reduced powdering rate and reduction rate of the sintered ore after reduction, It is intended to accurately evaluate the reduced powder properties of sintered ore in a blast furnace.

Hereinafter, the present invention will be specifically described with reference to FIG.
(A) General heat mass balance model analysis The present invention first sets a general heat mass balance model for analyzing the blast furnace operation from both the material balance and the heat balance. As the output, the furnace top gas component, the air flow rate, the air temperature, the air flow moisture, the oxygen enrichment amount, the output amount and the output component, ore unit, coke ratio, reducing material ratio, air supply Calculate the blast furnace operation specifications such as basic unit, oxygen basic unit, slag ratio, solution loss reaction amount, exhaust gas amount. Although there is no restriction | limiting in particular as a general heat mass balance model used for the said calculation, The model called a "list model" can be used preferably.

  Here, the blast furnace operating conditions to be input to the above-mentioned “general heat mass balance model” are the amount of tapping, the type, amount, composition of the tuyere-injected material, and the charging weight ratio of sinter and coke (sintered or coke). Ratio). And in the above-mentioned "general heat mass balance model", the mass balance is about Fe, C, H, contained in all the charged materials such as sintered ore, coke and tuyere blown material charged in the blast furnace. The balance of the Fe, C, H, O, S, and Ash components contained in the O, S, and Ash components and the hot metal and slag discharged from the blast furnace and the exhaust gas is calculated. On the other hand, regarding the heat balance, the amount of heat supplied is the combustion heat of coke, the sensible heat of air, the heat of reduction from iron oxide to iron, etc., and the required amount of heat is the heat of solution of reaction loss, the heat of reduction of oxides contained as impurities, C Heat absorption in iron, sensible heat of molten iron, sensible heat of slag, heat loss from the furnace wall, heat absorption in reactions involving blast moisture, heat absorption in reactions involving additives from tuyere, etc. Calculate the balance between the amount of heat supplied and the amount of heat required. In this way, the mass balance and heat balance of the entire blast furnace are calculated, that is, the blast furnace charge, the amount of air blown, the amount of discharge, the amount of exhaust gas, and the heat input of those charge materials. Using the heat adjustment that takes the difference between the heat output of the exhaust gas and the exhaust gas, the furnace top gas component, the air flow rate, the air temperature, the air humidity, the oxygen enrichment amount, the output amount, the output component, ore unit, coke Calculate the blast furnace operation parameters such as ratio, reducing material ratio, blast unit, oxygen unit, slag ratio, solution loss reaction amount, exhaust gas amount.

(B) Partial balance model analysis Next, as shown in FIG. 2, the inside of the blast furnace is divided by dividing the mesh according to a certain standard, and the partial balance model for calculating the mass balance and heat balance in each mesh portion is calculated. Set the blast furnace operating conditions and the calculated operating specifications that were input to the above-mentioned general thermal mass balance model as the partial balance model, and the temperature distribution, gas composition distribution, and charging furnace descent rate in the blast furnace Is calculated.
In this "partial balance model", the blast furnace operating specifications calculated by the overall thermal mass balance model are satisfied as a whole blast furnace, and the meshes inside the blast furnace are coupled and changed. Calculate the temperature distribution and gas composition distribution in the blast furnace. Specifically, first, it is divided in the axial direction of the blast furnace (furnace height direction) so that the interval is close to the layer thickness of the layered structure in the furnace, and the radial direction of the blast furnace is about the same as the axial direction. The mesh is cut into the size of, and the boundary mesh is provided around them. The triangular mesh which is the minimum unit of the mesh is obtained by dividing the quadrilateral mesh obtained by the above method in a direction in which an obtuse angle is difficult to occur. Gas flow, solid flow, and liquid flow are calculated using a triangular mesh, and heat transfer (temperature) and reaction (gas composition) are calculated using a square mesh. Then, for each mesh, a partial material balance and a partial heat balance for each phase of gas, solid, and liquid are calculated. For details of other calculation methods, refer to the technical document of Kuwahara et al. ("Mathematical two-dimensional model of blast furnace process", Iron and Steel, Japan Iron and Steel Institute, Vol. 77 (1991) No. 10, pp. 1593 to 1600). Be helpful

(C) Setting of reduction test conditions Next, in the present invention, the sintered ore descends in the blast furnace from the previously calculated temperature distribution and gas composition distribution in the blast furnace and the descending speed in the charging furnace. Estimated change in reduction conditions over time, that is, changes in reducing gas composition and reduction temperature with respect to the elapsed time after charging the sintered ore, simulated the estimated reducing conditions, reducing conditions in the reduction test of sintered ore, That is, the reducing gas composition and the reduction temperature that are changed with the reduction time are set.

  Specifically, the temperature increase rate in the reduction test is obtained by averaging the previously calculated temperature distribution in the blast furnace in the radial direction to obtain the average temperature distribution in the furnace height direction of the blast furnace. The change in average temperature with respect to the elapsed time after charging when the ore descends in the furnace is calculated from the rate of descent in the charging furnace calculated by the partial balance model of (B). What is necessary is just to set the time-dependent change of average temperature as a temperature condition in a reduction test.

Further, the gas composition in the reduction test is obtained by averaging the gas composition distribution in the blast furnace calculated previously in the radial direction to obtain the average gas composition distribution in the furnace height direction of the blast furnace, and the average gas composition distribution in the furnace height direction, The change in the average gas composition with respect to the elapsed time after charging when the sintered ore descends in the furnace is obtained from the rate of descent in the charging furnace previously calculated by the partial balance model of (B). What is necessary is just to set the time-dependent change of an average gas composition as a reducing gas composition condition in a reduction test.
In addition, although the relationship between the set reduction time and the gas composition is continuous, in order to simplify the reduction test, the reduction temperature may be divided into several stages and the composition of the reducing gas may be changed. . However, when the gas composition can be automatically controlled, it is of course better to change the composition more finely or to change it continuously.

(D) Reduction test of sintered ore Next, from the blast furnace top temperature, under the conditions that simulated the time-dependent change of the reduction conditions when the sintered ore descended in the blast furnace, set through the above treatment While reducing the temperature, the reduction test of the sintered ore is performed to an arbitrary temperature of 900 ° C. or lower. As an apparatus used for this reduction test, it is preferable to use a blast furnace shaft portion simulation test apparatus capable of performing a reduction test while raising the temperature as shown in FIG.
In addition, although the reduction test of the said sintered ore is implemented in the range to 900 degrees C or less arbitrary temperature rising from blast furnace top temperature, the said blast furnace top temperature is generally about 200-240 degreeC. is there. In addition, the reason for setting the upper limit of the temperature at which the reduction test is performed to 900 ° C. is that when the reduction temperature exceeds 900 ° C., the softening of the sintered ore occurs, so the meaning of evaluating the reduced powder properties is lost. Because it ends up. Therefore, if the reduction test is in an arbitrary temperature range of 900 ° C. or less from the blast furnace top temperature, it is sufficient for evaluating the reduced powder property of the sintered ore. However, since reduction powdering does not occur even if the upper limit temperature is too low, the reduction test is preferably carried out at least up to 500 ° C or higher.

  In the present invention, the upper limit temperature at which the reduction test is performed can be set to an arbitrary temperature of 900 ° C. or less. For example, when the reduction test is completed at 800 ° C., the temperature is raised and reduced to 800 ° C. in the blast furnace. Thus, reduced powder properties of the sintered ore can be obtained. Therefore, by varying the upper limit temperature of the reduction test and measuring and evaluating the reduced pulverization properties, the sinter ore charged into the blast furnace is caused by the change over time in the reduction conditions when the ore is descending the blast furnace. It is possible to accurately grasp the change in the reduced powdering property of the sinter. As described above, in the present invention, the evaluation of the reduced pulverization property of the sintered ore is not performed by fixing the reduction test temperature at one specific temperature, but in a wide temperature range. It is possible to accurately grasp and predict the change in the reduced powdering property in the interior.

  In addition, it is preferable to perform in the reduction | restoration test of the said sintered ore, applying a load to a sample from the meaning which simulates the condition in a blast furnace correctly. In this regard, the blast furnace shaft portion simulation test apparatus shown in FIG. 3 can be preferably used because the test can be performed while raising the temperature while applying a load. The load applied to the sample (sintered ore) is reduced when the blast furnace top side, that is, when the elapsed time after charging is short, with the passage of time, that is, the charged material drops and the static pressure increases. It is preferable to increase the load in accordance with the above. As the load to be applied, for example, an estimated value of the load distribution in the actual blast furnace described in Non-Patent Document 1 can be used.

(E) Evaluation of reduced powdering properties, etc. The sintered ore subjected to the reduction test as described above is then subjected to a tumbler test in accordance with JIS M8712 “Iron Ore-Rotational Strength Test Method”. Measure the rate of conversion and evaluate the reduced powder properties. Alternatively, the reduction rate may be measured according to JIS M8713 “Iron Ore—Reducibility Test Method”.

In this example, as a reducing material blown from coke and tuyere, “CO reduction” using only a carbon-based reducing material of pulverized coal, and a hydrogen-based reducing material in addition to a carbon-based reducing material of coke and pulverized coal are used. The reduced powdering properties of sintered ore in the blast furnace in two cases of “CO + H ₂ reduction” (H ₂ concentration: 6.1 vol%) were evaluated and compared.
First, for the blast furnace with a furnace volume of 5153 m ³ and a tapping capacity of 10500 t / day, a “list model” is set as a general thermal mass balance model for evaluating mass transfer in the blast furnace shaft section. As the blast furnace operating conditions, the items shown in Table 1 (the amount of tapping, the type and amount of tuyere blown material, the element composition, the sintered ore / coke ratio) are input, and the blast furnace is charged into the blast furnace as output. Under the balance of balance that the amount of material and the amount of discharged material are equal, the blast furnace operation specifications shown in Table 2 (furnace top gas components (N ₂ , CO, CO ₂ , H ₂ , H ₂ O), air flow rate) , Ventilation temperature, ventilation moisture, oxygen enrichment amount, output amount and output component, ore intensity, coke ratio, reducing material ratio, ventilation intensity, oxygen intensity, slag ratio, solution loss reaction amount, exhaust gas Amount) was calculated. Note that the elemental composition of the blowing agent listed in Table 1, is that the average composition together pulverized coal and COG the modification treatment with a gas having an increased concentration of H ₂ (modified COG).

Next, as shown in FIG. 2, a mesh is cut into the blast furnace and divided, and a partial balance model for calculating the mass balance and the heat balance is set for each mesh, and the blast furnace shown in Table 1 above is set in this model. The operating conditions and the blast furnace operation specifications shown in Table 2 above were input, and the temperature distribution, gas composition distribution, and charging furnace descent rate in the blast furnace were calculated as outputs. As a reference example, FIG. 4 shows a comparison of the temperature distribution in the blast furnace in the case of CO reduction and the case of CO + H ₂ reduction. As a result of this analysis, the blast furnace top temperature was 237 ° C. in all cases.

  Next, according to the procedure of (C) described above, from the previously calculated temperature distribution and gas composition distribution in the blast furnace and the descending speed in the charging furnace, the reduction condition when the sintered ore descends in the blast furnace. Estimating the change over time, that is, the change of the reducing gas composition and the reduction temperature with respect to the elapsed time after the charging of the sintered ore, simulating the time-dependent change of the estimated reduction conditions, reducing conditions in the reduction test of the sintered ore, That is, the reducing gas composition and the reducing temperature that change with the reducing time were set.

FIG. 5 shows the relationship between the reduction time and the reduction temperature in the reduction test set as described above in the case of CO reduction and the case of CO + H ₂ reduction. From FIG. 5, by changing the reducing material to be blown, the heating rate of the sintered ore charged in the blast furnace is changed, and CO + H ₂ reduction (3.6 ° C./min) from CO reduction (5.0 ° C./min). ) Shows that the temperature rises at a lower speed. The reason for this is considered that the reduction reaction of sintered ore with hydrogen is an endothermic reaction.

Table 3 shows the reduction gas composition in the reduction test set as described above, comparing the case of CO reduction with the case of CO + H ₂ reduction. However, although the relationship between the reduction time and the gas composition obtained by the above calculation changes continuously, in Table 3, the reduction temperatures are room temperature to 237 ° C., 237 to 649 ° C., and 649 to 958 to simplify the reduction test. The composition of the reducing gas was changed in three stages of ° C. Here, the temperature of 237 ° C. in Table 3 is the blast furnace top temperature obtained by this calculation, and below this temperature corresponds to before the blast furnace charging, the supply gas in the reduction test is 100 vol% nitrogen, The reducing gas was supplied at 237 ° C. or higher.

Next, based on the reduction test conditions in two cases of CO reduction and CO + H ₂ reduction set as described above, a sintered ore prepared according to JIS M8720 was used as a sample, and the blast furnace shaft portion shown in FIG. A reduction test was conducted using a simulation test apparatus. At this time, the sample (sintered ore) used in the reduction test increased the load applied with the reduction time as shown in the load pattern shown in FIG. I let you.
And in the above reduction test, in order to investigate the change of the reduced powdering properties depending on the reduction temperature, after raising the temperature from the blast furnace top temperature to the upper limit temperature set every 100 ° C. in the temperature range of 500 to 900 ° C., reduction, It cooled and measured the reduction | restoration powdering rate and reduction rate in each upper limit temperature. In addition, the said reduction | restoration powdering rate evaluated the sintered ore after the said reduction | restoration by performing the tumbler test by the method prescribed | regulated to JISM8712 "Iron ore-rotational strength test method". Moreover, the reduction rate was measured according to JIS M8713 “Iron Ore—Reducibility Test Method” for the sintered ore after the reduction.

FIG. 7 shows the relationship between the reduction temperature and the reduction rate in the above test results by comparing CO reduction with CO + H ₂ reduction. From this figure, CO + H ₂ reduction using a hydrogen-based reducing material in addition to a carbon-based reducing material of coke and pulverized coal compared to CO reduction using only a carbon-based reducing material of coke and pulverized coal as a reducing material. It can be seen that the reduction rate increases in a temperature region of 600 ° C. or higher. Such a difference due to the reducing material has not been detected in a conventional test performed at about 550 ° C.

Further, FIG. 8 shows the relationship between the reduction temperature and the reduced powdering rate in the above test results by comparing CO reduction with CO + H ₂ reduction. From this figure, CO + H ₂ reduction using a hydrogen-based reducing material in addition to a carbon-based reducing material of coke and pulverized coal compared to CO reduction using only a carbon-based reducing material of coke and pulverized coal as a reducing material. The reduction powdering rate at a reduction temperature of 500 ° C. or higher is high, and the difference due to the reducing material is clearly shown as in FIG.
Note that in FIG. 8, described in Patent Document 1 as a reference, was also shown reduction degradation rate when the reduction test at a temperature of 550 ° C. using a reducing gas and H ₂ gas containing 6.2Vol% However, in the evaluation method of the present invention, reduced powder properties of the sintered ore that could not be grasped by the evaluation method of Patent Document 1 are obtained.

  As described above, by using the method for evaluating reduced powdering properties of the present invention, it is possible not only to accurately evaluate and grasp the reduced powdering properties in a wide temperature range of sintered ore charged into a blast furnace, but also as a reducing material. Changes in the reduced powdering properties of sintered ore when changing the blast furnace operating conditions such as adding a hydrogen-based reducing material to a carbon-based reducing material can also be accurately evaluated and grasped.

Furthermore, by applying the method for evaluating reduced powdering properties of the present invention to actual operation of a blast furnace, for example, when performing blast furnace operation under conditions such that the reduced powdering rate of sintered ore is high, However, when using high-strength sintered ore, or when using sintered ore with a high reduction powdering property, the blast furnace operating conditions are changed to reduce the reduction powdering rate of the sintered ore accordingly. Therefore, it becomes possible to foresee or prevent a blast furnace operation trouble in advance.
The effect peculiar to the present invention can be obtained for the first time by conducting a reduction test by simulating the change over time of the reduction conditions in the blast furnace obtained by utilizing a blast furnace operation simulation.

1: Load 2: Core tube 3: Heater 4: Sinter (sample)
5: Graphite crucible 6: Reducing gas 7: Exhaust gas after reduction treatment 8: Gas analyzer 9: Sintered ore after reduction 10: Tumbler tester

Claims (3)

In evaluating the reduced powdering properties of sinter used in blast furnace operation, we estimated the time-dependent change of the reduction condition when the sinter descends in the blast furnace, and simulated the time-dependent change of the estimated reduction condition. A method for evaluating a reduced powdering property of a sintered ore, comprising performing a reduction test of the sintered ore and measuring and evaluating a reduced powdering rate of the sintered ore after reduction. By the following treatments (A) to (C), the reduction test conditions of the sintered ore were simulated to simulate the change over time of the reduction conditions when the ore descends in the blast furnace. The method for evaluating reduced powdering properties of sintered ore according to claim 1, wherein the reduction test is performed.
(A) A general heat mass balance model for analyzing the blast furnace operation from both the material balance and the heat balance is set, and the blast furnace operation conditions are calculated by inputting the blast furnace operation conditions into the general heat mass balance model.
(B) The inside of the blast furnace is divided into meshes, partial balance models for calculating the mass balance and heat balance are set for each mesh, and the blast furnace operating conditions calculated in (A) above are calculated for the partial balance model. Input the operation specifications and calculate the temperature distribution and gas composition distribution inside the blast furnace and the descending speed in the charging furnace.
(C) Based on the temperature distribution and gas composition distribution inside the blast furnace calculated in (B) above, and the descending speed in the charging furnace, the time-dependent change in the reduction condition of the sintered ore descending in the blast furnace is estimated, and the estimated firing Simulating the time-dependent change of the reduction condition of the ore, the reduction gas composition and the reduction temperature are set with respect to the reduction time in the reduction test of the sintered ore.
(D) Under the conditions set in (C) above, the sintered ore reduction test is performed to a temperature of 900 ° C. or lower while the temperature is raised from the blast furnace top temperature. 3. The method for evaluating reduced powder properties of sintered ore according to claim 1, wherein the reduction test of the sintered ore is performed while applying a load to the sintered ore.

Images