JP2014040627A - Refining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To be able to satisfactorily perform dust collection while efficiently performing refining treatment.SOLUTION: At first, a relation between an oxygen supplying rate at a refining treatment time and a dust amount inflowing to a building 2 is obtained; at second, an oxygen supplying rate X1 in which dust generating in refining treatment does not inflow to the building 2 is obtained; at third, when refining treatment is performed by an oxygen supplying rate X2 larger than the oxygen supplying rate X1, a relation of a refining processing time of the refining treatment and a dust concentration in the building 2 is obtained; at fourth, a decreasing time in which a dust concentration decreases to a dust concentration corresponding to a first management division defined by operation environmental control is obtained based on relation between a refining processing time when refining treatment is performed by the oxygen supplying rate X2, then refining treatment is performed by an oxygen supplying rate of at most the oxygen supplying rate X1, and a dust concentration in the building 2. In addition, at fifth, when refining treatment is performed, refining treatment is performed by the oxygen supplying rate X2 larger than the oxygen supplying rate X1, and an oxygen supplying rate is lowered to the maximum of the oxygen supplying rate X1 before at least the decreasing time from a refining finishing time.

Description

  The present invention relates to a refining method for collecting dust generated in a refining process using local dust collection just above a facility for performing the refining process and performing a refining process while collecting a building dust different from the local dust collection. .

Conventionally, it is known that dust is generated when refining treatment is performed. When a large amount of dust is generated, the working environment is deteriorated. Therefore, dust generated during the refining process is collected by a dust collector that collects dust. There exist some which are shown to patent documents 1-3 as a technique which collects dust with a dust collector.
In Patent Document 1, a weighing value of an auxiliary material to be introduced into the converter from the auxiliary material hopper is introduced, and an arithmetic unit for calculating an oxygen blowing flow value corresponding to an exhaust gas flow rate generated by the introduction of the relevant auxiliary material is provided, Introduce pressure measurement value or exhaust gas flow rate measurement value on the exhaust gas dust collector outlet side, compare this with the set value, calculate the oxygen blowing flow value corresponding to the deviation value, and calculate from the arithmetic unit and dust content adjustment device Each oxygen blowing flow rate value and a predetermined base oxygen blowing flow rate setting value are introduced, and an oxygen blowing flow rate setting device for outputting a setting value for an oxygen flow rate controller is provided.

In Patent Document 2, the amount of dust in the exhaust gas generated from the converter is measured, the transition of the amount of dust generation between the heats is obtained based on the measured amount of dust, and the heat immediately before the heat, or two or more immediately before the heat When the amount of dust generation in the heat of the vehicle deviates from the set threshold value, the operating condition of the heat is changed so that the amount of dust generation falls within the threshold value.
In Patent Document 3, the dust content in the exhaust gas is obtained from the pressure generated by the induced blower at the rotational speed of the induced blower, and the dust content is compared with a preset environmental reference value. When it is smaller, the determined rotational speed is set as the rotational speed of the induction fan, and when the dust content is larger than the environmental reference value, the rotational speed is recalculated to satisfy the environmental reference value.

Japanese Examined Patent Publication No. 54-022169 Japanese Patent Laid-Open No. 2002-060824 Japanese Patent No. 30804526

In Patent Document 1, although oxygen blowing is performed in consideration of the amount of dust generated when refining in a converter or the like, in this technique, the acid feed rate during the refining process is limited by the amount of dust, and the refining is performed. At present, it is very difficult to perform a sufficient refining process while shortening the processing time.
Patent Documents 2 and 3 also relate to the amount of dust. However, as in Patent Document 1, it is very difficult to sufficiently perform the refining process while shortening the refining process time.

  Therefore, in view of the above problems, an object of the present invention is to provide a refining method capable of sufficiently collecting dust while performing a refining process efficiently.

In order to achieve the above object, the present invention has taken the following measures.
That is, the technical means for solving the problem in the present invention is to collect dust generated by the refining process using local dust collection just above the facility for performing the refining process, and a building different from the local dust collection. A method of performing a refining process while collecting dust, characterized by performing the following step (5) during a refining process after performing the preliminary preparation shown in the following (1) to (4) before the refining process. To do.
(1) The relationship between the acid feed rate during the refining process and the amount of dust flowing into the building is obtained.
(2) The maximum acid feed rate X1 at which dust generated in the refining process does not flow into the building is obtained.
(3) When the refining treatment is performed at a larger acid sending rate X2 than the maximum acid sending rate X1, the relationship between the refining time of the refining treatment and the dust concentration in the building is determined in the step (1). Determined using acid velocity and dust.
(4) Based on the relationship between the refining treatment time and the dust concentration in the building when the refining treatment is performed at the acid sending rate below the maximum acid sending rate X1 after refining treatment at the acid sending rate X2. A reduction time during which the dust concentration decreases to the dust concentration corresponding to the first management category determined by the work environment management is obtained.
(5) The refining process is performed at an acid sending rate X2 larger than the maximum acid sending rate X1, and the acid sending rate is set to the maximum acid sending rate from the end of the refining before the decrease time obtained in step (4). Reduce to speed X1.

  According to the present invention, it is possible to sufficiently collect dust while performing the refining process efficiently.

It is the figure which showed each process of the refining method of this invention. It is the figure which showed the hot metal pretreatment, the building, the equipment which performs local dust collection, and the equipment which performs building dust collection. It is the figure which showed the opening hole which lets an immersion lance etc. pass. It is a figure which shows the relationship between an acid delivery speed | rate and the dust amount which flows in into a building. It is the perspective view which showed the inside of the building typically. Oxygen-flow-rate is the 94.0Nm ³ / min and building precipitator is a graph showing the relationship between refining processing time and dust concentration when a 3000 m ³ / min. Oxygen-flow-rate is the 94.0Nm ³ / min and building precipitator is a graph showing the relationship between refining processing time and dust concentration when a 2000 m ³ / min. Oxygen-flow-rate is the 94.0Nm ³ / min and building precipitator is a graph showing the relationship between refining processing time and dust concentration when a 6000 m ³ / min. It is a relationship figure of the refining processing time and dust concentration when building dust collection is 3000 m < ³ > / min. It is a related figure of refining processing time and dust concentration when building dust collection is 2000m < ³ > / min. It is a related figure of the refining process time and dust concentration when building dust collection is 6000 m < ³ > / min. FIG. 2 is a relationship diagram between the Si concentration of hot metal and the basic unit of the refining agent 1. It is a figure which shows the measurement position of the dust density | concentration in a building.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In a steelmaking factory, refining treatment such as desiliconization treatment, dephosphorization treatment, and decarburization treatment is generally performed on hot metal discharged from a blast furnace. In the refining process, a refining agent, oxygen, or the like is supplied to the hot metal to refine the hot metal. During the refining process, dust such as exhaust gas is generated. The generated dust is subjected to local dust collection (to perform local dust collection) with a dust collector provided immediately above a refining facility that performs refining treatment. Although it is ideal to collect dust generated during the refining process by this local dust collection, for example, there is a case where not all dust can be collected due to the dust collection capability of a dust collector, a bag filter or the like. Dust that cannot be collected by local dust collection spreads in the building and may reach a work space (work place) where workers work. When there is a lot of dust in the building, workers may wear dust masks and dust glasses (goggles) depending on the situation. In addition, in order to improve the work space, a dust collector is provided in the building separately from the local dust collection, and building dust collection is performed in which dust in the building is collected by the dust collector in the building. Thus, by implementing the building dust collection, the dust in the building can be reduced, and the environment of the worker's work place can be improved.

In the present invention, when performing the refining process while carrying out both the local dust collection and the building dust collection, the conditions of the refining process are appropriately changed in order to improve the working environment of the worker. is there. The refining process may be any process as long as oxygen is supplied, and the container for performing the refining process may be any one such as a kneading car, a hot metal ladle, and a converter.
In the refining process, gaseous oxygen or solid oxygen is supplied to the molten iron for refining. The refining reaction varies depending on the oxygen delivery rate when gaseous oxygen or solid oxygen is supplied to the hot metal, and the degree of this refining reaction affects the degree of dust generation. In other words, there is a relationship between the acid feed rate during the refining process and the amount of dust generated, and in order to improve the working environment in the building, the acid feed rate during the refining process must be appropriate.

Hereinafter, the relationship between the acid delivery rate and the dust generated during the refining process will be described.
In the refining process, when the acid feed rate (the supply amount of oxygen) is large, the refining reaction becomes faster, the amount of dust generated increases, and the exhaust gas temperature also increases. In such a case, the dust generated during the refining process cannot be collected by local dust collection, and the dust spreads in the building. Here, in a situation where the amount of dust spread in the building is small, the building dust collection is also performed, so the dust in the building does not increase. On the other hand, when there is a lot of dust spreading in the building (when there is a lot of dust that could not be collected by local dust collection), the dust in the building will increase.

Thus, in the refining process, the acid delivery rate affects the amount of dust generated. If the acid delivery rate is large, the amount of dust spreading in the building may also increase. Therefore, in the present invention, as shown in FIG. 1, before performing the refining process, first, the relationship between the acid feed rate during the refining process and the amount of dust flowing into the building (the amount of dust spreading in the building) is obtained. (Processing (1)).
The acid sending speed during the refining process and the amount of inflow dust flowing into the building may vary depending on the refining conditions (equipment conditions) and the operation method in the refining process. Therefore, in the process (1), the acid feed rate measured in the actual operation and the amount of dust flowing into the building at the acid feed rate at that time are obtained from the result of the actual operation.

  As described above, in the refining process, both solid oxygen and gaseous oxygen may be used as the oxygen source. Here, even if the value of the acid delivery rate obtained from solid oxygen and gaseous oxygen is the same, if the ratio of gaseous oxygen to solid oxygen (gasic acid ratio) is different, the amount of dust flowing into the building may increase or decrease. is there. For example, in the dephosphorization process, when the gas-acid ratio is large, the secondary combustion amount may increase and the temperature of the exhaust gas may rise. When the exhaust gas temperature rises, cooling air may be supplied in the vicinity of a dust collector that performs local dust collection in order to suppress an increase in the exhaust gas temperature. Due to this influence, the amount of dust collected by local dust collection decreases, and the amount of dust flowing into the building increases. That is, since the gas-acid ratio may increase even at the same acid feed rate, it is preferable to adopt the most dust amount flowing into the building as the dust amount in the process (1) even at the same acid feed rate. .

  Now, looking at the tendency between the acid feed rate and the amount of dust in the refining process in more detail, the amount of dust generated gradually increases as the acid feed rate increases. When the acid delivery rate is high, dust cannot be collected by local dust collection and the dust flows into the building. However, when the acid delivery rate is low, the dust does not flow into the building. That is, there is a boundary between an acid delivery rate that realizes a situation in which dust does not flow into the building and an acid delivery rate that produces a situation in which dust flows into the building, and there is a boundary between them. Here, if we focus only on the fact that dust does not flow into the building, it is sufficient to always perform the treatment with a very low acid feed rate in the refining process, but the refining process becomes very long and productivity etc. It cannot be implemented with a decline. For this reason, when performing the refining treatment, the boundary value between the acid feed rate at which dust flows into the building and the acid feed rate at which dust does not flow into the building, that is, the maximum acid feed rate at which dust does not flow into the building. It is necessary to grasp the speed (non-inflow acid sending speed) X1.

  If the uninflowed acid feed rate X1 is known, for example, in the first half of the refining process, the refining process is advanced at an acid feed rate X2 larger than the non-inflow acid feed rate X1, while in the second half of the refining process, the uninflow acid feed rate X1 It is possible to reduce the amount of dust in the building at the point of time when the treatment is carried out at a lower acid feed rate and finally the refining treatment is completed. In other words, a non-inflow acid feed rate X1 that is a boundary value between an acid feed rate at which dust flows into the building and an acid feed rate at which dust does not flow into the building is calculated, By controlling the acid speed, it is possible to perform a process excellent in the efficiency of the refining process and the environmental performance in the building.

Therefore, in the present invention, in the process (2), an acid feed rate (non-inflow acid feed rate) X1 at which dust generated in the refining process does not flow into the building is obtained. Even in this process, when there are a plurality of non-inflowing acid feed rates X1 at which the dust does not flow into the building due to the gas-acid ratio even at the same acid feed rate, the smallest acid feed rate among them is set as the non-inflow acid feed rate X1. Is preferred. In addition, since the acid feed rate (non-inflow acid feed rate) X1 which can collect dust only by local dust collection changes with installation conditions, an operation method, etc., it is preferable to set using the acid feed rate in an actual operation. In addition, since the exhaust gas (dust) generated in the refining process is observable smoke such as brownish brown, it can be easily determined by visual inspection whether dust is flowing into the building. The acid rate X1 may be obtained. In actually measuring the acid delivery rate, it is preferable to record and obtain the gas-acid flow rate (acid delivery rate) using a data logger or the like.

  Next, in the step (3), when the refining treatment is performed at the acid sending rate X2 larger than the non-inflow acid sending rate X1, the refining treatment time when the refining treatment is performed at the acid sending rate X2 and the inside of the building Find the relationship with dust concentration. As described above, since the relationship between the acid delivery rate and the amount of dust is known in advance in step (1), the relationship is determined using a simulation from the relationship between the acid delivery rate and the amount of dust. The dust concentration in the building can be calculated using the size of the building, that is, the internal volume (volume) of the building and the amount of dust in the building.

As described above, when the refining process is performed at the acid feed rate X2 by obtaining the relationship between the refining process time and the dust concentration in the building when the refining process is performed at the acid feed rate X2 by the step (3). It is possible to grasp how much the dust concentration in the building has increased for each refining time.
Now, when refining treatment is performed at an acid feed rate X2 larger than the uninflowed acid feed rate X1, the amount of dust in the building, that is, the dust concentration increases, but in step (3), refining is performed at the acid feed rate X2. Since the relationship between the refining time and the dust concentration in the building is known, the dust concentration in the building at the time when the refining at the acid feed rate X2 is completed can be grasped. Here, a case is considered in which refining treatment is performed at an acid feed rate equal to or lower than the non-inflow acid feed rate X1 from the time when refining at the acid feed rate X2 is completed. Since the acid feed rate is the non-inflow acid feed rate X1, the dust generated by this refining process is collected only by local dust collection, while the dust that has already entered the building by the refining process is collected in the building. The dust in the building can be gradually lowered according to the refining time. Since the dust concentration before reducing the acid feed rate in step (3) is known, the refining process is finally completed if the decreasing dust concentration is known by continuing the refining treatment at the non-inflow acid sending rate X1. It becomes possible to control the dust concentration at the time.

  For this reason, in the step (4) of the present invention, after performing the refining treatment at the acid feed rate X2, the building in the case of performing the refining treatment at the acid feed rate not higher than the non-inflow acid feed rate X1. Based on the relationship between the dust concentration and the refining time, a reduction time during which the dust concentration falls to the dust concentration corresponding to the first management category (details will be described later) determined by the work environment management is obtained. In this step (4), the dust in the building when the acid feeding rate is switched to the non-inflowing acid feeding rate X1 from the state where the dust concentration in the building has already increased by the refining treatment of the acid feeding rate X2 The degree of decrease in density is obtained using simulation. That is, the reduction time for the dust concentration in the building to fall to the dust concentration corresponding to the first management category determined in the work environment management after the refining process after switching to the non-inflow acid transmission rate X1 is obtained.

The dust concentration corresponding to the first management category defined in work environment management refers to the control concentration used as a reference when evaluating the state of work environment management from the measurement results of airborne hazardous substances based on Article 65 of the Industrial Safety and Health Act. It is a thing. The first management of the dust concentration is obtained from the work environment measurement standard by the equation E = 3.0 ÷ (1.19Q + 1). E is the concentration (unit: mg / m ³⁾ that is used as a standard for evaluating the state of work environment management from the measurement results of hazardous substances in the air based on Article 65 of the Industrial Safety and Health Law. Q is the release of dust The silicic acid content (unit:%) The first control category can be obtained by collecting the dust in the building and measuring the free silicic acid content of the dust. Is a mineral (SiO ₂ ) in a state in which silicon is three-dimensionally bonded to oxygen and not bonded to other elements with a name distinguished from bonded silicic acid constituting a silicate compound.

The simulation method may be implemented by any method. For example, it is important that the calculated value of the dust concentration of the building when the dephosphorization process is finished and the actual value are substantially equal. When the volume of the building is small, the efficiency of dust ventilation in the building varies depending on the air volume of the building dust collection. Therefore, when several types of building dust collection airflows are used in actual operation, the relationship between the refining treatment time and the building dust concentration Z may be obtained for each building dust collection airflow.

As described above, in the present invention, as shown in the steps (1) to (4), preparations are made in advance before performing the refining treatment, the acid feed rate during the refining treatment, and the amount of dust flowing into the building. Find the relationship between the dust concentration in the building and the drop time.
When actually performing the refining process, as shown in the step (5), first, the refining process is first performed at the acid feeding rate X2 larger than the non-inflowing acid feeding rate X1, and from the time when the refining process is finished. Before the decrease time obtained in step (4), the acid feed rate is reduced to the non-inflow acid feed rate X1 or less, and the dust concentration in the building at the end of refining is less than the dust concentration corresponding to the first management category To do.

  Specifically, in the refining process, the target component value of the hot metal, the amount of refining agent and the amount of gaseous oxygen required to reach the target temperature set during the refining process (target temperature of the hot metal) are obtained in advance. The amount of the refining agent and the amount of gaseous oxygen may be determined in any way as long as the target component value and the target temperature are determined. By determining the scheduled use amount of the refining agent and the expected use amount of gaseous oxygen in advance, the blowing rate of the refining agent, the blowing rate of gaseous oxygen (acid feed rate), and the total refining time can be determined. In addition, it is important to determine in advance the amount of the refining agent and the amount of gaseous oxygen necessary for the refining treatment in order to control the target component and the target temperature of the hot metal in the refining treatment.

  When the acid feed rate X2 in the actual operation is determined, the dust concentration of the building when the operation is performed is determined by the step (3) and the step (4). Also, the refining time (decrease time) until the dust concentration in the building during the refining process is less than the dust concentration corresponding to the first management category, that is, the acid supply rate during the refining process is less than the non-inflow acid supply rate X1 The time to perform the refining process is reduced. For this reason, the acid feed rate is always set to the non-inflow acid feed rate X1 before the decrease time as seen from the time when the refining process is finished.

As described above, the present invention can be summarized as follows: (5) is performed during the refining process after the preliminary preparations shown in (1) to (4) are performed before the refining process.
(1) The relationship between the acid feed rate during the refining process and the amount of dust flowing into the building is obtained.
(2) The acid feed rate X1 at which the dust generated in the refining process does not flow into the building is obtained.
(3) When the refining process is performed at an acid supply rate X2 larger than the acid supply rate X1, the refining process is performed using the relationship between the refining process time of the refining process and the dust concentration in the building.
(4) Dust concentration based on the relationship between the refining time and the dust concentration in the building when refining treatment is performed at an acid feed rate of 1 or less after refining treatment at acid feed rate X2. Finds the decrease time to decrease to the dust concentration corresponding to the first management category defined in the work environment management.
(5) The refining treatment is performed at an acid feed rate X2 larger than the acid feed rate X1, and the acid feed rate is set to the maximum acid feed rate X1 before the decrease time obtained in step (4) from the end of refining. To lower.

The above-described present invention will be described in detail. FIG. 2 shows a hot metal pretreatment for performing a refining process, a building, a facility for performing local dust collection, and a facility for performing building dust collection.
As shown in FIG. 2, the hot metal pretreatment facility 1 is provided on the lower side of the building 2 and includes an immersion lance 5 for blowing a refining agent into the hot metal 4 in the kneading vehicle 3 and an oxygen lance 6 for blowing oxygen. Yes. A dust collection hood 8 that performs local collection of dust (exhaust gas) generated during the refining process is provided on the top of the furnace port 7 of the kneading vehicle 3. A splash cover 10 is attached in the vicinity of the dust collection port 9 of the dust collection hood 8 and between the dust collection port 9 and the furnace port 7 of the kneading vehicle 3. By providing the splash cover 10, the exhaust gas can be efficiently collected locally.

The dust collection hood 8 is provided with a discharge passage 11 through which dust (exhaust gas) passes. A gas cooling facility 12 for cooling the dust (exhaust gas) is provided in the discharge passage 11 and dust collected is collected. A bag filter 13 for complementing is provided. The bag filter 13 is composed of a glass fiber bag filter 13 and has a maximum heat-resistant temperature of 260 ° C. When the temperature of the collected exhaust gas reaches 240 ° C. or higher, the cooling air introduction damper provided in the discharge path 11 between the gas cooling facility 12 and the bag filter 13 is opened, thereby cooling air. The exhaust gas is introduced into the discharge path 11 so that the exhaust gas temperature at the dust collection port 9 is less than 260 ° C.

Further, the immersion lance 5 and the oxygen lance 6 extend through the dust collection hood 8 and the discharge path 11 in the vertical direction in the building 2 positioned at the upper part of the hot metal pretreatment facility 1. On the ceiling (upper part) of the building 2, a building dust collector 15 that performs the building 2 in the building 2 is provided. The building dust collector 15 is configured by combining, for example, three dust collectors. By combining the three dust collectors, building dust collection can be performed with a capacity of 2000, 3000, and 6000 m ³ / min.

In the hot metal pretreatment facility 1 shown in FIG. 2, local dust collection and building dust collection were performed while performing dephosphorization as refining treatment. The implementation conditions of the refining process are as follows.
The amount of hot metal charged into the kneading vehicle 3 was 260 to 310 tons. The hot metal components before treatment were [Si] = 0.05 to 0.35 mass%, [P] = 0.103 to 0.133 mass%, and [Mn] = 0.15 to 0.45 mass%. . [P] after the dephosphorization treatment was set to 0.015 to 0.036% by mass. Three refining agents were used in the dephosphorization process. The components of the refining agent are as shown in Table 1.

Although three types of refining agents are used, any number of types may be used as long as they contain CaO or CaO and O.
As the gaseous oxygen, one having 100% O ₂ was used, and the supply rate of the refining agent was 100 to 600 kg / min for the refining agent 1 to the refining agent 3 respectively, and the gaseous oxygen was 10 to 80 Nm ³ . As shown in FIG. 3, the opening hole (the size of the floor hole of the building 2) 16 through which the immersion lance 5 and the oxygen lance 6 are passed has a horizontal width of 0.96 m and a vertical width of 0.79 m.

  First, in the step (1), an actual operation was used to determine the relationship between the acid feed rate during the dephosphorization treatment and the amount of dust flowing into the building 2. First, as shown in Table 2, the dephosphorization process was performed 3 times (tests 1 to 3).

In tests 1 to 3, 10 minutes after the start of the dephosphorization process, the blowing speed of the refining agent 1 was 150 kg / min, the blowing speed of the refining agent 2 was 100 kg / min, and the flow rate of gaseous oxygen was It was decided to switch to 65 Nm ³ / min. These in dephosphorization process, the blowing rate of the solid oxygen 21,7kg / min, since the flow rate of gaseous oxygen was 65 nm ³ / min, when obtaining the oxygen-flow-rate, oxygen-flow-rate becomes 86.7Nm ³ / min .

  Here, in order to obtain the amount of dust flowing into the building 2 through the opening hole 16, it passes through the opening hole 16 when it is dephosphorized three times (from the opening hole 16 into the building 2). Measure the exhaust gas dust concentration. Specifically, as shown in FIG. 3, when the opening hole 16 was viewed in plan, the dust concentration in the exhaust gas, the wind speed of the exhaust gas, and the temperature of the exhaust gas were measured at three locations, point A, point B, and point C. Table 3 shows the dust concentration in the exhaust gas at each point, the wind speed of the exhaust gas, and the exhaust gas.

The measured values shown in Table 3 are average values for 10 minutes during the dephosphorization treatment under the above conditions. Moreover, the position of each point when the opening hole 16 is viewed from the side is as shown in FIG.
In Test 1, the dust concentration in the exhaust gas was 16069 mg / Nm ³ , the wind speed of the exhaust gas was 3.33 m / sec, and the temperature of the exhaust gas was 348 ° C. The area of the opening hole 16 is 0.758 m ² because it is 0.96 m wide and 0.79 m long. Since the diameter of the immersion lance 5 is 370 mm, the diameter of the oxygen lance 6 is 200 mm, the area of the immersion lance 5 is 0.107m ^2, the area of the oxygen lance 6 becomes 0.031 ^2. Therefore, the substantial area of the opening hole 16 (area of the portion through which the exhaust gas passes) is 0.62 m ² . For convenience of explanation, the substantial area of the opening hole 16 is simply referred to as the area of the opening hole 16. The flow rate of the exhaust gas flowing in from the opening hole 16 is an area of the opening hole 16 of 0.62 m ² × wind speed of the exhaust gas 3.33 m / sec = 2.06 m ³ / sec. Since the temperature of the exhaust gas is 348 ° C., when the volume of the exhaust gas is converted to Nm ³ , 2.06 m ³ /sec×273÷(273+348)=0.91 Nm ³ / sec. Since the dust concentration in the exhaust gas is 16069 mg / Nm ³ , the speed of the dust flowing into the building 2 (work floor) from the opening 16 is 16069 mg / Nm ³ × 0.91 Nm ³ / sec = 145666 mg / sec. Become.

Similar to Test 1 described above, the dust speed (dust amount) in Test 2 and Test 3 was 13835 mg / sec in Test 2 and 13677 mg / sec in Test 3.
From the above, when the results of tests 1 to 3 are averaged, the amount of dust flowing into the building 2 when the dephosphorization process is performed at an acid feed rate of 86.7 Nm ³ / min is 14026 mg / sec.

The dust concentration (mg / Nm ³ ) in the exhaust gas is measured by a weight concentration measurement method (JIS Z 8808) by filtration repair, and the wind speed of the exhaust gas is measured continuously by a digital manometer using a Pitot tube (JIS Z 8808). I went there. The exhaust gas temperature was continuously measured by a thermocouple.
Furthermore, in order to determine the amount of dust flowing into the building 2 at another acid delivery rate, as shown in Table 4, dephosphorization treatment was performed under the conditions shown in Tests 4-6.

In tests 4 to 6, 10 minutes after the start of the dephosphorization process, the blowing speed of the refining agent 1 was 150 kg / min, the blowing speed of the refining agent 2 was 120 kg / min, and the flow rate of gaseous oxygen was It was decided to switch to 70 Nm ³ / min. In these dephosphorization treatments, the solid oxygen blowing rate was 23.8 kg / min and the flow rate of gaseous oxygen was 70 Nm ³ / min. Therefore, when the acid feeding rate was determined, the acid feeding rate was 93.8 Nm ³ / min. . In tests 4-6, as shown in Table 5, the amount of dust flowing into building 2 is 20254 mg / se in test 4.
c, and it was 19898 mg / sec in Test 5 and 19447 mg / sec in Test 6. Therefore, the amount of dust flowing into the building 2 when the acid feed rate was 93.8 Nm ³ / min was 19866 mg / sec.

In tests 1 to 6 described above, the test was performed at a gas oxygen ratio of 75%, which is the maximum gas oxygen ratio conceivable in normal dephosphorization treatment. That is, the gas oxygen ratio with the largest amount of dust flowing into the building 2 (the amount of dust generated) is selected, and the operation results are calculated. The acid feed rate during the refining process in the step (1) and the amount of dust flowing into the building 2 Used to find the relationship.
Next, as shown in Table 6, the operations of Tests 7 to 12 were performed in order to obtain the non-inflow acid transmission rate X1 at which the dust generated in the refining process does not flow into the building 2.

In tests 7 to 10, the dephosphorization process was performed for 10 minutes while the dephosphorization process was performed for 10 minutes while the flow rate of the refining agent 1 was 210 kg / min and the flow rate of gaseous oxygen was 50 Nm ³ / min. It was.
In Test 7, the actual value of the acid delivery rate during the dephosphorization treatment for 10 minutes is 204 to 213 Nm ³ / min, the supply rate of solid oxygen is 14.9 to 15.5 Nm ³ / min, and the acid delivery rate is It became 64.9-65.5Nm < ³ > / min. When dephosphorization treatment was performed at an acid feed rate of 64.9 to 65.5 Nm ³ / min, no inflow of dust from the opening 16 into the building 2 was confirmed.

In Test 8, the actual value of the acid feed rate during the 10-minute dephosphorization process was 206 to 213 Nm ³ / min, the solid oxygen supply rate was 14.9 to 15.5 Nm ³ / min, and the acid feed rate was It became 64.9-65.5Nm < ³ > / min. In Test 9, the actual value of the acid feed rate during the dephosphorization treatment for 10 minutes was 205 to 214 Nm ³ / min, the solid oxygen supply rate was 15.0 to 15.6 Nm ³ / min, The speed was 65.0-65.6 Nm ³ / min. In Test 8 and Test 9, no inflow of dust into the building 2 was observed.

The determination of the inflow of dust into the building 2 is continued for 5 seconds or more during the dephosphorization process, and when dust enters the building 2 from the opening hole 16, the inflow of dust is continued for 5 seconds or more. Thus, it is preferable that the dust does not flow when the dust does not enter the building 2 from the opening hole 16. Ideally, there should be no dust in the building 2 when no dust flows into the building 2. However, in the actual operation, when dephosphorization is performed, the CO gas generated in the kneading vehicle 3 is reduced. There are times when dust temporarily flows into the building when it comes out of the slag momentarily. For example, if the basicity of the slag is low and the viscosity of the dephosphorization slag is low at the initial stage of dephosphorization, the degassing of the CO gas is bad and the CO gas is discharged at once. At this time, an instantaneous dust inflow of about 2 seconds is confirmed, but the instantaneous dust inflow does not increase the dust concentration in the building 2 abruptly, and the impact on the environment in the building 2 is Since there are few, it is preferable to exclude the instantaneous inflow of dust to the building 2. In Tests 7 to 9 described above, in order to facilitate the removal of CO gas from the dephosphorization slag, the basicity of the dephosphorization slag at the start of the dephosphorization process is increased to about 2.0, and there is no sudden outgassing. As a result of the refining process, there was no instantaneous inflow of dust into the building 2 as described above.

In test 10, the actual value of the acid feed rate during the dephosphorization treatment for 10 minutes was 213 to 224 Nm ³ / min, the supply rate of solid oxygen was 15.5 to 16.4 Nm ³ / min, and the acid feed rate was It became 66.5-67.4 Nm < ³ > / min. In Test 11, the actual value of the acid feed rate during the 10-minute dephosphorization process was 216 to 225 Nm ³ / min, the solid oxygen supply rate was 15.8 to 16.4 Nm ³ / min, The speed was 66.8-67.4 Nm ³ / min. In Test 12, the actual value of the acid delivery rate during the dephosphorization treatment for 10 minutes is 214 to 223 Nm ³ / min, the supply rate of solid oxygen is 15.6 to 16.3 Nm ³ / min, and the acid delivery rate is It became 66.6-67.3Nm < ³ > / min. In tests 10 to 12, the inflow of dust from the opening 16 into the building 2 was confirmed continuously for 5 seconds or more.

As described above, according to the operation results of Tests 7 to 12, when the acid feed rate is 65.5 Nm ³ / min or less, there is no inflow of dust into the building 2, and the building speed exceeds 65.5 Nm ³ / min. As a result, there was inflow of dust into 2.
When the relationship between the acid delivery rate and the dust inflow rate is organized, when the acid delivery rate is 65.0 Nm ³ / min, the dust inflow rate (dust amount) flowing into the building 2 is 0 mg / sec, and the acid delivery rate is In the case of 86.7 Nm ³ / min, the dust inflow rate (dust amount) is 14026 mg / sec, and in the case of the acid feed rate of 86.7 Nm ³ / min, the dust inflow rate (dust amount) is 19866 mg / sec. . Further organizing, the relationship between the acid delivery rate in the step (1) and the amount of dust flowing into the building 2 becomes the curve A (secondary curve) shown in FIG. 4, and the non-inflow acid delivery rate X1 in the step (2) is It is 65.0 Nm ³ / min shown in FIG. In addition, in the operation results of Tests 7 to 12, the acid feed rate without inflow of dust into the building 2 is 65.5 Nm ³ / min, but in this example, considering the variation in the acid feed rate, The non-inflow acid feeding rate X1 is set to 65.0 Nm ³ / min.

  In the step (3), it is assumed that the refining treatment is performed at an acid feed rate X2 larger than the non-inflow acid feed rate X1, and the relationship between the refining treatment time at this time and the dust concentration in the building 2 is used. The simulation was used for obtaining. In the simulation, the dust concentration in the building 2 was determined using the dust inflow amount of the building 2 flowing in every second and the outflow amount flowing out of the building 2. The amount of outflow flowing out of the building 2 is determined by the dust collection capacity of the building and the dust concentration of the gas (exhaust gas) when the building collects dust. The dust concentration of the exhaust gas when collecting the building dust is as shown below. The amount of spillage was determined after the same concentration as the dust concentration in Building 2.

The acid feed rate X2 larger than the non-inflow acid feed rate X1 was 94.0 Nm ³ / min. The dust inflow rate (dust amount) when the acid feed rate X2 was 94.0 Nm ³ / min was obtained from the curve equation of FIG. 4 and was 20044 mg / sec. In determining the volume of the building 2, the actual size of the building 2 was used. As shown in FIG. 5, the width of the work floor in the building 2 is 15.25 m, the vertical width is 13.70 m, and the height is 20.0 m. Therefore, the volume of the building 2 is 4179 m ³ . As shown in FIG. 5, in the building 2, in addition to the immersion lance 5, the oxygen lance 6, and the lance carriage, various facilities such as a lance replacement deck and a lance inspection deck are provided. Since it is small compared with other space volumes, the size of the periphery of the building 2 was directly used as the volume of the building 2 without removing various facilities.

If there is no obstacle, the dust flowing into the building 2 from the opening hole 16 proceeds to the building dust collector 15 and is captured by the building dust collector 15, but in actuality, it hits various facilities installed in the building 2. Therefore, the dust flowing into the building 2 from the opening hole 16 is assumed to diffuse uniformly into the building 2 instantaneously, and the dust concentration in the building 2 is calculated. Moreover, since the average particle size of the dust which flowed into the building 2 from the opening hole 16 was as very fine as 4 to 8 μm, the calculation was performed without considering sedimentation due to gravity.

Now, the oxygen-flow-rate X2 as 94.0Nm ³ / min, if the dust 20044mg / sec flows into building 2, dust concentration of the building in 2 will ^{20044mg ÷ 4179m 3 = 4.8mg / m} 3 . On the other hand, since dust in the building 2 is collected by the building dust collection, when the air volume of the building dust collector 15 is 3000 m ³ / min, the discharge capacity per second is 3000 m / 60 and 50 m ³ / sec. , 50 m ³ /sec×4.8 mg = 240 mg of dust is removed by building dust collection. Thereby, the amount of dust in the building 2 after 1 second becomes 20044 mg−240 mg = 19844 mg. The dust concentration in the building within 2 becomes ^{19804mg / 4179m 3 = 4.74mg / m} 3.
When the acid feed rate is 94.0 Nm ³ / min based on the above-described concept, the dust concentration in the building 2 gradually increases according to the refining treatment time as shown in FIG. Becomes 396 mg / m ³ at the time when becomes 571 seconds. This is because the amount of dust flowing into the building 2 from the opening 16 is balanced with the amount of dust discharged by the building dust collection (outflow amount).

Similarly, when the acid feed rate is 94 Nm ³ / min and the building dust collection capacity is 2000 m ³ / min, the discharge capacity per second is 33 m ³ / sec at 2000/60, which is 33 m ^3. /Sec×4.8 mg = 160 mg of dust is removed by building dust collection. Thereby, the dust concentration in the building 2 becomes (20044/160) / = 4.76 mg / m ³ . When the acid feed rate is 94 Nm ³ / min and the building dust collection capacity is 2000 m ³ / min, as shown in FIG. 7, when the refining time becomes 858 seconds, the constant is 597 mg / m ³ . Become.

Similarly, when the acid feed rate is 94 Nm ³ / min and the building dust collection capacity is 6000 m ³ / min, as shown in FIG. 8, when the refining time is 284 seconds, 196 mg / m ³ It becomes constant.
As described above, when the refining process is performed by the step (3) at the acid sending speed X2 larger than the acid sending speed X1, the relationship between the refining time of the refining process and the dust concentration in the building 2 is determined. When a certain time elapses during processing, the dust concentration in the building 2 becomes a certain value. That is, the dust concentration in the building 2 becomes constant in 858 seconds even when the building dust collection capacity (air volume) is 2000 m ³ / min, which is the smallest.

Now, in the step (4), after dephosphorization treatment at an acid feed rate X2, refining treatment time (dephosphorization treatment time) when dephosphorization treatment is carried out at an acid feed rate lower than the acid feed rate X1. And the relationship between the dust concentration in the building 2 is obtained. Next, a reduction time during which the dust concentration is reduced to the dust concentration corresponding to the first management category determined by the work environment management is obtained.
When the acid delivery rate is set to the non-inflow acid delivery rate X1 or less, as shown in the step (3), no new dust flows into the building 2 even if the dust concentration in the building 2 is increased. Therefore, the dust concentration in the building 2 gradually decreases as the refining time in which the non-inflow acid transmission rate is set to the non-inflow acid transmission rate X1 or less proceeds.

At the stage where refining treatment was performed with an acid feed rate of 94 Nm ³ / min and a building dust collection capacity of 3000 m ³ / min, the total amount of dust in the building 2 was 396 mg / m ³ × 4179 m ³ = 1654884 mg. . From this state, if the acid feed rate is set to the non-inflow acid feed rate X1 or less (for example, 65 Nm ³ / min or less), the dust collection capacity is 3000 m ³ / min, so the amount of dust discharged per second Is 19800 mg [(3000 m ÷ 60) × 396]. Amount of dust building in 2 one second after the 1654884mg-19800mg = 1635084mg next, dust concentration of the building in 2 becomes ^{1635084mg ÷ 4179m 3 = 391.3mg / m} 3. Similarly, when the calculation is repeated, the dust concentration in the building 2 decreases as shown in FIG. As shown in FIG. 9, when refining treatment is performed at an acid feed rate of X1 or less after refining treatment at an acid feed rate of X2, the acid feed rate is set to X1 or less and 463 seconds from the time point. If it passes, the dust concentration in the building 2 can be made less than 1.51 mg / m ^3, which is the dust concentration corresponding to the first management category defined in the work environment management. This 463 seconds is the decrease time shown in step (4).

It should be noted that when building dust collection is performed, an equivalent amount of air discharged by building dust collection is required, but in step (4), air with a dust concentration of 0 / m ³ is passed through the opening 16. Calculation is performed as flowing into the building 2.
As shown in FIG. 10, similarly, when the dephosphorization process is performed at a building dust collection capacity of 2000 m ³ / min and an acid feed rate before the decrease of the acid feed rate is 94 Nm ³ / min, If the acid velocity is set to X1 or less and 748 seconds have elapsed from the time point, the dust concentration in the building 2 can be made less than the dust concentration corresponding to the first management category.

In addition, as shown in FIG. 11, when dephosphorization treatment was performed at a building dust collection capacity of 6000 m ³ / min and an acid feed rate before the reduction of the acid feed rate was 94 Nm ³ / min, If the speed is set to X1 or less and 200 seconds have elapsed from the time point, the dust concentration in the building 2 can be made less than the dust concentration corresponding to the first management category.
As described above, as shown in FIG. 4, in step (1), the relationship between the acid feed rate in the dephosphorization process and the amount of dust flowing into the building 2 is obtained, and in step (2), the dephosphorization process occurs. A non-inflow acid sending speed X1 at which dust does not flow into the building 2 is determined. And as shown in FIGS. 6-8, in a process (3), the dephosphorization process in the case of performing a dephosphorization process with the acid sending speed | rate X2 larger than the non-inflow acid sending speed | rate X1, and the dust concentration in the building 2 Seeking relationship with. As shown in FIGS. 9 to 11, in the step (4), after performing the refining treatment at the acid feed rate X2, the refining treatment time in the case of performing the dephosphorization treatment at the acid feed rate equal to or lower than the acid feed rate X1 Based on the relationship with the dust concentration in the building 2, the reduction time during which the dust concentration decreases to the dust concentration corresponding to the first management category determined by the work environment management is obtained.

In actual operation, the following processing is performed.
The amount of refining agent and the amount of gaseous oxygen are set so that the [P] concentration after dephosphorization treatment, the temperature after dephosphorization treatment, and the dephosphorization slag basicity become target values based on actual operation data. Specifically, the relationship between the dephosphorization rate, the basic unit of gaseous oxygen, the basic unit of solid oxygen, the Si concentration before the treatment, and the hot metal temperature after the dephosphorization treatment is expressed by Equation (1). Is used to determine the basic unit of gaseous oxygen.

  For example, when Pi = 0.117 mass% and Paim = 0.020 mass%, equation (1) becomes equation (2).

  The basic unit of solid oxygen is represented by formula (3).

  In this embodiment, the refining agent (the refining agent in the dephosphorization process) includes three types of refining agent 1, refining agent 2, and refining agent 3. When three types of refining agents are used, the target temperature of hot metal after dephosphorization, the temperature of hot metal before dephosphorization, the basic unit of refining agent 1, the basic unit of refining agent 2, the basic unit of refining agent 3, The relationship between the basic unit, the Si concentration before the treatment, and the Mn concentration before the treatment is expressed by Equation (4).

  First, the basic unit of the refining agent 1 used in the dephosphorization process is obtained by the formula (5). In order to obtain the basic unit of the refining agent 1, the Si concentration before processing is used as shown in FIG. Here, the basicity during the dephosphorization treatment was 1.8.

  At the time of dephosphorization, as shown in Japanese Patent Application Laid-Open No. 2012-122134, when the basicity of slag becomes 2.5 or more, the melting point of dephosphorization slag rises, and the slag to the chaotic vehicle 3 is increased. Adhesion increases. Therefore, when determining the basic unit of the refining agent 1, the slag at the time of setting the basic unit of the refining agent 1 is taken into consideration that the basicity of the slag is increased by the refining agent 2 or the refining agent 3 to be set later. The basicity is 1.8. For example, when the Si concentration before treatment is 0.21% by mass, it is 88.95 × 0.21 + 0.15 = 18.8 kg / t according to the equation (5).

The solid oxygen in the refining agent 2 uses collected dust or the like. Considering the balance between the dust used for the refining agent 2 and other materials, the basic unit of the refining agent 2 was 25 kg / t.
As described above, when the refining agent 1 and the refining agent 2 are obtained, the basic unit of the refining agent 3 is finally obtained. Here, since the basic unit to be used by the refining agent 1 and the refining agent 2 is determined, the basic unit of the refining agent 3 (the basic unit to be used) and the basic unit of gaseous oxygen are the above-described formulas (1) and (1). It can be obtained by solving simultaneous equations so as to satisfy (4). In the embodiment described above, the basic unit of the refining agent 3 is 15.1 kg / t, and the basic unit of gaseous oxygen is 5.34 Nm ³ / t. Here, assuming that the amount of hot metal at the time of dephosphorization is 291 tonnes, the supply amount (input amount) of each refining agent is as follows. The refining agent 1 is 18.8 kg / t × 291 ton = 5479 kg, the refining agent 2 is 25 kg / t × 291 ton = 7275 kg, and the refining agent 3 is 15.1 kg / ton × 291 ton = 7275 ton. Here, when the supply amount of each refining agent is rounded up to the nearest ten, refining agent 1 is 5500 kg, refining agent 2 is 7300 kg, and refining agent 3 is 4400 kg. Further, the amount of gaseous oxygen is 5.34 Nm ³ / t × 291 ton = 1553 Nm ³ , and is rounded up to the first place to 1560 Nm ³ .

Here, dephosphorization is performed at a building dust collection capacity of 3000 m ³ / min and an acid feed rate of approximately 94 Nm ³ / min. According to the results of the above-described processes (1) to (4), the acid feed rate of the refining process is set to 65 Nm ³ / min or less before 408 seconds or more.
Specifically, the acid delivery rate was determined in four stages in the dephosphorization process. First, from the first stage to the third stage, the acid feed rate was fixed at 94 Nm ³ / min for dephosphorization treatment, and in the final fourth stage, the acid feed rate was set to 65 Nm ³ / min.

As described above, the supply amount of the refining agents 1 to 3 and the basic unit of gaseous oxygen are obtained, but the supply amount of the refining agent and the basic unit of gaseous oxygen are as follows at each stage.
In the first stage, the blowing speed of the refining agent 1 was 300 kg / min, the blowing speed of the refining agent 2 was 250 kg / min, and the flow rate of gaseous oxygen was 45 Nm ³ / min.
Oxygen-flow-rate is a ^{300kg / min × 0.073Nm 3 /kg+250kg/min×0.107Nm 3} / kg + 45Nm 3 /min=97.3Nm 3 / min. However, the gaseous oxygen started to be sprayed after 5 minutes from the start of the treatment, and was blown in the first stage until the Si concentration of the hot metal 4 became 0.10%, as shown in JP 2012-122134 A.

In the first stage, the time when the gaseous acid oxygen is not blown is 4 minutes, and the lower limit time of blowing is a
Assuming minutes, the lower limit time of blowing can be obtained by equation (6).

  From the equation (6), the blowing time a is 2.1 minutes. In this example, blowing was performed at the above-mentioned acid feed rate for 6.1 minutes. The silicon removal oxygen efficiency in the first stage is expressed by equation (7). The silicon removal oxygen efficiency was determined by the process of Si Nojima removal, Hiroshi Ichikawa, Yuji Marukawa, Masaharu Anesaki, Hiromitsu Ueki, iron and steel, vol.15 (1983), 1738-1445. It can be obtained as shown in “Relationship between concentration and desiliconization oxygen efficiency”.

In the first stage, 1830 kg (300 kg / min × 6.1 min) of refining agent 1 was blown. Since the total supply amount of the refining agent 1 is 5500 kg as described above, the remaining 3670 kg is blown in after the second stage.
In the second stage, the blowing speed of the refining agent 1 was 200 kg / min, the blowing speed of the refining agent 2 was 130 kg / min, and the flow rate of gaseous oxygen was 65 Nm ³ / min.

Oxygen-flow rate was ^{200kg / min × 0.073Nm 3 /kg+130kg/min×0.107Nm 3} / kg + 45Nm 3 /min=93.5Nm 3 / min. The second stage blowing time was set to 3670 kg / 200 kg / min = 18.4 (min) using the remaining supply amount of the refining agent 1.
Now, as described above, the blowing of the refining agent 1 among the three types of refining agents is completed by the first stage and the second stage. In the third stage and the fourth stage, the refining agent 2 and the refining agent 3 are blown, but in the fourth stage, since the blowing is performed at a non-inflow acid feed rate X1 or less, the supply amount of the refining agent 2 and It is necessary to consider the balance between the supply amount of the refining agent 3 and the acid feed rate. In the third stage and the fourth stage, the supply amount of each refining agent, the acid feed rate, etc. are set as follows.

First, in the fourth stage, since the acid feed rate must be lowered, the supply amount of the refining agent in the fourth stage is set first. In the fourth stage, since the acid feed rate must be not more than the inflow acid feed rate X1, that is, 65 kg / min or less, the blowing rate of the refining agent 3 is set to 500 kg / min (acid feed rate = 500 kg / min). (Blowing speed of refining agent 3) × 0.130 kg / Nm ³ = 65 kg / min). Here, as described above, in order to set the dust concentration to be equal to or lower than the dust concentration corresponding to the first management category in a state where the acid feed rate is 65 kg / min, in the fourth stage, the decrease time is 463 seconds or more. It is necessary to make the acid feed rate 65 kg / min quickly. In this example, the time for the acid delivery rate to be 65 kg / min was set to 480 seconds, which was longer than 463 seconds.

  In the fourth stage, the blowing speed of the refining agent 3 is set to 500 kg / min and then blown for 480 seconds (8 minutes). Therefore, the remaining amount to be blown in the third stage is 4400 kg−500 kg / min × 8 min. = 400kg. The remaining amount of the refining agent 2 is 7300 kg−250 kg / min × (4 + 2.1) min−130 kg / min × 18.4 = 3390 kg.

The remaining amount of gaseous ^oxygen, a ^{1560Nm 3 -2.1min × 45Nm 3 /min-18.4min×65Nm 3} / min = 270Nm 3. The remaining total oxygen amount becomes ^{3390kg × 0.107Nm 3 /kg+400×0.130Nm 3 / kg} + 270Nm 3 = 687Nm 3. Dividing 687Nm ³ , which is the remaining amount of gaseous oxygen, by 94Nm ³ / min, which is the third stage acid feed rate, is 7.31 min, and this time is the third stage time. Finally, the blowing speed of the refining agent 2 is 3390 kg ÷ 7.31 min = 463.7 kg / min, and the blowing speed of the refining agent 3 is 400 kg ÷ 7.31 min = 54.7 kg / min.
The blowing speed of min and gaseous oxygen is 270 Nm ³ ÷ 7.31 min = 37.1 Nm ³ / min. When the refining agents 2 and 3 are blown down at the position of 1 and the gaseous oxygen is cut down at the position of 0.1, the blowing speed of the refining agent 2 is 460 kg / min, and the blowing speed of the refining agent 3 is 50 kg / min. The flow rate of gaseous oxygen is 37 Nm ³ / min. Actual oxygen-flow-rate in the third stage becomes ^{460kg / min × 0.107Nm 3 /kg+50kg/min×0.130Nm 3} / min + 37Nm 3 /min=92.7Nm 3 / min. Here, since the actual acid delivery rate in the third stage is 92.7 Nm ³ / min, in order to satisfy the total oxygen amount 687 Nm ³ in the third stage, 687 Nm ³ ÷ 92.7 Nm ³ / min = 7.41 min is the actual dephosphorization processing time in the third stage.

Thus, as a result of carrying out the dephosphorization process, the dust concentration in the building 2 after the dephosphorization process was able to be 1.0 mg / m ³ .
In the simulation, since the dust concentration was expected to be 1.2 mg / m ³ , the actual value is almost equal to the simulation. In addition, the dust density | concentration in the building 2 after completion | finish of a dephosphorization process was measured with the weight concentration measuring method by filtration collection as mentioned above. For the dust concentration, the dust concentration for 1 minute was measured from the end of the dephosphorization treatment, and the average value was used. In addition, when building dust collection was continued, since the inside of the building 2 was ventilated, the dust concentration was measured with the dust collection air volume of the building dust collection set to 0 m ³ / min simultaneously with the completion of the dephosphorization process. As shown in FIG. 13, the measurement of the dust concentration in the building was performed at three locations at a height of 1.5 m on the work floor of the building 2 in consideration of the position of the operator's face. Moreover, as shown in FIG. 13, the measurement of the dust concentration was performed at three locations in the order closer to the lance hole within the range in which the worker mainly works.

  Tables 7 and 8 summarize forms implemented in addition to the examples described above.

Table 7 shows the amount of hot metal in Experiment Nos. 1 to 7, the hot metal component, the hot metal temperature before treatment, the target after treatment [P], the target temperature after treatment, the basic unit of each refining agent to be used, the expected amount of use, This is a summary of non-inflow acid feeding speed X1, dust collection air volume of building dust collection, lower limit time, and the like. The amount of each refining agent used, the uninflowed acid feed rate, and the lower limit time were determined in the same manner as in the above-described Examples. As disclosed in Japanese Patent Application Laid-Open No. 2012-122134, the upper limit of the dephosphorization processing time was set to 50 minutes or less.

As shown in Table 8, in Experiments Nos. 1 to 4, the dephosphorization processing time is set to 50 minutes or less, and the dust concentration in the building is set to be equal to or lower than the dust concentration of the first management category determined by work environment management. did it.
On the other hand, in Experiment No5, although the dust concentration in the building could be made lower than or equal to the dust concentration of the first management category determined by the work environment management, the dephosphorization processing time took more than 50 minutes specified. In Experiment No. 6 and 7, although the dephosphorization time could be within the prescribed 50 minutes, the dust concentration in the building became larger than the dust concentration in the first management category determined by the work environment management. .

  In the embodiment disclosed herein, matters not explicitly disclosed, for example, operating conditions, various parameters, dimensions, weights, volumes, etc. of the components do not deviate from the range normally practiced by those skilled in the art. However, matters that can be easily assumed by those skilled in the art are employed.

DESCRIPTION OF SYMBOLS 1 Hot metal pretreatment equipment 2 Building 3 Chaos 4 Hot metal 5 Immersion lance 6 Oxygen lance 7 Furnace port 8 Dust collection hood 9 Dust collection port 10 Splash cover 11 Discharge path 12 Gas cooling facility 13 Bag filter 15 Building dust collector 16 Opening hole

Claims (1)

Dust generated by the refining process is a method of collecting the dust using a local dust collection just above the facility for performing the refining process, and performing the refining process while collecting the building dust different from the local dust collection,
A refining method characterized by performing the following step (5) at the time of refining treatment after the preliminary preparation shown in the following (1) to (4) before refining treatment.
(1) The relationship between the acid feed rate during the refining process and the amount of dust flowing into the building is obtained.
(2) The acid feed rate X1 at which the dust generated in the refining process does not flow into the building is obtained.
(3) When the refining process is performed at an acid supply rate X2 larger than the acid supply rate X1, the refining process is performed using the relationship between the refining process time of the refining process and the dust concentration in the building.
(4) Dust concentration based on the relationship between the refining time and the dust concentration in the building when refining treatment is performed at an acid feed rate of 1 or less after refining treatment at acid feed rate X2. Finds the decrease time to decrease to the dust concentration corresponding to the first management category defined in the work environment management.
(5) The refining treatment is performed at an acid feed rate X2 larger than the acid feed rate X1, and the acid feed rate is set to the maximum acid feed rate X1 before the decrease time obtained in step (4) from the end of refining. To lower.