阅读说明：本技术 转炉吹炼方法 (Converter blowing method ) 是由 贞本峻秀 福山博之 仁井谷洋 于 2019-05-27 设计创作，主要内容包括：转炉吹炼方法为,从顶吹喷枪的喷嘴向转炉内的铁水面吹送氧气,该转炉吹炼方法具有：速度计算工序,求出在吹炼中产生的废气中的粉尘量而计算所述转炉中的粉尘产生速度；偏差量计算工序,求出预先求出的使所述铁水面与所述顶吹喷枪的前端的距离即喷枪间隙为最佳的间隔时的所述顶吹喷枪的使用次数与所述粉尘产生速度的关系R1所对应的、在所述速度计算工序中计算出的所述粉尘产生速度的偏差量；以及位置调整工序,根据预先求出的所述喷枪间隙的变化量与所述粉尘产生速度的变化量的关系R2,为了校正在所述偏差量计算工序中求出的所述偏差量,在所述吹炼中调整所述喷枪间隙。(A converter blowing method for blowing oxygen into a molten iron surface in a converter from a nozzle of a top-blowing lance, the converter blowing method comprising: a speed calculation step of calculating a dust generation speed in the converter by obtaining an amount of dust in an exhaust gas generated during blowing; a deviation amount calculation step of calculating a deviation amount of the dust generation speed calculated in the speed calculation step, the deviation amount corresponding to a relationship R1 between the number of times of use of the top-blowing lance and the dust generation speed when a lance gap, which is a distance between the molten iron surface and a tip end of the top-blowing lance, is an optimum distance, which is calculated in advance; and a position adjustment step of adjusting the lance gap during the blowing so as to correct the deviation amount calculated in the deviation amount calculation step, based on a relationship R2 between a variation in the lance gap and a variation in the dust generation speed, which is obtained in advance.)

1. A converter blowing method for blowing oxygen gas from a nozzle of a top-blowing lance to a molten iron surface in a converter, the converter blowing method comprising:

a speed calculation step of calculating a dust generation speed in the converter by obtaining an amount of dust in an exhaust gas generated during blowing;

a deviation amount calculation step of calculating a deviation amount of the dust generation speed calculated in the speed calculation step, which corresponds to a relationship R1 obtained in advance, where the relationship R1 is a relationship between the number of times the top-blowing lance is used and the dust generation speed when a lance gap, which is a distance between the molten iron surface and the tip end of the top-blowing lance, is an optimum interval; and

and a position adjustment step of adjusting the lance gap during the blowing so as to correct the deviation amount calculated in the deviation amount calculation step, based on a relationship R2 between a variation in the lance gap and a variation in the dust generation speed, which is obtained in advance.

2. The converter blowing method according to claim 1,

in the correction of the deviation amount, a gradient obtained by dividing a variation amount of the dust generation speed by a variation amount of the lance gap is used.

3. The converter blowing method according to claim 1 or 2,

in the speed calculation step, the dust concentration in the collected dust water is calculated from the difference between the density of the collected dust water measured by the densitometer and the density of the pure water predicted from the temperature of the collected dust water measured by the thermometer, and the amount of the dust is obtained by continuously collecting the collected dust water obtained by wet-collecting the exhaust gas, passing the collected dust water through the densitometer and the thermometer.

Technical Field

The present disclosure relates to a converter blowing method using a top-blowing lance.

Background

In the converter, the blowing is performed using a top-blowing lance (hereinafter, appropriately referred to as "lance"). In this blowing, oxygen is injected from a nozzle hole provided in the lance toward the molten iron surface (liquid surface) to stir the molten iron and remove Si, Mn, P, and C by the oxidation reaction. During blowing, dust is generated from the converter due to the oxygen gas injected from the nozzle hole of the lance bouncing on the molten iron surface and the decarburization reaction. The generated dust is discharged together with the exhaust gas. This dust mainly contains iron components (iron and iron oxide), and it is not desirable that the iron components are lost and reduced during discharge.

When the top-blowing lance is used for converting, the shape of the molten iron surface in the converter changes when the oxygen collides with the molten iron surface due to the oxygen feeding speed and the lance height (the nozzle tip position).

It is known that the more the distance between the molten iron surface and the tip of the nozzle, that is, the more the lance gap is reduced at a constant oxygen feed rate, the more the shape of the molten iron at the time of oxygen collision with the molten iron surface becomes a puddle (reversed Ω -shaped cross section), and the more easily the generated dust is captured into the molten iron without scattering, so that the amount of dust generated can be reduced. This is called hard blowing.

On the other hand, it is known that if the lance gap is too small, the nozzle is strongly affected by heat from the molten iron surface, and therefore the nozzle is severely worn, and the life of the lance is shortened. In this way, the life of the lance is shortened, and the replacement frequency of the lance is increased, which adversely affects the operation.

From the above, it is desirable that the lance gap is an optimum gap for reducing the amount of dust generated while maintaining the life of the lance, and blowing is performed according to the gap. The optimum interval of the lance gap (hereinafter, appropriately referred to as "optimum lance gap") is set in accordance with the size and oxygen feed rate of the converter.

In order to set the lance gap to an optimum interval, it is necessary to know the height of the molten iron surface, and as a method therefor, for example, there is a technique disclosed in japanese patent application laid-open No. 11-52049. Specifically, the following method is used: after charging molten iron and scrap or a can alloy (alloy iron charged into a can or the like) into the converter, microwaves are transmitted into the converter through a mobile microwave transmitting/receiving antenna provided in a sub-lance hole of an upper lid of the converter, and the height (liquid level grade) of the molten iron surface is measured from the received signals.

Disclosure of Invention

Problems to be solved by the invention

The height of the molten iron level is measured after charging molten iron or the like into the converter and during the period until the start of blowing (before the start of blowing). In japanese patent application laid-open No. 11-52049, although there is no explicit description about the time required for measuring the molten iron level, since the molten iron level immediately after charging swings, it is necessary to wait until the swing becomes small to grasp the accurate level, which affects productivity, and thus it is difficult to measure the molten iron level every time molten iron is charged into the converter or the like.

Therefore, an estimated value of the molten iron level height (estimated molten iron level height) for each blow when not measured is calculated using the following formula (1) based on the measured value of the molten iron level height measured by the microwave molten iron level gauge.

(deducing the height of the molten iron) { (WTN-WT { (WTn-WT)₀)/(ρπr₀ ²)}+l₀···(1)

Where ρ is the specific gravity of iron, r₀Is the section radius (inner diameter) of the converter in the vicinity of the molten iron level₀Is the measured value of the height of the molten iron surface by the microwave molten iron level gauge, WT₀The amount of iron charged into the converter at the time of the measurement of the molten iron level by the microwave, and the amount of iron charged into the converter at the time of the estimation of the molten iron level height WTN.

However, since the refractory attached to the inner surface of the converter is repeatedly worn and repaired, the cross-sectional radius of the converter changes every blowing. Therefore, every time blowing is repeatedly performed by measuring the molten iron level using the microwave molten iron level gauge, it is estimated that the molten iron level deviates from the actual molten iron level. Therefore, the lance gap cannot be set to an optimum interval.

The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a converter blowing method capable of performing blowing with an appropriate lance gap even when the height of the molten iron surface is not measured.

Means for solving the problems

The present inventors have intensively studied a method of setting an optimum lance gap among methods of blowing by charging a top-blowing lance into a converter, and as a result, found the following findings.

The lance gap can be estimated from the dust generation speed by utilizing the fact that the dust generation speed changes due to the variation of the lance gap.

However, when the number of times of use of the top-blowing lance is increased, the flow of the injected oxygen gas (oxygen injection) is changed due to the deformation of the lance (nozzle shape), and therefore the dust generation speed is changed even if the lance gap is constant. That is, it is difficult to estimate the lance gap only by the generation speed of the dust.

Therefore, the lance gap is adjusted based on the dust generation speed in consideration of the influence of the number of times of use of the lance.

The present disclosure has been completed based on the above findings, and the gist thereof is as follows.

A converter blowing method according to an aspect of the present disclosure is a converter blowing method of blowing oxygen gas from a nozzle of a top-blowing lance to a molten iron surface in a converter, the converter blowing method including: a speed calculation step of calculating a dust generation speed in the converter by obtaining an amount of dust in an exhaust gas generated during blowing; a deviation amount calculation step of calculating a deviation amount of the dust generation speed calculated in the speed calculation step, which corresponds to a relationship R1 obtained in advance, where the relationship R1 is a relationship between the number of times the top-blowing lance is used and the dust generation speed when a lance gap, which is a distance between the molten iron surface and the tip end of the top-blowing lance, is an optimum interval; and a position adjustment step of adjusting the lance gap during the blowing so as to correct the deviation amount calculated in the deviation amount calculation step, based on a relationship R2 between a variation in the lance gap and a variation in the dust generation speed, which is obtained in advance.

Effects of the invention

According to the present disclosure, it is possible to provide a converter blowing method capable of performing blowing with an appropriate lance gap even when the height of the molten iron surface is not measured.

Drawings

Fig. 1A is an explanatory view of a refining facility to which the converter blowing method according to the embodiment of the present disclosure is applied.

FIG. 1B is an explanatory view of a dust concentration measuring device of the refining facility shown in FIG. 1A.

FIG. 2A is a cross-sectional view of the top-blowing lance used in the refining apparatus shown in FIG. 1A, the cross-sectional view being taken along the tip side thereof.

FIG. 2B is a cross-sectional view showing the tip side of the top-blowing lance shown in FIG. 2A in a state where the nozzle is worn by use.

Fig. 3 is a graph showing a relationship between a change amount of the lance gap and a change amount of the dust generation speed in the converter for each number of times the top-blowing lance is used.

FIG. 4 is a graph showing the relationship between the number of times of use of the top-blowing lance and the dust generation speed in the converter when the lance gap is set to the optimum interval.

Detailed Description

Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings.

A converter blowing method according to an embodiment of the present disclosure is a blowing method used in the refining facility 9 shown in fig. 1A and 1B. First, the refining facility 9 of the present embodiment is explained, and then the converter blowing method of the present embodiment is explained.

As shown in fig. 1A and 1B, the refining facility 9 includes a converter 10, a top-blowing lance 11 (hereinafter, appropriately referred to as "lance"), and an exhaust gas treatment device 17.

As shown in fig. 2A, the lance 11 is a member for blowing oxygen gas from a nozzle 11A described later to the molten iron surface S in the converter 10. The lance 11 is formed in a tubular shape and is movable vertically upward and downward by an unshown elevating device. By moving the lance 11 up and down, the lower portion (tip side) of the lance 11 can be inserted into and removed from the converter 10. The lance 11 can be stopped at an arbitrary height position by the elevating device. The lance gap G described later can be adjusted by the vertical movement of the lance 11. In addition, an arrow UP in fig. 2A shows an upward direction in the vertical direction. In addition, an arrow AXL in fig. 2A shows a central axis of the lance 11.

The tip of the lance 11 is a nozzle portion, and a plurality of nozzles 11A are provided in the nozzle portion. These nozzles 11A are through holes having a narrowed middle portion, that is, Laval nozzles (De Laval nozzles), and are provided in plural numbers at regular intervals on a concentric circle centering on the center axis AXL of the lance 11. Further, the nozzle 11A may be formed on the central axis AXL of the spray gun 11.

As shown in fig. 2A, oxygen a supplied to the lance 11 is injected from the nozzle 11A. Here, the jet flow of the oxygen gas a jetted from the nozzle 11A toward the molten iron surface S is diffused by an angle of phi after forming a jet core, and collides with the molten iron in the converter 10 to form an ignition point (the ignition point is not shown in fig. 2A) dented like a waterfall pool on the molten iron surface S.

As shown in FIG. 1A, the exhaust gas treatment device 17 treats the exhaust gas (CO, CO) containing dust generated from the converter 10 in a wet manner₂、N₂Gas of which the main component is gas). The exhaust gas treatment device 17 includes a furnace lid 18, an exhaust gas duct 12, a primary dust collector 13, a secondary dust collector 19, and the like.

The furnace cover 18 and the flue gas duct 12 are provided above the converter 10. Further, a primary dust collector 13, a secondary dust collector 19, and a guide blower, not shown, are provided in this order on the downstream side of the exhaust gas duct 12. The exhaust gas of the converter 10 is sucked by the blower and is dedusted by the primary dust collector 13 and the secondary dust collector 19 through the furnace lid 18 and the exhaust gas duct 12. Further, the exhaust gas after dust removal is sent to a gas holder, not shown, as a valuable gas through a guide blower, while the exhaust gas with a high CO concentration is burned at the top through a chimney, not shown, and diffused into the atmosphere.

The primary dust collector 13 and the secondary dust collector 19 wet-collect the exhaust gas, and for example, a venturi scrubber may be used.

The dust collecting water introduced into the primary dust collector 13 (indicated by arrow W in fig. 1A and 1B) collects dust in the exhaust gas and becomes dust-containing dust collecting water. The collected water is temporarily stored in a lower water tank 14 provided immediately below the primary dust collector 13, and then sent to a not-shown collected water treatment apparatus to remove dust in the collected water.

As shown in fig. 1B, the exhaust gas treatment device 17 includes a dust concentration measurement device (hereinafter, appropriately referred to as "measurement device") 20 for measuring the dust concentration. The measuring apparatus 20 includes a pump 15 for continuously collecting the dust collection water having passed through the primary dust collector 13, and a vibrating densitometer 16 for measuring the density of the dust collection water. In the measuring apparatus 20, the dust collecting water is continuously collected by the pump 15, and the concentration of dust in the dust collecting water per unit time is continuously measured from the relationship with the water temperature at that time by using the vibrating densitometer 16 (the amount of dust in the exhaust gas generated during the blowing of the converter 10 is continuously measured). Here, most, at least 90% or more of the dust generated in the converter 10 is removed by the primary dust collector 13. Therefore, by measuring the dust concentration in the collected water collected by the primary dust collector 13, the dust concentration in the exhaust gas of the converter 10 can be estimated.

The dust concentration measured dust-collected water is returned to the lower water tank 14.

Next, a converter blowing method according to the present embodiment will be described.

As shown in fig. 1A and 1B, the converter blowing method of the present embodiment is a blowing method in which the distal end side of the lance 11 is inserted into the converter 10, and oxygen gas a is blown from the nozzle 11A of the lance 11 onto the molten iron surface S in the converter 10 to perform decarburization treatment. In addition, this converter blowing method is characterized in that, in the blowing, the lance gap G (see fig. 2A), which is the distance between the molten iron surface S and the tip of the lance 11, is set to an optimum distance. In addition, the blowing may be not only top blowing but also top blowing and bottom blowing in which bottom blowing is simultaneously employed.

Specifically, the converter blowing method includes:

a speed calculation step of calculating a dust generation speed GR by obtaining an amount of dust in the exhaust gas generated during the blowing;

a deviation amount calculation step of calculating a deviation amount of the dust generation speed GR calculated in the speed calculation step, corresponding to a relationship R1 between the number of times of use of the lance 11 and the dust generation speed GR at an optimum interval of the lance gap G, which is obtained in advance; and

and a position adjustment step of adjusting the lance gap G during the blowing in order to correct the deviation amount obtained in the deviation amount calculation step, based on a relationship R2 between the amount of change in the lance gap G and the amount of change in the dust generation speed GR, which is obtained in advance.

The speed calculation step, the deviation amount calculation step, and the position adjustment step are processed in a computer (arithmetic unit) of an operator who performs the converter operation. The relationship R1 used in the deviation amount calculating step and the relationship R2 used in the position adjusting step are, for example, made into a database. The computer also receives various information for performing the converter operation, and performs control of the converter operation (for example, start and stop of blowing, adjustment of the lance gap G), and the like (that is, the computer becomes a control unit).

The computer is a conventionally known computer including a RAM, a CPU, a ROM, an I/O, and a bus connecting these elements, but is not limited thereto.

First, the methods of calculating the dust generation speed, the relationship R1, and the relationship R2 will be described.

In the converter operation, as shown in fig. 1A, a lance 11 is inserted into the converter above a converter 10, and oxygen a is blown at a high speed onto molten iron to remove impurities of Si, C, P, and Mn (decarburization treatment is performed). At this time, the blown oxygen a rebounds on the molten iron surface S, and bubbles of CO gas on the molten iron surface S are broken along with the decarburization reaction, thereby generating fine dust.

The generated dust is sucked into the exhaust gas duct 12 through the furnace port cover 18 together with the exhaust gas generated from the converter 10, is contained in the collected water supplied from the primary dust collector 13, is sent to the collected water treatment apparatus through the lower water tank 14, and is separated and collected. Further, the dust generated from the converter 10 is separated from the exhaust gas by the dispersion of the dust collecting water by the primary dust collector 13, and the exhaust gas is sent downstream.

(method of calculating dust generation speed in converter 10)

As shown in fig. 1B, in the measuring apparatus 20, the dust collecting water is continuously collected by the pump 15, and the concentration of dust in the dust collecting water per unit time is continuously measured by the relationship with the water temperature at that time using the vibrating densitometer 16. The dust generation rate in the blowing of the converter 10 can be calculated from the product of the dust concentration and the amount of water scattered per unit time of the dust water (the amount of water scattered from the primary dust collector 13) measured by the above-described method.

(calculation method of relationship R2)

The relationship shown in fig. 3 can be obtained by measuring the molten iron level S in the converter 10 (for example, about 400 tons of molten iron in the converter) with a microwave molten iron level gauge (not shown) and estimating the relationship between the lance gap G and the average dust generation speed GR during the most decarburization period, which is the period when decarburization is initiated preferentially to oxygen supply, for each number of times of use of the lance 11. The number of times N of use of the lance 11 corresponds to the number of times of blowing in the converter 10 (the same applies hereinafter). In fig. 3, the case where the number of times of use of the spray gun is about 50 times (the case where the number of times of use is small: black circles in fig. 3) and the case where the number of times of use is about 200 times (the case where the number of times of use is large: white circles in fig. 3) are shown, but the same behavior is shown even in the range of 50 to 200 times.

As shown in fig. 3, the dust generation speed GR increases linearly with the increase in the lance gap G (here, in the range of 2500 to 3000 mm), and the inclination is constant regardless of the deformation of the nozzle 11A of the lance 11 with the increase in the number N of lance uses. The "inclination" described here is a gradient obtained by dividing the change amount of the dust generation speed GR by the change amount of the lance gap G (i.e., the relationship R2).

(calculation method of relationship R1)

The molten iron level S in the converter 10 was measured by a microwave molten iron level meter, and the dust generation speed GR in the most decarburization stage corresponding to the number of times N that the lances were used when the lance gap G was set to the optimum interval was set to the relationship shown in FIG. 4 (that is, the relationship R1).

As shown in fig. 4, when the lance gap G is set to the optimum value, the dust generation speed GR increases with an increase in the number of times of use N of the lance. In addition, when the dust generation speed is y and the number of times of using the spray gun is x, the curve shown in fig. 4 is 6.9492x^0.0698。

The dust generation speed GR of the converter 10 is calculated by the above method, and the speed calculation step, the deviation amount calculation step, and the position adjustment step are sequentially performed using the relationship R1 and the relationship R2 which are obtained in advance.

(speed calculation step)

First, the blowing of the converter 10 is performed by setting the lance height so as to obtain the optimum lance gap G based on the estimated molten iron level height obtained by the above equation (1), and the average amount of dust generation (amount of dust) in the exhaust gas generated during the most advanced decarburization period is obtained by using the above blowing method, and the dust generation speed GR of the converter 10 is calculated.

(deviation amount calculating step)

As shown in fig. 4, how much the dust generation speed GR of the converter 10 calculated in the speed calculation step deviates is determined from the relationship R1 between the number of times the top-blown lance 11 is used and the dust generation speed of the converter 10 at the optimum lance gap, which is determined in advance. Specifically, the difference (i.e., the amount of deviation) between the value of the dust generation speed GR determined from fig. 4 in accordance with the number N of gun uses and the value of the dust generation speed calculated in the speed calculation step is determined.

Here, when the calculated value of the dust generation speed GR is lower than the value of the dust generation speed GR corresponding to the number N of times of gun use shown in fig. 4, it means that the actual gun gap G is smaller (hard blowing) than the optimum gun gap G, and therefore, the gun gap G needs to be adjusted to be larger. On the other hand, when the calculated value of the dust generation speed GR is higher than the value of the dust generation speed GR corresponding to the number N of times of gun use shown in fig. 4, it means that the actual gun gap G is larger (soft blowing) than the optimum gun gap G, and therefore, the gun gap G needs to be adjusted to be small.

(position adjustment step)

The lance gap G is adjusted during blowing in order to correct the deviation amount obtained in the deviation amount calculation step, based on the relationship R2 between the amount of change in the lance gap G and the amount of change in the dust generation speed GR, which is obtained in advance as shown in fig. 3. In the present embodiment, the dust generation rate GR is determined and the lance gap G is adjusted during the most advanced decarburization period during blowing.

As described above, the gradient of the change amount of the dust generation speed GR divided by the change amount of the lance gap G, which indicates the relationship R2 between the change amount of the lance gap G and the change amount of the dust generation speed GR, is substantially constant regardless of the number N of lance uses. From the relationship between the two, the adjustment amount of the lance gap G for correcting the deviation amount of the dust generation speed GR is obtained, and the lance gap G is adjusted during the blowing of the converter 10.

Specifically, the deviation amount of the dust generation speed GR stored in the deviation amount calculation step is divided by the gradient to obtain an adjustment amount of the lance gap G corresponding to the deviation amount of the dust generation speed GR, and the height position of the lance 11 is changed by the adjustment amount to adjust the lance gap G.

The adjustment of the lance gap G (i.e., the speed calculation step, the deviation amount calculation step, and the position adjustment step) may be performed once for one blow, but may be performed a plurality of times as needed.

Here, as shown in fig. 2B, when the number of times of use N of the lance 11 increases, the outlet portion of the nozzle 11A tends to wear and the outlet diameter tends to increase. When the outlet diameter of the nozzle 11A is enlarged, energy loss occurs at the nozzle outlet, and the jet core length becomes short, so that the flow potential of the oxygen gas a is reduced. However, in the converter blowing method of the present embodiment, since the lance gap G is adjusted based on the dust generation speed GR in consideration of the influence of the number of times N of use of the lance 11, even when the molten iron level is actually measured without using the microwave molten iron level gauge, the blowing of the converter 10 can be performed with an appropriate lance gap G. This can suppress and prevent the dust amount from becoming excessive due to excessive soft blowing (the lance gap G becomes large) and the life of the lance 11 from being significantly reduced due to excessive hard blowing (the lance gap G becomes small).