KR101032503B1 - Method for Last Blow Working of Blast Furnace - Google Patents

Abstract

Blast Furnace in Steel Plants In particular, a blast furnace longitudinal wind operation method is provided that enables the maximum discharge of melt in the furnace for the repair and repair of large blast furnaces.

The blast furnace blast operation method, the step of charging the iron ore and lump coke to ensure breathability during blast furnace blast operation; and performing the detoxification while maintaining the constant pressure to the end point of the blast blast operation; and, the point of completion Charging the pressurized coke to the blast furnace in the; And increasing the top pressure while maintaining a constant air volume in the charged pressurized charge.

According to the present invention, in the state of preventing a safety accident such as blast furnace explosion, an improved effect of maximizing the discharge of the melt in the furnace, excluding the use of pressurized charges other than coke, such as silica used previously Can be obtained.

Blast furnace opening, repair, vertical wind operation, top pressure, air flow, pressurizing

Description

Method for Last Blow Working of Blast Furnace

The present invention relates to a blast furnace operation method for opening and repairing a blast furnace of a steel mill, in particular, a large blast furnace, and more specifically, by allowing the permissible pressure loss to satisfy the management standards through securing ventilation first, In order to prevent safety accidents such as blast furnace explosions, blast furnace blasts are allowed to discharge the melt in the furnace as much as possible by eliminating the use of pressurized charges other than coke, such as conventionally used silica. It relates to a method of operation.

In general, the blast furnace operation, as shown in Figure 1, charging the charge 110, that is, iron ore and coke in the furnace from the top of the blast furnace 100, hot air through the air vent 120 installed in the furnace bottom 120 Blowing to produce a molten iron by implementing a reduction, melting reaction in the furnace.

At this time, the iron ore and the coke charges (110) charged in the blast furnace 100 is a frictional action with the internal flue, or coke from the bottom of the furnace caused by the coke combustion and descent to the lower part according to the reduced melting of the iron ore at the lower part. Gas generated during the combustion of molten iron ore and reduction of iron ore rises to be discharged to the upper part of the blast furnace, and is damaged by the refractory smoke installed in the furnace body of the blast furnace 100 due to chemical erosion reactions generated at the contact with the furnace lead and the surface. Will receive.

On the other hand, the bottom portion 102 is largely divided into a bottom side portion 102a and a bottom portion 102b of the bottom, and a substantial amount of the melt 110 'is generated and discharged out of the furnace through the outlet 104 inside. Erosion of the lead occurs most quickly, and this erosion of the bottom part determines the life of the blast furnace.

Therefore, when the erosion of the bottom of the furnace continually progresses and the residual (warm range of the healthy duct) reaches 500 mm, the blast furnace is opened and repaired, and the longitudinal wind operation of the blast furnace is performed.

In other words, the blast furnace vertical wind operation is the final shelter operation step of terminating the blast furnace operation prior to the opening and repair of the blast furnace 100, and completely discharges the melt in the furnace to facilitate the dismantling and demolition work of the blast furnace, It means the air-venting operation to reduce the L1) of FIG.

The reason why such blast furnace vertical operation is important is to discharge the melt 110 ′, ie, molten iron and slag, accumulated on the bottom of the blast furnace when the blast furnace is closed, so that the blast furnace renovation period can be shortened.

On the other hand, the simple vertical wind operation method through the step reduction is the residual amount (melt) of the bottom part and the porosity of the coke 112 present in the bottom part is 23% level, and the outside of the melt of the furnace by lowering the porosity further. There has been a need for ways to increase emissions.

However, in Korean Patent Laid-Open Publication No. 2003-0097538, filed by the applicant of the present invention, a conventional blast furnace vertical wind operation method for further reducing the bottom melt 110 'is disclosed.

For example, in the related art disclosed in the above-described Patent Publication shown in FIG. 3, which is described in detail below, the furnace 100 is stepped up, and the exit port 104 is closed in steps. In the step before ending the discharge of the bottom melt 110 ', the air flow through the air vent 120 is checked and the top pressure is kept constant, and as shown in FIG. 2, the charge reduction level' L1 'is 23 m at the blast furnace. When the point was reached, the charging charge 140 for the vertical wind operation, that is, the coke 144 in addition to the additional silica 142 was charged to minimize the residual amount of the bottom melt.

However, in the related art disclosed in the above-described patent, the coke 142 and the silica 144 loaded for pressurization are discharged in a mixed state during the blast furnace dismantling operation, and thus, additional separation work for future reuse is required. In addition, the silica is melted in a high-temperature furnace atmosphere to coat the surface layer of the residual coke in the furnace (for example, pressurized coke (144 in FIG. 3) and core coke (112 in FIG. 1,2)).

Therefore, when a high temperature melt is coated on the charge charged for the vertical wind operation, the cooling time is delayed when the blast furnace is actually dismantled.

Furthermore, at the end of the decay, the lowering of the top pressure due to the decrease in the air volume caused a problem that could cause local gas flow changes such as melt discharge and channeling.

Accordingly, the applicant of the present invention eliminates the input of a separate charge other than coke in order to solve the problem caused by the pressurized charge, such as silicon that is conventionally put into the blast furnace for the pressure, and through the mixing of iron ore and lump coke in the blast furnace In order to ensure breathability, the present invention has been proposed to perform a stable blast furnace longitudinal operation while preparing for safety accidents such as blast furnace explosion.

The present invention has been proposed in order to solve the conventional problems as described above, the object of the aspect is to ensure the permissible pressure loss by satisfying the management standard through ensuring the breathability at the time of vertical wind operation, in the state of preventing safety accidents such as blast furnace explosion, It is to provide a blast furnace blast operation method that allows the discharge of the melt in the furnace as much as possible by eliminating the use of pressurized charges other than coke, such as silica, which has been used previously.

As a technical aspect for achieving the above object, the present invention comprises the steps of charging iron ore and lump coke to ensure breathability during blast furnace operation;

Performing deduction while maintaining the constant pressure up to the end of the vertical wind operation;

Charging the pressurized coke to the blast furnace at the time point of completion of the reduction; And,

Increasing the top pressure while maintaining the air volume in the charged pressurized charge;

It provides a blast furnace blast operation method configured to include.

Preferably, in the charging step of iron ore and lump coke, the mixture is charged with the mixed iron ore and lump coke, and then mixed charge the small iron ore and lump coke.

More preferably, the top pressure is maintained at 2,400 to 2,500 g / cm 2 until the end of the vertical wind operation, and the top pressure is 2,400 to 2,500 g / m while maintaining the air volume at 1900 to 2300 Nm 3 / min in the charged pressurization. The primary pressure is increased by 2 cm 2.

More preferably, after the first pressurization, the top pressure is increased to 2,400-2,500 g / cm2 while maintaining the air flow rate at 1400-1600 Nm3 / min to pressurize the secondary to raise the level of the bottom melt and discharge it. .

According to the present invention, when the vertical wind operation to ensure that the permissible pressure loss by satisfying the management standards through ensuring the breathability, in the state of preventing safety accidents such as blast furnace explosion, other than the coke, such as conventionally used coke Excluding the use of the charges, but by providing pressure through the air flow and the top pressure provides an excellent effect to enable the maximum discharge of the melt in the furnace.

Therefore, the present invention enables to discharge more of the melt in the bottom of the furnace during the blast furnace vertical operation to the outside of the furnace in a faster time, it is possible to reduce the burden on the bottom line operation after the blast, and to facilitate the internal cooling of the blast furnace after the bottom line It is also easy to dismantle the blast furnace.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

First, the blast furnace vertical wind operation is gradually reduced after the start of the reduction operation for the blast as shown in FIG. 2 (check the reduction level), and then confirm the air flow rate and the top pressure, and the reduction level is 23m from the blast furnace road (for example, When it reaches L1) of FIG. 2, the exit port 104 is closed in stages, and then the discharge of the bottom portion melt is terminated, and the ventilation operation is performed in stages.

On the other hand, blast furnace blast operation method of the present invention, the step of charging the iron ore (10) and lump coke (Nut Coke) (20) to ensure breathability during blast furnace blast operation as shown in FIG. Carrying out the charging step described above while maintaining the constant pressure to the end of the bell wind operation, and the decay reaches the point where the loading level is 23m (L1 in Fig. 2) at the blast furnace, and the blast furnace is completed at the end point. Charging only the pressurized coke (144 in FIG. 3), and increasing the top pressure (arrow 'F' in FIG. 4) while maintaining a constant air flow rate (see FIG. 4A) in the loaded pressurized coke. It may be implemented in one embodiment including the step of.

Therefore, in the vertical wind operation step of the present invention, unlike the conventional, to ensure the ventilation so that safety accidents such as blast furnace explosion is not managed to manage as shown in Figure 6 described below, and then the existing problem Instead of using silica (see 142 in FIG. 3), it is to properly operate the top pressure and the air flow.

At this time, looking at the breathability during the operation of the vertical wind, specifically, in the charging step of iron ore and lump coke, the mixed iron ore (10a in Fig. 3) and the lump coke (20 in Fig. 3) is charged to the blast furnace, and then granulated Iron ore (10b in FIG. 3) and the intermediate coke (20 in FIG. 3) are mixed and charged into the blast furnace.

For example, in the present embodiment, in order to improve the air permeability of the blast furnace during the vertical wind operation, about 5.5 tons of heavy coke (Nut Coke) after the iron iron ore 10a (75 ton / ch) layer after the iron ore layer (90 ton / ch) 25 mm or less in particle size), followed by mixing and charging 1.5 tons of intermediate coke 20 after the small iron ore 10b (25 tons / ch) layer.

In this case, when the intermediate ore coke is mixed with the iron ore layer, since the intermediate ore coke having a particle size of 25 mm or less exists in the ore layer, it is possible to secure ventilation at the initial softening fusion zone (T in FIG. 1) during the vertical wind operation, which ensures the air volume during the vertical wind operation. To make it possible.

For example, the vertical wind operation is an operation that actually emptyes the contents of the blast furnace. Therefore, when the blowing energy of the air volume is higher than the load of the contents, a so-called wind blow is generated and oxygen is supplied to the inside of the blast furnace. It can get into a dangerous safety accident.

That is, in FIG. 6, when the blast furnace vertical wind operation of the present invention is mixed with iron ore in order to ensure breathability, the lowering pressure loss, that is, the allowable pressure loss which is a correlation between the load of the internal charge and the blowing energy does not exceed the safety factor of the management standard. It is not shown.

Therefore, in the case of the present invention, even if the blowing energy due to the reduction of the charge level according to the reduction is higher than the load energy of the charge, air permeability is secured to prevent the generation of waste wind in which oxygen is supplied into the blast furnace.

At this time, the important thing is to compensate the load of the blast furnace charges, which are hidden in the vertical wind operation so as not to exceed the management standards as described below, so that the blast furnace opening pressure is 2,450 to 2,550 g / ㎠ so that the blowing energy does not exceed the load energy. Preferably, the blast furnace is to maintain a maximum top pressure of 2,500 g / cm 2.

If the above pressure is lower than 2,450 g / ㎠, the allowable pressure loss described above may exceed the management standards, and in the case of a large blast furnace operated by POSCO, the applicant of the present case, the maximum pressure is higher than 2,550 g / ㎠ It is difficult to maintain.

On the other hand, in the blast furnace vertical wind operation method of the present invention, as described above, in the step before closing the outlet 104 by gradual step-by-step and end the discharge of the bottom melt 110 ', When the top pressure is kept constant and the reduction level reaches 23 m, the pressurized coke (144 in FIG. 3) is charged (S2 in FIG. 3) to minimize the remaining amount of the melt of the bottom part, and then the top pressure and By carrying out the first and second pressurization through the air volume, it is possible to further discharge the remaining melt.

That is, when the decompression operation for the blast furnace is first started for the number of blast furnaces, the decompression operation is carried out to the point of 23m (L1 of FIG. 2), which is slightly higher than the level (26m) of the tuyere tip, and maximizes the pressurization effect. To this end, the peak pressure is maintained at a maximum of 2,500 g / cm2 up to the point of 21 m, the end of the vertical wind operation.

At this time, to the point where the charge level is 23m (L1 of FIG. 2), the reduction is performed according to the conventional reduction procedure. When the target charge level is 23m at the end of the wind blowing, the present invention does not use silica as in the prior art. Only the pressurized coke (144 in FIG. 3) is charged ('S2' in FIG. 3).

On the other hand, the step of mixing the iron ore and the intermediate coke described above, which is the step S1 in FIG. 3 is shown in the drawing, and the pressurized coke charging step S2 is shown below, but this is in contrast to the conventional press coke 144 It is necessary to understand that the actual operation stage consists of steps S1-> S2.

Such charged press coke prevents the formation of further melt and prevents the formation of additional melt due to the blowing energy of the amount of wind applied until the completion of the shelter, and provides a pressurizing effect of pressurizing and discharging the melt, in particular with a charging load. .

For example, the pressurized coke 144 remains in the furnace without being burned or melted to the vertical wind, and the furnace pressure (see 'F' in FIG. 4) and the pressurized coke (FIG. By the load of 4 of 144), the porosity of the bottom part melt is minimized from the existing 23% to 21% by pressurizing the inside of the furnace to maximize the discharge of the remaining amount of the melt to the outside of the furnace.

That is, among the melts remaining in the furnace after the bell blow, especially if the molten iron is large, the amount of melted water is increased and the dismantling work is difficult, so discharging the melt as much as possible is important during the bell blow operation. 144) is in its solid state, relatively easy to remove and reusable compared to other charges, and does not present any problems during post-demolition decommissioning operations.

Next, as shown in Figure 4, by using the air volume and the top pressure to the pressurized charge to increase the level of the melt (110 ') by minimizing the melt porosity of the bottom of the bottom portion, by adding the melt. By discharging out of the furnace, the remaining amount of melt is further minimized.

At this time, in the present invention, the amount of air retained in the pressurized charge during the first pressurization is 1900 to 2300 Nm 3 / min, preferably 2100 Nm 3 / min (for example, in FIG. L2) is P2 at the first pressurization, and the top pressure is 2,450 to 2,550 g / cm2 as described above. Preferably, the maximum top pressure is 2,500 g / cm2 (for example, P2 in FIG. 5). To increase.
Next, in the present invention, the air volume at the time of the second pressurization is maintained at 1300 to 1700 Nm3 / min, preferably at 1500 Nm3 / min (for example, P3 at the second pressurization in FIG. 5), and the top pressure is as described above. Similarly, 2,450-2,550 g / cm 2 Preferably, it is increased to 2,500 g / cm 2 (e.g., P3 in FIG. 5), which is the maximum blast pressure.

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Therefore, in the case of the present invention, when the charge level is completed up to 21m, the air volume and the top pressure are increased firstly, and then the air volume and the top pressure are secondly pressurized to discharge the melt in the furnace. To the maximum.

At this time, the first and second air flow conditions are to prevent the allowable pressure loss from exceeding the management standard due to excessive increase in the blowing energy as the air flow is maintained excessively than the allowable pressure loss described above, that is, the load energy.

That is, the air volume at the first pressurization (A of FIG. 4) is maintained at 1900 to 2300 Nm 3 / min, preferably 2100 Nm 3 / min, in order to apply pressure to the charging coke (144 of FIG. 4). In case of deviation, the pressure is weak and it is difficult to discharge the melt or the air volume is excessive.

And, in order to increase the melt level at the time of secondary pressurization, in consideration of the melt discharged at the first pressurization, the air flow rate is maintained at 1300 to 1700 Nm 3 / min, preferably 1500 Nm 3 / min, wherein the range As described above, as described above, the pressure is weak, so that it is difficult to discharge the melt or the air volume is excessive, so the allowable pressure loss may exceed the management standards.

At this time, the top pressure maintains 2,500 g / cm 2, which is the maximum top pressure that can be applied in a large blast furnace currently operating in Korea, as described above.

Next, the blast furnace longitudinal wind operation method of the present invention described so far is as follows.

When the decompression operation for the breeze starts, the air flow is gradually reduced as described above while watching the change of the charge level (L1 in FIG. 2), and the top pressure is kept constant at 2,500 g / cm 2.

In other words, the top pressure is applied much more than the amount of air flow in the blast furnace operation in the daily blast furnace operation, which is to maintain the maintenance of the allowable pressure loss described above.

Then, the work is carried out to the point (L1) where the charge level is 23m which is slightly higher than the level of the tip of the tuyere. Lowered.

However, in the present invention, although the air flow is lowered to cope with the local gas flow change in response to the lowering of the charge level, a separate pressurizing charge (ex. 142 of FIG. 3) is not used except for coke such as silica. As a result, the top pressure is maintained at a maximum value (2,500 g / cm 2) in order to ensure a uniform pressurizing effect on the melt in the furnace.

Therefore, the level of the bottom melt 110 'is lowered below the starting point level (L2 in FIG. 4), and thus, the level of the bottom bottom melt is lowered at the starting point 104 so that the melt does not come out of the starting point. Only the emergence phenomena occur repeatedly.

At this time, when the pressurized coke 144 is charged, the melt porosity remaining in the bottom part is lowered from 23% to 21% due to the self-load of the charged coke and the top pressure maintaining the maximum value. As the level rises and rises, more discharge occurs through the exit.

On the other hand, Figure 5 is a graph showing the blast furnace vertical wind operation according to the present invention (BV), the top pressure (TP) and the charge level (Stock Level).

That is, in the blast furnace vertical operation, the top pressure is maintained at a maximum (for example, 2,500 g / cm 2) up to the point of reaching 21 m (P1 in FIG. 5) of the charge level, and then the point at which the charge level is 23 m (in FIG. 5). In P2), 100 tons of coke pressurized charges are charged by a conventional charging method, and then the air flow is maintained at a level of 2100 Nm 3 / min, at which time the top pressure is increased from 2,000 g / cm 2 to 2,500 g / cm 2. To pressurize and pressurize first and increase the top pressure from 1,500g / cm2 to 2,500g / cm2 while maintaining the next air volume at 1500 Nm3 / min (P3 in FIG. 5) (P3 in FIG. 5). The change of the air volume, the stationary pressure, and the charge level in the case of carrying out the above is shown.

While the invention has been shown and described in connection with specific embodiments so far, it will be appreciated that the invention can be modified and modified in various ways without departing from the spirit or scope of the invention as set forth in the claims below. It will be appreciated that those skilled in the art can easily know.

1 is a schematic diagram showing a typical blast furnace operation

Figure 2 is a schematic diagram showing a charge level reduction state in known jong pong operation

Figure 3 is a state of operation shown in contrast to the present invention using the coke and pressurized charge of the silica to ensure the breathability by mixing the crushed coke and iron ore during the operation of the longitudinal wind, using only coke as the pressurized charge

Figure 4 is a detailed view showing the blast furnace bottom section

5 is a graph showing the air flow rate, the stationary pressure and the charge level during blast furnace vertical wind operation according to the prior art and the present invention

Figure 6 is a graph showing the allowable pressure loss according to the air permeability secured by the charging of lump coke and iron ore in the blast furnace vertical wind operation of the present invention

Explanation of symbols on the main parts of the drawings

10 .... Iron Ore 20 .... Coke Coke

100 .... blast furnace 102 ...

104 .... exit 110 .... charges (iron ore + coke)

120 .... Blowhole 140 .... Pressurized Charge

144 .... Pressurized Coke

Claims (4)

Charging iron ore and lumped coke into the blast furnace to ensure breathability during blast furnace operation; Performing deduction while maintaining the constant pressure up to the end of the vertical wind operation; Charging the pressurized coke to the blast furnace at the time point of completion of the reduction; And, Increasing the top pressure while maintaining the air volume in the charged pressurized charge; Blast furnace blast operation method configured to enable the minimization of the melt in the furnace, including. The method of claim 1, In the charging step of iron ore and lump coke, blast furnace blast operation method characterized in that the charging of the mixed iron ore and the lump coke, and then mixed charging the small iron ore and lump coke. The method according to claim 1 or 2, The top pressure is maintained at 2,400-2,500 g / cm2 until the end of the vertical wind operation, and the top pressure is increased to 2,400-2,500 g / cm2 while maintaining the air volume at 1900-2300 Nm3 / min. Blast furnace vertical wind operation method characterized by pressing the car. The method of claim 3, After the first pressurizing, while maintaining the air flow rate at 1400-1600 Nm3 / min, the top pressure is increased to 2,400-2,500 g / cm 2, followed by secondary pressurization to increase the level of the bottom melt and discharge the blast furnace. How to operate.

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