JP2006137986A - Method for operating hot blast stove - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for operating a hot blast stove, in which when the change-over of blasting between the prior hot blast stove and the following hot blast stove is performed, the variation of the blasting quantities and the blasting temperatures are relaxed and also, the thermal efficiency can be improved, in the case of blasting while duplicating the prior hot blast stove having low blasting temperature and the following hotblast stove having high blasting temperature. <P>SOLUTION: In the method for operating the hot blast stoves, in which hot-blasting is continuously injected into a blast furnace while partially duplicating the latter stage parallel blasting period of the prior hot blast stove and the early stage parallel blasting period of the following hot blast stove by setting the plurality of hot blast stoves so as to be three sectional blasting periods of the prior stage parallel blasting-one set blasting-the following stage parallel blasting, when the change-over of the blasting between the prior hot blast stove and the following hot blast stove is performed, the variation of the blasting quantity and the blasting temperature are reduced by continuously changing the blasting quantity distributing ratio with a fixed gradient. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for operating a hot stove to supply hot air to a blast furnace.

As is well known, a hot blast furnace that supplies hot blast to a blast furnace conceptually generates combustion gas from fuel gas and air in a combustion chamber, and sends the combustion gas to a heat storage chamber to heat bricks (checker bricks). The temperature of the hot air obtained by passing cool air through the brick layer in the heat storage chamber after adjusting the temperature for a certain period of time during which the combustion exhaust gas is discharged outside the system (heat storage period) is adjusted in the dome and the mixed cooling chamber. Thus, the period of supplying the lower part of the blast furnace (the blowing period) is repeated for a certain period of time.
This hot stove is arranged in 3 to 4 units with respect to one blast furnace, and as its blowing pattern, for example, 3 single blows in the case of 3 placements, 4 parallel blows in the case of 4 placements, etc. are selected, The hot air blowing period of each hot blast furnace is made continuous so that hot air can be continuously supplied to the blast furnace.

In the case of the former single air blowing, basically, the air is switched in order so that the air blowing periods of the hot stoves do not overlap during one cycle.
In the case of the latter parallel air blowing, basically, the air blowing periods of the front and rear hot stove are switched so as to partially overlap during one cycle.
In either case of the former or the latter, it is necessary to switch the hot blast furnace so that it can continuously blow into the blast furnace. In particular, the individuality of each furnace such as the combustion conditions, heat storage characteristics, and pipe length (distance to the blast furnace) for each furnace. Due to the difference, it is inevitable that fluctuations in the air flow rate and air temperature will occur between the hot stoves to be switched.

As methods for operating a hot stove capable of improving such problems, various methods have been proposed that aim to reduce fluctuations in the blowing temperature and reduce the amount of input heat.
For example, in Patent Document 1, air temperature fluctuations are reduced by duplicating the air blowing periods of a preceding hot air furnace having a low air temperature and a subsequent hot air furnace having a high air temperature and optimizing a parallel air blowing cycle. Is disclosed.

In the case of these methods, for example, as shown in the blast furnace air temperature column of FIG. 3, the difference Δ between the maximum temperature Tb and the minimum temperature Ta of the air flow in the first period parallel air flow, the first air flow, and the second time parallel air flow period in the air blowing cycle. There is a problem that t becomes large and it is difficult to realize stable operation of the blast furnace.
The main cause of the increase in Δt is that the two air blowers with the succeeding furnace are started when the air temperature of the preceding furnace is lowered to the temperature Ta. At this time, the succeeding furnace is in a high temperature state. In order to perform a large amount of ventilation, the temperature of the hot air supplied to the blast furnace rises rapidly to the temperature Tb. Further, in order to rapidly reduce the amount of air blown from the preceding furnace, a sudden increase from the lowest temperature Ta to the highest temperature Tb is cited as a secondary cause.
JP 59-110710 A

  In the present invention, in the case of performing parallel air blowing with the preceding hot air furnace having a low air temperature and the subsequent hot air furnace having a high air temperature, when performing air blowing switching between the preceding hot air furnace and the succeeding hot air furnace, Provided is a hot stove operating method capable of realizing stable operation of a blast furnace by reducing fluctuations in the air flow rate and air temperature, and capable of improving thermal efficiency.

In order to solve the above-mentioned problems advantageously, the present invention has the following (1) to (2).
(1) A plurality of hot blast furnaces having a blast period of three periods of the first period parallel blast, one group blast, and the latter period parallel blast are arranged, and the second stage parallel blast period of the preceding hot blast furnace and the first stage parallel of the succeeding blast furnace. In the operation method of a hot stove that continuously blows hot air to the blast furnace with a part of the air blowing period, when the air is switched between the preceding hot stove and the succeeding hot stove, the air volume distribution rate is continuously changed with a constant gradient. Therefore, the operating method of a hot stove characterized by reducing a ventilation volume variation and a ventilation temperature variation variation.
(2) The air flow rate decrease gradient from the first air blow end point of the preceding hot stove to the late parallel air blow end point is the same as the air flow rate increase gradient from the previous air blow start point of the succeeding hot stove to the start point of the single air blow. And the operating method of the hot stove as described in said (1) characterized by overlapping a ventilation period so that this decrease gradient and this increase gradient may cross in the intermediate point area | region.

According to the present invention, the air flow temperature distribution rate is continuously changed with a constant gradient during the period of switching the air flow by overlapping the preceding hot air furnace having a low air blowing temperature and the succeeding hot air furnace having a high air blowing temperature. Variations can be reduced.
Further, by reducing the variation in the blowing temperature, it is possible to reduce the average value of the blowing temperature and to reduce the heat intensity. Furthermore, the air temperature can be increased to improve the thermal efficiency.
Moreover, the hot metal temperature can be stably reduced within an appropriate range, and the low [Si] operation for reducing the [Si] concentration in the hot metal can be stably performed, so that hot metal with good quality can be produced.

  In the present invention, a blowing pattern in which the blowing period in one blowing cycle of each hot stove is divided into three periods of the first period parallel blowing, the first group blowing, and the latter parallel blowing is adopted, and the space between the preceding hot wind furnace and the subsequent hot wind furnace is adopted. This is applied to the case where a part of the blowing period is overlapped when switching the blowing period. Basically, one unit in the preceding hot stove is used when switching the blowing between the preceding hot stove and the succeeding hot stove. The decreasing gradient of the blowing amount from the blowing end point and the increasing gradient of the blowing amount from the blowing start point to the one blowing start point in the subsequent hot stove are crossed with a constant gradient (the blowing amount distribution rate is a constant gradient). By continuously changing the air flow rate variation and the air temperature variation, the stable operation of the blast furnace is facilitated.

  FIG. For convenience, the air blowing patterns divided into three periods of the first period parallel blowing, the first group blowing, and the latter period parallel blowing in one blowing cycle (about 200 minutes) in one hot stove are referred to as “No. 1 No. 1 hot stove and its front and rear No. 4 hot stove, no. 2 shows the air blowing patterns of the two hot air furnaces superimposed (the combustion period is not shown).

Furthermore, this is no. It is shown on the basis of one hot stove, and is an increasing gradient from the start point of parallel air blow in the previous period (air flow rate 0%) A to the start point B of single air blow (air flow rate 100%) which is the maximum area of air flow rate It is continuously changed at a constant gradient of tu and a decreasing gradient td from the end point B ′ of the single air blowing (air flow rate 100%) to the end point of the late parallel air flow (air flow rate 0%) C.
This No. No. 1 which becomes the preceding hot stove in this period No. 4 which becomes two-stage ventilation (mixed ventilation) by overlapping the period of the latter parallel blowing of the four hot air furnaces, and becomes the latter hot air furnace in this case, during the latter period of the latter parallel blowing. The switching air blowing is performed so that two air blowing (mixed air blowing) is performed by overlapping the period of the parallel air blowing of the two hot stove.

Continuously changing the air flow rate distribution rate at the time of this air flow change with a constant gradient (increase gradient tu, decrease gradient td) is to use a flow rate control valve and set the change pattern of the opening degree Cv value. Easy to do.
In this case, since the pipe length from each hot stove to the blast furnace is different, considering this, the timing of each switching so that two air blows (mixed blow) by the air blow switching of each hot stove can be performed accurately and smoothly. The switching valves are opened and closed and the opening is changed (constant gradient).

2 shows four hot stoves that employ the air blowing pattern according to the present invention shown in FIG. 1 hot stove-No. 2 Hot stove-No. 3 hot stove-No. No. 4 hot stove-No. The conceptual flow of the hot stove operation example which switches ventilation in order of 1 hot stove is shown partially.
FIG. 3 shows numerical values and diagrams in the case of performing the hot stove operation (simulation) as shown in FIG. 2 in comparison with the case of the hot stove operation example (conventional example) employing the conventional air blowing pattern. It is a thing.

In the conventional example, as shown in the figure, the blowing period in one blowing cycle of the hot stove (one hot stove) is divided into three sections of the first period parallel blowing, the first group blowing, and the latter parallel blowing as in the embodiment. Is constant at 1 unit air flow rate of 100%, the previous air flow rate is constant at about 60%, and the late air flow rate is constant at about 40%. The valve is switched by the opening degree of the valve that causes a large step in the air flow rate.
Here, for the sake of convenience, no. 1 No. 1 hot stove and its front and rear No. 4 hot stove, no. The blast pattern of the two hot stove is shown in an overlapping manner.
[Example of operation]

  In this embodiment, one cycle of blowing in each hot stove is set to 200 minutes, divided into 90 minutes in the previous period parallel blowing time, 10 minutes in the first group blowing, and 90 minutes in the latter period parallel blowing. 90/100% / min, the decrease gradient (β) of late parallel ventilation was set to −90 / 100% / min.

According to this example operation, the following improvements are possible compared to the comparative example operation.
(1) The blowing temperature to the blast furnace is 1185 to 1163 degrees, the difference (Δt ') between the highest temperature (Tb') and the lowest temperature (Ta ') is reduced, and the blowing temperature average can be reduced to about 1173 ° C. The blowing cost can be cut down.
(2) The combustion gas flow rate can be reduced by 1.2%, the combustion gas sensible heat can be reduced by about 1%, and the heat intensity can be saved.
(3) The hot metal temperature can be lowered by about 6.4%, and the hot metal [Si] concentration can be lowered by about 0.034% to perform a low [Si] operation.
It was confirmed that.

The present invention is not limited to the contents of the above embodiments. The type, structure, layout, blow pattern, operation flow, etc. of the hot blast furnace depend on the furnace volume of the blast furnace, the amount of tapping, basic operation conditions, operation schedule, charging materials, hot air, pulverized coal (heavy oil) blowing conditions, etc. Therefore, there is a change within a range that satisfies the scope of the claims.
In addition, when changing the air flow rate distribution rate continuously with a constant gradient (increase gradient, decrease gradient), the constant gradient is shown as a straight line, but it may be a curve or a semi-constant combination of a straight line and a curve. A gradient can be considered.

Explanatory drawing which showed notionally the ventilation pattern example of the hot stove by this invention. Explanatory drawing which showed notionally the example of the hot stove operation flow which employ | adopted the ventilation pattern by this invention. Explanatory drawing which shows a part of operation result of the hot stove by the Example of this invention and a prior art example.

Claims (2)

  A plurality of hot blast furnaces having a blast period of three periods of the first period parallel blast, one group blast, and the second period parallel blast are arranged, and the second parallel blast period of the preceding hot blast furnace and the first parallel blast period of the succeeding hot blast furnace are set. In the operation method of the hot stove that continuously blows hot air to the blast furnace with some overlap, at the time of air blow switching between the preceding hot stove and the succeeding hot stove, by continuously changing the air volume distribution rate with a constant gradient, A method for operating a hot stove characterized by reducing fluctuations in air flow and air temperature. The same is the same as the airflow decrease gradient from the end of the first hot air furnace to the end of the second parallel airflow, and the airflow increase gradient from the start of the first parallel airflow to the start of the first air blower The method of operating a hot stove according to claim 1, wherein the blowing period is overlapped so that the decreasing gradient and the increasing gradient are crossed in the middle point region.

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