RU2769340C2 - Blast heating device for blast furnace and method of operation of blast heating device for blast furnace - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: group of inventions relates to a blast heater system, as well as to a blast heating method for a blast furnace in a heater, made with possibility of blowing operation for supply of hot blast to blast furnace. Blast heater system for blast furnace comprises blast heater, made with possibility of blowing operation for supply of hot blast to blast furnace and heating operation for combustion of fuel gas in blowing heater, fuel gas supply line, made with possibility of blast furnace top gas supply to blast heater as fuel gas, and supercharger provided in fuel gas supply line to increase fuel gas pressure so that pressure in the blast heater during the heating operation is equal to the pressure in the blast heater during the blasting operation.

EFFECT: invention discloses a blast heating device for a blast furnace and a method of operating the blast heating device for a blast furnace.

8 cl, 4 dwg

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

[0001]

The present invention relates to a blast preheater system, as well as to a method for operating a blast preheater.

BACKGROUND OF THE INVENTION

[0002]

A blast preheater (aka air heater) was used to supply hot blast to a blast furnace for iron production (see Patent Document 1).

In the blast preheater, the heating and blowing operations are repeated.

During the heating operation, fuel gas and combustion air are supplied from outside and burned inside the blast preheater to heat the heat storage bricks in the blast preheater to a high temperature.

During the blowing operation, the air supply direction is reversed from the air supply direction during the heating operation, and the supplied air is heated by the heat storage bricks to a high temperature to be supplied to the blast furnace.

[0003]

The blast heater includes a plurality of blast heaters arranged in parallel. When one of the blast preheaters is in the heating operation state, the rest of the blast preheaters continue to be in the blast operation state in order to avoid interruption of the hot blast supply to the blast furnace.

The commonly used gaseous fuel in the heating operation is BFG (blast furnace top gas). The exhaust gases of combustion are released into the atmosphere. Accordingly, the pressure in the blast preheater (sometimes hereinafter simply referred to as "preheater pressure") is slightly higher than atmospheric pressure.

In contrast, air introduced into the blast preheater is compressed by a high-pressure fan or the like during the blowing operation to blow hot blast into the inside of the high-pressure blast furnace so that the pressure in the blast preheater is equal to or greater than the internal pressure. in a blast furnace.

[0004]

When using the blast preheater, the heating operation and the blast operation are switched over at a predetermined interval, and the pressure in the blast preheater is adjusted at the time of switching so that its level matches the pressures in the furnace during the heating operation and the blast operation.

When the heating operation is switched to the blast operation, a pressure equalization operation is performed to introduce compressed air into the blast preheater to increase the pressure in the blast preheater.

When the blast operation is switched to the heating operation, a depressurization operation is performed to gradually remove air from the blast preheater so as to reduce the pressure in the preheater.

[0005]

The blast preheater system disclosed in Patent Document 1, which increases the pressure of fuel gas and air supplied during the heating operation, offers the following improvements.

In particular, since the pressure in the preheater during the heating operation increases relative to the pressure in a typical preheater (i.e., substantially atmospheric pressure), the volume of combustible gas, and hence the size of the preheater housing and ancillary equipment, can be reduced. In addition, the preheater pressure during the heating operation becomes closer to the preheater pressure during the blowing operation, so that the pressure difference between the heating and blowing operations, and hence the time normally required for the pressure equalization operation and the depressurization operation, can be reduced, thereby saving energy.

In order to increase the pressure in the preheater during the heating operation, Patent Document 1 specifically discloses that blast furnace gas (BFG) used in the heating operation in the blast preheater system is taken from the high pressure part of the blast furnace top gas utilization line located before TRT (Top Gas Pressure Recovery Turbine Generating System).

LIST OF CITATIONS

PATENT DOCUMENTS

[0006]

Patent Document 1: JP 59-143008 A

SUMMARY OF THE INVENTION

PROBLEMS SOLVED BY THE INVENTION

[0007]

As described above, the BFG used in the heating operation is taken from the high pressure part of the BFG recycling line of the blast furnace located upstream of the TRT to increase the preheater pressure during the heating operation in the blast preheater system of Patent Document 1.

However, the BFG pressure (e.g. 280 kPa) withdrawn from the BFG portion of the BFG disposal line before the TRT is not sufficient to increase the preheater pressure during the heating operation to the preheater pressure during the blow operation (e.g. 500 kPa), which does not eliminate the need for pressure equalization operation and in pressure relief operation. In other words, although the adjustable pressure difference between the pressure equalization operation and the pressure relief operation can be reduced in Patent Document 1, the need for performing the pressure equalization operation and the pressure relief operation still remains, resulting in reduced operability and failure to improve operational efficiency.

[0008]

In addition, the selection of BFG from a part of the BFG recycling line of a blast furnace before TRT, as disclosed in Patent Document 1, leads to the following disadvantages.

BFG withdrawn from a portion of the BFG recycling line close to the blast furnace is subject to pressure fluctuations at the top of the blast furnace. Accordingly, the BFG pressure becomes unstable, destabilizing the heating operation of the blast preheater.

In addition, BFG, which has a high pressure, and thus contains a large amount of moisture, may generate mist when it is introduced into the blast preheater, which will destroy the refractory bricks.

[0009]

It is an object of the present invention to provide a blast preheater system, as well as a method for operating the blast preheater, which is capable of sufficiently pressurizing the preheater during the heating operation.

WAYS TO SOLVE PROBLEMS

[0010]

A blast preheater system in accordance with one aspect of the present invention includes: a blast preheater configured to perform a blast operation to supply hot blast to a blast furnace and a heating operation to burn fuel gas in the blast preheater; a fuel gas supply line configured to supply top gas of the blast furnace to the blast preheater as fuel gas; and a supercharger provided in the fuel gas supply line to increase the pressure of the fuel gas.

[0011]

The operation method of a blast preheater according to another aspect of the present invention is to perform a blast operation to supply hot blast to a blast furnace and a heating operation to burn fuel gas in the blast preheater, and includes: supplying blast furnace top gas from the blast furnace to the blast preheater as a fuel gas; and

increasing the pressure of the fuel gas supplied to the blast heater using a supercharger.

[0012]

In accordance with the above aspects of the present invention, the pressure of the fuel gas supplied to the blast preheater is increased by a supercharger to a sufficiently high level.

Accordingly, the pressure in the blow preheater during the heating operation can be increased sufficiently to become equal to the pressure in the preheater during the blow operation. Since the pressure difference in the preheater between the heating operation and the blowing operation is eliminated, the pressure equalization operation and the pressure release operation are no longer necessary and can be omitted.

[0013]

The pressure equalization operation and the pressure relief operation can be completely eliminated, so that the operating steps for them can be eliminated, and the operating efficiency and operating costs can be reduced. In addition, the time interval occupied by the pressure equalization operation and the pressure release operation can be eliminated, so that the operating efficiency can be improved. In addition, the number of blast heaters can be reduced. In addition, condensation of moisture in the BFG remaining in the blast preheater, which occurs during a typical depressurization operation in accordance with depressurization of the preheater, can be prevented by eliminating the depressurization operation.

[0014]

In addition, in accordance with the above-described aspects of the present invention, the temperature of the fuel gas introduced into the blast preheater can be increased by adiabatically compressing with a supercharger. Accordingly, the normally required fuel gas preheater and the normally required additional fuel supply can be eliminated, thereby reducing the number and size of equipment and operating costs.

[0015]

In the above-described aspects of the present invention, the heating operation time can be shortened by pressurizing the preheater during the heating operation. In general, the duration of the heating operation is set to be longer than that of the blowing operation, and the above-described pressure equalization operation and the pressure release operation are required. However, the pressure equalization operation and the pressure release operation may be omitted in the above-described aspects of the present invention. In addition, the duration of the heating operation can be reduced substantially to the duration of the blowing operation. Accordingly, the operation schedule can be simply set as a cycle from the heating operation and the blowing operation.

[0016]

In addition to the effects described above, the aforementioned aspects of the present invention offer effects associated with increasing fuel gas pressure as disclosed in Patent Document 1.

In particular, since the difference between the pressure in the preheater during the blowing operation and the pressure in the preheater during the heating operation can be reduced, and pressure fluctuations during the pressure equalization operation and the pressure relief operation can be eliminated, the service life of the components of the blowing heater can be extended. In particular, for example, fatigue failure of the iron shell, cracking of refractory bricks in the blast preheater, and formation of gaps in the seams of the brickwork (and, accordingly, leakage of gas from the blast preheater through the seams of the brickwork) can be prevented.

In addition, the amount of fuel gas can be reduced by pressurizing the preheater during the heating operation, so that the cross section of the blast preheater can be reduced, the combustion efficiency during the heating operation can be improved, and the size of the preheater and equipment can be reduced.

[0017]

In the blast preheater system according to the above-described aspect of the present invention, it is preferable that the fuel gas supply line draws top gas from the top gas recovery line to remove top gas from the top gas of the blast furnace at a position after the turbine top gas pressure recovery system.

[0018]

In the operation method of the blast preheater according to the above-described aspect of the present invention, it is preferable that the top gas which is discharged from the top of the blast furnace and whose pressure is recovered by the turbine top gas pressure recovery system is used as fuel gas.

[0019]

In the above arrangement, top gas whose pressure is recovered by the turbine top gas pressure recovery system is used as a fuel gas, so that the effect of pressure fluctuations at the top of the blast furnace is smoothed out by the turbine top gas pressure recovery system to stabilize the pressure fluctuations of the fuel gas.

In the arrangement described above, the top gas used as fuel gas, the pressure of which is recovered by the turbine top gas pressure recovery system and is thus low, contains little moisture, so that, for example, refractory bricks in the blast preheater are not destroyed due to the mist generated in the preheater. blast when top gas is introduced as fuel gas.

In the above arrangement, even when a low-pressure top gas is used, the pressure of the fuel gas introduced into the blast preheater can be set to a sufficiently high level by the blower.

[0020]

In the blast preheater system according to the above-described aspect of the present invention, it is preferable that the blast preheater system further includes an exhaust gas heat recovery system configured to recover the pressure and heat of the exhaust gases exiting the blast preheater during the heating operation so that the blower was driven by the pressure and heat of the waste gases utilized by the waste heat recovery system.

[0021]

In the method of operating the blast preheater according to the above-described aspect of the present invention, it is preferable that the method further includes utilizing the pressure and heat of exhaust gases exiting the blast preheater during the heating operation so that the blower is driven by the recovered pressure and heat. exhaust gases.

[0022]

In the above arrangement, the blower can be driven by the pressure and heat of the exhaust gases recovered from the exhaust gases exiting the blast preheater during the heating operation, so that the operating cost can be reduced. The blower in the above-described aspects of the present invention, the advantages of which have been described above, can be driven by the energy of the exhaust gases exiting the blast preheater during the heating operation, so that the cost of implementing the present invention can be minimized.

[0023]

In the operation method of the blast preheater according to the above aspect of the present invention, it is preferable that the method further includes cycling the blowing operation, the blowing-to-heating transfer operation to switch the blast preheater from the blowing operation to the heating operation, the heating operation, and the heating transfer operation to blow to switch the blow preheater from a heating operation to a blow operation, where the total duration of the blow-to-heat transition operation, the heating operation, and the heating-to-blast transition operation is equal to or less than the duration of the blow operation.

[0024]

In the above arrangement, for example, two blast preheaters are used to operate alternately, that is, while the blast operation is performed by one of these blast preheaters, the other blast preheater performs a blow-to-heat transfer operation, a heating operation, and a heat-to-blast transfer operation. .

In the above-described aspects of the present invention, the blow-to-heat changeover operation and the heat-to-blast changeover operation, which do not include pressure control (i.e., pressure equalization and depressurization), only require switching the supply of combustible gas and air, and can be performed in a very short period of time.

In addition, the heating operation of the present invention, which is performed under high pressure, can provide sufficient heat retention for substantially the same period of time as the duration of the blowing operation.

[0025]

Therefore, while the blowing operation is performed by one of the two blast preheaters, the heating operation performed between the blast-to-heat transfer operation and the heat-to-blast transfer operation can be performed by the other blast preheater, thus allowing the two blast preheaters to perform the same the same blast operation as a typical blast operation performed by three blast heaters. In this way, the hot blast can be supplied to the blast furnace without interruption during the blast operation, which is alternately carried out by these two blast preheaters.

It should be noted that the present invention is applicable to any two of the blast preheaters in a blast preheater system having an even number of blast preheaters.

[0026]

In the operation method of the blast preheater according to the above aspect of the present invention, it is preferable that the method further includes cycling the blowing operation, the blowing-to-heating transfer operation to switch the blast preheater from the blowing operation to the heating operation, the heating operation, and the heating transfer operation to a blast to switch the blast preheater from a heating operation to a blowing operation, where the total duration of the blow-to-heat transition operation, the heating operation, and the heating-to-blast transition operation is equal to or less than twice the duration of the blow operation.

[0027]

In the above arrangement, when, for example, three blast preheaters are used for operation, while the blast operation is performed by one of the three blast preheaters, the blast-to-heat changeover operation, the heating operation, and the heat-to-blast changeover operation are performed by the other two. blast heaters.

Specifically, the first blast preheater performing the blowing operation is switched to the heating operation, and the blowing operation is performed by the second blast preheater. After the predetermined blowing operation time elapses, the second blowing preheater switches from the blowing operation to the heating operation, and the blowing operation is performed by the third blowing preheater. At the same time, the heating operation by the first blast preheater is half completed. After the predetermined blowing operation time elapses, the third blast preheater switches from the blowing operation to the heating operation, and the blowing operation is performed by the first blast preheater.

Therefore, while the blowing operation is performed by one of these three blast preheaters, the heating operation between the blast-to-heat transfer operation and the heat-to-blast transfer operation can be performed by the other two of the three blast preheaters, thus ensuring efficient operation of these three preheaters. blast. In this case, the hot blast can be supplied to the blast furnace without interruption during the blast operation, which is carried out in turn by each of these three blast preheaters.

In addition, in the above arrangement, the duration of the heating operation is approximately twice as long as the duration of the blowing operation. Accordingly, the duration of the blowing operation can be shortened in order to reduce the decrease in the maintained temperature. In addition, the size of the combustion chamber can be reduced.

[0028]

It should be noted that the present invention is applicable to any combination of three blast preheaters in a blast preheater system having a multiple of three blast preheaters.

When three blast preheaters are used, the blast operation can be performed by two blast preheaters while the heating operation is performed by one blast preheater. The two blast preheaters can perform the blowing operation so that the blowing operation is initially performed only by the first of the two blast preheaters, and after the blowing operation performed by the first of the two blast preheaters is half completed, the second of the blast preheaters can start the operation. blast, whereby the temperature of the hot blast for the blast furnace can be increased compared to the temperature of the above-described alternating operation of two or an even number of blast preheaters.

[0029]

According to the above-described aspects of the present invention, a heater system and a method of operating blast heaters capable of sufficiently pressurizing the heater during a heating operation can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030]

Fig. 1 schematically shows a blast preheater system in accordance with an exemplary embodiment of the present invention.

Fig. 2 is a schematic diagram showing a blowing operation and a heating operation according to an exemplary embodiment.

Fig. 3 is a schematic diagram showing a blast operation and a heating operation according to a typical blast preheater system.

Fig. 4 is a schematic diagram showing a blowing operation and a heating operation according to one modification of the exemplary embodiment.

DESCRIPTION OF EMBODIMENTS

[0031]

As shown in FIG. 1, the system 1 of the blast heater is configured to supply hot blast to the blast furnace 2.

The blast furnace 2 includes a top 21 and charging equipment 22 provided on the top 21 and configured to charge raw materials, mainly in the form of iron ore and coke. The blast furnace 2 includes a plurality of lances 23 arranged in a circular manner on the furnace body. The blast heater system 1 is connected to each of the lances 23 via an annular pipeline 24.

The hot blast supplied from the blast heater system 1 is distributed in the annular pipeline 24 for its uniform introduction into the blast furnace through the tuyeres 23. BFG (top gas).

[0032]

Top gas utilization line 3 is connected to blast furnace 2.

The top gas recycling line 3 includes a top gas pipeline 31 connected to the top 21 and configured to withdraw the BFG, as well as a dust collector 32, a primary venturi scrubber 33 and a secondary venturi scrubber 34, through which the BFG passes in series to remove dust therefrom.

Residual energy (eg, pressure and heat energy) of the dedusted BFG is recovered by the turbine top gas pressure recovery (i.e., TRT) system 35 for reuse after being converted into electrical energy and the like.

The BFG whose energy has been recovered is stored in the gas tank 36 for use as fuel for other equipment and the like.

[0033]

The blast heater system 1 includes three blast heaters 4 (4A - 4C). Each of the heaters 4A to 4C is an external combustion air heater including a regenerative chamber 41 and a combustion chamber 42.

The regenerative chamber 41 includes an interior lined with heat recovery packed bricks, a top portion communicating with the combustion chamber 42, and a bottom portion connected to a cold blast line 43, and an exhaust gas line 44.

The combustion chamber 42 includes a middle part connected to a hot blast line 45 extending up to an annular line 24 and a lower part provided with a burner block connected to a combustion air line 46 and a fuel gas line 47 .

Each of the blast heaters 4A - 4C includes on/off valves (not shown) at respective fittings to the cold blast line 43, flue gas line 44 and hot blast line 45, configured to open/close the connections of the respective lines to the heaters 4A - 4C blast depending on the operation of the heaters 4A - 4C blast.

[0034]

A blast operation for supplying hot blast to the blast furnace 2 and a heating operation for storing heat are alternately performed in the blast preheater 4A to 4C.

During the blowing operation, the air introduced through the cold blast line 43 passes through the regenerative chamber 41 to be heated and converted into hot blast, which is supplied from the combustion chamber 42 through the hot blast line 45 to the annular line 24.

During the heating operation, the air from the combustion air line 46 and the gaseous fuel from the fuel gas line 47 are burned in the combustion chamber 42 by the burner unit so that high-temperature combustion products pass through the regenerative chamber 41 to store heat in the packing bricks. The combustion gases that have passed through the regenerative chamber 41 exit through the flue gas line 44 .

The interaction of these three blow preheaters 4A - 4C during the blow operation and the heating operation will be described in detail later.

[0035]

The cold blast line 43, which is provided with a high pressure fan 431, is configured to pressurize the intake air to a predetermined pressure and supply this air to the regenerative chamber 41 or the hot blast line 45. The high pressure fan 431 maintains the pressure in the regenerative chamber 41 and the combustion chamber 42 during the blowing operation at a predetermined high level to ensure hot blowing through the tuyeres 23 even when the internal pressure in the blast furnace 2 is high.

The flue gas pipeline 44 is provided with an exhaust gas pressure recovery turbine system 441 (eg, a turbine generator) for utilizing the residual energy (eg, pressure and heat energy) of the combustible gas exiting through the flue gas pipeline 44 .

[0036]

The combustion air conduit 46 is provided with an air supply fan 461 configured to pressurize external air into the combustion chamber 42 during the heating operation.

The fuel gas pipeline 47 is connected to the blast-furnace gas utilization line 3 via the fuel gas supply line 5 in order to enable the BFG from the blast furnace 2 to be used as fuel gas for the combustion chamber 42.

[0037]

The fuel gas supply line 5, which includes a discharge pipe 51 connected to the outlet of the turbine top gas pressure recovery system 35 of the blast-furnace gas recovery line 3, is configured to supply BFG taken from the attached part to the blast heater 4.

A fan 52 (a blower of the present invention) is provided for part of the fuel gas supply line 5 . The BFG, which is supplied through the fuel gas supply line 5 to the combustion chamber 42, and which is pressurized by the fan 52 to a predetermined level, can maintain the pressure in the combustion chamber 42 and the regenerative chamber 41 during the heating operation at a predetermined high level.

[0038]

The blower in the form of a fan 52 is driven by the energy recovered from the exhaust gas pressure recovery system 441 provided in the exhaust gas line 44 . For example, when a heating operation is performed in one of the blast heaters 4A - 4C, the BFG pressurizing fan 52 can be powered by energy recovered from at least one blast heater 4A - 4C during the heating operation.

[0039]

When the pressure is increased by the fan 52 to increase the pressure of the fuel gas (BFG) supplied from the fuel gas line 47 to the combustion chamber 42, the air pressure supplied from the combustion air line 46 to the combustion chamber 42 must be raised to balance combustion. The air pressure can be raised by the fan 461. It should be noted that the fan 461 can also be driven by the energy utilized by the turbine exhaust pressure recovery system 441. In addition, the air supply fan 461 can be replaced with a high pressure fan 431 if the high pressure fan 431 can provide additional air volume.

[0040]

In the blast preheater system 1 of the exemplary embodiment, two of the three blast preheaters 4A - 4C are used to alternately perform a blast operation and a heating operation in each of the blast preheaters.

As shown in FIG. 2, when two blow preheaters 4A, 4B are used, the blow operation and the heating operation are performed alternately, for example, in 45 minute cycles from the starting point (0 min).

[0041]

In the blowing preheater 4A, the blowing operation is carried out for 45 minutes from the starting point (0 minutes), the operation for switching from the blowing operation to the heating operation (the blowing-to-heating changeover operation) is carried out for 0.5 minutes, the heating operation is carried out for 44 min, and the switching operation from the heating operation to the blowing operation (the heating-to-blowing changeover operation) is performed within 0.5 minutes. The cycle of these four stages is then repeated.

The blowing operation, which lasts 45 minutes, is one cycle. A heating operation lasting 44 minutes and two switching operations between heating and blowing each taking 0.5 minutes lasts a total of 45 minutes (that is, one cycle).

[0042]

The pressure in the blast heater 4A is maintained at a predetermined level during the blast operation by the air pressure boosted by the high pressure fan 431 of the cold blast line 43. In contrast, during the heating operation, the BFG (fuel gas) pressure is increased by the fan 52 of the fuel gas supply line 5 so that the preheater pressure is maintained at the same level as during the blowing operation.

During the operation of the change from blast to heating and the operation of the change from heating to blow to reverse the direction of the air flow, some switching time is required to actuate the on-off valves (not shown) provided in each of the connecting parts of the air blast pipeline 43, the flue gas pipeline 44 pipeline 45 hot blast heaters 4A - 4C blast.

[0043]

The temperature in the blast preheater 4A decreases during the blast operation in accordance with the amount of hot blast to be dispensed. In contrast, during the heating operation, the temperature of the preheater gradually rises due to combustion in the combustion chamber 42, reaching the temperature required to start the blowing operation.

With such a short heating operation, a sufficient amount of heat can be stored because the pressure of the BFG (fuel gas) is increased by the fan 52 (blower) to allow the heating operation in the combustion chamber 42 to be carried out at high pressure.

[0044]

Unlike the above-described blast preheater 4A, in the blast preheater 4B, the blast-to-heat transfer operation is performed within 0.5 min from the starting point (0 min), the heating operation is performed for 44 min, the heating-to-blast transfer operation is performed for 0.5 min, and the blowing operation is performed for 45 min. The cycle of these four stages is then repeated.

Also, in the blow preheater 4B, the blowing operation (45 minutes) is one cycle, and the heating operation (44 minutes) and the blow-to-heat and heat-to-blast transition operations (0.5 minutes each) are 45 minutes in total (that is, one cycle).

Changes in pressure and temperature during the blow operation and the heating operation in the blow preheater 4B exhibit the same behavior as described for the blow preheater 4A.

[0045]

As described above, the blow preheaters 4A, 4B may alternately perform a blow operation and a heating operation with a 45-minute cycle in the exemplary embodiment as shown in FIG. 2.

The blow operation proceeds completely during the 45 minute cycle in blow heaters 4A, 4B. Accordingly, the hot blast is fed into the blast furnace 2 without interruption. In contrast, the heating operation, which is carried out at high pressure, provides the desired heat retention for 44 minutes. Thus, the heating operation as well as the blow-to-heat changeover operation and the heat-to-blast changeover operation can be performed in a 45-minute cycle, so that alternating blow-and-heat operations in a 45-minute cycle can be achieved with these two heaters 4A , 4B blast.

For the operation shown in Fig. 2, a combination of preheaters 4A, 4C blast or preheaters 4B, 4C blast can be used instead of a combination of preheaters 4A, 4B blast.

[0046]

In the blast preheater system 1 of the exemplary embodiment, typical blast and heating operations can be performed using the three blast preheaters 4A - 4C by performing the heating operation at ambient pressure without using fan 52 (blower).

As shown in FIG. 3, when the heating operation is performed at ambient pressure using the three blow preheaters 4A to 4C, the blow operation and the heating operation are performed alternately, for example, in 45-minute cycles from the starting point (0 min).

However, although the blowing operation is performed in one cycle (ie, 45 minutes), the heating operation is performed in two cycles (ie, 90 minutes) because the temperature raising process takes a long time. In addition, over two cycles (90 min), a 7.5 minute depressurization operation to reduce the high pressure during the blow operation to ambient pressure during the heating operation and a 7.5 minute pressure equalization operation to increase the ambient pressure during the high pressure heating operation during the blowing operation is performed before and after the 75-minute heating operation.

[0047]

As shown in FIG. 3, in each of the blow preheaters 4A to 4C, a 7.5-minute depressurization operation, a 75-minute heating operation, and a 7.5-minute pressure equalization operation, which are 90 minutes in total (i.e., two cycles), are performed after the above-described 45 min blowing operation (i.e. one cycle). The cycle of these stages is then repeated.

Here, the operations in the blast preheaters 4A - 4C are mutually shifted by one cycle, so that the hot blast is supplied to the blast furnace 2 without interruption. In other words, the blowing operation of the blowing preheater 4A is followed by the blowing operation of the blowing preheater 4B, followed by the blowing operation of the blowing preheater 4C, and then the blowing operation of the blowing preheater 4A is performed again. By repeating these operations, the blowing operation is continuously performed by one of the blowing preheaters 4A to 4C.

[0048]

As described above, in the typical blowing and heating operations shown in FIG. 3, the blast heaters 4A-4C that perform the ambient pressure heating operation require a large amount of time for the heating operation, and therefore the three blast heaters 4A-4C operate simultaneously to achieve the desired heat storage. In addition, in order to compensate for the pressure difference in the preheater between the heating operation and the blowing operation, a pressure equalization operation and a pressure release operation are necessary, resulting in complicated operation procedures.

[0049]

As described above, the blast preheater system 1 according to the exemplary embodiment offers the following advantages, especially when operating as shown in FIG. 2.

In an exemplary embodiment, the pressure of the fuel gas (BFG) supplied to the blast heater 4 (4A-4C) is increased by the fan 52 (blower) to a sufficiently high level.

Accordingly, the pressure in the blow preheater 4 during the heating operation can be increased sufficiently to become equal to the pressure in the preheater during the blow operation (see FIG. 2). Since the preheater pressure difference between the heating operation and the blowing operation is eliminated, the pressure equalization operation and the pressure relief operation (see FIG. 3) are no longer necessary and can be omitted.

[0050]

In the exemplary embodiment, the blowing operation and the heating operation of the blowing preheater 4 are performed as shown in FIG. 2 so that the pressure equalization operations and the pressure release operation as shown in FIG. 3 can be completely eliminated, thereby reducing the number of stages, operating efficiency and operating costs.

In addition, according to the operation of the blast preheater 4 shown in FIG. 2, the time period occupied by the pressure equalization operation and the pressure release operation shown in FIG. 3 can be eliminated so that the operating efficiency can be improved.

In addition, the operation of the blast preheater 4 shown in FIG. 2 requires only two of the blast heaters 4A - 4C, where one of the blast heaters 4A - 4C may be suspended or may be serviced.

In order to perform only the operation shown in FIG. 2, only two blast heaters 4 can be provided in the blast preheater system 1 (that is, the number of blast preheaters can be reduced).

[0051]

When the typical operation shown in FIG. 3, moisture in the BFG remaining in the blast preheater 4 is condensed during the pressure equalization operation in accordance with the pressure increase in the blast preheater. However, the operation shown in FIG. 2 does not require a pressure equalization operation, and thus moisture condensation in the blast preheater can be prevented.

[0052]

Furthermore, in the exemplary embodiment, the temperature of the fuel gas introduced into the blast preheater 4 can be increased by adiabatically compressing the fan 52 (the blower of the present invention) and the air supply fan 461 so as to raise the air pressure. Accordingly, the fuel gas preheater used in a typical blast heater system and the supply of normally required additional fuel can be eliminated, thereby reducing the number and size of equipment and operating costs.

[0053]

In an exemplary embodiment, the duration of the heating operation can be shortened by pressurizing the preheater during the heating operation, as described in the explanation of FIG. 2. Generally, the duration of the heating operation is set to be longer than that of the blowing operation, and the above-described pressure equalization operation and the pressure release operation are required. However, in the exemplary embodiment, the pressure equalization operation and the pressure release operation may be omitted. In addition to this, the duration of the heating operation can be reduced substantially to the duration of the blowing operation. Accordingly, the operation schedule can be simply set as a cycle from the heating operation and the blowing operation.

[0054]

Furthermore, in the exemplary embodiment, since the difference between the pressure in the preheater during the blowing operation and the pressure in the preheater during the heating operation, and hence the change in pressure during the pressure equalization operation and the depressurization operation (see Fig. 3), may be eliminated, the service life of the blast heater 4 components can be extended. In particular, for example, fatigue failure of the iron shell, cracking of refractory bricks in the blast preheater, and formation of gaps in the seams of the brickwork (and, accordingly, leakage of gas from the blast preheater through the seams of the brickwork) can be prevented.

In addition, the amount of fuel gas can be reduced by pressurizing the preheater during the heating operation, so that the cross section of the blast preheater can be reduced, the combustion efficiency during the heating operation can be improved, and the size of the preheater and equipment can be reduced.

[0055]

In an exemplary embodiment, the gaseous fuel of the blast preheater 4 is provided by the BFG (top gas) recovered through the top gas recovery line 3 from the top 21 of the blast furnace 2, where the BFG is withdrawn from a portion of the top gas recovery line 3 downstream of the top gas pressure recovery turbine system 35 through the outlet pipe 51 of the fuel gas supply line 5.

Accordingly, the BFG whose pressure is recovered by the turbine top gas pressure recovery system 35 is used as a fuel gas, so that the effect of pressure fluctuations in the top 21 of the blast furnace 2 is smoothed out by the turbine top gas pressure recovery system 35 to stabilize pressure fluctuations of the BFG supplied to the burner unit. heater 4 blasts.

In addition, BFG used as a fuel gas, the pressure of which is recovered by the turbine of the top gas pressure recovery system 35, and thus is low, contains a small amount of moisture, so that, for example, refractory bricks in the blast preheater 4 are not destroyed due to the mist generated in the blast preheater when the BFG is introduced into the burner block of the blast preheater 4.

[0056]

For comparison, when the BFG is withdrawn from the part of the blast furnace gas recycling line 3 before the turbine top gas pressure recycling system 35, as in the above-described Patent Document 1 (see the bypass pipe 51P in FIG. 1), the BFG that is supplied during the heating operation of the preheater 4 blast furnace may be affected by pressure fluctuations in the top 21 of the blast furnace 2 and contain more moisture due to the higher pressure than in the above arrangement, so that mist may form in the blast preheater 4 when BFG is introduced into the burner block of the blast preheater 4, possibly destroying refractory bricks.

However, in the exemplary embodiment, since the BFG is taken from the portion of the blast furnace gas recovery line 3 that is downstream of the top gas pressure recovery turbine system 35, these drawbacks can be avoided.

[0057]

In an exemplary embodiment, the fan 52 (blower) provided in the fuel gas supply line 5 is configured to increase the pressure of the BFG supplied to the blast preheater 4.

Accordingly, even when a low-pressure BFG whose pressure has been recovered by the turbine top gas pressure recovery system 35 is used, the pressure of the BFG introduced into the blast preheater 4 can be set to a sufficiently high level.

[0058]

In an exemplary embodiment, the exhaust gas pressure recovery turbine system 441 provided in the exhaust gas pipeline 44 utilizes the exhaust gas pressure and heat of the blast preheater 4, and the recovered exhaust gas pressure and heat energy is used to drive the fan 52 (blower) and the fan 461 pipeline 46 air for combustion. Accordingly, the fans 52, 461 can be driven by the energy recovered from the exhaust gas of the blast preheater 4 during the heating operation, so that the operating cost can be reduced.

Accordingly, the fan 52, configured to pressurize during the heating operation, the advantages of which have been described above, in the exemplary embodiment can be driven by the exhaust gas energy of the blast preheater 4 during the heating operation, so that operating costs can be minimized.

[0059]

As shown in FIG. 2, the operations of the two blast heaters 4 of the blast heater system 1 of the exemplary embodiment are switched on a 45 minute cycle. In contrast, the operations of the three blast preheaters 4 of the same blast preheater system 1 can be switched on a 30 minute cycle.

As shown in FIG. 4, the three blow preheaters 4A - 4C alternately perform a blow operation and a heating operation, for example, with a 30-minute cycle from the starting point (0 min).

[0060]

In the blowing preheater 4A, the blowing operation is carried out for 30 minutes from the starting point (0 minutes), the operation for switching from the blowing operation to the heating operation (the blowing-to-heating changeover operation) is carried out for 0.5 minutes, the heating operation is carried out for 59 min, and the switching operation from the heating operation to the blowing operation (the heating-to-blowing changeover operation) is performed within 0.5 minutes. The cycle of these four stages is then repeated.

The blowing operation, which lasts 30 minutes, is one cycle. A heating operation lasting 59 minutes and two switching operations between heating and blowing each taking 0.5 minutes lasts a total of 60 minutes (that is, two cycles).

[0061]

The pressure in the blast preheater 4A is the same as in FIG. 2.

Specifically, a predetermined pressure is maintained in the blast preheater 4A during the blowing operation by the air pressure raised by the fan 431 of the cold blast line 43 . In contrast, during the heating operation, the BFG (fuel gas) pressure is increased by the fan 52 of the fuel gas supply line 5 so that the preheater pressure is maintained at the same level as during the blowing operation.

During the blow-to-heat changeover operation and the heat-to-blast changeover operation for reversing the air flow direction, some switching time is required to actuate on-off valves (not shown) provided in each of the connecting parts of the cold blast line 43, the flue gas line 44 and pipeline 45 hot blast heaters 4A - 4C blast.

[0062]

The temperature in the blast preheater 4A decreases during the blast operation in accordance with the amount of hot blast to be dispensed. However, due to the short duration of the blowing operation, the temperature at the end of the blowing operation remains higher than the temperature at the end of the blowing operation shown in FIG. 2.

In contrast, during the heating operation, the temperature of the preheater gradually rises due to combustion in the combustion chamber 42, reaching the temperature required to start the blowing operation. However, in addition to the slight decrease in temperature during the blowing operation described above, since the heating operation is provided with a time of approximately two cycles (59 minutes), the temperature of the preheater may rise more slowly than in the heating operation shown in FIG. 2 (29 min), so that the heating operation can be performed at a lower combustion temperature and/or with less fuel gas consumption. In addition, the size of the combustion chamber 42 can be reduced.

[0063]

Unlike the blow preheater 4A described above, the blow preheater 4B performs from the starting point (0 min) the second half of the heating operation and a 0.5-minute heating-to-blast transfer operation, then a 30-minute blow operation, a 0.5-minute transfer operation. blow to heat, a 59 minute heat up operation, and a 0.5 minute heat to blow transition operation. These steps are then repeated.

The blow heater 4C performs from the starting point (0 min) a 0.5 minute blow-to-heat transfer operation, a 59-minute heating operation, a 0.5-minute heat-to-blast transfer operation, and a 30 minute blow operation. These steps are then repeated.

[0064]

As described above, the blow preheaters 4A-4C may sequentially perform a blow operation and a heating operation in a 30 minute cycle shown in FIG. 4. In addition, each of the blast heaters 4A to 4C alternately performs a blast operation for 30 minutes, so that hot blast can be supplied to the blast furnace 2 without interruption.

In addition, the pressure equalization operation and the pressure relief operation (see Fig. 3) are not necessary and can be omitted, and therefore the above-described disadvantages associated with pressure fluctuations during the pressure equalization operation and the pressure relief operation (for example, the influence equipment and moisture condensation) can be eliminated. When two blast preheaters are used to perform a blast operation, the blast temperature can be increased compared to a blast operation using one blast preheater.

[0065]

The present invention is not limited to the above-described exemplary embodiments, but includes modifications and the like, as long as these modifications and the like are are compatible with the present invention.

For example, the number of blast preheaters 4 provided in the blast preheater system 1 need not be three, but may be two (to perform the operation shown in Fig. 2), or four or more (to perform the operation shown in Fig. 2). .2, or the operation shown in Fig. 4). For example, when there are four blast preheaters 4, two pairs of these four blast preheaters 4 can be used to perform the operation described above with reference to FIG. 2, or one of the four blast preheaters 4 can be suspended and the operation shown in FIG. 4 can be carried out using three blast heaters 4 . Alternatively, a pair of blow preheaters 4 of these four blow preheaters 4 can be suspended and the remaining pair can be used.

[0066]

In an exemplary embodiment, the 45 minute cycle operation shown in FIG. 2 and the 30 minute cycle operation shown in FIG. 4. However, the cycle time of the operation can be determined as desired, and can be as short as 20 minutes or can be as long as 60 minutes. However, the short cycle time requires frequent stage switching and sometimes becomes inefficient. In contrast, a long cycle time requires a large volume for the preheaters 4 blast. In addition, the range of temperature change in the blast preheater during the blowing operation and the heating operation is sometimes limited. Accordingly, it is desirable to determine the cycle time in accordance with the requirements of the blast preheater system 1.

[0067]

Although an external combustion blast preheater 4 is used in the exemplary embodiment, the blast preheater 4 in some embodiments is an internal combustion unit or a top heated unit. In other words, the present invention is applicable to any type of blast preheater.

Although the fan 52 is used as a blower, in particular a high pressure fan, any other type of blower that is capable of increasing the pressure of the fuel gas passing through the fuel gas supply line 5 can be used.

In some embodiments, a flow meter and a flow controller are provided in the off-gas line leading to the off-gas conduit 44 from each of the blast heaters 4 to adjust the off-gas flow rate to match the amount of fuel gas and air, thereby eliminating the need for operation valve switching during switching between the heating operation and the blowing operation.

INDUSTRIAL APPLICABILITY

[0068]

The present invention is applicable to a blast preheater system(s) and to a method of operating the blast preheater.

LIST OF REFERENCES

[0069]

1 - blast heater system,

2 - blast furnace,

21 - top,

22 - filling equipment,

23 - lance,

24 - ring pipeline,

3 - top gas utilization line,

31 - top gas pipeline,

32 - dust collector,

33 - primary Venturi scrubber,

34 - secondary Venturi scrubber,

35 - turbine system for utilization of top gas pressure,

36 - gas holder,

4, 4A, 4B, 4C - blast heater,

41 - regenerative chamber,

42 - combustion chamber,

43 - cold blast pipeline,

431 - high pressure fan for blowing,

44 - flue gas pipeline,

441 - turbine exhaust gas pressure recovery system,

45 - hot blast pipeline,

46 - air pipeline for combustion,

461 - fan for compressing combustion air,

47 - fuel gas pipeline,

5 - fuel gas supply line,

51, 51P - outlet pipe,

52 - fan (supercharger)

Claims (21)

1. A blast heater system for a blast furnace, comprising: a blast preheater configured to perform a blast operation to supply hot blast to the blast furnace and a heating operation to burn fuel gas in the blast preheater; a fuel gas supply line configured to supply top gas of the blast furnace to the blast preheater as fuel gas; and a blower provided in the fuel gas supply line for pressurizing the fuel gas so that the pressure in the blast preheater during the heating operation is equal to the pressure in the blast preheater during the blast operation. 2. The system according to claim 1, in which the fuel gas supply line takes top gas from the top gas recovery line to remove top gas from the top gas of the blast furnace at a position downstream of the top gas pressure recovery turbine system. 3. The system according to claim 1 or 2, further comprising: an exhaust gas heat recovery system configured to recover the pressure and heat of the exhaust gases exiting the blast preheater during the heating operation so that the blower is driven by the pressure and heat of the exhaust gases recovered by the exhaust gas heat recovery system. 4. A method for preheating a blast for a blast furnace in a preheater configured to perform a blast operation for supplying hot blast to the blast furnace and a heating operation for burning fuel gas in the blast preheater, comprising: supplying blast furnace top gas from the blast furnace to the blast preheater as fuel gas and pressurizing the fuel gas supplied to the blast preheater by the blower so that the pressure in the blast preheater during the heating operation is equal to the pressure in the blast preheater during the blast operation. 5. The method according to claim 4, in which The top gas of the blast furnace, which is drawn off from the top of the blast furnace, and whose pressure is recovered by the turbine top gas pressure recovery system, is used as fuel gas. 6. The method of claim 4, further comprising: utilizing the pressure and heat of the off-gases exiting the blast preheater during the heating operation so that the blower is driven by the reclaimed pressure and heat of the off-gases. 7. The method according to any one of paragraphs. 4-6, further comprising: repeating the cycle of the blowing operation, the blowing-to-heating changeover operation for switching the blowing preheater from the blowing operation to the heating operation, the heating operation and the heating-to-blowing changeover operation for switching the blowing preheater from the heating operation to the blowing operation, in which the total time of the blow-to-heat transfer operation, the heating operation, and the heat-to-blast transfer operation is set to be equal to or less than the duration of the blow operation. 8. The method according to any one of paragraphs. 4-6, further comprising: repeating the cycle of the blowing operation, the blowing-to-heating changeover operation for switching the blowing preheater from the blowing operation to the heating operation, the heating operation and the heating-to-blowing changeover operation for switching the blowing preheater from the heating operation to the blowing operation, in which the total time of the blow-to-heat transfer operation, the heating operation, and the heat-to-blast transfer operation are set to be equal to or less than twice the duration of the blow operation.

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