EP3730631A1

EP3730631A1 - Blast furnace stove device and method for operating blast furnace stove device

Info

Publication number: EP3730631A1
Application number: EP18892629.9A
Authority: EP
Inventors: Kengo Usui; Shoji FURUTACHI
Original assignee: Nippon Steel Engineering Co Ltd; Nippon Steel Plant Designing Corp
Current assignee: Nippon Steel Engineering Co Ltd
Priority date: 2017-12-18
Filing date: 2018-08-31
Publication date: 2020-10-28
Anticipated expiration: 2038-08-31
Also published as: CN111684083A; EP3730631A4; KR102443024B1; JP6954824B2; JP2019108583A; WO2019123727A1; BR112020012112A2; RU2769340C2; BR112020012112B1; EP3730631B1; KR20200096635A; RU2020119665A3; RU2020119665A

Abstract

A hot-blast stove system (1) includes: a hot-blast stove (4) for performing an on-blast operation for delivering a hot blast to a blast furnace (2) and an on-gas operation for combusting a fuel gas in the hot-blast stove; a fuel gas supply line (5) for supplying a BFG produced by the blast furnace (2) to the hot-blast stove (4) as the fuel gas; and a blower (52) provided in the fuel gas supply line (5) and configured to raise a pressure of the BFG. The fuel gas supply line (5) takes out the BFG from a part of a blast-furnace-top-gas recovery line (3) downstream of a top pressure recovery turbine system (35), the blast-furnace-top-gas recovery line (3) being configured to take out the BFG from a furnace top (21) of the blast furnace (2). A power of the blower (52) is supplied from a waste pressure recovery turbine system (441) for recovering a waste pressure and a waste heat from an waste gas of the hot-blast stove (4) during the on-gas operation.

Description

TECHNICAL FIELD

The present invention relates to a hot-blast stove system and a hot-blast-furnace operation method.

BACKGROUND ART

A hot-blast stove has been used for supplying hot blast to an ironmaking blast furnace (see Patent Literature 1).
On-gas operations and on-blast operations are repeated in a hot-blast stove.
During the on-gas operation, a fuel gas and combustion air are supplied from an outside and combusted inside the hot-blast stove to heat heat-storage bricks in the hot-blast stove to a high temperature.
During the on-blast operation, the air-supply direction is reversed from the air-supply direction during the on-gas operation, where the supplied air is heated by the heat-storage bricks to a high temperature to be supplied to a blast furnace.
The hot-blast stove includes a plurality of hot-blast stoves arranged in parallel. When one of the hot-blast stoves is in the on-gas operation, the rest of the hot-blast stoves continues their on-blast operation to avoid interruption of hot-blast supply to the blast furnace.
Typically used fuel gas in the on-gas operation is BFG (Blast Furnace top Gas) of the blast furnace. Combustion waste gas is released to the atmosphere. Accordingly, a furnace pressure in the hot-blast stove (sometimes simply referred to as a "furnace pressure" hereinafter) is slightly higher than the atmospheric pressure.
In contrast, the air introduced into the hot-blast stove is pressurized by a blower or the like during the on-blast operation in order to blow the hot blast into the interior of the high-pressure blast furnace, so that the furnace pressure in the hot-blast stove is equal to or more than the interior pressure of the blast furnace.
In use of the hot-blast stove, the on-gas operation and the on-blast operation are switched at a predetermined interval and the pressure inside the hot-blast stove is adjusted at the time of switching to a level corresponding to respective furnace pressures during the on-gas operation and the on-blast operation.
When the on-gas operation is switched to the on-blast operation, a pressure-equalization operation is performed to introduce the pressurized air into the hot-blast stove to increase the pressure inside the hot-blast stove.
When the on-blast operation is switched to the on-gas operation, a pressure-release operation is performed to gradually exhaust the air inside the hot-blast stove to reduce the pressure inside the hot-blast stove.
The hot-blast stove system disclosed in Patent Literature 1, which increases the pressure of the fuel gas and air supplied during the on-gas operation, provides the following improvements.
Specifically, since the furnace pressure during the on-gas operation is increased with respect to the furnace pressure in a typical furnace (i.e. substantially atmospheric pressure), the volume of the combustion gas and, consequently, the size of the furnace body and accessory equipment, are reducible. Further, the furnace pressure during the on-gas operation is brought close to the furnace pressure during the on-blast operation, so that the pressure difference between the on-gas operation and the on-blast operation and, consequently, the time typically required for the pressure-equalization operation and the pressure-release operation are reducible, leading to energy-saving.
In order to increase the furnace pressure during the on-gas operation, it is specifically disclosed in Patent Literature 1 that the BFG used in the on-gas operation of the hot-blast stove system is taken out from a high-pressure portion of a BFG-recovery line of a blast furnace located upstream of a TRT (Top-pressure Recovery Turbine generating system).

CITATION LIST

PATENT LITERATURE(S)

Patent Literature 1: JP 59-143008 A

SUMMARY OF THE INVENTION

PROBLEM(S) TO BE SOLVED BY THE INVENTION

As described above, the BFG used in the on-gas operation is taken out from the high-pressure portion of the BFG-recovery line of the blast furnace located upstream of the TRT to increase the furnace pressure during the on-gas operation in the hot-blast stove system of Patent Literature 1.
However, the pressure of the BFG (e.g. 280 KPa) taken out from a part of the BFG-recovery line of the blast furnace at an upstream of the TRT is not enough to increase the furnace pressure during the on-gas operation to the furnace pressure during the on-blast operation (e.g. 500 KPa), failing to eliminate the need for the pressure-equalization operation and the pressure-release operation. In other words, though the pressure difference to be adjusted between the pressure-equalization operation and the pressure-release operation can be reduced in Patent Literature 1, the need for performing the pressure-equalization operation and the pressure-release operation still remains, resulting in reduction in working efficiency and failing to improve the operation efficiency.
In addition, the BFG taken out from the part of the BFG-recovery line of the blast furnace at an upstream of the TRT as disclosed in Patent Literature 1 entails the following disadvantages.
The BFG, which is taken out from the part of the BFG-recovery line close to the blast furnace, is susceptible to pressure fluctuation at the furnace top of the blast furnace. Accordingly, the BFG pressure is unstable, destabilizing the on-gas operation of the hot-blast stove.
Further, the BFG, which is high-pressure and thus contains much amount of moisture, may produce mist when being introduced into the hot-blast stove to degrade the firebricks.
An object of the invention is to provide a hot-blast stove system and a hot-blast-furnace operation method capable of sufficiently increasing a furnace pressure during an on-gas operation.

MEANS FOR SOLVING THE PROBLEM(S)

A hot-blast stove system according to an aspect of the invention includes: a hot-blast stove configured to perform an on-blast operation for delivering a hot blast to a blast furnace and an on-gas operation for combusting a fuel gas in the hot-blast stove; a fuel gas supply line configured to supply a blast furnace top gas from the blast furnace to the hot-blast stove as the fuel gas; and a booster provided in the fuel gas supply line to raise a pressure of the fuel gas.
A method of operating a hot-blast stove according to another aspect of the invention is configured to perform an on-blast operation for delivering a hot blast to a blast furnace and an on-gas operation for combusting a fuel gas in the hot-blast stove, the method including: supplying a blast furnace top gas from the blast furnace to the hot-blast stove as the fuel gas; and
raising a pressure of the fuel gas supplied to the hot-blast stove with a booster.
According to the above aspects of the invention, the pressure of the fuel gas supplied to the hot-blast stove is raised by the booster to a sufficiently high level.
Accordingly, the furnace pressure in the hot-blast stove during the on-gas operation can be sufficiently raised to be equal to the furnace pressure during the on-blast operation. Since a furnace pressure difference between the on-gas operation and the on-blast operation is eliminated, the pressure-equalization operation and the pressure-release operation are no more necessary and can be omitted.
The pressure-equalization operation and the pressure-release operation can be totally omitted, so that the work steps for these operation can be cut down, and work efficiency and operation cost can be reduced. Further, the time period occupied by the pressure-equalization operation and the pressure-release operation can be eliminated, so that the operation efficiency can be improved. Furthermore, the number of the hot-blast stoves can be reduced. In addition, condensation of moisture in the BFG remaining in the hot-blast stove, which occurs in a typical pressure-release operation in accordance with decrease in the furnace pressure, can be prevented by omitting the pressure-release operation.
In addition, according to the above aspects of the invention, the temperature of the fuel gas introduced to the hot-blast stove can be raised by an adiabatic compression by the booster. Accordingly, a typically required pre-heater for the fuel gas and a typically required supply of enrichment gas can be omitted, thereby reducing facility and operation cost.
In the above aspects of the invention, the time of the on-gas operation can be shortened by raising the furnace pressure during the on-gas operation. Typically, the time for the on-gas operation is set longer than the on-blast 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 can be omitted in the above aspects of the invention. In addition, the time of the on-gas operation can be shortened substantially to the same time as that of the on-blast operation. Accordingly, the operation schedule can be simply set as a cycle of the on-gas operation and the on-blast operation.
In addition to the above effects, the above aspects of the invention offer effects associated with increasing the pressure of the fuel gas as disclosed in Patent Literature 1.
Specifically, since the difference between the furnace pressure during the on-blast operation and the furnace pressure during the on-gas operation can be reduced and pressure fluctuation during the pressure-equalization operation and the pressure-release operation can be eliminated, the lifetime of the components of the hot-blast stove can be prolonged. Specifically, for instance, fatigue breakdown of an iron shell, cracking of firebricks in the hot-blast stove, and generation of gaps in the brick joint (and consequent blowout of gas in the hot-blast stove through the brick joint) can be prevented.
Further, the volume of the fuel gas can be reduced by raising the furnace pressure during the on-gas operation, so that a cross section of the hot-blast stove can be reduced, combustion efficiency during the on-gas operation can be improved, and the size of the furnace body and facility can be reduced.
In the hot-blast stove system according to the above aspect of the invention, it is preferable that the fuel gas supply line takes out the blast furnace top gas from a blast-furnace-top-gas recovery line for taking out the blast furnace top gas from a furnace top of the blast furnace at a position downstream of a top pressure recovery turbine system.
In the hot-blast-furnace operation method according to the above aspect of the invention, it is preferable that the blast furnace top gas, which is taken out from a furnace top of the blast furnace and whose pressure is recovered by a top pressure recovery turbine system, is used as the fuel gas.
In the above arrangement, the blast furnace top gas, whose pressure is recovered by the top pressure recovery turbine system, is used as the fuel gas, so that the influence of the pressure fluctuation at the furnace top of the blast furnace is moderated by the top pressure recovery turbine system to stabilize the pressure fluctuation of the fuel gas.
In the above arrangement, the blast furnace top gas used as the fuel gas, whose pressure is recovered by the top pressure recovery turbine system and thus is low, contains low amount of moisture, so that, for instance, the firebricks inside the hot-blast stove are kept from being degraded due to mist generated in the hot-blast stove when the blast furnace top gas is introduced as the fuel gas.
In the above arrangement, even when the low-pressure blast furnace top gas is used, the pressure of the fuel gas introduced to the hot-blast stove can be set at a sufficiently high level thanks to the pressure raised by the booster.
In the hot-blast stove system according to the above aspect of the invention, it is preferable that the hot-blast stove system further includes a waste gas heat recovery system configured to recover a waste pressure and a waste heat from a waste gas from the hot-blast stove during the on-gas operation, the booster being powered by the waste pressure and the waste heat recovered by the waste gas heat recovery system.
In the hot-blast-furnace operation method according to the above aspect of the invention, it is preferable that the method further includes recovering a waste pressure and a waste heat from a waste gas from the hot-blast stove during the on-gas operation, the booster being powered by the recovered waste pressure and waste heat.
In the above arrangement, the booster can be powered by the waste pressure and waste heat recovered from the waste gas during the on-gas operation of the hot-blast stove, so that the operation cost can be reduced. The booster of the above aspects of the invention, whose advantages have been described above, can be powered by the waste energy of the hot-blast stove during the on-gas operation, so that the cost required for implementing the invention can be minimized.
In the hot-blast-furnace operation method according to the above aspect of the invention, it is preferable that the method further includes repeating a cycle of the on-blast operation, a blast-to-combustion operation for switching an operation of the hot-blast stove from the on-blast operation to the on-gas operation, the on-gas operation, and a combustion-to-blast operation for switching the operation of the hot-blast stove from the on-gas operation to the on-blast operation, where a total time of the blast-to-combustion operation, the on-gas operation and the combustion-to-blast operation is set to be equal to or less than a time for the on-blast operation.
In the above arrangement, for instance, two hot-blast stoves are used for operation in an alternate manner, where, while the on-blast operation is performed by one of the two hot-blast stoves, the blast-to-combustion operation, the on-gas operation, and the combustion-to-blast operation are performed by the other of the hot-blast stoves.
In the above aspects of the invention, the blast-to-combustion operation and the combustion-to-blast operation, which do not include pressure adjustment (i.e. pressure equalization and pressure release), only require switching of the combustion gas and blasting air and can be performed within an extremely short time.
Further, the on-gas operation of the invention, which is performed under a high pressure, can provide sufficient heat storage within substantially the same time period as that for the on-blast operation.
Consequently, while the on-blast operation is performed by one of the two hot-blast stoves, the on-gas operation sandwiched between the blast-to-combustion operation and the combustion-to-blast operation can be performed by the other of the two hot-blast stoves, thus allowing the two hot-blast stoves to perform the same on-blast operation as typical on-blast operation performed by three hot-blast stoves. At this time, the hot blast can be delivered to the blast furnace without interruption through the on-blast operation, which is alternately performed by the two hot-blast stoves.
It should be noted that the invention is applicable to any two of hot-blast stoves in a hot-blast stove system having an even number of hot-blast stoves.
In the hot-blast-furnace operation method according to the above aspect of the invention, it is preferable that the method further includes repeating a cycle of the on-blast operation, a blast-to-combustion operation for switching an operation of the hot-blast stove from the on-blast operation to the on-gas operation, the on-gas operation, and a combustion-to-blast operation for switching the operation of the hot-blast stove from the on-gas operation to the on-blast operation, where a total time of the blast-to-combustion operation, the on-gas operation and the combustion-to-blast operation is set to be equal to or less than twice of a time for the on-blast operation.
In the above arrangement, when, for instance, three hot-blast stoves are used for operation, while the on-blast operation is performed by one of the three hot-blast stoves, the blast-to-combustion operation, the on-gas operation, and the combustion-to-blast operation are performed by the other two of the hot-blast stoves.
Specifically, the operation of the first hot-blast stove performing the on-blast operation is switched to the on-gas operation and the on-blast operation is performed by the second hot-blast stove. After an elapse of a predetermined on-blast operation time, the operation of the second hot-blast stove is switched from the on-blast operation to the on-gas operation and the on-blast operation is performed by the third hot-blast stove. At this time, the on-gas operation by the first hot-blast stove is half-finished. After an elapse of a predetermined on-blast operation time, the operation of the third hot-blast stove is switched from the on-blast operation to the on-gas operation and the on-blast operation is performed by the first hot-blast stove.
Consequently, while the on-blast operation is performed by one of the three hot-blast stoves, the on-gas operation sandwiched between the blast-to-combustion operation and the combustion-to-blast operation can be performed by the other two of the three hot-blast stoves, thus allowing efficient operation by the three hot-blast stoves. At this time, the hot blast can be delivered to the blast furnace without interruption through the on-blast operation, which is alternately performed by the one of the three hot-blast stoves.
Further, in the above arrangement, the duration of the on-gas operation is approximately twice as long as the duration of the on-blast operation. Accordingly, the duration of the on-blast operation may be shortened to reduce the decrease in the stored heat temperature. Further, the size of the combustion chamber for the combustion can be reduced.
It should be noted that the invention is applicable to any combination of three hot-blast stoves in a hot-blast stove system having three multiples of hot-blast stoves.
When the three hot-blast stove are used, the on-blast operation may be performed by two hot-blast stoves while the on-gas operation is performed by one hot-blast stove. The two hot-blast stoves may perform the on-blast operation so that the on-blast operation is initially performed only by a first one of the two hot-blast stoves and, after the on-blast operation performed by the first one of the two hot-blast stoves is half-finished, the second one of the hot-blast stoves may start the on-blast operation, whereby the temperature of the hot blast to the blast furnace can be raised as compared with the temperature by the above-described alternate operation by the two or an even number of hot-blast stoves.
According to the above aspects of the invention, a hot-blast stove system and a hot-blast-furnace operation method capable of sufficiently raising the furnace pressure during the on-gas operation can be provided.

BRIEF DESCRIPTION OF DRAWING(S)

Fig. 1 schematically shows a hot-blast stove system according to an exemplary embodiment of the invention.
Fig. 2 is a schematic diagram showing an on-blast operation and an on-gas operation according to the exemplary embodiment.
Fig. 3 is a schematic diagram showing an on-blast operation and an on-gas operation according to a typical hot-blast stove system.
Fig. 4 is a schematic diagram showing an on-blast operation and an on-gas operation according to a modification of the exemplary embodiment.

DESCRIPTION OF EMBODIMENT(S)

As shown in Fig. 1, a hot-blast stove system 1 is configured to supply hot blast to a blast furnace 2.
The blast furnace 2 includes a furnace top 21 and a charging equipment 22 provided at the furnace top 21 and configured to charge raw materials mainly in a form of iron ore and coke. The blast furnace 2 includes a plurality of tuyeres 23 circumferentially arranged on a furnace body. The hot-blast stove system 1 is connected to each of the tuyeres 23 via a bustle main 24.
The hot blast, which is supplied from the hot-blast stove system 1, is distributed in the bustle main 24 to be evenly blown into hot-blast stoves through the tuyeres 23. After having been blown into the hot-blast stove to heat the raw materials and contribute to reduction reaction of iron component, the hot blast is taken out through the furnace top 21 in a form of BFG (Blast Furnace top Gas).
A blast-furnace-top-gas recovery line 3 for recovering the blast furnace top gas is connected to the blast furnace 2.
The blast-furnace-top-gas recovery line 3 includes a furnace top gas duct 31 connected to the furnace top 21 and configured to take out the BFG, and a dust catcher 32, a primary venturi scrubber 33, and a secondary venturi scrubber 34, though which the BFG is sequentially passed to be removed with dust therefrom.
Residual energy (e.g. pressure and heat) of the dust-removed BFG is recovered by a top pressure recovery turbine system 35 (i.e. TRT) to be recycled after being converted into electricity or the like.
The BFG whose energy has been recovered is stored in a gas holder 36 for use as a fuel for other equipment or the like.
The hot-blast stove system 1 includes three hot-blast stoves 4 (4A to 4C). The hot-blast stoves 4A to 4C are external-combustion type hot-blast stoves each including a checker chamber 41 and a combustion chamber 42.
The checker chamber 41 includes an interior portion lined with heat-storage checker bricks, a furnace top portion in communication with the combustion chamber 42, and a bottom portion connected with an cold-blast main 43 and a waste gas main 44.
The combustion chamber 42 includes a middle portion connected with a hot-blast main 45 extending to the bustle main 24, and a bottom portion provided with a burner unit connected with an combustion air main 46 and a fuel gas main 47.
The hot-blast stoves 4A to 4C each include on-off valves (not shown) at respective connecting portions with the cold-blast main 43, the waste gas main 44, and the hot-blast main 45, the on-off valves being configured to connect/disconnect respective pipes to/from the hot-blast stoves 4A to 4C depending on the operations of the hot-blast stoves 4A to 4C.
The on-blast operation for supplying the hot blast to the blast furnace 2 and a heat-storage operation for storing heat are alternately performed in the hot-blast stove 4A to 4C.
During the on-blast operation, air introduced through the cold-blast main 43 passes through the checker chamber 41 to be heated to turn into the hot blast, which is supplied from the combustion chamber 42 through the hot-blast main 45 to the bustle main 24.
During the on-gas operation, the air from the combustion air main 46 and the fuel gas from the fuel gas main 47 are burnt in the combustion chamber 42 by the burner unit, so that a high-temperature combustion gas is passed through the checker chamber 41 to store heat in the checker bricks. The combustion gas having passed through the checker chamber 41 is discharged through the waste gas main 44.
Mutual collaboration of the three hot-blast stoves 4A to 4C during the on-blast operation and the on-gas operation will be detailed later.
The cold-blast main 43, which is provided with a blasting blower 431, is configured to raise a pressure of sucked air to a predetermined pressure and deliver the air to the checker chamber 41 or the hot-blast main 45. The blower 431 keeps the furnace pressure in the checker chamber 41 and the combustion chamber 42 during the on-blast operation at a predetermined high pressure to allow the hot blast to be blown through the tuyeres 23 even when an inner pressure of the blast furnace 2 is high.
The waste gas main 44 is provided with a waste pressure recovery turbine system 441 (e.g. turbine generator) for recovering the residual energy (e.g. pressure and heat) of the combustion gas discharged through the waste gas main 44.
The combustion air main 46 is provided with an air-supply blower 461 configured to pressure-feed external air to the combustion chamber 42 during the on-gas operation.
The fuel gas main 47 is connected to the blast-furnace-top-gas recovery line 3 through a fuel gas supply line 5 to allow the recovered BFG from the blast furnace 2 to be used as the fuel gas for the combustion chamber 42.
The fuel gas supply line 5, which includes a branch duct 51 connected to a downstream of the top pressure recovery turbine system 35 of the blast-furnace-top-gas recovery line 3, is configured to supply the BFG taken out from the connected portion to the hot-blast stove 4.
A blower 52 (booster of the invention) is provided to a part of the fuel gas supply line 5. The BFG, which is delivered through the fuel gas supply line 5 to the combustion chamber 42 and pressure-raised by the blower 52 to a predetermined pressure, can keep the furnace pressure in the combustion chamber 42 and the checker chamber 41 during the on-gas operation at a predetermined high-pressure.
The booster in a form of the blower 52 is powered by the energy recovered by the waste pressure recovery turbine system 441 provided in the waste gas main 44. For instance, when the on-gas operation is performed in one of the hot-blast stoves 4A to 4C, the power for the blower 52 to raise the pressure of the BFG can be provided by the energy recovered from at least one of the hot-blast stove 4A to 4C during the on-gas operation.
When the pressure is raised by the blower 52 to increase the pressure of the fuel gas (BFG) supplied from the fuel gas main 47 to the combustion chamber 42, the pressure of the air supplied from the combustion air main 46 to the combustion chamber 42 has to be raised for combustion balancing. The pressure of the air can be raised by the blower 461. It should be noted that the blower 461 can also be powered by the energy recovered by the waste pressure recovery turbine system 441. Further, the air-supply blower 461 may be substituted by the blasting blower 431 when the blower 431 can provide an extra air volume.
In the hot-blast stove system 1 of the exemplary embodiment, two of the three hot-blast stoves 4A to 4C are used to alternately perform the on-blast operation and the on-gas operation in each of the hot-blast stoves.
As shown in Fig. 2, when the two hot- blast stoves 4A, 4B are used, the on-blast operation and the on-gas operation are alternately performed at, for instance, 45-minute cycles from a reference point (0 minutes).
In the hot-blast stove 4A, the on-blast operation is performed for 45 minutes from the reference point (0 minutes), a switching operation from the on-blast operation to the on-gas operation (blast-to-combustion operation) is performed for 0.5 minutes, the on-gas operation is performed for 44 minutes, and a switching operation from the on-gas operation to the on-blast operation (combustion-to-blast operation) is performed for 0.5 minutes. The cycle of these four steps is repeated thereafter.
The on-blast operation, which lasts for 45 minutes, accounts for one cycle. The on-gas operation lasting for 44 minutes and the two switching operations between combustion and blasting, which each take 0.5 minutes, accounts for 45 minutes (i.e. one cycle) in total.
The furnace pressure in the hot-blast stove 4A is kept at a predetermined level during the on-blast operation by the pressure of the blasting air raised by the blower 431 of the cold-blast main 43. In contrast, during the on-gas operation, the pressure of the BFG (fuel gas) is raised by the blower 52 of the fuel gas supply line 5, so that the furnace pressure is kept at the same level as that during the on-blast operation.
During the blast-to-combustion operation and the combustion-to-blast operation, in order to reverse the air flow direction, a switching time for driving the on-off valves (not shown) provided to each of connecting portions of the cold-blast main 43, the waste gas main 44 and the hot-blast main 45 of the hot-blast stoves 4A to 4C is required.
The furnace temperature in the hot-blast stove 4A declines during the on-blast operation in accordance with the volume of outputted hot blast. In contrast, the furnace temperature gradually rises during the on-gas operation due to the progress in combustion in the combustion chamber 42, reaching to a temperature required at the start of the on-blast operation.
Sufficient heat can be stored in such a short-time on-gas operation because the pressure of the BFG (fuel gas) is raised by the blower 52 (booster) to allow the on-gas operation in the combustion chamber 42 to be performed at a high pressure.
In contrast to the above-described hot-blast stove 4A, in the hot-blast stove 4B, the blast-to-combustion operation is performed for 0.5 minutes from the reference point (0 minutes), the on-gas operation is performed for 44 minutes, the combustion-to-blast operation is performed for 0.5 minutes, and the on-blast operation is performed for 45 minutes. The cycle of these four steps is repeated thereafter.
Also in the hot-blast furnace 4B, the on-blast operation (45 minutes) accounts for one cycle, and the on-gas operation (44 minutes) and the blast-to-combustion and combustion-to-blast operations (each 0.5 minutes) accounts for 45 minutes in total (i.e. one cycle)
The pressure and temperature changes during the on-blast operation and the on-gas operation in the hot-blast stove 4B show the same behavior as those described for the hot-blast stove 4A.
As described above, the hot- blast stoves 4A, 4B can alternately perform the on-blast operation and the on-gas operation at the 45-minute cycle in the exemplary embodiment, as shown in Fig. 2.
The on-blast operation lasts entirely during the 45-minute cycle in the hot- blast stoves 4A, 4B. Accordingly, the hot blast is delivered to the blast furnace 2 without interruption. In contrast, the on-gas operation, which is performed under a high pressure, allows desired heat storage in 44 minutes. Thus, the on-gas operation as well as the blast-to-combustion operation and the combustion-to-blast operation can be performed in the 45-minute cycle, so that the alternate blasting and combustion operations in 45-minute cycle can be achieved with the two hot- blast stoves 4A, 4B.
For the operation as shown in Fig. 2, a combination of the hot- blast stoves 4A, 4C or the hot- blast stove 4B, 4C may be used instead of the combination of the hot- blast stoves 4A, 4B.
In the hot-blast stove system 1 of the exemplary embodiment, typical on-blast and on-gas operations can be performed with three hot-blast stoves 4A to 4C by performing the on-gas operation at an ambient pressure without using the blower 52 (booster).
As shown in Fig. 3, when the on-gas operation is performed at an ambient pressure using the three hot-blast stoves 4A to 4C, the on-blast operation and the on-gas operation are alternately performed at, for instance, 45-minute cycles from a reference point (0 minutes).
However, though the on-blast operation is performed for one cycle (i.e. 45 minutes), the on-gas operation is performed for two cycles (i.e. 90 minutes) because temperature-raising process requires much time. Further, during the two cycles (90 minutes), 7.5-minute pressure-release operation for reducing the high pressure during the on-blast operation to the ambient pressure during the on-gas operation and 7.5-minute pressure-equalization operation for raising the ambient pressure during the on-gas operation to the high pressure during the on-blast operation are performed before and after the 75-minute on-gas operation.
As shown in Fig. 3, in each of the hot-blast stoves 4A to 4C, the 7.5-minute pressure-release operation, the 75-minute on-gas operation, and the 7.5-minute pressure-equalization operation, which account for 90 minutes in total (i.e. for two cycles), are performed after the above-described 45 minutes on-blast operation (i.e. one cycle). The cycle of these steps is repeated thereafter.
At this time, the operations in the hot-blast stoves 4A to 4C are mutually offset by one cycle, so that the hot blast is supplied to the blast furnace 2 without interruption. In other words, the on-blast operation of the hot-blast stove 4A is followed by the on-blast operation of the hot-blast stove 4B, which is further followed by the on-blast operation of the hot-blast stove 4C, and then the on-blast operation of the hot-blast stove 4A is again performed. Through the repetition of the operations, the on-blast operation is constantly performed by one of the hot-blast stoves 4A to 4C.
As described above, in the typical on-blast operation and on-gas operation shown in Fig. 3, the hot-blast stoves 4A to 4C, which perform the on-gas operation under an ambient pressure, requires much time for the on-gas operation and, consequently, simultaneous operation of the three hot-blast stoves 4A to 4C in order to achieve the desired heat storage. Further, in order to compensate for the furnace pressure difference between the on-gas operation and the on-blast operation, the pressure-equalization operation and the pressure-release operation are necessary, resulting in complicated operation procedures.
As described above, the hot-blast stove system 1 according to the exemplary embodiment offers the following advantages, especially by performing the operation shown in Fig. 2.
In the exemplary embodiment, the pressure of the fuel gas (BFG) supplied to the hot-blast stove 4 (4A to 4C) is raised by the blower 52 (booster) to a sufficiently high level.
Accordingly, the furnace pressure in the hot-blast stove 4 during the on-gas operation can be sufficiently raised to be equal to the furnace pressure during the on-blast operation (see Fig. 2). Since the furnace pressure difference between the on-gas operation and the on-blast operation is eliminated, the pressure-equalization operation and the pressure-release operation (see Fig. 3) are no more necessary and can be omitted.
In the exemplary embodiment, the on-blast operation and the on-gas operation of the hot-blast stove 4 are performed as shown in Fig. 2, so that the pressure-equalization operation and the pressure-release operation as shown in Fig. 3 can be totally omitted, thereby reducing the work steps, work efficiency and operation cost.
Further, according to the operation of the hot-blast stove 4 as 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 operation efficiency can be improved.
Further, the operation of the hot-blast stove 4 shown in Fig. 2 requires only two of the hot-blast stoves 4A to 4C, where one of the hot-blast stoves 4A to 4C can be suspended or may be subjected to maintenance.
In order to solely perform the operation shown in Fig. 2, only two hot-blast stoves 4 may be provided in the hot-blast stove system 1 (i.e. the number of the hot-blast stoves can be reduced).
When the typical operation as shown in Fig. 3 is performed, moisture in the BFG remaining inside the hot-blast stove 4 is condensed at the time of the pressure-equalization operation in accordance with the increase in the furnace pressure in the hot-blast stove. However, the operation shown in Fig. 2 does not require the pressure-equalization operation and thus the moisture condensation in the hot-blast stove can be prevented.
Further, the temperature of the fuel gas introduced to the hot-blast stove 4 can be raised by adiabatic compression by the blower 52 (booster of the invention) and the air-supply blower 461 for raising the pressure of the air, in the exemplary embodiment. Accordingly, a pre-heater for the fuel gas used in the typical hot-blast stove system and a supply of a typically required enrichment gas can be omitted, thereby reducing facility and operation cost.
In the exemplary embodiment, the time of the on-gas operation can be shortened by raising the furnace pressure during the on-gas operation as described in the explanation of Fig. 2. Typically, the time for the on-gas operation is set longer than the on-blast 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 can be omitted in the exemplary embodiment. In addition, the time of the on-gas operation can be shortened substantially to the same time as that of the on-blast operation. Accordingly, the operation schedule can be simply set as a cycle of the on-gas operation and the on-blast operation.
Further, in the exemplary embodiment, since the difference between the furnace pressure during the on-blast operation and the furnace pressure during the on-gas operation and, consequently, pressure change during the pressure-equalization operation and the pressure-release operation (see Fig. 3) can be eliminated, the lifetime of the components of the hot-blast stove 4 can be prolonged. Specifically, for instance, fatigue breakdown of an iron shell, cracking of firebricks in the hot-blast stove, and generation of gaps in the brick joint (and consequent blowout of gas in the hot-blast stove through the brick joint) can be prevented.
Further, the volume of the fuel gas can be reduced by raising the furnace pressure during the on-gas operation, so that a cross section of the hot-blast stove can be reduced, combustion efficiency during the on-gas operation can be improved, and the size of the furnace body and facility can be reduced.
In the exemplary embodiment, the fuel gas of the hot-blast stove 4 is provided by the BFG (Blast Furnace top Gas) recovered through the blast-furnace-top-gas recovery line 3 from the furnace top 21 of the blast furnace 2, where the BFG is taken out from a part of the blast-furnace-top-gas recovery line 3 downstream of the top pressure recovery turbine system 35 through the branch duct 51 of the fuel gas supply line 5.
Accordingly, the BFG whose pressure is recovered by the top pressure recovery turbine system 35 is used as the fuel gas, so that the influence of the pressure fluctuation at the furnace top 21 of the blast furnace 2 is moderated by the top pressure recovery turbine system 35 to stabilize the pressure fluctuation of the BFG supplied to the burner unit of the hot-blast stove 4.
Further, the BFG used as the fuel gas, whose pressure is recovered by the top pressure recovery turbine system 35 and thus is low, contains low amount of moisture, so that, for instance, the firebricks inside the hot-blast stove 4 are kept from being degraded due to mist generated in the hot-blast stove when the BFG is introduced to the burner unit of the hot-blast stove 4.
In comparison, when the BFG is taken out from a part of the blast-furnace-top-gas recovery line 3 upstream of the top pressure recovery turbine system 35 as in the above-described Patent Literature 1 (see branch duct 51P in Fig. 1), the BFG, which is supplied during the on-gas operation of the hot-blast stove 4, may be influenced by the pressure fluctuation in the furnace top 21 of the blast furnace 2 and contains larger amount of moisture due to the higher pressure than that in the above arrangement, so that mist may be generated inside the hot-blast stove 4 when the BFG is introduced to the burner unit of the hot-blast stove 4, possibly degrading the firebricks.
However, since the BFG is taken out from a part of the blast-furnace-top-gas recovery line 3 downstream of the top pressure recovery turbine system 35 in the exemplary embodiment, these disadvantages can be avoided.
In the exemplary embodiment, the blower 52 (booster) provided to the fuel gas supply line 5 is configured to raise the pressure of the BFG supplied to the hot-blast stove 4.
Accordingly, even when the low-pressure BFG whose pressure has been recovered by the top pressure recovery turbine system 35 is used, the pressure of the BFG introduced to the hot-blast stove 4 can be set at a sufficiently high level.
In the exemplary embodiment, the waste pressure recovery turbine system 441 provided to the waste gas main 44 recovers waste pressure and waste heat of the waste gas of the hot-blast stove 4, the energy of the recovered waste pressure and waste heat being used to power the blower 52 (booster) and the blower 461 of the combustion air main 46. Accordingly, the blowers 52, 461 can be powered by the recovered energy from the waste gas of the hot-blast stove 4 during the on-gas operation, so that the operation cost can be reduced.
Accordingly, the blower 52 configured to raise the pressure during the on-gas operation, whose advantages have been described above, can be powered by the waste energy of the hot-blast stove 4 during the on-gas operation in the exemplary embodiment, so that the cost required for the operation can be minimized.
In the above-described Fig. 2, the operations of the two hot-blast stoves 4 of the hot-blast stove system 1 of the exemplary embodiment are switched per 45-minute cycle. In contrast, the operations of three hot-blast stoves 4 of the same hot-blast stove system 1 may be switched per 30-minute cycle.
As shown in Fig. 4, the three hot-blast stoves 4A to 4C alternately perform the on-blast operation and the on-gas operation at, for instance, 30-minute cycles from the reference point (0 minutes).
In the hot-blast stove 4A, the on-blast operation is performed for 30 minutes from the reference point (0 minutes), a switching operation from the on-blast operation to the on-gas operation (blast-to-combustion operation) is performed for 0.5 minutes, the on-gas operation is performed for 59 minutes, and a switching operation from the on-gas operation to the on-blast operation (combustion-to-blast operation) is performed for 0.5 minutes. The cycle of these four steps is repeated thereafter.
The on-blast operation, which lasts for 30 minutes, accounts for one cycle. The on-gas operation, which lasts for 59 minutes, and the two switching operations between combustion and blasting, which each take 0.5 minutes, accounts for 60 minutes (i.e. two cycles).
The furnace pressure in the hot-blast stove 4A is the same as that for the above-described Fig. 2.
Specifically, the predetermined furnace pressure is kept in the hot-blast stove 4A during the on-blast operation by the pressure of the blasting air raised by the blower 431 of the cold-blast main 43. In contrast, during the on-gas operation, the pressure of the BFG (fuel gas) is raised by the blower 52 of the fuel gas supply line 5, so that the furnace pressure is kept at the same level as that in the on-blast operation.
During the blast-to-combustion operation and the combustion-to-blast operation, in order to reverse the air flow direction, a switching time for driving the on-off valves (not shown) provided to each of connecting portions of the cold-blast main 43, the waste gas main 44 and the hot-blast main 45 of the hot-blast stoves 4A to 4C is required.
The furnace temperature in the hot-blast stove 4A declines during the on-blast operation in accordance with the volume of outputted hot blast. However, due to the short on-blast operation time, the temperature at the end of the on-blast operation is kept higher than the temperature at the end of the on-blast operation as described above with reference to Fig. 2.
In contrast, the furnace temperature gradually rises during the on-gas operation due to the combustion in the combustion chamber 42, reaching to a temperature required at the start of the on-blast operation. However, in addition to the above-described small reduction in temperature during the on-blast operation, since approximately two-cycle time (59 minutes) is ensured for the on-gas operation, the furnace temperature may be raised more gradually than that in the on-gas operation (29 minutes) shown in Fig. 2, so that the on-gas operation may be performed at a lower combustion temperature and/or with smaller consumption of the fuel gas. Further, the size of the combustion chamber 42 for the combustion can be reduced.
In contrast to the above-described hot-blast stove 4A, the hot-blast stove 4B performs, from the reference point (0 minutes), a later half of the on-gas operation and 0.5-minute combustion-to-blast operation, followed by 30 minutes on-blast operation, 0.5-minute blast-to-combustion operation, 59-minute on-gas operation, and 0.5-minute combustion-to-blast operation. These steps are repeated thereafter.
The hot-blast stove 4C performs, from the reference point (0 minutes), 0.5-minute blast-to-combustion operation, 59-minute on-gas operation, 0.5-minute combustion-to-blast operation, and 30-minute on-blast operation. These steps are repeated thereafter.
As described above, the hot-blast stoves 4A to 4C can sequentially perform the on-blast operation and the on-gas operation at the 30-minute cycle in the exemplary operation shown in Fig. 4. Further, the hot-blast stoves 4A to 4C each perform the on-blast operation for 30 minutes in relays, so that the hot blast can be supplied to the blast furnace 2 without interruption.
In addition, the pressure-equalization operation and the pressure-release operation (see Fig. 3) are not necessary and omittable and, consequently, above-described disadvantages associated with the pressure fluctuation during the pressure-equalization operation and the pressure-release operation (e.g. influence on machinery and moisture condensation) can be eliminated. When two hot-blast stoves are used to perform the on-blast operation, the blast temperature can be raised as compared with the on-blast operation using a single hot-blast stove.
The invention is not limited to the above-described exemplary embodiments but includes modifications and the like as long as the modifications and the like are compatible with the invention.
For instance, the number of the hot-blast stoves 4 provided in the hot-blast stove system 1 is not necessarily three, but may be two (capable of performing the operation shown in Fig. 2), or four or more (capable of performing the operation shown in Fig. 2 or the operation shown in Fig. 4). For instance, when there are four hot-blast stoves 4, two pairs out of the four hot-blast stoves 4 may be used to perform the operation above-described with reference to Fig. 2, or one of the four hot-blast stoves 4 may be suspended and the operation shown in Fig. 4 may be performed with the three of the hot-blast stoves 4. Alternatively, a pair of hot-blast stoves 4 out of the four hot-blast stoves 4 may be suspended and a remaining pair out of the four hot-blast stoves 4 may be in operation.
In the exemplary embodiment, the 45-minute cycle operation as shown in Fig. 2 and the 30-minute cycle operation as shown in Fig. 4 have been described. However, the cycle time of the operation may be determined as desired, where the cycle time may be as short as 20 minutes or may be as long as 60 minutes. However, the short cycle time requires frequent switching of the steps and is sometimes inefficient. In contrast, the long cycle time requires a large volume for the hot-blast stove 4. Further, a variable range for the temperature in the hot-blast stove during the on-blast operation and the on-gas operation is sometimes limited. Accordingly, the cycle time is desirably determined in accordance with requirements for the hot-blast stove system 1.
Though the external-combustion hot-blast stove 4 is used in the exemplary embodiment, the hot-blast stove 4 is an internal-combustion type hot-blast stove or a top-combustion type hot-blast stove in some embodiments. In other words, the present invention is applicable to any type of the hot-blast stove.
Though the blower 52 is used as the booster, any other type of booster that is capable of raising the pressure of the fuel gas passing through the fuel gas supply line 5 is usable.
In some embodiments, a flowmeter and a flow regulator are provided in a waste-gas line reaching the waste gas main 44 of each of the hot-blast stoves 4 to regulate the flow rate of the waste gas to correspond to the amount of the fuel gas and the air, thereby eliminating the need for the switching operation of the valve at the time of switching the on-gas operation and the on-blast operation.

INDUSTRIAL APPLICABILITY

The invention is applicable to a hot-blast stove system and a hot-blast-furnace operation method.

EXPLANATION OF CODE(S)

1... hot-blast stove system, 2... blast furnace, 21... furnace top, 22... charging equipment, 23...tuyere, 24... bustle main, 3... blast-furnace-top-gas recovery line, 31... furnace top gas duct, 32... dust catcher, 33... primary venturi scrubber, 34... secondary venturi scrubber, 35...top pressure recovery turbine system, 36...gas holder, 4, 4A, 4B, 4C...hot-blast stove, 41...checker chamber, 42...combustion chamber, 43...cold-blast main, 431...blasting blower, 44...waste gas main, 441...waste pressure recovery turbine system, 45...hot-blast main, 46...combustion air main, 461...combustion-air pressurizing blower, 47...fuel gas main, 5...fuel gas supply line, 51, 51P...branch duct, 52...blower (booster)

Claims

A hot-blast stove system comprising:
a hot-blast stove configured to perform an on-blast operation for delivering a hot blast to a blast furnace and an on-gas operation for combusting a fuel gas in the hot-blast stove;

a fuel gas supply line configured to supply a blast furnace top gas from the blast furnace to the hot-blast stove as the fuel gas; and

a booster provided in the fuel gas supply line to raise a pressure of the fuel gas.
The hot-blast stove system according to claim 1, wherein
the fuel gas supply line takes out the blast furnace top gas from a blast-furnace-top-gas recovery line for taking out the blast furnace top gas from a furnace top of the blast furnace at a position downstream of a top pressure recovery turbine system.
The hot-blast stove system according to claim 1 or 2, further comprising:
a waste gas heat recovery system configured to recover a waste pressure and a waste heat from a waste gas from the hot-blast stove during the on-gas operation, the booster being powered by the waste pressure and the waste heat recovered by the waste gas heat recovery system.
A method of operating a hot-blast stove configured to perform an on-blast operation for delivering a hot blast to a blast furnace and an on-gas operation for combusting a fuel gas in the hot-blast stove, the method comprising:
supplying a blast furnace top gas from the blast furnace to the hot-blast stove as the fuel gas; and

raising a pressure of the fuel gas supplied to the hot-blast stove with a booster.
The method according to claim 4, wherein
the blast furnace top gas, which is taken out from a furnace top of the blast furnace and whose pressure is recovered by a top pressure recovery turbine system, is used as the fuel gas.
The method according to claim 4 or 5, further comprising:
recovering a waste pressure and a waste heat from a waste gas from the hot-blast stove during the on-gas operation, the booster being powered by the recovered waste pressure and waste heat.
The method according to any one of claims 4 to 6, further comprising:
repeating a cycle of the on-blast operation, a blast-to-combustion operation for switching an operation of the hot-blast stove from the on-blast operation to the on-gas operation, the on-gas operation, and a combustion-to-blast operation for switching the operation of the hot-blast stove from the on-gas operation to the on-blast operation, wherein

a total time of the blast-to-combustion operation, the on-gas operation and the combustion-to-blast operation is set to be equal to or less than a time for the on-blast operation.
The method according to any one of claims 4 to 6, further comprising:
repeating a cycle of the on-blast operation, a blast-to-combustion operation for switching an operation of the hot-blast stove from the on-blast operation to the on-gas operation, the on-gas operation, and a combustion-to-blast operation for switching the operation of the hot-blast stove from the on-gas operation to the on-blast operation, wherein

a total time of the blast-to-combustion operation, the on-gas operation and the combustion-to-blast operation is set to be equal to or less than twice of a time for the on-blast operation.