JP3491441B2 - Non-oxidizing heat retention method for tundish - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] The present invention relates to continuous casting (hereinafter referred to simply as "casting").
To a continuous casting)
To keep the tundish in a non-oxidized state
It is about the method. [0002] 2. Description of the Related Art Molten steel is received from a ladle and distributed to a mold.
Tundish itself has no heating element
Before use, heat it separately with a heating means and cast it.
It is necessary to secure a temperature that can be controlled. In addition, multiple
Continuous casting while changing dishes
In the case where the steel type is changed, for example,
When it's time to replace it with a waiting tundish,
What was used up to that point will wait until the next reuse.
There is a usage of tundish such as making
In this way, the number of waiting tundishes
Both are heated to a temperature at which they can be cast before use
Is required. [0003] In such a case where the tundish is heated,
Conventionally, it is usually installed on a tundish preheating cover.
This gas burner is used as a heating means.
In addition, fuel gas such as coke gas and its theoretical
A mixture of 110-120% of the required amount of combustion air
The gas is burned in the gas burner and
Heat the inside of the dish to 1200-1300 ° C
I'm trying. However, in this case, a high-temperature tandis
A large amount of O_TwoIs used, the previous use (previous channel)
The residual steel / residue caused by acidification during preheating at the next charge
FeO and Fe_ThreeO_FourIs produced.
The O component of the generated and remaining iron oxide is used at the next charge.
Reacts with Al in the steel_TwoO_ThreeIs generated.
As a result, hard Al_TwoO_ThreeIs hot scab
・ It may cause quality defects such as blisters. [0005] Such a so-called FeO pickup is suppressed.
There is a demand for the establishment of technologies to prevent
A plan has been made. As an example, see, for example,
Japanese Patent No. 22567 discloses fuel supplied to a preheating gas burner.
The amount of burning air is set to 70 times the theoretical required amount of the supplied fuel gas.
By setting it to 100%, the atmosphere in the tundish
Lowers oxygen concentration to prevent oxidation of residual steel
A tundish preheating method is disclosed. [0006] Japanese Patent Application Laid-Open No. 2-37949 discloses that
With the end of preheating in the tundish as described above, fuel
Stop supplying gas and combustion air and at the same time inert gas
These residual components remaining in the burner with Ar
And purging out the residue of flue gas and
If necessary, fuel gas and combustion air can be
Combustion and A in the tundish in a short time
to prevent oxidation of residual steel by purging with
A gas displacement technique in a dish is disclosed. [0007] SUMMARY OF THE INVENTION
JP-A-4-22567, JP-A-2-37949
The method of heating the tundish described in the report is
Both can be cast when using tundish
Fuel mixed with air as a means to heat
Gas is burned in the tundish and the inner wall is
Assuming that heat is kept or heated to 1200 to 1300 ° C
are doing. Here, for example, Japanese Unexamined Patent Publication No. Hei.
In the official gazette, the supply amount of the combustion air is set to 70% of the supply amount of the fuel gas.
Up to 100%, but under such high temperatures
Is the remaining O_TwoIn addition to the components,
CO which is an oxidizing component_TwoAnd H_TwoO component of O combines with residual steel
Iron oxide is generated, and the oxidation of the remaining steel itself
There is a problem that it cannot be sufficiently suppressed. In order to suppress this as much as possible, Japanese Patent Application Laid-Open No.
How to heat a tundish described in 37949
According to the method, after the preheating is completed, the inert gas Ar
Into the tundish to remove fuel gas and residual oxygen.
Is purged, thereby replacing the atmosphere with a non-oxidizing atmosphere.
Is taking the method. However, even if inert gas is purged
Required from the end of the preheating to the completion of gas replacement
Even if the time can be shortened somewhat, this inert gas
Purging lowers the temperature of the inner wall of the tundish, resulting in heat loss
And residue of excess oxygen during heating
There is a problem that oxidation cannot be prevented. On the other hand, Japanese Unexamined Patent Publication No. Hei.
In the tundish heating method described in
To reduce the amount of air to the hot gas burner below the theoretical requirement
To suppress oxidation of residual steel without purging inert gas
The problem like the former does not arise.
The tundish caused by the flue gas
Supply to burner to completely prevent oxidation of residual steel inside
The amount of combustion air that is generated should be 50% or less of the theoretical air amount of fuel gas.
Must be below. However, the combustion air
If the supply amount is extremely reduced, O_TwoShortage
Heating costs due to incomplete combustion
And measures such as explosion-proof and CO poisoning measures for the treatment of unburned gas.
All problems arise. The present invention has been developed in view of these problems.
For example, multiple regenerative preheaters are alternately
Switch to heat the inert gas to a high temperature,
To the inside of the tundish for efficient
While keeping heat in an oxidized state, it is already oxidized.
To reduce iron oxide even more
To provide a non-oxidizing heat retention method
It is the purpose. [0011] [MEANS FOR SOLVING THE PROBLEMS] To solve the above problems.
The present inventionNoThe non-oxidizing heating method of Ndish
In reusing the tundish that produced residual steel,
Heated by heating means provided outside the tundish
Use the active gas to keep the inside of the tundish warm and use it next time
When servingBelow the explosion limit in addition to the inert gas
A small amount of reducing gas into the tundish,
Change the atmosphere in the tundish to a non-oxidizing and reducing atmosphere.
A non-oxidizing heat retention method for a tundish,
H to neutral gas _Two And the H _Two Combines with the O component of iron oxide
The redox equilibrium curve for reducing iron by _Two / H _Two O concentration
As a redox equilibrium curve of iron depending on temperature ratio and temperature
According to this redox equilibrium curve,
H that can reduce iron at target heat retention temperature _Two / H _Two O concentration ratio and
H to be _Two Put inIt is characterized by
You. [0012] [0013] [0014] [0015] BEST MODE FOR CARRYING OUT THE INVENTION
In order to ensure the temperature at which the reusable tundish can be cast,
As a measure to solve the various problems,
The tundish without burning in the dish.
Reuse, that is, realization of a non-preheating and oxidation-free reuse process
We have been studying various experiments for this purpose. According to experiments by the present inventors, it is usually found that casting is in progress.
Surface temperature of the tundish is almost equal to the molten steel temperature1
The temperature rises to about 540 to 1570 ° C.
Sometimes the temperature starts dropping and if you let it stand,
In the case of a 70t tundish, after about 6 hours
Below 1100 ° C, 850 ° C or less after 14 hours
Become. The temperature inside the tundish is 850 ° C. or less.
At lower temperatures, oxygen is blown from below the nozzle,
Bubbling to bring the nozzle into communication
The molten steel transferred from the ladle to the tundish
It is difficult to pour into the mold from the nozzle at the bottom of the dish
is there. In addition, the temperature of the waiting tundish decreases.
And the temperature of molten steel when molten steel is injected into the tundish
As the lower volume increases, ensure the molten steel temperature at the beginning of casting
Therefore, it is necessary to increase the temperature of molten steel at the time of the injection.
However, with such a high molten steel temperature, the
The dish temperature has risen too much and the molten steel temperature
Too high, slow casting speed and breakout
Or cause it to occur. For this reason, 850 ° C.
Is the minimum reusable temperature of the waiting tundish
At the same time. In addition, as the temperature decreases, a tundish
Internal pressure is reduced, which allows external air (atmosphere) to enter
Then, the oxygen concentration in the tundish will increase.
You. Prevent oxidation of residual steel when reusing tundish
To stop, check the oxygen concentration in the waiting tundish.
It is known that it is necessary to set it to "0".
Therefore, purge the inside of the tundish with an inert gas
Oxygen with reduced tundish temperature during standby
To prevent intrusion, keep the tundish almost completely sealed
Must be kept. Waiting tundish
The temperature drop data for the
You. However, even if it is completely sealed, the temperature drops.
External sky into the shrinking tundish
It is impossible as a matter of fact to make the invasion "0"
Because there is, completely non-oxidizing only with this tundish seal
Is difficult to achieve. As a countermeasure, inert gas
(Eg N_Two) From outside the tundish with continuous purging
It is conceivable to prevent oxygen from entering. The possibility
I went to a 70t tundish to study.
According to experiments conducted by the present inventors, it was found that 120 Nm^Three/ H ratio
N continuously_TwoWhile supplying the tundish into the tundish
The temperature drop when the purge is performed is higher than when the purge is not performed earlier.
It ’s steep, about 3 hours at 1100 ° C, 8-9 hours
The temperature drops to 850 ° C and the temperature of the tundish is low
When the internal gas shrinks due to the air below,
O in the dish_TwoConcentration can be reduced only to 1-2%
It has been found. Based on these results, the present inventors have
When reusing the tundish,
Purify the inside of the tundish with inert gas heated outside.
The temperature of the inner surface of the tundish
Can be maintained at 850 ° C. or more, which is the lower limit of the casting possible temperature.
Eliminates the need for conventional preheating with combustion gases in the tundish.
Re-heat the tundish without preheating and preventing oxidation.
Completed the present invention, finding that it can be used
I came to. The tundish is provided outside the
To send the flue gas and air into the tundish.
There is no heating means such as regenerative preheater or electric resistance heating
Use electric heaters such as heaters, induction heaters, and plasma torches
Can be. In particular, regenerative preheaters use small amounts of combustion gas.
Can be used to efficiently heat the inert gas.
And a plurality of regenerative preheaters
In a tundish while heating the inert gas with a preheater
Put it in, and in the tundish with the remaining regenerative preheater
Burner while sucking (recycling) inert gas
If the regenerator is heated by the
Capacity can be reduced, so that
It is also possible to always attach it to the tundish
You. Further, together with the inert gas, H_TwoAnd CO
, A small amount of gas below the explosion limit,
By introducing the tundish inside the tundish,
Oxidation and reduction atmosphere can be used,
Not only can oxidation be suppressed and prevented, but
To reduce the residual steel_TwoO_ThreeActively prevent the generation of
Can be Also, H is added to this reducing gas._TwoUse gas
Efficient tundish with a trace amount below the explosion limit
The interior can be made a non-oxidizing and reducing atmosphere, and carbon
Consider free C generated by C-based reducing gas, that is, soot
You don't have to. [0023] DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the non-oxidizing protection of the tundish according to the present invention.
One embodiment of the heating method will be described in detail with reference to the drawings. First, FIG. 1 shows the tundish of this embodiment.
Overall configuration of non-oxidation heat retention device that implements non-oxidation heat retention method
Is shown. The tundish 1 has an opening 1 in its lid 1a.
b, 1c are connected to regenerative preheaters 2A, 2B, respectively.
You. For example, heat transfer type preheaters 2A and 2B
Spherical or pipe-shaped ceramics to increase the area
Storage chamber 3A filled with a heat storage body made of metal or metal,
3B and for heating the heat storage bodies of the heat storage chambers 3A and 3B.
And a series of combustion chambers 4A and 4B
The combustion chambers 4A, 4B are connected to the tanks through the inlet pipes 7A, 7B.
Connected to the openings 1b and 1c of the dish 1, respectively,
The main burners 5A and 5B and the pyro inside the chambers 4A and 4B
The burners 6A and 6B are provided. The insertion tube 7
A, 7B and each opening 1b, 1c of the tundish 1
In between, make the inside of the tundish 1 non-oxidized
For this purpose, sealing devices 50A and 50B described later are interposed.
ing. Also, each nozzle at the bottom of the tundish is shown in the figure.
Omitted. Next, the regenerative preheaters 2 similar to each other
To explain the condition of the piping to A and 2B,
The following description is made using the regenerative preheater 2A.
The combustion chamber 4A of the thermal preheater 2A has
A combustion chamber temperature detector 31A for detecting the temperature,
A pressure detector 33A for detecting the pressure in the combustion chamber 4A;
Is installed. Also, the storage of the regenerative preheater 2A
On the outlet side of the heat chamber 3A, the outlet temperature of the heat storage chamber 3A is detected.
The temperature detector 37A on the outlet side of the heat storage
Temperature that operates based on the output of the heat chamber outlet temperature detector 37A.
A degree switch (TS) 39A is provided. The main burner 5A is provided with M gas.
Valve 8A, M gas shut-off valve 52A, M gas flow regulating valve 9A and
And an M gas (not shown) through the M gas orifice 10A.
M gas valve 8A, M gas
N for sparging_TwoShut-off valves 11A and N_TwoThrough the pressure reducing valve 12
N not shown_TwoConnected to the source. here,
M gas is a fuel gas, for example, a converter generated in a converter.
(LD) Gas and coke oven generated by coke oven (C)
Blast furnace generated in a blast furnace with mixed gas of gas and C gas
(B) A mixed gas with a gas. In addition,
Use fuel gas such as LPG or liquid fuel instead
Is also possible. The orifice to which the M gas is supplied
10A is provided with an M gas flow detector 26A.
You. Further, the M gas valve 8A and the M gas shutoff valve 52A or
N for M gas purge_TwoDissipates in piping between shut-off valve 11A
The valve 51A is branched and the opposite branch connection end is open to the atmosphere.
Have been. The main burner 5A is provided with an air valve 1
3A, air flow control valve 14A, air orifice 15A
The air supply fan 16 is connected to the air supply fan 16. This air
Air orifice to which combustion air is supplied from supply fan 16
The air flow detector 29A is provided on the switch 15A. Further, the pilot burner 6A is
Via the M gas shut-off valve 54 for pilot burner, the M gas
For the pilot burner
N_TwoShutoff valve 53 and N_TwoThrough the pressure reducing valve 12, the N_TwoOffering
Connected to a power source. On the other hand, the heat storage chamber 3A_TwoValve 17A,
N_TwoFlow control valve 19, N_TwoOrifice 18 and the N_Two
Through the pressure reducing valve 12, the N_TwoWhen connected to a source,
The N_TwoValve 17A, H_TwoValve 72, H_TwoFlow control valve 7
1, H_TwoH not shown via orifice 70_TwoSupply
Connected to the source, and further with the exhaust valve 20A and exhaust flow or pressure
It is connected to the exhaust fan 22 via the regulating valve 21A.
You. And the N_TwoThe orifice 18 has the N_TwoSupply
N supplied from the source_TwoN to detect the flow rate of_TwoFlow detector
42, and the H_TwoThe orifice 70 has the H_Two
H supplied from the source_TwoH to detect the flow rate of_TwoFlow detection
Dispenser 73 is attached. Further, the heat storage chamber 3A and
Exhaust flow from the heat storage chamber 3A to the exhaust valve 20A
Flow rate or pressure detector 35A for detecting
And the exhaust flow or pressure regulating valve 21A and the exhaust fan.
Exhaust temperature detector 3 for detecting the exhaust gas temperature between the
8A is attached, and the output of this exhaust temperature detector 38A is
Temperature switch 40A which operates based on
You. Further, a pipe between the heat storage chamber 3A and the exhaust valve 20A.
Is connected to a dilution valve 23A.
The branch connection end is provided with a manual or automatic flow control valve 24A.
(The actual control is described later.
As shown, when the exhaust from the heat storage chamber 3A is being performed
Only because the dilution valve 23A is opened,
The exhaust air of the heat storage chamber 3A is supplied to the manual or automatic flow control valve.
It is not released to the atmosphere via the lube 24A). What
The exhaust valve 20A and the exhaust flow rate or pressure regulating valve 21A
The exhaust gas analyzer 41A connected between the
It is for analyzing and detecting the CO concentration in the inside. Then, the M gas of the M gas flow control valve 9A is
Flow rate is measured by the M gas flow rate controller (FIC) 27A.
The air flow rate of the air flow control valve 14A is
The flow rate is controlled by each of the quantity indicating controllers (FIC) 30A.
However, both FICs 27A and 30A exchange information with each other.
Enabled, so that the M gas FIC 27A
M gas flow detection according to the output from the flow rate detector 26A
Value and output from the combustion chamber temperature detector 31A.
Control information from the furnace temperature detection value and air FIC30A
The M gas flow of the M gas flow control valve 9A as described later according to
Volume control, while the air FIC 30A is
The air flow detection value and the air flow detection value according to the output from the flow detector 29A
In accordance with the control information of the M gas FIC 27A,
Thus, the air flow rate of the air flow rate adjusting valve 14A is controlled. The exhaust flow rate or pressure control valve 21A
The exhaust flow rate or pressure of the combustion chamber is determined by the pressure in the combustion chamber pressure detector 33A.
Detection value of the combustion chamber according to the output from the
Or the exhaust flow rate according to the output from the pressure detector 35A.
Is the exhaust flow rate or pressure indicating controller that reads the detected pressure value
(F / PIC) flow rate or pressure as described below by 34A
Power controlled. It should be noted that the temperature detector 37A on the outlet side of the heat storage chamber is
Output of the temperature switch 39A that operates according to the output
Is taken into the control device of the entire system (not shown),
Switching control of the regenerative preheaters 2A and 2B described later, and
N which is an inert gas_TwoThe N of gas_TwoFlow control valve 9A
It is used for controlling the input flow rate. In addition, the exhaust fan
From the exhaust temperature detector 38A provided near the fan 22
The output of the temperature switch 40A that operates according to the output of
It is taken into the control device of the whole system (not shown) and exhausted.
The flow control valve 24A that takes in the air inside (in the case of automatic control)
) Is used for opening adjustment control, etc. In addition, each of the above
On-off valve, for example, M gas valve 8A, air valve 13A, N_TwoValve 1
7A, exhaust valve 20A, dilution valve 23A, H_Two
A valve (not shown) that operates at each open / close end is provided at the valve 72 or the like.
Mitt switch is provided and the limit switch
The output of the
And used for sequence control described later. On the other hand, regarding the other regenerative preheater 2B side
Is configured similarly to the above-mentioned regenerative preheater 2A,
The main burner 5B includes an M gas valve 8B and an M gas flow control valve.
9B and the like, and connected to the M gas supply source through
N for M gas purge_TwoShut-off valve 11B or N_TwoPressure reducing valve 12
Through the N_TwoConnected to source. Also Pyro
The cut burner 6B shuts off the M gas for the pilot burner.
When connected to the M gas supply source via a valve 54 or the like,
And N for the pilot burner_TwoShut-off valve 53 or N_Two
Through the pressure reducing valve 12 and the like, the N_TwoConnected to source. Ma
The combustion chamber 4B is provided with an air valve 13B and an air flow control valve 14
B and the like, and connected to the air supply fan 16. Ma
The heat storage chamber 3B has N_TwoValve 17B or N_TwoFlow control
Negative valve 19 or N_TwoThrough the pressure reducing valve 12 and the like, the N_TwoSource
Connected, exhaust valve 20B and exhaust flow / pressure adjustment
This is connected to the exhaust fan 22 via a valve 21B and the like.
Dilution valve 23B and manual valve 24B
Are branched and connected. For other detailed configurations,
Since it is the same as the one of the regenerative preheaters 2A,
The components have the same reference numerals with the suffix B,
Detailed description is omitted. Next, the regenerative preheaters 2A, 2B and
Between these and the openings 1b and 1c of the tundish 1
FIG. 2 is used for the mounted sealing devices 50A and 50B.
I will explain briefly. The heat storage type preheaters 2A and 2B
And the sealing devices 50A and 50B are inserted as shown in FIG.
It has a function of sealing around the outer circumferences of the inlet pipes 7A and 7B.
You. Further, reference numeral 301 in the heat storage chamber 3B (3A) indicates the above-mentioned storage.
The heat storage element 301 is formed in a spherical shape here.
You. The heat storage body 301 is provided in the heat storage chamber 3B (3A).
Heat-resistant net arranged diagonally above the pipe connection part 303
A large number of heat accumulating preheaters are stored above the member 302.
When 2B (2A) is in the state shown in FIG.
The upper surface of the body 301 is indicated by the two-dot chain line in FIG.
The state shown in FIG. However, in this embodiment,
The regenerative preheater 2B (2A) is a tundish when discharging
1 is tilted in the direction of the arrow in FIG.
Heat storage element 301 is rolled under its own weight and is indicated by a two-dot chain line b in FIG.
The angle of repose stabilizes. Therefore, the regenerative preheating of this embodiment
In the heat storage chamber 3B (3A) of the vessel 2B (2A), as shown in FIG.
Weirs 304 and 305 are formed. By the way, this
Permit of the heat storage chamber 3B (3A) exit side (TCA (TCB) in the figure)
The upper limit temperature is mainly the heat resistance of the heat-resistant net member 302.
Depends on the maximum temperature. On the other hand, adjacent to the heat storage chamber 3B (3A)
As described above, the main burner 5 is provided in the combustion chamber 4B (4A).
The burner port of B (5A) is opened, and the M gas
Combustion air is supplied. Also, this main burner 5B
The pilot burner 6B (6
A) The burner opening of the pilot burner 6B is opened.
Using the M gas flame supplied to (6A) as a pilot flame,
The inburner 5B (5A) is ignited. Of these, the main
Regarding the ignition and extinguishing of the burner 5B (5A),
This is explained in detail using a sequence diagram.
Briefly explain the ignition procedure of the lot burner 6B (6A)
I will tell. As is known, this kind of pilot burner 6B
When igniting (6A), the surrounding area should not explode sufficiently.
Environment. More specifically, heat storage
Each pipe, as well as the chamber 3B (3A) and the combustion chamber 4B (4A)
In order to make a non-combustion state inside,
N which is an inert gas_TwoFill gas (or N_TwoWith gas
Purge). Therefore, the pilot bar
Before the ignition of the gas 6B (6A), the M gas shutoff valve 52
B (52A) and dissipation valve 51B (51A) are closed and M
Open the gas valve 8B (8A) to open the M gas purge N_TwoInterception
Open the valve disconnection 11B (11A) and open the main burner 5B (5
N in the piping to A)_TwoPurge with. Then the pie
With the M gas shut-off valve for lot burner 54 closed,
N for Ilot burner_TwoOpen the shut-off valve 53 and open the pilot
N inside the pipe to the connector 6B (6A)_TwoPurge with. Of course
During this time, the N_TwoValve 17B (17A) and Dairu
Exhaust valve 20 with the option valve 23B (23A) closed.
B (20A) is opened, and the combustion chamber 4B (4A) and the heat storage chamber are opened.
3B (3A) and N in the exhaust pipe_TwoPurge with. this
Thus, the environment of the pilot burner 6B (6A) is completely
And N_TwoAfter being purged with N, the pilot burner N
_TwoClose shutoff valve 53 and shut off M gas for pilot burner
Open valve 54 and ignite pilot burner 6B (6A)
I do. By doing so, the pie can be safely and reliably
The lot burner 6B (6A) can be ignited. Now, from the combustion chamber 4B (4A),
The distal end of the extended insertion tube 7B (7A) is
To the inside of the opening 1c (1b) of the lid 1a of the dish 1.
And around the opening 1c (1b) and the lid 1a.
Around the upper surface and the insertion tube 7B (7A) and in the combustion chamber 4B
(4A) between the lower surface of the sealing device 50B
(50A) is provided. Note that reference numeral 504 in the figure indicates prevention.
Heat ring, regenerative preheater 2B (2A) and tandy
Unnecessary exchange of heat with the shoe 1 is suppressed and prevented. Also,
The distal end of the insertion tube 7B (7A) is connected to the opening 1c (1b).
If it is not inserted into the inside of the
50B (50A) insertion tube 7B (7A) and tandy
Airtightness (sealing property) with the opening 1c (1b) of the brush 1
Is reduced, the N heated from the combustion chamber 4B (4A)
_TwoGas flow into the tundish 1
The ejector effect that occurs along_TwoAtmosphere containing components
Flows into the tundish 1 and
There is a possibility that the inside of the shoe 1 cannot be maintained in the non-oxidized state.
You. Therefore, in this embodiment, the distal end portion of the insertion tube 7B (7A) is used.
Into the opening 1c (1b),
N_TwoAtmospheric inflow due to the ejector effect of gas flow
It is designed to prevent suppression. Next, the tundish executed in this embodiment will be described.
The outline of the non-oxidation heat retention method is briefly described with reference to FIG.
Will be described. This tundish non-oxidation heat retention method,
Now, suppose that the heat storage body in the heat storage chamber of the heat storage type preheater A of the A system is sufficient.
Heat stored in the heat storage type preheater A
N which is an inert gas to the body_TwoWhile supplying B
Air is exhausted from the heat storage chamber of the heat storage type preheater B. At this time,
In the combustion chamber of the thermal preheater A, M gas or fuel is supplied to the main burner.
Leave them unburned without supplying burning air,
In the combustion chamber of the regenerative preheater B, M gas is supplied to the main burner.
And burning air to burn them. Do
And enough to pass through the gap between the heat storage bodies of the heat storage type preheater A.
N heated to_TwoBecomes a tundish (T / D in the figure)
And the other regenerative preheater B is forcibly exhausting.
For this purpose, suction into the combustion chamber of the regenerative preheater B
Cycle), while passing through this tundish
The tundish is heated by flowing heat transfer. one
On the other hand, the N recycled to the other regenerative preheater B_Two
Heat energy by the heat transfer to the tundish
-That is, although the temperature has dropped, the main
Gas is burning, the heat of the combustion exhaust gas
Energy and self (recycle N_Two) With thermal energy
Heated the heat storage element in the adjacent heat storage chamber and heated the heat storage element
After that flue gas and recycled N_TwoGas mixture with gas
Since the temperature of the exhaust gas consisting of has already been sufficiently lowered,
Exhaust this. However, as described above, the heat storage type
The allowable upper limit temperature is also on the exhaust side (exit side) of the heat storage chamber of the preheater B.
Therefore, the temperature on the outlet side of the heat storage chamber reaches the allowable upper limit temperature.
Or before that, N_TwoAnd the exhaust flow is reversed
Extinguishes the main burner in the combustion chamber of B type regenerative preheater B
And the main burner in the combustion chamber of the A-system regenerative preheater A
To fire. Therefore, this time, the heat storage type of the B system which is sufficiently heated
N heated sufficiently through the gap of the heat storage body of the preheater B_Two
Heats the tundish through the tundish
Heat from the combustion gas in the A-system combustion chamber
Luggy and the N _TwoAnd the residual heat energy
Is heated and then exhausted. Repeat this
O2 components contained in flue gas and air
The tundish does not flow into the
Heat the inside of the window in a state close to non-oxidation and
To increase the heat retention time of the
Almost 100% of energy input to tundish N_Two
Sensible heat to increase energy efficiency. Less than
Is how to enhance these effects.
It is art. In addition, two regenerative preheaters alternately use tandy
For a short period of time (20 to 12).
0 seconds), the entire regenerator of each regenerative preheater
Heat capacity may be small, so each regenerative preheater must be small
Can be Next, control of each valve of the piping system will be described.
Before the explanation, in the piping system of FIG.
Function of valves that are not directly involved in heat
And explain briefly. M gas shutoff for the pilot burner
N for valve 54 and pilot burner_TwoThe shutoff valve 53 is
When the pilot burners 6A and 6B are ignited and extinguished
Used when Also, as mentioned above, the main burner piping
N inside_TwoAfter purging with N_TwoCut off
The valves 11A and 11B are closed, and the M gas valves 8A and 8B are closed.
After that, the pilot burners 6A and 6B are ignited. Ma
In addition, the release valves 51A and 51B are connected to the main burners 5 respectively.
When the fire extinguishing of A and 5B is stopped, the M gas valves 8A and 8B or M
The gas shutoff valves 52A and 52B are closed, but each shutoff valve is
Because of the possibility of leakage, the M gas shutoff valve 52
A, even if a leak occurs in 52B, this release valve 51A,
By depressurizing at 51B, the M gas valves 8A, 8B
M gas does not flow downstream, that is, into the preheater
It has a function as a safety valve to make it work. Also,
Similarly, when the pilot burners 6A and 6B are ignited,
M gas supply to the burners 5A and 5B is performed by M gas valves 8A and 8B.
The M gas shut-off valves 52A and 52B are controlled to open and close by B.
It is kept open at all times. In addition, the dilution
Manual or automatic flow provided on the inlet side of valves 23A, 23B
The amount adjusting valves 24A and 24B are connected to the tandem of this embodiment.
In the non-oxidizing preheating method, the opening is always maintained at the set opening.
You. Next, the control logic of each valve of the piping system will be described.
Will be described with reference to the sequence chart of FIG. here
Then, the two regenerative preheaters have already been used
And heating of the heat storage element is repeated.
Shall be. First, at time t₀Then, the heat storage type preheating of the B system
2B to N_TwoAnd heat storage type A preheater 2A
N_TwoInto the recycling mode,
N of the B system_TwoThe valve 17B is opened from the closed state. So
And this time t₀A predetermined time T101 after
_TwoThe valve 17A is closed from the open state. At this time, important
The reason is that two N_TwoValves 17A and 17B
If it is closed at the same time and the pressure inside the tundish 1 is negative,
At the time t ₀From B
N of the system_TwoTime T20 required to open valve 17B
0 is also at time t₀From A to N_TwoValve 17A is closed
So that it is shorter than the required time T102 until
It is necessary to set a predetermined time T101. In other words, this
The required time T102 is N_TwoInput / "Combustion + N"_TwoLisa
It is the time required for switching "Ikle". This timer processing
The use of B-type N
_TwoOpen the valve 17B from closed to N_TwoOpen and close the valve
Operation, basically, N of the B system concerned_TwoValve 17B
After confirming the open signal from the limit switch,
N of the A system_TwoLogic to output an open command to valve 17A
It is appropriate to use it, but it is clear from the following formulas 1 and 2.
How to shorten the time required for switching is the combustion time rate
If the combustion time rate is increased,
To reduce the amount of combustion per hour, that is, the burner capacity
Therefore, the preheater is made smaller and lighter to make it compact.
This is advantageous in terms of installation cost and installation space.
Therefore, the timer processing as described above is required.
You. [0042]   Burning time rate = θ_B/ (Θ_B+ Θ_C) ……… (1) Where θ_C: Switching time (M gas valve closing time) θ_B: Combustion time (opening time of M gas valve)   Required combustion amount / θ_B= Burning amount per unit burning time ……… (2) Also, during this time, the A-system exhaust valve 20A, dilution
Valve 23A, air valve 13A, M gas valve 8A are closed, same
The exhaust flow rate or pressure regulating valve 21A of the A system is set at a predetermined opening.
Is defined. Also, H_TwoValve 72 is closed, N_TwoFlow control
The valve 19 is used for controlling the positive pressure in the tundish described later.
The opening is set to a predetermined value corresponding to the opening. Here, at the time of the switching
To H_TwoThe closing of the valve 72 is caused by any traffic at the time of this switching.
Bull N_TwoFlow rate cannot be secured,_Two
H inside_TwoAssumes cases where the concentration rises abnormally
This is to avoid this and ensure safety. Follow
N_TwoH inside_TwoSet an upper limit for the concentration
H when it exceeds_TwoAdopt logic to close valve
Then, the H_TwoThe valve can be basically always open
It is. The N_TwoThe setting of the flow control valve 19 is possible
This is strange, and the details of the control will be described later. On the other hand, B system
Exhaust valve 20B, dilution valve 23B, air valve 1
The 3B and M gas valves 8B are both in the closed state.
The exhaust flow or pressure regulating valve 21B is set to a predetermined opening.
ing. Next, the N of the A system_TwoWhen the valve 17A is closed
Dilution valve 23A
And H_TwoThe valve 72 is opened, and thereafter, for a predetermined time T103.
Thereafter, the exhaust valve 20A is opened. Here, the exhaust valve 2
Open dilution valve 23A before 0A
Pressure generated by the opening operation of the exhaust valve 20A
Waves can be mitigated. And the A-system exhaust valve
Same after a predetermined time T104 after 20A is opened.
The A-system air valve 13A is opened, and the air valve 13A
After a predetermined time T105 from the opening of the combustion air, the combustion air
Equal to the air amount at the end of the previous air ratio control to secure the amount
Combustion air by the A-system air flow control valve 14A
Start controlling the flow rate. Then, after a predetermined time T106
Exhaust flow rate or pressure by the pressure regulating valve 21A
Control is started (the details of the control will be described later), and
Then, after a predetermined time T107, the A-type M gas valve 8A is also turned on.
Open operation to actually open combustion of main burner 5A of A system.
Start. Is this A-system M gas valve 8A open?
After a predetermined time T108, the M gas flow control valve 9
When the M gas flow control by A starts,
The air flow control by the air flow control valve 14A is simply performed.
Change and set flow rate control to M gas air ratio control. Also,
At the same time as the M gas flow rate control,_TwoFlow control valve 19A
Is closed by a specified opening (the control details are described in the later section).
After a predetermined time T109)._TwoFlow rate
N by adjusting valve 19_TwoStart flow control. By the way,
The M gas valves 8A and 8B of this embodiment are both other valves.
It is set to open more slowly. this is,
Immediately after the M gas valves 8A and 8B open in a short time,
M gas more than the value flows into the main burners 5A and 5B
To prevent incomplete combustion from occurring.
You. While continuing this combustion state, as described above,
N heated from B type regenerative preheater 2B_TwoBut tandy
And stored in the A-system regenerative preheater 2A.
Cycled N_TwoWith the thermal energy of the flue gas
The heat storage body 301 of the heat storage chamber 3A of the heat storage type preheater 2A.
Heating the exhaust valve 20A and exhaust flow rate or pressure regulating valve
Exhausted through 21A. And actually, the A
Temperature detector 37A and the temperature switch (T
S) Feedback is performed based on the temperature of the heat storage chamber exit side detected at 39A.
Is controlled. Here, the stable combustion time is defined as M gas and air
T109 and T110 during which the control of FIG.
And the sum of After the elapse of the predetermined time T110, the switching is performed.
For operation, first, the A-system air flow control valve 14A
Stop the M gas air ratio control, and fix the opening to a predetermined opening.
And after a predetermined time T111, the exhaust of the A
Exhaust flow rate or pressure control by flow rate or pressure control valve 21A
M gas flow rate by A system M gas flow control valve 9A
Control and stop. At the same time, a predetermined time T1
N after 12_TwoN by flow control valve 19_TwoFlow control
The operation is stopped and the opening is opened by a predetermined opening. That
Thereafter, after a predetermined time T113, the A-system M gas valve 8A is turned off.
After the closing operation, the M gas valve 8A is closed.
After the fixed time T114, the air valve 13A of the A system is closed.
Let it. Next, the A-system air valve 13A is closed.
Optimized exhaust gas purge time described later
After the predetermined time T115 obtained from
The closing valve 23A and the exhaust valve 20A are simultaneously closed.
You. Then, in synchronization with the closing operation of the A-system exhaust valve 20A,
H_TwoThe valve 72 is also closed. This series of N_TwoInput /
"Combustion + N_TwoIn the recycle switch sequence
The exhaust flow rate of the system A or the opening degree of the pressure regulating valve 21A and N_Two
By properly setting the opening of the valve 19, the M gas
Exhaust gas from air and air flows into the tundish 1
And M gas, which is a combustion gas, is directly
There is no inflow. On the other hand, when the A-system exhaust valve 20A is closed.
After a predetermined time T116, N_Twovalve
17A is opened, and after a predetermined time T201, B
N of the system_TwoThe valve 17B is closed. Again,
Similarly, N of A system_TwoRequired until valve 17A opens
Time T100 is equal to N of the A system._TwoValve 17A opens.
N of B system after starting_TwoUntil valve 17B is closed
The predetermined time T20 is set to be shorter than the required time T202.
1 must be set. Next, the N of the B type_TwoWhen the valve 17B is closed
At the same timing as before,
H 23B and H_TwoOpen the valve 72, and then
After time T203, the exhaust valve 20B is opened. Soshi
After the B-system exhaust valve 20B is opened.
After the time T204, the air valve 13B of the B system is opened.
For a predetermined time T after the air valve 13B is opened.
After 205, the air flow adjusting valve 14B
Control of the combustion air flow rate is started. Then, at a predetermined time
After the interval T206, the exhaust gas flow rate or pressure regulating valve 2 is
Start the exhaust flow rate or pressure control by 1B, and then
After the fixed time T207, the M gas valve 8B of the B system is opened.
Then, the combustion of the B-system main burner 5B is actually started.
After the B-system M gas valve 8B is opened,
After a predetermined time T208, the M gas flow control valve 9B
Start the M gas flow control at the same time
The flow control of the air by the flow control valve 14B is simply a flow control.
Control to change to M gas air ratio control. In addition, the M
At the same time as controlling the gas flow rate,_TwoPredetermined flow control valve 19B
The closing operation is performed by the opening degree, and after a predetermined time T209,
The N_TwoN by flow control valve 19_TwoStart flow control
You. While continuing this combustion state, as described above,
N heated from A-system regenerative preheater 2A_TwoBut tandy
And stored in the B-type regenerative preheater 2B.
Cycled N_TwoWith the thermal energy of the flue gas
The heat storage body 301 of the heat storage chamber 3B of the heat storage type preheater 2B.
Heating the exhaust valve 20A and exhaust flow rate or pressure regulating valve
Exhausted through 21A. Then, as before,
After the stable combustion time T210 has elapsed, the air flow rate of the B system is adjusted.
Stop the M gas air ratio control by the regulating valve 14B and open the valve
Is fixed at a predetermined opening, and thereafter, after a predetermined time T211.
Exhaust flow rate of the B system or exhaust flow by the pressure control valve 21B
As with the volume or pressure control, the B system M gas flow control valve 9B
And the control of the M gas flow rate is stopped. Also, at the same time
After a predetermined time T212, the N_TwoBy flow control valve 19
N_TwoStops flow control and opens the opening by the specified amount
Let it work. Thereafter, after a predetermined time T213, the B system
The M gas valve 8B is closed and the M gas valve 8B is closed.
After a predetermined time T114, the B-type air valve
13B, and then the optimized exhaust gas
After a predetermined time T215 obtained from the sparge time,
System dilution valve 23B and exhaust valve 20B at the same time
At the same time as the closing operation of the exhaust valve 20B.
_TwoThe valve 72 is also closed. This series of N_TwoInput / "burn"
+ N_TwoIn the recycle switching sequence,
The exhaust flow rate of the system or the opening degree of the pressure regulating valve 21B and N_TwoValve 1
9 and the M gas and the air
Combustion flue gas flows into the tundish 1
And the combustion gas M flows directly into the exhaust gas.
It will no longer enter. Note that each of the heat storage type preheaters 2A and 2B
In the case where the combustion of the inburners 5A and 5B is temporarily stopped, respectively
The air flow rate by the air flow control valves 14A and 14B
Prior to stopping the control, the air flow rate must be lower than the M gas flow rate.
Because of the cade control, the combustion restarts
Order to stabilize control of air flow and exhaust gas flow
After that, the combustion is started safely. In addition,
N in steady state_TwoInput / "Combustion + N"_Tworecycling"
Is switched when a set time by a so-called timer has elapsed.
However, other than this, the output
Turns are (1) exhausted when the exhaust gas temperature exceeds the upper limit.
When protecting gas fan and maintaining thermal efficiency, (2)
When the outlet temperature of the heat storage chamber exceeds the upper limit,
(3) When the temperature of the combustion chamber exceeds the upper limit
When protecting the device itself, there are three patterns:
The switching pattern of (1) is based on dilution.
Is considered abnormal because the exhaust gas temperature is lowered
However, the switching patterns (2) and (3) are not
Works as an interlock. Next, the flue gas path in the logic will be described.
Setting time and flow / pressure control methods for each gas.
Will be explained. First, the fuel in the combustion chamber of each regenerative preheater
Finish baking, N_TwoInput / "Combustion + N" _TwoRecycle
When switching modes, N_TwoHeat storage type on the side that inputs
Since the combustion exhaust gas remained in the preheater and its piping system,
Is the N_TwoAt the same time, flue gas is injected into the tundish.
Will be entered. This combustion exhaust gas contains CO_TwoAnd H_TwoO
Oxidizing gas components such as
Combines with the residual steel, and at the start of the next casting, as described above.
Al_TwoO_ThreeWill form. Therefore, this flue gas
After purging_TwoNeed to start
You. However, the combustion in the combustion chamber of each regenerative preheater
When it is completed, the combustion chamber, heat storage chamber, and exhaust pipe
Is still full of flue gas and the exhaust gas temperature at each location
The degrees vary widely. The temperature at each site
Is the combustion exhaust gas flow rate / input N_TwoFlow rate / recycle N_TwoFlow
Combustion required by actual driving patterns
It is necessary to set the exhaust gas purge time. Here, below
The flue gas purge time t is set according to the following equation (3).
Was. [0051]   t = t_F+ T_R+ T_W                                      ……… (3) However,   t_F= V_F/ (V_G× (273 + T_F) / 273) × α₁   t_R= V_R/ (V_G× (273 + T_R) / 273) × α_Two   t_W= V_W/ (V_G× (273 + T_W) / 273) × α_Three And V_G(Nm^Three/ Sec.): Exhaust gas flow rate T_F(° C) · V_F(M^Three): Combustion chamber temperature and volume T_R(° C) · V_R(M^Three): Thermal storage room temperature and volume T_W(° C) · V_W(M^Three): Temperature / volume in piping α₁~ Α_Three:constant It is. Here, the combustion chamber volume V_F, Heat storage chamber volume
V_R, Piping volume V_WIs known, and the logic
From the allowable temperature in the heat storage chamber._TwoInput / "Combustion + N"_Two
Combustion chamber temperature T when switching "recycle" mode_F, Accumulation
Heat room temperature T_R, Piping temperature T_WIs almost stable
If this is sampled by experiments, etc.,
Flow rate V_GAnd the exhaust gas flow rate V_GIncrease
The exhaust gas purge time t, which decreases linearly with
Will be issued. Therefore, the assumed actual exhaust gas flow rate V_GOr
Thus, the combustion exhaust gas purge time t can be optimized. Next, during normal combustion in the logic,
That is, the stable combustion times T110, T210 and the end of the control.
Expressed as the sum of predetermined times T111 and T211
In time, N_TwoRegarding the opening control of the flow regulating valve 19
N_TwoFor setting the input flow rate and the recycle flow rate of wastewater
explain. Actual N_TwoThe input flow rate of the exhaust gas
It must be set precisely in consideration of the amount, etc.
Considers only the transfer of thermal energy. First, FIG. 5 relates to the exhaust of the piping system.
This is an excerpt of the area around the regenerative preheater.
And detected by the combustion chamber temperature detectors 31A and 31B.
The combustion chamber temperature T₁, The heat storage chamber outlet temperature detector 37
A, 37B is the temperature of the heat storage chamber outlet side detected by_TwoAnd
Heat stored in the heat storage body during combustion of this heat storage type preheater
Heat received per unit time of the heat storage unit as energy
Quantity Q_GIs represented by the following four equations. [0055]   Q_G= (V₁+ V_Two) × C_PG× (T₁−T_Two) ……… (Four) However, C_PG: Combustion exhaust gas and recycled N_TwoGas mixture with gas
Specific heat of (exhaust gas) V₁： Flow rate of combustion exhaust gas V_Two: Recycle N_TwoFlow rate It is. Further, in FIG.
The amount of heat dissipated per unit time is Q₁Is the real heat storage
Heat storage amount Q 'per unit time of body_GIs expressed by the following 5 formulas
You.   Q '_G= (V₁+ V_Two) × C_PG× (T₁−T_Two) -Q₁        ……… (Five) Now, the N, which is an inert gas,_TwoSet the flow rate at the time of
As described above, the amount of heat stored in the heat storage_Two
If heat exchange is not performed with the entire amount, for example,
The lower temperature of the heat storage body such as the lower heat-resistant mesh member 302 rises
As a result, a problem in heat resistance of the device structure occurs. On the other hand, N_Twoamount
Is more than necessary, the input N _TwoLow gas temperature
Causes gas supply for heating purposes
That is, the problem that the heating object is not heated occurs. Less than
From above, input on heat exchange N_TwoTemperature T_NIs the combustion chamber
Temperature T₁Since it is below, N before heat exchange_TwoTemperature T_N0When
Then, the most effective input N_TwoFlow rate V_NSatisfies the following 6 formulas
Therefore, when rearranging using the above three equations, the following 7 is obtained.
It looks like an expression. Here, the combustion exhaust gas flow rate V₁Is the combustion chamber
Is controlled by the temperature of
N_TwoFlow rate V_TwoAnd input N_TwoFlow rate V_NWhen determining the set value of
Become a constraint. [0057]   Q '_G= V_N× C_PN× (T₁−T_N0) ……… (6) ∴V_N= (V_G× C_PG× (T₁−T_Two) -Q₁) / (C_PN× (T₁−T_N0))                                                             ……… (7) However, C_PN: N_TwoSpecific heat It is. Next, the normal combustion time in the above logic
Control of opening of exhaust gas flow control valves 21A and 21B
A method of setting the flow rate of exhaust gas will be described. First, figure
6 also removes the area around the regenerative preheater related to exhaust
As shown in the figure, in FIG.
The pressure in the combustion chamber detected by the detectors 31A and 31B is
P₁, Detected by the exhaust flow / pressure detectors 35A and 35B
Pumping pressure (in-pipe pressure in the figure)_Three, Said da
Used as dilution gas from the dilution valves 23A and 23B
The supply pressure (ie, atmospheric pressure) of the air₀And then
Detected by a pressure sensor inside the tundish not shown
Pressure inside the tundish (in the furnace or T / D in this figure)
Pressure) to P_TwoAnd the exhaust gas flow rate V is the combustion exhaust gas
Flow rate V₁And recycle N_TwoFlow rate V_TwoAnd diluent gas (dairy
Solution) flow rate V_ThreeSum, that is, V = V₁+ V_Two
+ V_ThreeOf which, the flue gas flow rate V₁Is the following 8
It is represented by the formula. [0059]   V₁= Vm (G₀+ (M-1) A₀) ……… (8) However, Vm: Total fuel gas flow rate G₀： Theoretical combustion gas amount A₀： Theoretical air volume m: Air ratio It is. The above-mentioned dilution gas (dilution)
Flow rate V_ThreeIs the dilution gas supply pressure (atmospheric pressure) P₀And exhaust pressure
(Piping pressure) P_ThreePressure difference (P₀-P_Three) To decide
Therefore, for example, as shown in FIG. 7, the dilution gas supply pressure (=
Atmospheric pressure) P₀And exhaust pressure (pressure in piping) P_ThreeDifferential pressure
(P₀-P_Three) And dilution gas (dilution) flow rate V
_ThreeInvestigate the relationship with
Dilution gas supply pressure (atmospheric pressure) P₀And exhaust pressure (pipe internal pressure
Force) P_ThreeDifferential pressure (P₀-P_Three) To the dilution gas (die
Solution V)_ThreeCan be obtained. On the other hand, as described above, recycled N_TwoFlow rate
V_TwoAnd input N_TwoFlow rate V_NIs determined by the above equation (7).
Is set, this input N_TwoFlow rate V_NDecide and resai
Kuru N_TwoFlow rate V_TwoIs found. Here, input N_TwoFlow rate V_N
Is determined by the amount of heat required to heat the tundish,
For example, from the heat balance equation expressed by the following equations 9 and 10
The following equation is derived to calculate the input N_TwoFlow rate V_NSet
be able to. [0062]   Q_TD= A_TD× α × (T_GOUT−T_TD) ……… (9) However, Q_TD  : Tundish heat received A_TD  : Internal surface area of tundish α: Tundish inner surface and input N_TwoHeat transfer between
number T_GOUT: Input N_TwoTemperature when leaves the tundish T_TD  : Tundish inner surface temperature   Q_G= V_N× C_P× (T_GIN−T_GOUT) ………(Ten) However, Q_G  : The amount of heat released from the input N2 to the tundish C_P  : Average specific heat of input N2 T_GIN： Temperature of input N2 Where Q_TD= Q_GFrom   V_N= A_TD× α × (T_GOUT−T_TD) / (C_P× (T_GIN−T_GOUT))                                                             ……… (11) Each flow rate V thus obtained₁~ V_ThreeFrom the sum of
The gas flow rate V is set, and this exhaust gas flow rate V is achieved.
The exhaust gas flow rate or pressure regulating valve 21A for the control time
What is necessary is just to control the opening degree of 21B. The recycling N_TwoFlow rate V_TwoIs
It can also be set as follows. That is, as described above
Pressure inside the tundish_TwoCan be detected
For example, recycle N from inside this tundish_TwoCheck the quantity
The necessary and sufficient conditions for maintaining the pressure are as follows:
_TwoAnd combustion chamber pressure P₁Pressure difference (P_Two-P₁) Is a positive value
There will be. Here, the pressure P in the tundish_TwoPassing
And combustion chamber pressure P₁Differential pressure (P_Two-P₁) And recycling
N_TwoFlow rate V_TwoIs a unique function at equivalent temperature and pressure.
Therefore, for example, as shown in FIG.
Pressure P in dish_TwoAnd combustion chamber pressure P₁Differential pressure (P
_Two-P₁) And Recycle N_TwoFlow rate V_TwoInvestigate the relationship with
The detected pressure P in the tundish_Twoas well as
Combustion chamber pressure P₁Differential pressure (P_Two-P₁To satisfy)
Is the pressure P in the combustion chamber.₁To control the recycling
Le N_TwoFlow rate V_TwoMay be set.
The exhaust gas flow rate V is set in
Control of exhaust gas flow or pressure control valves 21A and 21B
The degree can be controlled. Controlling the flow rate of each gas as described above
And at least stationary N_TwoInput / "Combustion + N"_TwoResai
The pressure inside the tundish in the
It will be possible to have. However, N_TwoInput /
"Combustion + N_TwoWhen switching to the “recycle” mode,
The pressure inside the tundish cannot be maintained at positive pressure
Could be. That is, for example, the sequence of FIG.
From the closing of the M gas valve 8A in the chart to the closing of the M gas valve 8B
In the required switching time until opening, the combustion exhaust gas flow rate V ₁Is reasonable
Logically "0", so if the
Kuru N_TwoFlow rate V_Two= (Exhaust gas flow rate V-dilution)
Flow rate V_Three) In such a case.
To the input N_TwoFlow rate V_NAnd the exhaust gas flow rate V_TwoInput
/ "Combustion + N_TwoThe setting is the same as in the normal operation of
The pressure inside the tundish becomes negative.
To suck the flue gas and air into the tundish.
I will. Then, such N_TwoInput / "Combustion + N"
_TwoWhen switching to "recycle" mode, N
_TwoOpen the flow control valve 19 and open N_TwoFlow rate V_NIncrease
Or the exhaust flow rate or pressure regulating valves 21A, 21B.
By closing the opening and decreasing the exhaust gas flow rate V,
The pressure inside the tundish is maintained at a positive pressure. More specific
To the input N_TwoFlow rate V_NIncrease input when increasing
N_TwoFlow rate ΔV_NTo explain the setting method of
N_TwoInput / "Combustion + N"_TwoRecycle mode switching
Combustion gas flow rate V₁Becomes “0” at the time of the switching.
Recycling N_TwoFlow rate V_2CIs the steady state recycle
Le N_TwoFlow rate V_2SIs expressed by the following equation (12). [0066]   V_2C= V₁+ V_2S                                          ……… (12) On the other hand, the pressure in the tundish
(Negative discharge port, nozzle port, etc.)_TwoFlow rate V_Wdependent upon
Yes (V_WThe higher the pressure, the higher the pressure in the tundish
Wear). Therefore this radiation N_TwoFlow rate V_WIs expressed by the following equation (13).
Is done. [0067]   V_W= V_N-V_2S                                          ………(13) Therefore, this dissipation N_TwoFlow rate V_WMake constant when switching
To do this, connect the above equations 12 and 13 with an equal sign
As is clear from this, basically, the combustion gas flow rate V₁Minute
Only input N_TwoFlow rate V_NShould be increased. In practice,
Recycling N during normal operation_TwoFlow rate V_2SIs in the tundish
The pressure is smaller than the limit value so that the pressure becomes
Value is set. Therefore, it is possible to set the
Cycle N_TwoSet the upper limit of the flow rate to "V_2SUpper limit "
If the relationship is investigated in advance, the increase in recycling N_TwoFlow rate Δ
V_TwoIs used to establish the following equation (14). [0068]   V_2SUpper limit = V_2S+ ΔV_Two                                    ………(14) Where ΔV_Two> 0 In addition, in order to make the internal pressure of the tundish positive,
Essential emission N_TwoThe lower limit of flow rate "V_WThe lower limit is the following 15
expressed. [0069]   V_WLower limit = V_N-V_2SUpper limit ............ (15) Therefore, the following equation (16) is obtained from the equations (14) and (15).
The following equation (17) is obtained from the equation (16) and the equation (12). [0070]   V_WLower limit = V_N− (V_2S+ ΔV_Two……… (16)   V_WLower limit = V_N− (V_2C-V₁) −ΔV_Two           = V_N-V_2C+ V₁-ΔV_Two                        ............ (17) Therefore, from equation 17, the internal pressure of the tundish is
In order to make₁-ΔV_TwoOnly "
N_TwoFlow rate V_NThis relationship is
Increase input N to satisfy Equation 18_TwoFlow rate ΔV_NSet
It should be fixed. [0071]   ΔV_N≧ V₁-ΔV_Two= V₁− (V_2SUpper limit -V_2S……… (18) If the exhaust gas flow rate is reduced during this switching,
The increase input N_TwoFlow rate ΔV_NCan be made even smaller
Wear. This means that the decrease in exhaust gas flow rate is V₁Decrease
It is clear if you think about it. In this embodiment, the input N_TwoFlow rate V_NIncrease and
The reduction of the exhaust gas flow rate V satisfies the above conditions at the same time.
The simultaneous operation in a well-balanced manner
In-push pressure P_TwoIs set so that positive pressure is maintained.
ing. Of course, the pressure P in the tundish_TwoThe aforementioned
Is detected, the input N_TwoFlow rate V_NIncrease
It is possible to change and set the addition amount and the decrease amount of exhaust gas flow rate V
Becomes The above-described control contents are implemented in combination.
This allows the flue gas and air to be absorbed into the tundish.
Further oxidation of residual steel
Can be reliably prevented from being suppressed. By the way, this implementation
In the example, the inside of the tundish is further reduced.
By doing so, it is intended to make almost no residual steel oxidation. Here, the inside of the tundish is reduced, for example.
H as the reducing gas to make the atmosphere_TwoWhen using
The H_TwoIs iron oxide Fe_ThreeO_FourAnd the O component of FeO
Reducing iron or H_TwoO component of O oxidizes iron
Iron oxide Fe_ThreeO_FourOr the state of becoming FeO,_Two
Concentration and H_TwoRedox equilibrium curve depending on O concentration and temperature
This is shown in FIG. 9 as a line. This redox equilibrium curve is represented by H_Two/ H_TwoO concentration
The redox equilibrium curve of iron,
FIG. Also, FIG.
When CO is used as a reducing gas capable of achieving
CO / CO_TwoRedox plane of iron depending on temperature of concentration ratio
The balance curve is also shown. In this case, keep the tundish
Since the thermal target temperature is about 1000 ° C or more,
High temperature N_TwoIn the atmosphere, iron can be reduced from the same figure
Na H_Two/ H_TwoO concentrationratioIs about 1.5
You. Therefore, H as a reducing gas_TwoIt is better to use_Twoof
Since a small amount may be used, the amount
The reducing gas concentration below the explosion limit (flammable limit) concentration
It seems that it is advantageous in controlling. Here, it leaked into the air as is known.
H in the case_TwoThe flammability limit of is less than about 4%
From the H_TwoConsider the conditions for adding. Now, tongue
Average O in dish_TwoConcentration to C_O, Inside the tundish
The input N to_TwoFlow rate V_N, Also in the tundish
H added to_TwoFlow rate V_HAnd inside the tundish
O invaded_TwoH reacts with_TwoQuantity (= H to be generated_TwoO
Amount) V_{H2 0}Is given by the following equation (19). [0077]   V_H20= 2 × V_N× C_O                                    ............ (19) Therefore, the ignited H in the tundish_TwoOf which, O
H that does not react with_TwoQuantity V _HrIs given by the following equation (20). [0078]   V_Hr= V_H-V_H20= V_H-2 x V_N× C_O                  ............ (20) Therefore, the H generated here_TwoO amount V_H2OIn fact against
Input H_TwoQuantity V_HrConcentration ratio H_Two/ H_TwoO is the following 21
Since this is represented by the left side, this is the predetermined concentration ratio 1.5
This is all we need to do to solve this
Essential average O_TwoConcentration C_O, Input N_TwoFlow rate V_N, Additive H_TwoFlow
Quantity V_HIs 22. [0079]   (V_H-2 x V_N× C_O) / (2 × V_N× C_O) ≧ 1.5 ……… (21) ∴V_H≧ 5 × V_N× C_O                                      ………(twenty two) On the other hand, the input N_TwoFlow rate V_NH added in_TwoFlow rate V_H
The flammability limit range of is expressed by the following equation (23).
Input N obtained_TwoFlow rate V_N, Additive H_TwoFlow rate V _Hconnection of
Is 24. [0080]   V_H/ (V_N+ V_H) ≦ 0.04 ……… (23) ∴V_H≤V_N/ 24 ............ (24) FIG. 11 shows the relationship between these 24 equations._TwoActual flammability lower limit curve
Indicated by a line, and this H _TwoAbove and below the lower flammability curve,
Average O given by equation (2)_TwoConcentration C_OWith parameters as
N_TwoInput -H_TwoThe relationship between the amounts added is shown by a two-dot chain line. this
From the above H_TwoThe upper part of the lower flammability curve is the N of the present embodiment.
_TwoAtmosphere H_TwoCombustible range of gas (HN gas in the figure)
Because of this H_TwoAverage above the lower flammability curve
O_TwoWhen the concentration is ≧ 0.7%, a safety problem occurs. Change
To the input N set as described above._TwoFlow rate V_Nunder
The flue gas and air are not sucked into the tundish.
If the reduction of iron oxide is promoted efficiently and efficiently,
_TwoThe addition may be very small, for example, N_TwoInput
1000Nm^Three/ H, added H_TwoFlow rate V_HIs
Only 10Nm^Three/ H has been found to be sufficient. The present embodiment implemented as described above
The operation of will be described. First, the N_TwoInput / "burn"
+ N_TwoWhen switching to the "recycle" mode, the combustion exhaust gas
Set the sparging time optimally or_TwoFlow rate V
_NOr temporarily increase the dilution flow rate.
By adjusting the opening of the valves 24A and 24B,
(Here, the reducing gas H_TwoHas not been added
In this embodiment, as shown in FIG.
(T / D) pressure is always higher than “0”, ie, positive pressure.
Was able to hold. In contrast, N_TwoInput / "Fuel
Yaki + N_TwoWhen the recycle mode is switched, the combustion exhaust gas
Set the sparging time to the optimum_TwoFlow rate V_NTo
Temporarily increased or adjusted the dilution flow rate
In the prior art example, where there is no
Although the pressure in the dish (T / D) is temporary
It becomes a so-called negative pressure lower than “0”, and
The flue gas and air are sucked into the tundish as in
It is assumed that they will be lost. Also, as described above, N_TwoInput / "Combustion + N"_Two
When switching to the “recycle” mode, the flue gas
Time can be set to the optimum_TwoFlow rate V_NOne
The dilution flow control valve 2
By adjusting the opening of 4A and 24B (here
However, the reducing gas H_TwoWas not added)
Fig. 13a shows the oxygen concentration in the tundish (T / D) of the example.
Shown in As is clear from the figure, the tundish
The internal oxygen concentration is determined by the first N_TwoInput / recycle mode
Some peaks appear when switching, but others are stable
As a result, it can be seen that it is kept below the target upper limit. one
On the other hand, according to a conventional example in which such a control mode is not performed at all.
The oxygen concentration in the tundish (T / D) is shown in FIG.
So each N_TwoEach time the input / recycle mode is switched, the
And it always exceeds the target limit
I understand that there is. Further, N_TwoInput / "Combustion + N"
_TwoWhen switching to the “recycle” mode, the flue gas
Storage time can be set optimally,_TwoFlow rate V_NTo
Temporarily increase the dilution flow control valve
By adjusting the opening of 24A and 24B,
Again, the reducing gas H_TwoIs not added) Figure 1
As shown in Fig. 4, the average O in the tundish_TwoConventional concentration
The amount of oxidation of the remaining steel can be greatly reduced.
The width could be reduced. By the way, FIG.
The oxygen concentration in the tundish shown in FIG.
Gas H_TwoIs the case without the addition of
Reducing gas H_TwoIn a tundish with added oxygen
The concentration is always "0" (below the measurable limit of the gas analyzer).
I know it will be. Then, almost complete non-oxidation
Heat retention in a state where the amount of oxidation of the remaining steel is greatly reduced
When the prepared tundish was subjected to actual casting,
As shown in 15, in the casting of the first Ch (charge)
Total hot balding occurrence rate is 100%
Original gas H_TwoAbout 32.0 without adding
Original gas H_TwoWhen added, it is reduced to about 3.5
Can be reduced, and
Hot in the first and second slabs immediately after the start of casting
The scab generation rate is defined as the reducing gas H
_TwoIs approximately 27.9 without adding the reducing gas H
_TwoIf added, reduce it to about 1.1.
I was able to. Of course, as shown in FIG.
_TwoBy using a regenerative preheater (burner in the figure),
Keep the temperature inside the tundish (T / D) above the opening limit
The elapsed time from the end of pouring to be retained has been greatly increased
Can be extended and the number of stations can be greatly extended
Was. In the above embodiment, N was used as the inert gas.
_Two, H as a reducing gas in the tundish_TwoUsing
Only the cases and the advantages of using them.
However, the inert gas is Ar, and the reducing gas described above is Ar.
Use various carbon dioxide and heavy hydrocarbons including CO
Of course, it is possible. However, such carbon C-based conversion
If a primary gas is used, enter the flammable range as described above.
Therefore, it is necessary to take additional safety measures.
Not only is it necessary, but also the release of solid C, that is, the generation of soot
It is necessary to prevent
To conduct carbon-based reducing gas
Note that the flow rate must be set. In the above embodiment, the inert gas is used.
N_TwoH, which is a reducing gas,_TwoIf you supply
Was described in detail, but the oxygen concentration was extremely
Input H when low_TwoSince the flow rate can be very small,
Without significantly heating the regenerative preheater or tandem
May be supplied directly into the tissue itself,
Therefore, it has almost no effect on the temperature drop of the tundish
The inventors have also confirmed by experiments. Further, as the reducing gas, H_TwoAdd etc.
If so, N_TwoOf the side where inert gas such as
By extinguishing the heater pilot burner,
It becomes easy to obtain a high level of reduction. That is, in the embodiment,
In case of tundish heating, the pilot burner
The flue gas flow rate is_Two+ H_Two(Inert gas +
Less than 1% of reducing gas) and CO_TwoAnd H_TwoAcids such as O
Since the oxidizing gas component is about 0.2%,
There is no practical problem if the fire is not extinguished,
N_Two+ H_TwoLow flow rate of (inert gas + reducing gas)
If not, pilot bar of those input preheaters
High levels of non-oxidation or reduction by extinguishing fire
You can get the status. Next, FIG. 17 shows a tundish of the present invention.
Still another implementation of inert gas heating means for heat-free non-oxidative heat retention
Here is an example. This is a non-inert gas heating means.
Using a transfer-type plasma torch 120
You. This type of plasma torch 120 includes a cathode 121.
And the torch itself has an anode 122, and the cathode 12
Inert gas supplied to the torch via 1 or its reduction
The mixed gas flow with the reactive gas is used to discharge the electrodes 121 and 122.
High temperature plasma obtained by making it more plasma
23 heats the inner wall surface of the tundish 1. This
Ar, N as the plasma gas_TwoThe above-mentioned HN
It is also possible to use a gas in combination. In general plasma jet heating,
Plasma temperature 3000-10000 ° C is used
However, in this embodiment, the atmosphere in the tundish is applied to the plasma jet.
By bringing ambient gas in, up to 2000 ° C or less
Tundish fire resistant with high temperature jet gas whose temperature has been lowered by
And spray it on the object in a non-oxidizing atmosphere.
Heating is performed at 1300 ° C. That is,
With the plasma torch 120 attached to the lid 1a of the
Inert gas fed into dish 1 or its reducing property
The gas mixture with the gas is turned into plasma and the tundish 1
Spray on the bottom. The heat transfer during this heating is
Heat transfer from turbidity and the resulting tandi
Takes the form of radiant heat transfer from the bottom to the other side. However, in the case of plasma jet heating,
Before re-use of tundish to reduce running cost
To ensure that the inner surface temperature of the tundish is 1300 ° C
Heat only for the required time, other waiting time
Inside was no preheating standby. FIG. 18 shows a heat insulating tank having a heat insulating material thickness of 30 mm.
Plasma torch 1 when casting with dish
20 non-oxidative heat retention experiment of tundish
The results are shown. Tandy at 1570 ° C during casting
After a 7-hour standby time, the
The inner surface temperature of the dish decreased to 1100 ° C. or less.
Subsequently, N using the plasma torch 120 is used._TwoGas plasma
Start non-oxidizing heating in the tundish by jet,
After 4 hours, the internal surface temperature of the tundish reaches the target of 1300.
° C was reached and became reusable. Total wait time is 11
It is time, during which one charge in another tundish
16 charges of 40-minute casting could be performed. In the above embodiment, no tundish was used.
Electric heating means for inert gas in oxidation heat retention method
Thus, the case where the plasma torch is used has been described. Other
An electric induction heater or an electric resistance heater may be used.
Heating the steel to high temperature, durability, running cost
It is disadvantageous in terms of the [0094] As described above, the tandy of the present invention is
According to the non-oxidizing heat retention method for
Heated to at least 850 ° C while waiting for the dish
An inert gas is supplied to keep the tundish warm.
Combustion gas in the tundish
The conventional preheating of
It can greatly prevent and prevent oxidation of steel, and
It is possible to greatly extend the waiting time until reuse
The effect is obtained. Further, in addition to the inert gas, an explosion limit
Introduce the following trace amount of reducing gas into the tundish.
If the atmosphere in the tundish is reduced,
Oxidation can be further suppressed and prevented, and
To the remaining steel_TwoO _ThreeActively reduce the generation of
Can be Also, H is added to this reducing gas._TwoUse gas
If it is, a very small amount less than the explosion limit
An atmosphere can be obtained and a carbon C-based reducing gas
It is not necessary to consider the generation of free C as in the above. [0096]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall configuration diagram showing a tundish non-oxidation heat retention apparatus that implements the tundish non-oxidation heat retention method of the present invention. FIG. 2 is a sectional view showing an example of a regenerative preheater of FIG. FIG. 3 is a schematic explanatory view of a method for keeping a tundish without oxidation according to the present invention. FIG. 4 is a sequence chart of valve opening / closing control showing one embodiment of the non-oxidizing heat retention method for a tundish of the present invention. FIG. 5 is an explanatory diagram for setting an input N ₂ flow rate. FIG. 6 is an explanatory diagram for setting an exhaust gas flow rate. FIG. 7 is an explanatory diagram of a dilution gas flow rate used for setting an exhaust gas flow rate. FIG. 8 is an explanatory diagram of a recycled N ₂ flow rate used for setting an exhaust gas flow rate. FIG. 9 is an explanatory diagram of the redox equilibrium of iron in an H ₂ —H ₂ O atmosphere. FIG. 10 is an explanatory diagram of a redox equilibrium of iron. FIG. 11 is an explanatory diagram of H ₂ addition conditions. FIG. 12 is an explanatory diagram of a pressure in a tundish. FIG. 13 is an explanatory diagram of an oxygen concentration in a tundish. FIG. 14 is an explanatory diagram of a residual steel oxidation amount in a tundish. FIG. 15 is an explanatory diagram of a hot barb generation rate. FIG. 16 is an explanatory diagram of a temperature in a tundish. FIG. 17 is a conceptual diagram showing still another embodiment of the non-oxidizing heat retention method for a tundish of the present invention. FIG. 18 is an explanatory diagram of a transition of a tundish temperature in the non-oxidizing heat retention method for the tundish shown in FIG. [Description of Signs] 1 is a tundish 2A, 2B is a regenerative preheater (heating means) 3A, 3B is a regenerative chamber 4A, 4B is a combustion chamber 5A, 5B is a main burner 6A, 6B is a pilot burner 7A, 7B is an insert Pipes 8A and 8B are M gas valves (fuel gas valves) 9A and 9B are M gas flow control valves (fuel gas flow control valves) 13A and 13B are air valves 14A and 14B are air flow control valves 16 are air supply fans 17A and 17B is an N ₂ valve (inert gas valve) 19 is an N ₂ flow regulating valve (inert gas flow regulating valve) 20A and 20B are exhaust valves 21A and 21B are exhaust flow or pressure regulating valves 22 are exhaust fans 23A and 23B Dilution valves 26A and 26B are M gas flow rate detectors (fuel gas flow rate detectors) 27A and 27B are M gas flow rate flow controllers (fuel gas flow rate flow controllers) 29A and 29B are air flow rates Dispensers 30A and 30B are air flow rate indicating controllers 31A and 31B are combustion chamber temperature detectors 33A and 33B are combustion chamber pressure sensors 34A and 34B are exhaust gas flow rate / pressure indicating controllers 35A and 35B are exhaust gas flow rate detectors 37A and 37A. 37B is a heat storage chamber outlet temperature detector 38A, 38B is an exhaust gas temperature detector 42 is an N ₂ flow detector (inert gas flow detector) 43 is an N ₂ flow indicator controller (inert gas flow indicator controller) 50A , 50B are sealing devices 51A, 51B are a dissipating valve 71 is an H ₂ flow control valve (reducing gas flow control valve) 72 is an H ₂ valve (reducing gas valve) 73 is an H ₂ flow detector (reducing gas flow detection 74 is a H ₂ flow rate controller (reducing gas flow rate controller) 120 is a plasma torch 123 is a plasma 301 is a heat storage body 302 is a heat-resistant net member 304 is a weir 305 is a weir

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Junichi Hasunuma 1-chome, Mizushima Kawasaki-dori, Kurashiki-shi, Okayama Pref. Chome (without address) Kawasaki Steel Corporation Mizushima Works (72) Inventor Kazuaki Hara 1-chome, Mizushima Kawasaki-dori (Kurashiki City, Okayama Prefecture) Kawasaki Steel Corporation Mizushima Works (56) References JP-A-8 JP-A-155599 (JP, A) JP-A-7-112249 (JP, A) JP-A-6-281350 (JP, A) JP-A-2-37949 (JP, A) JP-A-7-246456 (JP, A) JP-A-9-53886 (JP, A) JP-A-4-144747 (JP, A) JP-A-9-295126 (JP, A) JP-A-9-295127 (JP, A) 295110 (JP, A) Patent 2991 941 (JP, B2) US Patent 5,700,420 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 11/10 310 B22D 11/10 360 B22D 41/015 F23L 15/02 F27D 7 / 06

Claims (1)

(57) [Claims 1] When reusing a tundish having residual steel on the inner wall, an inert gas heated by a heating means provided outside the tundish is used to recycle the tundish. the heated holding, and when the subject to be used next, the inert gas
In addition, a small amount of reducing gas below the explosion limit
Into the tundish to deoxidize the atmosphere in the tundish.
And non-oxidizing heat retention method for tundish in reducing atmosphere
Wherein H ₂ is used as the reducing gas, and the H ₂ is an acid
Redox equilibrium curve that reduces iron by combining with O component of iron fossil
Can be converted to iron redox depending on the H ₂ / H ₂ O concentration ratio and temperature.
Calculated as a one-dimensional equilibrium curve, and
Can reduce iron at the target heat retention temperature of the tundish
A non-oxidizing heat retaining method for a tundish , wherein H ₂ is supplied so as to have a H ₂ / H ₂ O concentration ratio .