JPH0440408B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is directed to supplying oxygen gas and powder fuel into a molten iron bath charged in a bottom blowing converter or a top and bottom blowing converter through a switching valve. The present invention relates to an improvement in a switching method for realizing reliable switching to each blowing system when blowing.

(Prior art) Japanese Patent Publication No. 60-40487 discloses a device for introducing into a molten iron bath a fuel containing fine carbon such as coal and coke dust suspended in a carrier medium and oxygen. When introduced into a molten iron bath, a reliable and trouble-free supply of the fuel below the surface of the molten bath is guaranteed over a long period of time,
Further, a device has been proposed in which the tuyere is not blocked and is maintained in an open state while fuel is not being fed.

The device disclosed in the above-mentioned publication (hereinafter simply referred to as a switching valve) has a movable valve member disposed within a housing that includes a fuel supply pipe, an oxygen supply pipe, and a tuyere pipe. The valve member is actuated by controlling the pressure of oxygen in the supply pipe, and either fuel or oxygen is blown into the converter through the tuyere pipe.

Specifically, by reducing the oxygen blowing pressure in the oxygen supply pipe by an adjustable pressure difference of 0.5 to 10 bar compared to the blowing pressure in the tuyere pipe, oxygen is removed by a movable valve member disposed within the housing. The supply hole is closed, and at this time, fuel supply from the fuel supply hole is started. Conversely, when starting the supply of oxygen, the movable valve member closes the fuel supply hole by increasing the pressure difference, and the supply of oxygen is started from the oxygen supply hole.

(Problems to be Solved by the Invention) This switching valve has a simple mechanism that can avoid dangers such as coal dust explosions when injecting fine particulate fuel containing oxygen gas and carbon into the converter. Although it is advantageous, it has the following problems. In other words, such switching valves are normally located near the bottom shell of a converter in an atmosphere with a relatively high temperature of about 300°C, and in order to electrically adjust the operation of the switching valve from the outside, a regulating medium is used. Therefore, it was not possible to directly detect whether or not the switching valve was operating reliably. For this reason, for example, when switching from fuel blowing operation to oxygen blowing operation using such a switching valve, it is necessary to lower the supply pressure of the carrier gas for blowing powdered fuel; The lowering timing was not appropriate, and there were disadvantages such as the pressure difference between the switching valves being reduced and the operation of the movable valve member becoming uncertain, and the pressure at the tuyeres being lowered because the oxygen gas was not supplied in time.

The purpose of the present invention is to solve the above-mentioned problems that occur when blowing oxygen gas and powdered fuel into a converter by applying such a switching valve, and to improve the efficiency of each injection system for oxygen gas and powdered fuel. The purpose of this invention is to propose a switching method that is advantageous in realizing reliable switching.

(Means for solving the problem) The above object is achieved by controlling the supply pressure in each blowing system separately and ensuring a pressure difference inside the switching valve.

That is, the present invention provides a method for selectively injecting either oxygen gas or powdered fuel into a bottom-blown or top-bottom-blown converter having an oxygen gas injection system and a powdered fuel injection system. (1) Switching from powdered fuel to oxygen gas is performed by adjusting the blowing pressure in the oxygen gas blowing system to the value necessary for switching. After maintaining the above, the supply of carrier gas by the powdered fuel injection system is stopped, and the carrier gas remaining in the powdered fuel injection system is released. (2) Transfer from oxygen gas to powdered fuel The switching is performed by maintaining the blowing pressure in the powdered fuel blowing system at a value necessary for switching, and then stopping the supply of oxygen gas by the oxygen gas blowing system, and removing the oxygen gas remaining in the oxygen gas blowing system. This is a method for switching the oxygen gas and powder fuel injection system in a converter, which is characterized in that it can be performed without releasing the gas.

(effect) The present invention will be described in detail below with reference to the drawings.

FIG. 1 schematically shows the equipment for supplying oxygen gas and powdered fuel to a converter. In the figure, 1 is a converter, 2 is a tuyere for optionally blowing oxygen gas or powdered fuel into the iron molten bath of the converter 1, and 3 is a converter.
is a switching valve that switches between oxygen gas and powdered fuel using the pressure difference between them; 4 is an oxygen gas blowing system that mainly blows oxygen gas (sometimes inert gas); 5 is oxygen Gas release valve, 6
is an oxygen gas pressure gauge, 7 is an oxygen gas cutoff valve,
8 is an oxygen gas flow meter, and 9 is an oxygen gas supply pressure control device. 10 is a powder fuel injection system that blows powder fuel together with carrier gas;
11 is a carrier gas diffusion valve, 12 is a fuel storage and extraction device for storing powdered fuel and cutting out the required amount, 13 is a carrier gas pressure gauge, 14 is a carrier gas cutoff valve, 15 is a carrier gas flow meter, and 16 is a carrier gas supply pressure control device, 17
18 is a carrier gas flow rate control valve, and 18 is a powdered fuel cutoff valve.

Normally, the oxygen gas flow rate in the oxygen gas blowing system 4 is regulated by the cross-sectional area of the oxygen blowing hole of the switching valve 3, and in order to secure and keep the required amount of gas flow constant, the oxygen gas supply pressure must be controlled. The supply pressure is controlled to 10 to 20 kg/cm ² G, for example 15 kg/cm ² G, by the device 9. By the way, in the powdered fuel injection system 10, when only the carrier gas is blown, the pressure of the carrier gas at the inlet of the tuyere 2 is about 4 to 8 kg/cm ² G, although it varies depending on the carrier gas flow rate. Here, from the powder fuel injection system to the oxygen gas injection system 4,
For example, if the oxygen gas supply pressure is 15 kg/cm ² G, the switching valve 3 starts switching from the blowing system 10 to the blowing system 4, but the carrier gas in the powder fuel blowing system 10 is not controlled by the flow meter 15 or the flow rate. Since the flow rate is controlled by a flow rate control device consisting of a control valve 17, etc.,
The secondary pressure of the carrier gas supply pressure control device 16 at the inlet of the switching valve 3 is 10 to 20 kg/
cm ² ·G has risen to, for example, close to 16 kg/cm ² ·G, and in such a state it is not possible to provide the switching valve with the necessary and sufficient pressure difference for switching.

The present invention selectively injects either oxygen gas or powdered fuel into the equipment described above by switching the switching valve in the following manner.

First, when switching from blowing gas by the oxygen gas supply system to blowing fuel by the powdered fuel blowing system, the carrier gas diffusion valve 11
After closing, the carrier gas cutoff valve 14 is opened to allow the carrier gas whose pressure is controlled by the carrier gas supply pressure control device 16 to flow. When it is confirmed that the pressure of the carrier gas has reached a predetermined value using the pressure gauge 13, the oxygen gas cutoff valve 7 is closed and the oxygen gas diffusion valve 5 is opened to remove the oxygen remaining in the oxygen gas supply line 4. Release the gas and reduce the pressure.

Here, the predetermined pressure of the carrier gas is the pressure necessary to prevent molten iron from being inserted into the tuyere.
and an oxygen gas cutoff valve 7 and an oxygen gas diffusion valve 5
Considering the operating speed of the switching valve 3, an appropriate pressure, for example 5 kg/cm ² ·G, is set to realize smooth switching operation of the switching valve 3. Further, for example, the carrier gas diffusion valve 11 may not be fully closed while receiving a closing command from a control device (not shown), or
Alternatively, if there is a leak in the fuel injection system 10 and the pressure of the carrier gas does not rise to a predetermined value, the oxygen gas cutoff valve 7 remains open and the oxygen gas diffusion valve remains closed. Valve 3 is not switched to the powder fuel injection side.

Next, when switching from blowing powdered fuel to blowing oxygen gas, the oxygen gas diffusion valve 5 is closed and the oxygen cutoff valve 7 is opened. Next, oxygen gas is caused to flow by the oxygen gas supply pressure control device 9. and,
When it is confirmed by the flow meter 8 and pressure gauge 6 that the flow rate and pressure of oxygen gas have reached predetermined values, the carrier gas cutoff valve 14 is closed and the carrier gas diffusion valve 11 is opened to allow the oxygen gas to remain in the powder fuel injection system 10. The pressure is lowered by releasing the carrier gas.

Here, the predetermined value of the oxygen gas pressure mentioned above is the pressure necessary to prevent molten iron from being inserted into the tuyere, and is selected by taking into account the operation of the carrier gas cutoff valve 14 and the carrier gas diffusion valve 11. The value is set to an appropriate value to realize smooth switching operation of the valve 3, for example, 5 kg/cm ² ·G. Even if this pressure is set to a high value such as 14Kg/cm ² G, the switching valve 3 will start switching to the powder fuel injection side, but during this operation, the carrier gas will be Total 15 and flow control valve 17
Since the flow rate is still controlled by the flow rate control device consisting of the following, the pressure of the carrier gas increases as the cross-sectional area of the carrier gas flow path inside the switching valve becomes smaller, and the maximum value of the pressure is Since the pressure reaches the secondary set pressure value of the carrier gas pressure control device, the pressure difference acting inside the switching valve becomes very small, and the switching operation may not be completed in a short time. Therefore, it is desirable that the set value of the oxygen pressure is as low as possible within a range that does not cause molten iron to be inserted into the tuyere.

Also, for example, the oxygen gas diffusion valve may not fully close despite receiving a closing command from a control device (not shown), or there may be a leak in the oxygen gas blowing system 4, and the oxygen gas pressure may not reach the predetermined value. At times, the carrier gas cutoff valve 14 remains open, the carrier gas diffusion valve 11 remains closed, and the switching valve 3 is not switched to the oxygen gas injection side.

In the present invention, since the above-described operation is performed, a pressure difference inside the switching valve 3 can be ensured, and the blowing system can be switched reliably.

(Example) Example 1 Using the equipment shown in Figure 1, oxygen gas and powdered fuel were alternately blown into the molten iron bath in the bottom blowing converter via the switching valve 3 in the manner described above. The operating status of the switching valve 3 was investigated.

Powdered fuel at a speed of 300Kg/min, flow rate 60Nm ³ /
Nitrogen gas was used as a carrier gas and was blown into the molten iron bath in the converter 1 through the switching valve 3 and the tuyere 2. At this time, the carrier gas pressure gauge 13
showed 13 to 15 Kg/cm ² ·G. From this state, the system was switched to the oxygen gas blowing system using the logic shown in time chart A in FIG. First, the fuel cutoff valve 18 is closed, and after a predetermined time (T ₁ second) has elapsed, the oxygen gas diffusion valve 5 is closed, and then the oxygen gas cutoff valve 7 is opened, and the pressure measured by the oxygen gas pressure gauge 6 reaches the predetermined pressure of 5 kg. /cm ² , the carrier gas cutoff valve 14 is closed and the carrier gas diffusion valve 11 is opened, the pressure in the powdered fuel injection system 10 decreases, and the switching valve 3 switches between the oxygen gas injection system and the powdered fuel injection system. Due to the pressure difference with the system, the system smoothly switched to the oxygen gas injection system, and oxygen gas was blown at a predetermined flow rate of 60Nm ³ /min. At this time, the oxygen gas pressure gauge 6 is about 11
It showed Kg/cm ²・G. Next, from this state,
Using the logic shown in B of the time chart in Figure 2, the system was switched to the powder fuel injection system again. First, the carrier gas dissipation valve 11 is closed, and then the carrier gas cutoff valve 13 is opened, and the pressure measurement value by the carrier gas pressure gauge 13 reaches the predetermined pressure of 5 kg/kg.
When the temperature reached cm ² ·G, the oxygen gas cutoff valve 7 was closed and the oxygen gas diffusion valve 5 was opened to lower the pressure of the oxygen gas blowing system. As a result, the switching valve 3
The movable valve member (not shown) of the switching valve 3 moves toward the powder fuel injection system by the force of the internal spring (not shown), and carrier gas (nitrogen gas) flows out at a predetermined flow rate of 60Nm ³ /min. Ta. After a predetermined time (T ₂ seconds) has elapsed since the oxygen gas diffusion valve 5 opened,
Open the powder fuel cut-off valve 18 and drain the powder fuel at 300 ml.
Blowing was started at a flow rate of Kg/min.

Example 2 In the above Example 1, the switching from powdered fuel to oxygen gas was performed by maintaining the blowing pressure in the oxygen gas blowing system at a value higher than the value required for switching, and also by switching from oxygen gas to powdered fuel. The switching to is performed by maintaining the blowing pressure in the powdered fuel blowing system at a value higher than the value required for switching, and
The above switching is performed by controlling the oxygen gas pressure acting on the switching valve 3 and operating a movable valve member (not shown) of the switching valve 3. but,
If the powdered fuel injection system 10 using powdered fuel
If a malfunction occurs due to blockage of the carrier gas dispersion valve 11 or powder fuel is caught in the carrier gas diffusion valve 11, it is difficult to ensure safe and reliable switching using a method that uses only the pressure value as a switching condition. Therefore, in the second embodiment, in addition to the pressure value, each cutoff valve 7, 14,
The open/close status of each relief valve 5, 11, each flow meter 8, 1
By adding each gas flow rate value according to No. 5 as a switching condition, safe and reliable switching is attempted. The switching method in Example 2 is shown in the time chart of FIG.

First, from a state in which powdered fuel is injected at a flow rate of 300 Kg/min of powdered fuel, a flow rate of 60 Nm ³ /min of carrier gas (nitrogen gas), and an indication value of 13 to 15 Kg/cm ² ·G of carrier gas pressure gauge 13, Switching to the oxygen gas injection system was performed as follows. In other words, a predetermined time (T ₁ second) after closing the cutoff valve 18
After that, close the oxygen gas diffusion valve 5, and confirm that it is fully closed using a limit switch (not shown).
Open the oxygen gas cutoff valve 7. Confirm that the oxygen gas cut-off valve 7 is fully open with a limit switch (not shown), and when the pressure measurement value with the oxygen gas pressure gauge 6 exceeds the predetermined pressure of 5 kg/cm ² ·G, measure the oxygen gas flow rate with the oxygen gas flow meter 8. After confirming that the value has reached the predetermined flow rate of 4 Nm ³ /min (this value varies depending on the piping volume of the oxygen gas blowing system from the oxygen gas cutoff valve 7 to the switching valve 3), the carrier gas cutoff valve 14 is was closed, and the carrier gas diffusion valve 11 was opened. As a result, the switching valve 3 switches to the oxygen gas blowing system side due to the differential pressure between the oxygen gas blowing system 4 and the powdered fuel blowing system 10, and the predetermined flow rate is determined.
Oxygen gas began to be blown in at 60Nm ³ /min.

Next, from this state, the system was switched to the powdered fuel injection system again as follows. First, the carrier gas diffusion valve 11 was closed, and after confirming its fully closed state using a limit switch (not shown), the carrier gas cutoff valve 14 was opened. The carrier gas pressure gauge 13 is 4 kg/cm ² ·G or more, and the carrier gas flow meter 15 is 6 Nm ³ /min. After confirming that the carrier gas cutoff valve 14 is fully open using a limit switch (not shown),
After closing the oxygen gas cutoff valve 7 and confirming its fully closed state using a limit switch (not shown), the oxygen gas diffusion valve 5 was opened. As a result, the switching valve 3 was switched to the powder fuel injection system side, and the carrier gas (nitrogen gas) began to flow at a predetermined flow rate of 60 Nm ³ /min while being controlled by the carrier gas flow rate control valve 17. After a predetermined time (T ₂ seconds) had passed since the oxygen gas diffusion valve 5 was fully opened, the powder fuel cut-off valve 18 was opened, and powder fuel began to be blown in at a predetermined flow rate of 300 kg/min.

In this example, by checking the flow rate of oxygen gas or carrier gas while checking the opening/closing status of each cutoff valve and each release valve using a limit switch, it is possible to check the malfunction of the cutoff valves and to prevent malfunction of each blowing system, especially the powder fuel blowing system. Blockage can be detected, and subsequent switching operations can be stopped based on this detection, so switching can be performed more safely and reliably than in the first embodiment.

(Effects of the Invention) According to the present invention, when blowing oxygen gas and powdered fuel into the converter through the switching valve, it is possible to ensure a pressure difference inside the switching valve, so that the pressure difference in each injection system can be maintained. Reliable switching is possible, which makes it possible to prevent combustion accidents caused by mixture of oxygen and carbon-containing powder fuel and to achieve safe and accurate blowing control.

[Brief explanation of the drawing]

FIG. 1 is a system diagram for blowing oxygen gas and powdered fuel into the converter, and FIGS. 2 and 3 are time charts for explaining how to switch between the oxygen gas and powdered fuel injection systems. 1... Converter, 2... Tuyere, 3... Switching valve,
4...Oxygen gas blowing system, 5...Oxygen gas diffusion valve, 6...Oxygen gas pressure gauge, 7...Oxygen gas cutoff valve, 8...Oxygen gas flow meter, 9...Oxygen gas supply pressure control device, 10... Powdered fuel injection system, 11... Carrier gas diffusion valve, 12... Powdered fuel storage and extraction device, 13... Carrier gas pressure gauge, 14... Carrier gas cutoff valve, 15... Carrier gas flow meter, 16... Carrier gas supply pressure control device, 17...Carrier gas flow rate control valve,
18...Powdered fuel cutoff valve.

Claims (1)

[Claims] 1. In order to selectively blow either oxygen gas or powdered fuel into a bottom blowing or top blowing converter having an oxygen gas blowing system and a powdered fuel blowing system, (1) Switching from powdered fuel to oxygen gas requires the blowing pressure in the oxygen gas blowing system to be actuated as follows: (2) Converting oxygen gas from oxygen gas to powdered fuel while stopping the supply of carrier gas by the powdered fuel injection system and releasing the carrier gas remaining in the powdered fuel injection system. The switching is performed by maintaining the blowing pressure in the powdered fuel blowing system above the value required for switching, and then stopping the supply of oxygen gas by the oxygen gas blowing system, and removing the oxygen remaining in the oxygen gas blowing system. A method for switching an oxygen gas and powder fuel injection system in a converter, characterized in that the switching is performed after gas is released.