JPH0547601B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method of operating an evaporative cooling type converter exhaust gas treatment apparatus designed to protect a cooler and reduce power consumption of a cooling water circulation pump.

[Prior Art] Generally, a converter is operated as follows. First, as a step before starting blowing, the converter 1 is tilted as shown at 1' in FIG. 2, scrap is introduced into the converter 1, and molten pig iron is charged (hereinafter referred to as the pig iron receiving step). Next, the converter 1 is set upright. In this state, auxiliary raw materials such as lime and mataru stone are added. This completes the pre-blowing process and starts blowing. As a post-blowing step, the blowing is temporarily interrupted, the converter 1 is tilted as indicated by 1', and the molten steel in the converter is sampled to inspect the condition of the steel. If the inspection results are good, the blowing is completed, but if the inspection results are still insufficient, the converter 1 is stood upright again and the blowing is carried out again. In this way, the blowing is completely completed, and the oxygen blowing lance 10 is pulled up.
Prepare for tapping. Tapping is performed by tilting the converter 1 at an angle of 1".

In this manner, the operation of the converter goes through the steps of pre-blowing, blowing, completion of blowing, preparation for tapping, and tapping, and then the first charge is completed and the second operation begins.

As an example, the time allocation during this period is approximately 20 minutes for blowing.
The non-blowing period is approximately 10 to 15 minutes, and this is repeated alternately to create a so-called batch operation.

In this converter operation, pure oxygen is blown into the converter 1 from the oxygen injection lance 10 in the converter exhaust gas treatment equipment shown in Fig. 2 during blowing, and a large amount of dust is generated during decarburization. A large amount of high-temperature CO gas (CO concentration 90-100%) containing 1200-1300℃ is generated. This CO gas is a toxic and flammable gas, and if it is released into the atmosphere, it may cause fire, explosion, or poisoning. After being attracted and cooled, and then being removed by dust removers 4 and 5,
Only gas with a high CO concentration is recovered into the gas holder 8 as a valuable gas. On the other hand, gas with a low CO concentration at the start and end of pure oxygen blowing (hereinafter referred to as blowing) is passed through the chimney 7 by switching the switching damper 9, burned at the top, and then released into the atmosphere.

On the other hand, in the converter exhaust gas treatment equipment, the converter 1 is operated in batches, so the temperature is increased to 100℃←→ every 30 to 45 minutes.
There is a sudden temperature change of 1300℃/1 minute, which causes a large thermal shock to the converter exhaust gas treatment equipment, especially the cooler 3. Also, if water gets mixed into the hot metal/molten steel in the converter 1, there is a danger of a steam explosion. For some reason,
Converter exhaust gas treatment equipment requires high reliability,
The reality is that water leakage due to damage to the cooler 3 is particularly unacceptable.

On the other hand, coolers for converter exhaust gas treatment equipment can be roughly divided into hot water cooling types and evaporative cooling types (which fall under the boiler type in a broad sense). The hot water cooling type basically consists of a hot water circulation pump, a cooler, and a heat exchanger, and has a temperature of 30 to 35℃.
The cooling water supplied to the cooler is 70% at the cooler outlet.
The temperature reaches ~75℃ and is supplied to the heat exchanger.
After being cooled to 30-35°C, it is again fed to the cooler. On the other hand, the evaporative cooling type basically consists of a hot water circulation pump, a cooler, a drum (tank), and a water supply system, and is operated under pressure. To explain this with reference to FIG. 2, cooling water stored in a tank 15 is supplied into the jacket of the cooler 3 through a conduit 13 by a circulation pump 12. The cooling water supplied to the cooler 3 is heated by the high-temperature CO gas flowing inside the cooler 3, and flows through the conduit 14 as a mixture of steam and water, so-called hot water.
It is returned to tank 15. The energy (heat) absorbed by the cooler 3 cools the converter exhaust gas by evaporating the hot water in the tank 15, and the temperature of the cooling water is approximately constant at the saturation temperature of its pressure. Therefore, the temperature change in the cooler during blowing and non-blowing is smaller in the evaporative cooling type, and the amount of repeated thermal stress generated is also lower, making it a more reliable equipment than the hot water cooling type. . In addition, in Fig. 2, 16 is a steam pipe, 17 is a water supply pump, 11 is an auxiliary raw material input port, and 2
is a skirt.

However, hot metal (steel) in a steelworks is produced in a blast furnace →
There is a large flow from converter to ingot making, and it is impossible to omit this process.Stopping these facilities will immediately lead to a halt in production.Stable operation of the facilities is essential for a steelworks. In factories, particular attention is paid to stable operation of converter exhaust gas treatment equipment, especially coolers. Specifically, damage to the heat transfer tube of the cooler (water leakage due to cracks on the heat transfer surface)
There is a need for an operating method that minimizes the occurrence of heat shock and repeated thermal stress, which are a major factor in this, and to reduce the temperature difference between non-blowing and blowing. In addition, in the evaporative cooling type, the entire system is pressurized and the temperature of the cooling water is high even during non-blowing, so if the amount of circulating water is reduced, the molten metal will be removed from the converter refractories, the hot metal in the converter, and the molten steel after blowing. The radiant heat causes local evaporation within the cooler, resulting in poor circulation.
It is thought that the heat exchanger tubes of the cooler may be damaged due to overheating, and in order to avoid these phenomena, protect the equipment, and ensure stable operation, we are aware that this is the most disadvantageous method economically. Sometimes 100% circulating water
Water drainage methods have been adopted. In this way, with conventional cooling water circulation, the circulation pump was operated at its rated value even during non-blowing periods when no CO gas was generated, and more cooling water was supplied to the cooler than necessary. Extra power was being consumed.

However, since the oil shocks in 1971, energy conservation has gained momentum, and many energy conservation measures have been implemented in recent years even in steel mills, which are energy-intensive industries. Under these circumstances, the inventor of the present invention has conducted extensive research on energy saving measures for converter exhaust gas treatment equipment, and as a result, has developed a method to lower the circulation pump during non-blowing in evaporative cooling type converter exhaust gas treatment equipment. If it is rotated under load (low rotational speed), the flow resistance of the cooling water circulation circuit will be small, so the radiant heat from the converter refractories and the hot metal in the converter will cause partial evaporation in the heat transfer tubes of the cooler. Rather, the natural circulation flow due to local cooling water temperature differences (=cooling water density differences) is taken into account, and the circulation amount in the cooler increases, resulting in poor circulation and poor circulation of cooling water due to partial evaporation. In addition, in the evaporative cooling type, the system is always pressurized, so there is almost no change in the temperature of the cooling water, even if the amount of circulating water is reduced. It was found that there was almost no temperature change in the cooler.

[Problem to be solved by the invention]

The present invention was developed based on the above knowledge, and
Cooling while protecting the cooler from the radiant heat of the converter refractories and molten metal in the converter before preparing for blowing, and the radiant heat of the converter refractories and molten steel in the converter during tipping of the converter after blowing. An object of the present invention is to provide a method of operating an evaporative cooling type converter exhaust gas treatment apparatus that can reduce the amount of cooling water supplied to the converter and thereby reduce the power consumption required to drive the circulation pump.

[Means to solve the problem]

In order to solve the above problems, the operating method of the evaporative cooling type converter exhaust gas treatment device of the present invention is an evaporative cooling method in which exhaust gas generated from the converter is cooled, then dust is removed, and gas with a high CO concentration is collected into a gas holder. In the type converter exhaust gas treatment equipment, before preparation for blowing, the cooling water circulation pump is installed by adding the natural circulation amount of cooling water due to the positional difference of the cooler to the circulation amount that does not cause overheating of the heat transfer tubes due to the radiant heat of the hot metal in the converter. Reduce the amount of cooling water circulating in the cooler by lowering the rotation speed, then charge the raw materials into the converter, stand the converter upright, and before starting blowing, raise the cooling water circulation pump to the rated rotation speed to cool it down. A predetermined amount of cooling water is circulated in the vessel, then blowing is started, and when the blowing is finished and the converter is tilted to complete preparation for tapping, the rotation speed of the cooling water circulation pump is lowered and the rotation speed is lowered before the preparation for blowing. It is characterized by maintaining the state of

[Effect]

As mentioned above, the operating method of the evaporative cooling type converter exhaust gas treatment equipment of the present invention is to adjust the amount of cooling water by changing the position of the cooler to the amount of circulating water that does not cause overheating of the heat transfer tubes due to the radiant heat of the hot metal in the converter before preparation for blowing. The amount of cooling water is reduced by lowering the rotational speed of the cooling water circulation pump, taking into account the natural circulation amount of water, so the cooler can be protected from the radiant heat of the converter refractories and the hot metal in the converter before blowing preparation, and the cooling water circulation is also reduced. The power consumed to drive the pump can be reduced. In addition, after charging the raw materials into the converter and before starting blowing after the converter is erected, the rotation speed of the cooling water circulation pump is increased to the rated value to circulate the cooling water at a predetermined flow rate. It can handle sudden temperature rises without any problems. Furthermore, when blowing is completed and the converter is tilted to complete preparation for tapping, the rotational speed of the cooling water circulation pump is lowered to maintain the state before preparation for blowing. The cooler can be protected from the radiant heat of the molten steel in the converter, and the power consumed to drive the cooling water circulation pump can be reduced.

〔Example〕

An embodiment of the present invention will be described. FIG. 1 shows the relationship among the converter exhaust gas amount (curve A), the cooling water flow rate (curve B), and the circulation pump driving power (curve C) in accordance with the converter operating process.

In the figure, as a preliminary step before the start of blowing, the converter is tilted to charge scrap, and then hot metal is charged (raw material charging). In this state, the converter is tilted, so the cooler does not receive radiant heat from the hot metal. After charging the raw materials, the converter is erected. From this point on, the cooler receives radiant heat from the hot metal in the converter, but since the circulation pump is rotating at a low load, the flow resistance of the cooling water circulation circuit is small, and the cooling water is circulated naturally. However, the heat transfer tubes of the cooler will not be overheated by the radiant heat of the hot metal. At this time, the converter exhaust gas amount is zero, and in this embodiment, the cooling water flow rate is about 20% when the flow rate during blowing is 100%.

In this case, if the circulation resistance of the circulation pump is small, or if a pipeline is provided to bypass the circulation pump (the circulation resistance of the circulation pump is small), or if the tank is installed at a sufficiently high place and If the water head pressure for circulation is sufficient, it is also possible to stop the circulation pump.

Next, increase the rotation speed of the circulation pump to its rated operation (100%) to circulate the cooling water necessary to start blowing. After that, oxygen is blown into the converter to start blowing. When blowing begins, carbon (C) in the hot metal reacts with oxygen, generating high-temperature CO gas. This reaction progresses rapidly due to the high temperature of the hot metal, and the temperature of the generated gas increases from 1200 to 1200 in a short period of about 1 minute.
Although the temperature reaches 1300℃, as mentioned above, 100% of the cooling water is passed through before the blowing starts, so the heat transfer tubes of the cooler can be protected.

Next, at the end of the blowing, stop the blowing once,
Perform sampling of molten steel in the converter. If the inspection results from this sampling are good, the blowing will be completed as shown in curve A, but if the results are unsatisfactory, then the blowing will be restarted (curve A').
After that, blowing is completed.

In this way, preparation for tapping is performed when blowing is completely completed. In this case, before the converter is tilted (in the upright state of the converter), there is still some high-temperature gas remaining from the converter, and the molten steel immediately after blowing is stopped is at an extremely high temperature of 1700℃. Since the radiant heat is much larger than that of hot metal (by the way, the radiant heat from molten steel at 1,700°C is about 2.2 times that of molten metal at 1,350°C), at this point the cooling water is still being circulated 100% of the time.

After this condition subsides, the converter is tilted to tap the steel (tilting tap). at this point
The load on the circulation pump is reduced.

In this case, there is radiant heat from the molten steel during tilting, but
The heat transfer tubes of the cooler are protected by natural circulation of approximately 20% of the cooling water as before the start of blowing.

In the operation of the above exhaust gas treatment device, the driving power of the circulation pump (curve C) increases or decreases in proportion to the amount of cooling water (circulation pump load).

The operation of the exhaust gas treatment device is generally performed by field workers. In this case, the rotation speed of the circulation pump is controlled based on the operation of the converter upright (before the start of blowing) and tilting of the converter (at the end of blowing).

Of course, it is also possible to extract an electrical signal (for example, a limit switch) from the operation of the converter to automatically control the rotation speed of the circulation pump.

〔Effect of the invention〕

As detailed above, according to the operating method of the evaporative cooling type converter exhaust gas treatment equipment according to the present invention, while protecting the cooler, the operation is performed from the time when the converter is tilted after blowing to the time before preparation for blowing. Since the rotational speed of the cooling water circulation pump can be lowered during non-blowing to reduce the amount of cooling water, the power consumed to drive the cooling water circulation pump can be significantly reduced, resulting in an extremely large energy saving effect.

[Brief explanation of the drawing]

FIG. 1 is an embodiment of the operating method of the evaporative cooling type converter exhaust gas treatment device of the present invention, and is a diagram showing the relationship between the converter exhaust gas amount, cooling water amount, and circulation pump driving power with respect to the converter operating process. be. FIG. 2 is a schematic diagram showing the entire evaporative cooling type converter exhaust gas treatment device. 1... Converter, 3... Cooler, 4, 5... Dust remover, 6... Induced blower, 8... Gas holder, 12
... Circulation pump, 13, 14 ... Conduit, 15 ...
tank.

Claims (1)

[Claims] 1 After cooling the exhaust gas generated from the converter, dust is removed.
In an evaporative cooling type converter exhaust gas treatment equipment that collects gas with high CO concentration in a gas holder,
Before preparing for blowing, the rotation speed of the cooling water circulation pump is lowered to reduce the rotation speed of the cooling water circulation pump, taking into consideration the natural circulation amount of cooling water due to the difference in the position of the cooler, and the circulation amount that does not cause overheating of the heat transfer tube due to the radiant heat of the hot metal in the converter. Next, after charging the raw materials into the converter and standing the converter upright, before starting blowing, increase the cooling water circulation pump to the rated speed to increase the cooling water in the cooler to the specified amount. circulates, then starts blowing, and when blowing is finished and the converter is tilted to complete preparation for tapping, the rotational speed of the cooling water circulation pump is lowered to maintain the state before preparation for blowing. A method of operating an evaporative cooling type converter exhaust gas treatment equipment.