JPS5925005B2 - Steel smelting furnace exhaust gas recovery method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering exhaust gas from a steel smelting furnace, and more particularly to a method for minimizing excessive suction of outside air and emission of exhaust gas into the atmosphere during recovery.

Exhaust gas from pure oxygen top-blown or bottom-blown steel smelting furnaces consists mainly of carbon monoxide (hereinafter abbreviated as CO), and various methods have been implemented to recover this gas unburned and use it as fuel gas. There is.

As a measure to increase the calories of this exhaust gas, that is, to improve the CO content, a control method is proposed in which the amount of generated exhaust gas is detected as the gas pressure in the recovery hood, and the induced air volume of the exhaust gas recovery device is determined based on this detected pressure value. A method is known in which the rate at which CO generated during refining is combusted in the recovery process, that is, the combustion rate of generated CO, is controlled to be constant, or a method is controlled in which the amount of suction air is controlled according to changes in the amount of generated CO.

According to each of the above control methods, the CO recovery rate is greatly improved.

Furthermore, in recent years, with the aim of further improving the 00 recovery rate, the above-mentioned input method has been introduced to compensate for control delays in response to sudden changes in the amount of gas generated, such as when auxiliary materials such as iron ore are input. A method is provided for preemptive control using a signal.

However, as a practical matter, even with the above-mentioned strict control, it is not possible to completely suppress excessive attraction or the opposite ejection of plumes, and there is still room for improvement.

When the present inventors investigated this point, it was found that the amount of exhaust gas is closely related to the condition of the steel refining furnace.

In other words, the amount of exhaust gas generated is affected by the slag generation status, in other words, the level of slag generated in the furnace. Even if gas generation itself is carried out normally, it is trapped as bubbles in the slag generated in the furnace, and is released as exhaust gas. This was replaced by the phenomenon of increasing the slag level by removing it from the furnace.

Alternatively, the generated gas is successively trapped in the slag in this way, and the generated slag level increases rapidly, causing the slag in the furnace to form and slopping, or when measures to prevent slopping are taken. A much larger amount of gas was ejected at once than the amount generated.

This situation is shown in Figure 1, where the generated gas is captured by the slag produced in the furnace, resulting in slag forming or slopping.
The period a until the anti-slopping measures are taken is this period a.
Since the time itself is extremely short, the detection delay b and control delay C result in excessive suction d, while on the other hand, if slopping or measures to prevent slopping are taken, plume ejects d'.

The present invention focuses on the fact that the slag level affects the amount of gas generated, and aims to further improve the amount of CO gas recovered.The present invention detects the furnace condition, that is, the slag level generated in the furnace, and increases the detected value. exceeds a predetermined value and a slag forming phenomenon is predicted, the amount of exhaust gas recovered is determined based on the detection signal of the slag level generated in the furnace, instead of the conventional steady exhaust gas recovery control. However, after the slag level drops to a steady level, the original steady recovery method is resumed.

This method enables more precise exhaust gas recovery.

The present invention will be explained in detail below based on specific examples.

In FIG. 2, reference numeral 1 denotes a converter, in which oxygen is blown into the steel bath from a blowing oxygen lance 2 to refine the steel.

Exhaust gas generated from the converter 1 enters a primary cooling dust collector 6 through a collection hood 4 having a vertically movable skirt 3 and a duct 5.

Here, the gas becomes clean, passes through the induced blower 7, and is transferred to the recovery switching device 8, where the gas in the middle stage of refining with a high CO content is transferred to the holder 1.
It will be operated to be recovered on 7th.

In this example, the amount of exhaust gas generated is detected as the pressure inside the hood.

That is, the pressure at the bottom of the hood is measured by a differential pressure transmitter 10 as a pressure difference between the pressure outlet 9 and the atmosphere, and the signal is input to a controller 11.

A target differential pressure setting value is given to the controller 11 in advance, and the signal from the differential pressure transmitter 10 and the differential pressure setting signal from the controller 11 are compared, and the damper in the secondary cooling dust collector 6 is A control signal is transmitted to a servo device 13 that drives the exhaust gas 12 to recover exhaust gas.

On the other hand, the level of slag generated within the furnace is measured by detecting the sound level within the furnace using a sound meter 14 attached to the top of the hood, for example.

The relationship between this slag level and the sound inside the furnace is already known.

Now, if the slag level in the converter is increasing and the slag forming phenomenon is predicted to exceed a predetermined level, the sound level detected by the sound meter 14 is sent to the slag level converter 15. At this point, the sound change in the furnace is signal-processed into a slag level change, which is transmitted to the slag level difference detector 16 and compared with a set value.

Here, the slag level change difference is processed by a predetermined coefficient and sent to the aforementioned controller 11, which sends a control signal to the servo device 13 as an interrupt signal prior to normal control, and operates the damper 12 to control the amount of exhaust gas induced. Determine.

In other words, the above coefficient gradually reduces the suction amount as the slag level in the furnace rises, and suddenly decreases the suction amount when the slag level rises to the point where forming slag starts to slop, or when the anti-slopping agent is introduced. This is given to increase the amount of attraction, and the first
Apply in a manner that prevents excessive suction or ejection of smoke.

The period of advance interrupt control according to the present invention described above is
Since slag slopping or the amount of post-processing gas that takes measures to prevent slag will drop rapidly, this should be controlled until a certain period of time after the peak of the slag level in the furnace is detected, and for example, by a timer (not shown). release and return to the original normal control.

FIG. 3 shows the operating situation of the above-mentioned invention. As shown in FIG. 3, according to the present invention, changes in the internal pressure of the hood can be suppressed to a minimum, and as a result, proper suction without excessive suction and exhaust gas blowout is possible.

As described above, according to the present invention, by adding a control system that follows the slag level to the conventional exhaust gas treatment control system, the damper for determining the amount of exhaust gas can be operated before detecting and grasping the amount of exhaust gas generated, and the slag forming Furthermore, it is possible to prevent excessive suction of outside air during slopping or abnormal exhaust gas generation such as during slopping, and furthermore, it is possible to prevent plumes from emitting from the furnace mouth, thereby making it possible to improve the CO gas recovery rate.

In the above explanation, as an example of detecting changes in the slag level in the furnace, an example was shown in which changes in the slag level were indirectly measured from the sound generated in the furnace. However, other measurement examples (including direct examples) are also possible. Needless to say, these can also be used in the present invention.

[Brief Description of the Drawings] Fig. 1 is an explanatory diagram showing the operating situation of the conventional method, Fig. 2 is an explanatory diagram showing an example of the apparatus for implementing the method of the present invention, and Fig. 3 is an explanatory diagram showing the operating situation of the present invention. be. 1... Converter, 2... Oxygen lance for blowing, 3... Skirt, 4... Hood, 5
...Duct, 6...Cooling dust collector, 7.
...Induced air blower, 8...Recovery switching device,
9...Pressure outlet, 10...Differential pressure transmitter, 11...Controller, 12...Damper, 13...Servo Apparatus, 14... Sound meter, 15... Slug level converter, 16... Slug level difference detector.

Claims (1)

[Claims] 1 In an exhaust gas recovery method that determines the recovery amount according to the status of exhaust gas generation in a steel smelting furnace, the slag level in the furnace is detected during the recovery period, and if this detected value exceeds a predetermined value, slag forming is predicted. A method for recovering exhaust gas from a steel smelting furnace, characterized in that the amount of exhaust gas to be recovered is determined based on this detection signal.