JPS6320405A - Skirt control method for converter waste gas treatment device - Google Patents

Abstract

PURPOSE:To prevent surging of a fan by raising a skirt up to a prescribed height when the state of the decrease of the flow rate of a waste gas down to a prescribed value or below continues at the time of treating and recovering the waste gas while the throat and skirt of a converter are held hermetically closed. CONSTITUTION:The throat and skirt (inside seal) 4a of the converter 1 are held hermetically closed or are put in the state approximately similar thereto and blowing is executed in this state with the converter 1. The waste gas generated at this time is sucked and discharged through dust collectors 11a, 11b by the induced draft fan 14. The gaseous pressure at the throat part is detected by an in-furnace detector 6 and the opening degree of a damper 12 in the secondary dust collector 11b is controlled. A control device 15 controls a skirt operating device 16 in accordance with the signal from a waste gas flow rate transmitter 5 to rise the skirt 4a and to admit the atm. air from the spacing between the skirt 4a and the throat when the state of the decrease of the flow rate of the waste gas down to the prescribed value or below continues for the prescribed time or longer. The generation of the surging in the fan 14 is thereby prevented and the safe operation is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a skirt control method in a converter waste gas treatment device (OG) equipped with a surging prevention function of an induced fan (ID fan).

(Prior art) Conventional converter waste gas treatment equipment is normally operated without bringing the skirt part located above the furnace mouth into close contact with the furnace mouth, and therefore the furnace pressure or furnace internal pressure is approximately plus,
It was within the range of minus several fins H20 (water column). In other words, if the furnace internal pressure is lower than atmospheric pressure, air will be sucked in from the gap between the furnace mouth and the skirt, so even when the amount of waste gas generated is small, if the specified furnace pressure side Gas flow rates were obtained, which prevented blower surging.

[Problem that the invention seeks to solve]

However, if the amount of waste gas generated from the furnace decreases when the skirt is in close contact with or close to the furnace mouth, air cannot be sucked from the furnace mouth even if the furnace pressure is controlled, or Even if it were possible, the amount would be very small, so the flow rate of the waste gas would not increase much, and as a result, there would be a problem that surging could not be prevented. In other words, the converter waste gas treatment equipment is designed to keep the equipment safe while cooling the waste gas, collecting dust, and continuing blowing.Ensuring safety is the most fundamental thing. Therefore, if the blower causes surging, the operation must be stopped.

Therefore, it is an object of the present invention to prevent the blower from surging and to ensure safe operation.

(Means for solving the problem) In a converter waste gas treatment system that prevents surging by controlling the blower inlet damper in stages, the waste gas flow rate is monitored and the amount of 2 it is below a predetermined value. If this condition continues for a certain period of time, the skirt is raised to a predetermined height.

(Operation) In other words, as mentioned above, in the conventional type, which operates without bringing the skirt part into close contact with the furnace mouth, severe surging can be avoided as long as the furnace pressure is controlled. This surging problem cannot be avoided with the type of equipment that operates with the furnace mouth and skirt sealed or in a similar state, and many of the existing converter waste gas treatment equipment are of this type. By doing the above, the amount of air sucked from the furnace mouth is increased to prevent surging from occurring.

〔Example〕

FIG. 1 is an explanatory diagram for explaining the invention in detail, and FIG.
The figure is a schematic diagram showing a specific example of a converter waste gas treatment apparatus in which the present invention is implemented, and FIG. 3 is a graph for explaining a conventional example of an improved surging prevention control method.

First, FIG. 2 will be explained. In addition, in the same figure,
1 is a converter, 2 is hot metal and scrap, 3 is a top blowing lance, 4a is a skirt (inner seal), 4b is a skirt (outer seal), 5 is a waste gas flow rate transmitter, 6 is a furnace pressure transmitter, 7 is a Hood section, 8 is a blower artificial damper (suction damper), 9 is a damper controller, 10 is an upper safety valve, lla
is the primary dust collector, llb is the secondary dust collector, 12 is the damper, 1
3 is an electrohydraulic controller, 14 is an induced blower, 15 is a control device,
16 is a skirt operating device (hydraulic device).

Scrap and hot metal 2 are charged as main raw materials into a converter 1, and high pressure oxygen is blown into the converter using a lance 3 from the top of the converter.
Refining hot metal into molten steel. This is called blowing. During this blowing, oxygen combines with carbon in the hot metal to generate waste gas mainly composed of CO gas. This waste gas is approximately 120
It has a high temperature of 0°C and contains a large amount of iron oxide dust of about 150 g/Nm'. Since this waste gas has a high temperature, the hood part 7 is water-cooled with a water-cooled pipe to protect the main body of the apparatus. On the other hand, in order to remove the dust in this waste gas, a primary dust collector (IDC) lla and a secondary dust collector (2DC) are installed.
llb is provided. Since these dust collectors use dust collecting water, the waste gas is rapidly cooled to a temperature of 70°C.
down to In order to remove dust from the waste gas, it is necessary to pass the gas through the first two dust collectors at high speed, and each dust collector 113.11b is equipped with a damper and serves as a throttling mechanism. Further, gas suction is performed by an induced fan 14. The gas pressure at the furnace mouth is called the furnace pressure (furnace pressure), and when it is detected by the furnace pressure detector 6,
The damper 12 in the secondary dust collector 11b is controlled using the control device 15.
It is controlled by moving the . Note that a battery controller 13 is normally used to drive this damper. The pressure inside the furnace is usually controlled close to atmospheric pressure to minimize the amount of gas blown out or the amount of atmospheric air sucked through the gap between the furnace mouth and the skirt (inner seal) 4a.
Normally, if the gap between the skirt 4a and the furnace mouth is about 200 μ, the furnace pressure is controlled between plus and minus several ta Hz O. However, if the skirt 4a is lowered and a device called an outer seal 4b that brings the skirt into close contact with the furnace body is operated, the gap at the furnace mouth will almost disappear. When operated in such a closed state, the fluctuation of the furnace pressure becomes large, and in the event of an abnormality, it can exceed + or - several hundred amH! It can be O. For this reason, the control device 15 performs various furnace pressure controls to ensure safe operation.

Here, surging prevention control of the blower 14 will be explained.

Generally, in a converter waste gas processing blower, when the air flow rate decreases to a flow rate below the peak of the flow rate-pressure characteristic line, a so-called surging phenomenon occurs in which the wind pressure and air volume vibrate and generate noise. When the airflow rate of the blower drops below the flow rate at which surging occurs, the opening of the damper or suction valve can be throttled to lower the blower's discharge pressure.
Since the flow rate-pressure characteristics of the blower change, it is possible to prevent surging from occurring. There is a control method that continuously controls the damper opening degree of the blower according to the air flow rate, but with this method, if the air flow rate constantly fluctuates, the damper has to be operated more frequently, so the damper There is a problem that the wear of the rotating parts of the motor increases and its lifespan becomes short.

In order to avoid such problems, there is also a method of controlling the damper opening degree in stages according to the amount of air blown by the blower. According to this method, the frequency of operation is lower than when the damper opening is controlled continuously, but each stepwise opening of the damper means that the air volume is larger than the flow rate set value corresponding to each opening. Therefore, if the air flow rate fluctuates near the set flow rate, the damper will repeatedly open and close, resulting in unstable operation.

In order to eliminate such drawbacks, the following surging prevention method has been proposed (Japanese Patent Publication No. 58-10598). FIG. 3 is a graph for explaining the method.

This means that the damper opening degree can be set to A (20%) or B depending on the air flow rate.
(40%), C (60%), D (80%).

When controlling in stages like E (100%), when the airflow rate decreases (F+, F3.FS+F?) and when it increases with respect to the airflow setting value corresponding to the switching point of the damper opening degree. By providing a hysteresis (for example, see ΔF) with a width of (F2, F4.F4, Fs), the frequency of operation of the damper is reduced and the operation is stabilized. In addition, S+, St, Sz, S4 in the same figure
．． Ss is the peak of the flow rate-pressure characteristic, and the right side is the safe area and the left side is the surging area.

Next, an embodiment of the present invention will be described with reference to FIG. In addition, the same figure (a) is a graph showing the surging prevention control characteristics according to the mff1-pressure characteristics of the blower, the same figure (b) is a graph showing the temporal change in the exhaust gas flow rate, the same figure (c)
is a graph showing changes in skirt height.

In other words, this embodiment performs surging prevention control in the same way as shown in Fig. 3, and when the air flow rate (waste gas flow rate) decreases over time, the damper opening degree is adjusted in stages according to the exhaust gas flow rate. change. For example, for flow rate F, the opening degree is changed from 100% to 80%, and for flow rate FS, the opening degree is changed from 80% to 60%.
In flow it F3, the opening degree is changed from 60% to 40%, and in flow IFl, the opening degree is changed from 40% to 20%. Here, assuming that the minimum value of the damper opening is set at 20%, surging will occur if the exhaust gas flow rate continues to decrease further than F. In other words, when the flow rate falls below the point S on the characteristic curve (E) at 20% opening in the graph of FIG. Therefore, a flow rate F0 that is slightly thicker than this is predetermined, and if the waste gas flow rate becomes less than this set value F0 and continues for a certain period of time (see t in the same figure (b)),
As shown in c), the skirt height is raised by, for example, hlmm. As a result, the amount of air sucked between the skirt and the furnace mouth increases, so the flow rate of the exhaust gas also increases. However, despite these operations, the gas generated in the furnace further decreases and the waste gas flow rate falls below F0 again, and if this continues for more than t seconds, the skirt height will rise again as shown in Figure (C). hams.The exhaust gas flow rate is monitored by the control device 15 based on the signal from the transmitter 5, and the state where the exhaust gas flow rate is below the predetermined value F0 is detected. When it is detected that the elongation continues for a predetermined period of time or more, the above-described control is performed via the skirt ff1 making device 16, which is a hydraulic device.

〔Effect of the invention〕

According to this invention, when performing surging prevention control in a converter waste gas treatment device that operates with the converter mouth and skirt sealed or in a substantially equivalent state, the waste gas flow rate is determined to be below a predetermined value. If this condition continues for more than a predetermined time, blowing is performed by simply raising the skirt to a predetermined height. ! This provides advantages that can greatly contribute to stable operation.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram for explaining the invention in detail, and FIG.
The figure is a schematic diagram showing a converter waste gas treatment apparatus in which the present invention is implemented, and FIG. 3 is a graph for explaining a conventional example of an improved surging prevention control method. Code explanation 1... Converter, 2... Hot metal and scrap, 3...
・Top blow lance, 4a...Skirt (inner seal), 4
b... Skirt (outer seal) 5... Waste gas flow rate transmitter, 6... Furnace pressure transmitter, 7... Hood part, 8...
... Blower Rodanba, 9... Damper controller, 10.
...Top safety valve, 11a...Primary dust collector, llb...
- Secondary dust collector, 13... Electrohydraulic controller, 14... Induced blower, 15... Control device, 16... Skirt operating device, A-4... Flow rate-pressure characteristic diagram, S, -SS...
・Vertex, F, ... Waste gas flow rate setting value. Agent Patent Attorney Akio Namiki Agent Patent Attorney Kiyoshi Matsuzaki Figure 1 Darkness υ)] 1113 Figure

Claims (1)

[Scope of Claims] Waste gas from the converter is treated and recovered by sealing the opening and skirt of the converter or in a state substantially equivalent to this, and
In a converter waste gas treatment device that performs surging prevention control of a blower, the waste gas flow rate is monitored, and when the waste gas flow rate remains below a predetermined value for a predetermined time or more, the skirt is raised to a predetermined height. A skirt control method in a converter waste gas treatment equipment, which is characterized by preventing surging of a blower.