JPS5839204B2 - Furnace pressure control device in converter waste gas treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a furnace internal pressure control device in a converter such as an oxygen converter.

Generally, the waste gas generated during blowing in an oxygen converter is a valuable gas whose main component is carbon monoxide gas (CO gas), so it is cooled, cleaned to remove dust, and recovered as fuel. ing.

When CO gas is recovered without being combusted in this way, it is necessary to prevent air from flowing into the furnace through the gap between the converter mouth and the movable skirt installed between the converter mouth and the hood.

To achieve this, it is necessary to control the gas pressure in the hood so that it is approximately equal to atmospheric pressure, and for this reason, the gas pressure in the hood (hereinafter sometimes referred to as furnace pressure or simply furnace pressure) is detected. The exhaust gas flow rate is adjusted so that the pressure inside the furnace remains constant even if gas generation fluctuates irregularly within the furnace.

However, during blowing, if there is a sudden change in the reaction in the furnace due to the input of auxiliary materials, etc., the above-mentioned furnace pressure control is activated by a signal (
It may not be possible to follow up due to a delay in the detection or transmission of gas pressure or a delay in the response of the control end.

In this case, waste gas may inevitably blow out from the gap between the furnace mouth and the skirt, or conversely, excess air may be sucked into the furnace through the gap, resulting in wasteful combustion of CO gas. Operators manually raised and lowered the skirt position to adjust the gap.

Additionally, if slopping (slag and molten steel spews out) from the furnace mouth occurs during blowing, and metal adheres irregularly to the furnace mouth, the size of the gap will become substantially smaller even though the skirt position remains unchanged. .

There has been a conventional problem that during blowing, if the gap between the furnace mouth and the skirt (hereinafter simply referred to as the gap) changes, the above-mentioned furnace internal pressure control becomes unstable.

This point will be explained in detail below.

The PI or PID controller used for furnace pressure control has parameters such as Kc, which is a proportional gain for proportional operation, Ti, which is a specific number for integral operation, and Td, which is a time constant for differential operation. These parameters are set to different values depending on the process characteristics of the control system.

Therefore, when the process characteristics of the controlled system change, if these parameters are kept the same, the adjustment operation may become unstable.

In the above-mentioned furnace internal pressure control system, the change in the size of the gap changes the process characteristics.

Focusing only on the proportional operation of all controllers, if the gap is large enough, the exhaust gas flow rate control device (e.g. secondary damper)
Even when the controller is driven, the in-furnace pressure changes only a little because the air can easily flow into and out of the furnace mouth, so the proportional gain Kc of the controller may be large.

Conversely, if the gap is small, the furnace internal pressure will fluctuate greatly due to the drive of the exhaust gas flow rate control device, so the proportional gain of the controller must be small.

In the former case, that is, if the proportional gain Kc of the controller is small when the gap is large, the control operation of the controller becomes too slow, resulting in large fluctuations in the furnace pressure.

Therefore, a large amount of air flows in through the gap, leading to wasteful combustion of CO gas that should normally be recovered, or conversely, waste gas blows out from the gap and pollutes the environment.

Furthermore, if the proportional gain of the controller is large even though the gap is small, hunting will occur and the control operation will become unstable.

Conventional furnace internal pressure control devices for oxygen converters have the disadvantage that the above-mentioned problem occurs when the gap between the furnace mouth and the skirt changes, because the controller parameters are always constant. Ta.

This invention was made in order to solve the drawbacks of the conventional furnace internal pressure control device as described above, and therefore, an object of the invention is to adjust the skirt position during operation of a converter to improve the air inflow gap. An object of the present invention is to provide a furnace internal pressure control device that can operate stably even when the size of the furnace is changed.

The key point of the configuration of the present invention is that a change in the size of the gap is detected by determining the amount of air flowing into the furnace, and the parameters of the furnace pressure regulator are adjusted accordingly.

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

First, an overview of the configuration of the converter waste gas treatment equipment will be explained.

After putting scrap iron and molten pig iron 2 into converter 1, lance 3
Refining (this is called blowing) is performed by blowing high-pressure oxygen through the steel, and after blowing, the converter 1 is tilted to tap the steel.

During this blowing, the oxygen jet blown from the lance 3 reacts with the carbon in the molten pig iron, generating a large amount of CO-rich waste gas.

On the other hand, the collision surface of the oxygen jet against the steel bath becomes very high temperature, and since the Fe in the steel bath vaporizes, a large amount of iron oxide powder is also generated.

Therefore, waste gas treatment equipment can be divided into equipment that cools large amounts of high-temperature waste gas and equipment that collects dust.

A large amount of high-temperature, dusty waste gas generated as described above is sucked in by the induced blower 11 and flows through the flue. At this time, it is cooled in a gas cooler 7 consisting of a group of cooling water pipes, for example. After that, coarse dust is collected in the primary dust collector 6, and final collection of fine dust is performed in the subsequent secondary dust collector 8, and the thus dust-removed and purified waste gas is passed through the induced blower 11. , and is recovered as fuel in a gas holder (not shown).

However, in the converter 1, a large amount of waste gas is generated during the middle stage of blowing, but the amount generated is small at the early stage and final stage.

Further, during blowing, the amount of waste gas generated varies even if auxiliary raw materials are added or the amount of oxygen blown from the lance 3 is changed.

Due to such fluctuations in the amount of waste gas generated, the gas pressure within the hood 5 also fluctuates.

Therefore, the flow rate of the waste gas is controlled so that the gas pressure within the hood 5 is within an appropriate range.

That is, the gas pressure inside the hood 5 is detected, and the in-furnace transmitter 12
from there to the controller 14.

The controller 14 compares the gas pressure with a preset value, and sends an operation output signal to the damper operator 15 so that the difference becomes zero, and controls the opening/closing operation of the secondary damper 9 to eliminate waste. Adjust gas flow rate.

However, if the reaction inside the furnace fluctuates rapidly, the above-mentioned furnace pressure control cannot keep up, and waste gas blows out from the gap between the furnace mouth and the skirt 4, or excess air is sucked into the furnace, resulting in waste of CO gas. This could lead to severe combustion.

As previously explained, the operator may adjust the size of the gap by moving the skirt 4 up and down.

In the present invention, the parameters of the controller 14 are adjusted in such a case, that is, when the gap between the furnace mouth and the skirt 4 changes, so that the furnace internal pressure control does not become unstable.

The size of the change in the gap can be determined as a function of the amount of air flowing into the furnace from the gap.

One method for calculating the amount of air is to calculate the height H of the gap between the furnace mouth and the skirt 4 (also referred to as skirt height) using the skirt position meter 13, and calculate the amount of air in the gap as a function of this mechanical dimension H. Find the flow path resistance (sometimes called skirt resistance).

On the other hand, since the gas pressure in the hood 5 is determined by the furnace pressure transmitter 12, the amount of air flowing into the gap can be calculated from this gas pressure and the skirt resistance.

The calculator 16 has the function of performing the above-mentioned calculations when given the gas pressure from the furnace pressure transmitter 12 and the skirt height H from the skirt position meter 13.

Based on the result of the calculation in the calculator 16, the parameters of the controller 14 can be adjusted to prevent the reactor pressure control system from becoming unstable.

Inflow air amount QA from skirt height H and hood gas pressure P
The following formula is used to calculate .

However, R5 is the skirt resistance, A is a coefficient, and B is a constant.

That is, the skirt resistance Rs may be determined as a function of the skirt height H using equation (2), and then the amount of incoming air may be determined using equation (1).

This method does not involve a time delay during measurement, so the amount of air can be calculated quickly, but it has the disadvantage of large errors.

That is, in the above equation, the skirt resistance Rs is equal to the skirt height H
However, during actual operation of a converter, slopping occurs and metal adheres unevenly to the furnace mouth, so the skirt resistance Rs is not necessarily a function of the skirt height H. It is.

FIG. 2 is a schematic configuration diagram showing an embodiment of the pond of the present invention.

The difference from FIG. 1 is that a gas analyzer 17 is provided in front of the primary precipitator 6, and a venturi 1 for measuring the flow rate of waste gas is provided.
The point is that a waste gas flow rate transmitter 18 is provided to measure the flow rate at zero.

Then, the calculator 16 calculates the amount of air flowing into the furnace from the result of the exhaust gas analysis in the gas analyzer 17 and the exhaust gas flow rate from the exhaust gas flow transmitter 18, and based on the result, the parameters of the controller 14 are calculated. is being adjusted.

The inflow air amount QA is the exhaust gas flow rate as C0% of the F1 exhaust gas.
, CO2% and H2% respectively as XC01XCO2 and XH
If it is set to 2, it can be calculated using the following formula.

This method has less error than the method shown in FIG. 1, but the difference is that it requires a time delay of nearly 20 seconds for gas analysis.

However, things like adjusting the parameters of a controller
Since this is not something to be done in a hurry, the above-mentioned time delay is not much of a problem.

Now, in Figure 1 (or Figure 2), the secondary tamper 9
The range in which the gas pressure P in the hood 5 changes when the opening degree of the hood 5 is changed is large when the skirt height H is low and the gap is small, and small when the skirt height H is high and the gap is large.

This means that in the control loop composed of the controller 14, secondary damper 9, and furnace pressure transmitter 12, the system gain Kp varies depending on the skirt height H.

On the other hand, since it is desirable to maintain the control roof b loop gain at a constant optimum value, the proportional gain Kc of the controller 14
It is better to make it smaller as the gain Kp of the system increases, and increase it as the gain Kp becomes smaller.

Based on this idea, the proportional gain Kc of the controller is changed in response to changes in the system gain Kp.

In order to know the change in the gain Kp of the system, the amount QA of air flowing into the furnace through the gap and the differential pressure △P between the atmospheric pressure and the gas pressure inside the hood 5 are the following functions for Kp. You can take advantage of that.

That is, the gain Kp of the (1) system and the inflow air amount QA are inversely proportional, and the gain Kp of the (2) system and the differential pressure ΔP are proportional.

When using the function (1), the amount of incoming air calculated by the calculator 14 is used, as previously explained with reference to FIGS. 1 and 2.

If the operating pressure of the furnace (set furnace internal pressure) has also been changed,
Since the relationship (2) is used, the gas pressure inside the hood is also used.

In this way, the change in the system gain Kp is estimated, and the proportional gain Kc of the controller 14, which has already been adjusted for the skirt height, is made to correspond to the change in the system gain Kp.

The correspondence is based on the following formula. However, Kcm is the controller 1
Kpo is the proportional gain that will be used as a reference from now on when the proportional gain is determined by first adjusting Kpo.

Next, the effects of this invention will be explained with reference to FIG.

Figure 3A is a time chart showing the furnace pressure fluctuation situation when the proportional gain Kc of the controller is determined with the skirt height H set high, and the skirt height H is lowered without implementing the present invention. It turns out that hunting is occurring.

The figure above shows the furnace pressure fluctuation when the skirt height H is actually high, with the proportional gain Kc of the controller determined with the skirt height H high, and of course the control operation is good. .

C is a diagram showing the furnace internal pressure fluctuation situation when the skirt height H is low, and the proportional gain Kc of the controller is determined, and the skirt height is actually low, and the control operation is good.

2 is a diagram showing the furnace pressure fluctuation situation when the proportional gain Kc of the controller is determined when the skirt height H is low and the skirt height is increased without implementing the present invention.

2 seems to be good if it is proportional to 8, but since it should normally be performed well like the mouth, it can be said that the control operation is not good in comparison.

E is a diagram showing the situation in which the present invention is implemented, and E is a diagram showing the fluctuation of the furnace pressure when the skirt height is low, and the proportional gain Kc of the controller is also adapted to the skirt height (low). As in case C, good control operation is performed.

This is a diagram showing the furnace pressure fluctuation situation when the skirt height H is high.The proportional gain Kc of the controller is also adapted to the skirt height (high) according to the present invention, so it can be controlled as well as the mouth. It can be seen that the action is taking place.

As explained above, this invention has the advantage that even if the height of the skirt changes, the furnace internal pressure can always be controlled stably, and as a result, excess air flows in through the gap, and CO gas is wasted. This has the advantage of increasing waste gas recovery efficiency and contributing to energy conservation, since it also avoids the situation of combustion.

In the description of the embodiment, a case has been described in which the proportional gain of the controller is adjusted, but it goes without saying that the integral time constant and differential time constant can also be adjusted based on the same principle as necessary.

Furthermore, it goes without saying that the present invention cannot be carried out unless the controller is of a swing type that automatically changes parameters in response to the output of a computing unit.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.
FIG. 2 is a schematic configuration diagram showing an embodiment of the pond. Figure 3 is a time chart showing fluctuations in furnace pressure.
FIG. 3 is a diagram for explaining the invention in detail. In the figure, 1 is a converter, 2 is scrap iron and molten pig iron, and 3 is a converter.
is a lance, 4 is a skirt, 5 is a hood, 6 is a primary dust collector, 7 is a gas cooler, 8 is a secondary dust collector, 9 is a secondary damper,
10 is a venturi for measuring the flow rate of waste gas, 11 is an induced blower, 12 is a furnace pressure transmitter, 13 is a skirt position meter, 14 is a furnace pressure regulator, 15 is a damper operating device, 16 is a computing device, 17
18 indicates a gas analyzer, and 18 indicates a waste gas flow rate transmitter.

Claims (1)

[Claims] 1 Furnace pressure detection means, a furnace pressure regulator that compares the detected furnace pressure with a set value and sends out a control signal according to the deviation, and a furnace pressure regulator that generates pressure from inside the furnace in response to the control signal from the controller. In a furnace pressure control device in a converter waste gas treatment device, which comprises a means for controlling the flow rate of waste gas and is configured to control the furnace internal pressure at a constant level, from the gap between the furnace opening of the converter and the skirt covering the furnace opening. A means for measuring the amount of air sucked into the furnace, and a variation in the amount of air sucked by the measuring means is detected, and when a change occurs in the characteristic parameters of the waste gas treatment device, adapting to the change. A reactor pressure control system comprising means for adjusting the operating parameters of the controller as follows.