JPS6025609B2 - Control method for blast furnace exhaust gas energy recovery plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for controlling the top pressure of a blast furnace while recovering blast furnace exhaust gas energy using a turbine.

Conventionally, a pressure control valve and a pressure control valve for adjusting the furnace top pressure and a turbine for recovering exhaust gas energy were arranged in parallel in the exhaust gas path from the blast furnace, and an emergency shutoff valve and a control valve were also installed on the supply side of the turbine. A pressure control valve is provided, and the pressure control valve, range adjustment valve, and speed control valve are controlled by the output signal of the pressure regulator according to the top pressure of the blast furnace, and the top pressure of the furnace is controlled while recovering blast furnace exhaust gas energy. There are known ways to do this.

Fluctuations in the furnace top pressure must be kept as small as possible, and fluctuations caused by various disturbances must be kept within a few percent.However, in the conventional furnace top pressure control system described above, it is necessary to maintain the furnace top pressure at a constant level. In addition to disturbances such as raw material input, blast furnace blow-through, taper drop, and slip, fluctuations in furnace top pressure due to turbine tripping are new and biggest problems when exhaust gas energy is recovered using a turbine.

When the turbine trips, the emergency shutoff valve is fully closed for a short period of time (approximately 0.0 sec) to protect the turbine and the generator directly connected to it. In order to keep it as small as possible,
The opening degrees of the pressure regulating valve and the pressure regulating valve are correspondingly increased in a short time to increase the total gas flow rate of these valves (referred to as septan valves).

) side. However, because the range adjustment valve is configured to operate when a limit switch detects when the pressure adjustment valve deviates from its maximum opening, which is easy to control, there is a limit to the speed at which the range can increase. The furnace top pressure rises considerably later than the closing speed. If the gain of the control system is increased in order to suppress the rise in the furnace top pressure due to such turbine tripping, hunting is likely to occur, which deteriorates the stability of the furnace top pressure control system.

Alternatively, increasing the operating speed of the septan valve is the optimal value for the gain of the pressure regulator and the operating speed of the pressure regulating valve when controlling the furnace top pressure with the turbine disconnected. If you increase the operating speed,
This makes the furnace top pressure control characteristics during normal operation unstable. The purpose of the present invention is to prevent abnormal increases in furnace top pressure, and the furnace top pressure control function that operates the pressure control valve at a high gain only when the furnace top pressure increases slightly is replaced by conventional control. In addition to the system, a control method is provided that maintains the furnace top pressure constant not only against turbine trips but also against blast furnace blow-through and other disturbances on the blast furnace side. For the example,
This will be explained below with reference to the drawings.

In FIG. 1, the exhaust gas from the blast furnace 1 is removed by a dust collector 2, a ventilator scrubber 3, 3', etc., and then the pressure regulating valves 4, 5 arranged in parallel and the pressure regulating valves 4, 5 are removed. A turbine 7 is connected in parallel to the range control valve 6 and for recovering exhaust gas energy, and a generator 8 is directly connected to the turbine 7.

On the supply side of the turbine 7, there is a shutoff valve 9 and an emergency shutoff valve 1.
0 and a regulating valve 11 are arranged in series, and a shutoff valve 12 is provided on the discharge side. The load of the turbine 7 is detected at the turbine shaft, and the governor 1 is detected by the signal from the signal transmitter 13.
4 and a signal low selector 15 to control the Liaoyuan valve 11. On the other hand, the furnace top pressure of the blast furnace 1 is determined by the furnace top pressure transmitters 16 and 1.
6' is selected by the signal selector 17 and the first
The signal is sent to a pressure regulator 18, and the output signal of this regulator 18 is sent to a signal switch 19.

A contact 19a of the stub 19 is connected to a subtracter 20 and a signal limiter 21, and the limiter 21 is further connected to the signal low selector 15. The selector 15 is connected to a subtracter 20', and the subtracter 20 is connected to the contact 19 of the signal switch 19.
b and to signal limiters 22 and 23. The restrictor 22 is further connected to the pressure regulating valve 4, and the restrictor 23 is connected to the pressure regulating valve 5 via a proportional bias setting device 24. The pressure control valves 4 and 5 are provided with limit switches 25 and 26, respectively, which are connected to a relay box 27, which is connected to a motor drive signal generator 28 and a signal high level selector 29, which will be described later.
It is connected to the range adjustment valve 6 via.

The characteristics of the present invention are that the control system for the furnace top pressure in the above-mentioned blast furnace exhaust gas energy recovery plant has a fast response and a high The reason lies in the addition of a furnace top pressure control function that operates the range control valve 6 based on the gain.

That is, a separate second pressure regulator 30 is connected in parallel with the first pressure regulator 18, and a signal high level selector 29 is interposed between the motor drive signal generator 28 and the engine control valve 6.
A second pressure regulator 30 is connected to this. The manual setting device 31 is then connected to the first pressure regulator 18 and the second pressure regulator 30 via the bias setting device 32, respectively. Second
The set value of the pressure regulator 30 is set slightly higher [by 10 B] than the first pressure regulator 18 by the bias setting device 32, and is transmitted from this second pressure regulator 30 to the signal high level selector 29. The signal x is x
:K (e1Td group 10Ti'edt) where K is the gain of the second pressure regulator, Td is the differential time, Ti is the integration time, and e is the deviation.

On the other hand, from the motor drive signal generator 28 to the signal high level selector 2
The signal x' transmitted to 9 is x':A as shown in FIG.
-(t) Given by equation '21.

Here, A represents the rate (a type of gain) of the motor drive signal generator 28, and t represents the time starting from the time when the limit switch 26 detects the high level signal. The furnace top pressure is detected by the furnace top pressure transmitters 16, 16', selected by the signal selector 17, and becomes an input signal for the first pressure regulator 18 and the second pressure regulator 30.

However, during normal operation of the blast furnace, the second pressure regulator 30 outputs a full open signal because it is set higher by [10 B], and the control system is activated only by the signal from the first pressure regulator 18. Function. During turbine trip (Tt in Figure 3)
time), the output signal of the first pressure regulator 18 is the signal cutter 1
9 to the contact 19b side, and this signal level is the second
If it is larger than point H in the figure (in most cases it will be larger), the limit switch 26 activates the signal generator 28 to generate a signal x'=A・(t) (formula [2}), and gradually The opening degree of the range adjustment valve 6 is increased.

After the time condition mh, the output signal x (formula '11) from the second pressure regulator 30 becomes higher, and the signal high level selector 29 selects this, so the range adjustment valve 6 follows this x. and increase the opening at a fast speed. Therefore, the furnace top pressure, which had only begun to rise due to the turbine trip, decreases when it rises slightly, and when the furnace top pressure approaches the target value, x rapidly decreases, and the T point (Fig. 3) ) After that, the selector 29 selects the signal x' from the signal generator 28 to return to the normal control system. That is, FIG. 3 shows the relationship between the output x of the second pressure regulator 30 and the output x of the motor drive signal generator 28 from the turbine trip time Tt, and these two signals are selected as shown in FIG. The range adjustment valve 6 is operated via the device 29. Therefore, the range adjustment valve 6 outputs the output x of the second pressure regulator 30 between time m and TI.
before time Th or time Ti
Thereafter, the movement follows the diagram of the output x of the motor drive signal generator 28. Note that the value set by the bias setter 32 [10B] can be changed sequentially using a trib signal or the like, if necessary, and restored at an appropriate time.

Further, FIG. 2 shows the opening degree characteristics of the pressure regulating valves, that is, the opening degree characteristics of the pressure regulating valves 4 and 5 with respect to the operation signal level. Note that the L and H points indicate the operating point of the mitt switch, which detects that the valve is out of a range with good controllability. To be more specific, FIG. 2 is a graph showing the relationship between the pressure regulating valves. When the regulating valve 11 is fully closed during a turbine trip, the pressure regulating valve 4 is fully opened, and the pressure regulating valve 5 is at an intermediate level. Become. At this time, if the pressure at the top of the furnace increases, the range valve 6 opens to suppress the pressure. This relationship is shown in FIG. 3. That is, the pressure regulating valves 4 and 5 are operated in a split manner, and only the pressure regulating valve 4 opens until the operating signal reaches a certain level, and when the signal level exceeds the signal level determined by the setting of the bias setting device, the pressure regulating valve 5 begins to open.

Note that after the pressure regulating valve 4 reaches 100% opening, the pressure regulating valve 4 remains fully open as the signal increases. Further, a butterfly valve is generally used as the pressure regulating valve, and the control characteristics of this valve, that is, the Cv value curve, exhibits an S-shape. Therefore, by installing two pressure regulating valves in parallel and selecting the bias setting appropriately, it is possible to expand the range of the combined Cv value that is close to a straight line, and this range is called the range with good controllability. There is. Furthermore, as mentioned above, FIG. 2 is a graph showing the opening characteristics of the pressure regulating valve, and the signal level of the shaft corresponds to the output signal of the pressure regulator 18, and this signal is transmitted to the signal controller 22. , 23 and proportional bias setter 24
The signals are distributed as operation signals for the pressure regulating valves 4 and 5.

That is, FIG. 2 shows the relationship characteristics of the pressure regulating valve, with the valve relationship corresponding to the output signal level of the pressure regulator 18 taken on the vertical axis.

Therefore, the output of the pressure regulator 18 is controlled by the signal controllers 22 and 23.
There is no problem in connecting the pressure control valves 25 and 26 to the pressure control valves 25 and 26 as operation signals. According to the control method of the present invention, when the top pressure of the furnace rises slightly due to a disturbance such as a turbine trip, the output signal of the second pressure regulator, which has a quick response and a high gain, increases the range control valve. Since the flow rate of the exhaust gas whose supply to the turbine has been cut off by the emergency shutoff valve is quickly made to flow to the pressure control valve, it is possible to prevent an abnormal rise in the furnace top pressure at the time of a turbine trip or the like.

In addition, since the control system using the second pressure regulator is separated and does not function in normal times, the stability of the original furnace top pressure control system is not impaired.

[Brief explanation of drawings]

The figures show an embodiment of the present invention, Fig. 1 is a diagram showing the control system, Fig. 2 is a graph showing the relationship characteristics of the pressure regulating valve, and Fig. 3 is a graph showing the signal characteristics of the pressure regulating valve. It is. 1... Blast furnace, 4, 5... Pressure control valve, 6.
... Range adjustment valve, 7 ... Turbine, 8
... Generator, 10 ... Emergency shutoff valve, 11 ... Speed control valve, 16, I6' ... Furnace top pressure transmitter, 18
......First pressure regulator, 25, 26...Limit switch, 27...Relay box, 28...Motor drive signal generator, 29...Signal high level selector, 30
...Second pressure regulator, 31...Manual setting device, 32...Bias setting device. Figure 2 Figure 3 Snake

Claims (1)

[Claims] 1 A pressure control valve and a range control valve for adjusting the furnace top pressure and a turbine for recovering exhaust gas energy are arranged in parallel in the exhaust gas path of the blast furnace, and an emergency shutoff valve and a speed control valve are installed on the supply side of the turbine. In the method of controlling the furnace top pressure while recovering the blast furnace exhaust gas energy by providing a , disposing another second pressure regulator in parallel with the pressure regulator, and connecting the second pressure regulator to the range adjustment valve via a signal high level selector, The set value is set slightly higher than the set value of the pressure regulator and has a high gain, and when the furnace top pressure rises slightly from normal, the output signal from the second pressure regulator is set to a high level. A method for controlling a blast furnace exhaust gas energy recovery plant, characterized in that a selection is made using a selector and a range adjustment valve is controlled.