JPS62359B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention continuously measures the flow rate and pressure of a large turbo compressor, compares the measured value with a reference value, and controls based on the difference value in order to avoid surge phenomena. , relates to a method of controlling a blow compressor for adjusting a blow-off valve, particularly a blow compressor for a blast furnace.

An example of a blowing system of a blast furnace to which such a control method is applied is shown in FIG. Produces a flow rate of air supply. Immediately downstream of the compressor 1, a blow-off valve 2 is arranged, which serves to discharge a portion of the charge air to the atmosphere if necessary. A non-return valve 3 and a control valve 4 are provided next to the blow-off valve 2, and a regenerator 5 is downstream thereof.
is provided, and only one such regenerator is shown in the drawing. The supply air then flows into the ring main pipe 6, from which it is blown up and enters the blast furnace 7 through the tuyere connection. The throat gas generated in the blast furnace then enters a purification system 9 through the throat 8 and from there into a throat gas system 10 . Currently, blast furnace 7
back pressure is very often controlled via this purification system. The pressure present in the throat gas system is controlled elsewhere as well, so that this throat gas system forms a huge reservoir of constant pressure.

FIG. 2 shows a group of characteristic curves of the compressor 1 combined with the characteristic curve of the low resistance of the blast furnace 7, in which the flow rate QA is shown on the horizontal axis and the discharge pressure PE is shown on the vertical axis. A is the resistance curve when the blow-off valve 2 is fully open, B and B' are the guide vane characteristics of 0% and 100%.
The operating point curve of the compressor 1 at the time of ing. During normal operation, the compressor 1 is started with the blow-off valve 2 fully open, thereby obtaining the operating point BP1. When the blow-off valve 2 is closed, the operating point of the compressor 1 moves along the curve B where the guide vane characteristic is 0% to the operating point BP2 where it intersects the resistance characteristic curve HO1 of the blast furnace 7. When the guide vanes are opened, the operating point of compressor 1 is the curve where the guide vane characteristics are 100%.
B' moves to BP3 where it intersects the resistance curve HO1.

The low resistance of blast furnace 7 changes from the characteristic curve HO1 to the characteristic curve.
When a high resistance value as shown by HO2 is reached, the operating point of the compressor 1 moves along the characteristic curve B' to an operating point BP4 that intersects the blowout curve C. Then, the blow-off valve 2 starts to open, and even if the compressor 1 maintains the pressure, the unnecessary supply air to the blast furnace 7 will be discharged to the atmosphere.

In this way, when the blowout curve C is reached, the blowoff valve 2
In order to ensure reliable opening, a control method using a controller using an electric circuit as shown in FIG. 3 has conventionally been used.

In this controller, the measured values of the flow rate QA and the pressure PE of the compressor 1 are converted into electrical signals, ie the measured values of the pressure PE are converted by a function generator 30. A signal difference value is formed in the customary manner in a comparator 32 and this difference value is applied as a control difference value to a surge limit controller 34, which then outputs a signal y for controlling the blow-off valve 2. provide. Note that 11 indicates an electromagnetic control valve.

However, such a control method has the disadvantage that the control is performed manually and that a surge phenomenon occurs in the compressor under conditions involving large pressure fluctuations. Although the occasional surge phenomenon was previously considered to be something that could be tolerated, it has recently been considered something that must be avoided.

Recent research shows that in the case of large blower compressors with a performance of about 25 MW, whenever a surge phenomenon occurs,
It has been found that damage to the blades occurs when the blades are subjected to a stress that exceeds their elastic limit. Current blast compressors for furnaces are designed from an efficiency point of view so that each compressor feeds a single blast furnace, especially in the event of a disruption or breakage, which can result in large pressure supply fluctuations and thus prevent the occurrence of surge phenomena. It is difficult.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a control method capable of eliminating the drawbacks of the conventional control methods and preventing surge phenomena in turbo compressors, particularly large turbo compressors.

According to the present invention, the above object is achieved by nonlinearly increasing the control difference value between the measured quantities of pressure and flow rate and the reference value, so that the control difference value becomes negative and the operating point of the compressor changes to the blowout curve. Moving beyond this and into the unacceptable region will be achieved in such a way that the control difference value increases.

Embodiments of the present invention are shown in FIGS. 4 to 6, and the present invention will be described in detail below with reference to these. Note that the same parts as those in FIG. 3 are given the same reference numerals.

As can be seen in FIG. 4, a nonlinear transfer element 40 is connected to the input side of the surge limit controller 34. When the control difference value XD formed by the comparator 32 is within the permissible region, it represents a positive value, and when within the non-permissible region, it represents a negative value. That is, when the control difference value for the surge limit controller 34 is positive, the operating point of the compressor 1 is in the allowable region on the lower right side of the blowout curve C; This means that it is within the permissible range.

The gain characteristic of the nonlinear transfer element 40 is at least 2
It is formed by two straight lines with increasing slope. The characteristic curve is interrupted due to entering the non-permissible region, in which case small negative control difference values caused by noise signals are eliminated unless they are of a predetermined magnitude.
A control difference value in the large, non-acceptable region allows a high gain to be obtained, for example an input to output ratio of 1:5, thereby increasing the interference of the surge limit controller 34, resulting in The blow-off valve 2 is rapidly opened to return the operating point of the compressor 1 to the permissible range.

Furthermore, the control difference value XD formed in the comparator 32
is compared with the limit value at the safety curve D in FIG. The distance is greater and is such that it is reached only in the event of a failure of the control system caused by improper control action. If the control difference value XD exceeds the limit value, the blow-off valve 2 is fully opened.

During the start-up phase, on the one hand, normal operating conditions are reached as quickly as possible, and on the other hand, high overshoot conditions, which can be triggered by the use of the normal surge limit controller 34 and which can give rise to surge effects, are ensured. , shall be removed as much as possible.

An embodiment for this is shown in FIG. 5, in which a starting circuit including a controllable integrator 50 is used,
This circuit operates as follows.

During startup of the compressor 1, the blow-off valve 2 is opened under control. While this control command continues, a variable factor of a certain magnitude is set in the integrator 50, and this magnitude is large enough to ensure generation of the opening command of the controller. The output voltage of this integrator 50 has a polarity opposite to the allowable control difference value. In this way, unacceptable control difference values are simulated to the surge limit controller 34, which responds accordingly. When the start-up of the compressor 1 is completed, the blow-off valve 2 is gradually closed until the operating point of the compressor 1 reaches the blow-off line C. The integrator 50 is cleared and its contained contents are discharged at an adjustable rate, and its output signal goes from its initial value to zero. In this way, the true control difference value takes effect in the surge intensity controller 34, which gradually controls the blowoff valve 2 to such an extent that the operating point of the compressor 1 reaches the blowout line C. close. By appropriately selecting the clearing speed of the integrator 50, it is ensured that the operating point of the compressor 1 does not exceed the blowout line C during the start-up step.

In the control method shown in said third figure, it is known that the surge limit controller 34 issues a manual control command in the form of a continuous electrical signal and an output signal, which output signal controls the regulating drive regulating the blow-off valve 2. useful for. In this case the blow-off valve 2 may also be opened manually, but it is ensured that it is not closed further than commanded by the surge limit controller 34. However, this system has the disadvantage that extremely rapid changes in the open-to-close manual control signal can result in an overshoot condition similar to that which would occur without the starting circuit shown in FIG.

To avoid this phenomenon, the manual control signal is compared with the output signal of the surge limit controller 34 in a comparator 60 shown in FIG. This difference value and the control difference value in comparator 32 are sent to circuit 62 for minimum value selection. The output signal of this circuit 62 is applied to the surge limit controller 34 in place of the control difference value. In this way, the blowoff valve 2 can be manually opened to a further extent, but it is ensured that it is not closed to such an extent that the operating point of the compressor 1 exceeds the blowoff curve C. However, surge limit controller 3
Since the output signal of 4 always corresponds to the actual position of the blow-off valve 2, the above-mentioned overshooting condition never occurs.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a blast furnace supply air system to which the method of the present invention is applied, Fig. 2 is a graph of a typical combination of the above blast furnace characteristics and compressor characteristics, and Fig. 3 is a diagram showing a typical combination of blast furnace characteristics and compressor characteristics used in the conventional control method. The typical electric circuit diagrams shown in Figs. 4, 5, and 6 are the 1st, 2nd,
FIG. 3 is a circuit diagram of a third embodiment. 1...Compressor, 2...Blower, 7...Blast furnace,
30...Function generator, 32...Comparator, 34...
Surge limit controller, 40...Nonlinear transfer element, 4
2... limit controller, 50... integrator, 60... comparator.

Claims (1)

[Claims] 1 Continuously measure the flow rate and pressure of the air supplied by the turbo compressor, and in order to prevent the occurrence of surge phenomena,
In a turbo compressor control method in which a blow-off valve is adjusted by surge limit control based on a control difference value between the measured value and a reference value, the control difference value is nonlinearly increased by a nonlinear transmission element; If the value becomes negative and the operating point of the compressor moves beyond the blowout line toward the surge limit curve, the gain increases and is transmitted to the surge limit controller. How to control a turbo compressor.