JPS6129217B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for recovering the energy of flowing water head in a blast furnace cooling system, and in particular, for recovering the energy of cooling water in a blast furnace cooling system that has a relatively low head and fluctuates in flow rate as electrical energy to the power source side. The present invention relates to a method and device for recovering power.

BACKGROUND OF THE INVENTION Flowing water is used in various industrial facilities to cool or purify equipment, and the water is pumped up by a pump or the like and sent under pressure to the required facility location to perform the desired cooling or other effects. In these running water utilization facilities, the pumped water itself has potential energy, and the pumped water itself has large pressure energy. A suitable example of this type of facility is a steel mill, where large amounts of running water are used to cool high-rise buildings such as blast furnaces, and large amounts of water are also used for slag equipment other than blast furnaces. However, in normal cases, these running waters are used for cooling or purification and then are allowed to naturally fall, a portion of which is pumped up again, and a portion of which is discharged. Therefore, in the past, the reality was that a huge amount of potential energy or pressure energy contained in the flowing water was wasted without any use.

Conventionally, it has been considered to use the aforementioned running water to generate hydroelectric power and recover the aforementioned energy as electrical energy, but since the running water in these facilities has a low head and large fluctuations in flow rate, the use of regular generators is not possible. There is a problem in that the overall efficiency is poor and it is difficult to put it into practical use, and in particular, with ordinary synchronous generators, it is difficult to recover electricity profitably from the aforementioned flowing water with a low head and fluctuating flow rate. Furthermore, it has been proposed to produce stable power generation by temporarily storing flowing water in a reservoir, but this has the problem of increasing the size of the equipment and reducing the efficiency of cooling or purifying the flowing water itself.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a profitable power recovery method that efficiently recovers the cooling water energy of the blast furnace cooling system as electric energy by providing a simple additional mechanism. and equipment.

In order to achieve the above object, the method according to the present invention converts flowing water energy into rotational energy of a water wheel, and converts the rotational energy of the water wheel into electric energy by over-rotating the induction motor beyond the synchronous speed, and converting the rotational energy of the water wheel into electrical energy on the power source side. When the rotational speed of the induction motor decreases below the synchronous speed, the connection between the induction motor and the power source is cut off, and the flow rate of the flowing water is controlled to control the rotational speed of the induction motor. shall be.

Further, the device according to the present invention includes a water wheel installed in a water channel and rotated by flowing water, a control valve that controls the amount of water sulfur that rotates the water wheel, a rotor connected to the water wheel, and a rotor that can be connected to a power source. An induction motor having a stator, a switch that controls the connection between the stator of the induction motor and the power supply side, and a switching signal that opens the switch when the rotational speed of the induction motor drops below the synchronous speed. a switching signal detector for converting the flowing water energy into electrical energy by closing the switch and causing the induction motor to act as an induction generator only when the flowing water energy is enough to rotate the induction motor in the generator region. It is characterized by being recovered to the power source side.

Preferred embodiments of the present invention will be described below based on the drawings.

In the following description, the cooling water of the blast furnace cooling system includes cooling water for blast furnace bodies, cooling water used for blast furnace auxiliary equipment and peripheral equipment, or cooling water for a hot blast furnace.

FIG. 1 shows an embodiment in which a flowing water head energy recovery device according to the present invention is attached to a flow channel for cooling a blast furnace in a steelworks. It is falling with a . In the present invention, in order to convert this flowing water energy into rotational energy, a water wheel 14 is provided in a part of the flowing water channel 10, and the water wheel 14 is rotationally driven by the flowing water 12. Then, on the upstream side from the water wheel 14 of the waterway 10, there is flowing water 1.
A control valve 16 is provided that can control the flow rate of 2. An induction motor 18 is connected to the water turbine 14, and more specifically, a rotor 18a of the induction motor 18 is connected to a rotating shaft 14a of the water turbine 14, so that the rotational energy of the water turbine 14 is converted into electrical energy of the induction motor 18. converted. induction motor 1
The stator 8 is electrically connected to the power supply side, in the embodiment, a commercial frequency power supply 20 via a switch 22, and the connection state between the induction motor 18 and the power supply 20 is changed by the switching action of the switch 22. It is understood that the induction motor 18 acts as an electric motor when its rotational speed is below the synchronous speed, and acts as a generator when it exceeds the synchronous speed. In addition, the coupling phase order of the stator winding of the induction motor 18 is the water turbine 14.
is set in the same direction as the rotation direction.

Here, the speed (slip S), torque (T), and power (W) characteristics of the induction motor used in the present invention will be explained with reference to FIG.

Generally, when an induction motor is operating under a load, if the load is gradually reduced, the slip S will also decrease and the speed will approach the synchronous speed _ns . Under ideal no-load conditions, the slip S will be zero and the synchronous speed will reach the synchronous speed _ns . and rotate.
When mechanical force is applied to the motor shaft to rotate it in the same direction as before and faster than the synchronous speed, the direction in which the magnetic flux of the rotor conductor is cut is also reversed, and the electromotive force induced in the rotor winding is goes in the opposite direction. Therefore, since the rotor current also flows in the opposite direction, the torque is also opposite to the motorized region, producing a torque that opposes rotation. As described above, when applying mechanical force to an induction motor and rotating it in the same rotational direction as the motor faster than the synchronous speed, this motor works to generate electric power by taking mechanical force, that is, it acts as an induction motor. Flowing water as mechanical power12
By utilizing the rotation of the water wheel 14, it is possible to recover flowing water energy to the power source 20 side as electrical energy. At this time, the rotation of the induction motor is stable to the point where the reverse torque that attempts to rotate at a synchronous speed or less and the torque generated by the water turbine 14 that attempts to rotate at a synchronous speed or higher are balanced, and the motor 18 functions as an induction generator. I will continue driving.

Now, when the switch 22 is closed with no flowing water 12 in the water channel 10, the induction motor 18 operates as an electric motor at a synchronous speed n _s determined by its polarity, and the water turbine 1
It rotates with a slip S according to the no-load torque on the 4th side,
In Fig. 2, the electric motor generated torque T and the water turbine 14
The intersection with the no-load torque T _l becomes the operating point, the speed at this time is n _n , and the torque and power used are T
_n , W _n .

Next, when the flowing water 12 is introduced into the flowing waterway 10 and dropped, and the water wheel 14 is rotated with a torque greater than or equal to the no-load torque T _n , the rotational speed of the induction motor 18 at this time is n _G
Thus, a generator region that acts as the induction generator described above is obtained. The operating point at this time is determined by the intersection of the torque curve T _l ' of the water turbine 14 rotated by the flowing water 12 and the torque T, and the rotation speed is n _G.
At this time, the reverse generated torque becomes T _G , and the regenerated power becomes W _G , and this power W _G is recovered to the power source 20 .

As described above, according to the present invention, it is possible to recover electric power with a small driving force even from flowing water with a low head and flow rate fluctuation using the general-purpose induction motor 18, and it is possible to recover electric power with a small driving force using the general-purpose induction motor 18. Compared to the conventional method, it is possible to operate at a speed other than the synchronous speed, there is no synchronization phenomenon, and stable power recovery can be performed, and the start-up synchronization operation is easy and an exciter is not required. This feature makes it possible to perform simple and profitable power recovery.

Of course, in the present invention as well, the induction motor 18 must be rotated at a speed higher than the synchronous speed using flowing water energy, and when this speed decreases below the synchronous speed, the method of the present invention Since the induction motor 18 and the power source 20 must be electrically connected only when the energy of the flowing water exceeds a predetermined value, the induction motor 18 and the power source 20 must be electrically connected. For this purpose, the above-mentioned switch 2
2.Accurate opening/closing control must be performed. Furthermore, in the actual usage state, it is preferable in the present invention to rotate the electric motor 18 in a predetermined rotational speed region selected in the generator region, and the speed n _M at which the theoretical maximum power can be recovered is the power Although it is the most efficient for recovery, at this speed n _M , the water turbine 14
There is a drawback that the equilibrium point between the torque T _l ' of the motor 18 and the torque T generated by the electric motor 18 becomes two or more points, making the operation unstable, and the water turbine 14 runs away, and in extreme cases, the generator 18 enters the braking region. Therefore, in practice, stable operation is preferably controlled within a speed range of a speed n _k or less, which is slightly lower than the speed n _M and is indicated by α.

An embodiment of the present invention for performing each of the above-mentioned controls will be described below with reference to FIG.

In order to perform power recovery control, a control device 24 is provided in the embodiment, and the control device 24 includes an operation panel 26 to which operation command signals from an operator are supplied.
is connected. The output of the control device 24 is supplied to the control valve 16 and the switch 22, and controls the flow rate of the flowing water 12 by the opening degree of the control valve 16, and also controls the opening and closing of the switch 22 to connect the electric motor 18 and the power source 20. control. In the present invention, a switching signal detector is provided that detects a switching signal that opens the switch 22 by detecting that the rotational speed of the electric motor 18 has decreased below the synchronous speed. consists of a power flow direction detector 28, which directly detects whether the motor 18 is in the motor region or the generator region, and controls the opening and closing of the switch 22 via the control device 24 based on this detection signal. That is, when the rotation speed of the electric motor 18 is below the synchronous speed, the drive current is supplied from the power supply 20 to the electric motor 18;
When the rotational speed of the motor 18 is equal to or higher than the synchronous speed, regenerative power is recovered from the electric motor 18 to the power source 20. Therefore, the switching signal can be detected by detecting the current direction of the connection line between the electric motor 18 and the power source 20. I can do it.
The power flow direction detector 28 in the embodiment includes an instrument transformer 30 and an instrument current transformer 32, and uses the voltage and current values to operate a wattmeter or a watt-hour meter, thereby controlling the rotation of the needle or disk of these meters. By detecting the direction, it becomes possible to detect the current direction. Of course, in the present invention, the power flow direction detector 28 can also waveform shape the power value and current value and identify the power flow direction based on the phase difference between the two waveforms. As described above, the control device 24 controls the opening and closing of the switch 22 based on the switching signal from the power flow direction detector 28 to control the opening and closing of the electric motor 1.
8 can be operated only in the generator area. Note that the control device 24 is provided with a timer circuit,
It is preferable to have a configuration in which a switching signal is output when the power flow direction continues for a certain set time or more to eliminate subtle hunting near the synchronous speed.

In the embodiment, a pressure switch 34 is provided to detect the flow rate of the flowing water 12 in the flow channel 10, and is supplied as a flow rate signal to the control device 24, and the rotational speed of the electric motor 18 is controlled by a tachometer generator or the like. It is detected by a detector 36 and supplied to the control device 24.

A preferred embodiment of the present invention has the above configuration,
The energy recovery effect will be explained in detail below.

When an operation command is input to the operation panel 26 while the switch 22 is in an open state, the control device 24 receives flow rate or pressure information of the flowing water 12 based on a pressure signal from the pressure switch 34. At the start of operation, the control valve 16 is in a fully closed state, and together with the operation command, the control device 24 gradually opens the control valve 16. The opening control speed at this time is suppressed to a speed at which there is no delay in increasing the rotational speed of the water turbine 14. With the opening operation of the control valve 16, the water turbine 14
When the rotor of the electric motor 18 starts rotating and its rotational speed reaches a starting speed n _l set below the synchronous speed n _s , the control device 24 gives a closing command to the switch 22 and closes the switch 22 . Electric motor 1
8 is electrically connected to a power source 20. The starting speed n _l is the speed at which the electric motor 18 can enter the generator region by the mechanical force applied from the water turbine 14,
When the stator winding of the motor 18 is open, this speed n _l is lower than the synchronous speed n _s , but stator current is supplied from the power supply 20 to the motor 18 by closing the switch 22. Immediately, the rotation speed of the electric motor 18 becomes equal to or higher than the synchronous speed n _s , and the rotation speed of the electric motor 18
starts functioning as an induction generator and can recover running water energy to the power source 20 side as electrical energy. The starting speed n _l is determined experimentally, and the reference setting voltage corresponding to this starting speed n _l and the detection signal from the speed detector 36 are transmitted to the control device 24 .
A comparison operation is performed by , and a closing control signal for the switch 22 is output.

As described above, the control valve 16 continues to open until the rotational speed reaches the aforementioned n _k while continuing the power recovery action in the generator region. and,
When the rotational speed of the electric motor 18 becomes equal to or higher than n _k due to an increase in the opening degree of the control valve 16 or an increase in the flow rate of the flowing water 12, the control device 24 adjusts the output of the speed detector 36 at this time and the set voltage corresponding to the speed n _k A closing operation command is given to the control valve 16, and this closing operation is continued until the rotational speed becomes equal to or less than n _k . In order to prevent hunting from occurring during the opening/closing operation of the control valve 16 at this speed n _k , it is preferable to provide hysteresis regions n _k1 and n _k2 before and after the speed n _k .

As described above, according to the method of the present invention, electric power can be recovered when the speed of the electric motor 18 is in the range from n _s to n _k , and especially when the flow rate of the running water 12 is sufficient, the electric motor 18 can be recovered almost immediately. By rotating at a speed of n _k , it is possible to efficiently recover power.

In the power recovery state, if it becomes impossible to maintain the generator area even if the control valve 16 is fully opened due to a decrease in the energy of the flowing water 12, such as a decrease in flow rate or pressure, the power flow direction detector 28 sends a signal to the control device 24. A switching signal is supplied to the switch 22 to open the switch 22, thereby preventing the motor 18 from operating in the motor region and drawing unnecessary power from the power supply 20.

As described above, in the present invention, only when the flowing water energy is enough to rotate the induction motor in the generator region, the switch 22 is closed, the induction motor 18 acts as an induction generator, and the flowing water energy is converted into electricity. It becomes possible to recover energy to the power source 20 side.

In the embodiment, when a stop command is input to the operation panel 26, the switch 22 is immediately opened and the control valve 16 is closed until it is fully closed.

In the embodiment described above, since the torque T generated by the electric motor 18 changes rapidly near the synchronous speed n _s , when the torque T _l ' generated by the water turbine 14 decreases, the electric motor 18 moves between the generator region and the motor region. There is a problem of hunting. Therefore, in the invention, a wound type induction motor 18 is used, and when the speed approaches the synchronous speed n _s in the generator region, the resistance value of the secondary resistance 38 of the motor 18 is controlled to increase. It is preferable that the secondary resistance 38 is increased by a control signal shown by a broken line from the control device 24, and the motor generated torque T in _FIG . It becomes possible to shift the rotational speed to a stable operating point faster than the synchronous speed n _s . According to this embodiment, even when the rotational energy of the water turbine 14 decreases, it is possible to perform stable power recovery. The resistance control can be performed by the control device 24 based on the detection signal of the speed detector 36.

In addition, in the present invention, as described above, a wound type induction motor is used as a generator, and furthermore, this motor has a secondary resistance and can cope with fluctuations in the flow rate of cooling water, and the recovered torque and recovered power are determined by the secondary resistance. In each of the above-described embodiments in which the slip S of the motor is varied to maintain stability of operation, the synchronous speed n _s of the induction motor 18 is constant, so the electric power is Although recovery is often interrupted, if the synchronous speed n _s itself is controlled to a value lower than the actual rotational speed of the electric motor 18, it becomes possible to constantly regenerate electric power regardless of fluctuations in flowing water energy. 18 can be operated with high efficiency.
A variable synchronous speed circuit 40, shown in broken lines in FIG. 1, is connected to the motor 18, an example of which is shown in FIG. The synchronous speed variable circuit 40 shown in FIG. 3 is composed of a well-known variable voltage variable frequency inverter device, and controls the voltage and frequency (v/=constant) supplied from the power source 20 to the motor 18 to control the synchronous speed of the motor 18. n _s can be varied. That is, in FIG. 3, if the rotational speed of the electric motor 18 is detected by the speed detector 36, the speed is set based on this detection signal, and the voltage and frequency are determined based on this, the synchronous speed can be set with extremely high accuracy. It becomes possible to control the rotation speed below the actual rotation speed.

The variable synchronous speed circuit 40 described above can also be implemented by a pole number converter, a secondary excitation device, or the like in addition to the variable voltage variable frequency inverter device.

Furthermore, in each of the embodiments described above, the running water 12
However, when flowing water is pumped to various facilities in a steelworks, for example, a backflow of water may occur in the water channel 10. For example, when the pressure pump is stopped, the flow channel 10 The residual water inside the tank may return and cause a phenomenon. In each of the embodiments described above, the water turbine 1 is used to deal with this backflow water.
However, in the present invention, by attaching a reversing switch 42 shown by a broken line in FIG. 1, the motor 18 can be connected so that the coupled phase order of the motor 18 is reversed when the residual water flows backward. By reversing the rotational direction of the electric motor 18, the energy of the flowing water during this reverse flow can also be recovered to the power source 20 side.

As explained above, according to the present invention, the energy contained in flowing water in the blast furnace cooling system can be recovered as electricity with high efficiency, and the power recovery method is particularly profitable even for flowing water with a low head and large flow rate fluctuations. It is extremely effective for energy saving in steel works and other places.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a preferred embodiment of the cooling water head energy recovery device for a blast furnace cooling system according to the present invention, FIG. 2 is a characteristic diagram of the induction motor in FIG. 1, and FIG. FIG. 7 is a main part block diagram showing another embodiment. 10...Flow channel, 12...Flowing water, 14...Water wheel, 16...Control valve, 18...Induction motor, 20
... Commercial frequency power supply, 22 ... Switch, 28 ...
Power flow direction detector.

Claims (1)

[Scope of Claims] 1. Converting the head energy of the cooling water that cools the blast furnace into the rotational energy of the waterwheel, and controlling the rotational speed of the waterwheel by increasing the amount of water flowing sequentially while the waterwheel is being driven to rotate the waterwheel. When the rotational speed of the connected induction motor reaches a starting speed set below the synchronous speed, a power supply is connected to the motor and the induction motor is used as a generator to induce the amount of water supplied to the water turbine. Increase control is performed so that the maximum power can be recovered from the motor, and the running water head energy due to overspeed is recovered as electrical energy to the power supply side, and when the rotational speed of the induction motor becomes lower than the synchronous speed, a fixed time limit is applied. A method for recovering flowing water head energy in a blast furnace cooling system, characterized in that the connection between a rear induction motor and a power source is cut off, and the flowing water head energy is converted into electrical energy and recovered by a water turbine and an induction motor. 2. A water wheel provided in a flow channel of cooling water that cools the blast furnace and driven to rotate by the energy of the head of the water; a control valve that controls the flow rate of the cooling water supplied to the water wheel and varies the rotational speed of the water wheel; A wire-wound induction motor has a rotor that is connected to a water turbine and is slidably controlled by varying secondary resistance, and a stator that can be connected to a power source, and a switch that controls opening and closing of the connection between the stator of the induction motor and the power source. and a switching signal detector that outputs a switching signal to open the switch after a certain period of time after the induction motor detects the power flow direction and enters the motor region, and adjusts the secondary resistance of the induction motor. When the flowing water head energy is large, the induction motor and the power source are connected with a switch, the induction motor acts as a generator, and the flowing water head energy is recovered as electrical energy to the power source, and the flowing water head energy is A water head energy recovery device for a blast furnace cooling system, which is characterized by opening a switch to cut off an induction motor and a power source when it is small.