JPS6039121B2 - How to operate blast furnace gas energy recovery power generation equipment during unstable blast furnace conditions - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of operating a blast furnace gas energy recovery power generation facility that generates power using blast furnace gas discharged during high-pressure operation of a blast furnace, and in particular, to a method for operating a blast furnace gas energy recovery power generation facility that can operate even when furnace conditions are unstable such as when blast furnace slip occurs. Continuous blast furnace gas energy recovery power generation equipment (hereinafter also referred to as blast furnace top pressure recovery power generation equipment)
This relates to how to drive a car.

As is well known, in order to increase the productivity of blast furnaces and reduce the fuel ratio, high-pressure operation in which the top pressure of the furnace is increased has become commonplace. For this purpose, it has become common practice to drive a turbine generator with high-pressure blast furnace exhaust gas and recover the pressure energy as electrical energy.

By the way, the operation of blast furnace top pressure recovery power generation equipment is influenced by the turbine input conditions, that is, the turbine inlet steam pressure and steam flow rate, similar to the turbine generator in a thermal power plant. The gas pressure or gas flow rate at the inlet of the turbine frequently and significantly fluctuates depending on the conditions of the blast furnace, such as large blast furnace slip, medium slip, or reduced air pressure, forcing an emergency shutdown of the power generation equipment. That is, when the input energy to the turbine becomes too large or too small, the power generation equipment is brought to an emergency stop in order to protect the equipment and prevent the generator from becoming an electric motor. To explain this using the blast furnace slip phenomenon as an example, as soon as the slip occurs, the furnace top pressure and the amount of gas generated increase rapidly, and the power generation output decreases from 1.2 to 1.2
The pressure increases rapidly to about 1.7 times, but the next moment the pleeder valve opens, and then the septan valve opens fully, so the furnace top pressure and the amount of gas generated drastically decrease, and as a result, the power generation output decreases almost proportionally. However, the power output becomes foggy or negative.
However, the top pressure recovery power generation equipment is generally installed in accordance with thermal power generation equipment, and therefore the furnace top pressure and gas generation amount will gradually recover to their original state. Turbine inlet gas pressure low trips and blast furnace gas flow rate low trips, etc. in , correspond to sudden steam pressure/steam flow rate drops or vacuum low trips in thermal power generation equipment, and as a result, when blast furnace slip occurs,
Normally, the first and second stages of reverse power, the second stage of low turbine inlet gas pressure, and the second stage of low turbine input gas flow rate are detected and the turbine/generator is immediately tripped for an emergency stop. However, when blast furnace furnace conditions are poor, it is not uncommon for blast furnace slips of various sizes to occur, and as a result, reductions in blast furnace gas flow rate and gas pressure may occur relatively frequently. However, with conventional power generation equipment that uses a flow rate control method, an emergency shutdown is required each time blast furnace slip occurs, as described above.Moreover, when the power generation equipment makes an emergency shutdown, it is difficult to investigate the cause and restart operations. Currently, operators are spending a great deal of effort and time in communication, etc., and as a result, it takes at least 20 to 3 hours for each blast furnace slip to recover.

As described above, with the operating method of the blast furnace top pressure recovery power generation equipment, there are many cases where emergency shutdowns are required, and it takes time to restore them, resulting in problems such as low operating rates and poor reliability of power supply. was there. The present invention has been made in view of the above circumstances, and is capable of operating blast furnace gas energy recovery power generation equipment that can minimize emergency shutdowns due to blast furnace furnace conditions and improve operating efficiency and power supply reliability. The purpose is to provide a method.

In other words, as a result of intensive study by the present inventors, we focused on the fact that the blast furnace slip that causes the turbine inlet gas pressure low 2-stage trip and the blast furnace gas flow rate low 2-stage trip usually recovers at a sand level of 20 to 5. Use a timer to close and lock the sand relay at 5 to 2 degrees after the turbine inlet gas pressure low stage 2 or blast furnace gas flow rate low stage 2 occurs to stop sending out the emergency stop signal, and take protection and security measures during that time. By taking these steps, the power generation equipment can be operated continuously without an emergency stop, and by appropriately selecting the set time of the timer, the turbine inlet gas pressure low stage 2 or the blast furnace gas flow rate low stage 2 can be maintained for the set time. This invention was developed based on the recognition that if the failure continues beyond this time, it can be determined to be a serious failure and the operation can be stopped to protect the equipment.

To explain the present invention in more detail below, the present invention is a method of continuing operation by closing and locking a relay for several seconds to tens of seconds when the blast furnace condition is unstable such as when a blast furnace slips. As a countermeasure, take the following measures.

First, as a protective measure against the input drop caused by the drop in blast furnace gas flow rate and the drop in turbine inlet gas pressure, a reverse power relay is installed at an optimum relay setting of 20 to 6 peaks in the range of 2 to 10% of the rated output. In addition to closing and locking with a timer, a second reverse power relay is additionally installed, and the second reverse power relay protects areas other than the protection range of the first reverse power relay. The reverse power relay of No. 2 shall be timed tripped in the range of 30 to 110% of the rated output with an optimum relay setting in the range of 15 to 60% of the rated output. Note that as the second reverse power detection method, the same effect can be obtained by comparing and detecting the generator output signal in the electric governor that controls the turbine governor valve using a comparator. By setting the first and second reverse power relays as described above, backup protection is provided by setting the relays corresponding to the sum of the wind losses and bearing losses of the turbine inverter or rotating blades and generator. These reverse power relays can also
It also functions as a protective relay to protect against the inflow of blast furnace gas, a gas containing a large amount of dust and mist, as well as damage to the impeller or rotary blades or loss of field caused by foreign matter entering the turbine. In addition, as a countermeasure for the generator and exciter, the short-circuit ratio of the generator is designed to be around 0.45 to 0.56 in order to protect against sudden large inputs such as blast furnace slips and subsequent drastic decreases in input. Therefore, it is possible to maintain sufficient steady-state stability (also referred to as steady-state stable limit power) against steep large inputs. In addition, the exciter operation is usually AQR operation or APF operation.
R operation will be performed to relatively increase the excitation (at or above the rated power factor), thereby reinforcing the state stability and at the same time supplying reactive power to the power distribution system. In addition, here, AQ
R operation generally means constant excitation operation C, but in a broader sense, the relationship between reactive power Q and active power P is Q=(shibP)0C(
b, C: constant), and APFR operation means operating while maintaining the relationship Q = bP. I explained a certain case, but if the generator does not have enough capacity and is operating at almost 100% power factor in constant excitation operation (or constant power factor operation), if you increase the excitation, it will fall outside the output limit curve range. , the start of blast furnace slip is detected (not shown), and steady state stability is achieved by applying strong excitation by pulsing distant excitation or excitation equivalent to the rated power factor for one fixed time period only when the output increases. May be reinforced.

In addition, we have added a function to switch to AVR operation at an output point of 5 to 20% of the rated output in case of a sudden decrease in input, and we have also added a function to ensure transient stability (
(also known as transient stability limit power). If the above protection and security measures are taken, the (transient)
Coupled with improved responsiveness, higher reliability and higher performance of power generation equipment, improved controllability of the turbine governor system, and improved performance of hydraulic control equipment, it can withstand adverse conditions such as blast furnace slip and continue to operate. Can drive.

Next, an embodiment of the present invention will be described with reference to the attached drawings. FIG. 1 shows a blast furnace exhaust gas system, and the high pressure exhaust gas generated from the blast furnace 1 is passed through a dry dust collector 2 and a wet dust collector 3. The furnace top pressure is controlled and adjusted to a predetermined pressure Ps by the manual valve 4M, range valve 4R, and control valve 4C that constitute this septum valve device 4, and the pressure is reduced, and then the pressure is reduced to an electrostatic precipitator. 5 and then distributed to various locations from a gas holder 6.

A furnace pressure recovery power generation equipment 7 is connected to the septum valve device 4.
are installed in parallel, the blast furnace gas discharged from the wet precipitator 3 is guided to the turbine 1OT via the cutoff valve 8 and the governor valve 9, and this turbine 1OT drives the generator 10G, and the exhaust gas of the turbine 10T is Gas is led to the electrostatic precipitator 5 and gas holder 6 via an outlet stop valve 11. A furnace top pressure detector 12 is attached to the blast furnace 1, and the detection signal of the furnace top pressure detector 12 is transmitted to the furnace top pressure regulator 1.
3 and output from the furnace top pressure regulator 13, the control valve 4C of the septum valve device 4 is controlled to control the pressure within a certain range, and the range valve 4R is controlled to maintain an appropriate pressure. Furthermore, the control signal output from the furnace top pressure regulator 13 is input to the turbine electric governor 14, and the opening degree of the governor valve 9 is adjusted by the control output signal processed here. Therefore, the furnace top pressure is largely controlled here, and almost the entire amount of blast furnace gas is allowed to flow into the turbine 10T to perform pre-pressure control. Further, when the turbine comes to an emergency stop, the manual valve 4M of the septum valve device 4 is controlled to open by the feedforward output signal of the electric governor 14. Furthermore, the power generation equipment 7 is equipped with a security interlock device 15, and this security interlock device 15 is equipped with a safety interlock device 15.
5 to shut off the shutoff valve 8 and circuit breaker 16. Figure 2 shows the main parts of the security interlock system.

In other words, the turbine generator is stopped based on signals such as serious turbine failure, serious generator failure, turbine generator stop, and mid-generator failure, and the electric governor sends a fully close command to the governor valve. In addition, each signal of the turbine inlet gas pressure low 2nd stage trip, the blast furnace gas flow rate low 2nd stage trip, and the first reverse power trip is closed and locked for a predetermined time by a timer, and the situation continues for more than the time set by the timer. In this case, the turbine generator is stopped, the isolation valve 8 is fully closed, and the electric governor 14 sends a full close command to the governor valve 9, and the turbine generator is immediately shut off by the second reverse power trip signal. It is designed to stop the electric governor and send out a command to fully close the electric governor. The operation of the top pressure recovery power generation equipment configured as described above, that is, the operating method of the present invention, will be explained by taking the case of blast furnace slip as an example.

Figure 3 is a graph showing the changes in gas pressure, gas flow rate, and generated power during blast furnace slippage.At the moment when blast furnace slip occurs, the amount of blast furnace gas generated and the furnace top pressure rapidly increase, and the power generation output also increases rapidly. However, the output is about 1.2 to 1.7 times the steady output, but normally a 10G generator is operated in AQR mode or APF mode.
Since R operation (EXA) is performed, stable operation is maintained. Further, when the furnace pressure becomes equal to or higher than the bleeder valve opening pressure PB, the bleeder valve dissipates, and the control signal from the furnace top pressure regulator 13 is input to the turbine electric governor 14, so that the governor valve 9 is activated to open the turbine electric governor 14. The control valve 4C and the range valve 4R of the septum valve device 4 are then fully opened by the control signal from the furnace top pressure regulator 13. After that, when the bleeder valve and the septum valve device 4 are fully opened, the blow-through of the blast furnace ends and the furnace top pressure and blast furnace gas flow rate decrease rapidly due to an increase in the ventilation resistance in the furnace, and the furnace top pressure accordingly decreases to the set pressure Ps. Then, the turbine inlet gas pressure low second stage trip pressure PT is further lowered to below, and at the same time, the blast furnace gas flow rate also shows a similar tendency and becomes below the low second stage trip point QT2 of the blast furnace gas flow rate. On the other hand, it automatically detects (not shown) that the power generation output (WP) has suddenly decreased below a certain set point within 5 to 20% of the rated output and switches to AVR operation (EXV). Instead, continue driving. In this case, the generator 10G becomes an electric motor, and its generated output becomes a negative output, which is equal to or less than the first reverse power trip point WR. Then, in the blast furnace where the gas pressure is below the turbine inlet gas pressure low second trip point PT, the gas flow rate reaches the blast furnace gas flow rate low trip point Q, below the flame limit, within the time TPd set by the timer. The blast furnace that is in operation is within the time TQ2 set by the timer, and the power generation output is above the first reverse power trip point WR, hereinafter the second reverse power trip point WR, and the duration is above the first reverse power trip point WR. , the set time Tw by the timer
If the blast furnace slips, the closure is locked for a fixed period of time, and the sending of a stop command due to a serious generator failure, such as an emergency stop or load shedding, is stopped and operation is continued.

That is, in the above-described method, if blast furnace slipping and similar phenomena occur within the above-mentioned set time period and within the relay set value, it is determined that there is no major failure and operation is continued.

In this way, the input conditions depending on the blast furnace furnace condition are determined by the above-mentioned safety interlock items (see the area surrounded by the dashed line in FIG. 2), and operation is continued within the allowable range of the turbine generator. As explained above, in the present invention, when the blast furnace furnace condition is unstable such as blast furnace slip, especially when the blast furnace gas pressure and gas flow rate suddenly decrease and the duration thereof is within a certain period of time,
Only during that time, the protective relay or protection device is closed and locked, and AQR operation or APFR operation is switched to AVR operation, so continuous operation is possible without causing serious equipment accidents even when furnace conditions are unstable such as blast furnace slippage. As a result, it is possible to dramatically improve the energy recovery rate, operation rate, and reliability of power generation supply, as well as to supply reactive power to the power distribution system and improve the power factor, as well as to trip the turbine during unstable blast furnace conditions. Due to the suspension of the command, the high temperature and high pressure dust gas flow associated with the forced septum valve can be suppressed, and as a result, dust adhesion in the blast furnace exhaust gas system, especially dry vision dust collectors, wet dust collectors, septum valve bags and pipes, has been suppressed. It has many excellent practical effects, such as preventing and cutting.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an example of a blast furnace exhaust gas system incorporating power generation equipment for carrying out the present invention, Fig. 2 is a block diagram showing the main parts of the safety interlock system, and Fig. 3
The figure is a graph showing changes in gas pressure, gas flow rate, and power generation output during blast furnace slip. 1... Blast furnace, 4... Septum valve device,
7...Furnace top pressure recovery power generation equipment, 10T...
...Turbine, 10G... Generator, 15... Security interlock device. Figure 2 Figure 3

Claims (1)

[Claims] 1 Blast furnace gas energy recovery power generation in which gas turbine power generation equipment for recovering blast furnace gas pressure energy is installed in the blast furnace exhaust gas system in parallel with a septum valve device, and these power generation equipment and the septum valve device control the furnace top pressure and generate electricity. In the equipment operation method, when there is a sudden increase in output due to unstable blast furnace conditions such as the occurrence of blast furnace slip, the turbine generator is operated continuously in constant power factor operation, constant excitation operation, or increased excitation, and then the blast furnace gas generation amount and When the furnace top pressure decreases, the protective relay and protection device are closed and locked for a certain period of time, and the turbine generator is switched to automatic voltage adjustment operation and operated, and during this period, the gas turbine generator equipment is operated without issuing a stop command. A method of operating a blast furnace gas energy recovery power generation facility during unstable blast furnace furnace conditions, characterized by continuing.