JPS63105208A - Combined plant start/stop time adjusting method - Google Patents

Abstract

PURPOSE:To enable the start/stop time of the whole of a series to be shortened by adjusting the start/stop time of each unit so that the NOx quantity of the whole of the series may be put within a series regulating value. CONSTITUTION:At a series NOx quantity calculation portion 120, the characteristics of the time change of each unit's NOx discharge quantity are predicted by grasping the plant condition 100 of each unit within a series and on the basis of the data of a unit schedule calculation portion 105. And, the NOx characteristic of the whole of the series is sought by putting together these predicted characteristics, and if necessary, a command is given to a series schedule calculation portion 110 in order that the start interval or stop interval of a start or stop unit may be slid until a series NOx quantity is put within a regulating value. Thus, even if there is a plurality of start/stop units, the shortening of the time required for starts/stops for the whole of the series becomes possible, while the series NOx regulating value is being observed.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a control device for a combined plant, and in particular, the present invention relates to a control device for a combined plant, and in particular, it is possible to control the total startup time and shutdown time of the plant while adhering to environmental regulation values for NOx emissions. This invention relates to a method for adjusting start and stop times between units to shorten the time.

[Conventional technology]

Measures to reduce NOx in combined plants include the two-stage combustion method (using a low NOx combustor) and the water injection method for gas turbines.

■Steam injection method, In the exhaust heat recovery boiler.

(2) Catalytic denitrification method (denitrification equipment).Normally, some of these methods are used in combination to reduce NOx. Japanese Patent Application Laid-Open No. 59-32645 describes a method of using a combination of NOx reduction methods of this type.

[The problem that the invention aims to solve] In general, a combined plant combines multiple small-capacity units to have the same capacity as the number of normal thermal power plants, so multiple units are treated as one power plant (hereinafter referred to as a series), so NOx Regarding regulations, it is necessary to control the entire series so that the total NOx value emitted from each unit is below the environmental regulation value.

By the way, when looking at the load operation of the series, in order to take advantage of the high efficiency during high output operation, which is a unit characteristic of the Hunbind plant, there is a significant increase or decrease in the series load (for example, starting from a low load in the morning to (Transition from high load during the middle of the day to low load at night) is generally responded to by starting and stopping an appropriate number of units.

The problem here is that the amount of NOx generated by the unit during startup and shutdown becomes a considerably large value due to the limitations on use and characteristics of the denitrification method described above. NO at startup
As for the x characteristics, as shown in FIG. 3, the amounts of N and Ox at the outlet of the denitrification device become large until a certain point after the ignition gas is added. Although the NOx amount at the inlet of the denitrification equipment increased after that, the NOx amount at the outlet remained within the regulated value because as the load increased after startup, the gas turbine exhaust gas temperature rose and the catalytic reaction became active. This is because the effectiveness of NOx reduction measures increases, such as by reaching a temperature range of

Because of these NOx characteristics, if several units of gas turbines start and stop at the same time during load operation in a train, it may not be possible to comply with the train NOx regulation value by taking measures to reduce NOx on a unit-by-unit basis. In contrast, in the past, the start and stop times of the units were simply shifted by a certain period of time to prevent the series actual NOx amount from exceeding the regulation value.

However, this requires a large margin, and there is a problem in that the starting and stopping times of the entire series become too long.

The purpose of the present invention is to shorten the start and stop times of the entire series while observing the series NOx regulation value.

[Means for solving problems]

The above purpose is to
The amount of Ox is accurately predicted based on the plant status at the time of startup and shutdown, and the amount of NOx for the entire series is accumulated based on the start and stop times of each unit determined by this predicted value and schedule calculation, to keep it within the series NOx regulation value. This is achieved by adjusting the start and stop times of each unit so that the

[Effect]

Schedule calculations, which are conventionally performed for thermal power plants, can be roughly divided into two types for combined power plants. One is to calculate the arrival time of each event when starting and stopping each unit (hereinafter referred to as unit schedule calculation).The other is to start each unit according to the load pattern of the entire series.

It calculates the stop start time (hereinafter referred to as a series schedule).

The starting pattern and stopping pattern of the unit are uniquely determined once the process state at the time of startup is determined, and the amount of NOx is also almost determined. Once the NOx amount of each unit is determined, the NOx amount of each unit is accumulated according to the start and stop times of each unit specified in chronological order in the series schedule, and the NOx amount of the entire series is checked to see if it exceeds the regulation value. I know what's going on. By feeding this result back to the series schedule calculation and appropriately shifting the unit start-up and stop times, it is possible to keep the NOx regulation value as a series and to minimize the start-up and stop times of the entire plant.

〔Example〕

An embodiment of the present invention will be described below.

Figure 2 shows the schematic configuration of the -axial type compounding plant and the N
In a combined plant (hereinafter abbreviated as C/C) that takes measures against oxygen, a gas turbine (hereinafter abbreviated as G/T) 10 is the main engine, and the air sucked and compressed by a gas turbine compressor 11 is converted into fuel in a combustor 12. The high-temperature, high-pressure combustion gas drives the turbine 13 to obtain output.

The combustion gas discharged from the G/T at y still has a large amount of heat and is at a high temperature, so the heat is recovered by the downstream exhaust heat recovery boiler (hereinafter abbreviated as HR8G) 20, and the gas is sent to the chimney 2.
It is discharged from 5. The steam generated by HR8G drives a steam turbine (hereinafter abbreviated as S/T) 30 to obtain output.

Since G/T burns a large amount of air at high temperatures, thermal NOx, which is generated by the combination of nitrogen and oxygen in the air, becomes a problem. Although several types of NOx reduction measures are used in combination, the water injection method and the steam injection method are limited in use when the amount of fuel is small, that is, when starting and stopping, in order to ensure stable combustion.

Similarly, the low NOx combustor 12 also releases NOx when the amount of fuel is small.
It has no effect on suppressing the amount of x generation. or.

The denitrification device 60, which removes NOx discharged from the G/T through a chemical reaction using ammonia, has a reaction efficiency that is greatly affected by temperature, and has the highest reaction efficiency in a high-load region where the G/T exhaust gas temperature is high. .

The HR8G outlet NOx amount is designed to be smaller than the inlet NOx amount. Therefore, the 5 reaction efficiency is poor in the low load range from startup ignition to the low load range and from the low load range at stop to extinguishing, and there are regulations on the discharge of unreacted ammonia to the outside of the system. Use of denitrification equipment is restricted.

In this way, low-range NOx countermeasures cannot be expected to be effective when starting or stopping, and although the amount of NOx generated by the G/T is not that large, it is mostly emitted from the chimney as it is1. In normal load range, NO generated in G/T
Although the amount of x tends to increase, it is possible to clear the regulation value at the chimney exit due to the large effect of NOx low-range measures (especially denitrification equipment). At the time of startup, therefore, the characteristics are as shown in FIG. 3, and the NOx amount may exceed the regulation value (the value obtained by dividing the series NOx amount by the number of units). However, since a combined plant usually consists of a plurality of units as shown in FIG. 4, it is sufficient that the amount of NOx in the entire system does not exceed the regulation value.

Even if there is a start/stop unit, if there is a margin in the denitrification performance of other operating units, control is performed to reduce the NOx amount and maintain the NOx regulation value for the series. However, when a series load starts up rapidly in the morning or stops down rapidly at night, there are many starting and stopping units1.Normally, there are few operating units, so if the starting time and stopping time of several units overlap, If left as is, it may not be possible to comply with the series NOx regulation value, and it may not be possible to start or stop the system. Since the amount of NOx in the starting and stopping units becomes extremely large within a few minutes to about ten minutes, if the starting and stopping times of each unit are set so that the peaks of the amount of NOx do not overlap, It is possible to comply with series NOx regulation values. A method for starting and stopping units while observing the series NOx regulation value will be explained using FIG.

The amount of NOx in each unit varies depending on the plant status, and depending on the number of operating units at that time, the amount of NOx in the series
Since there may be cases where the regulation value can be cleared, the plant status 100 of each unit in the series is grasped, and the series NOx
f#, the calculation unit 120 predicts the characteristics of the time change in the NOx emission amount of each unit, superimposes these predicted characteristics to obtain the NOx characteristics of the entire series, and if necessary, starts or stops the unit. A command is given to the series schedule calculation unit 110 to shift the start interval or stop interval of the series until the series NOx amount falls within the regulation value.

The superposition of series NOx amounts and start-up time adjustment will be explained with reference to FIG. Figure 5(a) shows a state in which the &1 unit is in operation and the unit NOx amount is controlled.
This is Nα2. When the Nα3 unit starts up, it is expected that the NOx amount at each start-up will be as shown in (b) and (Q). Considering that the NQ1 to Na3 units form one series, the NOx emission characteristics of the series become as shown in FIG. 5(d), which shows that the series exceeds the NOx regulation value. Time exceeding series NOx regulation value 6
If the ignition times of the Na 2 and Na 3 units are shifted by one minute as shown in FIG. 5 (6), the series NOx amount can clear the regulation value.

In this way, even if there are a plurality of starting and stopping units, it is possible to shorten the time required for starting and stopping the entire series while observing the series NOx regulation value.

The above example uses a -shaft type compounding plant, but
The present invention may be applied to a multi-shaft combined plant including a plurality of gas turbines 10 and a smaller number of steam turbines 30 as shown in FIG.

〔Effect of the invention〕

According to the present invention, even if multiple units start and stop at the same time in a combined plant, the NO.
Start-up of the first unit while observing x regulation values, or
Combined plant startup or shutdown time defined as the time from shutdown to startup of the last unit or shutdown varies depending on plant status and series NOx regulation value.
The time can be shortened by several minutes to more than ten minutes.

[Brief explanation of the drawing]

Figure 1 is a functional configuration diagram of an embodiment of the present invention, Figure 2 is a schematic diagram of the main engine configuration of a single-shaft compounding plant, Figure 3 is a graph of NOx amount characteristics at startup per shaft, and Figure 4 is a diagram of multiple units. FIG. 5 is an explanatory diagram of the start/stop time adjustment method of the present invention, and FIG. 6 is a schematic diagram of the configuration of a multi-shaft combined plant. 10... Gas turbine, 20... HR8G, 25.
... Chimney, 30 ... Steam turbine, 40 ... Generator, 60 ... Denitrification device, −

Claims (1)

[Scope of Claims] 1. In a control device for controlling the start and stop of a plurality of units of a combined plant consisting of a plurality of units combining a gas turbine and a steam turbine, the amount of nitrogen oxide emissions of the entire plant is , using the predicted nitrogen oxide emissions of each unit so that the startup or shutdown time of the entire plant is shortened within the environmental regulation value,
A method for adjusting start and stop times for a combined plant, the method comprising adjusting the start and stop times of each unit.