JPH0627484B2 - Operating method of combined plant - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a plant comprising a plurality of gas turbines, an exhaust heat recovery boiler and an ammonia injection type denitration device installed in the exhaust gas system thereof, and in particular to a gas turbine. The present invention relates to an operation method for reducing NOx emitted from a train at startup.

[Background of the Invention]

As a NOx reduction measure for a combined plant, a gas turbine employs a steam injection method and a low NOx combustor, and an exhaust heat recovery boiler uses a NOx removal device using a dry catalytic reduction method with ammonia injection to reduce NOx. . As a device related to this type, for example, Japanese Patent Publication No. 59-
There is 32645 publication.

In general, a combined plant constitutes a series by combining a plurality of small capacity units. Therefore, NOx must be controlled so that the total NOx of the entire series, that is, the total of NOx discharged in each unit is equal to or less than the regulation value.

By the way, in the combined plant, the load is changed by switching the number of gas turbines. In addition, the main operation mode is DSS (Daily start & stop) operation, and the gas turbine is frequently started and stopped.

Recently, even when starting up a gas turbine, keeping the NOx regulation value in place has become a problem. However, at the time of starting the gas turbine, the above-mentioned NOx reduction measures do not function sufficiently, and the NOx characteristic at the time of starting the unit shows a steady characteristic after a certain peak is generated, as shown in FIG. As a measure for reducing this peak value, a means for maintaining the gas turbine at a rotation speed of about 40% for a certain period of time has been proposed. However, when starting a gas turbine with NOx characteristics at such a unit startup, the total number of NOx emissions emitted from the series depends on the startup case, that is, the combination of the number of preceding operation units and the number of additional startup units. The peak value may exceed the regulation value.

[Object of the Invention]

An object of the present invention is to provide a method for operating a combined plant that reduces NOx so that the total emission value of NOx emitted from the train does not exceed the regulation value when the gas turbine is started.

[Outline of Invention]

In the present invention, when starting the gas turbine, if there is a unit in the preceding operation, the NOx set value of the operating unit is reset, and as a result, the ammonia injection amount is controlled to control the series. The feature is that the total emission value of NOx emitted more is kept below the regulation value.

The second feature of the present invention is that the gas turbine to be additionally activated is
The control system is provided to hold the rotation speed around 0% and determine the rotation speed holding time from the total NOx emission value discharged from the series.

The third feature is that it has a control system that determines the starting interval of the gas turbine to be additionally started from the total emission value of NOx emitted from the series.

Furthermore, the fourth feature is that the gas turbine to be additionally started is
It is to have a control system that determines both the holding time and the start interval held at a rotational speed of around 0% from the total NOx emission value emitted from the series.

Example of Invention

 An embodiment of the present invention will be described below with reference to FIG.

Gas turbine 1 is a compressor 2 for producing compressed air
And a low NOx combustor 3 for producing combustion gas by mixing compressed air and fuel from the compressor, and a gas turbine 4 operated by the combustion gas, and a turbine shaft has a generator 5 and a steam turbine 7. Are connected.

The combustion gas that has worked in the gas turbine 4 is sent to the exhaust heat recovery boiler 6, and steam for driving the steam turbine 7 is produced in the exhaust heat recovery boiler 6.

The steam that has worked in the steam turbine 7 is condensed in the condenser 8, and this condensed water is sent to the exhaust heat recovery boiler 6 by the boiler feed water pump 9 and is heat-exchanged with the exhaust gas to become steam. The generated steam is sent to the steam turbine 7 again.

A denitration device 10 is provided in the exhaust heat recovery boiler 6, and ammonia from an ammonia injection pump 11 is injected into the denitration device 10 via an ammonia flow control valve 12. This ammonia flow control valve 12 is a unit NO
x It opens and closes according to a command from the control device 13.

Fuel is sent to the low NOx combustor 3 via a fuel flow rate transmitter 14, and its signal is sent to the unit NOx controller 13.

In addition, NOx contained in the exhaust gas at the outlet of the exhaust heat recovery boiler 6
The concentration is detected by the unit NOx concentration transmitter 15, and the detection signal is sent to the unit NOx controller 13. further,
The inlet gas temperature of the denitration device 10 is detected by the temperature transmitter 16, and the detection signal is also sent to the unit NOx control device 13.

The above is regarded as one unit 17, and the exhaust gas discharged from the plurality of units is collected in the chimney 18 and discharged from the chimney 18 as the exhaust gas of the plant.

Each unit NOx control device 13 is connected to a series NOx control device 19 which controls NOx in the entire series.

The unit NOx control device 13 will be described with reference to FIG.

The unit NOx controller 13 opens and closes the ammonia flow control valve 12 based on the NOx set value 20 sent from the series NOx controller 19 and the exhaust heat recovery boiler outlet NOx concentration 15. In the unit in the preceding operation, the exhaust gas amount 21 is calculated from the fuel flow rate 14, and in the unit to be additionally started, the start mode 22 (hot start / warm start / cold start) is calculated from the denitration device inlet gas temperature. These calculated signals and NOx concentration 15 are the series N
It is sent to the Ox controller 19.

The series NOx control device 19 will be described with reference to FIG.

The series NOx control device 19 sends the lowest NOx set value 20 determined from the denitration efficiency or the leak ammonia concentration to each unit NOx control device 13 when the additional starting unit number 23 is given. NOx of the preceding operation unit
The actual NOx value of the entire preceding operation unit is calculated from the concentration 15 and the exhaust gas amount 21. From the difference between this value and the NOx regulation value, the NOx value that can be discharged for the entire additional startup unit is calculated.
This value, the number of additional startup units 23, and each startup mode 22
More start-up unit start-up interval 24 or 40
The% rotation speed holding time 25 is calculated, prioritized and sent to the unit controller 26 (FIG. 1). Based on this, the unit control device 26 starts up the unit.

When the startup of all units is completed, the series NOx control device 19
Calculates the NOx set value 20 of each unit so that the calculated actual NOx value becomes equal to or less than the regulation value, and sends it to the unit NOx control device 13.

Next, the operation will be described. Here, a case in which two additional operation units are activated when there are four preceding operation units will be described as an example with reference to FIGS. 1 to 4.

First, the signal 23 indicating the number of additional startup units is 2
When it is sent to the x control device 19, the denitration efficiency, or the
Leakage NH released from the exhaust heat recovery boiler 6 without reaction
_The lowest NOx setpoint 20 determined by the value of ₃ is sent. In response to this, each unit NOx control device 13 adjusts the ammonia flow rate control valve 12 to control the exhaust heat recovery boiler outlet NOx concentration 15 to this. In this way, the preceding operation unit NOx is reduced.

In addition, the series NOx control device 19 calculates the schedule of the additional starting unit and sets the starting time 2 to the starting unit.
4 or 40% rotation speed holding time 25 is sent to the unit controller 26. As a result, the unit is activated.

When the second unit is started, the NOx setting value 20 is released from the minimum value, and all the units including the preceding operation unit that was previously reducing NOx are discharged from the series.
x Controlled by the deviation between the total emission value and the regulation value.

The above example is a single-shaft combined plant, but may be applied to a multi-shaft combined plant including a plurality of gas turbines and a smaller number of steam turbines.

〔The invention's effect〕

According to the present invention, it is possible to suppress the total NOx emission value emitted from the series when the gas turbine is started up to the regulation value or less.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of a plant according to an embodiment of the present invention, FIG. 2 is a configuration diagram of a unit NOx control device of the present invention, FIG. 3 is a configuration diagram of a series NOx control device of the present invention, and FIG. Is a characteristic diagram of NOx emitted from the series of the present invention, and FIG. 5 is a characteristic diagram of NOx at start-up emitted from the unit. 1 ... Gas turbine, 6 ... Exhaust heat recovery boiler, 12 ... Ammonia flow rate control valve, 13 ... Unit NOx control device, 14 ...
Fuel flow rate transmitter, 15 ... NOx concentration transmitter, 16 ... Temperature transmitter, 17 ... Unit, 19 ... Series NOx control device.

Claims (4)

[Claims] 1. A combined plant, which comprises a plurality of gas turbines, a plurality of exhaust heat recovery boilers, and a steam turbine as main equipment, and which is provided with a catalyst for injecting ammonia into an exhaust gas system of the gas turbine to reduce NOx, When starting the turbine, when there is the gas turbine in the preceding operation, the NOx set value of the operating gas turbine is reset, and the ammonia injection amount is controlled according to the result. How to operate a combined plant. 2. The gas turbine according to claim 1, wherein the gas turbine to be additionally started is held at a rotation speed of around 40%, and the rotation speed holding time is NO from all gas turbines.
x A method for operating a combined plant, which is characterized by determining and controlling from a total emission limit value. 3. The operation of a combined plant according to claim 1, wherein the starting interval of the gas turbine to be additionally started is determined and controlled from the NOx total emission limit value from all gas turbines. Method. 4. The claim 1 according to claim 1, wherein both the holding time and the starting interval for holding the gas turbine additionally started at a rotation speed of around 40% are based on the NOx total emission limit value from all gas turbines. A method for operating a combined plant, which is characterized by determining and controlling.