JPH0331899B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a gas turbine device. Especially nitrogen oxides (NOx) contained in gas turbine exhaust gas.
This relates to low-pollution, high-combustion efficiency gas turbine equipment that suppresses the generation of unburned components such as carbon monoxide (CO) and hydrocarbons (HC).

[Background of the invention]

Gas turbines tend to become more efficient by increasing the temperature and pressure, and at the same time, it is essential to achieve low pollution and high combustion efficiency. In this case, among the substances contained in gas turbine exhaust gas, NOx and CO are the targets of air pollution, and on the other hand, suppressing CO and HC has a large effect on improving combustion efficiency. Therefore, in gas turbines, it is necessary to simultaneously improve efficiency, reduce pollution, and improve combustion efficiency, but as temperatures and pressures increase,
The production of NOx increases, but on the other hand, if attempts are made to suppress the production of NOx, the production of CO and HC will increase. Because of this contradictory relationship,
It is a very difficult technique to solve these problems at the same time. In conventional technology, first, NOx in the combustor
As a means of suppressing generation, low-temperature combustion is performed using excess air, and a NOx reduction catalyst layer is installed in the exhaust duct to significantly reduce the concentration of NOx exhausted. However, gas turbines require low NOx over a wide range from ignition to rated load.
It is difficult to simultaneously maintain combustion efficiency and high combustion performance. This is because the range is wide and the conditions are different for each. In particular, the combustion state at low loads is
Combustion is inhibited due to excessive air excess, and CO
The generation of unburned components such as and HC increases. Furthermore, when the load is low, the temperature of the exhaust gas decreases, so the efficiency of the denitration catalyst decreases, and therefore the concentration of NOx emitted into the atmosphere is not reduced. This situation will be explained using a diagram.

Figure 1 shows the main configuration of the gas turbine. The gas turbine consists of an air compressor 1, a combustor 2, and a turbine 3, and the exhaust gas 4 that has passed through the turbine 3 passes through a catalyst layer 5, or in some cases, a boiler for exhaust heat recovery is installed after this. , released into the atmosphere. NOx, which causes pollution, is generated in the combustor 2, and its generation is greatly affected by the gas temperature during combustion. combustion, so-called low-temperature combustion method
Efforts are being made to reduce NOx. further emitted into the atmosphere
A catalyst layer 5 is installed to further suppress the amount of NOx. Ultimately, it is required to keep the amount of NOx below 10 to 15 ppm over the entire operating load range of the gas turbine. However, the prior art is particularly problematic at low loads. In other words, the NOx concentration relative to the gas turbine load increases as the load increases at the gas turbine outlet, as shown by the M line in Figure 2, but this is because the data includes the effect that the exhaust gas is diluted with air at the gas turbine outlet. In order to eliminate this effect, it is necessary to convert the exhaust gas to a constant oxygen concentration (15%). When corrected like this,
The NOx concentration is as shown by the N line in Figure 2. As shown in the N line, especially at low loads, the NOx concentration increases approximately four times due to the correction due to the dilution effect. on the other hand,
When the load is low, the denitrification efficiency also decreases due to the decrease in exhaust gas temperature, so the concentration of NOx exhausted increases from the rated load, as shown by the L line, and even exceeds the regulation value. That is, in a load range of 50% or less, as shown in FIG. 3, the exhaust gas temperature (C line) decreases as the load decreases, and the denitrification efficiency (D line) decreases. This is because, as shown in Figure 4, the amount of air supplied to the combustor (solid line A) is constant from low load to rated load, and the combustion flow rate (dotted line B) changes as the load changes. The exhaust gas temperature becomes low at low load when the amount of gas is low, and therefore the denitrification efficiency decreases. YuiWith conventional technology
It is becoming difficult to keep NOx concentrations below regulatory limits. In addition, regardless of the load, the air flow rate is constant and in order to suppress NOx generated in the combustor, combustion with excess air is performed based on the rated load when NOx emissions are high. The air excess is four times that under load (this occurs because the air flow rate is constant and only the fuel flow rate changes). Therefore, in this case, combustion occurs at an excessively low temperature and combustion is inhibited, resulting in increased generation of end-combustion components such as CO and HC, and a decrease in combustion efficiency.

[Purpose of the invention]

The purpose of the present invention is to reduce the denitrification efficiency of the catalyst without reducing the denitrification efficiency even in the gas turbine low load operating range.
It is an object of the present invention to provide a gas turbine device capable of reducing NOx, improving combustion efficiency at low loads, and suppressing the generation of unburned components.

[Summary of the invention]

The present invention achieves the above object by regulating the flow rate of air introduced into the combustor during low load to prevent deterioration in catalyst performance. If this configuration is used to suppress the air flow rate introduced into the combustor at low loads,
This makes it possible to suppress a decrease in denitrification efficiency without lowering the exhaust gas temperature even under low load conditions, thereby making it possible to significantly reduce the NOx concentration in the exhaust gas. In addition, by suppressing the air flow rate, it is possible to eliminate low-temperature combustion caused by an excessive excess of air, and therefore it is possible to improve combustion efficiency at low loads.

[Embodiments of the invention]

An embodiment of the present invention is shown in FIG. This gas turbine device includes a compressor 1, a turbine 3, and a combustor 2.
In addition, a denitrification catalyst layer 5 for removing nitrogen oxides is installed in the exhaust gas passage. In the present invention, the amount of air flowing into the combustor during low load of the gas turbine is controlled by an inlet guide vane of the compressor, a flow control valve provided in the air inflow path to the compressor, or a combination of both. In this embodiment, an air flow rate control device 9 capable of controlling the flow rate of air 8 is installed in the inlet section 7 of the compressor 1, and the air flow rate is controlled via a controller 10. It is configured to do so. Of course, depending on the case, the operation may be performed by the inlet guide vane 11 installed at the front stage of the compressor 1, or by combining the guide vane 11 and the flow rate control device 9. In addition, air 12 is extracted from an intermediate stage of the compressor 1, a valve 13 is installed to control this, and the air is introduced downstream of the catalyst layer 5 in order to prevent the temperature of the gas passing through the catalyst layer 5 from decreasing. It is also possible to do this.

Adjust the air flow rate as follows. That is, the air flow rate is adjusted from near no load to near 50% load as shown in FIG. 4, and is variably controlled as the load increases as shown by line I in the figure. At this time, the fuel flow rate is not much different from conventional control as shown in the J line, but by making the air flow rate variable in this way, the combustion state of the combustor is changed to the condition where the air flow rate decreases from the A line to the I line. becomes. This prevents excessive air combustion during low loads. In addition, as shown in the dotted line C to K in Figure 3, the turbine exhaust temperature is approximately 400% lower than the exhaust gas temperature equivalent to 50% load from no load to 50% load.
Can be kept at ℃. Therefore, the denitrification efficiency does not tend to decrease at low loads as shown in the prior art (line E) in FIG. 6, but rather increases as the exhaust temperature increases as shown in the dotted line G. As a result, the NOx concentration does not tend to increase particularly at low loads, compared to the conventional F-line which exhibits a high concentration at low loads, and on the contrary, the denitrification efficiency improves. Therefore, as shown by the H line in Figure 6, the
NOx concentration can be suppressed.

In this way, by reducing the air flow rate supplied to the combustor at low loads, it is possible to suppress the deterioration of denitrification performance, but the amount of decrease in air flow rate in this case is less than the rated value at no load. Approximately at load
It is desirable to keep it at about 50%, increase the fuel flow rate and air flow rate as the load increases, and control the flow rate so that at 50% load, the air flow rate is approximately the same as at the rated load. In this way, the combustion state can be made almost equal from no load to 50% load. This is the guide vane 11 of the inlet.
If the control is controlled by , the vane angle will be controlled at 30° or more.

Therefore, the combustion state at no load is almost the same as the combustion state at 50% load, so low-temperature combustion due to excessive air excess does not occur as in the conventional technology, and the combustion state does not result in the combustion of CO, HC, etc. It is possible to obtain the effects that the generation of combustion products is reduced, combustion performance is improved, and combustion efficiency can also be improved.

〔Effect of the invention〕

According to the present invention, it is possible to improve denitrification efficiency and combustion performance from low load to high load.

It should be noted that, as a matter of course, the present invention is not limited to the illustrated embodiment.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional gas turbine device. FIG. 2 is a characteristic diagram showing the relationship between turbine load and NOx concentration. FIG. 3 is a characteristic diagram showing the relationship between turbine load, gas temperature, and denitrification efficiency. FIG. 4 shows the relationship between the gas turbine load and the air and fuel flow rates, and is a diagram comparing data from the prior art and an embodiment of the present invention. FIG. 5 is a configuration diagram showing a gas turbine device according to an embodiment of the present invention. FIG. 6 is a comparison diagram of the denitrification efficiency and NOx concentration characteristics between this example and the conventional technology. DESCRIPTION OF SYMBOLS 1... Compressor, 2... Combustor, 3... Turbine, 5... Denitration catalyst layer, 7... Inlet part, 9
... Air flow control device, 11 ... Inlet guide vane, 12 ... Air bleed piping, 13 ... Air bleed valve.

Claims (1)

[Claims] 1. A gas turbine, a compressor that is driven by the gas turbine and compresses air, and a combustion system that combusts fuel under the compressed air from the compressor and supplies combustion gas to the gas turbine. and a denitrification catalyst device for removing nitrogen oxides provided in an exhaust gas passage of the gas turbine, the gas turbine device comprising: an inlet guide vane that adjusts the amount of air flowing into the compressor; bleed air piping that releases air discharged from an intermediate stage of the denitrification device to the downstream side of the denitrification device;
A low-pollution gas turbine device comprising: a bleed valve provided in the middle of the bleed pipe to adjust an amount of bleed air. 2. A gas turbine, a compressor that is driven by the gas turbine and compresses air, a combustor that combusts fuel under compressed air from the compressor and supplies combustion gas to the gas turbine, and the gas turbine. A gas turbine device comprising: a denitrification catalyst device for removing nitrogen oxides provided in an exhaust gas passage; an inlet guide vane for adjusting the amount of air flowing into the compressor; a bleed pipe that releases air to the downstream side of the denitrification device;
A low-pollution gas turbine device comprising: a bleed valve provided in the middle of the bleed pipe to adjust an amount of bleed air.