JP3788071B2 - gas turbine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas turbine, and more particularly to a gas turbine provided with means for controlling a supply amount of compressed air supplied from a compressor of the gas turbine to a combustor.
[0002]
[Prior art]
In recent years, various fuels such as coal gasification furnace-generated gas, gas generated in a blast furnace and coke oven (by-product gas) have been used as fuel to be supplied to the combustor of the gas turbine and burned. However, such gas has a characteristic that the calorific value (calorie) is lower than that of normal fuel. Japanese Patent Laid-Open No. 60-222531 provides an air compressor and a fuel compressor having multistage variable blades, and controls the multistage variable blades according to the amount of heat generated by the fuel burned in the combustor. -It is described that control is performed to optimize the air ratio.
[0003]
[Problems to be solved by the invention]
However, in the known apparatus, the compressor structure itself is complicated. In addition, a normal fuel such as LNG has a calorific value of about 10,000 kcal / kg, whereas a calorific value of by-product gas such as a blast furnace is as low as about 1/10 of 1000 kcal / kg. In order to burn this low-calorie fuel and generate high-temperature and high-pressure gas in the same way as when supplying normal fuel, a combustor with a larger fuel flow rate (about 10 times in this case) than normal fuel according to the calorific value of the fuel gas. It will be necessary to throw in. When a large amount of combustion gas flows into the turbine in this way, the compressor discharge pressure rises and the margin for the surging of the compressor decreases. On the other hand, the compressor discharge pressure is kept constant by using a compressor with a smaller air volume than the gas turbine compressor of normal fuel so that the amount of combustion gas flowing into the turbine is the same as that of the turbine in normal fuel. When trying to supply a plurality of fuel gases having different calorific values to a combustor, a single compressor cannot cope.
[0004]
An object of the present invention is to provide a gas turbine capable of stable operation even when fuel of different calories (calorific value) is supplied to a combustor.
[0005]
[Means for Solving the Problems]
The present invention relates to a compressor, a combustor that is supplied with compressed air discharged from the compressor and a plurality of fuels having different calorific values, and combusts, and is connected to the compressor via a shaft to burn from the combustor. A gas turbine comprising: a gas-supplied and driven turbine;
The extraction means for extracting a part of the compressed air supplied from the compressor to the combustor outside the system, and the amount of extraction extracted from the extraction means outside the system is changed according to the use of fuel having a different calorific value. And control means for controlling so as to suppress the pressure fluctuation of the compressed air supplied to the combustor.
[0006]
Thereby, even if the calories of the supplied fuel are different, the gas turbine can be controlled stably and easily.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
A gas turbine according to an embodiment of the present invention will be described with reference to FIG.
[0008]
Coal is abundant in oil reserves and attracts attention as an alternative fuel for petroleum. Therefore, plants that use coal gasifier-generated gas as fuel for gas turbine combustors as thermal power generation facilities have attracted attention in recent years. ing. On the other hand, by-product gas generated in blast furnaces and coke ovens at steelworks is distributed to hot blast furnaces, heating furnaces, etc., but there are cases where it is used for conversion to highly flexible power. However, the by-product gas generated in the blast furnace or coke oven is not only low in calorie but also low in pressure, so it is necessary to increase the pressure when used as fuel for a gas turbine.
[0009]
The compressor 101 to which the air 111 is supplied and the turbine 102 are connected via a shaft 401, and the turbine 102 and the boosting low calorie gas compressor 115 are connected to the turbine 102 by a shaft 402. A load (generator) 103 is connected to the coaxial 403. The compressed air discharged from the compressor 101 is supplied to the combustor 104, and the fuel is combusted. The combustion exhaust gas from the combustor 104 is supplied to the turbine 102 to drive the turbine 102. The exhaust 112 of the turbine 102 is used as a heat source such as an exhaust heat recovery boiler as needed.
[0010]
The compressed air compressed by the compressor 101 passes through an extraction line 116 provided with a control valve 117 for controlling the flow rate, and then enters an expander 113 such as a separate expansion turbine that is not connected to a shaft connected to the turbine 102. Supplied. The expander exhaust 118 that has flowed through the expander 113 is supplied to, for example, a place where air is required in the plant.
[0011]
A pressurizing low calorie gas compressor 114 is connected via the expander 113 and the shaft 405 to pressurize the low calorie gas 105 supplied from the low calorie gas supply means. The primary boosted low calorie gas 106 boosted by the boosting low calorie gas compressor 114 is supplied to the boosting low calorie gas compressor 115 connected to the gas turbine 102 by the shaft 402. The secondary boosted low calorie gas further boosted through the compressor 115 is supplied to the combustor 104 through the low calorie fuel supply line 107. The combustor passes through the low calorie gas flow control valve 108 for controlling the flow rate of the low calorie gas. 104.
[0012]
On the other hand, normal high-calorie fuel such as oil or LNG is supplied from a normal fuel supply means through a normal liquid fuel supply line 109, and a flow rate control for controlling the flow rate of fuel supplied to the combustor 104 in the line 109. A valve 110 is provided.
[0013]
A detection device 130 for detecting the amount of heat generated by the fuel is installed in the low calorie fuel supply line 107 in the vicinity of the low calorie gas flow control valve 108. If it can detect the emitted-heat amount of this fuel, it may not be restricted to the same detection apparatus.
[0014]
A control device 120 for controlling each flow control valve 117, 110, 108 is provided, and a load signal is input to the control device 120 from a load detector 123 for detecting a gas turbine load. This embodiment is based on a signal from the generator 103.
[0015]
The configuration of a normal gas turbine including a compressor 101, a gas turbine 102, and a combustor 104 and a load 103 (generator, etc.) is the same as that of a gas turbine plant using a normal amount of fuel. In the case of a fuel with a normal calorific value, the liquid fuel supply line 109 for this fuel is used, the fuel supplied to the combustor 104 is controlled by the control valve 110, and the combustion temperature is constant in the base load operation mode. In the present embodiment, a low calorie fuel supply line 107 for supplying low calorie fuel to the combustor 104 and a low calorie gas compressor 115 for pressurization for boosting the low calorie gas having a low supply pressure corresponding to the low calorie gas fuel, A control valve 108 is installed. When low calorie gas is used as combustion gas, normal fuel from the liquid fuel supply line 109 is closed by the control valve 110, and the fuel is controlled by opening the control valve 108 for low calorie gas provided in the low calorie fuel supply line. Operation is controlled based on the relationship between the gas turbine exhaust temperature and the compressor outlet pressure so that the gas turbine combustion temperature remains constant. A large amount of low calorie gas will flow into the combustor 104 to achieve temperature. As a result, there arises a problem that the pressure ratio increases and the surge margin of the compressor decreases. In the present embodiment, in order to avoid this, the amount of air extracted from the compressor 101 is controlled by controlling the opening degree of the control valve 117. The amount of this bleed air is controlled so as to increase as the calorific value of the fuel decreases and decrease as it increases. Furthermore, this embodiment has a separate expander 113 for effectively utilizing the power of the extracted air and a separate low-pressure gas compressor 114 for boosting that is a fuel compressor. The extracted air from the outlet of the compressor 101 guided to the separate expander 113 expands to generate power, and drives the pressurizing low calorie gas compressor 114. The power of the pressurizing low calorie gas compressor 115 installed on the gas turbine shaft can be reduced by the amount of power boosted by the pressurizing low calorie gas compressor 114 connected through the shaft 405 combined with the expander 113. In addition, the power of the compressor 101 can be used effectively, and operation with high plant efficiency can be achieved as a whole.
[0016]
In the above configuration, the low-calorie fuel gas is first boosted by a separate boosting low-calorie gas compressor 114 and then boosted by a boosting low-calorie gas compressor 115 connected to the gas turbine 102 and burned. The low-calorie fuel gas is firstly boosted by a boosting low-calorie gas compressor 115 connected to the gas turbine 102, and then secondarily boosted by a separate boosting low-calorie gas compressor 114. The pressure may be increased and supplied to the combustor 104.
[0017]
In this way, the bleed line 116 and the control valve 117 for the compressor discharge air are provided to control the amount of bleed from the compressor, and the air extracted from the compressor 101 is separately provided with the expander 113 and the low calorie gas compression for boosting. The machine 114 is used effectively. As a result, even if the combustor 104 burns from a low calorie fuel of about 1000 kcal / kg to a normal fuel of about 10,000 kcal / kg without reducing the surge margin of the compressor 101 and without reducing the performance. It is possible to operate freely while suppressing a decrease in output and efficiency of the turbine.
[0018]
Here, the operation of the gas turbine of FIG. 1 will be described. The main body gas turbine 102 has a compressor 101 and a load 103. The fuel at the time of start-up is usually high calorie liquid fuel such as light oil or LNG fuel, and the normal fuel is supplied to the combustor 104 using the liquid fuel supply line 109 and the control valve 108, and the compressor The control valve 117 installed in the bleed line 116 is closed to burn the fuel. The combustion gas burned in the combustor 104 drives the gas turbine 102 and drives a load 103 such as a generator. When using low-calorie fuel, which is a gasification fuel gasified from coal or a by-product gas generated in a blast furnace or coke oven, as a fuel for a gas turbine, this type of low-calorie fuel gas has an ignition performance higher than that of a normal fuel. Since it is low, liquid fuel and LNG fuel, which are high calorie fuels, are used from gas turbine startup to stable operation. Thereafter, when it becomes possible to switch from the liquid fuel or the LNG fuel to the low calorie fuel, the fuel switching operation is performed. In the fuel switching, first, the control valve 108 of the low calorie combustion supply line 107 is slightly opened to guide the low calorie gas to the combustor 104. After confirming the ignition of the low calorie gas in the combustor 104, the opening degree of the control valve 108 of the low calorie gas system is increased to increase the flow rate of the low caloric gas, while the opening degree of the liquid fuel flow rate control valve 110 is reduced. The flow rate of the high calorie liquid fuel supplied to the combustor 104 is reduced. If switching is performed with a partial load of the gas turbine, the pressure ratio has a sufficient margin, so that the extraction flow control valve 117 of the extraction line 116 can be kept closed. After switching, the operation of the gas turbine can be freely changed. The normal fuel (liquid fuel or the like) is supplied, for example, when the gas turbine is started or stopped, or when a fuel supply such as a by-product gas of low calorie gas is hindered. (At this time, for example, switching control is performed so that the control valves 117 and 108 are closed and the control valve 110 is opened.)
FIG. 2 has the same basic configuration as the gas turbine system shown in FIG. 1, but is further connected to a boosting low calorie gas compressor 114 driven by a separate expander 113 and connected to a generator 406 by a shaft 406. An electric motor 219 is added. In FIG. 2, 114 is a low calorie gas compressor as shown in FIG. 1, but when there is a difference between the expander 113 and the load of the compressor 114, that is, when the power of the expander is insufficient, 219 is the electric motor. If the expander power is exceeded, 219 is used as a generator. Others are the same as FIG.
[0019]
By configuring as in the present embodiment, the fuel can be switched from normal high calorie fuel to low calorie gas, and stable operation can be performed even when the calorific value of the low calorie gas varies greatly.
[0020]
When supplying low calorie fuel, there is no particular problem even if low pressure by-product gas is supplied to the gas turbine combustor because the gas turbine compressor discharge compressed air at low load is low in pressure. Further, even if a large amount of by-product gas as described above is supplied, the discharge compression air pressure does not increase so much. However, as the load rises, the gas turbine first stage stationary blade inlet temperature rises, the pressure rises, and the fuel consumption also increases. , Surging can be prevented and the load can be changed stably. In addition, it is possible to smoothly solve the point that the necessary pressure width of the by-product gas is increased due to the pressure increase accompanying the load increase and the like, and the surging allowable width of the gas turbine compressor needs to be increased.
[0021]
3 and 4 are comparisons of main body gas turbine compressor discharge pressure changes during operation of the embodiment of the present invention. FIG. 3 shows the change of the compressor discharge pressure of the low calorie fuel gas turbine and the compressor outlet pressure of the normal fuel gas turbine with respect to the gas turbine load when extracting from the compressor from the partial load to the full load of the gas turbine. Is. In particular, the amount of bleed air from the compressor is controlled so that the compressor outlet pressure of the low calorie fuel gas turbine does not become higher than the maximum discharge pressure of the normal fuel gas turbine compressor.
[0022]
FIG. 4 shows changes in the low-calorie fuel gas turbine compressor discharge pressure and the normal fuel gas turbine compressor outlet pressure with respect to the gas turbine load when the gas turbine is partially loaded, particularly when extracting from no load to full load.
[0023]
3 and 4 show examples of changes in the compressor discharge air pressure of the low calorie fuel gas turbine and the normal fuel gas turbine with respect to the gas turbine load, and the pressure when the gas turbine load is 0% is (531). , (631), the pressure when the gas turbine load is 100% is indicated by (532), (632) and (533), (633). The actual change is not simple, but the figure shows the change as a straight line. The pressure of the low calorie fuel gas turbine is higher than that of the normal fuel gas turbine because the calorific value of the fuel is low, and in order to generate high-temperature and high-pressure gas, a larger amount of fuel than normal fuel is injected into the combustor. is there. This compressor outlet pressure is related to the design pressure of the compressor casing and turbine casing, and there is also a problem of the surging limit pressure of the compressor, so if it is the same casing as the normal fuel gas turbine, it will be higher than the maximum pressure of the normal fuel gas turbine. Should not be too high. In FIG. 4, the compressor discharge air is extracted at a predetermined gas turbine partial load (535) or higher, and the discharge pressure is kept constant from the predetermined partial load (536) to the gas turbine load 100% (533). It can be suppressed to a maximum pressure (533) or less at a gas turbine load of 100%. This pressure change portion is indicated by oblique lines (538) and (539) in the figure.
[0024]
FIG. 4 shows an earlier extraction start point of the low calorie fuel gas turbine. In the drawing, the pressure value (636) lower than that in the case of the predetermined load is the extraction start point, and the partial load at that time is (635). This (636) may be further accelerated to the pressure (631) in the case of no load. When the operation pattern is no load (631), the pressure increases as the load increases and the pressure is (636), bleed is started, the pressure is constant until the predetermined load, and from the load (641) to the normal gas turbine discharge pressure. The operation may be performed at the same time, or the operation can be performed at a pressure different from the change lines of the pressures (636), (641), and (633) by adjusting the extraction amount. If the discharge pressure is kept below (636), neither a problem of strength nor a problem of surging occurs. For example, at the time of start-up, after igniting with normal fuel, switching to low-calorie fuel as described above is performed at a partial load lower than the loads (535) and (635), and then the extraction line is changed according to the gas turbine load as described above. The control valve 117 of 116 is controlled to control the discharge pressure of the compressor 101.
[0025]
FIG. 5 shows the relationship between the amount of bleed and the compressor discharge pressure in a constant combustion temperature operation. Normally, the base load operation of the gas turbine is controlled by an exhaust temperature control line that is a relationship between the exhaust temperature and the compressor outlet pressure. At this time, the state of the gas turbine is an operation at a constant combustion temperature, and FIG. In other words, the relationship between the amount of bleed air and the compressor discharge pressure in the base load operation control is shown. When the amount of extraction is increased, the gas flow rate to the turbine decreases as described above, so the compressor discharge pressure decreases, and the relationship is shown by the line 711 in the figure. When the calorific value of the fuel gas supplied to the plant is lowered, a larger amount of fuel is introduced into the combustor 104 and the compressor discharge pressure rises, so that the characteristic shown by the line 712 in the figure is obtained. On the other hand, when the calorific value of the fuel gas increases, the compressor discharge pressure decreases, so that the characteristic shown by the line 713 in the figure is obtained.
[0026]
If there is no control method for adjusting the amount of bleed, the compressor discharge pressure rises from point A to point D in FIG. 6 when the calorific value of the fuel gas decreases, so the compressor discharge pressure is lowered by lowering the combustion temperature. However, a reduction in combustion temperature leads to a reduction in cycle efficiency.
[0027]
In this embodiment, when the calorific value becomes low, the compressor discharge pressure is kept constant by increasing the extraction flow rate (721 → 723). On the other hand, when the calorific value becomes high, the compressor discharge pressure is kept constant by decreasing the extraction flow rate (721 → 722). That is, the relationship (811) between the heat generation amount and the extraction flow rate as shown in FIG. 6 is incorporated in the control device, and the extraction amount control valve 117 adjusts the extraction amount corresponding to the change in the heat generation amount. In order to keep the pressure ratio 812 constant, control is performed so as to increase the extraction amount when the heat generation amount of the fuel is smaller than when it is large.
[0028]
For example, when C is the amount of heat generated (822), the amount of extraction is 832, when A is the amount of heat extracted (821) when the amount of heat is generated (831), and when B is the amount of heat generated (823), the amount of extraction is (833). To do.
[0029]
For example, specifically, in the gas turbine system diagram shown in FIG. 1, a fuel calorific value detector 130 is provided in the low calorie fuel supply line 107 in the vicinity of the control valve 108, and based on the detection signal of the detector 130. The amount of extraction is controlled by controlling the control valve 117 in the line 116. At this time, the pressure ratio of the gas turbine is always kept constant as indicated by 812 in FIG. As described above, the gas turbine can be operated in an optimum state by adjusting the extraction flow rate with respect to the heat generation amount and controlling it so as to move along the line 714 in FIG.
[0030]
In addition, you may consider the case where the flow volume distribution inside the combustor 104 is changed according to the calorific value. This changes the flow rate inside the combustor which is an element constituting the gas turbine. When the calorific value of the fuel decreases, the fuel gas flow rate increases so as to keep the load constant. However, in order to make the fuel-air ratio constant, the bypass flow rate is decreased to increase the air required for combustion. In this configuration, the amount of air passing through the combustor is kept constant, and only the flow distribution inside the combustor is changed. Therefore, if the amount of fuel gas increases, the flow rate flowing into the turbine increases accordingly, and the pressure ratio increases. To do. Accordingly, in this configuration, although there is no problem with a heat generation amount change of several percent, it is not possible to cope with a large change in which the heat generation amount becomes larger than 1/2. In FIG. 5, the bypass amount increases as the heat generation amount decreases, but the pressure increases as the fuel gas increases, resulting in a movement as indicated by a line 715.
[0031]
According to these embodiments, even when the low calorie gas is supplied, it is possible to suppress the combustion temperature from being lowered as compared with the normal fuel supply.
[0032]
In addition, since the fluctuation of the discharge pressure can be suppressed by adjusting the amount of extraction of the compressor discharge air, the operating state of the gas turbine can be optimized. In addition, the degree of freedom in driving can be increased.
[0033]
Extraction air can be used as a separate expander air source, and the operating freedom of the expander is not greatly affected by the operating conditions of the main body gas turbine, and the operating range with high thermal efficiency can be widened.
[0034]
【The invention's effect】
According to the present invention, even when a plurality of fuels of different calories are supplied to the combustor, a stable gas turbine can be easily operated.
[Brief description of the drawings]
FIG. 1 is a system diagram showing a gas turbine according to an embodiment of the present invention.
FIG. 2 is a system diagram showing a gas turbine according to another embodiment of the present invention.
FIG. 3 is a load-compressor discharge pressure relationship diagram according to an embodiment of the present invention.
FIG. 4 is a load-compressor discharge pressure relationship diagram according to an embodiment of the present invention.
FIG. 5 is a relationship diagram between an extraction flow rate and a compressor discharge pressure under a constant combustion temperature condition according to an embodiment of the present invention.
FIG. 6 is a diagram showing the relationship between the heat generation amount of fuel gas and the extraction flow rate for keeping the compressor discharge pressure constant according to the embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 ... Air compressor, 102 ... Main body gas turbine, 103 ... Main body load (for example, generator), 104 ... Combustor, 105 ... Low calorie gas, 106 ... Primary boost low calorie gas, 107 ... Low calorie fuel supply line, 108 ... Low calorific gas flow control valve, 109 ... Liquid fuel supply line, 110 ... Liquid fuel flow control valve, 111 ... Atmosphere, 112 ... Exhaust, 113 ... Expander, 114, 115 ... Low calorie gas compressor for pressurization, 116 ... Extraction line, 117: Extraction flow rate control valve, 118: Expander exhaust.

Claims (5)

A compressor,
A combustor that is supplied with compressed air discharged from a compressor and a plurality of fuels with different calorific values to burn;
A turbine connected to the compressor via a shaft and supplied with a combustion gas from a combustor and driven by the turbine,
An extraction system for extracting a part of the compressed air supplied from the compressor to the combustor out of the system;
Provide a control valve installed in this extraction system,
When using fuel with a low calorific value in the combustor, the pressure of the compressed air supplied to the combustor is increased by opening the control valve and increasing the amount of air extracted from the extraction means. Control means for controlling to suppress fluctuations;
A gas turbine comprising: A compressor,
A combustor which is supplied with compressed air and fuel discharged from the compressor and burns;
A turbine connected to the compressor via a shaft and supplied with a combustion gas from a combustor and driven by the turbine,
A first fuel supply path for supplying the first fuel from the first fuel supply means to the combustor;
An extraction system for extracting a part of the compressed air of the compressor; a control valve provided in the extraction system; an expander that communicates with the extraction system and is driven by being supplied with the compressed air;
A first fuel compressor that is connected to the expander via a shaft and pressurizes a second fuel having a calorific value lower than that of the first fuel supplied from a second fuel supply means;
A second fuel compressor connected to the turbine via a shaft and further boosting the second fuel discharged from the first fuel compressor;
A second fuel supply path for supplying the second fuel boosted by the second fuel compressor to the combustor,
According to switching of the first fuel or the second fuel, the fuel to be supplied to the combustor
Extracted from the compressor,
Control means for controlling the amount of compressed air supplied to the expander;
A gas turbine comprising: A compressor,
A combustor which is supplied with compressed air and fuel discharged from the compressor and burns;
A turbine connected to the compressor via a shaft and supplied with a combustion gas from a combustor and driven by the turbine,
A first fuel supply path for supplying the first fuel from the first fuel supply means to the combustor;
An extraction system for extracting a part of the compressed air of the compressor; a control valve provided in the extraction system; an expander that is driven by being supplied with compressed air in communication with the extraction system;
A first fuel compressor that is connected to the expander via a shaft and pressurizes a second fuel having a calorific value lower than that of the first fuel supplied from a second fuel supply means;
A second fuel compressor connected to the turbine via a shaft and supplied with the second fuel discharged from the first fuel compressor and further boosted;
A second fuel supply path for supplying the second fuel boosted by the second fuel compressor to the combustor,
When the fuel supplied to the combustor is switched from the first fuel to the second fuel,
Control means for controlling the pressure fluctuation of the compressed air supplied to the combustor to increase the amount of extraction from the extraction means by opening the control valve;
A gas turbine comprising: A compressor,
A combustor that is supplied with compressed air discharged from a compressor and a plurality of fuels with different calorific values and burns;
A turbine connected to the compressor via a shaft and supplied with a combustion gas from a combustor and driven by the turbine,
An extraction system for extracting a part of the compressed air supplied from the compressor to the combustor out of the system, a control valve provided in the extraction system,
Detection means for detecting the calorific value of the fuel supplied to the combustor;
Control means for adjusting the opening degree of the control valve based on the signal of the detection means, changing the amount of extraction from the extraction means, and controlling the pressure fluctuation of the compressed air supplied to the combustor; ,
A gas turbine comprising: A compressor,
A combustor that is supplied with compressed air discharged from a compressor and a plurality of fuels with different calorific values to burn;
A turbine connected to the compressor via a shaft and supplied with a combustion gas from a combustor and driven; and an extraction system for extracting a part of the compressed air supplied from the compressor to the combustor outside the system; In a gas turbine comprising
When the calorific value of the fuel supplied to the combustor is switched from high calorific fuel to low calorific fuel,
The amount of extraction is increased from the extraction system to the outside of the system, and control is performed so as to suppress the pressure fluctuation of the compressed air supplied to the combustor.
A control method for a gas turbine.

Images