Data processing: measuring – calibrating – or testing – Measurement system – Temperature measuring system
Reexamination Certificate
2001-03-20
2003-03-04
Barlow, JOhn (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system
Temperature measuring system
C702S181000, C702S182000, C702S183000, C702S185000, C700S021000, C700S028000, C700S029000, C700S031000, C700S286000, C700S287000, C700S288000, C060S645000, C060S039182, C060S646000, C060S660000, C060S657000
Reexamination Certificate
active
06529849
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermal efficiency diagnostic method and an apparatus of a combined power generation plant, which can clearly specify a thermal efficiency deterioration causative equipment (i.e. an equipment which causes a deterioration of thermal efficiency) in a case where a fluctuation or deterioration is generated in a thermal efficiency of a combined power generation plant that is already being operated and which can properly and effectively recover the thermal efficiency through inspection, repair and the like.
2. Prior Art
The thermal efficiency of a thermal power generation plant has become a focus of great attention recently in view of two points, that is, fuel saving and reduction of power generation cost. In the case where the thermal efficiency actually changes, it is imperative in the thermal efficiency management to specify which piece of equipment is responsible for the change in the thermal efficiency in a plant.
In this case, the thermal efficiency is a numerical value representing the performance of the power generation plant and expressed as a ratio of the generated electric power to a consumed fuel energy. The thermal efficiency is expressed by the following equation (1).
[Equation1]
thermal efficiency (%)=generated output (power)(
W
)/[fuel heat value (J/kg)×fuel consumption(kg/s)]×100 (1)
An improvement in the thermal efficiency can lead to a reduction in the fuel consumption. In a power generation plant already existing, a performance management of the entire plant and each piece of equipment are carried out through daily checks and measurements and periodic performance tests, and afterwards, the results are reflected in plant operation and maintenance.
Among the thermal power generation plants, a combined cycle (C/C, ACC) power generation plant represents the most advanced main unit which was introduced for the first time about ten years ago. The combined cycle power generation plant has a high thermal efficiency and a high utilization factor, and in recent years, its availability has considerably increased.
However, after the combined cycle power generation plant has been in operation for about ten years elapsed, certain units begin to show noticeable deterioration in the thermal efficiency, and for this reason, it is imperative from the standpoint of economy to identify the causative equipment and pinpoint the cause of deterioration of the thermal efficiency so as to take remedial measures. In the case of discovering the cause of the deterioration of the thermal efficiency, the combined cycle power generation plant is constructed in a manner in which the gas turbine (GT) and the steam turbine (ST) exist in one unit, with these turbines are connected to one generator. For this reason, it is very difficult to determine as to whether the gas turbine or the steam turbine causes the deterioration of the thermal efficiency. In the conventional cases, although there exists a method for individually calculating each performance of the GT and ST, the above-described method is marred by the problem in its accuracy due to influence of measurement data errors as described herein later.
In the combined power generation plant, the equipment comprising the plant facility is of a large scale, and much time and labor are required for inspection, repair and so on. Moreover, the amount of equipment, time, manpower hours, cost and the like required for such work markedly increases. In the case of large-scale inspection and repair mentioned above, a good recovery result in the thermal efficiency is expected in almost all cases. Thus, in order to obtain this high recovery result, it is necessary to identify the thermal efficiency deterioration causative equipment by the thermal efficiency diagnosis for clarifying which equipment requires inspection and/or repair as compared with the conventional case. On the other hand, as stated previously herein, it is very difficult to determine which the gas turbine or the steam turbine is the cause of the deterioration. Under such circumstances, even if computer processing is introduced to perform the thermal efficiency diagnosis, the cost incurred for its facility, man/hours, management and so on are considerable, and furthermore, there remains a problem that a high diagnosis accuracy is not always obtained.
SUMMARY OF THE INVENTION
The present invention has been made taking the problem encountered in the prior art into consideration. It is, therefore, an object of the present invention to provide a thermal efficiency diagnostic method and an apparatus for a combined power generation plant capable of effectively identifying which equipment causes the deterioration in the thermal efficiency with high accuracy by accurately analyzing influences brought about by performance changes of individual equipment upon the whole plant for the purpose of properly realizing the thermal efficiency recovery through periodic inspection, repair or the like.
In the present invention, a heat balance analysis by optimum state estimation is introduced as a method of improving an accuracy of the thermal efficiency diagnosis of a combined power generation plant. In this case, the heat balance represents input and output of heat energy or electric energy of each equipment in the entire power generation plant.
The inventors of the subject application have made various studies and tests, and as a result, they have obtained the following concept. That is, a performance calculation is not independently carried out with respect to all equipment of the plant, but on the basis of each measurement data in a power generation plant, a decision was made whether optimum consistency can be made when the heat balance of the entire plant is set. It is thereby possible to make a cross check of each measurement data, thus improving the diagnosis accuracy.
More specifically, there is a dispersion of accuracy in measurement data relative to the heat input and output of each equipment of the combined power generation plant. For example, according to the conventional thermal efficiency management method of the combined cycle power generation plant, a performance calculation is carried out independently with respect to the whole of the gas turbine equipment, the whole of the exhaust gas heat steam generator (i.e. HRSG) and the whole of the steam turbine (ST). On the basis of control data measured in the power generation plant, when showing an accuracy estimation according to the conventional method of directly calculating the performance of the main equipment, the accuracy error (&Dgr;&eegr;GT/&eegr;GT) of the gas turbine efficiency is 7.8%, the accuracy error (&Dgr;&eegr;HRSG/&eegr;HRSG) of the exhaust gas heat recovery boiler efficiency is 3.2% and the accuracy error (&Dgr;&eegr;ST/&eegr;ST) of the steam turbine efficiency is 15.6%.
However, it has been found that the above-described percentages are not accurate enough to diagnose the cause with respect to the change (about 2%) in the thermal efficiency of a combined cycle power generation plant, which will usually occurs. Equations for calculating an accuracy error of the efficiency are as follows.
The accuracy of the gas turbine efficiency is obtained from the following equation (2) by differentiating and arranging both sides.
[Equation 2]
|&dgr;&eegr;
GT/&eegr;GT|=W
gas/(
WLNG−W
gas)|&dgr;
G
gas/&dgr;
G
gas|+
W
gas/(
WLNG−W
gas)|&dgr;
h
gas/
h
gas|+
W
gas/
WLNG|&dgr;WLNG/WLNG|=
7.8% (2)
The accuracy of the exhaust gas heat recovery boiler efficiency is obtained from the following equation (3) by differentiating and arranging both sides.
[Equation 3]
|&dgr;&eegr;
HRSG/&eegr;HRSG|=|&dgr;Wwtr/Wwtr|+|&dgr;G
gas/
G
gas|+|&dgr;
h
gas/
h
gas|=3.2% (3)
The accuracy of the steam turbine efficiency is o
Obikawa Hajime
Umezawa Shuichi
Barlow JOhn
Cherry Stephen J
The Tokyo Electric Power Co. Inc.
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