Power plants – Combustion products used as motive fluid – Process
Reexamination Certificate
2003-04-18
2004-11-16
Gartenberg, Ehud (Department: 3746)
Power plants
Combustion products used as motive fluid
Process
C060S039270, C060S039182
Reexamination Certificate
active
06817186
ABSTRACT:
The entire disclosure of Japanese Patent Application No. 2002-272777 filed on Sep. 19, 2002 including specification, claims, drawings and summary is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an operation control apparatus and an operation control method for a single-shaft combined plant. More specifically, the operation control apparatus and the operation control method according to the present invention are designed to be capable of optimally controlling the pilot ratio and the fuel-air ratio of a gas turbine whether a clutch is disengaged or engaged, or even in a transient period during which the clutch shifts from a disengaged state to an engaged state, or conversely from an engaged state to a disengaged state, with the result that the apparatus and the method can operate the single-shaft combined plant while keeping the combustion state of the gas turbine stable.
2. Description of Related Art
A single-shaft combined plant, having a gas turbine and a steam turbine connected by a single shaft, is a plant with a high efficiency, involving minimal emission of hazardous substances (NO
x
, etc.), and flexibly accommodating diurnal changes in electric power consumption. Recently, demand has grown for a further decrease in the construction cost for this single-shaft combined plant. The conventional single-shaft combined plant involved the following factors behind cost increases:
(i) Since the gas turbine and the steam turbine are simultaneously started, there is need for a thyristor (starter) capable of generating a huge starting torque.
(ii) Since the steam turbine also rotates, together with the gas turbine, at the time of starting, cooling steam needs to be supplied to the steam turbine so that the blades of the steam turbine do not thermally expand because of windage loss. However, before a power generator output by the gas turbine increases, an exhaust gas boiler, which produces steam from an exhaust gas from the gas turbine, cannot form steam that can be charged into the steam turbine. Thus, until the exhaust gas boiler forms steam which can be charged into the steam turbine, there arises the necessity for an auxiliary boiler with a very high capacity enough to supply adequate cooling steam to the steam turbine.
(iii) In the single-shaft combined plant, the gas turbine, the steam turbine and a power generator need to be arranged in a line. Thus, a condenser has to be installed below the steam turbine, while the gas turbine, the steam turbine and the power generator should be installed at a high position (at a height as high as the third floor of a building).
To reduce the construction cost, a proposal has now been made for a single-shaft combined plant equipped with a clutch, as shown in
FIG. 3
(see, for example, Japanese Unexamined Patent Publication No. 2002-38907). In
FIG. 3
, a gas turbine
1
and a steam turbine
2
are connected by a single shaft
3
, and a power generator
4
is also connected to the shaft
3
. A clutch
5
is interposed between the gas turbine
1
/power generator
4
and the steam turbine
2
. The clutch
5
enables the gas turbine
1
and the steam turbine
2
to be connected to and disconnected from each other.
With this single-shaft combined plant having the clutch
5
on the shaft
3
, only the gas turbine
1
and the power generator
4
are started, with the gas turbine
1
and the steam turbine
2
being disconnected from each other by the clutch
5
. When the gas turbine
1
reaches a rated rotational speed, the power generator
4
is connected to a power system. After connection of the power generator
4
to the power system, steam, which is generated by an exhaust gas boiler
6
with the use of exhaust gas from the gas turbine
1
, is supplied to the steam turbine
2
at a time when the steam becomes suppliable to the steam turbine
2
, thereby starting the steam turbine
2
. After the steam turbine
2
reaches a rated rotational speed, the clutch
5
is engaged to convey the torque of the steam turbine
2
to the power generator
4
.
The single-shaft combined plant equipped with the clutch
5
are started and stopped in the manners illustrated in FIG.
4
. In
FIG. 4
, solid lines represent a target load and an actual load, dashed lines represent gas turbine outputs, and one-dot chain lines represent steam turbine outputs.
As shown in
FIG. 4
, during a period from t
1
to t
2
within a start period, the actual load is only the gas turbine output. The target load and the actual load are increased according to a change rate.
At a time t
2
within the start period, the clutch
5
is engaged. In a period from t
2
to t
3
, the actual load increases in accordance with an increase in the steam turbine output.
After a time t
3
within the start period, the actual load is the sum of the gas turbine output and the steam turbine output. The target load and the actual load are increased according to the change rate.
Until a time t
10
within a stop period, the actual load is the sum of the gas turbine output and the steam turbine output. The target load and the actual load are decreased according to the change rate.
At the time t
10
within the stop period, a steam flow control valve V
4
(see
FIG. 3
) for the steam turbine
2
starts to be closed. At a time t
11
within the stop period, the clutch
5
is disengaged.
After a time t
12
within the stop period, the actual load is only the gas turbine output. The target load and the actual load are decreased according to the change rate.
The single-shaft combined plant equipped with the clutch
5
, as shown in
FIG. 3
, has the following advantages:
(I) Only the gas turbine
1
and the power generator
4
are started first, so that the capacity of a thyristor necessary for starting can be decreased (the capacity can be decreased in an amount corresponding to the weight of the steam turbine
2
).
(II) During a period for which only the gas turbine
1
and the power generator
4
are operated, the steam turbine
2
rotates at a low speed, requiring no cooling steam. Thus, the capacity of the auxiliary boiler can be decreased.
(III) The thermal expansion of the steam turbine
2
can be accommodated by the clutch
5
. Thus, the gas turbine
1
, the power generator
4
and the steam turbine
2
are arranged in this order, namely, the steam turbine
2
is arranged at the end, whereby an axial flow exhaust condenser can be used. By so doing, the shaft
3
can be installed at a lower position than before.
As shown in
FIG. 3
, the gas turbine
1
is composed of a compressor C, a burner B and a turbine T as main members. IGV (inlet guide vane)
7
is disposed at the entrance of the compressor C, and the opening of the IGV
7
is controlled by an IGV opening controller
8
.
A main fuel nozzle of the burner B is supplied with fuel at a flow rate controlled by a main fuel flow control valve V
1
, and a pilot fuel nozzle of the burner B is supplied with fuel at a flow rate controlled by defined by “pilot fuel flow rate/main fuel flow rate”.
A bypass pipe
9
is connected in parallel with the burner B, and the ratio between the amount of compressed air flowing into the burner B and the amount of compressed air flowing into the bypass pipe
9
varies with the opening of a burner bypass valve V
3
. That is, as the opening of the burner bypass valve V
3
decreases, the amount of air flowing into the burner B increases and the amount of air flowing into the bypass pipe
9
decreases. As the opening of the burner bypass valve V
3
increases, the amount of air flowing into the burner B decreases and the amount of air flowing into the bypass pipe
9
increases.
The amount of steam supplied from the exhaust gas boiler
6
to the steam turbine
2
is controlled by a steam flow control valve V
4
.
With the shingle-shaft combined plant equipped with the clutch, however, problems to be discussed below arise when the clutch
5
is engaged and when the clutch
5
is disengaged. These problems will be explained in sequence.
In the gas turbi
Gartenberg Ehud
Mitsubishi Heavy Industries Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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