JP3117392B2 - Start-up method of an exhaust gas re-combustion complex plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of starting a combined plant for recovering heat of gas turbine exhaust as boiler combustion air.

[0002]

2. Description of the Related Art FIG. 2 is a system diagram showing an example of a conventional exhaust gas reburning type combined plant. Conventionally, an exhaust stack is installed at the outlet of the gas turbine (1), and the gas turbine system and the steam system are separately activated to switch from individual operation to combined operation, or to operate the boiler if there is no exhaust stack. Start first,
After some load, he started the gas turbine. In each of these cases, it was necessary to start the boiler using a forced air ventilator (FDF).

[0003] That is, when the gas turbine alone is operated at the time of starting the unit, it is necessary to install an exhaust pipe at the outlet of the gas turbine and further provide a denitration device at the outlet of the exhaust pipe. At this time, the damper (13) of the exhaust stack is opened, and the damper (10) installed between the gas turbine outlet and the boiler is closed.

Next, an air preheater (AH) and a forced draft fan (F)
In order to start the steam turbine and the boiler system using the DF), it is necessary to close the gas turbine outlet damper (10) and disconnect the gas cooler system from the system by the damper (11). At the same time, the air preheater inlet damper (12) is opened, and the air preheater (AH) is opened from the denitration device outlet.
Boiler exhaust gas to the side. After the boiler is heated and pressurized, the forced air ventilator (FDF) is gradually throttled to switch the O ₂ source to the exhaust gas at the gas turbine outlet. (The dampers (12) and (13) are closed and the dampers (10) and (11) are opened.) In order to start the boiler alone, combustion air is required, so a forced air blower (FDF) It is necessary to provide an air preheater (AH), an induction blower (IDF), and a chimney in the same manner as a conventional ordinary boiler in order to discharge exhaust gas from the boiler to the atmosphere without passing through a gas cooler. There is a need.

[0005]

Conventionally, when the gas turbine is started first, the exhaust gas of the gas turbine may be directly discharged to the atmosphere until the operation is switched to the combined operation. The situation has become so severe that untreated gas cannot be released to the atmosphere even at the time of startup, and a denitration device is required. In addition, when starting the boiler first, it is not necessary to use a forced draft fan or a startup fan during normal operation, but it is necessary to use an air preheater, a forced draft fan, etc. for the advance startup of the boiler. You will not get.

Therefore, it is desirable to start the gas turbine and the boiler at the same time. However, when starting with the conventional system shown in FIG. 2, there is a possibility that the feed water is heated and evaporated in the high-pressure gas cooler (4). There is. The present invention proposes a method of starting the feed water in the high-pressure gas cooler (4) while preventing the feed water from evaporating.

[0007]

In order to solve the above-mentioned conventional problems, the present inventor has set up a high-pressure water heater for heating feed water with steam and a high-pressure gas cooler for heating boiler exhaust gas in parallel in a boiler feed system. And a stop valve is provided at a water supply outlet of the high-pressure gas cooler, and at the time of start-up, the stop valve is closed and the upstream water supply is performed. The gas turbine and the boiler are sequentially ignited in a state where the pressure is set to a pressure higher than the boiler side residual pressure and does not steam against gas heat absorption at the time of startup, and low-temperature water is supplied from the high-pressure water heater to the boiler. When the boiler pressure rises and the boiler side pressure balances with the water supply side, the stop valve is opened and the high pressure water heater and high pressure gas cooler It proposes a method of starting repowering composite plant and supplying the water continuously to.

According to the method of the present invention, as described above, at the time of startup, the stop valve provided at the water supply outlet of the high-pressure gas cooler is closed, the upstream water supply pressure is higher than the boiler side residual pressure, and the gas heat While the gas turbine and the boiler are sequentially ignited and the low-temperature water is supplied from the high-pressure water heater to the boiler in a state where the pressure is set so as not to be steamed for absorption, even when the residual pressure on the boiler side is low. Steaming of the high pressure gas cooler is prevented. Also, when the pressure on the boiler balances with the water supply side due to the boiler pressure increase, the stop valve is opened when the pressures of both systems become substantially equal, and the water supply is continuously and simultaneously supplied from the high pressure water heater and the high pressure gas cooler. In addition, smooth start-up is possible with less disturbance.

[0009]

FIG. 1 is a system diagram showing an embodiment of the present invention. In the present embodiment, a stop valve (7) is provided at a water supply outlet of the high-pressure gas cooler (4).

When starting up the combined plant,
First, the water supply system of the high-pressure gas cooler (4) was maintained at a pressure higher than the boiler residual pressure so as not to cause steaming in the high-pressure gas cooler (4), and the stop valve (7) was closed to separate the boiler system and the water supply system. In the state, the gas turbine (1)
And ignite the boiler (2). In this case, the water is supplied intermittently via the drum level control valve (6). The water supply after passing through the high-pressure gas cooler (4) is recirculated to the condenser via the recirculation flow control valve (8).

After the ignition, the boiler (2) is pressurized while supplying water to the boiler drum by the drum level control valve (6). Then, when the pressures of the boiler (2) and the high-pressure gas cooler (4) match, the stop valve (7) is fully opened, so that the two systems on the high-pressure feed water heater (3) side and the high-pressure gas cooler (4) side operate in parallel. Then, a system for supplying water to the boiler (1) is established.

Thereafter, the pressure is increased as in a conventional general boiler. After the stop valve (7) is opened, the control of the drum level is switched from the starting drum level adjusting valve (6) to the regular drum level adjusting valve (9), and the high-pressure gas cooler (4) side is sufficiently controlled. In order to supply a proper supply of water, the temperature of the supply water at the outlet of the high-pressure gas cooler (4) is controlled using the recirculation flow control valve (8). This is because if the temperature of the boiler feedwater increases, steaming of the economizer may become a concern. In particular, when the load is low or when the engine is started, the exhaust gas amount of the gas turbine is constant, so that the boiler feedwater temperature (the high-pressure gas cooler outlet feedwater temperature) increases, and the recirculation flow control valve (8) opens.

[0013]

Conventionally, an exhaust gas treatment system such as a denitration apparatus is separately provided in order to treat the exhaust gas of the gas turbine within the pollution regulation value at the time of starting, or an air preheater is used when the boiler is started in advance. It was necessary to provide a fan and a forced draft fan only for starting the plant.

According to the present invention, the exhaust gas treatment of the gas turbine exhaust stack can be performed by ordinary equipment. Further, it is not necessary to operate auxiliary equipment such as an air preheater and a forced draft fan only at the time of starting the plant, and starting using only gas turbine exhaust gas becomes possible. This eliminates the need for equipment such as an air preheater and a fan, reduces startup loss, and shortens startup time.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention.

FIG. 2 is a system diagram showing an example of a conventional exhaust gas reburning combined plant.

[Explanation of symbols]

 (1) Gas turbine (2) Boiler (3) High pressure feed water heater (4) High pressure gas cooler (6) Drum level control valve (for starting) (7) Stop valve (8) Recirculation flow rate control valve (9) Drum level control Valve (common use) (10), (11), (12), (13) Damper (AH) Air preheater (FDF) Push-in ventilator (IDF) Induction ventilator

Claims (1)

(57) [Claims] 1. A high-pressure water heater for heating feedwater with steam and a high-pressure gas cooler for heating with boiler exhaust gas are installed in parallel in a boiler water supply system, and exhaust gas refueling using residual oxygen in gas turbine exhaust for boiler combustion. In the combined type plant, a stop valve is provided at the water supply outlet of the high-pressure gas cooler, and at the time of startup, the stop valve is closed, and the upstream water supply pressure is higher than the boiler side residual pressure. In a state where the steaming is set at a non-steaming pressure, the gas turbine and the boiler are sequentially ignited, and low-temperature water is supplied from the high-pressure water heater to the boiler. Opening the stop valve and supplying water continuously from the high-pressure water heater and the high-pressure gas cooler simultaneously; How to start the event.