JP2520082B2 - Automatic operation method of gas turbine exhaust reburning boiler for power generation - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas re-combustion system in which a gas turbine exhaust gas pipeline for power generation is connected to a boiler for steam power generation, exhaust gas of a gas turbine is introduced and used for combustion of a boiler, and power up of the boiler is achieved. In order to recover steam and required power in a short time without lowering steam conditions and power generation during automatic operation and gas turbine trips when introducing gas turbine exhaust into the boiler or disconnecting the introduction to perform individual operation. The present invention relates to a method for automatically operating a gas turbine exhaust reburn boiler for power generation.

[0002]

2. Description of the Related Art When a gas turbine for power generation (hereinafter abbreviated as GT) trips, boiler turbine power generation (BT
It is preferable to immediately back up the electric power by means of G), but from the economical aspect, the instrumentation and equipment are complicated, the boiler is stopped once in a small power plant, and then a forced draft fan (abbreviated as FDF). The method of turning and restarting is adopted. Even when the boiler burner combustion is continuously operated without being stopped, the draft hunting due to switching is generally reduced, and it is normal to increase the fuel after the boiler operation becomes stable.
About 10 minutes after T-trip, the steam pressure (SOP) at the outlet of the superheater, the evaporation amount, the steam temperature at the outlet of the superheater (SOT) decrease due to the decrease in heat input, and the output of the steam turbine also decreases, which adversely affects the process. It will be.

On the other hand, when introducing GT exhaust gas into the boiler,
And conversely, even if the one being introduced is separated and bypassed to the atmosphere, it is necessary to keep the operation of both the GT and the boiler, so it is extremely careful, and the timing of damper operation and the target Depending on how the wind pressure is taken, it is possible that serious problems such as abnormal occurrence due to high GT back pressure, fire extinguishing of the burner due to backflow of boiler combustion air, and flashback will occur.

[0004]

In a combination of a gas turbine for power generation and a boiler for power generation, the pressure of the GT exhaust gas outlet is controlled to stabilize the operation of the boiler in the normal operation of GT, and when the GT trips, steam is promptly discharged. (EN) It is possible to provide a method for recovering turbine power generation to a required level and quickly enabling back-up, and an automatic operation method for a gas turbine exhaust gas reburning boiler for power generation in which operations for introducing and disconnecting GT gas are performed safely and smoothly.

[0005]

According to the present invention, a branch line with a damper D _{3 is provided} from the exhaust gas outlet side to a pipe line connecting a gas turbine exhaust gas outlet for power generation and a wind box (6a) of an exhaust gas reburning boiler. 12), the damper _{D 1,} the mixing device of the exhaust gas and the air (5) is provided, the damper so as to detect the wind pressure _{P 3} and the downstream of the wind pressure _{P 1} upstream of the damper _{D 1,} is substantially stationary the wind pressure _{P 3} D _The exhaust gas re-burning boiler for controlling No. ₃ is operated, and the damper D ₃ is controlled to maintain the wind pressure P ₃ at a temporary steady value during the trip of the gas turbine for power generation, and then the difference between the wind pressure P ₃ and the wind pressure P ₁ is maintained. When the value reaches the value specified by, the damper D ₁ is fully closed, the damper D ₃ is controlled to open so that P ₃ is always larger than P ₁ and exhaust gas does not flow backward, and the exhaust gas is discharged to generate gas turbine power generation. The exhaust reburn boiler steam with immediate and sudden This is an automatic operation method of a gas turbine exhaust gas reburning boiler for power generation, which is characterized by rapidly generating power and backing up.

During the GT trip, the temporary wind pressure P ₃ is maintained at a steady value, and when the difference between the wind pressure P ₃ and the wind pressure P ₁ reaches a specified value, the damper D ₁ is fully closed and D ₃ is P ₃ is always larger than P _{1 and} control is performed to prevent the gas from flowing backward so that exhaust gas is discharged and the gas turbine power generation is backed up by the steam power generation boiler. It is an automatic driving method.

[0007]

Embodiment 1 FIG. 1 is a drawing of an apparatus and a pipe system used for carrying out the present invention. Power generation gas turbine exhaust gas pipeline 11
A branch pipe 12 having a means for controlling the amount of exhaust gas discharged to the atmosphere and silencing is provided at the exit of the gas turbine of the above, and an exhaust gas / air mixing device 5 is provided at the inlet of the wind box 6a of the steam power generation boiler 6 in the subsequent flow. In the GT exhaust gas introduction / separation operation, the damper D ₃ is controlled so that the wind pressure P ₃ upstream of the damper D ₁ is always kept higher than the downstream wind pressure P _1, and the GT exhaust gas introduction / separation operation D ₁ and D ₃ damper operation is performed. Safe operation is possible without backflow of combustion air from the boiler side, burner extinguishing, flashback, etc., because P ₁ becomes higher than P ₃ due to abnormal GT back pressure due to timing delay.

During the trip of the power generation gas turbine 1,
The trip signal 2 is sent to the control box 3. Immediately after the GT trips, D ₁ is normally fully open and D ₃ is fully closed.
Due to the trip signal, D ₁ immediately operates in the closing direction to prevent the wind pressure P ₃ from decreasing due to the rapid decrease in the amount of GT exhaust gas. During this period, D ₃ basically remains fully closed. If the exhaust gas pressure P ₃ of the connection portion of the branch pipe of the exhaust conduit 11 and immediately opened to D _3, the exhaust gas pressure after the D ₁ stream P ₁
Therefore, the combustion air flows backward from the boiler side toward the branch pipe 12, extinguishing the burner, fear of backfire, or at least disturbing the operation control of the boiler.
(It is necessary to consider the pressure drop due to the gas flow resistance in the damper D ₁ section.)

For this reason, when D ₁ is sequentially closed, and if P ₃ becomes higher than the set value so as to maintain the P ₃ value set higher than P ₁ by a certain value, D ₃ will be automatically opened. Prevents temporary GT back pressure. However, as described above, P ₃ is always controlled to be higher than P ₁ to prevent backflow. After D _{1 is} fully closed, the draft control of D ₃ is released and it moves to full open, and after the trip, secure the GT exhaust gas passage and prepare for restart.

On the other hand, since the GT trip causes a decrease in heat input due to exhaust gas and a shortage of combustion air, in response to this, the heat input automatically increases, the air increases, and the hunting operation does not occur in the boiler. Boiler fluctuations due to trips can also be minimized.

The equipment located along the GT exhaust gas flow and the equipment located along the air flow will be described with reference to FIG. Exhaust gas from the gas turbine is damper D ₁ , low temperature economizer 13,
Damper D ₂ , mixing device 5, wind box 6a, boiler 6 furnace,
It is discharged from the chimney 10 via the high temperature economizer 14, the air heater 8, the damper D ₄ , the induction blower 9, and the damper D ₅ .
The combustion air of the boiler is sent from the atmosphere to the mixing device 5 via the damper D ₇ , the forced air blower 7, the steam type air preheater 15, the air heater 8 and the damper D ₈ . This air is mixed with the exhaust gas from the GT in the mixing device 15, is sent to the wind box 6a, and is used to burn the fuel from the burner 4.
D ₆ is a damper provided in a pipe line for recirculating exhaust gas to the forced draft fan, and is used for low NOx combustion.

With such a configuration, when the GT 1 is in a steady load operation, the exhaust gas of the gas turbine is, for example, a high temperature of about 500 ° C. and a considerable sensible heat of about 15.5% (v
Oxygen (O ₂ ) of ol%) and effectively using it for combustion are conventionally known as GT repowering systems. On the other hand, the invention of the present application is
GT atmosphere re-combustion boiler that allows safe and easy operation when T gas is introduced and separated, and that automatically operates each damper to minimize boiler fluctuations due to GT trips and switch to atmospheric combustion in a short time. It enables automatic driving.

FIG. 5 is an operation block diagram of each damper in the GT trip.

[0014]

[Embodiment 2] FIG. 2 shows an example of an exhaust gas air mixing apparatus used for carrying out the present invention. This is a case where a plurality of small holes 18 are provided in the damper blade of the damper 17 provided near the connecting portion between the exhaust gas duct and the air duct. Damper 17
Has a normal damper function and can supply a minimum amount of air even when fully closed.

As a result, a small amount of air can be injected and mixed into a large amount of exhaust gas at the time of reburning GT exhaust gas, and when the GT exhaust gas is separated and the boiler is independently burned, the damper D ₇ is opened to flow a large amount of air. You can One damper can handle exhaust combustion and atmospheric combustion without taking up space.

[0016]

Third Embodiment As an air mixing apparatus, as shown in FIG. 3, one or more air supply pipes 20 each having a plurality of small holes are provided across the exhaust gas passage, and an air supply branch pipe 21 is provided further downstream thereof. If the damper 22 for controlling the amount of air supplied from the branch pipe 21 is provided, the air-exhaust gas can be mixed efficiently, but there is a problem that the duct becomes complicated and the cost is high. Further, a mixing section in which a plurality of wire meshes are arranged in parallel may be provided downstream of the intersection of the exhaust gas flow and the air flow.

[0017]

Fourth Embodiment FIG. 4 is a vertical sectional view of the branch pipe line 12. The damper D ₃ provided here is fully closed because all the exhaust gas flows to the boiler in steady operation. However, when introducing the exhaust gas into the boiler and vice versa, the pressure P ₃ is maintained at the steady P ₁
It is controlled by a signal from the control box 3 so as to have a higher value. During the GT trip, the pressure P ₃ is kept constant for a while by the signal from the control box 3 which receives the trip signal 2. At this time, D ₃ is closed, but the damper D ₁ to the boiler side is rapidly closed, so the wind pressure of the GT exhaust gas does not become abnormally high, and the backflow gas from the boiler side that hinders boiler operation is prevented. The D ₃ damper is controlled so that it does not exist. Then damper D
₁ is fully closed, and the draft control is released at this point, and the damper D ₃ is automatically opened sequentially.

When one or more plates 19 having one or more resistance orifices 19a are arranged in parallel in the branch pipe in the wake of this damper D ₃ , this portion functions as a silencer. Since there is a plate 19 with a resistor orifice on the downstream of the damper D _3, also becomes resistance when the exhaust gas emission, this improves the controllability of the damper D _3. Moreover, the silencer can eliminate the need for a silencer. The operation of the damper D ₃ corresponds to the operation of the damper D ₁ , and there is resistance because there is a boiler facility in the downstream of the damper D ₁ . On the other hand, since there is usually no orifice in the downstream of the damper D ₃ , there is no resistance, and a large amount of gas flows even with a small opening, that is, the controllability is poor. The present invention is intended to solve this problem.

[0019]

[Embodiment 5] The control box 3 receives an output signal of a gas turbine, an atmospheric temperature signal, a boiler load signal, and an exhaust gas O ₂ signal, and a computer 3a incorporated therein controls the amount of O ₂ required by the wind box 6a. By calculating and controlling the vane opening of the forced draft blower 7, an appropriate amount of air can be fed into the wind box.

[0020] Usually measured O ₂ in the air box 6a, although decided the amount of air in order to this constant value, which in the "variation" measurement delay of O ₂ in Kazebakonai is and load of the boiler It is not possible to cope with an increase in the air volume at a large time.

[0021]

[Embodiment 6] In the operation of the exhaust gas re-burning boiler according to the present invention, the damper D ₁ is manually operated to gradually open and close the atmosphere releasing damper when switching from atmospheric combustion to exhaust combustion and vice versa. D ₃ is higher than lower wind pressure P ₁ P
_It is automatically controlled to ₃ for stable operation.

[0022]

[Embodiment 7] An air intake side duct of an FDF (pushing fan) ₇ is provided with D ₇ for controlling the amount of intake air. Immediately after the GT trip during exhaust gas re-combustion, the amount of air must be increased to burn the atmosphere. At this time D ₇
By fully opening in a short time, it can be handled together with the opening operation of the suction vane separately. An automatic control vane such as a suction vane type is provided between the D ₇ damper and the connection portion of the duct with the FDF to perform control as shown in the block diagram of FIG.

[0023]

[Embodiment 8] The following is the observation of the boiler following the follow-up at the time of trip of the gas turbine for power generation. It was confirmed that the gas turbine was tripped under the conditions of a gas turbine load of 1000 kW and a boiler load of 30 t / h, and the boiler could be operated safely. The combustion air was increased in amount from the re-combustion state to the atmospheric combustion air state that had been input to the control device in advance, the state was maintained for about 45 seconds, and then the normal automatic control operation was started. After the amount of air supplied increased, the amount of fuel supplied to the burner increased correspondingly, and after maintaining this state for about 45 seconds, normal automatic operation was started. The combustion was stable and there was no particular problem. The economizer inlet damper D ₁ and the atmospheric release damper D ₃ each operated as planned, and the gas turbine outlet pressure never increased more than necessary. It was confirmed that the main steam pressure, main steam temperature, and evaporation amount of the boiler remained almost unchanged.

[0024]

The following effects can be obtained by implementing the present invention. (1) Since the wind pressure P ₃ during the introduction and disconnection operation of GT exhaust gas is always kept higher than P ₁ , there is no backflow of combustion air in the boiler, and the TGT exhaust gas pressure does not become abnormally high and is safe and easy. It is possible to introduce or separate the exhaust gas. (2) Recovery of boiler specifications at GT trip is described below. In one example, the rated boiler evaporation rate 42T / H, SOT (superheater outlet temperature) 470 ° C., SOP (superheater outlet pressure) 8
3 atg, after performing GT trip with a combination of a steam turbine power generation boiler and GT, the conventional method reduced the amount to 33 T / H 5 minutes later, but in the present invention, the fuel supply amount can be increased immediately after tripping, so the evaporation amount No decrease is observed. In the conventional method, the SOT reached 455 ° C., but in the method of the present application, the SOT did not change. In the conventional method, the SOP was 79 atg, but in the present invention, no pressure drop was observed. (3) Since the effect of the GT trip on the boiler can be immediately backed up by the method of the present invention, the adverse effect on the plant is completely eliminated.

[0025]

[Brief description of drawings]

FIG. 1 is a drawing of the arrangement of equipment and tubing used in the practice of the present invention.

FIG. 2 is a perspective view of an apparatus for mixing exhaust gas and air.

FIG. 3 is a schematic cross-sectional view of another exhaust gas / air mixing device.

FIG. 4 is a vertical cross-sectional view of the branch pipe line 12.

FIG. 5 is a block diagram of each damper operation at the time of GT trip. 1 GT (gas turbine for power generation) 2 Trip signal 3 Control box 3a Computer 4 Burner 5 Mixer 6 Boiler 6a Wind box 7 FDF (Forced blower) 8 Air heater 9 IDF (Induction blower) 10 Chimney 11 Exhaust pipe 12 Branch pipe 13 Low temperature economizer 14 High temperature economizer 15 Steam type air preheater 16 O ₂ signal 17 Damper 18 Small hole 19 Plate 19a Resistance orifice 20 Air supply pipe 21 Air supply branch pipe 22 Damper

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Saito 1-10-10 Isogo, Isogo-ku, Yokohama, Kanagawa Bab Hitachi Engineering Services Co., Ltd. (72) Inventor Fumio Koda 6-9 Takaracho, Kure-shi, Hiroshima Prefecture No. Babkotuk Hiritsu Co., Ltd., Kure Factory (56) References JP-A-5-5405 (JP, A)

Claims (2)

(57) [Claims] 1. A branch line (12) with a damper D _{3 and a} damper D from the exhaust gas outlet side to a pipe line that connects a gas turbine exhaust gas outlet for power generation and a wind box (6a) of an exhaust gas reburning boiler.
₁ , the exhaust gas and air mixing device (5) is provided, and the damper D ₁
Of the wind pressure P _{3 on} the upstream side and the wind pressure P ₁ on the downstream side, and the exhaust gas reburning boiler is operated to control the damper D ₃ so as to make the wind pressure P ₃ almost steady. At the trip of the gas turbine for power generation, The damper D ₃ is controlled to maintain the wind pressure P ₃ at a temporary steady value, and when the difference between the wind pressure P ₃ and the wind pressure P ₁ reaches a specified value, the damper D ₁ is fully closed and the damper D ₃
Is always P ₃ gas was released in the no-opening control flow back exhaust gas is large than P _1, characterized in that it Batsukuatsupu power generation instantaneously and rapidly gas turbine power generation steam repowering boiler Automatic operation method of gas turbine exhaust reburn boiler for power generation. 2. The mixing function for enhancing mixing of exhaust gas and air is enhanced by providing a plurality of air passage small holes in a damper blade of a damper provided in an air pipeline connected to the exhaust gas pipeline. A method for automatically operating a gas turbine exhaust gas reburning boiler for power generation according to.