JPH0794884B2 - Exhaust duct of gas turbine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust gas duct for guiding combustion gas discharged from a gas turbine to a chimney through an exhaust heat recovery boiler,
In particular, the present invention relates to an exhaust gas duct of a gas turbine that is suitable for combining exhaust gas from a plurality of gas turbines.

[Conventional technology]

The conventional device, as described in JP-A-59-7822,
In an exhaust gas duct that guides exhaust gas discharged from a gas turbine to a chimney from an exhaust heat recovery boiler, there is a system in which a damper is installed in the exhaust gas duct and an abnormal boosting prevention damper that functions as a check valve is further installed. .

Further, as shown in FIG. 3, each exhaust gas duct is separately ducted to the negative pressure portion near the chimney to join them.

[Problems to be solved by the invention]

In the former technology, in the former case, consideration is not given to keeping the exhaust pressure low when starting the next gas turbine while operating one gas turbine, and because of the exhaust gas system purge at the time of startup, When opening the outlet damper, it is necessary to increase the capacity of the starting motor or engine so that it does not flow backwards during operation so that the capacity of the starting motor or engine is large, and the equipment and power costs associated with it. However, there was a problem such as an increase in equipment cost, equipment costs for dampers, and an increase in maintenance.

Also, in the latter, there is no problem like the former, but it is necessary to separately duct to the lower part of the chimney for each gas turbine. Especially in the case of a collective chimney (often the case of supporting towers), exhaust heat recovery The duct from the boiler to the confluence near the stack becomes longer (100-150 m) in some cases). There were drawbacks that the site space increased and the duct and its supporting structure became enormous.

The object of the present invention is to maintain and improve functions and performances,
The object of the present invention is to solve the above-mentioned problems of the prior art.

[Means for solving problems]

The above-mentioned object is in the exhaust gas system of each gas turbine,
On the rear side of the exhaust heat recovery boiler, at a position closer to the exhaust heat recovery boiler than the chimney, the exhaust gas duct is united and ducted down to the lower part of the chimney by a duct with a partition plate inside, and there is no pressure near the lower part of the chimney. Alternatively, it can be achieved by forming a duct system path for joining the exhaust gases at the negative pressure portion.

As for the position of the confluence point of the exhaust gas, when one of the plurality of operating gas turbines starts up, air purging of the system is performed, but if there is exhaust pressure of another gas turbine at the confluence point,
The backflow phenomenon occurs, the air purge requires a pressure to overcome this exhaust pressure, but there is a limit in the starter (motor or engine) with limited output, and the pressure at the confluence is It must be a negative pressure or no pressure part.

The confluence position of this proposal is within the range of the ability of the starter,
Select as far upstream as possible (including the range with pressure).

Thereby, the installation range of the partition plate in the multi-system duct can be reduced, and various advantages occur.

[Action]

When merging the exhaust gas systems of a plurality of gas turbines and guiding them to the chimney, there are the following technical problems to be solved.

1. When multiple gas turbines are operating, and one of them is stopped, the gas turbine exhaust gas during continuous operation must not flow back to the stopped gas turbine side.

2. From the above conditions, when starting a gas turbine that is stopped, the gas turbine and exhaust gas system must be sufficiently purged by the compressed air pressure generated by the starting motor (or engine). (The gas turbine is usually prepared as a standard model, which is composed of standard parts. Therefore, it is often impossible to purge if there is pressure at the exhaust gas discharge end.) Therefore, the confluent part of the exhaust gas is As shown in FIG. 2, it is limited to a non-pressure or negative pressure part (near the lower part of the stack).

According to the present invention, the exhaust gas of the gas turbine is combined with the exhaust gas ducts at the position closer to the exhaust heat recovery boiler than the chimney on the rear side of each exhaust heat recovery boiler. The exhaust gas flows independently and joins at a pressureless or negative pressure portion near the lower part of the stack or at a pressure portion within a range permitted by the capacity of the starter.

Therefore, the backflow phenomenon of exhaust gas does not occur under any operating condition.

The design of the chimney is usually designed under the condition that the duct connection under the chimney has a negative pressure of 0 to 0.50 mAq.

〔Example〕

 An embodiment of the present invention will be described below with reference to FIG.

The gas turbine 1 drives the generator 2 to generate electricity. The combustion gas that has worked in the gas turbine 1 is discharged as exhaust gas, but passes through an exhaust heat recovery boiler 3 that recovers the thermal energy of the exhaust gas and generates steam, and enters an exhaust gas duct 4. The exhaust gas duct 4 merges with the exhaust gas duct 4 of another gas turbine at a position closer to the exhaust heat recovery boiler 3 than the collective chimney 8 behind the exhaust heat recovery boiler, and enters the multi-system duct 5. The inside of the multiple duct 5 is
Has a partition plate in the center and is divided into two parts on the left and right (or top and bottom),
Although it is a single duct, the interior is divided into two sections.

Exhaust gas that has passed through each system is joined to the lower part of the chimney at the confluence part 7
At the tip of the stack 8 and is discharged to the atmosphere from the tip. The horizontal load applied to the collective chimney is supported by the steel tower 9.

In this way, since the respective exhaust gases are merged at the merging portion 7 of the unpressurized or negative pressure portion, each gas turbine exhaust gas system has a function as if it were an independent exhaust gas system (system not merged). ing.

Compared with the prior art, the present embodiment balances the pressure loss of the two exhaust gas systems almost equally, reduces the amount of heat dissipated in the exhaust gas system, and reduces the decrease in exhaust gas temperature. Not only that, but by installing a multi-system duct, the plant site area can be greatly saved, and it is not necessary to install a damper in the exhaust system, improving maintenance, improving the economic efficiency of equipment, and a long exhaust gas duct. There is an effect of greatly improving the economic efficiency of the duct and its supporting equipment by simplifying the above.

〔The invention's effect〕

According to the present invention, since the exhaust gas duct system can be simplified,
It has the following effects.

1. Since the routes and shapes of the exhaust gas duct systems are almost the same, there is almost no pressure loss imbalance between the systems. Therefore, the imbalance in performance is also reduced.

Differences in the flow rate, the number of bends, the shape, and the like of the normal exhaust gas duct system greatly differ depending on the position of the stack stack as shown in FIG. Also, the greater the degree of aggregation, the greater the difference.

2.The outer surface area of the compound duct is about 25% less,
The amount of heat released to the outside can be similarly reduced, so that the exhaust gas temperature can be prevented from lowering and the draft effect in the chimney can be improved.

3. Similarly, since the heat insulation area on the outer surface of the duct is reduced, there is an effect of reducing heat insulation equipment.

4. By providing multiple ducts, the exhaust gas duct from the exhaust heat recovery boiler to the vicinity of the lower part of the chimney can be unified, and the site space can be greatly reduced. As shown in Fig. 3, the installation space of the exhaust gas duct around the stack chimney is
This is a large space that accounts for one-third of the total space of the main engine of the power plant, and the reduction effect is great.

5. Since it is not necessary to install a damper in the exhaust gas duct system after the exhaust heat recovery boiler (for the purpose of merging), the maintenance is improved, the reliability is improved, and the equipment cost (damper, supporting iron groove, operation console, power supply) Equipment) can be reduced.

6. Since multiple long exhaust gas ducts can be integrated into one, the duct body, supporting steel structure, inspection corridor, etc. can be greatly reduced, which has a great effect on the improvement of economic efficiency. (In the actual example of a 70 MW class gas turbine, it is estimated that a reduction of approximately 30 tons of steel plate per unit will be calculated.) 7. Similarly, the foundations that support the exhaust gas duct and pile equipment can be greatly reduced.

8. Since the partition plate provided in the exhaust gas duct can be effectively used as a strength member for the duct, it contributes to reducing the weight of the entire duct system.

Chimneys for releasing exhaust gas from combined-cycle power plants into the atmosphere are 150 to 200
A height of m is required. For this reason, a stack stack that is advantageous for improving the diffusion effect of exhaust gas and reducing the construction cost is adopted.

In a combined cycle power plant achieved by a large number of gas turbines, the stack chimney and each gas turbine are inevitably installed at different positions, and the exhaust gas duct from the exhaust heat recovery boiler to the chimney is 100 to 100 It often becomes as long as 150m. The present invention is to rationally design this exhaust gas duct, and the effect of the present invention increases as the number of gas turbines increases (plant output increases) and as the stacks progress. To do.

[Brief description of drawings]

FIG. 1 is a plan view showing the overall configuration of an embodiment of the present invention, FIG. 2 is a characteristic diagram showing the system head of exhaust gas pressure in an exhaust gas duct system, and FIG. 3 is a plan view showing the overall configuration in the prior art. is there. 1 ... Gas turbine, 3 ... Exhaust heat recovery boiler, 4 ... Exhaust gas duct, 5 ... Multi-system duct, 7 ... Confluence part where each exhaust gas joins, 8 ... Collect stack, 9 ... Steel tower.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-59-217413 (JP, A) JP-A-61-135940 (JP, A) Actual opening Shou 60-43831 (JP, U) Actual opening Sho-62- 70235 (JP, U) Actually open Sho 61-204144 (JP, U) Japanese Patent Sho 50-2765 (JP, B1)

Claims (1)

[Claims] 1. In an exhaust gas duct system for guiding exhaust gas of a plurality of gas turbines to a chimney through each exhaust heat recovery boiler, on the rear side of the exhaust heat recovery boiler, from the chimney to the exhaust heat recovery boiler. At the designated position, the ducts are united, and each exhaust gas flows independently up to the vicinity of the chimney, though it is one duct. An exhaust gas duct for a gas turbine, characterized in that a multi-system duct having a partition plate inside is installed.