JPH0713523B2 - Exhaust heat recovery boiler device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust heat recovery boiler device capable of recovering steam at high, medium, and low pressures by using combustion exhaust gas of a gas turbine or a diesel engine as a heat source gas, and more specifically, The present invention relates to an exhaust heat recovery boiler device equipped with a reactor having a catalyst layer for removing nitrogen oxides in combustion exhaust gas by catalytic reduction decomposition.

[Prior Art] In an exhaust heat recovery boiler device using combustion exhaust gas of a gas turbine or a diesel engine as a heat source gas, a superheater, an evaporator, and a economizer are usually sequentially arranged from the upstream side to the downstream side of the combustion exhaust gas flow. Is equipped with. Then, the feed water guided to the economizer via the water supply pipe is preheated here, vaporized by the evaporator, and further heated by the superheater to become superheated steam. Then, for example, it is introduced into the steam turbine device through the steam pipe to drive the steam turbine device and the generator.

By the way, in order to remove nitrogen oxides (NO _X ) in combustion exhaust gas, it has been widely practiced to install a denitration device in this exhaust heat recovery boiler device. It is known to have a catalyst layer that blows ammonia or hydrazine (usually ammonia) into and removes NO _X by catalytic reduction decomposition.

Such a denitrification reactor is normally used as shown in FIG.
Optimum denitration efficiency is achieved at 330 ° C to 400 ° C.

Thus, the exhaust gas temperature of the combustion exhaust gas of the gas turbine or diesel engine fluctuates significantly depending on the load condition during these periods, the temperature of the gas introduced into the denitration reactor exceeds the above-mentioned optimum range, and further, the heat damage of the reactor is caused. May reach temperatures that cause

Therefore, it has been proposed to install a denitration reactor between the economizer and the evaporator of the exhaust heat recovery boiler device (Japanese Patent Publication No. 60-
9201).

[Problems to be Solved by the Invention] However, in the exhaust heat recovery boiler device described in Japanese Patent Publication No. 60-9201, since the denitration reactor is provided on the outlet side of the evaporator, it is introduced into the denitration reactor. It is not possible to adjust only the temperature of the gas used, and it is often necessary to operate with low denitration efficiency.

In addition, unreacted reducing agent such as NH ₃ is likely to leak to the downstream side, resulting in loss of the reducing agent and SO _{X in the} combustion exhaust gas.
When gas is entrained, compounds such as NH ₄ HSO ₄ may precipitate in the latter part and cause troubles.
(Generally, NH ₄ HSO ₄ in the exhaust gas becomes a liquid phase at about 230 ° C or lower and adheres to the surface of the device, causing various troubles.

[Means for Solving Problems] An exhaust heat recovery boiler device of the present invention is an exhaust heat recovery boiler device that introduces combustion exhaust gas from a gas turbine or a diesel engine as a heat source, sequentially from the gas distribution upstream side to the downstream side. A first evaporator, a denitration reactor having a contact layer for removing nitrogen oxides in the combustion exhaust gas by catalytic reduction decomposition, a reburning burner, a superheater, a second evaporator and a economizer, The feed water heated by the economizer is introduced into the first and second evaporators, and the vapor from at least one of the evaporators is introduced into the superheater.

In the present invention, a different reheating burner may be provided between the upstream first evaporator and the denitration reactor.

[Operation] In the exhaust heat recovery boiler device of the present invention, the first evaporator is provided on the most upstream side, and the denitration reactor is provided immediately downstream thereof. Therefore, the evaporation pressure is adjusted by this first evaporator. By adjusting the amount of heat exchange using the means described above, the denitration reactor inlet temperature can be controlled to an optimum temperature of 330 to 400 ° C.

Further, as a result, the loss of the unreacted reducing agent (mainly NH ₃ ) leaking to the subsequent stage from the denitration reactor can be greatly reduced.

Furthermore, since a reburning burner is provided on the downstream side of the denitration reactor, even if a small amount of sulfur oxide is present in the combustion exhaust gas, the effect of decomposing the unreacted reducing agent due to reheating in the subsequent stage is In combination with the fact that the reducing agent leaks little, NH ₄ H
Precipitation of compounds such as SO ₄ can be suppressed and troubles can be prevented.

Embodiments Embodiments will be described below with reference to the drawings.

FIG. 1 is a system diagram of an exhaust heat recovery boiler apparatus according to an embodiment of the present invention, which is a gas turbine or diesel engine 1
From the upstream side through which the combustion exhaust gas flows, a first evaporator 2, a denitration reactor 3 having a catalyst layer for removing nitrogen oxides in the combustion exhaust gas by catalytic reduction decomposition, an additional burner 4,
A superheater 5, a second evaporator 6 and a economizer 7 are installed. Then, the feed water heated by the economizer 7 is led to the first and second evaporators 2 and 6, and the above-mentioned from at least one of the evaporators 2 and 6 (both in this embodiment) is superheated. Each device is connected by a pipe (not shown) so as to lead to.

Further, in the denitration reactor 3, a reducing agent such as ammonia or hydrazine (ammonia, NH ₃ in this embodiment) is blown into the combustion exhaust gas at the upstream portion of the reactor 3, and this ammonia is discharged. The NO _x component in the exhaust gas undergoes a denitration reaction when passing through the catalyst layer in the reactor 3. As is well known, this denitration reaction is a reaction between NO _X and NH _3.
It produces N ₂ and H ₂ O. Various kinds of catalysts such as iron oxide can be used.

As the reburning burner, those using gas or low sulfur oil as fuel are suitable.

With such a configuration, by adjusting the amount of heat exchange in the first evaporator 2, the inlet gas temperature of the denitration reactor 3 can be adjusted to 33%.
The optimum temperature can be controlled from 0 ℃ to 400 ℃.

(For example, it is possible to increase the inlet gas temperature of the reactor 3 by increasing the pressure of the vapor taken out from the first evaporator 2.) Further, in the present invention, it is provided on the upstream side of the denitration reactor. By adding equipment such as connecting an air blowing pipe, it is possible to rapidly lower the gas temperature by introducing air when the inlet gas temperature rises to 400 ° C or higher.

In addition, since the denitration reaction efficiency can be maintained at an extremely high level by setting the optimum reaction temperature of 330 to 400 ° C in this way, loss of unreacted reducing agent (mainly NH ₃ ) leaking from the denitration reactor 3 to the subsequent stage. Can be significantly reduced, and for example, the NH ₃ content on the latter stage side can be reduced to about 1 ppm or less.

Further, since the leakage of the undecomposed reducing agent to the downstream side is small as described above, even if a small amount of sulfur oxide is present in the combustion exhaust gas, unreacted reducing agent of the unreacted reducing agent due to reheating at a later stage is generated. Combined with the decomposition effect, the precipitation of compounds such as NH ₄ HSO ₄ in the latter-stage evaporator and cut-off device can be suppressed, and troubles can be prevented.

FIG. 2 is a system diagram of an exhaust heat recovery boiler device according to a different embodiment of the present invention.

In this embodiment, a different reburning burner (hereinafter referred to as a second reburning burner) is provided between the first evaporator 2 and the denitration reactor 3.
8 is different from the embodiment shown in FIG.

In addition to the effects of the embodiment of FIG. 1, the present embodiment has the effect that the temperature of the gas introduced into the denitration reactor 3 can be adjusted more easily. That is, if the inlet gas temperature of the denitration reactor 3 is lower than 330 ° C., the inlet gas temperature can be increased to 330 ° C. or higher by operating the second additional heating burner.

Since the exhaust heat recovery boiler device of the present invention is provided with the additional heating burner, even if the load of the gas turbine or the diesel engine changes, the change of the generated steam amount can be suppressed.

That is, in the conventional exhaust heat recovery boiler device that is not equipped with an additional heating burner, if the gas turbine load changes, the generated steam load also has to change, but in the present invention,
By adjusting the load (combustion amount) of the additional combustion burner to be strong or weak, it is possible to absorb the load fluctuation of the gas turbine or the diesel engine.

Furthermore, even if the load of the gas turbine or diesel engine is constant, the generated steam load can be controlled by adjusting the load of the additional burner.

FIG. 3 is a diagram showing the relationship between the generated steam load and the gas turbine or diesel engine load of such an exhaust heat recovery boiler apparatus of the present invention.

As shown, by varying the reburn burner load from minimum or stop to maximum, approximately two times the generated steam load can be adjusted. (A region surrounded by points A, B, C, and D is a range of generated steam load. Further, a line segment e is a generated steam load when the additional heating burner is stopped.) In the above embodiment, the first and second embodiments are performed. Although all of the above obtained in the evaporator of is introduced into the heater to obtain high temperature and high pressure steam, in the present invention, only the steam from one evaporator is introduced into the heater and the other evaporator is introduced. You may take out the steam as it is. For example, low pressure steam can be taken out from the second evaporator and medium pressure steam can be taken out from the first evaporator.

Further, in the present invention, it is also possible to stop the superheater and take out only medium or low pressure steam. As described above, according to the present invention, it is possible to take out steam of high, medium, and low pressures, and the response width of the steam load is extremely wide.

[Effects] As described above, the exhaust heat recovery boiler device of the present invention can reliably maintain the temperature of the gas introduced into the denitration reactor at the optimum denitration temperature, and has extremely high denitration efficiency. In addition, the catalyst also has a long life.

Further, precipitation of NH ₄ HSO _{4 and the} like on the downstream side of the denitration reactor is suppressed, and the stability of the device during long-term operation is excellent.

Furthermore, it can be used widely for load fluctuations of gas turbines and diesel engines and changes in steam load, and is extremely versatile.

[Brief description of drawings]

1 and 2 are system diagrams of an exhaust heat recovery boiler apparatus according to an embodiment, FIG. 3 is an operation characteristic diagram thereof, and FIG. 4 is an operation characteristic diagram of a denitration reactor. 2 ... first evaporator, 3 ... denitration reactor, 4 ... additional heating burner, 5 ... superheater, 6 ... second evaporator, 7 ... economizer, 8 ... second Burning burner.

Claims (1)

[Claims] 1. An exhaust heat recovery boiler apparatus for introducing combustion exhaust gas from a gas turbine or a diesel engine as a heat source, wherein the first evaporator and the combustion exhaust gas are sequentially installed from the gas distribution upstream side to the downstream side. A denitration reactor having a contact layer for removing nitrogen oxides therein by catalytic reduction decomposition, an additional burner, a superheater, a second evaporator and a economizer, and the feed water heated by the economizer is An exhaust heat recovery boiler device, characterized in that the steam is introduced into the first and second evaporators and the vapor from at least one of these evaporators is introduced into a superheater.