JP4187894B2 - Flue gas denitration method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for denitrating nitrogen oxides in exhaust gas, and more particularly to a flue gas denitration method for denitrating nitrogen oxides contained in gas turbine exhaust gas using ammonia as a reducing agent.
[0002]
[Prior art]
In general, gas turbine exhaust gas contains harmful nitrogen oxides and is not allowed to be released into the atmosphere as it causes environmental pollution. Therefore, a denitration device is provided in an exhaust heat recovery boiler that introduces exhaust gas in order to reduce the nitrogen oxides. In this denitration apparatus, nitrogen oxides and reducing substances are reacted in a catalyst to reduce them to an acceptable level that is reduced to harmless nitrogen and water. Normally, Ru is used as the reducing agent is ammonia, which mainly advantageous gaseous ammonia is used in the reaction so far.
[0003]
Gaseous ammonia is preferable because it facilitates the reaction, but there are some problems in its transportation and storage such as toxicity, and ammonia water has been used recently. When ammonia water is used, a method of blowing it directly into exhaust gas to react with nitrogen oxides, or a method of heating ammonia water with some heat source and evaporating it to supply gaseous ammonia is used.
[0004]
FIG. 3 shows ammonia vaporization means that uses exhaust gas as a heat source. The gas turbine unit includes a compressor 1, a combustor 2, and a gas turbine 3. The air compressed by the compressor 1 is guided to the combustor 2, where it is mixed with fuel to become a combustion product gas. The combustion product gas is supplied to the gas turbine 3 to expand and perform work. With this work, a generator (not shown) is driven, and an electrical output is obtained.
[0005]
The combustion product gas that has finished its work is sent to the exhaust heat recovery boiler 4 and becomes a heat source gas for the steam cycle. The exhaust heat recovery boiler 4 is provided with a denitration device 5, and an ammonia injection part 6 is disposed on the upstream side of the denitration device 5. The ammonia vaporization means includes a vaporizer 7, an exhaust gas pipe 8 that guides exhaust gas to the vaporizer 7, a supply pipe 9 that supplies ammonia, and a conduit 10 that guides the vaporized ammonia to the ammonia injection part 6. An adjustment valve 11 and a fan 12 are provided in the path of the exhaust gas pipe 8.
[0006]
Exhaust gas whose pressure and temperature are appropriately maintained using this vaporization means is introduced into the vaporizer 7 through the exhaust pipe 8, and the ammonia water sent to the vaporizer 7 through the supply pipe 9 is heated. By this heating, ammonia water evaporates, and gaseous ammonia can be obtained.
[0007]
Moreover, the example of another ammonia vaporization means is shown in FIG. In this example, a heat exchanger 14 for heating air is provided in a path of an air pipe 13 connected to the vaporizer 7. Air for diluting the ammonia water is pressurized by the fan 12, further heated by the heat exchanger 14, becomes high temperature, and is led to the vaporizer 7. Ammonia water evaporates with this high-temperature air, and gaseous ammonia can be obtained.
[0008]
As the heat source medium of the heat exchanger 14, steam generated in the exhaust heat recovery boiler 4, auxiliary steam, or the like is used. In the example shown in FIG. 4, an electric heater can be used instead of the heat exchanger 14, and the heating air can be similarly heated.
[0009]
Ammonia obtained by using such an ammonia vaporization means is supplied to the ammonia injection part 6 through the conduit 10, blown out into the exhaust gas, and used for reaction with nitrogen oxides.
[0010]
[Problems to be solved by the invention]
However, when ammonia water is vaporized by the above method, for example, if the exhaust gas contains sulfur, ammonia and sulfur may react to produce ammonium sulfate and acidic ammonium sulfate. When this ammonium sulfate and acidic ammonium sulfate are produced, these substances adhere to the superheater, evaporator, etc. of the exhaust heat recovery boiler 4 or the catalyst of the denitration device 5 to improve the heat transfer performance and denitration performance. It has a considerable influence. For example, when adhering to a heat transfer tube, heat becomes difficult to transfer due to dirt on the heat transfer surface, and the heat transfer performance is significantly reduced. In addition, these substances are corrosive and corrode the surface of the heat transfer tube.
[0011]
On the other hand, the exhaust gas used for vaporizing ammonia water is as high as 300 to 400 ° C. In order to pressurize the hot gas and send it to the vaporizer 7, the fan 12 must be operated and continued. Power costs. Further, in the case where the steam generated from the exhaust heat recovery boiler 4 is used to heat the air, the steam from the exhaust heat recovery boiler 4 cannot be obtained when the gas turbine 3 is started. Supply will be indispensable and forced operation of the auxiliary boiler will result in significant power costs.
[0012]
On the other hand, when an electric heater is used to heat the air, the power consumption of the heater is remarkably large, so that a reduction in power transmission end efficiency cannot be avoided, which is not preferable.
[0013]
Accordingly, an object of the present invention is to provide a flue gas denitration method that avoids the generation of undesirable substances such as ammonium sulfate for vaporizing ammonia water and suppresses the amount of energy input from the outside. It is in.
[0014]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided an air compressor for compressing and discharging supplied air, a combustor for burning fuel by the air discharged from the compressor, and a combustion gas of the combustor. It consists of a gas turbine to be driven, and the exhaust heat recovery boiler is arranged to ammonia injection section Contact and denitration catalyst in a duct for guiding the exhaust gas of the gas turbine, a vaporizer for vaporizing the ammonia supplied to ammonia injection unit, the air Air that has enough heat to vaporize ammonia water from the compressor is extracted, the extracted air is supplied into the vaporizer to vaporize the ammonia water in the vaporizer, and the vaporized ammonia is discharged into the exhaust heat recovery boiler. It is introduced into the exhaust gas through an ammonia injection portion therein, and is denitrated by reacting with nitrogen in the presence of a catalyst.
[0015]
In the method of the present invention, air having an amount of heat sufficient to vaporize ammonia water is extracted from the air compressor, and the extracted air is supplied into the vaporizer to vaporize the ammonia water in the vaporizer. Ammonia is introduced into exhaust gas through an ammonia injection part in an exhaust heat recovery boiler, and denitrated by reacting with nitrogen in the presence of a catalyst.
[0016]
According to such a method, ammonia water is vaporized with compressed air, so that ammonium sulfate or the like is not generated, and such substances are prevented from adhering to a heat transfer tube such as a superheater or an evaporator of an exhaust heat recovery boiler. It is possible to prevent the heat transfer performance from deteriorating. Furthermore, since compressed air generated by the equipment in the unit itself is supplied, it is not necessary to input energy from the outside, and it is possible to suppress the occurrence of excessive power costs.
[0017]
Further, the exhaust gas denitration method different from the above of the present invention includes an air compressor that compresses and discharges supplied air, a combustor that burns fuel by the air discharged from the compressor, and a combustion gas of the combustor a gas turbine driven by, while disposing the ammonia injection section Contact and denitration catalyst in a duct for guiding the exhaust gas of the gas turbine, an exhaust heat recovery boiler having a steam drum which hot water is stored during the operation of the plant, A vaporizer for vaporizing ammonia to be supplied to the ammonia injection section, the ammonia diluted air introduced into the vaporizer is heated by blow water sent from a steam drum, and the ammonia in the vaporizer is heated by the heated diluted air Water is vaporized, and this vaporized ammonia is introduced into the exhaust gas through the ammonia injection part in the exhaust heat recovery boiler, and in the presence of the catalyst. Nitrogen and reacted, characterized in that denitration.
[0018]
In the method of the present invention, the ammonia diluted air introduced into the vaporizer is heated by blow water sent from a steam drum, the ammonia water in the vaporizer is vaporized by the heated diluted air, and the vaporized ammonia is discharged. It is introduced into exhaust gas through an ammonia injection part in a heat recovery boiler, and denitrated by reacting with nitrogen in the presence of a catalyst.
[0019]
According to such a method, ammonia water is vaporized with air, so that ammonium sulfate or the like is not generated, and such substances are prevented from adhering to heat transfer tubes such as a superheater or an evaporator of an exhaust heat recovery boiler. It is possible to prevent the heat transfer performance from being deteriorated. Further, it is not necessary to input energy from the outside for vaporizing the ammonia water, and the energy consumption can be greatly reduced.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
A first embodiment of the present invention will be described with reference to the drawings. In FIG. 1, the ammonia vaporization means includes a vaporizer 7, an air pipe 15 that communicates between the air compressor 1 and the vaporizer 7, and a regulating valve 16 that is provided in the path of the air pipe 15. The air pipe 15 extracts the compressed air that vaporizes the ammonia water and guides it to the vaporizer 7. The regulating valve 16 adjusts the amount of air supplied.
[0021]
In the present embodiment, ammonia water is vaporized using the ammonia vaporization means. Air is compressed in the air compressor 1 during operation of the plant. The compressed air is supplied to the combustor 2, and a part of the compressed air is extracted and guided to the vaporizer 7 through the air pipe 15. The state of this compressed air satisfies the following conditions necessary for vaporizing ammonia water. That is, the pressure is adjusted to about 19,613 Pa (0.2 ata) and the temperature is adjusted to about 350 ° C. or higher. Usually, since the compressor 1 reaches a state in which ammonia water can be vaporized at the time of no-load rated speed operation, it is possible to secure a heat source from the start of the gas turbine.
[0022]
Further, the vaporizer 7 heats the ammonia water in the vaporizer 7 with the thermal energy held by the compressed air. This heating vaporizes ammonia water. The generated gaseous ammonia is supplied to the ammonia injection part 6 in the exhaust heat recovery boiler 4 through the conduit 10, and blown into the exhaust gas flowing therethrough to react with nitrogen oxides.
[0023]
In such a method using compressed air, since the heat source for vaporizing ammonia water is air, ammonium sulfate and acidic ammonium sulfate are not generated, and such substances flow to the exhaust heat recovery boiler 4 and adhere to heat transfer tubes and the like. It can be avoided to prevent the heat transfer performance from deteriorating. Further, it is not necessary to increase the pressure for sending the compressed air, and the required amount of air can be supplied without using a pressurizing means such as a fan.
[0024]
On the other hand, the use of compressed air has little substantial effect on the gas turbine output. For example, when a value is assumed assuming that 25 wt% ammonia water is vaporized in a 1300 ° C. class gas turbine, it can be calculated as follows. That is, the latent heat of vaporization of 25 wt% ammonia water is 2,737,644 J (654 kcal) / kg. On the other hand, the state of the compressed air at the outlet of the compressor 1 is a temperature of 350 to 400 ° C. and a pressure of 1,078,731 to 1,569,064 Pa (11 to 16 data).
[0025]
Assuming that the flow rate of ammonia water required for denitration under this condition is 0.1 kg / s, the flow rate of compressed air required to vaporize the ammonia water is 0.6 kg / s. This flow rate corresponds to about 0.1% with respect to the total air flow rate of 400 to 600 kg / s at the outlet of the compressor 1, and the influence on the gas turbine output due to the extraction of the compressed air is extremely small, and there is substantially no effect. I can say that.
[0026]
According to the present embodiment, ammonia water is vaporized with compressed air, so that ammonium sulfate or the like is not generated, and such substances adhere to heat transfer tubes such as the superheater and evaporator of the exhaust heat recovery boiler 4. This can be avoided and it is possible to prevent the heat transfer performance from deteriorating. Furthermore, since compressed air generated by the equipment in the unit itself is supplied, it is not necessary to input energy from the outside, and generation of excessive power costs can be suppressed.
[0027]
(Second Embodiment)
A second embodiment of the present invention will be described with reference to FIG. The ammonia vaporization means includes a vaporizer 7 and a heat exchanger 17 for heating the air in a path of an air pipe 13 that guides dilution air to the vaporizer 7. A hot water pipe 19 connected to the high-pressure steam drum 18 of the exhaust heat recovery boiler 4 is connected to the heat exchanger 17 and guides hot water as a heat source. A supply valve 20 is provided in the path of the hot water pipe 19. An auxiliary steam pipe 21 that guides steam as a heat source is connected to the hot water pipe 19. A supply source valve 22 is provided in the path of the auxiliary steam pipe 21.
[0028]
In the present embodiment, ammonia water is vaporized as follows using the ammonia vaporization means. During operation of the plant, hot water is stored in the high-pressure steam drum 18 of the exhaust heat recovery boiler 4. A part of the hot water, for example, blow water, is supplied to the heat exchanger 17 by opening the supply source valve 20 of the hot water pipe 19. This blow water is sent into the heat exchanger 17 by the fan 12 to heat the diluted air flowing in the heat transfer tube.
[0029]
The condition of the blow water to be supplied satisfies the following condition necessary for vaporizing the ammonia water. That is, the pressure is 10,787,315 to 12,748,645 Pa (110 to 130 at), and the temperature is 310 to 330.degree. This condition corresponds to blow water in a 1300 ° C. class gas turbine and has a sufficient amount of heat to heat the air.
[0030]
Further, the air whose temperature has been raised by heating is guided into the ammonia water in the vaporizer 7 to heat the ammonia water. This heating vaporizes ammonia water. The generated gaseous ammonia is supplied to the ammonia injection part 6 in the exhaust heat recovery boiler 4 through the conduit 10 and blown into the exhaust gas flowing therethrough to react with nitrogen oxides.
[0031]
In such a method using diluted air, since the heat source for vaporizing the ammonia water is air, ammonium sulfate and acidic ammonium sulfate are not generated, and such substances flow to the exhaust heat recovery boiler 4 and adhere to heat transfer tubes and the like. It can be avoided to prevent the heat transfer performance from deteriorating. In addition, since blow water originally discarded is used as a heat source, it is not necessary to input energy from the outside for vaporizing ammonia water, and the energy consumption can be greatly reduced.
[0032]
When it is difficult to secure the required amount of blow water, such as when starting up a gas turbine, or when it is difficult to secure sufficient heat for vaporization using only the blow water, the supply valve 22 is opened to assist from the outside. Auxiliary steam is supplied to the heat exchanger 17 through the steam pipe 21.
[0033]
According to the present embodiment, ammonia water is vaporized with air, so that ammonium sulfate or the like is not generated, and such substances are prevented from adhering to heat transfer tubes such as the superheater and evaporator of the exhaust heat recovery boiler 4. It is possible to prevent the heat transfer performance from deteriorating. Further, it is not necessary to input energy from the outside for vaporizing the ammonia water, and the energy consumption can be greatly reduced.
[0034]
【The invention's effect】
According to the present invention, since ammonia water is vaporized with air, ammonium sulfate or the like is not generated, and it is possible to avoid such substances from adhering to heat transfer tubes such as a superheater or an evaporator of an exhaust heat recovery boiler. It is possible and it can prevent that heat-transfer performance falls. Furthermore, it is not necessary to input energy from the outside for vaporizing the ammonia water, so that it is possible to suppress the generation of excessive power costs and to greatly reduce the energy consumption.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an ammonia vaporization means according to a first embodiment of the present invention.
FIG. 2 is a system diagram showing ammonia vaporization means according to a second embodiment of the present invention.
FIG. 3 is a system diagram showing an example of conventional ammonia vaporization means.
FIG. 4 is a system diagram showing another example of conventional ammonia vaporization means.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Compressor 3 Gas turbine 4 Waste heat recovery boiler 6 Ammonia injection part 7 Vaporizer 15 Air pipe 17 Heat exchanger 19 Hot water pipe 21 Auxiliary steam pipe

Claims (2)

An air compressor that compresses and discharges the supplied air, a combustor that burns fuel by the air discharged from the compressor, a gas turbine that is driven by the combustion gas of the combustor, and an exhaust gas of the gas turbine an exhaust heat recovery boiler is arranged to ammonia injection section Contact and denitration catalyst in a duct for guiding consists of a vaporizer for vaporizing the ammonia supplied to the ammonia injection section, sufficient to vaporize the aqueous ammonia from the air compressor Air having a heat quantity is extracted, the extracted air is supplied into the vaporizer to vaporize ammonia water in the vaporizer, and the vaporized ammonia is passed through the ammonia injection section in the exhaust heat recovery boiler. A flue gas denitration method characterized by denitrating by introducing it into exhaust gas and reacting with nitrogen in the presence of a catalyst. An air compressor that compresses and discharges the supplied air, a combustor that burns fuel by the air discharged from the compressor, a gas turbine that is driven by the combustion gas of the combustor, and an exhaust gas of the gas turbine with arranging the ammonia injection section Contact and denitration catalyst in a duct leading to the exhaust heat recovery boiler having a steam drum which hot water is stored during the operation of the plant, vaporizer to vaporize the ammonia supplied to the ammonia injection section The ammonia diluted air introduced into the vaporizer is heated by blow water sent from the steam drum, the ammonia water in the vaporizer is vaporized by the heated diluted air, and the vaporized ammonia is removed. It is introduced into the exhaust gas through the ammonia injection part in the exhaust heat recovery boiler and reacted with nitrogen in the presence of a catalyst to remove denitration. Flue gas denitration wherein the Rukoto.

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