JPH04161229A - Denitration apparatus - Google Patents

Abstract

PURPOSE:To make denitration possible even in a low temperature range, immediate after starting, and make it possible to lower NOx even when DSS operation is carried out by installing a CO converter, an NH3 injection pipe, and a denitration reactor and installing an upper stream side NH3 injection pipe also on the upper stream of the CO converter. CONSTITUTION:A denitration apparatus 30 is composed of a CO converter 31 having a CO oxidation catalyst 33 inside which CO in a waste gas is oxidized to CO2 in a waste gas passing through a passing route 25, an NH3 injection tube 35 to spray NH3 led from an ammonia gas system 34, and a denitration reactor 32 having a denitration catalyst 36 inside to reduce NOx in the waste gas to nitrogen and water. An upper stream side NH3 injection tube 42 is installed also in the upper stream of the CO converter 31 and even at the time of starting or stopping a gas turbine in a low temperature range of the waste gas temperature, denitration is carried out by injecting the reducing agent from the upper stream side NH3 injection tube 42 and after the temperature of the waste gas becomes high, the reducing agent is injected from the NH3 injection tube 35 to carry out denitration.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a denitrification device, and more particularly to a denitrification device for a waste heat recovery boiler incorporating a C○ oxidation catalyst.

[Conventional technology] Large-capacity thermal power plants are being constructed to meet the rapidly increasing demand for electricity, but these boilers are required to operate at variable voltage in order to obtain high power generation efficiency even during partial load. ing.

This is a feature of recent electricity demand, as nuclear power generation increases, the difference between maximum and minimum loads increases, and thermal power generation tends to shift from base load to load adjustment.

In other words, in thermal power generation, there are few cases in which the boiler load is always operated at full load.
% load, operating by lowering the load, or stopping the operation, so-called high-frequency startup/shutdown (Daily
Start S top (hereinafter simply referred to as DSS) operation is carried out to shoulder intermediate loads and improve power generation efficiency.

For example, combined cycle power plants have recently been attracting attention as a part of high-efficiency power generation. This combined power generation plant first generates electricity using a gas turbine, and then recovers the heat in the exhaust gas discharged from the gas turbine using a waste heat recovery device (waste heat recovery boiler). It operates a steam turbine to generate electricity. This combined power generation plant has high power generation efficiency because it generates electricity with a gas turbine and a steam turbine, and also has quick load response, which is a characteristic of gas turbines, and is therefore able to adequately respond to sudden increases in electricity demand. It also has the advantage of excellent load followability, and is effective for DSS operation.

However, combined cycle power plants use clean fuels such as LNG and kerosene.

Although the amount of SOX and dust decreases, the amount of NOx in the exhaust gas increases due to the large amount of oxygen and high temperature combustion in gas turbine combustion, so waste heat recovery boilers with built-in denitration equipment have been developed. There is.

FIG. 4 is a schematic configuration diagram of a conventional combined cycle power plant.

The combined power generation plant includes a gas turbine device 10, a waste heat recovery boiler device 20 that generates steam using combustion gas discharged from the gas turbine device 10 as a heat source, and a parking source that uses the steam generated by the waste heat recovery boiler device 20. N discharged from the steam turbine device 40 and the gas turbine device 10
The denitrification device ff1t30 denitrates Ox.

The gas turbine device 10 includes a compressor 11 that pressurizes the introduced air 4, a combustor 14 that burns the pressurized air together with fuel supplied from the fuel system 5, a gas turbine 12 that is parked by combustion gas, and a generator that generates electricity. It is formed by machine 13.

Further, the waste heat recovery boiler device 20 is a gas turbine device 10.
The combustion gas 3 is formed by a superheater 21, an evaporator 22, a economizer 23, and a chimney 24 along the upstream to downstream direction of the combustion gas 3 led from the combustion gas 3.

Then, the steam from the superheater 21 is guided to the steam turbine device 40 via the steam pipe 2, and the load is taken by the generator 41.

The steam turbine device 4o is connected to the energy saver 2 via the water supply pipe 1.
3, and further the superheater 21 of the waste heat recovery boiler device 20
A CO converter 31 and an evaporator 2 are provided between the evaporator 22 and the evaporator 22.
A denitrification device 30 consisting of a denitrification reactor 32 is arranged between the denitrification device 2 and the economizer 23 .

The denitrification device 30 includes a CO converter 31 containing a CO oxidation catalyst 33 whose main component is platinum (Pt), which oxidizes CO in the exhaust gas to CO2, and an ammonia gas system 34 in the exhaust gas in the exhaust gas passage 25. The denitrification reactor 32 includes an NH3 injection pipe 35 that sprays NH introduced from the exhaust gas, and a denitrification catalyst 36 that reduces NOx in the exhaust gas to nitrogen and water. In addition, 37 is NH, a flow rate adjustment valve.

The denitrification reaction in the denitrification reactor 32 is generally thought to proceed through the collision of NH and No adsorbed on the denitrification catalyst 36, and the reaction is 4No+4NH, +02→4
It becomes N2+ 6 H2O, decomposes into harmless nitrogen and water, and is denitrified.

On the other hand, as the CO oxidation catalyst 33 of the CO converter 31, a platinum-based, copper-based, or iron-based catalyst such as platinum, palladium, or rhodium alone or in an alloy is used. Usually, Ti-V type is used, and its activity with respect to temperature has characteristics as shown in FIG.

Therefore, the denitrification reactor 32 is installed at a position where the exhaust gas temperature is 350 to 400°C under the planned conditions, that is, between the two divided evaporators 22 or downstream of the evaporator 22.

FIG. 6 shows an example of the change in exhaust gas temperature at the time of startup in the combined cycle power plant shown in FIG. 4. As shown in FIG.
Since the exhaust gas temperature at the inlet of No. 2 is low, the denitration rate is extremely low even if a reducing agent such as NH3 is injected, and a high concentration of unreacted reducing agent is present in the downstream of the denitration reactor 32.

Therefore, NH3 is not injected into the gas turbine 12 in low-temperature ranges such as startup and shutdown when the exhaust gas temperature is low.
The NOx generated in this case is directly discharged from the chimney 24 to the outside of the line.

[Problem to be solved by the invention] However, as mentioned above, in a combined power generation plant that performs DSS operation, a high concentration of NO is generated from the low temperature range immediately after startup.
However, the denitrification catalysts developed so far have low low-temperature activity, so if denitration is attempted at a temperature of, for example, 250° C. or lower immediately after startup, an extremely large amount of catalyst is required, which is not practical. Therefore, if exhaust gas from a combined cycle power plant is denitrated using only conventional denitrification catalysts, it becomes impossible to remove NOx generated in the low temperature range immediately after startup, and a large amount of NOx is released into the atmosphere immediately after startup. There are drawbacks to doing so.

The present invention aims to eliminate such conventional drawbacks,
The purpose of this is to be able to remove nitrogen even in the low temperature range immediately after startup, and to be able to remove nitrogen even during DSS operation.
The objective is to obtain a denitrification device that can reduce Ox.

[3 Means for Solving the Problem] In order to achieve the above-mentioned object, the present invention arranges an upstream NH3 injection pipe upstream of the CO converter.

[Function] When a reducing agent such as ammonia is injected into the CO oxidation catalyst in a low temperature range, it has a denitrification effect as a denitrification catalyst.

Therefore, even in the low temperature range, NOx is reduced by the C○ oxidation catalyst.
Since NOx is reduced to N2, a large amount of NOx is not discharged outside the system.

[Example code] Embodiments of the present invention will be described below with reference to the drawings.

Figure 1 is a schematic configuration diagram of a combined power generation plant according to an embodiment of the present invention, Figures 2 and 3 show the denitrification rate on the vertical axis and the exhaust gas temperature on the horizontal axis, and Figure 2 shows the characteristics of the CO oxidation catalyst. curve diagram,
FIG. 3 is a characteristic curve diagram of the denitrification catalyst.

In FIG. 1, numerals 1 to 41 indicate the same parts as the conventional one.

42 is an upstream side N located upstream of the C○ converter 31
H, injection pipe; 43, upstream NH; flow rate adjustment valve; 44, temperature detector for detecting the exhaust gas temperature at the entrance of the denitrification reactor 32;
45 is an upstream temperature detector that detects the inlet exhaust gas temperature of the C○ converter 31.

1, the difference from the prior art denitrification device shown in FIG. 4 is that in addition to the NH3 injection pipe 35, the C○ converter 3
1, an upstream NH injection pipe 42 is also installed upstream of the gas turbine when the gas turbine is started.

Upstream NH in low temperature range where exhaust gas temperature is low, such as when stopping.
The reducing agent is injected from the NH injection pipe 35 to perform denitration, and after the exhaust gas temperature becomes high, the reducing agent is injected from the NH injection pipe 35 to perform denitration.

FIG. 2 shows an example of the relationship between the exhaust gas temperature and the denitration rate in the CO oxidation catalyst, and FIG. 3 shows an example of the relationship between the exhaust gas temperature and the denitration rate in the denitration catalyst. Figure 2.

Example of Fig. 3: CO@ conversion catalyst 33 L;! 't 5
The denitrification rate is 50% or more at 0°C or higher, and the denitrification catalyst 36 is 180
A denitrification rate of 50% or more can be obtained at temperatures above .degree. In a normal combined cycle power plant, the exhaust gas temperature at the inlet of the denitrification reactor 32 is approximately 10% compared to the exhaust gas temperature at the inlet of the CO converter 31.
Since the temperature is about 0°C lower, in the embodiment, the inlet exhaust gas temperature of the CO converter 31 is lower than about 150°C on the upstream side N.
H, injection of a reducing agent such as ammonia through the injection pipe 42 was started, and the exhaust gas temperature at the inlet of the C○ converter 31 was approximately 250°C.
When the temperature reaches approximately 250℃, the injection of reducing agent from the NH injection pipe 35 is started, and the temperature of the exhaust gas at the entrance of the denitrification reactor 32 is about 250℃.
℃ or the inlet exhaust gas temperature of the CO converter 31 is approximately 3
When the temperature reached 00'C, the upstream NH.

By stopping the injection of the reducing agent from the injection pipe 42,
NOx can be removed in a low gravity region where the exhaust gas temperature is low, such as when the gas turbine is started or stopped. That is, in the low temperature range, the injection of the reducing agent is started from the upstream NH3 injection pipe 42 depending on the temperature of the exhaust gas at the inlet of the CO converter 31, and thereafter the temperature of the exhaust gas at the inlet of the CO converter 31 and the exhaust gas temperature at the device inlet of the denitrification reactor 32 are changed. NH3 injection pipe 35
By starting to inject more reducing agent, N at low temperatures can be reduced.
Ox removal can be achieved.

Note that the exhaust gas temperature at the inlet of the CO converter 31 and the denitrification reactor 32 is detected by the upstream temperature detector 45 and the temperature detector 44, and the injection amount of NH3 is determined by the exhaust gas temperature detected by the temperature detector 44, 45, and the upstream NH, Flow rate adjustment valve 4
3. Adjusted by NH3 flow rate adjustment valve 37.

[Effects of the Invention] According to the present invention, denitration can be performed even in a low temperature range, and NOx can be reduced even when DSS operation is performed.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram of a combined power generation plant according to an embodiment of the present invention, Figures 2 and 3 show the denitrification rate on the vertical axis and the exhaust gas temperature on the horizontal axis, and Figure 2 shows the characteristics of the CO oxidation catalyst. curve diagram,
Fig. 3 is a characteristic curve diagram of the denitrification catalyst, Fig. 4 is a schematic diagram of a conventional combined cycle power generation plant, and Fig. 5 is a characteristic curve diagram in which the vertical axis shows the activity ratio of the denitrification catalyst and the horizontal axis shows the exhaust gas temperature. FIG. 6 is a characteristic curve diagram in which the vertical axis shows exhaust gas temperature and the horizontal axis shows time. 31...C○ converter, 32...Denitration reactor, 33...CO oxidation catalyst, 35...
NH3 injection pipe, 36... denitrification catalyst, 42...
Upstream NH3 injection pipe. Figure 2 Figure 3 Size 1-1 8-ji "C"

Claims (1)

[Claims] A CO converter with a built-in CO oxidation catalyst, an NH_3 injection pipe, and a denitration reactor with a built-in denitration catalyst are arranged from upstream to downstream in the exhaust gas passage, and nitrogen oxides in the exhaust gas are denitrated. A denitrification device, characterized in that an upstream NH_3 injection pipe is disposed upstream of the CO converter.