JP2011125765A - Flue gas denitration apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flue gas denitration apparatus avoiding wasteful consumption of a denitration catalyst when treating flue gas of a boiler employing a wide range burner. <P>SOLUTION: The flue gas denitration apparatus includes: a first denitration reactor 11 connected to the boiler B and packed with the denitration catalyst; a bypass 12 formed branched from an intermediate flue 6 continued to downstream of the first denitration reactor 11; a second denitration reactor 13 set above the bypass 12 and packed with the denitration catalyst; a bypass damper 14 blocking and releasing the flow of the flue gas to the second denitration reactor 13; a switching damper 16 switching the flow direction of the flue gas having passed through the first denitration reactor 11 to any one of the intermediate flue 6 and the bypass 12; a NOx sensor 17 measuring the NOx concentration at an outlet of the boiler; and a plant control part 19 activating the bypass damper 14 and switching damper 16 based on the NOx concentration and selecting the operation with only the first denitration reactor 11 or the operation with both the first and second denitration reactors 11, 13. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a flue gas denitration apparatus used to remove NO _x (nitrogen oxide) contained in exhaust gas discharged when fossil fuel such as coal is burned in a combustor such as a boiler. The present invention relates to a flue gas denitration apparatus suitable for a boiler employing a wide range burner.

The above-described flue gas denitration device is disposed, for example, in a flue at the coal-fired boiler outlet, and the coal combustion exhaust gas discharged from the coal-fired boiler is upstream of the denitration catalyst equipped in the flue gas denitration device. in the process of passing from the side to the downstream side, and a NO _X contained in the NH ₃ and the exhaust gas that is injected in the denitration reactor upstream portion be to denitration reaction, so as to remove the NO _X.

In such a denitrification device, as the boiler load is increased, although the NO _X concentration at the boiler outlet to remain substantially unchanged, since the amount of exhaust gas increases, the exhaust gas amount of NO _X (= NO _X Concentration x Exhaust gas amount) also increases, and the boiler load is the rated load (100%) point or the boiler maximum continuous load (MCR) is the denitration device design point (Critical-Point). The required amount of catalyst to be installed in the flue gas denitration system is planned.

  In recent years, as described in Non-Patent Document 1, a coal-fired boiler plant is also required to have an intermediate load operation such as nighttime low load operation. A wide range burner (WRB) that exhibits is apt to be adopted.

November 1995 Ishikawajima-Harima Technical Report Vol. 35, No. 6 “Practical application of internal separate type wide range burner for pulverized coal fired boiler”

Wide-range burners described above, NO _X concentration at the boiler outlet of the boiler low load range has a large increasing properties compared to conventional types of burners, NOx removal system design point (necessary catalytic planning point), It may happen that the boiler has a low load range different from the conventional high load range.

Thus, when the operation of the boiler low load region under the condition that the NOx removal system design point, i.e., when the operation by filling a denitrating catalytic amount mutually viewed in the exhaust gas amount of NO _X increases in boiler low load region, during boiler high load amount exhaust gas nO _X is reduced, not only the necessary amount of the denitration catalyst, there is a problem of deterioration will also progressing surplus denitration catalyst which is not originally required at the time of high load, to solve this problem This has been a problem in adopting wide range burners in boilers.

  The present invention has been made paying attention to the above-described conventional problems, and when used for exhaust gas treatment of boilers that employ a wide range burner, each operation mode from a high load operation mode to a low load operation mode of the boiler is used. By using an appropriate amount of denitration catalyst, wasteful consumption of the denitration catalyst can be avoided, and as a result, it is possible to provide a flue gas denitration apparatus that enables efficient operation of the denitration catalyst. It is aimed.

The present inventors, in order to plan the denitrification equipment used in boilers employing a wide-range burner, the amount of denitration each other seen in the exhaust gas amount of NO _X in the region of the boiler low load region near denitration system design point as a base Prepare a catalyst and operate it using the minimum amount of denitration catalyst among the above denitration catalysts during boiler high load operation (normal operation), while all of the above denitration catalysts during boiler low load operation Focusing on the fact that the use of the denitration catalyst can prevent the denitration catalyst from deteriorating, the present invention has been achieved.

That is, the invention according to claim 1 of the present invention removes nitrogen oxides contained in exhaust gas discharged from a combustor when fossil fuel such as coal is burned in a combustor such as a boiler. A denitration apparatus, a first denitration reactor connected to the combustor and filled with a denitration catalyst, a bypass formed by branching into a flue downstream of the first denitration reactor, A second denitration reactor disposed on the bypass and filled with a denitration catalyst, and disposed on the upstream side of the second denitration reactor on the bypass and shuts off the flow of exhaust gas to the second denitration reactor. A bypass damper, a switching damper for switching the flow direction of the exhaust gas that has passed through the first denitration reactor to one of the flue and the bypass, and NO _X that measures the nitrogen oxide concentration at the outlet of the combustor Sen And Sa, based on the NOx concentration measured by the NO _X sensor, the bypass damper and operation and the first only in the first denitration reactor switching damper is operated, the second denitration reactor It is characterized by having a plant control unit that selects operation in both, and the configuration of the flue gas denitration apparatus is used as a means for solving the above-described conventional problems.

The invention according to claim 2 of the present invention is a flue gas denitration device for removing nitrogen oxides contained in exhaust gas discharged from a combustor employing a wide range burner, wherein the exhaust gas discharged from the combustor is exhausted. A combustor monitoring unit that grasps the state of the combustor from the amount, etc., and the first denitration reactor is filled with a denitration catalyst in a minimum amount necessary for denitration during high-load operation of the combustor, the 2 denitration reactor, during an increase in the combustor exit gas amount of nO _X at the combustor low load operation, the denitration catalyst in an amount to compensate for the in the first denitration reactor not completely denitration portion is filled, the the Baipasuda with plant control unit, in the combustor monitoring unit and NO _X stage where sensor based on the acquired data from the determined to the time the combustor high load operation, the flue direction of flue gas flow by the switching damper When the operation is performed only with the first denitration reactor, and when it is determined that the combustor is in a low load region operation, the direction in which the exhaust gas flows is bypassed by the switching damper, and the bypass damper is It is configured to be opened and controlled to perform operations in both the first denitration reactor and the second denitration reactor.

  In the flue gas denitration apparatus according to the present invention, as the denitration catalyst filled in the first denitration reactor and the second denitration reactor, those having various shapes such as a honeycomb shape or a plate shape are used, and the exhaust gas flow path is crossed. In this way, multiple stages are installed.

In the flue gas denitration apparatus according to the present invention, NH ₃ is injected at the inlet of the flue gas denitration apparatus in the process in which exhaust gas generated when fossil fuel such as coal is burned in a combustor such as a boiler passes through the denitration catalyst. NO X contained in the exhaust gas _(nitrogen oxides) for removing nitrogen oxides by decomposing into nitrogen and water vapor by.

Here, in the case of a boiler employing a wide-range burner (combustor), as shown in the design plan view of FIG. 2 (a), (b), the NO _X concentration at the boiler outlet of the boiler low load region In addition, it has a characteristic that it is greatly increased (about 200 ppm → about 500 ppm) as compared with a normal type burner.

Therefore, in the flue gas denitration apparatus according to claim 1 of the present invention, the denitration process is performed only by the first denitration reactor by operating the bypass damper and the switching damper in a region where the boiler load is large, that is, in normal operation. , region boiler load is low, i.e., at the time of increasing the boiler outlet waste gas amount of NO _X in the low load operation, first to operate the bypass damper and switching damper, by to perform denitration at both the second denitration reactor For example, an amount of the denitration catalyst commensurate with the operation mode of the boiler is used, and therefore it is possible to avoid wasteful consumption of the denitration catalyst.

More specifically, as in the flue gas denitration apparatus according to claim 2 of the present invention, during normal operation in a boiler high load region, the direction in which the exhaust gas flows by the switching damper is a flue and the bypass damper is closed. uses only minimum amount of denitration catalyst filled in the first denitration reactor, whereas, at the time of the boiler outlet waste gas amount of NO _X operation in the boiler low load range, and bypasses the flow direction the exhaust gas by switching damper In addition, by opening the bypass damper and using all the denitration catalyst filled in both the first denitration reactor and the second denitration reactor, it is possible to respond to each from the high load operation mode to the low load operation mode of the boiler. As a result, a large amount of the denitration catalyst is used, so that the denitration catalyst is not consumed wastefully.

  Since the exhaust gas denitration apparatus according to claim 1 of the present invention has the above-described configuration, it is possible to avoid wasteful consumption of the denitration catalyst when used for exhaust gas treatment of boilers that employ a wide range burner. As a result, a very excellent effect that the denitration catalyst can be used efficiently is brought about.

  Moreover, in the flue gas denitration apparatus according to claim 2 of the present invention, since it has the above-described configuration, the amount corresponding to each operation mode from the high load operation mode to the low load operation mode of the boiler employing the wide range burner. By using the denitration catalyst, a very excellent effect that the denitration catalyst can be efficiently operated is brought about.

BRIEF DESCRIPTION OF THE DRAWINGS It is schematic structure explanatory drawing which shows the exhaust gas processing system of the boiler which employ | adopted the wide range burner containing the flue gas denitration apparatus by one Example of this invention. The graph (a) showing the relationship between the boiler load, NO _x , exhaust gas temperature, and exhaust gas amount when using the wide range burner that is the base for designing and designing the flue gas denitration device in Fig. 1 and a normal burner are used. boiler load and NO _X, the exhaust gas temperature in the case of a graph showing the relationship between the quantity of exhaust gas (b).

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a flue gas denitration apparatus according to an embodiment of the present invention.

As shown in FIG. 1, the flue gas denitration device 10 is connected via a vertical flue 1 to a coal-saving unit Ba of a coal-fired boiler (combustor) B that employs a wide range burner Bu. The vertical flue 1 is arranged ammonia injection nozzle (not shown) for converting by reducing NO _X by injecting ammonia into the exhaust gas to nitrogen and water vapor, while the chimney P from the denitrification device 10 A gas air heater 3, a dust collector 4, and a desulfurization unit 5 are sequentially arranged on the downstream side of the flue gas treatment flue 2 up to the above.

  The gas air heater 3 heats the external air introduced by a not-shown pushing fan with the heat of exhaust gas discharged from the flue gas denitration device 10 and sends it to the coal-fired boiler B. A heat exchanger (not shown) is also disposed between the dust collector 4 and the desulfurization unit 5. In this heat exchanger, the exhaust gas after passing through the dust collector 4 and the exhaust gas after passing through the desulfurization unit 7 are arranged. Heat exchange is performed.

  The flue gas denitration apparatus 10 includes a first denitration reactor 11 connected to the vertical flue 1, and a bypass 12 formed by branching to an intermediate flue 6 between the first denitration reactor 11 and the gas air heater 3. A second denitration reactor 13 disposed on the bypass 12 and a bypass damper disposed before and after the second denitration reactor 13 on the bypass 12 to cut off and open the flow of exhaust gas to the second denitration reactor 13 14 and 15 and a switching damper 16 for switching the flow direction of the exhaust gas that has passed through the first denitration reactor 11 to either the intermediate flue 6 or the bypass 12.

Further, the flue gas denitration apparatus 10 includes a boiler monitoring unit (combustor monitoring unit) 17 that grasps the status of the boiler B from the exhaust gas amount at the outlet of the boiler B, the fuel flow rate, the combustion air flow rate, and the like, and the NO at the outlet of the boiler B the NO _X sensor 18 for measuring the _X concentration, closing or switching the bypass damper 14, 15 and the switching damper 16 based on the data such as the outlet exhaust gas amount and NO _X concentration obtained from the boiler monitoring unit 17 and the NO _X sensor 18 A plant control unit 19 to be operated is provided.

Here, in the case of a boiler B that employs a wide-range burner Bu is FIG. 2 (a), the as shown in the design plan view of (b), the NO _X concentration at the boiler outlet of the boiler low load region, usually Higher than the type burner.
Order to meet this, the first denitration reactor 11, and denitration filled with minimum amount of denitration catalyst at the boiler high load operation (normal to the boiler outlet NO _X concentration is kept constant) ing. On the other hand, the second denitration reactor 13, a boiler at low load operation (during an increase of the boiler outlet NO _X concentration), filling the volume of the denitration catalyst that may supplement the portion which can not be denitration in the first denitration reactor 11 is doing.
In this boiler B, when the boiler load exceeds 50%, the boiler high load range is set, and when the boiler load is 50% or less, the boiler low load range is set.

That is, in the flue gas denitration apparatus 10, during normal operation in a boiler high load region, the plant control unit 19 operates the bypass dampers 14 and 15 and the switching damper 16 to perform the denitration process only with the first denitration reactor 11. while region boiler load is low, i.e., at the time of increasing the boiler outlet waste gas amount of NO _X in the low load operation, first to operate the bypass damper 14, 15 and the switching damper 16 by the plant control unit 19, a second denitration reaction The denitration process is performed in both the vessels 11 and 13.

In the flue gas denitration apparatus 10 having such a configuration, NH ₃ is injected from an ammonia injection nozzle (not shown) at the inlet of the flue gas denitration apparatus 10 in the process in which the exhaust gas generated in the coal-fired boiler B passes through the denitration catalyst. Nitrogen oxides are removed by decomposing NO _X contained in the exhaust gas into nitrogen and water vapor.

At this time, the plant control unit 19 determines the direction in which the exhaust gas flows by the switching damper 16 when the boiler is in a high load range operation based on the data acquired from the boiler monitoring unit 17 and the NO _X 18 sensor. In addition, both the bypass dampers 14 and 15 are shut off, and control is performed so that only the minimum necessary amount of the denitration catalyst charged in the first denitration reactor 11 is used.

On the other hand, the plant control unit 19 sets the direction in which the exhaust gas flows by the switching damper 16 to the bypass 12 when it is determined that the boiler is in a low load region operation based on the data acquired from the boiler monitoring unit 17 and the NO _X 18 sensor. At the same time, the bypass dampers 14 and 15 are both opened to control to use all the denitration catalysts filled in both the first denitration reactor 11 and the second denitration reactor 13.

  Therefore, in this flue gas denitration device 10, an amount of the denitration catalyst corresponding to each operation mode from the high load operation mode to the low load operation mode of the boiler B is used, and as a result, the denitration catalyst is consumed wastefully. It is possible to avoid deterioration.

  In the above-described embodiment, the case where the flue gas denitration apparatus according to the present invention is used for the exhaust gas denitration treatment of the coal fired boiler B adopting the wide range burner Bu is not limited to this, You may use for the exhaust gas denitration process of the coal fired boiler which adopted the burner.

In this case, the difference in properties of the fuel used, in a situation such as exceeding a value NO _X is assumed in the boiler outlet occurs, to use a denitration catalyst filled into the second denitration reactor 13 It will be possible to respond quickly.

  The configuration of the flue gas denitration apparatus according to the present invention is not limited to the configuration of the above-described embodiment.

6 intermediate flue 10 flue gas denitration device 11 first denitration reactor 12 bypass 13 second denitration reactors 14 and 15 bypass damper 16 switching damper 17 boiler monitoring unit (combustor monitoring unit)
18 NO _X sensor 19 Plant control part B Coal-fired boiler (combustor)
Bu wide range burner

Claims (2)

A flue gas denitration device for removing nitrogen oxides contained in exhaust gas discharged from a combustor when fossil fuel is combusted in the combustor,
A first denitration reactor connected to the combustor and filled with a denitration catalyst;
A bypass formed by branching into a flue downstream of the first denitration reactor;
A second denitration reactor disposed on the bypass and filled with a denitration catalyst;
A bypass damper disposed upstream of the second denitration reactor on the bypass to shut off and open the flow of exhaust gas to the second denitration reactor;
A switching damper for switching the flow direction of the exhaust gas that has passed through the first denitration reactor to either the flue or the bypass;
And NO _X sensor for measuring the NOx concentration at the outlet of the combustor,
Based on the concentration of nitrogen oxides measured by the NO _X sensor, the bypass damper and operation and the first only in the first denitration reactor switching damper is operated in both the second denitration reactor A flue gas denitration device comprising a plant control unit for selecting operation. A flue gas denitration device that removes nitrogen oxides contained in exhaust gas discharged from a combustor that employs a wide range burner,
A combustor monitoring unit that grasps the state of the combustor from the amount of exhaust gas discharged from the combustor and the like,
The first denitration reactor is filled with a denitration catalyst in a minimum amount necessary for denitration during high-load operation of the combustor, and the second denitration reactor is charged with exhaust gas from the combustor outlet during low-load operation of the combustor. When the amount of NO _X increases, the first denitration reactor is filled with a denitration catalyst in an amount that compensates for a portion that cannot be completely denitrated,
When the plant control unit determines that the combustor is in a high load range operation based on data acquired from the combustor monitoring unit and the NO _X sensor, the direction of the exhaust gas flowing by the switching damper is defined as a flue and the The bypass damper is shut off, and only the first denitration reactor is operated. When it is determined that the combustor is in a low load region operation, the switching damper sets the direction in which the exhaust gas flows as a bypass and the bypass damper. The flue gas denitration apparatus according to claim 1, wherein control is performed so that operation is performed in both the first denitration reactor and the second denitration reactor.

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