WO2021161695A1 - Denitration device and boiler - Google Patents

Abstract

A denitration device and a boiler, each of which is provided with: a selective-reduction-type catalyst which is arranged in a gas passage; a partitioning plate which is arranged on the upstream side of the gas flow direction relative to the selective-reduction-type catalyst in the gas passage and can partition the gas passage into a plurality of zones in the direction orthogonal to the gas flow direction; and a reducing agent supply device which is arranged on the upstream side of the gas flow direction relative to the selective-reduction-type catalyst and can supply a reducing agent in an amount according to the concentration of a nitrogen oxide in a gas flowing in the plurality of zones.

Description

Denitration device and boiler

The present disclosure relates to a denitration device for removing nitrogen oxides contained in exhaust gas and a boiler equipped with a denitration device.

Large boilers such as coal-fired boilers have a hollow furnace that is installed in the vertical direction, and a plurality of combustion burners are arranged along the circumferential direction of the furnace on the furnace wall. In the boiler, the flue is connected vertically above the furnace, and a heat exchanger for generating steam is placed in the flue. A combustion burner injects a mixture of fuel and air (oxidizing gas) into the furnace to form a flame, and combustion gas is generated and flows into the flue. The heat exchanger is composed of a large number of heat transfer tubes, and the combustion gas heats water or steam flowing in the large number of heat transfer tubes to generate superheated steam.

A gas duct is connected to the flue, and a denitration device is installed in the gas duct. Nitrogen oxides are removed from the exhaust gas generated by superheated steam in the heat exchanger by the denitration device. The denitration device supplies a reducing agent such as ammonia to the exhaust gas, and when the exhaust gas and the reducing agent pass through the catalyst, the reaction between the nitrogen oxides and the reducing agent is promoted, and the nitrogen oxides in the exhaust gas are removed. do.

As such a denitration device, there is one described in the following patent documents. The flue gas denitration device described in Patent Document 1 provides a rectifying grid on the upstream side of the catalyst layer to make the flow velocity portion of the exhaust gas uniform. The denitration device described in Patent Document 2 is provided with a straightening vane on the upstream side of the ammonia injection nozzle to uniformly distribute ammonia in the exhaust gas.

Japanese Unexamined Patent Publication No. 2004-255324 Japanese Unexamined Patent Publication No. 09-024246

The exhaust gas that flows through the flue and flows into the denitration device has variations in the concentration of nitrogen oxides contained in it. The combustion burner burns by injecting a mixture of fuel and air into the furnace to generate an ascending combustion gas flow. In addition, the flue has a heat exchanger in the gas passage and is bent in the middle. Therefore, the exhaust gas flowing into the denitration device has a variation in the concentration of nitrogen oxides in the plane orthogonal to the inflow direction, and the denitration performance by the denitration device is biased. Conventionally, the supply amount of the reducing agent is adjusted according to the concentration of nitrogen oxides contained in the exhaust gas. However, since the concentration of nitrogen oxides contained in the exhaust gas varies in the plane orthogonal to the inflow direction, the nitrogen oxides cannot be sufficiently removed in the region where the amount of the reducing agent supplied to the exhaust gas is small. On the other hand, in a region where the amount of the reducing agent supplied to the exhaust gas is too large, the remaining reducing agent flows to the downstream side of the denitration device and reacts with sulfur oxides to generate ammonium sulfate, which causes the exhaust duct to be blocked. There is.

The present disclosure is to solve the above-mentioned problems, and an object of the present disclosure is to provide a denitration device and a boiler for improving performance.

The denitration device of the present disclosure for achieving the above object is provided with a selective reduction catalyst provided in the gas passage and an upstream side of the selective reduction catalyst in the gas passage in the gas flow direction to provide the gas passage. A partition plate for partitioning into a plurality of regions in a direction orthogonal to the gas flow direction, and an amount provided on the upstream side of the selective reducing catalyst in the gas flow direction according to the nitrogen oxide concentration of the gas flowing through the plurality of regions. It is provided with a reducing agent supply device for supplying the reducing agent of the above.

Further, the boiler of the present disclosure includes a furnace installed along the vertical direction, a combustion device arranged in the furnace, a flue arranged on the downstream side in the flow direction of combustion gas in the furnace, and the smoke. It includes a heat exchanger arranged on the road and a denitration device arranged on the downstream side of the heat exchanger in the flue.

According to the denitration device and the boiler of the present disclosure, the performance can be improved.

FIG. 1 is a schematic view showing the boiler of the first embodiment. FIG. 2 is a schematic configuration diagram showing the denitration device of the first embodiment. FIG. 3 is a schematic view showing the operation of the denitration device of the first embodiment. FIG. 4 is a perspective view showing the arrangement of the first partition plate. FIG. 5 is a schematic configuration diagram showing the denitration device of the second embodiment. FIG. 6 is a schematic plan view showing the denitration device of the second embodiment. FIG. 7 is a schematic front view showing the denitration device of the third embodiment. FIG. 8 is a schematic plan view showing the denitration device of the third embodiment.

The preferred embodiments of the present disclosure will be described in detail with reference to the drawings below. It should be noted that the present disclosure is not limited by this embodiment, and when there are a plurality of embodiments, the present embodiment also includes a combination of the respective embodiments. In addition, the components in the embodiment include those that can be easily assumed by those skilled in the art, those that are substantially the same, that is, those in a so-called equal range.

[First Embodiment]
FIG. 1 is a schematic view showing the boiler of the first embodiment.

[Boiler configuration]
The coal-fired boiler 10 of the first embodiment uses pulverized coal obtained by crushing coal (carbon-containing solid fuel) as pulverized fuel, burns the pulverized fuel with a combustion burner, and exchanges heat generated by combustion with water supply or steam. It is a boiler that can generate superheated steam. In the following description, "upper" and "upper" mean the upper side in the vertical direction, and "lower" and "lower" mean the lower side in the vertical direction.

In the first embodiment, as shown in FIG. 1, the coal-fired boiler 10 has a furnace 11, a combustion device 12, and a combustion gas passage 13. The furnace 11 has a hollow shape of a square cylinder and is installed along the vertical direction. The furnace wall (heat transfer tube) 11a constituting the furnace 11 is composed of a plurality of evaporation pipes and fins connecting the plurality of evaporation pipes, and exchanges heat generated by combustion of pulverized fuel with water supply or steam. Therefore, the temperature rise of the furnace wall is suppressed.

The combustion device 12 is provided on the lower side of the furnace wall 11a. The combustion device 12 has a plurality of combustion burners 21, 22, 23, 24, 25 mounted on the furnace wall 11a. The combustion burners 21, 22, 23, 24, 25 are arranged at arbitrary intervals along the circumferential direction of the furnace 11 as one set, and have a plurality of stages along the vertical direction (five stages in the present embodiment). ) Placed. However, the shape of the furnace 11, the number of combustion burners in one stage, and the number of stages of combustion burners are not limited to this configuration.

The combustion burners 21, 22, 23, 24, 25 are connected to a plurality of crushers (mills) 31, 32, 33, 34, 35 via the pulverized coal supply pipes 26, 27, 28, 29, 30. Although not shown, the crushers 31, 32, 33, 34, and 35 are not shown, but for example, a rotary table is rotatably supported in a housing, and a plurality of rollers rotate in conjunction with the rotation of the rotary table above the rotary table. It is configured to be supported as possible. When coal is thrown between a plurality of rollers and a rotary table, it is crushed to a predetermined size of pulverized coal and transported to a classifier by a transport gas (primary air, oxidizing gas) to a predetermined size. Classified within the size range. The pulverized fuel classified within a predetermined size range is supplied from the pulverized coal supply pipes 26, 27, 28, 29, 30 to the combustion burners 21, 22, 23, 24, 25.

In the furnace 11, a wind box 36 is provided at the mounting position of the combustion burners 21, 22, 23, 24, 25, and one end of the air duct (air passage) 37 is connected to the wind box 36. A push-in ventilator (FDF: Forced Draft Fan) 38 is connected to the other end of the air duct 37. The furnace 11 is provided with an additional air port 39 above the mounting positions of the combustion burners 21, 22, 23, 24, 25. The end of the additional air duct 40 branched from the air duct 37 is connected to the additional air port 39.

The combustion gas passage 13 is connected to the upper part of the furnace 11 in the vertical direction. The combustion gas passage 13 is provided with superheaters 51, 52, 53, reheaters 54, 55, and economizer 56 as heat exchangers for recovering the heat of the combustion gas. The superheaters 51, 52, 53, the reheaters 54, 55, and the economizer 56 exchange heat between the combustion gas generated by the combustion in the furnace 11 and the water supply or steam flowing through the heat transfer tube.

The combustion gas passage 13 is connected to the flue 41 from which the combustion gas that has undergone heat exchange is discharged on the downstream side. An air heater (air preheater) 42 is provided between the flue 41 and the air duct 37. The air flowing through the air duct 37 exchanges heat with the combustion gas flowing through the flue 41, and raises the temperature of the combustion air supplied to the combustion burners 21, 22, 23, 24, 25.

The flue 14 is provided with a denitration device 43 at a position upstream of the air heater 42. The denitration device 43 supplies a reducing agent having an action of reducing nitrogen oxides (NOx) such as ammonia and urea water into the flue 41. In the combustion gas to which the reducing agent is supplied, the reaction between the nitrogen oxides and the reducing agent is promoted, and the nitrogen oxides in the combustion gas are removed and reduced. A gas duct 44 is connected to the downstream side of the flue 41. The gas duct 44 is provided with a dust collector 45 such as an electric dust collector, an induction ventilator (IDF: Induced Draft Fan) 46, a desulfurization device 47, etc. at a position downstream of the air heater 42, and a chimney 48 is provided at the downstream end. ..

[Boiler action]
When a plurality of crushers 31, 32, 33, 34, 35 are driven, the generated pulverized fuel is burned together with the transport gas (primary air, oxidizing gas) through the pulverized coal supply pipes 26, 27, 28, 29, 30. It is supplied to the burners 21, 22, 23, 24, 25. Further, the combustion air (oxidizing gas) heated by exchanging heat with the exhaust gas discharged from the flue 14 by the air heater 42 is sent from the air duct 37 through the air box 36 to each combustion burner 21, 22, 23. , 24, 25 are supplied. Then, the combustion burners 21, 22, 23, 24, 25 blow the pulverized fuel mixture, which is a mixture of the pulverized fuel and the transport gas, into the furnace 11, and also blow the combustion air into the furnace 11. At this time, a flame is formed by igniting the fine fuel mixture. A flame is generated in the lower part of the furnace 11, the high-temperature combustion gas rises, and is discharged to the combustion gas passage 13.

In the furnace 11, in the lower region A, the pulverized fuel mixture and the combustion air (secondary air, oxidizing gas) burn to generate a flame. The inside of the furnace 11 is maintained in a reducing atmosphere by setting the air supply amount to be less than the theoretical air amount with respect to the pulverized coal supply amount in the region A. That is, the nitrogen oxides (NOx) generated by the combustion of the pulverized coal are reduced in the region B of the furnace 11, and the additional air is additionally supplied from the additional air port 39 to complete the oxidative combustion of the pulverized coal. The amount of NOx generated by combustion is reduced.

The combustion gas that has risen in the furnace 11 is the second superheater 52, the third superheater 53, the first superheater 51, the second reheater 55, the first reheater 54, which are arranged in the combustion gas passage 13. Heat is exchanged with the economizer 56. After that, nitrogen oxides were reduced and removed from the combustion gas by the denitration device 43, particulate matter was removed by the dust collector 45 arranged in the gas duct 44, and sulfur oxides were removed by the desulfurization device 47. It is discharged into the atmosphere from the chimney 48.

[Configuration of denitration device]
FIG. 2 is a schematic configuration diagram showing the denitration device of the first embodiment, FIG. 3 is a schematic view showing the operation of the denitration device of the first embodiment, and FIG. 4 is a perspective view showing the arrangement of the first partition plate. be.

The flue (gas passage) 41 includes a first horizontal flue section 41a, a first vertical flue section 41b, a second horizontal flue section 41c, a second vertical flue section 41d, and a third horizontal flue section (horizontal passage). ) 41e and the third vertical flue section (vertical passage) 41f are continuously provided. In the flue 41, superheaters 51, 52, 53, reheaters 54, 55, and economizer 56 are arranged in the first horizontal flue portion 13a and the first vertical flue portion 13b. Further, in the flue 41, the denitration device 43 is arranged from the second vertical flue portion 41d to the third vertical flue portion 41f via the third horizontal flue portion 41e.

The denitration device 43 includes a selective reduction catalyst 61, a plurality of (three in this embodiment) first partition plates 62, 63, 64, and a reducing agent supply device 65.

As shown in FIGS. 2 to 4, the selective reduction catalyst 61 is a denitration catalyst and is provided in the third vertical flue portion 41f of the flue 41. In the selective reduction catalyst 61, a reducing agent such as ammonia or urea water is supplied to the exhaust gas to promote the reaction between the nitrogen oxide and the reducing agent in the exhaust gas to which the reducing agent is supplied. To remove and reduce nitrogen oxides in exhaust gas.

The first partition plates 62, 63, 64 are provided across the second vertical flue portion 41d, the third horizontal flue portion 41e, and the third vertical flue portion 41f of the flue 41. The first partition plates 62, 63, 64 are provided on the upstream side in the gas flow direction from the selective reduction catalyst 61 in the flue 41. The first partition plates 62, 63, 64 have a plurality of (four in this embodiment) mixed passages (regions) 70a, 70b, 70c, 70d in the width direction orthogonal to the gas flow direction in the gas passage of the flue 41. Partition into.

The mixing passages 70a, 70b, 70c, 70d are parallel to the gas flow direction and parallel to the width direction at the second vertical flue section 41d, the third horizontal flue section 41e, and the third vertical flue section 41f. Is placed. Here, the width direction is a horizontal direction orthogonal to the gas flow direction of the third horizontal flue portion 41e. Further, the mixing passages 70a, 70b, 70c, and 70d have the same length L in the gas flow direction. Here, the length L in the gas flow direction is the length of the center of the flue 41.

The mixing passages 70a, 70b, 70c, and 70d have the same dimensions as the lengths W1, W2, W3, and W4 in the width direction orthogonal to the gas flow direction. The lengths W1, W2, W3, and W4 of the mixing passages 70a, 70b, 70c, and 70d in the width direction are constant in the gas flow direction. The lengths W1, W2, W3, and W4 in the width direction may have different dimensions. When the exhaust gas reaches the mixing passages 70a, 70b, 70c, 70d, the exhaust gas has a variation in the concentration of nitrogen oxides in the width direction. Therefore, it is preferable that the lengths W1, W2, W3, and W4 in the width direction in the mixing passages 70a, 70b, 70c, and 70d are appropriately set according to the concentration distribution of nitrogen oxides in the gas, the layout of the flue 41, and the like. ..

Further, the mixing passages 70a, 70b, 70c, and 70d have dimensions longer than the lengths W1, W2, W3, and W4 in the width direction in which the length L in the gas flow direction is orthogonal to the gas flow direction.

The first partition plates 62, 63, 64 have a shape that matches the shapes of the second vertical flue portion 41d, the third horizontal flue portion 41e, and the third vertical flue portion 41f in the flue 41. Therefore, if the shapes of the second vertical flue portion 41d, the third horizontal flue portion 41e, and the third vertical flue portion 41f change, the shapes of the first partition plates 62, 63, 64 also change. Further, the first partition plates 62, 63, 64 straddle the second vertical flue section 41d, the third horizontal flue section 41e, and the third vertical flue section 41f, but only the third vertical flue section 41f. It may be provided only in the third horizontal flue portion 41e and the third vertical flue portion 41f, or it may be provided only in the third horizontal flue portion 41e. Further, the number of the first partition plates 62, 63, 64 is not limited to three, and may be one or four or more.

The reducing agent supply device 65 is the third vertical flue portion 41f of the flue 41, and is provided between the first partition plates 62, 63, 64 and the selective reduction catalyst 61. That is, the reducing agent supply device 65 is arranged on the downstream side of the first partition plates 62, 63, 64 and on the upstream side of the selective reduction catalyst 61. The reducing agent supply device 65 supplies a reducing agent having an action of reducing nitrogen oxides such as ammonia and urea water to the third vertical flue portion 41f.

The reducing agent supply device 65 includes a reducing agent supply pump 71 and a plurality of (four in this embodiment) reducing agent supply pipes 72a, 72b, 72c, 72d. The reducing agent supply pipes 72a, 72b, 72c, 72d are arranged in the third vertical flue portion 41f. A plurality of nozzles 73a, 73b, 73c, 73d are mounted on the reducing agent supply pipes 72a, 72b, 72c, 72d. The plurality of nozzles 73a, 73b, 73c, 73d are arranged toward the downstream side in the gas flow direction, but may be arranged toward the upstream side in the gas flow direction. A reducing agent supply pump 71 is connected to the end of the reducing agent supply pipes 72a, 72b, 72c, 72d.

The reducing agent supply pipes 72a, 72b, 72c, 72d and the nozzles 73a, 73b, 73c, 73d are arranged corresponding to the mixing passages 70a, 70b, 70c, 70d. The reducing agent supply device 65 is arranged at the outlet of the mixing passages 70a, 70b, 70c, 70d, supplies the reducing agent to the exhaust gas discharged from the mixing passages 70a, 70b, 70c, 70d, and selectively reduces the catalyst. The reducing agent is diffused in the exhaust gas before flowing into 61. As the reducing agent, aqueous ammonia, gaseous ammonia, urea water, or the like can be used.

A control device 66 is connected to the reducing agent supply device 65. By controlling the reducing agent supply device 65, the control device 66 supplies an amount of the reducing agent according to the concentration of nitrogen oxides in the exhaust gas flowing through the mixing passages 70a, 70b, 70c, and 70d. In this case, it is desirable to obtain the concentration of nitrogen oxides in the exhaust gas flowing through the mixing passages 70a, 70b, 70c, and 70d by prior experiments, measurements, and estimations. Further, a measuring instrument for measuring the concentration of nitrogen oxides in the exhaust gas may be provided in the mixing passages 70a, 70b, 70c, 70d, and the concentration of nitrogen oxides may be measured online. Here, the control device 66 adjusts the supply amount of the reducing agent supplied by the reducing agent supply device 65 to the mixing passages 70a, 70b, 70c, 70d according to the required denitration rate.

[Action of denitration device]
In the denitration device 43, as shown in FIGS. 2 and 3, the exhaust gas flowing through the flue 41 rises through the second vertical flue section 41d and then flows horizontally through the third horizontal flue section 41e, and the third It descends the vertical flue section 41f. At this time, the exhaust gas is distributed to the four mixing passages 70a, 70b, 70c, 70d partitioned in the width direction by the first partition plates 62, 63, 64, and the mixing passages 70a, 70b, 70c, 70d are designated. Only the length L flows.

The exhaust gas flowing through the flue 41 becomes exhaust gas in the width direction, for example, due to the swirling flow of the combustion gas flow generated in the combustion gas passage 13, the heat exchanger arranged in the flue 41, the intermediate shape of the flue 41, and the like. There are variations in the concentration of nitrogen oxides contained. For example, the concentration C0 of nitrogen oxides contained in the exhaust gas is lower on the upstream side of the mixing passages 70a, 70b, 70c, 70d, on the mixing passage 70a side in the width direction, and goes to the mixing passage 70d side. The higher it gets.

Exhaust gas having a difference in nitrogen oxide concentration in the width direction of the flue 41 flows into the mixing passages 70a, 70b, 70c, 70d and flows through the mixing passages 70a, 70b, 70c, 70d by a predetermined length L. Be mixed. The exhaust gas that has individually flowed through the mixing passages 70a, 70b, 70c, and 70d has a substantially uniform nitrogen oxide concentration difference at the outlets of the mixing passages 70a, 70b, 70c, and 70d. That is, in a wide flue in which the first partition plates 62, 63, 64 are not arranged, the exhaust gas is not sufficiently mixed even if it flows by a predetermined length L, and the concentration difference of nitrogen oxides in the width direction is large. Occurs. On the other hand, in the narrow mixing passages 70a, 70b, 70c, 70d partitioned by the first partition plates 62, 63, 64, the exhaust gas is sufficiently mixed while flowing a predetermined length L, and nitrogen oxidation occurs in the width direction. Differences in the concentration of substances are unlikely to occur. Comparing the exhaust gases flowing through the mixing passages 70a, 70b, 70c, and 70d, the concentrations of nitrogen oxides contained in the exhaust gas are different from each other (see FIG. 3) (C1 <C2 <C3 <). There is C4). However, when only the exhaust gas flowing through the mixing passages 70a, 70b, 70c, and 70d is compared in the width direction, the concentrations of nitrogen oxides C1, C2, C3, and C4 (see FIG. 3) contained in the exhaust gas are in the width direction. There is almost no difference in concentration.

When the exhaust gas flowing through the mixing passages 70a, 70b, 70c, 70d is discharged to the third vertical flue portion 41f, the reducing agent is supplied from the reducing agent supply device 65. At this time, the control device 66 controls the reducing agent supply device 65 to apply an amount of the reducing agent to the exhaust gas flowing through the mixing passages 70a, 70b, 70c, 70d according to the concentration of the nitrogen oxide contained therein. Supply. That is, for exhaust gas discharged from the mixing passages 70a, 70b, 70c, 70d and having different nitrogen oxide concentrations C1, C2, C3, C4, the nozzles 73a, 73b of the reducing agent supply pipes 72a, 72b, 72c, 72d. , 73c, 73d are injected with different amounts of reducing agent. Specifically, the minimum amount of the reducing agent is injected from the nozzle 73a of the reducing agent supply pipe 72a to the exhaust gas discharged from the mixing passage 70a and having a low concentration of nitrogen oxides. On the other hand, the maximum amount of the reducing agent is injected from the nozzle 73d of the reducing agent supply pipe 72d to the exhaust gas discharged from the mixing passage 70d and having a high concentration of nitrogen oxides.

When the reducing agent is supplied to the exhaust gas from the reducing agent supply device 65, the exhaust gas flows into the selective reduction catalyst 61 in a state where the reducing agent is mixed. The selective reduction catalyst 61 promotes the reaction between the nitrogen oxides in the exhaust gas and the reducing agent, reduces the nitrogen oxides, and removes and reduces the nitrogen oxides in the exhaust gas. At this time, since the reducing agent in an amount corresponding to the content of nitrogen oxides is supplied to the exhaust gas having different concentrations C1, C2, C3, and C4 and then flows into the selective reducing catalyst 61, the selective reducing catalyst Nitrogen oxides are efficiently reduced and removed by 61. That is, the supply amount of the reducing agent to the exhaust gas is small, and it is suppressed that the removal of nitrogen oxides is insufficient. In addition, the amount of the reducing agent supplied to the exhaust gas is large, and it is suppressed that the remaining reducing agent reacts with the sulfur oxide to generate ammonium sulfate.

[Second Embodiment]
FIG. 5 is a schematic configuration diagram showing the denitration device of the second embodiment, and FIG. 6 is a schematic plan view showing the denitration device of the second embodiment. The members having the same functions as those of the first embodiment described above are designated by the same reference numerals, and detailed description thereof will be omitted.

In the second embodiment, as shown in FIGS. 5 and 6, the denitration device 43A promotes mixing of the selective reduction catalyst 61, the plurality of first partition plates 62, 63, 64, and the reducing agent supply device 65. The device 81 is provided. Here, since the selective reduction catalyst 61, the first partition plates 62, 63, 64 and the reducing agent supply device 65 are the same as those in the first embodiment, detailed description thereof will be omitted.

The selective reduction catalyst 61 is provided in the third vertical flue section 41f of the flue 41. The first partition plates 62, 63, 64 are provided so as to straddle the second vertical flue portion 41d, the third horizontal flue portion 41e, and the third vertical flue portion 41f of the flue 41. The first partition plates 62, 63, 64 are provided on the upstream side in the gas flow direction from the selective reduction catalyst 61 in the flue 41. The first partition plates 62, 63, 64 divide the gas passage of the flue 41 into four mixed passages 70a, 70b, 70c, 70d in the width direction orthogonal to the gas flow direction. The reducing agent supply device 65 is a third vertical flue portion 41f of the flue 41, and is provided between the first partition plates 62, 63, 64 and the selective reduction catalyst 61.

The mixing promotion device 81 is provided in the gas inflow portion in the four mixing passages 70a, 70b, 70c, 70d partitioned by the first partition plates 62, 63, 64. The mixing accelerator 81 has a plurality of (four in this embodiment) mixing accelerators 81a, 81b, 81c, 81d. The mixing accelerators 81a, 81b, 81c, 81d are arranged at the upstream end in the gas flow direction in the four mixing passages 70a, 70b, 70c, 70d partitioned by the first partition plates 62, 63, 64. .. That is, the mixing accelerators 81a, 81b, 81c, 81d are arranged at positions sandwiched between the upstream end portions in the gas flow direction of the first partition plates 62, 63, 64.

The mixing accelerator 81 (mixing accelerator 81a, 81b, 81c, 81d) is, for example, a swirling flow generator, and applies a swirling force to the exhaust gas flowing into the mixing passages 70a, 70b, 70c, 70d. The exhaust gas flowing into the mixing passages 70a, 70b, 70c, and 70d is mixed by applying a swirling force, the nitrogen oxide concentration difference disappears, and the nitrogen oxide concentration in the width direction and the height direction increases. Become uniform.

The mixing promotion device 81 is not limited to the swirling flow generator. For example, a plurality of resistance plates with which the exhaust gas collides may be provided to form a turbulent flow in the mixing passages 70a, 70b, 70c, 70d, or other devices may be used. Further, the mixing accelerators 81a, 81b, 81c, 81d were arranged at the upstream end of the mixing passages 70a, 70b, 70c, 70d, but not in the mixing passages 70a, 70b, 70c, 70d, but in the mixing passages 70a, 70b. , 70c, 70d may be arranged immediately upstream.

Therefore, in the denitration device 43A, the exhaust gas flowing through the flue 41 rises in the second vertical flue section 41d, then flows horizontally in the third horizontal flue section 41e, and descends in the third vertical flue section 41f. .. At this time, the exhaust gas is distributed to the four mixing passages 70a, 70b, 70c, 70d partitioned in the width direction by the first partition plates 62, 63, 64. Then, when the exhaust gas flows into the mixing passages 70a, 70b, 70c, 70d, the mixing is promoted by applying a turning force by the mixing accelerators 81a, 81b, 81c, 81d, and the mixing passages 70a, 70b, 70c. At 70d, the difference in nitrogen oxide concentration is reduced. The exhaust gas that has flowed through the mixing passages 70a, 70b, 70c, and 70d by a predetermined length L has a substantially uniform nitrogen oxide concentration difference at the outlets of the mixing passages 70a, 70b, 70c, and 70d.

The reducing agent is supplied from the reducing agent supply device 65 to the exhaust gas discharged from the mixing passages 70a, 70b, 70c, 70d to the third vertical flue portion 41f. At this time, the control device 66 controls the reducing agent supply device 65 to apply an amount of the reducing agent to the exhaust gas flowing through the mixing passages 70a, 70b, 70c, 70d according to the concentration of the nitrogen oxide contained therein. Supply. Then, the exhaust gas flows into the selective reduction catalyst 61 in a state where the reducing agent is mixed. The selective reduction catalyst 61 promotes the reaction between the nitrogen oxides in the exhaust gas and the reducing agent, reduces the nitrogen oxides, and removes and reduces the nitrogen oxides in the exhaust gas. At this time, since the reducing agent in an amount corresponding to the content of the nitrogen oxide is supplied to the exhaust gas having different concentrations and then flows into the selective reduction type catalyst 61, the nitrogen oxide is efficiently produced by the selective reduction type catalyst 61. It is often reduced and removed.

[Third Embodiment]
FIG. 7 is a schematic front view showing the denitration device of the third embodiment, and FIG. 8 is a schematic plan view showing the denitration device of the third embodiment. The members having the same functions as those of the first embodiment described above are designated by the same reference numerals, and detailed description thereof will be omitted.

In the third embodiment, as shown in FIGS. 7 and 8, the denitration device 43B includes the selective reducing catalyst 61 and a plurality of (three in this embodiment) second partition plates 91, 92, 93. A reducing agent supply device 65 is provided. Here, since the selective reduction catalyst 61 and the reducing agent supply device 65 are the same as those in the first embodiment, detailed description thereof will be omitted.

The selective reduction catalyst 61 is a denitration catalyst and is provided in the third vertical flue portion 41f of the flue 41.

The second partition plates 91, 92, 93 are provided in the third vertical flue portion 41f of the flue 41. The second partition plates 91, 92, and 93 are provided on the upstream side in the gas flow direction from the selective reduction catalyst 61 in the flue 41. The second partition plates 91, 92, 93 have a plurality of (four in this embodiment) mixed passages (regions) 94a, 94b, 94c, 94d in the depth direction orthogonal to the gas flow direction in the gas passage of the flue 41. Partition into.

The mixing passages 94a, 94b, 94c, 94d are arranged along the gas flow direction and in parallel in the depth direction at the third vertical flue portion 41f. Here, the depth direction is a horizontal direction (horizontal direction in FIG. 7) orthogonal to the gas flow direction and the width direction of the third vertical flue portion 41f. Further, the mixing passages 94a and 94b have the same length in the gas flow direction, and the length in the gas flow direction (length in the vertical direction) in the mixing passages 94c and 94d is the length of the third vertical flue portion 41f. The ceiling portion may have an appropriate length in consideration of the layout of the flue 41, denitration efficiency, required performance, etc., regardless of the inclination.

Although the second partition plates 91, 92, and 93 are provided in the third vertical flue portion 41f in the flue 41, they may be provided in the second vertical flue portion 41d and the third horizontal flue portion 41e.

The reducing agent supply device 65 is the third vertical flue portion 41f of the flue 41, and is provided between the partition plates 91, 92, 93 and the selective reduction catalyst 61. That is, the reducing agent supply device 65 is on the downstream side of the partition plates 91, 92, 93 and on the upstream side of the selective reduction catalyst 61. The reducing agent supply device 65 supplies a reducing agent having an action of reducing nitrogen oxides such as ammonia and urea water to the third vertical flue portion 41f.

The reducing agent supply pipes 72a, 72b, 72c, 72d and the nozzles 73a, 73b, 73c, 73d are arranged corresponding to the mixing passages 94a, 94b, 94c, 94d. The reducing agent supply device 65 is arranged at the outlet of the mixing passages 94a, 94b, 94c, 94d, supplies the reducing agent to the exhaust gas discharged from the mixing passages 94a, 94b, 94c, 94d, and selectively reduces the catalyst. The reducing agent is diffused in the exhaust gas before flowing into 61.

A control device 66 is connected to the reducing agent supply device 65. By controlling the reducing agent supply device 65, the control device 66 supplies an amount of the reducing agent according to the concentration of nitrogen oxides in the exhaust gas flowing through the mixing passages 94a, 94b, 94c, 94d. Here, the control device 66 adjusts the supply amount of the reducing agent supplied by the reducing agent supply device 65 to the mixing passages 70a, 70b, 70c, 70d according to the required denitration rate.

Therefore, in the denitration device 43B, the exhaust gas flowing through the flue 41 descends from the third vertical flue portion 41f, and is divided in the depth direction by the second partition plates 91, 92, 93. , 94c, 94d, and flows through the mixing passages 94a, 94b, 94c, 94d for a predetermined length.

Exhaust gas having a difference in nitrogen oxide concentration in the height (depth) direction of the flue 41 flows into the mixing passages 94a, 94b, 94c, 94d, and flows through the mixing passages 94a, 94b, 94c, 94d by a predetermined length. Mixed while flowing. The exhaust gas that has individually flowed through the mixing passages 94a, 94b, 94c, 94d has a substantially uniform nitrogen oxide concentration difference at the outlets of the mixing passages 94a, 94b, 94c, 94d. That is, when the exhaust gases flowing through the mixing passages 94a, 94b, 94c, and 94d are compared with each other, there is a difference in the concentration of nitrogen oxides contained in the exhaust gas. However, when only the exhaust gases flowing through the mixing passages 94a, 94b, 94c, and 94d are compared in the width direction, the concentrations of nitrogen oxides contained in the exhaust gas have almost no difference in the depth direction.

When the exhaust gas flowing through the mixing passages 94a, 94b, 94c, 94d is discharged to the third vertical flue portion 41f, the reducing agent is supplied from the reducing agent supply device 65. At this time, the control device 66 controls the reducing agent supply device 65 to apply an amount of the reducing agent to the exhaust gas flowing through the mixing passages 94a, 94b, 94c, 94d according to the concentration of the nitrogen oxide contained therein. Supply. That is, different amounts from the nozzles 73a, 73b, 73c, 73d of the reducing agent supply pipes 72a, 72b, 72c, 72d with respect to the exhaust gas discharged from the mixing passages 94a, 94b, 94c, 94d and having different concentrations of nitrogen oxides. Inject the reducing agent. Specifically, the minimum amount of the reducing agent is injected from the nozzle 73a of the reducing agent supply pipe 72a to the exhaust gas discharged from the mixing passage 94a and having a low concentration of nitrogen oxides. On the other hand, the maximum amount of the reducing agent is injected from the nozzle 73d of the reducing agent supply pipe 72d to the exhaust gas discharged from the mixing passage 70d and having a high concentration of nitrogen oxides.

When the reducing agent is supplied to the exhaust gas from the reducing agent supply device 65, the exhaust gas flows into the selective reduction catalyst 61 in a state where the reducing agent is mixed. The selective reduction catalyst 61 promotes the reaction between the nitrogen oxides in the exhaust gas and the reducing agent, reduces the nitrogen oxides, and removes and reduces the nitrogen oxides in the exhaust gas. At this time, since the reducing agent in an amount corresponding to the content of the nitrogen oxide is supplied to the exhaust gas having different concentrations and then flows into the selective reduction type catalyst 61, the nitrogen oxide is efficiently produced by the selective reduction type catalyst 61. It is often reduced and removed.

[Action and effect of this embodiment]
The denitration device according to the first aspect is provided with a selective reduction catalyst 61 provided in the flue (gas passage) 41 and an upstream side of the selective reduction catalyst 61 in the flue 41 in the gas flow direction. Is selected as a partition plate 62, 63, 64, 91, 92, 93 that divides the gas into a plurality of mixing passages (regions) 70a, 70b, 70c, 70d, 94a, 94b, 94c, 94d in the direction orthogonal to the gas flow direction. An amount of reducing agent provided on the upstream side in the gas flow direction from the reduction catalyst 61 according to the nitrogen oxide concentration of the gas flowing through the plurality of mixing passages 70a, 70b, 70c, 70d, 94a, 94b, 94c, 94d. A reducing agent supply device 65 for supplying is provided.

In the denitration device according to the first aspect, the exhaust gas flowing through the flue 41 is a plurality of mixed passages 70a, 70b, 70c, 70d, 94a, 94b partitioned by partition plates 62, 63, 64, 91, 92, 93. , 94c, 94d, and then the reducing agent supply device 65 supplies an amount of the reducing agent according to the nitrogen oxide concentration of the gas flowing through the mixing passages 70a, 70b, 70c, 70d, 94a, 94b, 94c, 94d. NS. Therefore, a large amount of reducing agent is supplied to the exhaust gas having a high nitrogen oxide concentration, and a small amount of the reducing agent is supplied to the exhaust gas having a low nitrogen oxide concentration. No. 61 can efficiently reduce and remove nitrogen oxides in the exhaust gas, and can improve the performance. That is, since an appropriate amount of the reducing agent corresponding to the nitrogen oxide concentration is supplied to the exhaust gas, it is suppressed that the reducing agent remaining after the nitrogen oxide is reduced reacts with the sulfur oxide to generate ammonium sulfate. Therefore, the work of removing ammonium sulfate is not required, and an increase in maintenance cost can be suppressed.

In the denitration device according to the second aspect, the partition plate has first partition plates 62, 63, 64 that partition the flue 41 into a plurality of mixing passages 70a, 70b, 70c, 70d in the width direction. As a result, the exhaust gas having a concentration difference in nitrogen oxides in the width direction can be made uniform in concentration to nitrogen oxides in each of the mixing passages 70a, 70b, 70c, and 70d.

In the denitration device according to the third aspect, the length of the plurality of mixing passages 70a, 70b, 70c, 70d, 94a, 94b, 94c, 94d in the gas flow direction is longer than the length in the direction orthogonal to the gas flow direction. As a result, the mixing passages 70a and 70b can sufficiently secure a sufficient length of the flow path width or the flow path length with respect to the flow path area in order to uniformly mix the exhaust gas having a concentration difference in the nitrogen oxides. , 70c, 70d, 94a, 94b, 94c, 94d can be secured.

In the denitration device according to the fourth aspect, the mixing promotion device 81 is provided in the gas inflow section in the plurality of mixing passages 70a, 70b, 70c, 70d, 94a, 94b, 94c, 94d. As a result, the mixing accelerator 81 mixes the exhaust gas that has flowed into the mixing passages 70a, 70b, 70c, 70d, 94a, 94b, 94c, 94d, thereby mixing the mixing passages 70a, 70b, 70c, 70d, 94a, 94b, 94c. , 94d can be promoted to mix the exhaust gas, and the concentration of nitrogen oxides can be appropriately made uniform.

The denitration device according to the fifth aspect has the mixing passages 70a, 70b, 70c, 70d, 94a, 94b, 94c, in the direction in which the plurality of mixing passages 70a, 70b, 70c, 70d, 94a, 94b, 94c, 94d are adjacent to each other. The length of 94d is set according to the concentration distribution of nitrogen oxides in the flowing exhaust gas. Thereby, mixing passages 70a, 70b, 70c, 70d, 94a, 94b, 94c, 94d having a sufficient length can be provided according to the concentration distribution of nitrogen oxides in the exhaust gas, and a plurality of mixing passages 70a, 70b, Exhaust gas flowing through 70c, 70d, 94a, 94b, 94c, 94d can be appropriately mixed.

In the denitration device according to the sixth aspect, the partition plate has second partition plates 91, 92, 93 that partition the flue 41 into a plurality of mixing passages 94a, 94b, 94c, 94d in the depth direction. As a result, the exhaust gas having a concentration difference in nitrogen oxides in the depth direction can be made uniform in concentration to nitrogen oxides in each of the mixing passages 70a, 70b, 70c, and 70d.

In the denitration device according to the seventh aspect, the flue 41 has a third horizontal flue portion (horizontal passage) 41e and a third vertical flue portion (vertical passage) 41f, and the selective reduction catalyst 61 is a selective reduction catalyst 61. The third vertical flue section (vertical passage) 41f is provided, and the partition plates 62, 63, 64, 91, 92, 93 are provided at least in the third vertical flue section (vertical passage) 41f. As a result, the nitrogen oxide concentration in the exhaust gas flowing through the plurality of mixing passages 70a, 70b, 70c, 70d, 94a, 94b, 94c, 94d can be made uniform, and the partition plates 62, 63, 64, 91, It is possible to simplify 92 and 93.

In the denitration device according to the eighth aspect, the partition plates 62, 63, 64, 91, 92, 93 are provided so as to straddle the third horizontal flue portion 41e and the third vertical flue portion 41f. As a result, it is possible to secure a long flow path length of the plurality of mixing passages 70a, 70b, 70c, 70d, 94a, 94b, 94c, 94d, and the plurality of mixing passages 70a, 70b, 70c, 70d, 94a, 94b. , 94c, 94d can promote the mixing of exhaust gas.

The boiler according to the ninth aspect includes a furnace 11 installed along the vertical direction, a combustion device 12 arranged in the furnace 11, and a flue 41 arranged on the downstream side in the flow direction of combustion gas in the furnace 11. And the boilers 51, 52, 53 as heat exchangers arranged in the flue 41, the reheaters 54, 55, the economizer 56, and the denitration arranged downstream from the heat exchanger in the flue 41. It includes devices 43, 43A, 43B. As a result, the denitration devices 43, 43A, and 43B supply an appropriate amount of reducing agent to the exhaust gas according to the nitrogen oxide concentration, and the selective reduction catalyst 61 efficiently reduces and removes the nitrogen oxides in the exhaust gas. It is possible to improve the performance. Then, the reducing agent remaining after the reduction of the nitrogen oxide is suppressed from reacting with the sulfur oxide to generate ammonium sulfate, the work of removing the ammonium sulfate is not required, and the increase in maintenance cost can be suppressed. , It is possible to suppress a decrease in the operating efficiency of the coal-fired boiler 10.

In the above-described embodiment, between the partition plates 62, 63, 64, 91, 92, 93 (mixing passages 70a, 70b, 70c, 70d, 94a, 94b, 94c, 94d) and the selective reduction catalyst 61. Although the reducing agent supply device 65 is provided, the present invention is not limited to this configuration. For example, the downstream end in the gas flow direction in the mixing passages 70a, 70b, 70c, 70d, 94a, 94b, 94c, 94d (the downstream end in the gas flow direction in the partition plates 62, 63, 64, 91, 92, 93). A reducing agent supply device 65 may be provided at a position (position sandwiched between the portions). Further, the downstream end in the gas flow direction in the partition plates 62, 63, 64, 91, 92, 93 (mixing passages 70a, 70b, 70c, 70d, 94a, 94b, 94c, 94d) is selected as the reducing catalyst 61. A reducing agent supply device 65 may be provided at the downstream end in the gas flow direction in the mixing passages 70a, 70b, 70c, 70d, 94a, 94b, 94c, 94d so as to extend to the inflow portion.

Further, in the above-described embodiment, the number of partition plates 62, 63, 64, 91, 92, 93 and the mixing passages 70a, 70b, 70c, 70d, 94a, 94b, 94c, 94d is limited to the embodiment. It is not a thing, but may be appropriately set according to the shape and size of the furnace 11 and the flue 41.

Further, in the first embodiment described above, the mixing passages 70a, 70b, 70c, 70d are provided by the first partition plates 62, 63, 64, and in the third embodiment, the mixing passages are provided by the second partition plates 91, 92, 93. Although 94a, 94b, 94c, 94d are provided, a grid-like mixing passage may be provided by the first partition plates 62, 63, 64 and the second partition plates 91, 92, 93. Further, the lengths of the first partition plates 62, 63, 64 and the second partition plates 91, 92, 93 may be different from each other, and the number of sheets is not one but divided into a plurality of sheets. May be configured.

10 Coal-fired boiler (boiler)
11 Furnace 12 Combustion device 13 Combustion gas passage 21, 22, 23, 24, 25 Combustion burner 41 Flue (gas passage)
41a 1st horizontal flue section 41b 1st vertical flue section 41c 2nd horizontal flue section 41d 2nd vertical flue section 41e 3rd horizontal flue section (horizontal passage)
41f 3rd vertical flue (vertical passage)
42 Air heater 43, 43A, 43B Denitration device 44 Gas duct 51, 52, 53 Superheater 54, 55 Reheater 56 Economizer 61 Selective reduction catalyst (denitration catalyst)
62, 63, 64 1st partition plate (partition plate)
65 Reducing agent supply device 66 Control device 70a, 70b, 70c, 70d Mixing passage (region)
71 Reducing agent supply pump 72a, 72b, 72c, 72d Reducing agent supply pipe 73a, 73b, 73c, 73d Nozzle 81 Mixing accelerator 81a, 81b, 81c, 81d Mixing accelerator 91, 92, 93 Second partition plate (partition plate) )
94a, 94b, 94c, 94d mixed passage (region)

Claims (9)

1. Selective reduction catalyst provided in the gas passage and
   A partition plate provided on the upstream side of the selective reduction catalyst in the gas passage in the gas flow direction and partitioning the gas passage into a plurality of regions in the direction orthogonal to the gas flow direction.
   A reducing agent supply device provided on the upstream side in the gas flow direction from the selective reduction catalyst and supplying a reducing agent in an amount corresponding to the nitrogen oxide concentration of the gas flowing through the plurality of regions.
   Denitration device equipped with.
2. The partition plate has a first partition plate that partitions the gas passage into a plurality of regions in the width direction.
   The denitration device according to claim 1.
3. In the plurality of regions, the length in the gas flow direction is longer than the length in the direction orthogonal to the gas flow direction.
   The denitration device according to claim 1 or 2.
4. Mixing promotion devices are provided in the gas inflow portions in the plurality of regions.
   The denitration device according to any one of claims 1 to 3.
5. The length of the region in the direction in which the plurality of regions are adjacent to each other is set according to the concentration distribution of nitrogen oxides in the flowing gas.
   The denitration device according to any one of claims 1 to 4.
6. The partition plate has a second partition plate that partitions the gas passage into a plurality of regions in the depth direction.
   The denitration device according to any one of claims 1 to 5.
7. The gas passage has a horizontal passage and a vertical passage continuous to the downstream side in the gas flow direction in the horizontal passage, the selective reduction catalyst is provided in the vertical passage, and the partition plate is at least said. Provided in the vertical passage,
   The denitration device according to any one of claims 1 to 6.
8. The partition plate is provided so as to straddle the horizontal passage and the vertical passage.
   The denitration device according to claim 7.
9. A furnace installed along the vertical direction,
   The combustion device placed in the furnace and
   The flue arranged on the downstream side in the flow direction of the combustion gas in the furnace, and
   The heat exchanger placed in the flue and
   The denitration device according to any one of claims 1 to 8, which is arranged on the downstream side of the heat exchanger in the flue.
   Boiler with.

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