JP6542568B2 - Fluid mixing device and denitration device provided with fluid mixing device - Google Patents

Description

  The present invention relates to a fluid mixing device for mixing an exhaust gas generated from a combustion device such as a boiler installed in a thermal power plant or a plant with a different fluid such as a reducing agent, and to a NOx removal device provided with the fluid mixing device. .

  The exhaust gases generated from combustion devices such as boilers installed in thermal power plants and factories contain harmful nitrogen oxides (NOx). A selective catalytic reduction method is generally used as a method of removing NOx. This method sprays a reducing agent (such as ammonia) on the exhaust gas and then passes it through a NOx removal catalyst, thereby causing harmless nitrogen with the following reaction: It is converted to water.

4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O (1)
NO + NO ₂ + 2 NH ₃ → 2 N ₂ + 3 H ₂ O (2)
In order to increase the denitration rate, it is necessary to inject NH ₃ into the exhaust gas without excess or deficiency. Therefore, by providing the exhaust gas mixing unit in the exhaust gas flow path between the reducing agent spray unit that sprays the reducing agent on the exhaust gas and the NOx removal catalyst installation unit, the reducing agent is uniformly mixed in the exhaust gas to remove NOx by the NOx removal catalyst. Technology has been disclosed.

  Patent Document 1 below discloses a configuration in which an exhaust gas mixer in which a jet is provided on a quadrangular pyramid-shaped introduction flow path forming member is installed in an exhaust gas duct and mixing is promoted by colliding jets from the jet. It is done.

  Further, in Patent Document 2 below, the exhaust gas passing through the opening of the mixing plate on the upstream side is downstream by the exhaust gas mixer in which a plurality of mixing plates having openings are provided so that the openings do not overlap in the exhaust gas flow direction. A configuration is disclosed that promotes mixing by passing through the non-opening portion of the mixing plate when passing through the mixing plate.

  Furthermore, according to the configuration described in Patent Document 3 below, a trapezoidal shape is formed in the exhaust gas flow channel, and is formed into a gap forming portion of a rectangular flat plate provided at the top on the exhaust gas upstream side and a trapezoidal shape connected to opposing sides of the gap forming portion. A plurality of mixing cells forming a truncated pyramid shape are provided by two plate-like wings and a trapezoidal opening adjacent to the plate-like wings, and the mixing cell is rotated 90 ° of the plate-like wings and the opening. By forming the mixing element adjacently connected to each other in a stationary state, a vortex is formed to promote mixing.

  Then, according to Patent Document 4 below, the gas injection unit can be disposed in a narrow space by dividing the ammonia injection nozzle into a plurality so as to correspond to each of the plurality of divided gas mixers, and mixing in a short distance Possible configurations are disclosed.

  Further, Patent Document 5 below discloses a configuration in which a homogeneous mixed gas can be easily obtained by providing an ammonia injection nozzle inside a square pyramidal mixing device.

Patent No. 3296069 Japanese Utility Model Application Publication No. 4-65118 JP, 2013-180227, A Patent No. 3554997 gazette Patent No. 4335504

  In order to increase the denitration rate by the denitration catalyst, it is necessary to uniformly mix the reducing agent in the exhaust gas. That is, if the concentration of the reducing agent is made uneven and dispersed, mixing of the exhaust gas and the reducing agent can be promoted. The degree of deviation of the reducing agent concentration is represented by a coefficient of variation, and it is judged that the smaller the coefficient of variation, the smaller the variation, that is, the more dispersed. The calculation of the variation coefficient is performed based on the measurement result of the reducing agent concentration in the virtual division plane obtained by dividing the duct cross section by a predetermined amount.

The definition of the variation coefficient is the following equations (3) and (4).

In the following, the number of measurement points n represents the number of virtual division planes (measurement points), the measurement value x is a measurement value of each virtual division plane, and x _i is an average value.
In the configurations described in Patent Documents 1 to 5, all use mixers provided with openings, but if the opening ratio of the openings is increased, mixing of the reducing agent and the exhaust gas is not promoted, and the variation coefficient rises Invite you. On the other hand, although the coefficient of variation decreases when the opening ratio of the openings is lowered, the number of non-openings causes an increase in the pressure loss of the exhaust gas. In addition, when the pressure loss increases, the power of the fan increases and the exhaust gas treatment facility is also loaded.

  In the configurations described in Patent Document 4 and Patent Document 5, a plurality of exhaust gas mixers are disposed on the same cross section of the duct, and the plurality of exhaust gas mixers promote mixing at that location, but on the downstream side Since the exhaust gases are not mixed, it is not possible to expect an increase in the mixing ratio. On the other hand, in the case of an exhaust gas mixer provided with a plurality of openings such that the openings do not overlap in the exhaust gas flow direction as shown in FIG. 3 of Patent Document 1 and FIG. 5 of Patent Document 2, the reducing agent and the exhaust gas Although the mixing with is promoted, it causes an increase in pressure loss.

  In addition, in the gas mixing device described in Patent Document 3, the vortex flow is formed leaving only the plate-like blade portion contributing to the formation of the large swirling flow, and the pressure loss is reduced by increasing the flow passage cross-sectional area. . In the case of mixing of two fluids, mixing is possible only by going straight due to flow disturbance, but it is necessary to secure mixing time, that is, residence time. Therefore, in the case where the mixing element forms a vortex in a narrow space and mixes them, since the residence time is not secured, the effect of promoting mixing can not be expected much either.

  It is an object of the present invention to provide a fluid mixing device and a fluid mixing device capable of uniformly mixing exhaust gas and reducing agent by reducing the variation coefficient of reducing agent concentration in exhaust gas without increasing the pressure loss of exhaust gas. Providing a denitrification apparatus having the

The problems of the present invention can be solved by adopting the following configuration. ADVANTAGE OF THE INVENTION According to this invention, coexistence of acceleration | stimulation of mixing of waste gas and a reducing agent, and increase suppression of the pressure loss of a fluid is attained.
The invention according to claim 1 is a fluid mixing apparatus for mixing an exhaust gas discharged from a combustion apparatus including a boiler with a nitrogen oxide reducing agent injected into the flow path of the exhaust gas. The apparatus comprises a swirling portion of the fluid and a mixing portion of the fluid provided on the downstream side of the exhaust gas flow further than the swirling portion, and the swirling portion has a flat portion in a direction substantially orthogonal to the exhaust gas flow direction. A plate-like member, a plurality of outer peripheral openings formed along the outer periphery of the plate-like member, and an exhaust gas flow downstream side of each outer peripheral opening are brought into contact, and the fluid passing through the outer peripheral opening is guided in the circumferential direction The mixing unit is a mixing device for fluid which is a cone-shaped member without a bottom and having a top on the upstream side of the exhaust gas flow and a plurality of side openings on the side.

In the invention according to claim 2, the plate-like member of the turning portion has a central opening formed closer to the center than the outer peripheral opening, and the pyramid member of the mixing portion has an exhaust gas at its apex. The fluid mixing device according to claim 1, wherein the fluid mixing device is disposed so as to overlap with the central opening when viewed in the flow direction.
The invention according to claim 3 is the fluid mixing device according to claim 1 or 2, wherein each guide member of the turning portion is a tubular member.

  The invention according to claim 4 relates to a reducing agent injection unit for injecting a reducing agent of nitrogen oxide into a duct of exhaust gas discharged from a combustion apparatus including a boiler, and a fluid mixing apparatus for mixing exhaust gas and reducing agent And a denitration unit provided with a denitration catalyst for removing nitrogen oxides in the exhaust gas, which are disposed sequentially from the upstream side to the downstream side of the exhaust gas flow, wherein the mixing device for the fluid includes the first to third aspects. It is the denitrification apparatus which is a mixing apparatus of the fluid of any one of these.

(Action)
As described above, although the mixer having the opening is used in the gas mixer of the prior art, increasing the opening ratio of the opening causes an increase in the coefficient of variation, while reducing the opening ratio of the opening reduces the exhaust gas The problem is that it causes an increase in pressure loss.

  The mixing device of the present invention is configured in a two-stage configuration of the upstream fluid swirling portion and the downstream fluid mixing portion. The upstream swirling portion is a plate-like member having a flat portion in a direction substantially orthogonal to the exhaust gas flow direction, and is in contact with a plurality of outer peripheral openings provided along the outer periphery and the downstream side of each outer peripheral opening And a guide member for guiding the fluid circumferentially. Moreover, a mixing part is a pyramid member which has an apex on the exhaust gas upstream side, and has a plurality of side openings on the side.

  First, in the swirling portion on the upstream side, the fluid flowing into the outer peripheral opening on the inner wall side of the duct is given a circumferential flow by the guide member to be a swirling flow, and the flow velocity is maintained at a relatively high speed. Therefore, it flows into the side opening of the mixing section while turning while maintaining the flow velocity, and flows so as to bend in the central axial direction of the duct. According to the present invention, pressure loss can be suppressed to a low level without generating complicated and excessive vortices and wakes.

And by the structure of 2 steps of a turning part and a mixing part, the retention time of fluid is secured, and it can prevent mixing and increase of pressure loss.
Therefore, according to the first aspect of the present invention, the fluid is given a relatively high-speed circumferential flow on the inner wall side of the duct by the upstream swirling portion, and the duct in the downstream mixing portion while maintaining the flow velocity By flowing in the direction of the central axis, a decrease in the coefficient of variation is achieved while suppressing an increase in pressure loss.

  In addition, although there is an outer peripheral opening in the plate-like member of the turning portion, it is preferable that the opening ratio is high from the viewpoint of preventing an increase in pressure loss. However, if the outer peripheral opening is enlarged, the momentum of the swirling flow is weakened. Therefore, according to the second aspect of the invention, in addition to the function of the invention of the first aspect, by providing the central opening in the plate-like member of the turning portion, it is possible to further suppress an increase in pressure loss. . Here, when the aperture ratio is increased, the coefficient of variation rises, but the fluid passing through the central opening flows from the apex of the pyramid of the mixing section along the slope of the side and flows from the side opening toward the central axis of the duct. That is, after flowing from the central axis direction of the duct to the inner wall side (outside), it flows again to the central axis side, and the flow direction changes.

  Further, the fluid passing through the outer peripheral opening portion flows from the inner wall side of the duct into the side opening portion of the mixing portion while turning and flows to the central axis side. Then, in the mixing section, the fluid whose swirl is given at the outer peripheral opening and the fluid flowing in a linear direction (horizontal direction) from the inner central opening merge and are mixed when passing through the side opening Ru. Therefore, mixing can be promoted while further suppressing the increase in pressure loss, and the coefficient of variation also decreases.

  Then, according to the invention of claim 3, in addition to the function of the invention of claim 1 or claim 2, since the guide member of the turning portion is a cylindrical member, the fluid flows in the cylinder It is possible to give impetus to the flow and hold high-speed swirling flow.

  Further, according to the invention of claim 4, the mixing apparatus for fluid according to any one of claims 1 to 3 is provided between the reducing agent injection part and the denitrification part of the exhaust gas duct of the denitrification apparatus. By arranging, the fluid in which the exhaust gas and the reducing agent are uniformly mixed react with the NOx removal catalyst. Therefore, the reaction efficiency between the NOx removal catalyst and the fluid is improved, and a high NOx removal rate can be maintained.

  According to the first aspect of the present invention, the residence time of the fluid of the exhaust gas and the reducing agent is also secured by the mixing device including the upstream swirling portion and the downstream mixing portion, and the fluid to which the swirling flow is given. Can be promoted while suppressing the increase in pressure loss, and the coefficient of variation can also be reduced. Therefore, the power of the fan in the exhaust gas treatment facility is not increased.

  According to the invention of claim 2, in addition to the effect of the invention of claim 1, an increase in pressure loss can be further suppressed by the central opening provided in the plate-like member of the turning portion. In addition, the fluid passing through the central opening changes its flow direction outward from the central axis of the duct to the central axis again, and the outer swirl flow and the inner linear flow in the swirl portion merge to form a mixing portion Because mixing occurs when passing through the side opening, mixing is promoted and an increase in the coefficient of variation can also be prevented.

  And according to the invention of claim 3, in addition to the effect of the invention according to claim 1 or claim 2, since it is possible to hold the swirling flow at high speed by the cylindrical guide member, the pressure loss is increased. While suppressing, mixing in the mixing section is further promoted.

According to the invention of claim 4, the reaction efficiency between the NOx removal catalyst and the fluid is improved, and a NOx removal device capable of maintaining a high NOx removal rate can be provided.
And, by improving the mixing property of the exhaust gas and the reducing agent by the practice of the present invention, the amount of reducing agent used can be saved, and by reducing the unreacted reducing agent, it is possible to reduce the offensive odor derived from the reducing agent. Contribute to the improvement of plant operation.

It is a schematic block diagram (side view) of the NOx removal apparatus which is one Example of this invention. It is a front view of the mixer of FIG. It is a front view of the mixing part of the mixer of FIG. It is a perspective view at the time of arranging two mixers side by side. It is the figure which showed the measurement result (flow analysis) of the flow velocity of the fluid at the time of using the mixer of FIG. It is a figure at the time of seeing the turning part of the mixer of FIG. 4 from the exhaust gas flow direction. FIG. 7 (A) is a plan view of the mixing section of the mixer of FIG. 4 and FIG. 7 (B) is a side view. It is a perspective view of a mixer at the time of providing only a central opening in a plate-like member of a revolving part. Fig. 9 (A) is a front view showing another example of the turning portion, and Fig. 9 (B) is an enlarged view of the guide member of Fig. 9 (A). It is a schematic block diagram (side view) of the NOx removal apparatus which is another Example of this invention. It is a schematic block diagram (side view) of the NOx removal apparatus which is another Example of this invention.

  Hereinafter, embodiments of the present invention will be described.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, the schematic block diagram of the denitrification apparatus which is one Example of this invention is shown. Also, FIG. 2 shows a front view of the mixer comprising the swirling part and the mixing part when viewed from the exhaust gas flow direction (the nozzle 5 side), and FIG. 3 shows the mixer from the exhaust gas flow direction The figure of the mixing part of is shown.

  The denitration apparatus 1 of this embodiment has a configuration in which a reducing agent injection nozzle 5 for injecting ammonia as a reducing agent into the exhaust gas duct 3 and a denitration catalyst layer 7 composed of a denitration catalyst are provided along the exhaust gas flow. Further, a mixer 9 for promoting the mixing of the exhaust gas and the ammonia is provided between the reducing agent injection nozzle 5 and the NOx removal catalyst layer 7.

  The exhaust gas discharged from a boiler (not shown) (which may be a combustion reaction device such as a kiln) is introduced horizontally (in the direction of arrow A) and flows with the ammonia sprayed from the reducing agent injection nozzle 5 in the exhaust gas duct 3 After being mixed by the reactor 9, it flows into the NOx removal catalyst layer 7. The amount of ammonia sprayed is adjusted by the adjusting valve 6 a of the injection pipe 6 according to the amount of exhaust gas. Urea may be used as the reducing agent.

  The mixer 9 of this embodiment is characterized in that it has a two-stage configuration of the upstream swirling portion 11 and the downstream mixing portion 13. The upstream swirling portion 11 has a plate-like member 11a having a flat portion in a direction substantially orthogonal to the exhaust gas flow direction, a plurality of small diameter outer peripheral openings 11b formed along the outer periphery of the plate-like member 11a, and a plate A large diameter central opening 11c formed at the center of the annular member 11a and guide members 11d for guiding the fluid in the circumferential direction in contact with the exhaust gas flow downstream side of each outer peripheral opening 11b.

  The guide member 11 d is cylindrical, and as shown in FIG. 2, the guide member 11 d is disposed circumferentially such that fluid flows clockwise (clockwise) from the tip as viewed from the exhaust gas flow direction. Although the cylindrical shape is shown in the illustrated example, the cross section may be a polygonal shape such as a square shape. In FIG. 2, the outer peripheral opening 11 b and the guide member 11 d are arranged to be laterally offset, but may be arranged at equal intervals in the circumferential direction. Further, the numbers of the outer peripheral openings 11b and the guide members 11d are not limited, and it is preferable to install according to the size and the shape of the exhaust gas duct 3, but a multiple of about 4 is suitable.

  And mixing part 13 is quadrangular pyramid without a bottom which has point 13c in the exhaust gas upper stream side, and has a plurality of side openings 13b in side 13a. In addition, even if it is not a quadrangular pyramid, a cone, a triangular pyramid, etc. may be sufficient, and it is good to match with the shape of the exhaust gas duct 3. The same applies to the plate-like member 11 a of the turning portion 11. That is, the shape of the plate-like member 11a may be square or circular, and is not particularly limited.

The apex 13 c of the quadrangular pyramid of the mixing unit 13 is disposed so as to overlap with the central opening 11 c of the swirling unit 11 when viewed from the exhaust gas flow direction.
The fluid consisting of ammonia and the exhaust gas first flows into the swirling portion 11 on the upstream side. In the turning portion 11, a flow of fluid flowing in the horizontal direction from the central opening 11c and a turning flow in which turning is given by the guide member 11d from the outer peripheral opening 11b are formed.

  The fluid flowing through the central opening 11c goes straight and maintains a relatively high speed, and the central opening 11c has a relatively large diameter to increase the aperture ratio, thereby suppressing an increase in pressure loss. On the other hand, the fluid flowing through the outer peripheral opening 11b is supplied with a flow in the circumferential direction from the outer peripheral opening 11b having a relatively small diameter by the guide member 11d, whereby the flow velocity is maintained at a relatively high speed. In particular, when the guide member 11d is shaped like a nozzle whose diameter decreases toward the tip, high-speed flow is obtained.

  Then, in the mixing part 13 on the downstream side, the fluid that has passed through the swirling part 11 flows in the central axis direction of the exhaust gas duct 3 from the side opening 13 b. The fluid that has passed through the central opening 11c of the turning portion 11 flows along the slope of the side surface 13a from the pyramid apex 13c and flows into the side opening 13b. On the other hand, the fluid that has passed through the outer peripheral opening 11b of the turning portion 11 forms a turning flow, and flows into the side opening 13b while turning.

  Therefore, the horizontal flow from the central opening 11 c of the rotating portion 11 and the swirling flow from the outer peripheral opening 11 b flow into the side opening 13 b of the mixing portion 13 and flow in the central axial direction of the exhaust gas duct 3 The mixing efficiency is also reduced and the coefficient of variation is also reduced.

  In general, if the flow direction changes and the streamline extends long, mixing proceeds in the meantime. However, if the flow direction is sharply bent like a hairpin or maze, the pressure drop will rise. On the other hand, according to the configuration of the present embodiment, the pressure loss does not increase because the rapid change in the flow direction and the generation of the excess vortex accompanying it can be suppressed.

Further, since the fluid passes through the swirling portion 11 on the upstream side and the mixing portion 13 on the downstream side, the residence time of the fluid can be secured, and mixing can be promoted and an increase in pressure loss can be prevented.
Although the central opening 11c is provided in the plate-like member 11a in the illustrated example, the central opening 11c is not necessarily required, and even if the central opening 11c is not provided, the swirling flow by the outer peripheral opening 11b and the guide member 11d By flowing in the central axis direction of the mixing unit 13 while maintaining a relatively high speed, the variation coefficient can be reduced while suppressing an increase in pressure loss. When the central opening 11c is not provided, the outer peripheral opening 11b may be provided relatively on the central axis side.

  Here, if the outer peripheral opening 11b is reduced, high-speed flow can be maintained, but the pressure loss tends to increase. On the other hand, when the outer peripheral opening 11b is enlarged, the increase in pressure loss is suppressed but the momentum of the swirling flow is weakened. Therefore, by further providing the central opening 11c in the plate member 11a, mixing of the fluid can be promoted while preventing an increase in pressure loss.

  In the above-mentioned example, although one mixer 9 was installed in exhaust gas duct 3, if a plurality of mixers 9 are arranged in exhaust gas duct 3, the mixing promotion effect will become high. In particular, when the exhaust gas duct 3 is large in a large NOx removal apparatus, or when the cross-sectional shape is rectangular and the difference in the ratio between the short side and the long side is large, it is preferable to install a plurality.

  FIG. 4 shows a perspective view (inside of the duct 3) in the case where two mixers 9 are arranged side by side in the exhaust gas duct 3, and FIGS. 5 (A) and 5 (B) show the mixer of FIG. The flow analysis result of the fluid at the time of using 9 is shown. 6 shows a view of the swirling portion 11 of the mixer 9 of FIG. 4 viewed from the exhaust gas flow direction, and FIG. 7A shows a plane of the mixing portion 13 of the mixer 9 of FIG. A figure is shown and a side view is shown to FIG. 7 (B).

  Two mixers 9 were installed horizontally in the exhaust gas duct 3 having a rectangular cross section of 800 mm × 2100 mm so as to be in contact with the inner wall of the duct. Each mixer 9 is a plate-like member in which a central opening 11c having a diameter of about 500 (mm) and an elliptical outer peripheral opening 11b having a diameter of about 200 × 100 (mm) are arranged laterally (in the lateral direction). A rotating portion 11 in which a cylindrical guide member 11d having a length of 300 (mm) is attached to the downstream side of each outer peripheral opening 11b in 11a and a circular side opening 13b having a diameter of about 350 (mm) A mixing portion 13 of a quadrangular pyramid having a side surface 13 a, a height of 700 (mm) and a generatrix length of 800 (mm), and the mixing portion 13 has an apex 13 c of the central opening 11 c of the turning portion 11 Arranged to coincide with the center. By aligning the apex 13c with the center of the central opening 11c, it is possible to suppress an extreme flow direction sudden change and the generation of an excess vortex accompanying it, so it is possible to avoid an increase in pressure loss while promoting mixing. Become.

  In the flow analysis, the analysis was performed under the condition that the variation coefficient of the reducing agent concentration at the inlet of the mixer 9 has a bias of 20. The coefficient of variation in flow analysis can be set by setting the long side, short side, or diagonal of the duct cross section, but the coefficient of variation of 20 is set to the diagonal of the duct cross section where mixing of the reducing agent is most difficult did.

  In addition, this analysis was modeled by general-purpose fluid analysis software (Ansys Fluent) (manufactured by Ansis Japan Co., Ltd.), and carried out by steady-state analysis by a finite volume method. The conditions were the same as in the analysis of variation coefficient (Table 1) described later.

  In FIG. 5, the flow velocity is generally 0.0 m / s to 9.6 m / s blue, the flow velocity 9.6 m / s to 16.5 m / s green, and the flow velocity 16.5 m / s to 19.2 m / s yellow. A flow rate of 19.2 m / s to 24.7 m / s is shown in amber, and a flow rate of 24.7 m / s to 27.5 m / s is shown stepwise in red.

  According to FIG. 5, the flow velocity of the fluid between the swirling portion 11 and the mixing portion 13 is maintained at a relatively high speed of 16.5 m / s or more, and in particular, the fluid passing through the cylindrical guide member 11 d There are many places of .7 m / s or more. And, the flow velocity at the outlet of the mixer 9 is also higher at 9.6 m / s or more, mainly at 16.5 m / s to 19.2 m / s, compared to the inlet (which is approximately 9.6 m / s or less). Know that

Therefore, it is assumed that the pressure loss of the exhaust gas is low. In addition, it can be confirmed that there is no sudden change in the flow direction in the streamline and no occurrence of excessive vortices.
Then, the fluid is diffused in the lateral and vertical directions from the cylindrical guide member 11 d and then flows in the central axial direction of the exhaust gas duct 3 together with the fluid flowing in from the central opening 11 c, thereby promoting the mixing.

Table 1 shows the results of examining the coefficient of variation at the outlet of the mixer 9 using the mixer 9 shown in FIG.

  8 shows the mixer 10 provided with the swirling portion 14 and the mixing portion 13 in which only the central opening 14b is provided in the plate-like member 14a used as a comparison, and the dimensions and shape are shown in FIG. It is similar to the mixer 9 described above. In addition, analysis was modeled by general-purpose fluid analysis software (Ansys Fluent) (manufactured by Ansis Japan Co., Ltd.), and carried out by steady analysis by the finite volume method. Then, the variation coefficient of the reducing agent concentration was set to be 20% in the diagonal direction at the inlet of the mixer 9, and the variation coefficient of the reducing agent concentration at the outlet of the mixer 9 was calculated. The calculation of the coefficient of variation is based on the equations (3) and (4).

In the case of a duct of this size, in the case of hand analysis, the duct is divided into six, and the actual calculation is performed based on the measurement results of the center of each divided surface (six measured values can be obtained). On the other hand, since there is no restriction of hand analysis in analysis, ducts of the same size were divided into several thousand and calculated. In the analysis, since the cross section is divided into several thousand, it is an equation representing the concentration gradient of NH ₃ with the concentration (Y and Z (FIG. 5) as a variable) as one of the initial conditions of each mesh thereof The unit is given by mass fraction). For the entrance condition, the coefficient of the above equation was determined based on the equation of variation coefficient, and the equation was given to the analysis software. The outlet results were calculated from the values of the outlet cross section (calculation results of analysis software) using the equation of the coefficient of variation.

Further, as a condition, a mixed gas _{(N 2} is 75.54vol%, _{O 2} is 13.04vol%, _{H 2} O is 8.22vol%, CO ₂ is 3.20Vol%, those containing wet) and diluted NH ₃ A gas (volume fraction 0.03%) was set, and analysis was performed at a physical property value of 350 ° C.

The density of the mixed gas is 0.552 kg / m ³ and the viscosity coefficient is 3.0325 × 10 ⁻⁵ kg / m · s, while the density of diluted NH ₃ gas is 0.329 kg / m ³ and the viscosity coefficient is 2. It was 161 × 10 ⁻⁵ kg / m · s. The mass diffusion coefficient of the diluted NH ₃ gas was 8.5 × 10 ⁻⁵ m ² / s. The total amount of gas flowing into the model was 13354 m ³ N / h, and the turbulence intensity was assumed to be 10% assuming a standard turbulence.

  As shown in Table 1, in the case of the mixer 10 of the comparative example, although the coefficient of variation was a relatively high value of 10%, in the mixer 9 of the present embodiment, the value of a relatively low value of 5.8%. The Therefore, it was confirmed that the mixing ratio is increased by the turning effect of the cylindrical guide member 11d. If the variation coefficient is about 5%, it can be said that the reducing agent is sufficiently dispersed, and a high denitrification rate can be maintained.

In particular, when the coefficient of variation is about 5%, it has been confirmed from the results that the NOx removal efficiency can be increased to 95% or more by installing multiple NOx removal equipment such as the NOx removal catalyst layer 7 and the like.
In FIG. 1, although only one deNOx catalyst layer 7 is provided, denitration can be performed with high efficiency if the variation coefficient is low.

  For example, several tens of reducing agent injection nozzles 5 are installed in a grid, and the adjustment valve 6a of each injection pipe 6 is also installed for each nozzle. Then, the opening degree of the adjustment valve 6 a of the injection pipe 6 is finely adjusted, and the reducing agent is uniformly dispersed and adjusted to flow to the NOx removal catalyst layer 7. As described above, by using the exhaust gas mixer 9 together with the adjustment of the opening degree of the adjustment valve 6a, it is possible to realize further higher efficiency denitration.

  According to this example, it was confirmed that the fluid was uniformly mixed because the coefficient of variation was lowered to about 5% which is the target value. Therefore, it can be said that the reaction efficiency between the catalyst and the fluid in the NOx removal catalyst layer 7 is improved and a high NOx removal efficiency can be maintained by causing the swirl flow by the guide member 11 d.

The other example (front view) of the turning part 11 is shown in FIG.
In this figure, the case where a guide member is used as the turning blade (vane) 11e is shown. As shown in FIG. 9 (B), although the vane 11e is a half-split plate and has less force compared to the cylindrical guide member 11d, the flow in the circumferential direction is formed, so the flow velocity does not decrease so much. In addition, since only a portion of the outer peripheral opening 11b is attached to the outer peripheral opening 11b instead of the entire outer peripheral opening 11b, the structure is simple and the manufacture is easy. In the illustrated example, four outer peripheral openings 11b and four vanes 11e are provided at the corners of the plate member 11a.

  A plurality of mixers 9 may be installed in the exhaust gas flow direction. Further, since the denitration reaction also depends on the exhaust gas temperature, the mixer 9 can be installed on the upstream side of the injection pipe 6 to use for the purpose of smoothing the deviation of the exhaust gas temperature. These are common to the other embodiments.

  Further, FIG. 10 shows another example (a schematic configuration diagram) of the NOx removal system 1. In this example, the case where the NOx removal catalyst layer 7 is provided also on the upstream side of the mixer 9 is shown, and the other configuration is the same as that of the first embodiment.

  In this case, the fluid passing through the NOx removal catalyst layer 7, that is, the exhaust gas from which NOx in the exhaust gas has been removed to some extent, flows into the mixer 9 and is mixed, and the remaining NOx is assured in the NOx removal catalyst layer 7 downstream. Removed. Therefore, the NOx removal rate is further improved. By providing a plurality of NOx removal catalyst layers 7, it becomes possible to make the reducing agent contained in the exhaust gas passing through the catalyst layers 7 uniform.

In the case where the denitration catalyst layer 7 is provided continuously (connected), a portion where the reaction proceeds more and a portion where the reaction does not proceed are generated while passing through the denitration catalyst layer 7. Part and thin part occur. Therefore, to realize high NOx removal, it is desirable to divide the NOx removal catalyst layer 7 and install the exhaust gas mixer 9 therebetween. By installing the mixer 9 in the middle of the plurality of NOx removal catalyst layers 7, it is possible to eliminate the bias of the reducing agent generated while flowing through the NOx removal catalyst layer 7.
A plurality of mixers 9 may be disposed in the exhaust gas duct 3, and the pivoting portion 11 shown in FIG. 9 may be used.

  Further, FIG. 11 shows another example (a schematic configuration diagram) of the NOx removal system 1. In this example, the mixer 9 is further provided in front of the NOx removal catalyst layer 7 on the upstream side, and the other configuration is the same as that of the second embodiment.

In order to ensure the dispersion of the reducing agent in the reducing agent injection nozzle 5, the mixer 9 may be installed also at the inlet of the first NOx removal catalyst layer 7.
When a plurality of NOx removal catalyst layers 7 are installed, by installing mixers 9 upstream of each catalyst layer 7, the reducing agent flowing in each catalyst layer 7 becomes uniform, so the catalyst can be used efficiently It is possible to reduce the amount of reducing agent used and to reduce the concentration of reducing agent in the gas discharged to the atmosphere. It is desirable that the gas discharged to the atmosphere contains a reducing agent, which causes an offensive odor, and therefore, it is desirable that the gas be consumed as efficiently as possible.

According to the present embodiment, by providing the mixers 9 in front of the NOx removal catalyst layers 7, the NOx removal effect is further enhanced because the exhaust gases and the reducing agent flow in a well-mixed state in each NOx removal catalyst layer 7. The higher the denitration rate will be achieved.
It is needless to say that the pivoting portion 11 shown in FIG. 9 may be used also in this embodiment.

  Besides denitration equipment, there is also the possibility of using it as a method of mixing two different fluids.

1 denitration device 3 exhaust gas duct 5 reducing agent injection nozzle 6 injection piping 7 denitration catalyst layer 9, 10 mixer
11, 14 Turning part 13 Mixing part

Claims (4)

In a fluid mixing device for mixing an exhaust gas discharged from a combustion apparatus including a boiler with a nitrogen oxide reducing agent injected into a flow path of the exhaust gas,
The fluid mixing device includes a swirling portion of the fluid and a fluid mixing portion provided downstream of the swirling portion on the downstream side of the exhaust gas flow, and the swirling portion is substantially perpendicular to the exhaust gas flow direction. A plate-like member having a flat portion, a plurality of outer peripheral openings formed along the outer periphery of the plate-like member, and a downstream side of the exhaust gas flow of each outer peripheral opening are in contact with the fluid. And each guiding member guiding in the direction;
The mixing unit is a conical member without a bottom, having a top on the upstream side of the exhaust gas flow and having a plurality of side openings on the side.   The plate-like member of the turning portion has a central opening formed on the center side of the outer peripheral opening, and the conical member of the mixing portion has the central opening as viewed from the exhaust gas flow direction. The fluid mixing device according to claim 1, wherein the fluid mixing device is arranged to be in an overlapping position with the part.   The fluid mixing device according to claim 1 or 2, wherein each guide member of the turning portion is a tubular member. A reducing agent injection unit for injecting a reducing agent of nitrogen oxide into a duct of an exhaust gas discharged from a combustion apparatus including a boiler, a mixing device for a fluid for mixing the exhaust gas and the reducing agent, nitrogen oxides in the exhaust gas A denitrification unit equipped with a denitrification catalyst for removing nitrogen oxides, which are disposed sequentially from the upstream to the downstream of the exhaust gas flow,
The fluid mixing apparatus according to any one of claims 1 to 3, wherein the fluid mixing apparatus is a fluid mixing apparatus according to any one of claims 1 to 3.