CN112569783A - Mixing device for mixing gases in a channel of rectangular cross section - Google Patents
Mixing device for mixing gases in a channel of rectangular cross section Download PDFInfo
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- CN112569783A CN112569783A CN201910939454.8A CN201910939454A CN112569783A CN 112569783 A CN112569783 A CN 112569783A CN 201910939454 A CN201910939454 A CN 201910939454A CN 112569783 A CN112569783 A CN 112569783A
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- 238000002156 mixing Methods 0.000 title claims abstract description 145
- 239000007789 gas Substances 0.000 title abstract description 32
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 135
- 229910021529 ammonia Inorganic materials 0.000 claims description 61
- 238000002347 injection Methods 0.000 claims description 43
- 239000007924 injection Substances 0.000 claims description 43
- 238000011144 upstream manufacturing Methods 0.000 claims description 8
- 239000000126 substance Substances 0.000 claims description 3
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 30
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 25
- 239000003546 flue gas Substances 0.000 description 25
- 238000009826 distribution Methods 0.000 description 13
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 12
- 239000003054 catalyst Substances 0.000 description 8
- 238000005192 partition Methods 0.000 description 8
- 238000000034 method Methods 0.000 description 7
- 238000005507 spraying Methods 0.000 description 7
- 230000000694 effects Effects 0.000 description 6
- 229910052757 nitrogen Inorganic materials 0.000 description 6
- 238000002955 isolation Methods 0.000 description 5
- 239000000779 smoke Substances 0.000 description 4
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 229910000975 Carbon steel Inorganic materials 0.000 description 2
- XKMRRTOUMJRJIA-UHFFFAOYSA-N ammonia nh3 Chemical compound N.N XKMRRTOUMJRJIA-UHFFFAOYSA-N 0.000 description 2
- 239000010962 carbon steel Substances 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 230000010349 pulsation Effects 0.000 description 2
- 230000003068 static effect Effects 0.000 description 2
- 230000004888 barrier function Effects 0.000 description 1
- 210000004027 cell Anatomy 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 210000004754 hybrid cell Anatomy 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000009828 non-uniform distribution Methods 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 125000006850 spacer group Chemical group 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/90—Injecting reactants
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/8621—Removing nitrogen compounds
- B01D53/8625—Nitrogen oxides
- B01D53/8631—Processes characterised by a specific device
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2258/00—Sources of waste gases
- B01D2258/02—Other waste gases
- B01D2258/0283—Flue gases
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- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Biomedical Technology (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Treating Waste Gases (AREA)
Abstract
The invention provides a mixing device for mixing gases in a channel of rectangular cross section, comprising a plurality of mixing units, each of which contains 4 baffle discs placed in a specific manner. The gas mixing device can realize the zone mixing of the gas.
Description
Technical Field
The invention relates to the field of energy environmental protection, in particular to a mixing device for mixing gas in a channel with a rectangular cross section.
Background
In the flue gas SCR denitration process of the coal-fired power plant, the ammonia/nitrogen molar ratio distribution standard deviation is required to be ensured to be less than 5% at the inlet section of the catalyst. To achieve this target value, good mixing of the flue gas/ammonia in the reactor inlet flue gas must be achieved. In order to enhance the mixing of the flue gas and the ammonia gas, a static mixer is arranged near an ammonia spraying nozzle to form forced turbulence, and the method is one of important means for realizing the full mixing of the flue gas and the ammonia. The structure of the mixer directly determines the mixing performance of the flue gas/ammonia gas.
Various mixers have been proposed for mixing flue gas and ammonia gas. These mixers are designed for the mixing uniformity of the whole flue cross section and can only control the overall concentration distribution regularity of the whole flue cross section or the catalyst inlet cross section.
The above mixing scheme is applicable when the concentration of nitrogen oxides is always kept the same throughout the entire denitration inlet cross section. However, in actual operation conditions, concentration values at various positions of the section of the denitration inlet are not completely equal, and distribution changes along with changes of the conditions. Under the condition, ammonia injection needs to be controlled finely, and at the moment, the mixing device is required to realize a mixing strengthening effect, and meanwhile, all small partitions need to be isolated and do not influence each other. Under these conditions, conventional static mixers are no longer suitable.
There remains a need for an improved mixer that can meet the requirements of a refined ammonia injection control process.
Disclosure of Invention
The invention provides a mixing device for mixing gas in a channel with a rectangular cross section, which is characterized by comprising a plurality of mixing units which are arranged along the long side direction of the rectangular cross section, wherein each mixing unit comprises a first baffling disc, a second baffling disc, a third baffling disc and a fourth baffling disc which have the same shape, the centers of the first baffling disc, the second baffling disc, the third baffling disc and the fourth baffling disc are positioned in the same rectangular cross section of the channel, the center connecting line of the first baffling disc and the second baffling disc and the center connecting line of the third baffling disc and the fourth baffling disc are both parallel to the short side direction of the rectangular cross section, the center connecting line of the first baffling disc and the third baffling disc and the center connecting line of the second baffling disc and the fourth baffling disc are both parallel to the long side direction of the rectangular cross section, the diameter d of the baffle disc is between 1/4 and 1/2 of the length of the short side of the rectangular section, and the nearest distance between the center of the baffle disc and the wall of the channel is between 0.5d and 1 d;
wherein the content of the first and second substances,
the included angle between the first baffling disc and the long side direction of the rectangular section is 0-30 degrees;
the included angle between the first baffling disc and the length direction of the channel is 0-60 degrees;
the included angle between the first baffling disc and the second baffling disc is 0-30 degrees;
the included angle between the first baffling disk and the third baffling disk is between 30 and 90 degrees;
the included angle between the third baffling disc and the fourth baffling disc is 0-30 degrees;
the center distance between the first baffling disk and the second baffling disk is 1.5 d-2 d; and is
The center distance between the first baffling disk and the third baffling disk is between 1d and 2 d.
Preferably, the mixing device comprises 3 to 8 of said mixing units.
Preferably, the distance between the centers of adjacent baffle discs in adjacent mixing units is between 1d and 4 d.
Preferably, the channel is a flue.
Preferably, the mixing device further comprises an ammonia injection nozzle upstream of the baffle disc, and the ammonia injection nozzle is spaced from the baffle disc by a distance of 0.5d to 1.5d in the channel length direction.
Preferably, the mixing device further comprises an ammonia injection nozzle downstream of the baffle disc, and the ammonia injection nozzle is spaced from the baffle disc by a distance of 0.5d to 1.5d in the channel length direction.
More preferably, the ammonia injection nozzles are divided into a plurality of groups in the long side direction of the rectangular cross section of the passage, and the groups of the ammonia injection nozzles have a one-to-one correspondence relationship with the mixing units.
Drawings
Figure 1 shows a perspective view of a section of a channel in which the gas mixing device of the present invention is located.
FIG. 2 is a top view of one embodiment of the channels and baffle disks therein shown in FIG. 1.
Fig. 3 is a left side view of unit a in fig. 2.
Figure 4 schematically shows a three-dimensional perspective view of an embodiment of the present invention.
Figure 5 schematically shows that the mixing device of figure 3 also comprises an ammonia injection nozzle upstream of the baffle disc.
Fig. 6 schematically shows a flue gas denitration apparatus having the mixing device of fig. 5 and an ammonia injection nozzle.
Figure 7 schematically shows that the mixing device of figure 3 also comprises an ammonia injection nozzle downstream of the baffle disc.
Figure 8 shows a smoke trace in one embodiment.
FIG. 9 shows the mixer catalyst inlet ammonia/nitrogen molar ratio distribution, where FIG. 9a is the case without the mixing device and FIG. 9b is the case with the mixing device of the present invention.
Detailed Description
The invention provides a gas mixing device. The device can realize the invisible isolation of a flow field area, can also realize the mixing reinforcement of a local area, and can meet the requirements of the existing refined ammonia spraying control process.
The invention provides a mixing device for mixing gas in a channel with a rectangular cross section, which is characterized by comprising a plurality of mixing units which are arranged along the long side direction of the rectangular cross section, wherein each mixing unit comprises a first baffling disc, a second baffling disc, a third baffling disc and a fourth baffling disc which have the same shape, the centers of the first baffling disc, the second baffling disc, the third baffling disc and the fourth baffling disc are positioned in the same rectangular cross section of the channel, the center connecting line of the first baffling disc and the second baffling disc and the center connecting line of the third baffling disc and the fourth baffling disc are both parallel to the short side direction of the rectangular cross section, the center connecting line of the first baffling disc and the third baffling disc and the center connecting line of the second baffling disc and the fourth baffling disc are both parallel to the long side direction of the rectangular cross section, the diameter d of the baffle disc is between 1/4 and 1/2 of the length of the short side of the rectangular section, and the nearest distance between the center of the baffle disc and the wall of the channel is between 0.5d and 1 d;
wherein the content of the first and second substances,
the included angle between the first baffling disc and the long side direction of the rectangular section is 0-30 degrees;
the included angle between the first baffling disc and the length direction of the channel is 0-60 degrees;
the included angle between the first baffling disc and the second baffling disc is 0-30 degrees;
the included angle between the first baffling disk and the third baffling disk is between 30 and 90 degrees;
the included angle between the third baffling disc and the fourth baffling disc is 0-30 degrees;
the center distance between the first baffling disk and the second baffling disk is 1.5 d-2 d; and is
The center distance between the first baffling disk and the third baffling disk is between 1d and 2 d.
The mixing device is used for mixing the gas in the channel with the rectangular cross section, and achieves the effect that the uneven gas from the upstream of the mixing device is mixed in each subarea after being subaread by the mixing device, and then flows to the downstream. The invention forms a mixing unit by means of a specific matching and combination of four baffle discs. The mixing units are arranged in parallel, the units are invisible and isolated or do not interfere with each other, and the gas is uniformly mixed in the units to be strengthened.
That is, after passing through the mixing device of the present invention, the gases within the passageway are mixed within each zone, but no mixing occurs between the zones. For example, the gas within a rectangular channel may be flue gas, and wherein the concentration of nitrogen oxides varies throughout the cross-section. A mixing device of the present invention is used in which there are, for example, 3 mixing units. After passing through the mixing device according to the invention, a region is formed downstream of each mixing unit in the rectangular duct, the concentration of nitrogen oxides in each region being homogenized, but not between the concentrations of nitrogen oxides in the 3 regions.
Without being bound to any theory, when the mixture is run into the mixing device, four strong turbulent air streams will be generated in each mixing unit to move downstream around the baffle discs due to the special combination of the four baffle discs. The generation of strong turbulent air flow can generate strong turbulent pulsation, the convection diffusion capability of air in the air flow can be obviously improved, and the air can be fully mixed finally. In the process, the space size and the motion range of the four air flows are determined by the diameters and the relative arrangement mode of the four baffle discs. The mutual matching relationship between the baffling disc and the inner wall of the channel in the mixing device can ensure that the movement range of the strong disturbance airflow is within the range of the designed mixing unit, thereby realizing the invisible isolation of each part of the gas in the channel.
The mixing device of the invention is especially useful for channels of rectangular cross-section, since the inner walls of the channels also participate in the gas mixing. The rectangular cross section in the present invention includes a substantially rectangular cross section. The cross-section has two pairs of substantially parallel sides and the deviation in parallelism is not more than 5 °. The corners may be rounded.
The mixing device comprises a plurality of mixing units which are arranged along the long side direction of the rectangular section. The mixing device may comprise 2, 3, 4, 5, 6, 7, 8 or more mixing units. Preferably, the mixing device comprises 3-8 mixing units, which is suitable for the length to width ratio of conventional channels. When the number of mixing units is too large, the contribution to the fine partition mixing is not greatly improved. These mixing units invisibly divide the channel into a corresponding number of gas mixing zones, but there is no physical partition between the individual mixing units.
Each mixing unit comprises four baffle discs with the same shape. In the present invention, the same shape of the baffle discs means that their diameters and thicknesses are substantially the same, with a deviation of not more than 5%. The baffle disc acts as a barrier to the flow of air. The thickness of the baffle disc is small compared to its diameter, typically in the range of 15 mm. The baffle disk can therefore be regarded essentially two-dimensionally. The baffle disc may be made of carbon steel, which is not a particular requirement of the invention.
The baffle discs may be fixed in the channels in a suitable manner. For example, by a thin bracket.
The centers of the four baffle discs in each mixing unit are all located in the same cross section of the channel. Furthermore, the centers of all baffle discs in all mixing units are located in the same cross section of the channel. In the present invention, lying within the same cross-section means lying substantially within the same cross-section with no more than 5% deviation from the median cross-section.
The four baffle discs may be named first to fourth baffle discs and their centers form a rectangle in the same direction as the channel. That is, the central connecting line of the first and second baffling disks and the central connecting line of the third and fourth baffling disks are parallel to the short side direction of the rectangular cross section of the channel, and the central connecting line of the first and third baffling disks and the central connecting line of the second and fourth baffling disks are parallel to the long side direction of the rectangular cross section of the channel. In other words, the center points of the four baffle discs form a rectangle whose four sides are parallel to the four sides of the channel.
The diameter d of the baffle disk is between 1/4 and 1/2 of the length of the short side of the rectangular cross section. Too small a diameter may result in insufficient mixing and too large a diameter may result in insufficient gas flow.
The baffle disc has a center closest to the wall of the channel at a distance of between 0.5d and 1 d. Too large a distance of the baffle discs from the channel walls may result in insufficient mixing and too small a distance may result in insufficient gas flow.
On the basis of the arrangement, the angle and the distance of each baffling disc are required to be set. The included angle between the first baffling disc and the long side direction of the rectangular section is 0-30 degrees; the included angle between the first baffling disc and the length direction of the channel is 0-60 degrees; the included angle between the first baffling disc and the second baffling disc is 0-30 degrees; the included angle between the first baffling disk and the third baffling disk is between 30 and 90 degrees; the included angle between the third baffling disc and the fourth baffling disc is 0-30 degrees; the center distance between the first baffling disk and the second baffling disk is 1.5 d-2 d; and the center distance between the first baffling disk and the third baffling disk is between 1d and 2 d.
Fig. 1 shows a perspective view of a section of a channel in which the gas mixing device of the invention is located, where the z-direction is the gas flow direction, parallel to the length of the channel. The cross section of the channel is rectangular, the x direction is parallel to the short side of the rectangular section, and the y direction is parallel to the long side of the rectangular section.
FIG. 2 is a top view of one embodiment of the channels and baffle disks therein shown in FIG. 1. Four mixing units a-D are shown arranged in the y-direction. Each mixing unit comprises four baffle discs 1-4. The dashed lines between the mixed units indicate that there is no physical spacer between adjacent units.
The centers of the four baffle discs form a rectangle, the central connecting lines of the discs 1 and 2 and 3 and 4 are parallel to the x direction, and the central connecting lines of the discs 1 and 3 and 2 and 4 are parallel to the y direction. The included angles of the discs 1, 2, 3 and 4 and the y direction are all 0 degrees.
Fig. 3 is a left side view of the unit a in fig. 2, i.e., a view in the y direction. Where disc 3 is actually located behind disc 1 and disc 4 is actually located behind disc 2.
The included angle between the disc 1 and the z direction is 30 degrees, and the included angle between the disc 1 and the disc 2 is 0 degree. The included angle between the disc 1 and the disc 3 is 90 degrees, and the included angle between the disc 3 and the disc 4 is 0 degree.
As the flow passes the baffle disk in the z direction, it is redirected by the four baffle disks and mixing is enhanced.
It should be understood that fig. 2 and 3 schematically illustrate only one embodiment of the present invention, and the structure of the present invention is not limited thereto.
Figure 4 shows a three-dimensional perspective view of one embodiment of the present invention.
Preferably, the distance between the centers of adjacent baffle discs in adjacent mixing units is between 1d and 4d, more preferably between 1.5d and 3 d. When the distances are too close, adjacent hybrid cells may interfere with each other. Too far, there may be unmixed gas passing between the mixing cells.
As described above, the mixing device of the present invention can realize the zoned homogenization in the channel gas.
The mixing device of the invention can be used for flue gas purification. For example, the mixing device is particularly suitable for flue gas denitration. In the flue gas denitration process, a plurality of ammonia injection nozzles or ammonia injection grids are usually arranged for injecting ammonia. Aiming at different distribution of nitrogen oxide concentration in flue gas at different positions in the cross section of the flue, the ammonia spraying amount of each nozzle is independently controlled, so that accurate ammonia spraying is realized. Although the ammonia injection amount exhibits a non-uniform distribution as viewed in the entire cross-section, it is desirable that the gas is uniform in the area of influence of each nozzle. The mixing device of the present invention achieves this objective.
Specifically, flue gas enters a flue of the denitration reactor from a denitration inlet, enters an area where an ammonia spraying nozzle is located after being guided by a guide device, contacts and mixes with ammonia gas sprayed out of the ammonia spraying nozzle, and continues to move upwards along a vertical flue together. The amount of ammonia gas emitted by the ammonia injection nozzle may be different in different regions. When the mixed gas in different areas runs to the mixing device, the mixed gas respectively meets different mixing units. Due to the special combination of four baffle discs, four strong turbulent air streams will be generated in each mixing unit and move downstream around the baffle discs. The generation of the strong turbulent air flow can generate strong turbulent pulsation, the convection diffusion capability of the air in the air flow can be obviously improved, and finally, the air in each mixing unit can be fully mixed. In the process, the space size and the motion range of the four air flows are determined by the diameters and the relative arrangement mode of the four baffle discs. Through the design mode of the invention, the gases are basically not mixed among the mixing units, and uniform mixing is formed in each mixing unit. Namely, the movement range of the strong disturbance airflow can be ensured within the range of the designed mixing unit through the matching relationship between the baffling disc and the inner wall of the channel in the mixing device, so that the invisible isolation of each part of the gas in the channel is realized.
The mixing device of the invention is a passive mixing device, and does not need power drive. This is advantageous from the viewpoint of energy saving. In addition, the mixing device of the present invention is simple in geometric construction and easy to prepare and clean.
Preferably, the ammonia gas is injected into the flue by an ammonia injection nozzle upstream of the mixing device, and the distance between the ammonia injection nozzle and the mixing device in the length direction of the flue is between 0, 5d and 1.5 d. This distance arrangement allows to achieve an optimal ammonia/flue gas mixing effect.
Figure 5 schematically shows the mixing device of figure 3 further comprising an ammonia injection nozzle upstream of the baffle disc, and the ammonia injection nozzle is spaced from the baffle disc by a distance of between 0.5d and 1.5d in the length direction of the flue. In the figure, the flue gas flows upwards. The ammonia injection nozzle traverses the flue and is provided with an ammonia gas injection hole for injecting ammonia gas into the flue.
The ammonia gas sprayed into the flue is mixed with the flue gas and then enters the mixing unit together. In each mixing unit, mixing is sufficient, and between the mixing units, the gases do not substantially interfere with each other.
Preferably, the ammonia injection nozzles are divided into a plurality of groups in the long side direction of the rectangular section of the flue, and the groups of the ammonia injection nozzles and the mixing units have one-to-one correspondence relationship, so that fine ammonia injection control is facilitated. Of course, as shown in fig. 5, in each mixing unit, there may be a plurality of ammonia injection nozzles in the long side direction of the rectangular cross section of the flue.
Fig. 6 schematically shows a flue gas denitration apparatus having a mixing device of the present invention. After passing through the mixing device of the present invention, the gases reaching the SCR reactor are thoroughly and uniformly mixed in the downstream region of the corresponding zone unit.
The mixing device of the invention can also be arranged upstream of the ammonia injection nozzle, i.e. for providing the ammonia injection nozzle with zoned homogenized flue gas.
Figure 7 schematically shows that the mixing device of figure 3 also comprises an ammonia injection nozzle downstream of the baffle disc, and the ammonia injection nozzle is spaced from the baffle disc by a distance of between 0.5d and 1.5d in the length direction of the flue. In the figure, the flue gas flows upwards. The ammonia injection nozzle traverses the flue and is provided with an ammonia gas injection hole for injecting ammonia gas into the flue.
The flue gas passes through a mixing device to be mixed in a subarea mode before reaching the ammonia spraying nozzle. Thus, fine ammonia injection control is facilitated for each partition.
Also, preferably, the ammonia injection nozzles are divided into a plurality of groups in the long side direction of the rectangular cross section of the flue, and the groups of the ammonia injection nozzles have a one-to-one correspondence relationship with the mixing units, so as to facilitate fine ammonia injection control.
Figure 8 illustrates a smoke trace within a channel in one embodiment. The flue gas flows from the lower part to the upper part. It can be seen from the figure that the mixing is initially a straight flow. After the subarea mixer is additionally arranged and passes through the mixing device, the smoke of each subarea is isolated, and the smoke in the subareas is fully mixed.
Examples
Example 1:
the mixing device of the present invention is first constructed.
The cross section of the flue is 14450 multiplied by 2900 mm.
The size of the baffling disc is phi 900mm, the material is carbon steel, and the baffling disc is fixed in the flue in a mode of being welded on the auxiliary supporting rod.
A total of 6 mixing units were provided in the flue. The center-to-center spacing of the baffle discs between adjacent mixing units was 1350 mm.
The distance between the center of the first baffling disc in the outermost mixing unit and the long side and the short side of the flue is 850mm and 900 mm. The included angle between the first baffling disc and the long side of the cross section of the flue is 0 degree, and the included angle between the first baffling disc and the length direction of the flue is 50 degrees. The center distance between the first baffling disc and the second baffling disc is 1350mm, and the included angle is 0 degree. The central distance between the first baffling disc and the third baffling disc is 1150mm, and the included angle is 80 degrees. The center distance between the third baffling disc and the fourth baffling disc is 1350mm, and the included angle is 0 degree.
The ammonia injection nozzle is arranged at the upstream of the mixing device and is spaced 900mm from the baffling disc.
In the flue duct provided with the above-mentioned baffle discs, flue gas was supplied at a speed of 15m/s, and ammonia gas was supplied from an ammonia injection nozzle at a speed of 20 m/s.
The mixing effect of ammonia and flue gas is that the catalyst inlet section can still be ensured under the condition that the distribution of nitrogen oxides at the inlet is very uneven, and the relative standard deviation of the ammonia nitrogen molar ratio distribution is less than 5%. That is, for different zones of nitrogen oxide concentration, different amounts of ammonia gas are injected but in the same proportion as the nitrogen oxides, and uniform mixing of ammonia nitrogen is achieved in each zone. This can be confirmed by the measurement of ammonia concentration and nitrogen oxide concentration distribution at the inlet section of the catalyst, and also can be indirectly confirmed according to the nitrogen oxide concentration distribution at the outlet of the denitration. FIG. 9b shows the mixer catalyst inlet ammonia/nitrogen molar ratio distribution. The ammonia/nitrogen molar ratio distribution relative standard deviation Cv was 4.2%.
Comparative example:
under the same conditions, no mixer was used for mixing and ammonia sparging.
Figure 9a shows the catalyst inlet ammonia/nitrogen molar ratio distribution when no mixer is used. When the zoned forced mixer was not used, the catalyst inlet cross-section ammonia/nitrogen molar ratio distribution had a relative standard deviation Cv of 15.5%.
As can be seen from the comparison of examples and comparative examples, when the mixing device constructed according to the present invention was used, the gas mixing effect was significantly better.
The four baffling disks are specially matched and combined to form a mixing unit, so that partition isolation among the units is realized, and mixing in the units is strengthened. The advantages are mainly embodied in the following aspects:
(1) the partition isolation of the flue gas flow field along the long edge direction of the flue can be realized without a physical device (such as a partition plate added in the flue);
(2) because the mixing range is shortened, the mixing effect is better in each partition unit;
(3) the modular design can be realized, and the design flow of the mixing element is simplified.
It will be apparent to those skilled in the art that various changes and modifications may be made in the embodiments of the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (7)
1. A mixing device for mixing gas in a channel with a rectangular cross section is characterized by comprising a plurality of mixing units which are arranged along the long side direction of the rectangular cross section, each mixing unit comprises a first baffling disk, a second baffling disk, a third baffling disk and a fourth baffling disk which are identical in shape, the centers of the first baffling disk, the second baffling disk, the third baffling disk and the fourth baffling disk are positioned in the same rectangular cross section of the channel, the center connecting line of the first baffling disk and the second baffling disk and the center connecting line of the third baffling disk and the fourth baffling disk are all parallel to the short side direction of the rectangular cross section, the center connecting line of the first baffling disk and the third baffling disk and the center connecting line of the second baffling disk and the fourth baffling disk are all parallel to the long side direction of the rectangular cross section, the diameter d of the baffle disc is between 1/4 and 1/2 of the length of the short side of the rectangular section, and the nearest distance between the center of the baffle disc and the wall of the channel is between 0.5d and 1 d;
wherein the content of the first and second substances,
the included angle between the first baffling disc and the long side direction of the rectangular section is 0-30 degrees;
the included angle between the first baffling disc and the length direction of the channel is 0-60 degrees;
the included angle between the first baffling disc and the second baffling disc is 0-30 degrees;
the included angle between the first baffling disk and the third baffling disk is between 30 and 90 degrees;
the included angle between the third baffling disc and the fourth baffling disc is 0-30 degrees;
the center distance between the first baffling disk and the second baffling disk is 1.5 d-2 d; and is
The center distance between the first baffling disk and the third baffling disk is between 1d and 2 d.
2. Mixing device according to claim 1,
the mixing device comprises 3 to 8 of the mixing units.
3. Mixing device according to claim 1,
the center distance between adjacent baffle discs in adjacent mixing units is between 1d and 4 d.
4. Mixing device according to claim 1,
the passageway is a flue.
5. The mixing device of claim 1, further comprising an ammonia injection nozzle upstream of the baffle disc, and wherein the ammonia injection nozzle is spaced from the baffle disc by between 0.5d and 1.5d in the channel length direction.
6. The mixing device of claim 1, further comprising an ammonia injection nozzle downstream of the baffle disk, and wherein the ammonia injection nozzle is spaced from the baffle disk by between 0.5d and 1.5d in the channel length direction.
7. The mixing device according to claim 5 or 6, wherein the ammonia injection nozzles are divided into a plurality of groups in a long side direction of the rectangular cross section of the passage, and the groups of the ammonia injection nozzles have a one-to-one correspondence with the mixing units.
Priority Applications (1)
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