An ammonia injection mixing unit and a denitration system using the same

Abstract

The application discloses a kind of ammonia injection mixing units, be applied to the flue gas denitrification system without dust inside and install in flue, comprising: main pipe, it is laid in the direction of vertical flue gas flow direction in flue and lead into ammonia or ammonia air mixed gas;Branch pipe, the number is multiple, the branch pipe is communicated with main pipe and extends along the direction of flue gas;The free end of the branch pipe is equipped with a bearing, one end of the bearing is fixedly connected with the branch pipe, the other end is connected with a hollow rotating shaft, the hollow rotating shaft is communicated with the branch pipe;Distribution pipe, it is set on hollow rotating shaft and is in communication state, the distribution pipe is evenly distributed along the circumference of hollow rotating shaft;Multiple ammonia injection orifices with a certain angle between injection direction and flue gas flow direction are provided on distribution pipe;Rotational vane, it is fixedly connected in the middle of branch pipe in flue, for converting axial airflow into radial rotational airflow in the process of flue gas and ammonia gas mixing.The application is suitable for lower allowable installation height in old boiler denitrification reconstruction and in the flue gas denitrification device without dust or with lower dust amount.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flue gas denitration technology, and particularly relates to a kind of ammonia injection mixing unit and the denitration system of application of unit. BACKGROUND

[0002] The existing flue gas denitration method mainly includes selective catalytic reduction (SCR) technology, selective non-catalytic reduction (SNCR) technology, SNCR / SCR combined flue gas denitration technology, etc. Among them, the SCR technology has the advantages of mature technology, high denitration efficiency, stable operation, etc., and has become the most widely used flue gas denitration technology at home and abroad. The main principle of SCR technology is to inject reducing agent ammonia into flue gas and mix uniformly, under the action of SCR denitration catalyst, ammonia (NH3) reduces nitrogen oxides (NO x ) in flue gas into non-toxic and non-polluting nitrogen and water, so as to achieve the purpose of removing NO x in flue gas.

[0003] For the SCR denitration technology, the mixing effect of ammonia and flue gas is the key and difficulty in the design and operation of SCR device, and is also the key factor to ensure complete SCR denitration reaction, improve denitration efficiency and ammonia utilization rate, and control low ammonia escape rate. Where NH3 / NO x is too high, the ammonia escape rate will increase; where NH3 / NO x is too low, the denitration efficiency cannot be guaranteed. DL / T 296-2011 "Technical Guidelines for Flue Gas Denitration in Thermal Power Plants" stipulates that the deviation of NH3 / NO x molar ratio at 100% flue cross-section flue gas 500mm before the first layer of catalyst inlet of SCR reactor should be -10% to 10%.

[0004] The mixing effect of ammonia and flue gas is mainly determined by the ammonia injection mixing system. In "Coal-fired Flue Gas Denitration Ammonia Injection Mixing System" (GB / T 34339-2017), the ammonia injection mixing system is divided into ammonia injection grid (AIG) and ammonia injection static mixer. AIG is a spraying device that injects ammonia into the flue in the form of grid pipeline, including ammonia injection pipeline, nozzle, support and accessories; static mixer is a device that uses certain fixed components to change the flow state of ammonia and flue gas to achieve full mixing. Typical ammonia injection static mixers include vortex, cyclone, longitudinal vortex, V-shaped structure, etc.

[0005] The ammonia injection grid and the ammonia injection static mixer are separate devices, each of which requires a certain installation space (height); and the ammonia injection mixing system of the above structure requires a long mixing distance. However, most of the existing boilers have been built for a long time, and when they were built, the environmental protection standards were relatively loose, and there was no need for flue gas denitrification at that time, so there is no denitrification space reserved in the boiler, and the layout is relatively compact, and the idle installation height / space is limited, so it is difficult to use the above-mentioned ammonia injection mixing system for denitrification modification.

[0006] For example, Chinese patent application CN112742232A discloses an ammonia injection static mixer, which is one or more layers and is arranged in the flue. Each layer of the mixer is composed of a plurality of static mixer units and is distributed in a matrix. The static mixer unit includes: a reduced diameter section, which is a tubular structure with a small upper part and a large lower part, for increasing the flow rate of the ammonia and flue gas mixture; and a turbulence section located above the reduced diameter section and communicating with the reduced diameter section. The turbulence section is provided with a turbulence component for splitting the mixture, so that the mixture forms a vortex at the back of the turbulence section. Although this type of static mixer can significantly reduce the deviation of the gas velocity distribution and the deviation of the ammonia concentration distribution on the same cross section of the flue, the required mixing distance is still required; and this type of ammonia injection static mixer has a large pressure drop, and is mainly used for flue gas containing dust, and is not suitable for denitrification of flue gas of heating furnaces, gas power furnaces, ethylene cracking furnaces, waste acid regeneration of alkylation, and other chemical devices.

[0007] Therefore, there is an urgent need for an ammonia injection mixing unit and a denitrification system applying the unit, which can realize uniform mixing of ammonia and flue gas in a short distance, and is suitable for low allowable installation height in old boiler denitrification modification and flue gas denitrification devices with low dust content or low dust content.

[0008] The information disclosed in this BACKGROUND section is only intended to increase an understanding of the general context in which the present application can be practiced. It is not admitted that any of the information provided in this BACKGROUND section constitutes prior art. SUMMARY

[0009] The purpose of the present application is to provide an ammonia injection mixing unit and a denitrification system applying the unit, which can realize uniform mixing of ammonia and flue gas in a short distance by converting axial airflow into radial rotating airflow, and is suitable for low allowable installation height in old boiler denitrification modification and flue gas denitrification devices with low dust content or low dust content.

[0010] Another purpose of the present application is to further improve the uniformity of mixing of ammonia and flue gas by the rotatable distribution pipe.

[0011] To achieve the above object, according to a first aspect of the present application, the present application provides an ammonia injection mixing unit applied in a dust-free flue gas denitration system and installed in a flue, comprising: a main pipe arranged in the flue in the direction perpendicular to the flue gas flow and into which ammonia gas or ammonia-air mixed gas is fed; a plurality of branch pipes in communication with the main pipe and extending along the flue gas flow; a bearing arranged at the free end of the branch pipe, one end of the bearing being fixedly connected with the branch pipe and the other end being connected with a hollow rotating shaft in communication with the branch pipe; a distribution pipe arranged on the hollow rotating shaft and in communication, the distribution pipe being uniformly distributed along the circumference of the hollow rotating shaft; a plurality of ammonia injection holes with a certain angle between the injection direction and the flue gas flow direction being arranged on the distribution pipe; and a cyclone vane fixedly connected to the middle part of the branch pipe in the flue for converting the axial gas flow into radial rotating gas flow during the mixing of the flue gas and the ammonia gas.

[0012] Further, in the above technical solution, the cyclone vane can adopt a curved surface structure corresponding to the position of the ammonia injection hole, and the curved surface structure guides the axial gas flow into radial rotating gas flow.

[0013] Further, in the above technical solution, the angle between the opening direction of the ammonia injection hole and the flue gas flow direction can be 15-75°.

[0014] Further, in the above technical solution, the distribution pipe can be four and arranged in a cross shape.

[0015] Further, in the above technical solution, the distribution pipe can be arranged in multiple layers, and each layer of the distribution pipe is uniformly arranged on the circumference centering on the hollow rotating shaft; the projection of each layer of the distribution pipe on the flue cross section does not coincide.

[0016] Further, in the above technical solution, the distribution pipe can be arranged in two layers, and the projections of the two layers of the distribution pipe on the flue cross section are uniformly and spacedly arranged.

[0017] Further, in the above technical solution, a rotating piece can be arranged above the distribution pipe, the rotating piece can be fixedly connected to the top of the hollow rotating shaft, and in the case that the amount of ammonia injection is small and the distribution pipe cannot be driven to rotate, the rotating piece is driven to rotate by the flue gas, thereby driving the distribution pipe to rotate.

[0018] Further, in the above technical solution, the number of main pipes can be multiple and uniformly spaced in the flue, or the main pipe is extended by a connecting pipe to form multiple rows; the overall structure formed by the multiple main pipes, the multiple branch pipes on each main pipe or the connecting pipe, and the multiple distribution pipes on each branch pipe forms full coverage on the flue cross section.

[0019] Further, in the above technical solution, the installation height of the overall structure can be 0.7-1.2 meters.

[0020] Further, in the technical scheme, the system pressure drop of the ammonia injection mixing unit is less than 100 Pa; the NOx concentration in the flue gas after denitration is less than 30 mg / Nm x <30mg / Nm 3 .

[0021] According to the second aspect of the present application, the present application provides a denitration system suitable for flue gas denitration without dust, comprising the ammonia injection mixing unit of any one of the preceding aspects.

[0022] Further, in the technical scheme, the ammonia injection mixing unit can be arranged upstream of the denitration unit in the flue duct.

[0023] Further, in the technical scheme, a flow meter and a flow regulating valve can be arranged on the extension pipeline of each mother pipe of the ammonia injection mixing unit.

[0024] Further, in the technical scheme, the gas source of each mother pipe can be provided by an ammonia injection main pipe, and an ammonia-air mixer can be arranged on the ammonia injection main pipe, and the ammonia-air mixer can be provided with air through a dilution air pipeline.

[0025] Further, in the technical scheme, the dilution air pipeline can comprise: a dilution air main pipe for diluting the ammonia gas concentration to below the explosion limit; and as many dilution air branch pipes as the number of the mother pipes, and each dilution air branch pipe is controlled by a valve, and when it is detected that the flue duct has flue gas flowing therethrough, the valve is in an open state to ensure that gas is always sprayed out of the ammonia injection orifice.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] 1. The ammonia injection mixing system arranged in the flue duct of the conventional flue gas SCR denitration generally comprises an ammonia injection grid and an ammonia injection static mixer, and requires a high installation height; the present application can significantly reduce the installation height required by the ammonia injection mixing unit in the flue duct by converting the axial airflow into radial rotating airflow under the premise of achieving sufficient mixing, and is particularly suitable for denitration modification of old boilers / process heating furnaces / cracking furnaces that have been operated for many years; since the existing ammonia injection grid and ammonia injection static mixer are replaced, the weight of the equipment required to be added in the flue duct is greatly reduced, and at the same time, the boiler foundation and frame do not need to be changed, but only need to be reinforced, which is particularly suitable for denitration modification of old boilers that have been operated for many years, and can significantly reduce the modification cost;

[0028] 2、The ammonia injection hole of the application is arranged obliquely (with a certain angle with the vertical direction), and the ammonia gas or ammonia-air mixed gas is injected from the ammonia injection hole, on the one hand, the oblique injection gas flow obtains a reaction force in the horizontal direction to make the distribution pipe rotate (to make the ammonia gas distribution more uniform), on the other hand, the oblique downward ammonia gas or ammonia-air mixed gas can be mixed with the vertically running flue gas at the moment of injection, compared with the opening direction being the same direction as the flue gas, a better mixing effect can be obtained. When the preliminarily mixed flue gas and ammonia gas or ammonia-air mixed gas run downward to the cyclone vane, the axial gas flow can be converted into radial rotating gas flow through the guiding effect of the cyclone vane fixed on the branch pipe. Through the preliminary mixing mode, the distribution pipe can realize annular uniform distribution of the ammonia gas or ammonia-air mixed gas on the circumference with the hollow rotating shaft as the center line, and then the cyclone vane makes the ammonia gas and flue gas rotate around the branch pipe, to strengthen the further mixing of the flue gas and ammonia gas;

[0029] 3、When the branch pipe is provided with multiple layers of distribution pipes, the distribution pipes are arranged staggered in the flue gas flow direction, on the one hand, the distribution pipe forms a turbulent flow to the flue gas to accelerate the mixing of the ammonia gas and flue gas, on the other hand, the uniformity of the ammonia gas distribution in the plane perpendicular to the flue gas flow direction is strengthened;

[0030] 4、The distribution pipe is provided with a rotating piece above, the flue gas flow pushes the rotating piece to rotate, thereby driving the distribution pipe to rotate, so that the rotating speed of the distribution pipe can be accelerated, and the uniformity of the mixing of the ammonia gas and flue gas is improved, when the ammonia injection amount is low, the setting of the rotating piece can effectively ensure the normal rotation of the distribution pipe, and then ensure the uniformity of the mixing of the ammonia gas and flue gas;

[0031] 5、The branch pipe is provided with a cyclone vane, the flue gas and ammonia gas flowing through the cyclone vane rotate around the branch pipe, to strengthen the mixing degree of the flue gas and ammonia gas in the longitudinal direction and the mixing degree of the flue gas and ammonia gas between adjacent distribution pipes, further improve the uniform distribution degree of the ammonia gas in the flue gas, thereby shortening the distance required for the uniform mixing of the ammonia gas or ammonia-air mixed gas and flue gas;

[0032] 6、The ammonia injection and mixing unit of the application is applied to the flue gas denitration system without dust or with low dust amount, so that the distribution pipe can be provided with the ammonia injection hole with small aperture and large quantity, the gas speed of the injected ammonia gas or ammonia-air mixed gas can be higher, and the rotating flow effect is better after cooperating with the cyclone vane, test proves that the effect of the high-precision ammonia gas nozzle in the existing ammonia injection and mixing system can be completely achieved, and the existing expensive ammonia injection equipment can be replaced;

[0033] 7、The ammonia injection and mixing unit of the application makes the system pressure drop lower, and is especially suitable for the flue gas denitration of the heating furnace, ethylene cracking furnace and gas power furnace which are sensitive to the pressure drop, the pressure drop increased by the ammonia injection and mixing unit of the application is within the operation elastic range of the furnace body, so that the furnace body does not need to be reinforced or the fan does not need to be replaced.

[0034] 8、The ammonia injection mixing unit structure is relatively simple, can realize modular mass production, and effectively reduces production and installation costs.

[0035] The above description is only a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application and can be implemented according to the content of the specification, at the same time, in order to make the above and other purposes, technical features and advantages of the present application more easily understood, one or more preferred embodiments are listed below, and the following is described in detail with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a structural schematic diagram of the first embodiment of the ammonia injection mixing unit of the present application (without connecting pipe).

[0037] Figure 2 is Figure 1 is a schematic diagram of the arrangement of multiple ammonia injection mixing units in the flue.

[0038] Figure 3 is Figure 1 is another angle schematic diagram (showing the arrangement of ammonia injection holes).

[0039] Figure 4 is a structural schematic diagram of the second embodiment of the ammonia injection mixing unit of the present application (by setting a connecting pipe, multiple rows of branch pipes can be set on the basis of one mother pipe; the distribution pipe is two layers and a rotating piece is arranged above the distribution pipe).

[0040] Figure 5 is Figure 4 is a schematic diagram of the arrangement of multiple ammonia injection mixing units in the flue.

[0041] Figure 6 is Figure 4 is another angle schematic diagram (showing the arrangement of ammonia injection holes and rotating pieces).

[0042] Figure 7 is a schematic diagram of the arrangement of the denitration system of the present application.

[0043] Figure 8 is a control schematic diagram of the ammonia injection mixing unit in the denitration system of the present application.

[0044] Figure 9 is another control schematic diagram of the ammonia injection mixing unit in the denitration system of the present application (showing the arrangement of the dilution air main pipe and the dilution air branch pipe).

[0045] MAIN REFERENCE NUMERALS:

[0046] 10 - flue; 20 - ammonia injection mixing unit, 21 - main pipe, 22 - branch pipe, 23 - distribution pipe, 24 - ammonia injection hole, 25 - swirl vane, 26 - hollow rotating shaft, 27 - bearing, 28 - rotating blade, 29 - connecting pipe; 30 - denitration unit, 31 - denitration catalyst bed; 41 - ammonia injection main pipe, 42 - ammonia-air mixer, 43 - dilution air pipe line, 43A - dilution air main pipe, 43B - dilution air branch pipe, 44 - first flow regulating valve, 45 - second flow regulating valve, 46 - first flow meter, 47 - second flow meter. DETAILED DESCRIPTION

[0047] The specific embodiments of the present application will be described in detail below with reference to the drawings, but the scope of protection of the present application is not limited by the specific embodiments.

[0048] Unless otherwise clearly indicated, throughout the specification and claims, the term "comprise" or variations such as "comprises" or "comprising" will be understood to imply the inclusion of a stated element or group of elements but not the exclusion of any other element or group of elements.

[0049] In this document, spatially relative terms, such as "beneath", "below", "lower", "above", "upper", and the like, can be used to describe one element's or feature's relationship to another element or feature as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the object in use or operation in addition to the orientations depicted in the figures. For example, if an object in the figures is turned over, then a downwardly facing surface would then be an upwardly facing surface, and vice versa. Thus, the exemplary term "below" can encompass both a downward and upward orientation. The object can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative terms used herein interpreted accordingly.

[0050] In this document, the terms "first", "second", etc. are used to distinguish one element from another, and are not used to designate a particular position or relative relationship. In other words, in some embodiments, the terms "first", "second", etc. can be interchanged with each other.

[0051] The ammonia injection grid and / or ammonia injection static mixer provided in the flue for conventional flue gas SCR denitration requires a high installation height, and the ammonia injection mixing unit used in the present application can significantly reduce the installation height required for the ammonia injection mixing system in the flue, and is particularly suitable for denitration modification of old boilers / process heating furnaces / cracking furnaces that have been in operation for many years. The ammonia injection mixing unit of the present application replaces the conventional ammonia injection grid and ammonia injection static mixer, and the required increase in equipment weight in the flue is greatly reduced, and at the same time the boiler foundation and frame do not need to be modified, only need to be reinforced.

[0052] As Figures 1 to 3 shown in the figure, the present application provides a first embodiment of the ammonia injection mixing unit, which is applied in the flue gas denitration system without dust and installed in the flue 10, including the main pipe 21, branch pipe 22, distribution pipe 23 and the cyclone vane 25. Among them, the main pipe 21 is arranged in the flue 10 in the direction perpendicular to the flue gas flow and is connected to the ammonia gas or ammonia air mixture; the branch pipe 22 is multiple in number, and the branch pipe 22 is communicated with the main pipe 21 and extends along the flue gas direction; the free end of the branch pipe 22 is sleeved with a bearing 27, one end of which is fixedly connected with the branch pipe 22, and the other end is connected with a hollow rotating shaft 26, which is communicated with the branch pipe 22. The distribution pipe 23 is arranged on the hollow rotating shaft 26 and is in communication with the hollow rotating shaft, and the distribution pipe 23 is uniformly distributed along the circumferential direction of the hollow rotating shaft 26; the distribution pipe 23 is provided with a plurality of ammonia injection holes 24 with a certain angle (i.e. α angle, preferably 15-75°) between the injection direction and the flue gas flow direction (for reference Figure 3 ); the cyclone vane 25 is fixedly connected to the middle part of the branch pipe 22 in the flue 10, which is used to convert the axial airflow into radial rotating airflow during the mixing of flue gas and ammonia gas. As Figures 1-3 shown in the figure, the flue gas runs downward in the figure, and the opening direction of the ammonia injection hole 24 is inclined downward, which can obtain a reaction force in the horizontal direction on the one hand, so that the distribution pipe can rotate (so that the ammonia gas is more evenly distributed), and on the other hand, the inclined downward ammonia gas or ammonia air mixture can be mixed with the vertically running flue gas at the moment of injection, which can obtain better mixing effect compared with the setting of the opening direction in the same direction of the flue gas. When the preliminarily mixed flue gas and ammonia gas or ammonia air mixture runs downward to the cyclone vane 25, the axial airflow can be converted into radial rotating airflow through the guiding action of the cyclone vane 25 fixed on the branch pipe. Through the preliminary mixing, the distribution pipe 23 can realize the annular uniform distribution of the ammonia gas or ammonia air mixture on the circumference with the hollow rotating shaft 26 as the center line, and then the ammonia gas is rotated around the branch pipe 22 through the cyclone vane 25, which can strengthen the further mixing of the flue gas and the ammonia gas, improve the uniformity of the ammonia gas distribution in the same plane (perpendicular to the flue gas flow direction), shorten the distance required for the uniform mixing of the ammonia gas or ammonia air mixture and the flue gas, and thus reduce the overall installation height of the ammonia injection mixing unit.

[0053] Further as Figures 1 to 3 shown, the cyclone vane 25 adopts a curved surface structure corresponding to the position of the ammonia injection hole 24, which can guide the axial airflow into radial rotating airflow. The inventors have found through research that the ammonia injection mixing unit of the present application is applied in the flue gas denitration system without dust or with low dust content, so that a small aperture and a large number of ammonia injection holes can be arranged on the distribution pipe, which can achieve the effect of high-precision ammonia nozzle in the existing ammonia injection mixing system after cooperating with the cyclone vane 25. Due to the simple structure and light weight, it has good economic advantages.

[0054] Figures 1 to 3 In the first embodiment shown in the figure, the distribution pipes 23 can be four and arranged in a cross shape. Other arrangements such as a H-shaped or star-shaped arrangement can also be used, for example in the manner shown in the figure. When the distribution pipes are arranged in one layer, the number of mother pipes 21 can be set to multiple and arranged uniformly in the flue 10 (seven are shown in the figure). The overall structure formed by the multiple mother pipes, the multiple branch pipes on each mother pipe, and the multiple distribution pipes 23 on each branch pipe forms full coverage of the cross section of the flue 10 (see the figure). Figure 4 By this means, the mixing of the flue gas and the ammonia gas in the flue 10 can be ensured to the maximum extent. At the same time, the overall installation height of the unit can be controlled to about 0.7-0.9 meters on the basis of ensuring a certain mixing efficiency when the distribution pipes 23 are arranged in one layer. Figure 2 Figure 2 The present application also provides another embodiment of the ammonia injection mixing unit, as shown in the figure, that is, the distribution pipes 23 are arranged in multiple layers, and each layer of distribution pipes 23 is uniformly arranged on the circumference of the hollow rotating shaft 26. The projections of each layer of distribution pipes 23 on the cross section of the flue 10 do not overlap, so that the injected ammonia gas or ammonia-air mixed gas can be more dense, and at the same time, the ammonia gas injected from each ammonia injection hole does not interfere with each other and can be normally mixed and contacted with the flue gas. Preferably but not limitatively, the distribution pipes 23 are arranged in two layers (as shown in the figure), and the projections of the two layers of distribution pipes 23 on the cross section of the flue 10 are uniformly and spacedly arranged.

[0055] The present application also provides another embodiment of the ammonia injection mixing unit, as shown in the figure, that is, the distribution pipes 23 are arranged in multiple layers, and each layer of distribution pipes 23 is uniformly arranged on the circumference of the hollow rotating shaft 26. The projections of each layer of distribution pipes 23 on the cross section of the flue 10 do not overlap, so that the injected ammonia gas or ammonia-air mixed gas can be more dense, and at the same time, the ammonia gas injected from each ammonia injection hole does not interfere with each other and can be normally mixed and contacted with the flue gas. Preferably but not limitatively, the distribution pipes 23 are arranged in two layers (as shown in the figure), and the projections of the two layers of distribution pipes 23 on the cross section of the flue 10 are uniformly and spacedly arranged. Figures 4 to 6 In this embodiment, the mother pipes 21 can be extended by the connecting pipes 29 to form multiple rows (see the figure). By this means, compared with the first embodiment in which each row corresponds to one mother pipe, the self-weight of the unit can be further reduced, and the installation is more convenient. The overall structure formed by the multiple mother pipes, the multiple branch pipes on the connecting pipes 29, and the multiple distribution pipes 23 on each branch pipe also forms full coverage of the cross section of the flue 10 (see the figure).

[0056] Figure 4 The overall installation height of the unit can be controlled to about 0.9-1.2 meters when the distribution pipes 23 are arranged in two or more layers. Figure 5 Further referring to the figures, preferably but not limitatively, a rotating vane 28 can also be arranged above the distribution pipes 23. The rotating vane 28 is fixedly connected to the top of the hollow rotating shaft 26, and is used to drive the rotating vane 28 to rotate by the flue gas when the amount of ammonia gas to be injected is small and the distribution pipes 23 cannot be driven to rotate, thereby driving the distribution pipes 23 to rotate.

[0057] Figure 4 Figure 6

[0058] ​​​​​The mechanism of the ammonia injection mixing unit of the present application is as follows: ammonia gas or ammonia-air mixture is introduced into each distribution pipe 23 from the main pipe 21 through the branch pipe 22, the ammonia injection holes 24 are arranged obliquely, and the ammonia gas or ammonia-air mixture is injected from the ammonia injection holes 24, which is pushed by the reaction force to rotate the hollow rotating shaft 26 around the center line of the hollow rotating shaft 26, so that the ammonia gas can be uniformly distributed in a ring shape in a plane perpendicular to the flow direction of the flue gas, and the preliminary mixing effect of the flue gas and the ammonia gas can be improved due to the certain angle between the flow direction of the flue gas and the injection direction of the ammonia gas. When the rotating blades 28 are arranged above the distribution pipe 23, a horizontal pushing force is generated on the rotating blades 28 when the flue gas flows, which pushes the rotating blades 28 to rotate around the center line of the hollow rotating shaft 26, thereby driving the distribution pipe 23 to rotate, so that the rotation speed of the distribution pipe 23 can be increased, and the uniformity of the mixing of the ammonia gas and the flue gas can be improved. When the gas flows downward through the cyclone blades 25 on the branch pipe 22, the flow direction of the gas becomes rotating around the branch pipe 22, which strengthens the mixing degree of the flue gas and the ammonia gas in the longitudinal direction and the mixing degree of the flue gas between adjacent distribution pipes 23, and further improves the uniformity of the distribution of the ammonia gas in the flue gas, thereby shortening the distance required for the uniform mixing of the ammonia gas or ammonia-air mixture and the flue gas.

[0059] Experiments prove that the ammonia injection mixing units of the two embodiments can meet the following requirements: the pressure drop of the ammonia injection mixing unit is less than 100 Pa; the NOx content in the flue gas after denitrification is less than 30 mg / Nm3; and the NH3 slip is less than 3 mg / Nm3. x <30mg / Nm 3 The ammonia injection mixing unit of the present application has a simple structure, can be mass-produced in a modular manner, and effectively reduces the production and installation costs.

[0060] As shown in Figure 7 , the present application also provides a denitrification system using the aforementioned ammonia injection mixing unit, which is suitable for flue gas denitrification without dust or with low dust content. The flue 10 is provided with a denitrification unit 30, the denitrification unit 30 is provided with a denitrification catalyst bed 31 (the present application preferably uses two layers of denitrification catalyst), and the ammonia injection mixing unit 20 of the present application is arranged upstream of the denitrification unit 30 in the flue 10. The flue gas is first mixed with ammonia gas or ammonia-air mixture by the ammonia injection mixing unit 20, and then enters the denitrification catalyst bed for further denitrification treatment. The main pipe 21 of the ammonia injection mixing unit 20 is supplied with gas through the ammonia injection main pipe 41 outside the flue 10.

[0061] Further as Figure 8As shown, the extension pipeline of each mother pipe 21 of the ammonia injection mixing unit is provided with a flow meter and a flow regulating valve. Specifically, the three mother pipes 21 of the ammonia injection mixing unit 20 are provided with a first flow meter 46, and the ammonia injection main pipe 41 is provided with a second flow meter 47. The three mother pipes 21 of the ammonia injection mixing unit 20 are provided with a first flow regulating valve 44, and the ammonia injection main pipe 41 is provided with a second flow regulating valve 45. The ammonia injection main pipe 41 is provided with an ammonia-air mixer 42, which is connected with the dilution air pipeline 43, for mixing the ammonia gas with the dilution air, so that the ammonia concentration in the ammonia-air mixed gas injected into the flue 10 is far away from the explosion limit. By independently controlling the flow of the mother pipe 21 and the dilution of the ammonia gas, the system can control the uniform mixing degree of the ammonia gas and the flue gas in the flue 10 according to the site needs, while ensuring the safety of the system.

[0062] Further as Figure 9 shown, preferably but not limitedly, the dilution air pipeline 43 can include a dilution air main pipe 43A and dilution air branch pipes 43B. Among them, the dilution air main pipe 43A is used to dilute the ammonia concentration to below the explosion limit; the number of dilution air branch pipes 43B is the same as that of the mother pipes 21, and each dilution air branch pipe 43B is controlled by a valve. When it is detected that there is flue gas flowing through the flue 10, the valve is in an open state, ensuring that the ammonia injection orifice is always gas spouting. In other words, as long as there is flue gas flowing through the flue 10, the valve on the dilution air branch pipe 43B is in an open state, so that the ammonia injection orifice 24 always has gas spouting, ensuring that the distribution pipe 23 can rotate normally under any working condition, and further ensuring the uniform mixing degree of the ammonia gas and the flue gas.

[0063] Example 1

[0064] As Figures 1 to 3 shown, the ammonia injection mixing unit 20 of the embodiment includes 7 mother pipes 21, each of which is connected with 5 branch pipes 22 arranged vertically thereto, the distal end (the end away from the mother pipe 21) of the branch pipe 22 is fixed with a bearing 27; one end of the hollow rotating shaft 26 communicates with the branch pipe 22 through the bearing 27, and the other end is provided with 4 distribution pipes 23, which are located in the same plane and uniformly distributed on the circumference centering on the hollow rotating shaft 26. The side of each distribution pipe 23 facing the mother pipe 21 is provided with 9 ammonia injection orifices 24, which have an included angle α of 45° with the vertical direction. The middle part of the branch pipe 22 is provided with 4 spiral cyclone vanes 25.

[0065] Referring to Figures 7 to 8 shown, the SCR flue gas denitrification system of the embodiment adopts Figures 1 to 3The ammonia injection mixing unit 20 shown; 7 mother pipes 21 of the ammonia injection mixing unit 20 communicate with the ammonia injection main pipe 41, each mother pipe 21 is provided with a first flow meter 46 and a first flow regulating valve 44, the ammonia injection main pipe 41 is provided with a second flow meter 47 and a second flow regulating valve 45, the ammonia injection main pipe 41 is provided with an ammonia-air mixer 42, and the ammonia-air mixer 42 is connected with the dilution air pipe line 43; downstream of the ammonia injection mixing unit 20 in the direction of the flue gas flow, the denitration unit 30 is arranged, and two layers of denitration catalyst beds 31 are arranged in the denitration unit 30.

[0066] The installation height required by the ammonia injection mixing unit of the embodiment is only 0.8 m, which is greatly reduced compared with the installation height of 2.0 m required by other conventional ammonia injection mixing systems; the system pressure drop of the ammonia injection mixing unit of the embodiment is <100 Pa, which is much lower than the system pressure drop of 200-300 Pa of conventional ammonia injection mixing equipment; the mixing effect of ammonia and flue gas is good, the NOx content in the flue gas after denitration is <30 mg / Nm x <30mg / Nm 3 , and the ammonia escape is <1 mg / Nm 3 .

[0067] Example 2

[0068] As shown in Figures 4 to 6 , the ammonia injection mixing unit of the embodiment includes 3 mother pipes 21, each of which is connected with 12 branch pipes 22 arranged vertically thereto, 4 of which directly communicate with the mother pipe 21, and the remaining 8 branch pipes 22 communicate with the mother pipe 21 through a straight pipe segment arranged vertically thereto. The distal end (the end away from the mother pipe 21) of the branch pipe 22 is fixed with a bearing 27; one end of the hollow rotating shaft 26 communicates with the branch pipe 22 through the bearing 27, and the other end is closed, and two layers of distribution pipes 23 are arranged thereon, each of which communicates with the hollow rotating shaft 26 and is composed of 10 distribution pipes 23, which are uniformly distributed on the same plane and on the circumference centering on the hollow rotating shaft 26, and the two layers of distribution pipes 23 are arranged staggered in the direction of the flue gas flow. Each distribution pipe 23 is provided with 8 ammonia injection holes 24 on the side facing the mother pipe 21, and the ammonia injection holes 24 have a certain angle α with the vertical direction, and α is 60°. A rotating vane 28 is arranged above the distribution pipe 23, and the rotating vane 28 is fixed on the hollow rotating shaft 26, and the rotating vane 28 is arranged obliquely, and the oblique direction is the same as the opening direction of the ammonia injection hole 24, and the angle β between the rotating vane 28 and the vertical direction is also 60°. Four spiral cyclone vanes 25 are arranged near the middle of the branch pipe 22.

[0069] The installation height required by the ammonia injection mixing system of the flue gas denitration device of the certain gas power furnace is 2.0 m, the installation height required by the ammonia injection mixing unit of the embodiment is only 1.2 m, the installation height is greatly reduced; the system pressure drop of the ammonia injection mixing unit of the embodiment is less than 100 Pa, which is much lower than 200-300 Pa of the conventional ammonia injection mixing system; the ammonia gas and the flue gas are well mixed, the NOx after denitration is less than 25 mg / Nm x <25mg / Nm 3 , and the ammonia escape is not detected.

[0070] The foregoing description of specific exemplary embodiments of the application is intended to be illustrative only and is not intended to limit the application to the precise forms described. Many modifications and variations are possible in light of the above teachings without departing from the spirit or essential characteristics of the application. The exemplary embodiments were chosen and described in order to explain the principles of the application and its practical application and to allow others skilled in the art to understand the application for various exemplary embodiments with various modifications as are suited to the particular use contemplated. Any simple modifications, equivalent changes, and modifications based on the exemplary embodiments described above are intended to fall within the scope of the application.

Claims

1. An ammonia mixing unit, characterized in that, Applied to dust-free flue gas denitrification systems and installed in flue ducts, including: The main pipe is laid out in the flue in a direction perpendicular to the flue gas flow direction and is used to introduce ammonia or ammonia-air mixture. There are multiple branch pipes, which are connected to the main pipe and extend along the flue gas direction; a bearing is fitted on the free end of the branch pipe, one end of the bearing is fixedly connected to the branch pipe, and the other end is connected to a hollow rotating shaft, which is connected to the branch pipe. A distribution pipe is disposed on the hollow rotating shaft and is in a connected state. The distribution pipe is evenly distributed circumferentially along the hollow rotating shaft. The distribution pipe is provided with multiple ammonia injection holes whose injection direction is at a certain angle to the flue gas flow direction. Swirl blades, which are fixedly connected to the middle of the branch pipe in the flue, are used to convert the axial airflow into a radial rotating airflow during the mixing of flue gas and ammonia.

2. The ammonia mixing unit according to claim 1, characterized in that, The swirl blades adopt a curved surface structure corresponding to the position of the ammonia injection hole, and the curved surface structure guides the axial airflow into a radial rotating airflow.

3. The ammonia mixing unit according to claim 2, characterized in that, The angle between the opening direction of the ammonia injection hole and the flue gas flow direction is 15-75°.

4. The ammonia mixing unit according to claim 1, characterized in that, The distribution pipes consist of four pipes arranged in a cross shape.

5. The ammonia mixing unit according to claim 4, characterized in that, The distribution pipe is arranged in multiple layers, with each layer of distribution pipes evenly distributed on a circumference centered on the hollow rotation axis; the projections of each layer of distribution pipes on the cross-section of the flue do not overlap.

6. The ammonia mixing unit according to claim 5, characterized in that, The distribution pipe is provided in two layers, and the projections of the two layers of distribution pipes on the cross-section of the flue are arranged at uniform intervals.

7. The ammonia mixing unit according to claim 1, characterized in that, A rotating plate is provided above the distribution pipe. The rotating plate is fixedly connected to the top of the hollow rotating shaft. When the ammonia injection volume is small and cannot drive the distribution pipe to rotate, the rotating plate is driven to rotate by the flue gas, thereby driving the distribution pipe to rotate.

8. The ammonia mixing unit according to claim 1, characterized in that, The number of main pipes is multiple and they are evenly spaced in the flue, or the main pipes extend into multiple rows through connecting pipes; the overall structure consisting of multiple main pipes, multiple branch pipes on each main pipe or connecting pipe, and multiple distribution pipes on each branch pipe forms a complete coverage of the flue cross-section.

9. The ammonia mixing unit according to claim 8, characterized in that, The installation height of the overall structure is 0.7 meters to 1.2 meters.

10. The ammonia mixing unit according to claim 1, characterized in that, The system pressure drop using the aforementioned ammonia injection mixing unit is <100 Pa; NO in the denitrified flue gas is <100 Pa. x <30mg / Nm 3 .

11. A denitrification system, characterized in that, Suitable for dust-free flue gas denitrification, including the ammonia injection mixing unit as described in any one of claims 1 to 10.

12. The denitrification system according to claim 11, characterized in that, The ammonia injection mixing unit is located upstream of the denitrification unit in the flue.

13. The denitrification system according to claim 12, characterized in that, Each main pipe extension of the ammonia mixing unit is equipped with a flow meter and a flow regulating valve.

14. The denitrification system according to claim 13, characterized in that, The air source for each main pipe is provided by the ammonia injection main pipe, which is equipped with an ammonia-air mixer that supplies air through a dilution air duct.

15. The denitrification system according to claim 14, characterized in that, The dilution air duct includes: The dilution air main is used to dilute the ammonia concentration to below the explosion limit; The number of dilution air branch pipes is the same as that of the main pipe, and each dilution air branch pipe is controlled by a valve. When flue gas is detected flowing through the flue, the valve is in the open state to ensure that gas is always ejected from the ammonia injection port.

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