A device and method for fly ash removal from flue gas

Abstract

The present application relates to the field of SCR denitration, and particularly relates to a device and method for removing fly ash in flue gas; the device for removing fly ash in flue gas comprises at least one set of removal units, the removal unit comprises a module and a plurality of groups of guide vanes and a fly ash collecting device arranged in the module, wherein the guide directions of each group of guide vanes are the same; the present application can guide the flue gas by using the guide vanes arranged, the high-temperature flue gas is guided to flow, the flue gas and the coarse particle fly ash carried therein form a high-efficiency cyclone effect in the device, the flue gas mixing is intensified, under the action of the strong centrifugal force generated by the cyclone, the large-particle fly ash moves to the edge of the device, and finally enters the fly ash collecting groove of the device, the deposited fly ash falls into the fly ash falling pipe by gravity, and continuous and efficient collection is realized, so that the content of large-particle fly ash entering the SCR denitration area is effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of SCR denitrification, specifically to a fly ash removal device and method in flue gas. Background Technology

[0002] SCR denitrification refers to a NOx emission reduction technology in which, within a certain temperature range, a reducing agent (such as liquid ammonia, urea, and ammonia water) reacts selectively with NOx in flue gas under the action of a catalyst to generate pollution-free N2 and H2O.

[0003] SCR (Selective Catalytic Reduction) denitrification technology is currently the main technology for achieving ultra-low nitrogen oxide emission standards in power plant boilers. Currently, most SCR denitrification reactors are located between the boiler economizer and air preheater, making them prone to operation in a high-dust flue gas environment. Firstly, if the flue gas contains a high ash content, fly ash will deposit between the ammonia injection grid pipes, clogging the nozzles and affecting the uniformity of ammonia injection. Secondly, alkali metals such as calcium in the fly ash can cause chemical deactivation of the catalyst. The fly ash particles, after reacting with SO3, easily clog the catalyst micropores. Furthermore, if the denitrification catalyst is subjected to high-ash-concentration flue gas for a prolonged period, surface interface wear and even module collapse can occur, leading to reduced denitrification performance and shortened service life. Therefore, reducing the fly ash content entering the denitrification reactor is one of the necessary measures to ensure the long-term safe operation of the power plant boiler denitrification system.

[0004] Currently, the main method to reduce the fly ash content entering the denitrification reactor is to install ash collection hoppers and baffles at the bottom of the economizer and the bottom of the denitrification inlet flue, and separate the flue gas and ash particles by inertial force. However, this method has low ash removal efficiency and the structure is relatively complex, requiring a large amount of engineering work for modification during use. Summary of the Invention

[0005] To address the problems mentioned in the prior art, this invention proposes a fly ash removal device and method in flue gas. By setting guide vanes and ash collection troughs, it can achieve the purpose of ash removal in flue gas before SCR denitrification, improve ash removal efficiency, effectively reduce the burden on the SCR catalyst layer, and avoid catalyst wear and blockage caused by fly ash deposition.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The present invention includes at least one set of removal units, wherein the removal unit includes a module and multiple sets of guide vanes and ash collection devices disposed within the module, wherein each set of guide vanes has the same guiding direction, and when the flue gas containing fly ash is guided by the guide vanes, the fly ash in the flue gas enters the ash collection device and is removed.

[0008] As a further improvement of the present invention, the module is composed of a plurality of wall panels connected in sequence.

[0009] As a further improvement of the present invention, the guide vane includes a connected oblique guide plate and a longitudinal guide plate, wherein the surface of the oblique guide plate is perpendicular to the wall plate, the surface of the longitudinal guide plate is perpendicular to the cross-section of the module, and the surface of the oblique guide plate and the surface of the longitudinal guide plate intersect to form the guide vane.

[0010] As a further improvement of the present invention, the included angle between the inclined guide plate and the cross-section of the module is 30° to 45°.

[0011] As a further improvement of the present invention, the ash collection device includes multiple sets of ash collection troughs, which are U-shaped troughs. The ash collection troughs are located at the four corners of the module, and each ash collection trough is connected to a top plate. The bottom of the ash collection trough is connected to the ash discharge pipe.

[0012] As a further improvement of the present invention, the width of the ash collection trough is 150-200mm and the depth is 200-300mm, wherein the width of the ash collection trough is greater than the depth of the ash collection trough.

[0013] As a further improvement to the present invention, the module height is 1.5 to 2m.

[0014] As a further improvement of the present invention, the flow directions of each adjacent set of removal units are opposite.

[0015] As a further improvement of the present invention, this device is installed in the vertical flue at the inlet of the SCR denitrification device.

[0016] A method for removing fly ash from flue gas involves the following steps: When flue gas containing fly ash enters the device from bottom to top, it is guided by guide vanes and the flue gas and fly ash generate swirling flow within the module, which intensifies the mixing of the flue gas. The fly ash is then subjected to centrifugal force and flows towards the wall plate, entering the ash collection trough in the ash collection structure and falling into the ash discharge pipe, thereby achieving fly ash collection and removal.

[0017] Compared with the prior art, the present invention achieves the following technical effects:

[0018] The fly ash removal device of this invention is installed in the vertical flue at the inlet of the SCR denitrification device. The guide vanes can guide the flue gas. By guiding the flow of high-temperature flue gas, the flue gas and the coarse fly ash particles carried therein form an efficient swirling effect inside the device, which intensifies the mixing of flue gas. Under the strong centrifugal force generated by the swirling, the large fly ash particles move towards the edge of the device and eventually enter the ash collection tank of the device. The deposited fly ash will fall into the ash collection pipe by gravity, achieving continuous and efficient collection, thereby effectively reducing the content of large particulate matter entering the SCR denitrification zone.

[0019] This invention significantly improves the removal efficiency of coarse fly ash in flue gas, effectively reduces the burden on the SCR catalyst layer, and avoids catalyst wear and blockage caused by fly ash deposition, thereby improving the overall denitrification performance and catalyst lifespan. In addition, this device intensifies flue gas mixing, which helps to improve the uniformity of component concentration field before denitrification, thereby improving the operating conditions of the SCR denitrification device. This device has a simple structure, has little impact on the original flue structure, requires little installation space, is suitable for retrofit projects, and has low retrofit costs.

[0020] This invention can effectively reduce the amount of fly ash entering the SCR stage, which not only protects the catalyst but also indirectly improves the overall energy efficiency ratio of the system and reduces the energy consumption and cost caused by frequent cleaning of the catalyst layer. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of a fly ash removal device in flue gas according to the present invention;

[0022] Figure 2 This is a top view of the overall structure of a fly ash removal device in flue gas according to the present invention;

[0023] Figure 3 This is a top view of the fly ash removal unit structure of a fly ash removal device for flue gas according to the present invention;

[0024] Figure 4 This is a schematic diagram of the guide vane structure of a fly ash removal device in flue gas according to the present invention;

[0025] Figure 5 This is another schematic diagram of the guide vane structure of a fly ash removal device in flue gas according to the present invention;

[0026] Figure 6 This is a schematic diagram showing the arrangement of multiple removal units in a fly ash removal device for flue gas according to the present invention.

[0027] Reference numerals in the attached drawings: 1. Wall panel; 2. Guide vane; 3. Top plate; 4. Ash collection trough; 5. Ash drop pipe. Detailed Implementation

[0028] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0029] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0031] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0032] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0033] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0034] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0035] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0036] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0037] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0038] like Figures 1-6 As shown, the present invention provides a fly ash removal device for flue gas, comprising at least one set of removal units. Each removal unit includes a module and multiple sets of guide vanes 2 and a ash collection device disposed within the module. Each set of guide vanes 2 has the same guiding direction. When the flue gas containing fly ash passes through the guide vanes 2, the fly ash in the flue gas enters the ash collection device and is removed.

[0039] The module consists of multiple wall panels 1 connected in sequence. Example implementation: Figure 1 and Figure 2 As shown, the module is formed by four sequentially connected wall panels 1. An inner cavity is located in the middle of the module, and guide vanes 2 and a dust collection device are installed within the inner cavity; as shown... Figure 2 As shown, the length and width of the module are L and W, respectively. The specific length and width of the module are determined according to the actual dimensions of the vertical flue installed. The dimensions of each module are obtained by dividing the actual dimensions into several equal parts. Generally speaking, the length L and width W of the module can be selected in the range of 0.4 to 0.8 m.

[0040] The guide vane 2 includes a connected inclined guide plate and a longitudinal guide plate. The inclined guide plate is perpendicular to the wall panel 1, and the longitudinal guide plate is perpendicular to the cross-section of the module. The inclined guide plate and the longitudinal guide plate intersect to form the guide vane 2. The angle between the inclined guide plate and the cross-section of the module is 30° to 45°.

[0041] like Figure 1 , Figure 4 and Figure 5 As shown, in this embodiment, the guide vanes 2 are preferably four connected sets of vanes, each set of guide vanes 2 consisting of connected oblique guide plates and longitudinal guide plates; as Figure 5 As shown, the red one is the oblique guide plate, and the green one is the longitudinal guide plate. The surface of the oblique guide plate is perpendicular to the wall plate 1, and the cutting line formed by the oblique guide plate and the wall plate 1 is AB. The surface of the longitudinal guide plate is perpendicular to the cross-section of the module, and the cutting line formed by the longitudinal guide plate and the cross-section of the module is AO. In this embodiment, O is the midpoint of the cross-section of the module. The surface of the oblique guide plate and the surface of the longitudinal guide plate intersect to form the intersection line AC. The triangles ABC and AOC formed by these intersections constitute a set of guide blades 2. The flow path of the flue gas can be further optimized through the guide blades 2. The oblique guide plate and the longitudinal guide plate form an all-round guidance of the flue gas, realizing the swirling of the flue gas.

[0042] In this embodiment, adjacent guide vanes 2 have the same guiding direction, such as... Figure 3 As shown, in this embodiment, the four sets of guide vanes 2 are designed to have the same guiding direction, that is, to act together on the flue gas to generate a clockwise swirling flow. The tangential velocity of the swirling flow is mainly related to the incoming flow velocity and the guiding velocity X. The incoming flow velocity refers to the initial velocity of the flue gas before entering the guiding area, while the guiding velocity X is the angle formed between the cutting line AB and the bottom edge of the wall plate 1. In order to obtain the best swirling effect and fly ash separation performance, X is preferably set in the range of 30 to 45°. Through experimental simulation analysis, the X value in this range can effectively guide the flue gas to generate a high-intensity clockwise swirling flow, while reducing energy loss and eddy turbulence, thereby optimizing the distribution and deposition process of fly ash particles in the swirling flow field.

[0043] The ash collection device includes multiple sets of ash collection troughs 4, each trough being U-shaped. The troughs 4 are located at the four corners of the wall panel 1, and each trough 4 is connected to a top plate 3. Each trough 4 is connected to an ash discharge pipe 5. The width of the ash collection trough 4 is 150–200 mm, and its depth is 200–300 mm, with the width exceeding the depth. Figure 1 and Figure 2 As shown, in this embodiment, four sets of identical ash collection devices are preferably provided, each set located at one corner of the module; the ash collection trough 4 is a U-shaped trough structure, specifically a semi-open trough. The ash collection trough 4 includes an ash collecting baffle, and the semi-open trough formed between the ash collecting baffle and the wall panel 1 is the ash collection trough 4, wherein the opening direction of the trough is opposite to the flue gas swirl direction, such as... Figure 3 As shown, when the flue gas rotates clockwise under the action of the guide vane 2, the large particles of fly ash formed during the rotation process enter the ash collection trough 4 to achieve the collection of large particles of fly ash.

[0044] In the embodiments, to ensure the effectiveness of fly ash collection, such as Figure 2 As shown, the width m and depth n of the ash collection trough 4 of the present invention have been optimized through experiments to ensure its efficient operation and long-term stability. The preferred width m is 150-200 mm and the depth n is 200-300 mm. The width m is larger than the depth n, which ensures that when fly ash particles are subjected to the centrifugal force generated by the swirling flow, they can fully diffuse to both sides of the device and fall smoothly into the preset ash collection trough 4. This effectively avoids the retention and recirculation of fly ash inside the device, thereby significantly improving the efficiency and effect of coarse ash removal.

[0045] In this embodiment, the ash collection trough 4 is provided with a top plate 3, which is used to seal the top of the ash collection trough 4, thereby preventing the flue gas in the ash collection trough 4 from carrying away the collected fly ash particles while flowing upward. The bottom of the ash collection trough 4 is connected to an ash discharge pipe 5, which is connected to the ash collection trough 4. The bottom of the ash discharge pipe 5 is connected to an ash conveying pipe or ash hopper. When fly ash falls into the ash discharge pipe 5, it will be transported to other suitable locations through the connected ash conveying pipe or ash hopper to achieve the collection and removal of large fly ash particles.

[0046] In this embodiment, to ensure the guiding effect of the guide vane 2, a certain distance needs to be maintained between the guide vane 2 and the ash collection trough 4, such as... Figure 2 As shown in the figure, a is the interval distance between one of the ash collection troughs 4 and the guide vane 2, and b is the interval distance between the other ash collection trough 4 and the guide vane 2. In the preferred embodiment, the difference between a and m (width of ash collection trough 4) and the difference between b and m should be not less than 100mm. This is to reduce the mutual interference and accumulation of fly ash during the flow process and ensure that fly ash can fall into the ash collection trough 4. By controlling the interval distance, not only is the guiding effect of the guide vane 2 improved, but the collection path of fly ash is also optimized, effectively reducing the risk of fly ash escape and recycling.

[0047] In this embodiment, considering that the flue gas rises from bottom to top, the dynamic changes of the swirling effect during the flue gas's ascent are taken into account. When the flue gas passes through the guide vane 2, a swirling flow is generated. As the flue gas continues to rise, the intensity of the swirling flow will inevitably be affected by various factors and gradually decrease, including the viscous dissipation of the flue gas, friction with the flue wall, and turbulent diffusion. In order to ensure that most of the fly ash can be collected before the swirling flow weakens to an insignificant level, the height of the module in this embodiment is preferably 1.5 to 2 m. Experiments have shown that after the flue gas forms a swirling flow through the guide vane 2, the swirling flow can effectively guide the fly ash to the ash collection trough 4 area before its intensity significantly decreases, and complete the collection of fly ash.

[0048] The flow directions of adjacent removal units are opposite. In the embodiment, for example... Figure 6As shown, multiple removal units are arranged closely and evenly on the vertical flue section. The figure shows four removal units connected in sequence. In order to ensure that the flue gas entering the downstream is mixed more fully and the flow velocity distribution is more uniform, the swirling directions of adjacent removal units in this embodiment are opposite. Of course, the number of removal units can be changed according to the specific application scenario and requirements. Here, the number of removal units is not limited.

[0049] This device is installed in the vertical flue at the inlet of the SCR denitrification unit. In this embodiment, the device is specifically installed in the inlet area of ​​the SCR denitrification unit, within the vertical flue and after the ammonia injection grid. Its purpose is to pretreat the flue gas before it enters the SCR catalyst layer, effectively removing coarse fly ash particles from the flue gas. This reduces potential adverse effects on the subsequent denitrification process and the catalyst layer, ensuring that most of the coarse fly ash particles in the flue gas are effectively removed before the ammonia and flue gas are fully mixed. This avoids interference from fly ash with the ammonia injection effect and potential ammonia escape problems.

[0050] When this device is in use, when large fly ash particles enter the vertical flue of the SCR denitrification inlet from bottom to top, upon reaching this device, the flue gas is guided by the guide vanes 2, causing the flue gas to rotate. During the rotation, the flue gas and the coarse fly ash particles it carries form a highly efficient swirling effect inside the device, intensifying the mixing of the flue gas. At the same time, the large fly ash particles flow towards the wall plate 1 under the action of centrifugal force. During the flow, they enter the ash collection trough 4 and fall under the action of gravity, falling into the ash discharge pipe 5 and being discharged by the connected ash hopper.

[0051] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0052] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A fly ash removal device for flue gas, characterized in that, It includes at least one set of removal units, each set of removal units including a module and multiple sets of guide vanes and ash collection devices disposed within the module, wherein each set of guide vanes has the same guiding direction. When the flue gas containing fly ash passes through the guide vanes, the fly ash in the flue gas enters the ash collection device and is removed. The module consists of multiple wall panels connected in sequence; The guide vanes include connected inclined guide vanes and longitudinal guide vanes. The surface of the inclined guide vanes is perpendicular to the wall panel, and the cutting line formed by the inclined guide vanes and the wall panel is AB. The surface of the longitudinal guide vanes is perpendicular to the cross-section of the module, and the cutting line formed by the longitudinal guide vanes and the cross-section of the module is AO. O is the midpoint of the cross-section of the module. The surface of the inclined guide vanes intersects the surface of the longitudinal guide vanes to form an intersection line AC. The triangles ABC and AOC formed by these intersections constitute a set of guide vanes. The angle between the inclined guide vane and the cross-section of the module is 30° to 45°. The ash collection device includes multiple sets of ash collection troughs, which are U-shaped troughs. The ash collection troughs are located at the four corners of the module, and each ash collection trough is connected to a top plate. The bottom of the ash collection trough is connected to the ash drop pipe.

2. The fly ash removal device in flue gas according to claim 1, characterized in that, The width of the ash collection trough is 150-200mm and the depth is 200-300mm, wherein the width of the ash collection trough is greater than the depth of the ash collection trough.

3. The fly ash removal device in flue gas according to claim 1, characterized in that, The module height is 1.5 to 2 meters.

4. The fly ash removal device in flue gas according to claim 1, characterized in that, The flow direction of each adjacent set of removal units is opposite.

5. The fly ash removal device in flue gas according to claim 1, characterized in that, This device is located in the vertical flue at the inlet of the SCR denitrification unit.

6. The method of using the fly ash removal device in flue gas according to any one of claims 1 to 5, characterized in that, When the flue gas containing fly ash enters the device from bottom to top, after being guided by the guide vanes, the flue gas and fly ash generate a swirling flow in the module, which intensifies the mixing of the flue gas. The fly ash flows towards the wall plate under the action of centrifugal force and enters the ash collection trough in the ash collection structure and falls into the ash discharge pipe, thereby realizing the collection and removal of fly ash.

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