Cement kiln flue gas SCR denitration system

Abstract

The invention provides a cement kiln flue gas SCR denitration system which is characterized in that a mixing area and a reaction area are sequentially arranged on a flue gas runner, flue gas in the mixing area flows upwards, and flue gas in the reaction area flows downwards; in the reaction zone, a dispersion layer is arranged at the top end, and a plurality of catalyst layers are arranged below the dispersion layer; the dispersion layer is made of a metal material and is of a honeycomb porous structure, the mixing efficiency of flue gas and ammonia gas is improved by arranging the reverse mixing area and reaction area, and the metal dispersion layer is arranged to realize pre-dispersion before the flue gas is in contact with a catalyst, so that the concentration of solid particles in a local area of the flue gas is reduced, dust is adsorbed in advance, and heating is matched, so that the purification efficiency of the flue gas is improved. Ammonium salt is decomposed in time, the occurrence of later catalyst blockage is slowed down, and the denitration conversion efficiency of the catalyst is improved.

Description

Technical Field

[0001] The invention relates to the field of flue gas treatment, and in particular to a cement kiln flue gas SCR denitrification system. Background Art

[0002] In the treatment of cement kiln flue gas, the selective catalytic reduction technology (SCR) is generally used to denitrate the flue gas. The basic principle is to first mix ammonia with the flue gas, and then under the action of the catalyst, ammonia water or urea reacts with nitrogen oxides to convert them into nitrogen and water vapor. In this way, the denitration operation is completed. However, during the denitration process, the presence of dust particles, sulfur dioxide and alkali metals in the flue gas will lead to the production of ammonium salts on the one hand, and on the other hand, the dust particles will deposit in the small pores of the catalyst, which will hinder the removal of NOx and NH 3 , O 2 When the particles reach the active surface of the catalyst, they will be deactivated and the denitration efficiency will be reduced. In conventional denitration pipelines, the flue gas is directly introduced into the catalyst area. The concentration of particulate matter in the middle of the flue gas is higher than that in other areas. Therefore, it is easy to cause blockage in the middle area of ​​the catalyst, requiring operators to frequently perform cleaning operations. Summary of the invention

[0003] The technical problem to be solved by the present invention is that in the existing flue gas denitrification treatment, the catalyst is easily clogged, manual dust removal is required, and the operation efficiency is low. The present invention provides a cement kiln flue gas SCR denitrification system to solve the above problem.

[0004] The technical solution adopted by the present invention to solve its technical problems is: a cement kiln flue gas SCR denitrification system, in which a mixing zone and a reaction zone are sequentially arranged on the flue gas flow duct, the flue gas flow direction of the mixing zone is upward, and the flue gas flow direction of the reaction zone is downward; in the reaction zone, a dispersion layer is arranged at the top, and a multi-layer catalyst layer is arranged below the dispersion layer; the dispersion layer is made of metal, and the structure is a honeycomb porous structure.

[0005] Furthermore, the mixing zone includes a vertically arranged straight pipe and an ammonia injection grid arranged in the straight pipe, the straight pipe is a uniform cross-section structure, and the ammonia injection grid is connected to an injection device.

[0006] Furthermore: the mixing zone also includes a mixer arranged above the ammonia injection grid.

[0007] Furthermore: a slow flow zone is arranged between the mixing zone and the reaction zone, and the slow flow zone includes a slow flow pipe, and the slow flow pipe is in the shape of an inverted cone-shaped trumpet, a guide plate is arranged on the side of the slow flow pipe near the mixing zone, and a rectifying grid is arranged on the side of the slow flow pipe near the reaction zone; a transverse baffle is arranged on the top tube wall of the slow flow pipe.

[0008] Furthermore: an introduction zone is arranged at the front end of the mixing zone, the introduction zone comprises a transversely arranged introduction pipe, the cross section of the introduction pipe gradually shrinks near the mixing zone, and a guide plate is arranged in the introduction pipe.

[0009] Furthermore: a soot blower is arranged above the dispersion layer, and a resistance heating wire is connected to the dispersion layer.

[0010] The beneficial effect of the present invention is that the cement kiln flue gas SCR denitrification system of the present invention improves the mixing efficiency of flue gas and ammonia by setting up reverse mixing zones and reaction zones, and sets up a metal dispersion layer to achieve pre-dispersion of flue gas before contact with catalyst, thereby reducing the concentration of solid particulate matter in local areas of flue gas, and pre-adsorbing dust, and cooperating with heating to decompose ammonium salts in time, thereby slowing down the occurrence of subsequent catalyst blockage and improving the denitrification conversion efficiency of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0012] Figure 1 It is a structural schematic diagram of a cement kiln flue gas SCR denitrification system of the present invention; Figure 2 yes Figure 1 A partial enlarged view of point A in the figure.

[0013] In the figure, 1, mixing zone, 2, reaction zone, 3, dispersion layer, 4, catalyst layer, 5, straight pipeline, 6, ammonia spray grid, 7, injection device, 8, mixer, 9, slow flow zone, 10, slow flow pipe, 11, guide plate, 12, rectifying grid, 13, transverse baffle, 14, introduction zone, and 15, introduction pipeline. DETAILED DESCRIPTION

[0014] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and are not to be construed as limitations of the present invention. On the contrary, embodiments of the present invention include all changes, modifications and equivalents that fall within the spirit and connotation of the appended claims.

[0015] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0016] In addition, the terms "first", "second", etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance. In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0017] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention belong.

[0018] like Figure 1 , Figure 2 As shown, the present invention provides a cement kiln flue gas SCR denitrification system, in which a mixing zone 1 and a reaction zone 2 are sequentially arranged on the flue gas flow channel, the flue gas flow direction of the mixing zone 1 is upward flow, and the flue gas flow direction in the reaction zone 2 is downward flow; in the reaction zone 2, a dispersion layer 3 is arranged at the top, and a multi-layer catalyst layer 4 is arranged below the dispersion layer 3; the dispersion layer 3 is made of metal, and the structure is a honeycomb porous structure.

[0019] SCR denitrification technology is to first inject ammonia or other suitable reducing agents into the upstream flue gas, and then use a catalyst to convert NOx in the flue gas into nitrogen and water at a temperature of 200-450°C. In this technical solution, mixing zone 1 is the link where ammonia and flue gas are mixed, and reaction zone 2 is the conversion reaction link under the action of the catalyst. The upward flow of flue gas in mixing zone 1 can promote the full mixing of ammonia and flue gas, improve the gas-solid contact efficiency, improve the effect of the subsequent reduction reaction, and increase the denitrification rate. The reaction zone 2 adopts a reverse design, changing the flue gas flow to a downward flow, so that the gravity effect can be used to promote the separation and sedimentation of solid dust, reduce the generation of dust deposition, and reduce the direct impact of fly ash on the dispersion layer 3 and the catalyst layer 4.

[0020] The reaction zone 2 adopts a design in which the upper layer is a dispersion layer 3 and the lower layer is a catalyst layer 4. After reaching the reaction zone 2, the flue gas first contacts the dispersion layer 3. The dispersion layer 3 is a honeycomb porous structure, which has a certain dispersion and rectification effect, and can change the original flue gas state where the smoke dust is concentrated in the middle, and promote the uniform separation of the solid dust content in the flue gas.

[0021] At the same time, since the dispersion layer 3 is made of metal material, this material can be steel, copper or other common metal materials or alloy materials. This material is different from the material of the catalyst layer 4 below. Due to the characteristics of the material, the denitrification catalyst is easy to adsorb dust, which can easily cause dust accumulation and even blockage. However, since the metal surface of the dispersion layer 3 is smoother and less rough, it has less adhesion to solid dust particles. The solid dust in the flue gas can be efficiently diverted after encountering the dispersion layer 3, thereby improving the dispersion efficiency. In addition, the metal dispersion layer 3 is more wear-resistant, and strong cleaning methods can be used to efficiently clean it when it encounters blockage, which is convenient for maintenance.

[0022] In the interval of the dispersion layer 3, the airflow almost forms a static pressure zone, and the solid dust particles are fully dispersed. After passing through the dispersion layer 3, the evenly dispersed flue gas flows to the rear channel, which changes the distribution state of the flue gas on the surface of the catalyst layer 4, reduces the planar concentration of the soot, and thus disperses the solid particles in the flue gas from occupying the catalyst holes. When entering the catalyst layer 4, the flow rate is slowed down, and the catalyst layer 4 and the flue gas can fully contact and react. At the same time, the dust will not accumulate due to excessive concentration in the local area, thereby causing blockage.

[0023] The mixing zone 1 includes a vertically arranged straight pipe 5 and an ammonia spraying grid 6 arranged in the straight pipe 5. The straight pipe 5 is a uniform cross-sectional structure, and the ammonia spraying grid 6 is connected to an injection device 7. Ammonia is uniformly sprayed on the flue gas through the ammonia spraying grid 6, and dynamic mixing of ammonia and flue gas is achieved through flow rate control. The flue gas in the mixing zone 1 flows upward, and a straight pipe 5 with a uniform cross-sectional structure is designed, which can facilitate the formation of a turbulent flow field of the flue gas in the mixing zone 1. Ammonia is sprayed and mixed with the flue gas in a turbulent state, which will improve the mixing effect. The mixed gas forms a uniform flow state, realizing the dynamic mixing of ammonia and flue gas, and ensuring the treatment effect of the subsequent reduction reaction.

[0024] The mixing zone 1 further comprises a flow mixer 8 disposed above the ammonia injection grid 6. The flow mixer 8 may adopt a plurality of flow guiding structures, which can accelerate the diffusion of ammonia through turbulent disturbance, break the laminar flow state of the flue gas, and improve the mixing effect of ammonia and flue gas.

[0025] A slow flow zone 9 is arranged between the mixing zone 1 and the reaction zone 2, and the slow flow zone 9 includes a slow flow pipe 10, and the slow flow pipe 10 is in the shape of an inverted cone-shaped trumpet. A guide plate 11 is arranged on the slow flow pipe 10 near the mixing zone 1 side, and a rectifying grid 12 is arranged on the slow flow pipe 10 near the reaction zone 2 side; a transverse baffle 13 is arranged on the top tube wall of the slow flow pipe 10.

[0026] The flue gas flow velocity is gradually reduced through the slow flow pipe 10, and the guide plate 11 and the rectifying grid 12 cooperate to eliminate eddy currents and even out the airflow distribution. The slow flow pipe 10 is in the shape of an inverted cone, which can disperse the impact of the flue gas center airflow and reduce the flow resistance. The rectifying grid 12 evenly distributes and guides the slow flue gas, which is convenient for the reduction reaction in the subsequent reaction zone 2. Because the flue gas in the mixing zone 1 and the reaction zone 2 flows in opposite directions, the slow flow zone 9 can be used to achieve slowing down and flue gas reversal. The transverse baffle 13 can also guide the transversely flowing flue gas to a downward flowing state, which is convenient for the flow of flue gas in the reaction zone 2.

[0027] An introduction area 14 is disposed at the front end of the mixing area 1 . The introduction area 14 includes a transversely disposed introduction pipe 15 . The cross section of the introduction pipe 15 gradually shrinks toward the mixing area 1 . A guide plate 11 is disposed in the introduction pipe 15 .

[0028] The guide plate 11 disposed in the inlet pipe 15 is mostly of spiral design, and the tapered pipe and the guide plate 11 can generate a swirl flow, adjust the initial state of the smoke entering the mixing zone 1, speed up the initial flow rate of the smoke, and enhance the disturbance effect of the mixing zone 1. At the same time, the guide plate 11 pre-disperses the smoke and dust to reduce the wear of large particles on subsequent devices.

[0029] A soot blower is arranged above the dispersion layer 3, and a resistance heating wire is connected to the dispersion layer 3. The soot blower adopts sonic soot blowing or rake soot blowing, etc., which is a common way to deal with catalyst blockage in the prior art, so the specific structure and installation method are not described in detail.

[0030] In the temperature range of 200-210℃, the catalyst activity is low and the dosage is large for denitration. This temperature range is the best temperature range for ammonium sulfate generation. SO3 in the flue gas reacts with NH3 to generate ammonium sulfate byproduct, which is easy to block the catalyst and cause catalyst deactivation. In addition, ammonium sulfate is very viscous and difficult to blow off with a soot blower. The metal dispersion layer 3 is heated by a resistance heating wire in the dispersion layer 3. The surface temperature of the dispersion layer 3 can be adjusted regularly. Periodic heating inhibits the generation of ammonium sulfate, decomposes and decomposes the generated ammonium sulfate, solves the problem of catalyst passivation, ensures the conversion efficiency of the catalyst and reduces the occurrence of catalyst blockage.

[0031] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0032] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A cement kiln flue gas SCR denitrification system, characterized by: A mixing zone (1) and a reaction zone (2) are sequentially arranged on the flue gas flow passage, the flue gas in the mixing zone (1) flows upward, and the flue gas in the reaction zone (2) flows downward; In the reaction zone (2), a dispersion layer (3) is arranged at the top, and a multi-layer catalyst layer (4) is arranged below the dispersion layer (3); the dispersion layer (3) is made of metal and has a honeycomb porous structure.

2. A cement kiln flue gas SCR denitrification system as claimed in claim 1, characterized in that: The mixing zone (1) comprises a vertically arranged straight pipeline (5) and an ammonia injection grid (6) arranged in the straight pipeline (5); the straight pipeline (5) is a uniform cross-sectional structure; and the ammonia injection grid (6) is connected to an injection device (7).

3. A cement kiln flue gas SCR denitrification system as claimed in claim 2, characterized in that: The mixing zone (1) further comprises a flow mixer (8) arranged above the ammonia injection grid (6).

4. A cement kiln flue gas SCR denitrification system as claimed in claim 3, characterized in that: A slow flow zone (9) is provided between the mixing zone (1) and the reaction zone (2); the slow flow zone (9) comprises a slow flow tube (10); the slow flow tube (10) is in the shape of an inverted cone-shaped trumpet; a guide plate (11) is provided on the slow flow tube (10) near the mixing zone (1); a rectifying grid (12) is provided on the slow flow tube (10) near the reaction zone (2); and a transverse baffle (13) is provided on the top tube wall of the slow flow tube (10).

5. A cement kiln flue gas SCR denitrification system as claimed in claim 4, characterized in that: An introduction zone (14) is provided at the front end of the mixing zone (1), the introduction zone (14) comprising a transversely arranged introduction pipe (15), the cross section of the introduction pipe (15) gradually shrinks towards the mixing zone (1), and a guide plate (11) is provided in the introduction pipe (15).

6. A cement kiln flue gas SCR denitrification system as claimed in claim 5, characterized in that: A soot blower is arranged above the dispersion layer (3), and a resistance heating wire is connected to the dispersion layer (3).

Images