An ammonia process desulfurization system with reduced ammonia slip

Abstract

The utility model provides a kind of ammonia escape reduction's ammonia desulfurization system, including absorption tower, the liquid storage tank is sequentially equipped with 4 layers of spray layer, 2 layers of demisting layer from bottom to top in absorption tower, and its outside is equipped with circulating tank, the circulating tank is equipped with several spray pipes and is connected to each layer of spray layer;The reflux pipe is connected to the circulating tank and is equipped on the absorption tower;The circulating pipe is connected to the circulating tank and is equipped in the liquid storage tank;The spray layer and the demisting layer are evenly arranged with several evenly distributed nozzles, and the nozzle is tangential type conical structure.The utility model solves the problem of ammonia escape completely by double means of space optimization spray layer and demisting layer layout.

Description

Technical Field

[0001] This utility model relates to the technical field of flue gas purification equipment, specifically to an ammonia desulfurization system that reduces ammonia escape. Background Technology

[0002] The principle of ammonia-based desulfurization technology is to react ammonia (NH3) with sulfur dioxide (SO2) in flue gas to produce desulfurization products such as ammonium sulfite or ammonium sulfate. This technology boasts advantages such as rapid reaction rate, high desulfurization efficiency (95%-99%), and the byproduct ammonium sulfate can be utilized as nitrogen fertilizer. However, in practical applications, ammonia-based desulfurization systems generally face a series of technical bottlenecks, including high desulfurizing agent consumption, difficulty in aerosol elimination, slow oxidation of ammonium sulfite, and difficulty in ammonium sulfate crystallization. Among these, ammonia escape is particularly prominent and has become a key obstacle restricting the widespread adoption of this technology.

[0003] Ammonia escape refers to the phenomenon of unreacted ammonia gas escaping from the desulfurization system in gaseous form. It mainly stems from improper control of reaction conditions and equipment design defects.

[0004] 1. Uncontrolled reaction conditions: When the ammonia supply exceeds the stoichiometric ratio required for the desulfurization reaction, the excess ammonia is prone to volatilization; an excessively high pH in the absorption tower will enhance the alkaline environment and accelerate the volatilization of ammonia; in addition, an increase in the temperature of the absorption liquid will reduce the solubility of ammonia, causing ammonia to escape from the liquid phase to the gas phase.

[0005] 2. Equipment structural defects: Poor atomization effect of the spray system leads to insufficient contact between ammonia and flue gas, and unreacted ammonia escapes directly; low efficiency of the demister makes it unable to effectively capture ammonia-containing droplets, causing ammonia to be discharged with the flue gas.

[0006] A series of subsequent problems caused by ammonia escape include: the escaped ammonia reacts with sulfur trioxide and water in the flue gas to produce highly corrosive substances such as ammonium bisulfate, which adhere to the surface of flue ducts and chimneys, significantly shortening equipment lifespan; ammonia, as a malodorous substance, will worsen air quality and irritate the human respiratory tract and eyes when released into the atmosphere, harming health; ammonia escape directly leads to the waste of desulfurizing agents, increasing raw material consumption costs; at the same time, equipment corrosion problems increase maintenance and replacement costs and may lead to system failure and shutdown; excessive ammonia escape inhibits the desulfurization reaction in the absorption tower, reducing desulfurization efficiency and making it difficult to meet environmental emission standards.

[0007] Therefore, there is an urgent need for a simple and efficient solution to reduce ammonia escape in ammonia desulfurization systems. Utility Model Content

[0008] The purpose of this invention is to provide an ammonia desulfurization system that reduces ammonia escape. By optimizing the layout of the spray layer and the demister layer, the problem of ammonia escape can be completely solved.

[0009] To achieve the above objectives, the present invention proposes the following technical solution:

[0010] An ammonia desulfurization system for reducing ammonia escape includes an absorption tower, wherein the absorption tower is provided with a liquid storage tank, four spray layers, and two demister layers from bottom to top, and a circulation tank is provided on the outside.

[0011] The circulation tank is equipped with several spray pipes connected to each of the spray layers;

[0012] The absorption tower is equipped with a reflux pipe that connects to the circulation tank;

[0013] The liquid storage tank is provided with a circulation pipe connected to the circulation tank;

[0014] Both the spray layer and the demisting layer are provided with a number of evenly distributed nozzles, and the nozzles are in the form of tangential conical structures.

[0015] As a preferred technical solution of this utility model, a first concentration layer is provided in the absorption tower between the liquid storage tank and the lowest spray layer, and the first concentration layer is located above the air inlet of the absorption tower.

[0016] The circulation tank is equipped with a first concentration pipe that connects to the first concentration layer.

[0017] As a preferred technical solution of this utility model, a second concentration layer is provided between the first concentration layer and the lowest spray layer;

[0018] The storage tank is equipped with several second concentration pipes that connect to the second concentration layer.

[0019] As a preferred embodiment of this utility model, at least two return pipes are provided, with at least one return pipe located below the lowest spray layer and at least one return pipe located between the second and third spray layers.

[0020] As a preferred embodiment of this utility model, the included angle between the axes of adjacent nozzles in the same spray layer is 30°-60°, and the projections of the nozzles in adjacent spray layers are distributed in an interlaced grid pattern.

[0021] As a preferred embodiment of this invention, the vertical spacing between adjacent spray layers increases progressively from top to bottom.

[0022] As a preferred embodiment of this utility model, the nozzle spray direction of the demisting layer is at an angle opposite to the flue gas flow direction, and the nozzle angle of the lower demisting layer is 20°-30°, while the nozzle angle of the upper demisting layer is 40°-50°.

[0023] As can be seen from the above technical solutions, the present invention provides an ammonia desulfurization system that reduces ammonia slip, and has the following advantages compared with the prior art:

[0024] 1. Improve absorption efficiency and reduce ammonia escape at the source:

[0025] Increasing the number of spray layers to four increases the contact time and area between the spray layer and the absorbent liquid. The multiple spray layers allow for more thorough mixing of the sprayed ammonia liquid during the ascent, improving SO2 absorption efficiency, increasing ammonia utilization, and reducing unreacted ammonia residue due to incomplete reaction, thereby reducing ammonia escape precursors.

[0026] 2. Optimize defogging efficiency and specifically capture ammonia-containing droplets:

[0027] By replacing the original multi-layered ordinary nozzles with large-diameter nozzles featuring a tangential conical structure, higher particle capture efficiency is achieved, especially significantly enhancing the removal of fine droplets (which may contain dissolved or encapsulated ammonia), resulting in better demisting performance. Simultaneously, reducing the number of demisting layers lowers the system pressure drop (to 300 Pa), reducing the fan load and achieving energy-saving operation. Furthermore, combined with multi-stage reflux in the circulation tank, the increased resistance resulting from increasing the spray layer to four layers is offset through fluid optimization, achieving an overall reduction in system pressure drop. Excessive demisting layers may lead to excessive resistance and clogging, negatively impacting overall operational stability.

[0028] 3. This utility model optimizes and redistributes the functions within the absorption tower, enhancing its absorption capabilities. By increasing the spray layer and optimizing the nozzles, more of the desulfurization reaction occurs in the spray zone, ensuring that the vast majority of SO2 is fully absorbed there, thereby reducing the ammonia load in subsequent stages. The demisting function is streamlined and strengthened. Due to the improved absorption efficiency at the front end, the amount of droplets entrained in the flue gas is reduced. However, the concentration of ammonia in the droplets still needs to be controlled. Therefore, fewer but more efficient large-diameter tangential conical nozzles are used, specifically designed to precisely remove those unavoidable, potentially ammonia-containing fine droplets, achieving twice the result with half the effort.

[0029] 4. Achieve dynamic circulation and concentration control of ammonia solution:

[0030] The circulation tank continuously supplies ammonia solution to each spray layer through spray pipes and recovers some incompletely reacted absorbent through reflux pipes, enabling real-time adjustment of the ammonia concentration and preventing volatilization and escape due to excessively high local ammonia concentrations. Multiple spray pipes distribute the ammonia solution to the four spray layers, ensuring uniform distribution within the tower, improving contact efficiency with flue gas, reducing reaction dead zones, and thus minimizing ammonia escape due to incomplete local reactions. By rationally positioning the reflux pipes, ammonia-laden droplets can be effectively recovered, reducing ammonia loss and lowering overall system energy consumption and operating costs. Furthermore, the multi-stage circulation from the storage tank to the circulation tank to the concentration layer prevents localized saturation crystallization of ammonium sulfate within the tower, which could clog nozzles. The circulation tank acts as a buffer hub, working in conjunction with the secondary concentration in the concentration layer to ensure controllable crystallization occurring in the external crystallizer.

[0031] In summary, the structural design of this utility model forms a highly efficient synergistic mechanism. First, the front-end spray zone is strengthened, with four high-efficiency spray layers ensuring full reaction and reducing the generation of gaseous free ammonia at the source. Second, the rear-end demisting zone is optimized, with two high-efficiency demisting layers as a guarantee, effectively capturing ammonia (usually existing in the form of droplets) that may escape but is not completely absorbed. Third, while significantly improving the desulfurization and demisting effects, the system pressure drop caused by the increase in spray layers is reduced by decreasing the number of demisting layers, ensuring the economy and stability of the entire system operation.

[0032] It should be understood that all combinations of the foregoing concepts and the additional concepts described in more detail below can be considered as part of the utility model subject matter of this disclosure, provided that such concepts do not contradict each other.

[0033] The foregoing and other aspects, embodiments, and features of the present invention will be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the present invention, such as features and / or beneficial effects of exemplary embodiments, will become apparent from the following description or may be learned through practice of specific embodiments according to the teachings of the present invention. Attached Figure Description

[0034] The accompanying drawings are not drawn to scale according to a true reference numeral. In the drawings, each identical or nearly identical component shown in the various figures can be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the present invention will now be described by way of example and with reference to the accompanying drawings, wherein:

[0035] Figure 1 This is a schematic diagram of the ammonia desulfurization system for reducing ammonia slip according to this utility model;

[0036] Figure 2 This is a schematic diagram of the nozzle structure of this utility model.

[0037] The meanings of the reference numerals in the figure are as follows:

[0038] 1. Absorption tower; 101. Storage tank; 102. Ammonium sulfate discharge pipe assembly; 103. Overflow pipe; 104. Circulation pipe; 105. Air inlet; 106. Return pipe; 2. First concentration layer; 201. First concentration pipe; 3. Second concentration layer; 301. Second concentration pipe; 4. Spray layer; 401. Spray pipe; 5. Spray layer; 6. Circulation tank; 7. Nozzle. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. All other embodiments obtained by those skilled in the art based on the described embodiments of this utility model without creative effort are within the scope of protection of this utility model. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art to which this utility model pertains.

[0040] The terms "first," "second," and similar words used in this utility model patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, unless the context clearly indicates otherwise, the singular forms of "an," "a," or "the," etc., do not indicate a quantity limitation, but rather indicate the presence of at least one. Terms such as "comprising" or "including" indicate that the element or object preceding "comprising" encompasses the features, integrals, steps, operations, elements, and / or components listed following "comprising" or "including," and do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0041] This invention does not solve the problem of severe ammonia slip in existing ammonia desulfurization systems, and proposes an ammonia desulfurization system that reduces ammonia slip. For example... Figure 1 As shown, the ammonia desulfurization system of this utility model includes an absorption tower 1. The absorption tower 1 is provided with a liquid storage tank 101, a first concentration layer 2, a second concentration layer 3, a fourth spray layer 4, and a second demisting layer 5 in sequence from bottom to top. A circulation tank 6 is provided on the outside of the absorption tower 1.

[0042] The storage tank 101 is located at the bottom of the absorption tower 1 to receive the mixed solution containing ammonium sulfate falling from the concentration layer, spray layer 4, and demister layer 5. Its highest liquid level does not exceed the lowest point of the absorption tower's air inlet to prevent backflow of the mixed solution into the air inlet. An ammonium sulfate discharge pipe assembly 102 is provided at the lower part of the storage tank 101 to discharge the saturated absorbent from the storage tank 101; a circulation pipe 104 is also provided connecting to the circulation tank 6. An overflow pipe 103 is provided at the upper part of the storage tank 101 to discharge the mixed solution that has reached the overflow level, preventing it from exceeding the maximum liquid level.

[0043] The first concentration layer 2 is located within the absorption tower 1 between the storage tank 101 and the lowest spray layer 4, and is situated above the air inlet 105 of the absorption tower 1 to ensure that sulfur-containing flue gas rises from below the first concentration layer. The circulation tank 6 is equipped with a first concentration pipe 201 connected to the first concentration layer 2, drawing ammonia from the circulation tank 6 as the concentrated spray liquid for the first concentration layer 2. The concentration layer serves as a flue gas pretreatment zone, utilizing the medium-concentration ammonia liquid (pH 6.0-6.5) input from the circulation tank 6 to initially absorb high-concentration SO2, reducing the absorption load on the spray layer 4 and preventing high-concentration SO2 from directly impacting the spray layer 4 and causing localized ammonia overload.

[0044] In some specific embodiments, a second concentration layer 3 is further provided between the first concentration layer 2 and the lowest spray layer 4; the storage tank 101 is provided with several second concentration pipes 301 connected to the second concentration layer 3, directly drawing ammonia mixture from the circulation tank 101 as the concentrated spray liquid for the second concentration layer 3. The second concentration layer 3 performs deep treatment of the preliminary desulfurized flue gas, using high-concentration ammonia liquid (containing ammonium sulfate seed crystals) input from the storage tank 101 to promote sulfuric acid crystallization. The storage tank 101 enriches the slurry with high solids content, which is directly transported to the second concentration layer 3 to accelerate crystal nucleus growth and avoid clogging of the nozzles in the spray layer 4. It forms a gradient concentration control with the first concentration layer 2, from medium to high concentration, matching the actual decrease in SO2 content in the flue gas.

[0045] Above the second concentration layer 3 are four spray layers 4, each with several evenly distributed nozzles 7, such as... Figure 2 As shown, nozzle 7 has a tangential conical structure. The included angle between the axes of adjacent nozzles 7 within the same spray layer 4 is 30°-60°, and the projections of nozzles 7 in adjacent spray layers 4 are arranged in an interlaced grid. The cross arrangement and inclined spraying can enhance the turbulent mixing of droplets and flue gas, improve mass transfer efficiency, eliminate reaction dead zones, reduce ammonia short-circuit escape and unreacted ammonia generation, thereby reducing local ammonia concentration spikes and lowering the risk of escape from the source.

[0046] Furthermore, the vertical spacing between adjacent spray layers 4 increases progressively from top to bottom. This results in a compact lower layer layout that enhances initial strength, while the expanded upper layer slows down flue gas velocity, improving SO2 absorption efficiency. By optimizing the spacing of the spray layers 4, the uniformity of flue gas distribution in the lower layer is enhanced, improving the coverage efficiency of the upper spray liquid and further reducing ammonia escape. In addition, the compact lower layer layout of the spray layers 4 enhances turbulence in the high-velocity zone, facilitating rapid SO2 absorption; the loose upper layer extends the contact time in the low-velocity zone, improving ammonia utilization and solving the problem of insufficient contact caused by differences in spray atomization effects.

[0047] like Figure 1 As shown, the circulation tank 6 is equipped with four spray pipes 401 connected to each spray layer 4. Ammonia liquid is drawn from the circulation tank 6 by a circulation pump and used as the absorption spray liquid to absorb SO2 in the flue gas and generate ammonium sulfate. The absorption tower 1 is equipped with at least two return pipes 106. At least one return pipe 106 is located below the lowest spray layer 4, and at least one return pipe 106 is located between the second and third spray layers 4. The ammonium sulfate-containing spray liquid is returned to the circulation tank 6 through the return pipes 106. Specifically, as... Figure 1 As shown, a reflux pipe is provided on the absorption tower 1 of the lowest spray layer 4 to recover unreacted ammonia liquid and maintain the concentration of the circulation tank 6; and a reflux pipe 106 is provided on the absorption tower 1 between the second and third spray layers 4 to capture free ammonia in the rising gas flow and block the gas phase escape path.

[0048] The system comprises two demisting layers 5 positioned above the uppermost spray layer 4. Each demisting layer 5 is equipped with several evenly distributed nozzles 7, which are tangentially conical in shape. Specifically, the nozzles of the demisting layer 5 spray at an angle opposite to the flue gas flow direction. The lower demisting layer 5 has nozzles at an angle of 20°-30°, capturing large droplets with high ammonia content against the airflow. The upper demisting layer 5 has nozzles at an angle of 40°-50°, intercepting fine droplets at a high angle, significantly improving the ammonia droplet capture efficiency.

[0049] This invention increases the number of spray layers in the absorption section of the absorption tower from 4 to 4, and uses large-diameter nozzles with a tangential conical structure for better atomization and more uniform coverage. This significantly enhances the SO2 absorption efficiency and improves ammonia utilization, thereby reducing the generation of unreacted ammonia at the source. Simultaneously, the number of demister layers is reduced to 2, but a high-efficiency demister with higher capture efficiency, a tangential conical structure, and a lower pressure drop is used. This modification of increasing and decreasing layers is not a simple addition or reduction of functions, but rather a re-optimization of the two major functional areas of absorption and demister within the absorption tower.

[0050] This invention enhances the absorption function at the front end, allowing most chemical reactions to be completed in the spray zone, thus reducing the burden on the downstream demisting stage. Meanwhile, the downstream stage employs more efficient nozzles to remove fine droplets carrying trace amounts of ammonia, creating a synergistic effect of enhanced absorption and precise demisting. This design not only more effectively suppresses ammonia escape in the process but also achieves a balance in system operating resistance, realizing a unity of high efficiency and low energy consumption.

[0051] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Those skilled in the art to which this invention pertains can make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of this invention shall be determined by the claims.

Claims

1. An ammonia desulfurization system for reducing ammonia slip, comprising an absorption tower (1), characterized in that, The absorption tower (1) is provided with a liquid storage tank (101), four spray layers (4), and two demisting layers (5) from bottom to top, and a circulation tank (6) is provided on its outside. The circulation tank (6) is provided with a plurality of spray pipes (401) connected to each of the spray layers (4). The absorption tower (1) is provided with a reflux pipe connected to the circulation tank (6); The liquid storage tank (101) is provided with a circulation pipe (104) connected to the circulation tank (6); Both the spray layer (4) and the demisting layer (5) are provided with a number of evenly distributed nozzles (7), and the nozzles (7) have a tangential conical structure.

2. The ammonia-based desulfurization system for reducing ammonia slip according to claim 1, characterized in that, The absorption tower (1) between the liquid storage tank (101) and the lowest spray layer (4) is provided with a first concentration layer (2), and the first concentration layer (2) is located above the air inlet (105) of the absorption tower (1). The circulation tank (6) is provided with a first concentration pipe (201) connected to the first concentration layer (2).

3. The ammonia desulfurization system for reducing ammonia slip according to claim 2, characterized in that, A second concentration layer (3) is provided between the first concentration layer (2) and the lowest spray layer (4). The storage tank (101) is provided with a number of second concentration pipes (301) that connect to the second concentration layer (3).

4. The ammonia-based desulfurization system for reducing ammonia slip according to claim 1, characterized in that, At least two return pipes (106) are provided, with at least one return pipe (106) located below the lowest spray layer (4) and at least one return pipe (106) located between the second and third spray layers (4).

5. The ammonia-based desulfurization system for reducing ammonia slip according to claim 1, characterized in that, The included angle between the axes of adjacent nozzles (7) in the same spray layer (4) is 30°-60°, and the projections of the nozzles (7) in adjacent spray layers (4) are arranged in an interlaced grid pattern.

6. The ammonia desulfurization system for reducing ammonia slip according to claim 1, characterized in that, The vertical distance between adjacent spray layers (4) increases from top to bottom.

7. The ammonia-based desulfurization system for reducing ammonia slip according to claim 1, characterized in that, The nozzle (7) of the demister layer (5) sprays at an angle opposite to the direction of the flue gas flow, and the nozzle angle of the lower demister layer (5) is 20°-30°, while the nozzle angle of the upper demister layer (5) is 40°-50°.

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