A method for treating an ammonia-containing tail gas

Abstract

This invention discloses a method for treating ammonia-containing tail gas, relating to the field of ammonia-containing tail gas treatment. The method involves the ammonia-containing tail gas entering from the bottom of an acid washing tower and passing sequentially from bottom to top through a bottom washing liquid zone, a first packing zone, a second packing zone, a spray zone, and a demister for treatment. The spray zone uses atomizing nozzles to spray out a mixed washing liquid, controlling the pH value and conductivity of the washing liquid. Each atomizing nozzle includes a nozzle body, a first chamber, multiple diversion holes, a second chamber, and an outlet hole formed on the nozzle body and connected sequentially. The opening width of the diversion holes is smaller than the opening width of the outlet holes, and the width of the outlet holes increases along the axial direction. The orthographic projections of the diversion holes and the outlet holes on the end face of the nozzle body near the outlet hole do not intersect. This method can achieve efficient removal of ammonia from the tail gas even when the pH value of the washing liquid is high, resulting in a low acid mist value in the tail gas. It eliminates the need for a secondary water washing tower for treatment, thus reducing costs.

Description

Technical Field

[0001] This invention relates to the field of ammonia-containing exhaust gas treatment, and more specifically to a method for treating ammonia-containing exhaust gas. Background Technology

[0002] Currently, the production of some chemical products is accompanied by the generation of ammonia-containing tail gas. The ammonia component in the tail gas must be washed and purified. If the ammonia content in the tail gas does not meet the emission standards, such as the emission index required by the Odor Pollutant Emission Standard (GB14554-93) (ammonia content must be less than 20 kg / h at a height of 30 m), then it is not allowed to be discharged. Existing processes include water washing and acid washing. Water washing is usually difficult to meet the emission standards for tail gas with high ammonia content. Acid washing mainly uses acid to react with ammonia to remove it. However, in practice, although acid washing can remove ammonia as much as possible, the acid concentration in the tail gas after acid washing is high, requiring further acid removal in conjunction with a water washing tower, which further increases equipment and maintenance costs. At the same time, the pH value of the washing liquid in existing acid washing processes needs to reach about 4 to achieve a good ammonia removal effect. This strong acid washing liquid has high requirements for equipment, resulting in high investment costs. The strong acidity of the washing liquid also poses a safety hazard in production.

[0003] It should be noted that the information disclosed in the background section above is only for understanding the background of this application. Therefore, the background section of this invention may include background information about the problems or environment of this invention, and is not necessarily a description of the prior art. Thus, the content included in the background section does not constitute an admission of the prior art by the applicant. Summary of the Invention

[0004] The purpose of this invention is to overcome one or more shortcomings in the prior art and provide a new method for treating ammonia-containing exhaust gas. This method can achieve efficient removal of ammonia from the exhaust gas when the pH value of the mixed washing liquid is high, while also ensuring that the acid mist value in the exhaust gas is low. It eliminates the need for additional water washing towers for secondary treatment, thus reducing costs.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for treating ammonia-containing tail gas, the method comprising: allowing the ammonia-containing tail gas to enter from the bottom of an acid washing tower, and then passing it sequentially from bottom to top through a bottom washing liquid zone, a first packing zone, a second packing zone, a spray zone, and a demister for treatment;

[0007] The spray zone uses atomizing nozzles to spray the mixed washing liquid toward the second filler zone. The mixed washing liquid is made by mixing sulfuric acid and the washing liquid in the bottom washing liquid zone. The pH value of the washing liquid is controlled to be 5.5-6.5. The mass content of ammonium sulfate in the washing liquid in the bottom washing liquid zone is controlled to be less than or equal to 40%. The porosity of the fillers in the first filler zone and the second filler zone is independently greater than 80%.

[0008] The atomizing nozzle includes a nozzle body, and a first chamber, a plurality of diversion holes, a second chamber, and an outlet hole formed on the nozzle body. The first chamber, the diversion holes, the second chamber, and the outlet hole are sequentially connected. The opening width of the diversion holes is smaller than the opening width of the outlet hole. The width of the outlet hole increases along the axis. The orthographic projections of the diversion holes and the outlet holes on the end face of the nozzle body near the outlet hole side do not intersect.

[0009] According to some preferred aspects of the present invention, the flow rate of the ammonia-containing tail gas is denoted as L1, and the flow rate of the mixed washing liquid is denoted as L2, where L2 = (0.004-0.02) × L1.

[0010] Further, the flow rate of the ammonia-containing tail gas is denoted as L1, and the flow rate of the mixed washing liquid is denoted as L2, where L2 = (0.004 - 0.08) × L1.

[0011] According to some preferred aspects of the invention, the mass content of ammonium sulfate in the washing liquid in the bottom washing liquid zone is controlled to be 15%-25%.

[0012] In some embodiments of the present invention, the conductivity of the washing liquid in the bottom washing liquid zone is controlled to be less than or equal to 300 ms / cm. Further, the conductivity of the washing liquid in the bottom washing liquid zone is controlled to be less than or equal to 250 ms / cm. Even further, the conductivity of the washing liquid in the bottom washing liquid zone is controlled to be 180-230 ms / cm.

[0013] According to some preferred aspects of the invention, the pH value of the washing liquid in the bottom washing liquid zone is controlled to be 6.0-6.5.

[0014] According to some preferred aspects of the invention, the porosity of the packings disposed in the first packing region and the second packing region is independently 88% or more.

[0015] According to some preferred aspects of the invention, the distance between the first packing zone and the second packing zone is less than the distance between the second packing zone and the spray zone.

[0016] In some embodiments of the present invention, the distance between the first packing area and the second packing area is 15-25 mm.

[0017] In some embodiments of the present invention, the distance between the second filler zone and the spray zone is 0.5-1.5m.

[0018] According to some preferred aspects of the present invention, the distance between the bottom of the first filler zone and the upper surface of the washing liquid in the bottom washing liquid zone is 2-4m.

[0019] According to some preferred aspects of the invention, the axis of the first chamber, the axis of the second chamber, and the axis of the ejection orifice are collinear.

[0020] According to some preferred aspects of the invention, the plurality of diversion holes are uniformly distributed on the outer periphery of the bottom of the interior of the first chamber.

[0021] According to some preferred aspects of the invention, the cross-section of the diversion hole is semi-circular, and one arc side of the semi-circle faces the axis of the ejection hole.

[0022] According to some preferred aspects of the present invention, the ejection orifice includes a first ejection sub-orifice communicating with the second chamber and a second ejection sub-orifice communicating with the first ejection sub-orifice, wherein the diameter of the first ejection sub-orifice is smaller than the diameter of the second ejection sub-orifice, and the diameter of the second ejection sub-orifice gradually increases along its axial direction.

[0023] According to some preferred aspects of the invention, the diameter of the first ejection sub-orifice is 0.2-0.35 times the width of the second chamber.

[0024] According to some preferred aspects of the invention, the length of the first ejector sub-orifice is 0.05-0.3 times the length of the second ejector sub-orifice.

[0025] According to some preferred aspects of the invention, the sulfuric acid and the washing liquid in the bottom washing liquid zone are mixed in a mixing pipeline;

[0026] The mixing pipeline includes a mixing tube body for supplying washing liquid and an acid adding tube. The mixing tube body is provided with a connection hole, and the acid adding tube can be inserted into the connection hole and extend into the interior of the mixing tube body. The section of the acid adding tube that extends into the interior of the mixing tube body has multiple openings.

[0027] According to some preferred aspects of the present invention, the processing method further includes: when the mass content of ammonium sulfate in the washing liquid in the bottom washing liquid zone is monitored to be 15%-40%, discharging part of the washing liquid and replenishing it with desalination process water.

[0028] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0029] Addressing the issues of high investment and safety hazards associated with existing technologies for treating ammonia-containing exhaust gas, such as the high acidity of the scrubbing liquid and the need for further treatment with a water scrubbing tower, this invention innovatively provides a novel method for treating ammonia-containing exhaust gas. This method first improves the design of the atomizing nozzle, ensuring that the atomized scrubbing liquid droplets have a relatively moderate particle size, allowing for efficient mass transfer while minimizing escape with the exhaust gas. This allows for efficient removal of ammonia from the exhaust gas while preventing the acid in the scrubbing liquid from being carried away. Furthermore, by combining two packing zones with high-porosity packing material and controlling the distance difference between each zone, the mass transfer contact area and time are increased, and the formation of a gradient concentration liquid film is facilitated. In this gradient concentration liquid film, the presence of ammonium sulfate, which is readily soluble in water, allows it to dissociate into ammonium and sulfate ions in the scrubbing liquid. The charge effect of the ionic bonds reduces the hydrogen bond strength between water molecules, thus lowering the surface tension of the solution. When the exhaust gas passes through this liquid film, the lower surface tension of the solution makes it easier to form larger droplets (less prone to escape with the airflow). On the one hand, due to the different concentrations of ammonium sulfate in the direction of liquid film extension, the viscosity of the flowing liquid film varies at different points. This makes it difficult for relatively large droplets formed when the exhaust gas comes into countercurrent contact with the liquid film to be broken into fine droplets. The larger the droplet size carried by the airflow, the stronger the gravitational settling effect, thereby reducing the amount of acid carried by the gas. That is, while ensuring that the atomized droplets have sufficient specific surface area to increase mass transfer efficiency, this invention does not blindly pursue ultra-fine droplet size. In fact, the inventors of this invention have found that droplets are not necessarily better the finer they are. With an appropriate droplet size, the droplets can suppress airflow entrainment on their own without affecting mass transfer efficiency. Furthermore, based on the high efficiency of mass transfer reaction, this invention uses a high-pH acidic washing solution mixed with sulfuric acid. That is, the acidity of the mixed washing solution is also relatively moderate, avoiding acid escape caused by excessive acid due to too high acid value. By controlling the content of ammonium sulfate in the washing solution, the load on the washing solution can be reduced while obtaining ideal ammonia removal and acid suppression effects.

[0030] In summary, this invention can achieve efficient removal of ammonia from exhaust gas even when the pH value of the mixed washing liquid is high, while also ensuring a low acid mist value in the exhaust gas, eliminating the need for additional water washing towers for secondary treatment and reducing costs. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the treatment system used in the ammonia-containing tail gas treatment method of the present invention;

[0033] Figure 2 This is a schematic diagram of the atomizing nozzle in an embodiment of the present invention (view 1);

[0034] Figure 3 This is a cross-sectional schematic diagram of the atomizing nozzle in an embodiment of the present invention;

[0035] Figure 4 for Figure 3 Enlarged view of point A in the middle;

[0036] Figure 5 This is a top view of the atomizing nozzle in an embodiment of the present invention;

[0037] Figure 6 This is a schematic diagram of the atomizing nozzle in an embodiment of the present invention (viewpoint two);

[0038] Figure 7 This is a schematic diagram of the hybrid pipeline structure in an embodiment of the present invention;

[0039] Figure 8 This is a side view of the hybrid pipeline in an embodiment of the present invention;

[0040] Figure 9 This is a schematic diagram of the structure of the mixing tube body in an embodiment of the present invention;

[0041] Figure 10 This is a schematic diagram of the acid addition tube in an embodiment of the present invention;

[0042] In the attached figures, the following are the reference numerals: 100, pickling tower; 101, bottom washing liquid zone; 102, first packing zone; 103, second packing zone; 104, spray zone; 105, demister zone; 106, tower body; 107, packing; 108, spray pipe; 109, demister; 200, atomizing nozzle; 201, nozzle body; 202, first chamber; 2021, internal thread; 203, diversion hole; 204, second chamber; 205, spray hole; 2051, first spray sub-hole; 2052, second spray sub-hole; 300, mixing pipeline; 301, mixing pipe body; 3011, connection hole; 302, acid adding pipe; 30 21. Opening; 3022. External thread; 303. First flange; 304. Second flange; 401. Pickling circulation pump; 402. Sulfuric acid pump; 403. pH value monitor; 404. Conductivity monitor; 405. Desalination process water inlet pipe; 406. Process water electric valve; 407. Ammonium sulfate storage tank; 408. Washing liquid diversion pipe; 409. Diversion electric valve; 410. Washing liquid level gauge; 411. Sulfuric acid storage tank; 412. Collection tank; 413. Tank pump; 414. Ammonia-containing tail gas inlet pipe; 415. Tail gas vent pipe; 416. Short pipe; 417. Ammonium sulfate solution pump; 418. Drain pipe. Detailed Implementation

[0043] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. The implementation conditions used in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are generally those in conventional experiments.

[0044] In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0045] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0046] This example provides a method for treating ammonia-containing exhaust gas. The method involves treating the ammonia-containing exhaust gas with a scrubbing liquid, then passing it through a multi-stage packing system, and finally through a spray zone and a demisting zone before it is discharged.

[0047] The following is combined Figures 1 to 10 The above treatment method is described as follows: the ammonia-containing tail gas enters from the bottom of the acid washing tower 100 and passes through the demister 109 of the bottom washing liquid zone 101, the first packing zone 102, the second packing zone 103, the spray zone 104 and the demister 105 from bottom to top for treatment respectively.

[0048] In the spray zone 104, the mixed washing liquid is sprayed towards the second packing zone 103 using atomizing nozzles 200. The mixed washing liquid is made by mixing sulfuric acid and the washing liquid in the bottom washing liquid zone 101, and the pH value of the washing liquid is controlled to be 5.5-6.5. The mass content of ammonium sulfate in the washing liquid in the bottom washing liquid zone 101 is controlled to be less than or equal to 40%. The porosity of the packings set in the first packing zone 102 and the second packing zone 103 is independently above 80%.

[0049] The atomizing nozzle 200 includes a nozzle body 201, and a first chamber 202, a plurality of diversion holes 203, a second chamber 204, and an outlet hole 205 formed on the nozzle body 201. The first chamber 202, the diversion holes 203, the second chamber 204, and the outlet hole 205 are sequentially connected. The opening width of the diversion hole 203 is smaller than the opening width of the outlet hole 205. The width of the outlet hole 205 increases along the axis. The orthographic projections of the diversion holes 203 and the outlet holes 205 on the end face of the nozzle body 201 near the outlet hole 205 do not intersect.

[0050] In this example, the ammonia content in the exhaust gas is mainly reduced through water absorption and acid-base neutralization reaction. The reaction equation for acid-base neutralization is: H2SO4 + 2NH3 → (NH4)2SO4.

[0051] In this example, the flow rate of the ammonia-containing tail gas is denoted as L1, and the flow rate of the mixed washing liquid is denoted as L2, where L2 = (0.004 - 0.02) × L1. Further, the flow rate of the ammonia-containing tail gas is denoted as L1, and the flow rate of the mixed washing liquid is denoted as L2, where L2 = (0.004 - 0.08) × L1. Practice shows that by controlling the ratio of the flow rate of the mixed washing liquid (which is approximately equal to the flow rate of the washing liquid due to the relatively small amount of sulfuric acid introduced) to the flow rate of the ammonia-containing tail gas, a better ammonia removal effect and acid suppression effect in the tail gas can be achieved.

[0052] The mass content of ammonium sulfate in the washing liquid in the bottom washing liquid zone 101 is controlled to be 15%-25%. As an optional embodiment, the ammonium sulfate content in the washing liquid can be controlled by conductivity. In some cases, the conductivity in the washing liquid in the bottom washing liquid zone can be controlled to be less than or equal to 300 ms / cm, further controlled to be less than or equal to 250 ms / cm, and even further controlled to be 180-230 ms / cm (the mass content of ammonium sulfate is about 20%).

[0053] The pH value of the washing liquid in the bottom washing liquid zone 101 is controlled at 6.0-6.5. The pH value of the washing liquid in this example is significantly higher than that of approximately 4 in existing technologies. This reduces the acid resistance requirements of the equipment, extends its service life, and also reduces safety hazards. For example, in the event of an unintended leak, it is more friendly to operators and equipment in the production environment. The closer the pH is to neutral, the less corrosive it is, which is beneficial for safe production and handling.

[0054] The porosity of the packing materials in the first packing zone 102 and the second packing zone 103 is independently 88% or higher. For example, standard PP packing material with a porosity of approximately 91% can be used. The two packing zones can be filled with packing materials of the same or different porosities. The arrangement of the double-layer packing material is beneficial to improving gas-liquid exchange efficiency and enhancing washing efficiency. It also allows the distance between the first packing zone 102 and the second packing zone 103 to be smaller than the distance between the second packing zone 103 and the spray zone 104. This is more conducive to forming a gradient concentration liquid film, thereby reducing the amount of droplets carried away by the exhaust gas, reducing washing liquid loss, improving washing effect, and effectively controlling acid mist.

[0055] Furthermore, the distance between the first packing zone 102 and the second packing zone 103 is 15-25mm, for example, it can be 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, 24mm, etc. In this example, it can be set to 20mm. The distance between the second packing zone 103 and the spray zone 104 is 0.5-1.5m, for example, it can be 0.6m, 0.7m, 0.8m, 0.9m, 1m, 1.1m, 1.2m, etc. The distance between the bottom of the first packing zone 102 and the upper surface of the washing liquid in the bottom washing liquid zone 101 is 2-4m, for example, 2.2m, 2.3m, 2.4m, 2.5m, 2.6m, 2.7m, 2.8m, 2.9m, 3.0m, 3.1m, 3.2m, 3.3m, 3.4m, 3.5m, 3.6m, 3.7m, 3.8m, 3.9m, etc., and in this example, it can be set to 3m. By controlling the above distances, it is possible to ensure that the washing liquid film and the ammonia-containing tail gas have high mass transfer efficiency and sufficient mass transfer time, thereby improving the washing effect.

[0056] See Figures 2 to 5 As shown, in the atomizing nozzle 200, the centerlines of the first chamber 202, the second chamber 204, and the nozzle 205 are collinear, and the centerline of the diversion hole 203 is parallel to the centerline of the first chamber 202. Multiple diversion holes 203 are evenly distributed on the outer periphery of the bottom of the first chamber 202, forming a circle. The cross-section of the diversion hole 203 is semi-circular, with one arc side of the semi-circle facing the centerline of the nozzle 205.

[0057] The ejection orifice 205 includes a first ejection sub-orifice 2051 communicating with the second chamber 204 and a second ejection sub-orifice 2052 communicating with the first ejection sub-orifice 2051. The diameter of the first ejection sub-orifice 2051 is smaller than the diameter of the second ejection sub-orifice 2052, and the diameter of the second ejection sub-orifice 2052 gradually increases along its axial direction. Further, the diameter of the first ejection sub-orifice 2051 is 0.2-0.35 times the width of the second chamber 204, and the length of the first ejection sub-orifice 2051 is 0.05-0.3 times the length of the second ejection sub-orifice 2052. This structural design of the ejection orifice 205 not only significantly improves the atomization effect but also enables the ejected atomized droplets to move at high speeds. Simultaneously, the aperture setting of the second ejection sub-orifice 2052 allows the atomized droplets to rapidly diffuse in all directions, increasing the ejection volume.

[0058] The volume of the first chamber 202 is larger than that of the second chamber 204, and an internal thread 2021 is formed on the inner wall of the first chamber 202. The above design allows a sufficient amount of washing liquid to enter, and also enables the atomizing nozzle 200 to be quickly connected to the external pipe. The presence of the internal thread allows for quick replacement with pipes that have external threads, and it has a detachable function, so that damaged or different atomizing nozzles can be replaced when needed.

[0059] The structural design of the atomizing nozzle 200 of this invention helps to break the symmetry. When the washing liquid enters the first chamber 202 and flows through the smaller diameter diversion orifice, it will form boundary layer separation and vortex structure on the arc side, resulting in turbulent flow. The curvature change on the arc side may lead to uneven pressure distribution near the outlet, forming a local low-pressure area. At the same time, when the liquid flows from the high-pressure area (inside the diversion orifice) to the low-pressure area (outside the outlet, i.e., at the second chamber 204), the sudden change in pressure gradient will aggravate the instability of the liquid flow and promote atomization. Moreover, when the liquid flows through the semi-circular channel, it is conducive to forming a thinner liquid film on the arc surface (because the curved surface guides the liquid to diffuse towards the edge). The surface tension of the thin liquid film is more significant and it is easier to break into fine mist under its own inertia. When it enters the second chamber 204, since the diversion orifice 203 and the spray hole 205 are not aligned (the two are close to the second chamber 204), the diversion orifice 203 and the spray hole 205 are not aligned (the two are close to the second chamber 204). (The orthographic projections on the end face near the nozzle 205 do not intersect) The initially atomized droplets will collide with the inner wall of the second chamber 204 to further break up and atomize, and then be further accelerated and atomized through the front section of the nozzle 205 to form relatively smaller and appropriately sized atomized droplets, which can diffuse to form a gas-liquid exchange interface with high mass transfer efficiency, thereby improving the washing effect. This is conducive to maximizing the removal of ammonia with less and appropriate amount of acid, avoiding the situation of excessive acid mist in the exhaust gas that may be caused by excessive acid.

[0060] The spray zone 104 is also equipped with a spray pipe 108, which is connected to the outlet of the atomizing nozzle 200 and the mixing pipe body 300, respectively. The atomizing nozzle 200 is detachably connected to the spray pipe 108. Furthermore, multiple atomizing nozzles can be provided to achieve full radial coverage of the tower interior, forming a large-area liquid film. This prevents ammonia content exceeding standards due to direct discharge of ammonia-containing tail gas from gaps. As an optional implementation, multiple layers of atomizing nozzles can be provided, for example, multiple sets of atomizing nozzles arranged from bottom to top. Each set is configured to cover the interior of the tower radially. The atomizing nozzles in each set are staggered to form a uniformly diffused atomized liquid film, improving the gas-liquid exchange efficiency in each area. Alternatively, multiple spray pipes can be provided, each corresponding to a set of atomizing nozzles. When multiple sets of atomizing nozzles are required, multiple spray pipes can be provided accordingly.

[0061] In this example, sulfuric acid and the washing liquid in the bottom washing liquid area are mixed in a mixing pipe 300. The mixing pipe 300 includes a mixing pipe body 301 for supplying the washing liquid and an acid adding pipe 302. The mixing pipe body 301 is provided with a connection hole 3011. The acid adding pipe 302 can be inserted into the connection hole 3011 and extends into the interior of the mixing pipe body 301. The section of the acid adding pipe 302 extending into the interior of the mixing pipe body 301 has multiple openings 3021, which are used for acids, such as sulfuric acid, to enter the interior of the mixing pipe body 301. By directly introducing sulfuric acid into the interior of the flowing washing liquid through the acid adding pipe 302, since a small amount of acid can change the pH value, both good mixing of the two can be achieved, while avoiding excessive heat release caused by excessive concentration of acid. In this example, the acid is introduced into the interior during the flow process, which achieves good mixing.

[0062] Multiple openings 3021 are arranged in an array on the section of the acid adding tube 302 that extends into the mixing tube body 301. The openings 3021 can be provided in all directions to achieve balanced acid input and avoid excessive local acid and concentrated heat release. Furthermore, the length of the section of the acid adding tube 302 that extends into the mixing tube body 301 is greater than half the inner diameter of the mixing tube body 301 and less than the inner diameter of the mixing tube body 301.

[0063] In this example, the connection hole 3011 is actually formed on the acid-adding connection pipe fixedly mounted on the mixing pipe body 301. This acid-adding connection pipe facilitates quick and stable docking with the acid-adding pipe 302. After the acid-adding pipe 302 is inserted, the two can be quickly connected and sealed via a flange, using a sealing gasket or similar material. Furthermore, a first flange 303 is provided on the connection hole 3011, i.e., a first flange is provided on the acid-adding connection pipe, and a second flange 304 is provided on the acid-adding pipe 302. The first flange 303 and the second flange 304 cooperate to fix and dock the acid-adding pipe 302 with the connection hole 3011. Simultaneously, the connection hole 3011 is located on the inlet side of the mixing pipe body 301, which facilitates efficient mixing of the added acid and the incoming washing liquid before output to the atomizing nozzle 200.

[0064] The centerline of the acid-adding pipe 302 is perpendicular to the centerline of the mixing pipe body 301. One end of the acid-adding pipe 302 is provided with an external thread 3022, which can be used to quickly connect with the internal thread on the external pipe.

[0065] The mixing pipe body 301 is made of fiberglass. Fiberglass has strong acid resistance, which is conducive to mixing high-strength acids such as high-concentration sulfuric acid into the washing liquid. It has good safety and durability. Other pipes that need to flow sulfuric acid can also use this material. Of course, other acid-resistant materials can also be used, but they will not be elaborated here.

[0066] In this mixing pipeline 300, acid, such as sulfuric acid, can be added directly into the flowing washing liquid. Under the high pressure of the acid washing circulation pump, the washing liquid easily forms turbulence inside the pipeline. Moreover, the acid addition pipe extending into the mixing pipeline body disturbs the washing liquid to a certain extent. When the acid is added, the generated heat can be quickly released radially, which not only improves the mixing safety, but also accelerates the mutual flow and mixing of acid and washing liquid to a certain extent, which can quickly achieve uniform mixing and improve the uniform washing effect of subsequent ammonia-containing tail gas. The amount of acid added is easy to control, avoiding the problem of excessive acid causing an increase in acid mist value in the tail gas. At the same time, the mixing of a large amount of washing liquid with a small amount of strong acid can also reduce the corrosiveness of the acid. The efficient and uniformly mixed washing liquid has a more stable ammonia removal effect and is less likely to cause the ammonia in the tail gas to exceed the standard, thus improving the stability and continuity of the treatment system.

[0067] The treatment method for ammonia-containing tail gas also includes: when the mass content of ammonium sulfate in the washing liquid in the bottom washing liquid zone 101 is monitored to be 15%-40%, a portion of the washing liquid is discharged and desalination process water is replenished.

[0068] In this example, the treatment system used in the treatment method for ammonia-containing tail gas includes the aforementioned acid washing tower 100, mixing pipeline 300, atomizing nozzle 200, etc., and also includes acid washing circulation pump 401, etc.

[0069] Pickling tower 100 includes tower body 106, packing 107 (including first packing and second packing), spray pipe 108, and demister 109. The tower body 106 has, from bottom to top, a bottom washing liquid zone 101, a first packing zone 102, a second packing zone 103, a spray zone 104, and a demister 105. The bottom washing liquid zone 101 stores the washing liquid. The first packing is located in the first packing zone 102, and the second packing is located in the second packing zone 103. The first and second packings can be supported by a grid made of corrosion-resistant material, which is fixed to the inner wall of the pickling tower. The demister 109 is located in the demister 105. Multiple atomizing nozzles 200 are provided. The ammonia-containing tail gas inlet and the desalination process water inlet are respectively set in the spray zone 104. The lower part of the tower body 106 is provided with an ammonia-containing tail gas inlet and a desalination process water inlet, and the upper part is provided with a tail gas outlet. The tail gas outlet is located on the outlet side of the demister 109. The ammonia-containing tail gas inlet and the desalination process water inlet are respectively connected to the bottom washing liquid zone 101. The inlet of the spray pipe 108 is connected to the outlet of the mixing pipe 300, and the outlet of the spray pipe 108 is connected to multiple atomizing nozzles 200. The acid washing circulation pump 401 is connected to the bottom washing liquid zone 101 and the inlet of the mixing pipe 300. The mixing pipe 300 is also provided with a sulfuric acid inlet. The sulfuric acid inlet is provided with an acid adding pipe 302 to allow the sulfuric acid to be introduced.

[0070] The treatment system also includes a sulfuric acid pump 402, a pH monitor 403, a conductivity monitor 404, and a control system (not shown). The pH monitor 403 is used to monitor the pH value of the washing liquid at the outlet of the pickling circulation pump 401, and the conductivity monitor 404 is used to monitor the conductivity of the washing liquid at the outlet of the pickling circulation pump 401. The sulfuric acid pump 402 is connected to the sulfuric acid inlet. The sulfuric acid pump 402, pH monitor 403, and conductivity monitor 404 are respectively connected to the control system. This setup allows for real-time monitoring of the pH value and conductivity of the washing liquid at the outlet of the pickling circulation pump 401. Real-time pH feedback can adjust the frequency of the sulfuric acid pump 402 according to specific circumstances, thereby increasing or decreasing the amount of sulfuric acid introduced. Real-time conductivity feedback can promptly determine the concentration of ammonium sulfate in the washing liquid. If the concentration is too high, it will be detrimental to the removal of ammonia from the tail gas. Based on the conductivity, it can be adjusted whether the washing liquid needs to be discharged and new desalination process water needs to be added, thereby ensuring a stable ammonia removal effect.

[0071] Furthermore, the treatment system also includes a desalination process water inlet pipe 405, a process water electric valve 406 installed on the desalination process water inlet pipe 405, an ammonium sulfate storage tank 407, a washing liquid diversion pipe 408, a diversion electric valve 409 installed on the washing liquid diversion pipe 408, and a washing liquid level gauge 410 for monitoring the washing liquid level in the bottom washing liquid zone 101. The washing liquid diversion pipe 408 is connected to the outlet of the pickling circulation pump 401 and the ammonium sulfate storage tank 407, respectively. The process water electric valve 406, the diversion electric valve 409, and the washing liquid level gauge 410 are respectively connected to the control system. The opening and closing of the diversion electric valve 409 is controlled based on the conductivity monitored by the conductivity monitor 404. If the conductivity exceeds the preset value (i.e., the ammonium sulfate concentration is too high), the diversion electric valve 409 is activated, thereby discharging part of the washing liquid into the ammonium sulfate storage tank 407. At the same time, the process water electric valve 406 is activated to replenish new desalination process water to the bottom washing liquid zone 101, ensuring that the washing liquid level in the bottom washing liquid zone 101 is always maintained at the preset height. In addition, if other situations cause the washing liquid level in the bottom washing liquid zone to drop, the process water electric valve 406 is activated in a timely manner based on the feedback from the washing liquid level gauge to replenish new desalination process water to the bottom washing liquid zone 101. In this example, the diversion electric valve 409 is set to be activated to discharge part of the washing liquid once the conductivity exceeds the threshold, and the discharge volume is small each time. Therefore, even if the discharge outlet is set at the outlet of the pickling circulation pump 401, it will not affect the amount of washing liquid entering the spray zone 104. The ammonium sulfate solution stored in the ammonium sulfate storage tank 407 can be pumped to the thermoelectric ammonia tank through the ammonium sulfate solution pump 417 to achieve co-production of soda ash and thermoelectric system. In the desulfurization process of thermoelectric power, the ammonium sulfate product with a water content of ≤3% is produced by evaporation and concentration (dehydration of boiler flue gas) in the desulfurization tower, thickening, and separation by centrifuge. It is then sent to compound fertilizer as raw material or sold.

[0072] The treatment system also includes a sulfuric acid storage tank 411, a collection tank 412, a tank pump 413, an ammonia-containing tail gas input pipe 414, a tail gas vent pipe 415, and a short pipe 416. The sulfuric acid storage tank 411 is connected to the acid addition pipe 302 and the collection tank 412 respectively. The bottom washing liquid area 101 is also connected to the collection tank 412. The tank pump 413 is connected to the collection tank 412 and the bottom washing liquid area 101 respectively.

[0073] The ammonia-containing exhaust gas inlet pipe 414 is connected to the inlet of the short connector 416 and the ammonia-containing exhaust gas inlet, respectively. The exhaust gas vent pipe 415 is connected to the outlet of the short connector 416 and the exhaust gas outlet, respectively. The exhaust gas vent pipe is located in... Figure 1 Although the middle section extends horizontally, this only represents a part of it; the latter part extends vertically, potentially reaching a height of tens of meters.

[0074] The sulfuric acid storage tank 411 is used to buffer the sulfuric acid introduced by the external pipe. The collection tank 412 is used to collect the sulfuric acid discharged from the outside (such as the sulfuric acid storage tank 411 overflow or sulfuric acid pipeline maintenance) or the washing liquid in the bottom washing liquid zone 101 of the acid washing tower 100 during maintenance (discharged to the collection tank through the vent pipe 418), or the solution discharged from the ammonium sulfate storage tank 407 and other liquids that may be discharged from various components (such as acidic wastewater from the maintenance of various pumps). The solution in the collection tank 412 is usually acidic and can be pumped into the bottom washing liquid zone 101 as washing liquid through the tank pump 413 when the treatment system is working, so as to realize the recycling of waste liquid. The function of the short pipe 416 is that once the acid washing tower 100 malfunctions, the ammonia-containing tail gas can be directly connected to the tail gas vent pipe 415 through the short pipe 416.

[0075] The workflow in this example is roughly as follows:

[0076] See Figures 1 to 10 As shown, ammonia-containing tail gas from an external source, such as a filter, enters the washing liquid in the bottom washing liquid zone 101 through the ammonia-containing tail gas inlet pipe 414 at the bottom of the tower body 106. Based on the characteristics of the gas, after the ammonia-containing tail gas undergoes preliminary washing treatment in the washing liquid of the bottom washing liquid zone 101, it moves upward through the first packing zone 102 and comes into countercurrent contact with the washing liquid from the upper part to absorb ammonia. It continues to move upward and then continues to pass through the second packing zone 103 and comes into countercurrent contact with the washing liquid from the upper part to absorb ammonia. After arriving at the spray zone 104, it is washed again in the spray zone 104 (in fact, the gas-liquid exchange film continues to exist from the spray zone downward). Finally, it passes through the demister 109 in the demister zone 105 to enhance the removal of droplets (so that the droplets that may be contained in the tail gas can be retained in the acid washing tower 100, thereby preventing the droplets from transferring or spreading into the atmosphere, and also reducing the loss of washing liquid). Then, it is discharged to the outside from the tail gas outlet through the tail gas vent pipe 415.

[0077] The mixed washing liquid in the spray zone 104 comes from the mixing pipeline 300. The mixing pipeline 300 mixes the washing liquid from the pickling circulation pump 401 with the sulfuric acid pumped from the sulfuric acid pump 402 to form a mixed washing liquid.

[0078] Two pickling circulation pumps 401 are provided, one for standby and one for use. At the outlet of the pickling circulation pump 401, there is also a washing liquid diversion pipe 408 and a diversion electric valve 409 installed on the washing liquid diversion pipe 408. The washing liquid diversion pipe 408 diverts a portion of the washing liquid that has reached the expected conductivity to the ammonium sulfate storage tank 407 for buffering. The start and stop of the diversion electric valve 409 are controlled according to the monitoring results of the conductivity monitor 404.

[0079] Meanwhile, the sulfuric acid flow rate is also adjusted according to the pH value of the washing liquid at the outlet of the pickling circulation pump 401, which is monitored in real time, to ensure that the pH value of the washing liquid at the outlet of the pickling circulation pump is always at the preset value. Furthermore, concentrated sulfuric acid (e.g., mass concentration of 70%-98%) from the external pipe enters the sulfuric acid storage tank 411 through the flow meter, process valve and remote control valve, and is then sent to the mixing pipeline 300 by the metering pump, i.e., sulfuric acid pump 402. After mixing with part of the circulating washing liquid at the outlet of the pickling circulation pump 401, it is evenly sprayed and dispersed to the packing surface in the pickling tower through the atomizing nozzle 200. After being sprayed from top to bottom to absorb ammonia in the tail gas, it enters the bottom washing liquid area of ​​the pickling tower and is then pressurized by the pickling circulation pump for recycling.

[0080] The liquid level of the washing liquid in the bottom washing liquid area is monitored by the washing liquid level gauge 410. A multi-contact level gauge or multiple independent level gauges can be set to monitor the high, medium and low liquid levels of the washing liquid in the bottom washing liquid area. Simultaneous monitoring of the medium and high liquid levels ensures that the liquid level of the washing liquid remains stable, and real-time monitoring of the low liquid level can prevent the acid washing circulation pump from running dry when the liquid level is too low.

[0081] The above treatment method and system were used for acid washing of ammonia-containing tail gas from the alkali filter press of Jiangsu Huachang Chemical Co., Ltd. The test results are shown in Tables 1-4 (corresponding to multiple time periods of sampling).

[0082] Table 1

[0083]

[0084]

[0085] Table 2

[0086]

[0087] Table 3

[0088]

[0089]

[0090] Table 4

[0091]

[0092] As can be seen from the table above, the ammonia content in the exhaust gas after acid washing is far lower than the odor pollutant emission standard (GB14551-93). At a height of 30m, the ammonia content should be less than 20kg / h, and the sulfuric acid mist content should meet the emission standards stipulated by Jiangsu Province (≤5mg / m³). 3 ).

[0093] In summary, this invention can achieve a concentration of NH3 in exhaust gas of <8.5 mg / m³. 3 Sulfuric acid mist ≤ 2 mg / m³ 3 The emissions are significantly better than national standards for exhaust gas. Furthermore, the wastewater from the acid washing process is primarily composed of ammonium sulfate, the concentration and pH of which are adjustable. Ammonium sulfate can also be recycled as a byproduct, offering advantages in both energy conservation and environmental protection.

[0094] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

[0095] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A method for treating an ammonia-containing tail gas, characterized by, The treatment method includes: allowing the ammonia-containing tail gas to enter from the bottom of the acid washing tower, and then passing through the bottom washing liquid zone, the first packing zone, the second packing zone, the spray zone, and the demister from bottom to top for treatment; The spray zone uses atomizing nozzles to spray the mixed washing liquid toward the second filler zone. The mixed washing liquid is made by mixing sulfuric acid and the washing liquid from the bottom washing liquid zone. The pH value of the washing liquid in the bottom washing liquid zone is controlled to be 5.5-6.5, and the mass content of ammonium sulfate in the washing liquid in the bottom washing liquid zone is controlled to be less than or equal to 40%. The porosity of the fillers in the first filler zone and the second filler zone is independently greater than 80%. The distance between the first filler zone and the second filler zone is less than the distance between the second filler zone and the spray zone. The atomizing nozzle includes a nozzle body, and a first chamber, a plurality of diversion holes, a second chamber, and an outlet hole formed on the nozzle body. The first chamber, the diversion holes, the second chamber, and the outlet hole are sequentially connected. The opening width of the diversion holes is smaller than the opening width of the outlet hole. The width of the outlet hole increases along the axis. The orthographic projections of the diversion holes and the outlet holes on the end face of the nozzle body near the outlet hole side do not intersect.

2. The method of claim 1, wherein, The flow rate of the ammonia-containing tail gas is denoted as L1, and the flow rate of the mixed washing liquid is denoted as L2, where L2 = (0.004 - 0.02) × L1.

3. The method of claim 2, wherein the ammonia-containing tail gas is treated by, The flow rate of the ammonia-containing tail gas is denoted as L1, and the flow rate of the mixed washing liquid is denoted as L2, where L2 = (0.004 - 0.08) × L1.

4. The method of claim 1, wherein, The mass content of ammonium sulfate in the washing liquid in the bottom washing liquid zone is controlled to be 15%-25%; and / or, the pH value of the washing liquid in the bottom washing liquid zone is controlled to be 6.0-6.5; and / or, the porosity of the packings in the first packing zone and the second packing zone is independently 88% or more.

5. The method of claim 1, wherein, The distance between the first packing area and the second packing area is 15-25 mm; and / or, the distance between the second packing area and the spray area is 0.5-1.5 m; and / or, the distance between the bottom of the first packing area and the upper surface of the washing liquid in the bottom washing liquid area is 2-4 m.

6. The method of claim 1, wherein, The centerline of the first chamber, the centerline of the second chamber, and the centerline of the ejection hole are collinear; and / or, the plurality of diversion holes are evenly distributed on the outer periphery of the bottom of the interior of the first chamber; and / or, the cross-section of the diversion hole is semi-circular, and one side of the arc of the semi-circle faces the centerline of the ejection hole.

7. The method of claim 1, wherein, The ejection orifice includes a first ejection sub-orifice communicating with the second chamber and a second ejection sub-orifice communicating with the first ejection sub-orifice. The diameter of the first ejection sub-orifice is smaller than the diameter of the second ejection sub-orifice, and the diameter of the second ejection sub-orifice gradually increases along its axial direction.

8. The method of claim 7, wherein the ammonia-containing tail gas is treated by, The diameter of the first ejector orifice is 0.2-0.35 times the width of the second chamber; and / or, the length of the first ejector orifice is 0.05-0.3 times the length of the second ejector orifice.

9. The method of claim 1, wherein, The sulfuric acid and the washing liquid in the bottom washing liquid zone are mixed in the mixing pipeline; The mixing pipeline includes a mixing tube body for supplying washing liquid and an acid adding tube. The mixing tube body is provided with a connection hole, and the acid adding tube can be inserted into the connection hole and extend into the interior of the mixing tube body. The section of the acid adding tube that extends into the interior of the mixing tube body has multiple openings.

10. The method of claim 1, wherein, The treatment method further includes: when the mass content of ammonium sulfate in the washing liquid in the bottom washing liquid area is detected to be 15%-40%, discharging part of the washing liquid and replenishing it with desalination process water.

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