Apparatus for production of ammonium nitrate from nitric acid and ammonia
Patent Information
- Application Number
- EP2024705180
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-02-16
- Filing Date
- 2024-02-16
- Publication Date
- 2025-12-24
AI Technical Summary
The reaction between nitric acid and ammonia in ammonium nitrate production is prone to local overheating and corrosion, which can lead to equipment damage and maintenance issues due to the exothermic nature of the reaction and the corrosive properties of the reactants.
A device with a recirculation circuit and a neutralization reactor featuring multiple regions with perforated plates and a tube bundle reactor design, where the perforated plates are strategically placed to enhance mixing and reduce corrosion by distributing heat and diluting nitric acid before it comes into contact with corrosive areas, and using polytetrafluoroethylene for nitric acid supply devices to prevent direct contact with metallic walls.
The solution effectively manages heat distribution to prevent overheating and reduces corrosion by ensuring rapid and uniform mixing of reactants, thereby extending equipment lifespan and minimizing maintenance needs.
Smart Images
Figure EP2024054037_22082024_PF_FP
Abstract
Description
[0001] Device for producing ammonium nitrate from nitric acid and ammonia
[0002] The invention relates to a device for producing ammonium nitrate from nitric acid and ammonia, wherein operation is carried out in a recirculation circuit, i.e. a stream of ammonium nitrate is recirculated in the circuit, whereby local overheating during the strongly exothermic reaction between the nitric acid and ammonia is avoided.
[0003] Two challenges arise in the reaction between nitric acid and ammonia. First, the reaction heat must be dissipated to avoid local overheating. This can be solved, for example, by a recirculation loop, whereby the circulating amount of ammonium nitrate is available to absorb the heat. A system with a recirculation loop, for example, was described by Axel Eben and Paul Kaupas in "Ammonium Nitrate Production and Operational Experience" (Nitrogen & Methanol No. 235 (1998), p. 25ff). The ratio of reactants supplied to circulating ammonium nitrate is typically between 1:5 and 1:100.
[0004] Secondly, the reactants are corrosive. Nitric acid, which is usually added first, leads to corrosion damage, which in turn requires regular maintenance and part replacement.
[0005] A reactor for producing an ammonium nitrate solution is known from AU 654632 B.
[0006] The object of the invention is to reduce the extent of corrosion inside the device between the introduction of nitric acid and the most complete possible reaction with ammonia.
[0007] This object is achieved by a device having the features specified in claim 1. Advantageous further developments emerge from the subclaims, the following description and the drawing. The device according to the invention is used to produce ammonium nitrate from nitric acid and ammonia. The device has a recirculation circuit. A large portion of the product is therefore circulated. As a result, more mass is available at the site of the reaction between the nitric acid and ammonia, so that the released heat of reaction is quickly and more widely distributed and temperature peaks can thus be reliably avoided. A neutralization reactor is arranged in the recirculation circuit. The nitric acid and the ammonia are fed into the neutralization reactor to react with one another to form ammonium nitrate. The neutralization reactor has at least a first region and a second region.The first zone is fluidically arranged upstream of the second zone in the recirculation circuit. The first zone has at least one nitric acid supply device. The second zone is a tube-bundle reactor. The tubes of the tube-bundle reactor are designed to supply ammonia.
[0008] According to the invention, the first region comprises at least one first perforated plate. The first perforated plate is arranged perpendicular to the flow direction. The first perforated plate is arranged upstream of the nitric acid supply device in the flow direction. It is therefore crucial that the perforated plate is arranged upstream of the nitric acid supply device, i.e., it is not exposed to the nitric acid and therefore does not corrode. However, the strong turbulence of the perforated plate ensures very good and rapid mixing of the nitric acid in the ammonium nitrate. This eliminates the need for flow-generating internals downstream of the nitric acid supply device, which, due to their arrangement, are heavily exposed to the still slightly diluted nitric acid and therefore easily corrode.
[0009] In a further embodiment of the invention, the first perforated plate has a plurality of first holes. A first number of first holes are arranged adjacent to the wall of the first region. Additionally, further holes can be arranged in the interior region (between the holes adjacent to the wall). The nitric acid supply device has at least the first number of supply openings. Preferably, the nitric acid supply device has exactly the first number of supply openings. As a result, each hole, and thus each turbulence generated by the hole, is assigned exactly one nitric acid supply device. As a result, the nitric acid is injected into a particularly turbulent region, thereby achieving particularly rapid mixing and thus dilution. Alternatively, for example, two nitric acid supply devices can be assigned to each hole.
[0010] In a further embodiment of the invention, the first region has an axis of symmetry. In a tube, the central axis is the axis of symmetry. This also applies analogously, for example, to a truncated cone or a body with a polygonal cross-section. The feed openings are either arranged perpendicular to the axis of symmetry or are arranged at an angle of maximum ± 20 ° in the plane perpendicular to the axis of symmetry, deviating from the perpendicular to the axis of symmetry, and at an angle of maximum ± 45 ° in the plane through which the axis of symmetry runs, deviating from the perpendicular to the axis of symmetry. It is therefore particularly preferred for the feed opening, the turbulent flow generated by a hole, and the axis of symmetry to lie on the same line. Alternatively, a deviation in the plane can be used to achieve additional rotation of the ammonium nitrate flow.
[0011] In a further embodiment of the invention, all supply openings have the same angle in the plane perpendicular to the axis of symmetry, deviating from the perpendicular to the axis of symmetry. This allows a directed vortex flow to be generated.
[0012] In a further embodiment of the invention, the feed openings are arranged such that the nitric acid fed from each individual feed opening is introduced into exactly one swirl, which is generated by a hole in the first perforated plate adjacent to the wall of the first region.
[0013] In a further embodiment of the invention, the feed openings are made of polytetrafluoroethylene. Preferably, the feed openings are clamped into a flange in the form of a sleeve made of polytetrafluoroethylene. This creates a spatial distance from the hot container wall, while allowing the sleeve to be easily replaced, so that hot nitric acid does not come into direct contact with the metal wall.
[0014] In a further embodiment of the invention, the distance between the first perforated plate and the feed openings is less than 10% of the length of the zone of increased turbulence created by the first perforated plate. While the entire flow within the neutralization reactor is preferably turbulent, the first perforated plate creates a region with increased turbulent flow, with the Reynolds number preferably being at least 50% higher than the average Reynolds number across the entire cross-section of the neutralization reactor at this location.
[0015] In a further embodiment of the invention, the distance between the first perforated plate and the feed openings is 0.08 times to 0.3 times the diameter of the first perforated plate.
[0016] In a further embodiment of the invention, the nitric acid flow coming from the feed opening is directed directly onto the turbulence.
[0017] In a further embodiment of the invention, the first region has at least one second perforated plate. The second perforated plate is arranged perpendicular to the flow direction. The second perforated plate is arranged in the flow direction between the nitric acid supply device and the second region and thus the tube bundle reactor. After an initial mixing by the first perforated plate, the second perforated plate creates further turbulence for further mixing, thereby achieving homogenization during the subsequent neutralization. However, the initial mixing at the first perforated plate already achieves sufficient mixing to reduce the local concentration of nitric acid, so that corrosion at the second perforated plate is limited.In a further embodiment of the invention, the first region between the nitric acid supply device and the end facing the second region has a length l. The second perforated plate is spaced from the nitric acid supply device by at least 0.45 l in the flow direction. Furthermore, the second perforated plate is spaced from the nitric acid supply device by at most 0.85 l in the flow direction. As a result, the second perforated plate is arranged in the central part. This ensures that a sufficiently large portion is available for the initial mixing so that the dilution of the nitric acid in the first part is completed, thus largely preventing corrosion.
[0018] In a further embodiment of the invention, the first perforated plate has a first total number of holes. The second perforated plate has a second total number of holes. The second total number is greater than the first total number.
[0019] In a further embodiment of the invention, no internal components are arranged between the feed openings and the second perforated plate. Local differences in the concentration of nitric acid are to be expected in this area, and therefore, increased corrosion can occur due to locally higher concentrations.
[0020] In a further embodiment of the invention, the first region is conical. The first region has the largest diameter adjacent to the second region. Preferably, the first region is conical with an angle of 5° to 10°. This shallow angle prevents flow separation at the wall and simultaneously achieves expansion. The angle mentioned here is the angle between the wall and the axis of the neutralization reactor. The actual opening angle is thus twice as large, since this angle of 5° to 10° is opposite on both sides. The opening angle is therefore between 10° and 20°.
[0021] In a further embodiment of the invention, the first perforated plate has holes with a shape selected from the group comprising circle, ellipse, oval, acute oval, triangle, square, pentagon, hexagon, and rectangle. Particularly preferably, the holes in the first perforated plate all have the same shape. Particularly preferably, the first perforated plate has triangular holes. This is preferred because the injection of nitric acid through the nitric acid supply device often has a conical shape, thereby achieving optimal coordination between the turbulence generated by the first perforated plate and the injected nitric acid, thus achieving particularly rapid and efficient mixing.
[0022] In a further embodiment of the invention, the second perforated plate has holes with a shape selected from the group comprising circle, ellipse, oval, pointed oval, square, pentagon, hexagon, and rectangle. Particularly preferably, the holes in the second perforated plate all have the same shape.
[0023] For example, and preferably, the holes of the first perforated plate and the holes of the second perforated plate have the same shape.
[0024] Alternatively, the holes in the first perforated plate are triangular in shape, while the holes in the second perforated plate are round. This can be advantageous because the turbulent regions created by the first perforated plate function differently than those of the second perforated plate. The function of the first perforated plate is to generate turbulence for the fastest possible mixing of the injected nitric acid. However, the function of the second perforated plate is primarily to homogenize the flow.
[0025] Preferably, therefore, the distribution of the holes in the first perforated plate is designed for optimal mixing of the injected nitric acid and is thus locally and geometrically designed for the nitric acid supply device.
[0026] Preferably, the holes in the second perforated plate are distributed evenly across the second perforated plate. For example, the holes in the second perforated plate can be arranged hexagonally.
[0027] In a further embodiment of the invention, the tubes of the tube bundle reactor are made of titanium. Furthermore, the tubes have holes of 1 mm to 5 mm for the supply of ammonia. To prevent ammonium nitrate from passing through the tubes, the ammonia surrounding the tubes is maintained at an overpressure of 0.2 bar to 2 bar, preferably 0.2 bar to 1.2 bar, more preferably 0.5 bar to 1.2 bar, relative to the pressure of the ammonium nitrate in the tubes.
[0028] In a further embodiment of the invention, the neutralization reactor has a third region. The third region is arranged downstream of the second region in terms of flow. The third region has a static mixer.
[0029] The device according to the invention is explained in more detail below using an embodiment shown in the drawing.
[0030] Fig. 1 : Cross section
[0031] Fig. 1 shows a schematic cross-section of part of an exemplary device according to the invention, more precisely the neutralization reactor 10 of the device. The neutralization reactor 10 has three regions 12, 14, 16: a first region 12 located at the beginning in the flow direction, a second region 14 designed as a tube bundle reactor in the middle, and a third region 16. In the illustration below, a first perforated plate 40 is arranged as the first element in terms of flow technology. The first perforated plate has, for example, seven hexagonally arranged holes, i.e., six holes adjacent to the wall and one hole located centrally in the middle. As the ammonium nitrate flows through the holes, a fluidically turbulent region is created behind each hole. The nitric acid supply device 20, which has six supply openings 22 (two visible in the cross-section), is arranged shortly behind the first perforated plate 40.Each of the feed openings 22 is directed toward one of the turbulent regions created by the holes in the first perforated plate 40, so that the nitric acid is introduced into a flow region that ensures very rapid dilution. The first region 12 has a length l between the feed openings 22 and the end facing the second region 14. In the example shown, a second perforated plate 50 is arranged approximately 0.55 l from the feed openings 22 and approximately 0.45 l from the end of the first region 12 facing the second region 14. The first region 12 widens conically, for example, at an angle of 10°. As a result, the diameter of the second perforated plate 50 shown here is larger (opening angle thus 20°) than that of the first perforated plate 40.For example, the second perforated plate has nineteen hexagonally arranged holes - one centrally in the middle, six in a ring surrounding the middle, and twelve in an outer ring adjacent to the wall. The second perforated plate 50 thus ensures further turbulence and thus even better mixing and, at the same time, homogenization. The sufficient distance between the feed openings 22 and the second perforated plate 50 ensures that the homogenization resulting from the first perforated plate 40 and thus the dilution of the nitric acid before reaching the second perforated plate 50 is sufficiently high that no corrosion occurs due to locally higher nitric acid concentrations. The ammonium nitrate then flows through the tube bundle reactor in the tubes 30 in the second region 14. The gas space 32 surrounding the tubes 30 contains ammonia, for example, with an overpressure of 1 bar relative to the ammonium nitrate.The ammonia enters the ammonium nitrate through holes, for example, 3 mm in diameter, in the walls of the tubes 30, where it reacts with the nitric acid to form ammonium nitrate. Subsequently, the neutralization reactor 10 in the example shown has a third section 16 in which the cross-section is reduced back to the original cross-section (in particular, the cross-section of the recirculation circuit). A mixer could be arranged in this third section.
[0032] Reference symbol
[0033] 10 Neutralization reactor
[0034] 12 first area
[0035] 14 second area
[0036] 16 third area
[0037] 20 Nitric acid supply device
[0038] 22 Feed opening
[0039] 30 pipe
[0040] 32 Gas room
[0041] 40 first perforated plate
[0042] 50 second perforated plate
Claims
Patent claims 1. A device for producing ammonium nitrate from nitric acid and ammonia, the device comprising a recirculation circuit, a neutralization reactor (10) being arranged in the recirculation circuit, the neutralization reactor (10) comprising at least a first region (12) and a second region (14), the first region (12) being arranged fluidically upstream of the second region (14) in the recirculation circuit, the first region (12) comprising at least one nitric acid supply device (20), the second region (14) being a tube bundle reactor, the tubes (30) of the tube bundle reactor being designed for supplying ammonia, characterized in that the first region (12) comprises at least one first perforated plate (40), the first perforated plate (40) being arranged perpendicular to the flow direction, the first perforated plate (40) being arranged in the flow direction upstream of the nitric acid supply device (20) is arranged.
2. Device according to claim 1, characterized in that the first perforated plate (40) has a plurality of first holes, wherein a first number of first holes are arranged adjacent to the wall of the first region (12), wherein the nitric acid supply device (20) has at least the first number of supply openings (22).
3. Device according to claim 2, characterized in that the first region (12) has an axis of symmetry, wherein the feed openings (22) are arranged either perpendicular to the axis of symmetry or at an angle of maximum ± 20 ° in the plane which is perpendicular to the axis of symmetry, deviating from the perpendicular to the axis of symmetry and at an angle of maximum ± 45 ° in the plane through which the axis of symmetry runs, deviating from the perpendicular to the axis of symmetry.
4. Device according to claim 3, characterized in that all feed openings (22) have the same angle in the plane which is axis of symmetry is perpendicular, deviating from the perpendicular to the axis of symmetry.
5. Device according to one of claims 2 to 4, characterized in that the feed openings (22) are arranged such that the nitric acid fed from each individual feed opening (22) is introduced into exactly one swirl which is generated by a hole in the first perforated plate (40) adjacent to the wall of the first region (12).
6. Device according to one of claims 2 to 5, characterized in that the feed openings (22) are made of polytetrafluoroethylene.
7. Device according to one of the preceding claims, characterized in that the distance between the first perforated plate (40) and the feed openings (22) is less than 10% of the length of the turbulent flow generated by the first perforated plate (40).
8. Device according to one of the preceding claims, characterized in that the distance between the first perforated plate (40) and the feed openings (22) is 0.08 times to 0.3 times the diameter of the first perforated plate (40).
9. Device according to one of the preceding claims, characterized in that the first region (12) has at least one second perforated plate (50), wherein the second perforated plate (50) is arranged perpendicular to the flow direction, wherein the second perforated plate (50) is arranged in the flow direction between the nitric acid supply device (20) and the second region (14) and thus the tube bundle reactor.
10. Device according to claim 9, characterized in that the first region (12) between the nitric acid supply device (20) and the end facing the second region (14) has a length I, wherein the second perforated plate (50) is spaced apart from the nitric acid supply device (20) by at least 0.45 I in the flow direction, wherein the second perforated plate (50) is spaced apart from the nitric acid supply device (20) by at most 0.85 l in the flow direction.
11. Device according to one of claims 9 to 10, characterized in that the first perforated plate (40) has a first total number of holes, wherein the second perforated plate (50) has a second total number of holes, wherein the second total number is greater than the first total number.
12. Device according to one of claims 9 to 11, characterized in that no internal components are arranged between the feed openings (22) and the second perforated plate (50).
13. Device according to one of the preceding claims, characterized in that the first region (12) is conical, the first region (12) having the largest diameter adjacent to the second region (14).
14. Device according to claim 13, characterized in that the first region (12) is conical with an angle of 5 ° to 10 °.
15. Device according to one of the preceding claims, characterized in that the first perforated plate (40) has holes with a shape selected from the group comprising circle, ellipse, oval, acute oval, triangle, square, pentagon, hexagon, rectangle.
16. Device according to claim 15, characterized in that the holes of the first perforated plate (40) all have the same shape.
17. Device according to one of the preceding claims, characterized in that the tubes (30) of the tube bundle reactor are made of titanium, wherein the tubes (30) have holes of 1 mm to 5 mm for supplying ammonia.
18. Device according to one of the preceding claims, characterized in that the neutralization reactor (10) has a third region (16), wherein the third region (16) is arranged fluidically behind the second region (14), wherein the third region (16) has a static mixer.