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EP-4735387-A1 - AMMONIUM NITRATE REACTOR WITH STATIC MIXER

EP4735387A1EP 4735387 A1EP4735387 A1EP 4735387A1EP-4735387-A1

Abstract

The disclosure pertains to an ammonium nitrate reactor with a first type static mixer in the mixing zone upstream of the tube bundle and/or a second type static mixer downstream of the tube bundle.

Inventors

  • PATIL, RAHUL
  • Gevers, Lambertus Wilhelmus
  • WASSIE, Solomon Assefa
  • TSOPOZIDIS, Michail

Assignees

  • Stamicarbon B.V.

Dates

Publication Date
20260506
Application Date
20240909

Claims (14)

  1. Claims 1. A reaction unit (100) for the production of ammonium nitrate by neutralization of aqueous nitric acid with gaseous NH3, the reaction unit comprising: - an inlet zone (1) comprising a first inlet (2) for a stream of recirculated ammonium nitrate solution and a second inlet (3) for the aqueous nitric acid; - a mixing zone (4) located downstream of said inlet zone (1) and preferably comprising a first type static mixer (5) adapted to mix the recirculated ammonium nitrate solution with the aqueous nitric acid to form a liquid mixture; - a shell-and-tube chamber (6) comprising tube bundle (7) and a shell space (8), wherein the shell space comprises an inlet (9) for gaseous NH3, wherein a tube of the tube bundle has a tube wall (16), an inlet tube end (11) and an outlet tube end (12) and is configured for receiving the liquid mixture from the mixing zone (4) through the inlet tube end (11), and comprises perforations (13) in the tube wall (16) to allow gaseous NH3 from the shell space (8) to enter the tube; and - a reaction zone (14) downstream of the outlet end of the tube (12), which zone preferably comprises a second type static mixer (15).
  2. 2. The reaction unit according to claim 1, wherein the mixing zone (4) comprises the first type static mixer (5) adapted to mix the recirculated ammonium nitrate solution with the aqueous nitric acid to form a liquid mixture, wherein said first type static mixer (5) in the mixing zone (4) upstream of the tube bundle (7) comprises: - a flow-diverting plate (201) which extends in a transversal direction perpendicular to the general liquid flow direction (F) in the mixing zone (4) and wherein in operation liquid impinges on the flow-diverting plate (201); - a first aperture (202) in the flow-diverting plate (201), - a circumferential flange (203) around the first aperture (202), wherein said flange (203) extends perpendicular to the plate (201) and has a first end that is joined to the plate (203a) and an opposite second end (203b); and - a transversal element (204), extending substantially parallel to the plate (201) and joined to said second end of the circumferential flange (203); such that the transversal element (204) and the flange (203) together provide a cup-like structure around the first aperture (202); wherein the circumferential flange (203) comprises a plurality of second apertures (205), wherein each second aperture (205) provides a smaller flow area than said first aperture (202).
  3. 3. The reaction unit according to claim 2, wherein the transversal element (204) comprises a third aperture (206), wherein the third aperture (206) provides a smaller flow area than said first aperture (202); preferably wherein the transversal element (204) comprises a plurality of third apertures (206).
  4. 4. The reaction unit according to claim 2 or 3, wherein the total flow area of the apertures in the flange (203) and in the transversal element (204) is at least 80 % of the flow area of the first aperture (202), preferably at least 100 %.
  5. 5. The reaction unit according to any of claims 2-4, wherein the transversal element (204) and the flange (203) together provide a perforated mixing cup (208).
  6. 6. The reaction unit according to any of claims 2-5, wherein the second apertures (205) in the flange (203) are configured to provide for a swirling motion of the liquid mixture in the transversal plane parallel to the plate (201), which swirling motion is diverging or converging.
  7. 7. The reaction unit according to any of claim 2-6, wherein the second aperture (205) is a skewed hole in the flange (203), wherein the second aperture (205) is an aperture that is at a non-zero angle relative to a local normal of the flange (203) at the position of the second aperture (205).
  8. 8. The reaction unit according to claim 1, wherein the reaction zone (14) comprises the second type static mixer (15; 701), wherein the second type static mixer is provided downstream of the outlet tube ends (12), wherein the reaction zone (14) has a generally vertically upward flow direction, and wherein the second type static mixer (701) comprises: - a horizontal gas redistribution plate (702) provided with a liquid passageway (704), e.g. an aperture, and a gas vent hole (711), - wherein each liquid passageway (704) is provided with a flange (708) extending downward from a perimeter of the liquid passageway (704), the plate (702) and flanges (708) together providing an interstice (715) configured for collecting gas from the outlet tube ends (12) in a gas layer or cushion (703) below the gas redistribution plate (702); wherein the reaction unit preferably also comprises the first type static mixer, which preferably is as defined in any of claims 2-7.
  9. 9. The reaction unit according to claim 8, comprising a plurality of said liquid passageways (704), each provided with said flange (708), and comprising a plurality of said gas vent holes (711), wherein the total flow area of the gas vent holes (711) is less than 5% of the total flow area of the liquid passageways (704), preferably less than 1%.
  10. 10. The reaction unit according to claim 9, wherein the flanges (708) each extend at least 5 cm down from the gas redistribution plate (702).
  11. 11. The reaction unit according to any of claims 8-10, wherein the flange (708) comprises an opening, e.g. an aperture or notch, in a distal part of the flange, wherein the distal part is arranged distal from the plate (702).
  12. 12. A reactor (900) comprising the reaction unit (100; 901) according to any of claims 1-11 and - a gas/liquid separation zone (902) receiving an effluent from the reaction unit (901), - a liquid flow line (903) from said separation zone (902) to an inlet of the reaction unit (901) for recirculation of ammonium nitrate solution to said first inlet of the inlet zone (1); - a gas outlet (904) for gas from the separation zone (902); and - a liquid outlet (905) for product AN solution from the separation zone (902).
  13. 13. The reactor according to claim 12, wherein the reactor (901) comprises a pressure reduction means (906), e.g. a restriction orifice or valve, preferably a restriction orifice, between the reaction zone (14) and the gas/liquid separation zone (902); and a pump (910) in the liquid flow line for recirculated AN solution.
  14. 14. A process for the production of ammonium nitrate by neutralization of aqueous nitric acid with gaseous NH3 carried out in a reaction unit (100; 901) according to any of claims 1-11 or a in the reactor (900) according to any of claims 12-13.

Description

P135711PC00 Title: AMMONIUM NITRATE REACTOR WITH STATIC MIXER Field [0001] Embodiments of the invention pertain to a reactor and process for reacting aqueous nitric acid (NA) with gaseous NH3 to form an ammonium nitrate (AN) solution, with recirculation of a part of the AN solution. Gaseous NH3 is admitted to a mixture of aqueous nitric acid and ammonium nitrate through perforations of tubes. Introduction [0002] Ammonia reacts rapidly and completely with nitric acid in aqueous solutions to form AN in an exothermic reaction. In AN production, an amount of AN solution is recycled and serves as a buffer to the reaction heat. The recycle ratio depends on the maximum allowable reaction temperature (for instance, ranging from 125 to 185ºC) and is, for example, in the range 5 – 40 as mass ratio of recycled solution to AN product purge. Frequently forced flow of the solution is used, i.e. with a pump. [0003] The recycled aqueous ammonium nitrate solution for instance comprises at least 80 wt.% AN, e.g. up to 92 wt.% AN. The feed nitric acid solution contains e.g. about 60 wt.% NA and balance essentially water. Nitric acid is typically produced in an adjacent Ostwald process where NH3 is reacted with O2 to form nitric oxides that are absorbed in an aqueous stream under the formation of nitric acid to give nitric acid aqueous solution. NA concentrations up to 68% (azeotropic mixture) can be reached normally, higher concentrations require special measures. [0004] G.R. Maxwell, Synthetic Nitrogen Products (2005), p.251-265, chapter Ammonium Nitrate, doi: 10.1007/0-306-48639-3_10 describes various processes and apparatuses for AN production. A further background reference is Ullmann's Encyclopedia of Industrial Chemistry, chapter Ammonium Compounds, 2000, doi:10.1002/14356007.a02_243. [0005] An example reactor for the production of AN is described in AU654632B1. The described vertical reactor comprises a bottom cone for receiving recycled ammonium nitrate solution, said cone having injection nozzles for introducing aqueous nitric acid for admixture with the recycled ammonium nitrate solution; a premixing zone located adjacent and above said bottom cone and adapted to receive the admixture and initially mix the recycled ammonium nitrate solution and aqueous nitric acid; a final mixing zone located adjacent and above said premixing zone and adapted to receive and homogeneously mix the premixed recycled ammonium nitrate solution and aqueous nitric acid; a downstream tubed chamber located adjacent and above the final mixing zone, said chamber containing a bundle of perforated tubes for introducing the ammonia containing gas for admixture with the mixed recycled ammonium nitrate solution and aqueous nitric acid in a gas-to-liquids admixing zone; and a reaction chamber located adjacent and above the downstream tubed chamber. The reactor internals are arranged in a manner such that the initial liquid mixture passes (typically in an upward direction) through the mixing zone, the final mixing zone, the gas-to-liquids admixing zone provided by the perforated tubes, and the reaction zone. Gaseous ammonia is admitted, under pressure, to the shell space of the tube bundle, which is essentially closed by a bottom and top tube plates (which tube plates may contain minor venting holes). The tubes extend through the tube plates. The tubes are provided with penetration holes and the gaseous NH3 enters through the holes of the tube into the tube sides in the liquid phase. A provision is made for flash evaporation of steam downstream of the reactor. In order to reduce ammonia losses by the flash vapor, the ammonium nitrate solution in the reaction loop is adjusted so as to obtain a small surplus of acid. The document mentions that a sophisticated type of reactor is required to permit a homogenous reaction, a uniform heat distribution over the entire cross-sectional area of the reactor as well as lower nitrogen losses and to deploy suitable materials of construction. [0006] In AU654632B1, downstream of the acid injection device a premixing zone is provided (0.5 to 3 m in length), followed by 1-4 static mixing elements (described as multi-orifice plates, packings, fluid mixers; also referred to as premixing elements). The aim of the static mixer is to optimize the homogeneity of the acid distribution in the mixture. The coefficient of variance should range from 0.01 to 0.5. The finally mixed acidic ammonium nitrate solution enters a multitube reactor bundle (3-200 tubes). The individual tubes (inner diameter 50 to 200 mm) of the bundle have penetration holes diameter 1.5 to 5 mm) arranged in a spiral manner. The pressure inside the reactor bundle is 0.02-2.5 bar higher than the boiling point of the ammonium nitrate solution at the given temperature. Reaction zones, downstream of the tube bundle, followed by a post-mixing element similar to the premixing elements ensure completion of the reaction so that the nitrogen losses are very low d