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EP-4455079-B1 - AMMOXIDATION REACTOR AND METHOD FOR PRODUCING NITRIC ACID

EP4455079B1EP 4455079 B1EP4455079 B1EP 4455079B1EP-4455079-B1

Inventors

  • ZHOU, JUN
  • WANG, Jining
  • ZHAO, Shiping
  • HAN, FANG
  • WANG, JUNTING
  • YANG, LU
  • SUN, LIN
  • WU, ZHIJUN

Dates

Publication Date
20260506
Application Date
20221219

Claims (14)

  1. An ammonia oxidation reactor (1000) for the producing of nitric acid, wherein it comprises a shell (200) and a top cover (400) over said shell (200) to form a furnace chamber (300); said furnace chamber (300) comprising a first space and a second space which are connected in an upward and a downward direction; a combustion unit (500), which is located in said first space and comprises a platinum mesh layer (501), wherein a combustion reaction is performed in the medium of said platinum mesh layer (501) until the temperature of said platinum mesh layer (501) is sufficient to oxidise ammonia gases entering into said furnace chamber (300) to produce nitrogen oxides; and a heat recycling unit (100), which is located in said second space, for recycling heat from a hot gas stream generated by combustion of said combustion unit (500) inside said first space and migrating to said second space; said heat recycling unit (100) comprising at least two coil assemblies (1); wherein two of said coil assemblies (1) are provided at different heights inside said furnace chamber (300) along an axial direction of said furnace chamber (300); and two of said coil assemblies (1) are connected in parallel between an inlet header (2) and an outlet header (3); said coil assembly (1) comprising a plurality of coils (11) disposed in the axial direction along said coil assembly (1); said coil (11) is connected to a first inlet guide tube (113) and a first outlet guide tube (114) at both ends separately; said first outlet guide tube (114) of said coil (11) at the upper level is in the axial direction of said coil assembly (1) corresponding to the first inlet guide tube (113) of said coil (11) at the lower level; said first inlet guide tube (113) is connected to said inlet header (2), said first outlet guide tube (114) is connected to said outlet header (3); in the horizontal plane of said coil (11), said coil (11) is coiled from first inlet guide tube (113) from outside to inside in a first direction in an equidistant helix to form a plurality of first coil rings (111) of different circle diameters and said coil (11) is internally bent into an "S" shape and then coiled from inside to outside in a second direction in an equally spaced helix to form a plurality of second coil rings (112) of different circle diameters; said second coil ring (112) is located between two adjacent said first coil rings (111); wherein the first direction is opposite to the second direction; said combustion unit (500) comprises an ignition assembly (54); wherein said ignition assembly (54) comprises an igniter (541), an ignition distributor tube (542) and an ignition gas tube (543); wherein said igniter (541) ignites an ignition gas passed through said ignition gas tube (543) and ignites the entire layer of said platinum mesh by using said ignition distributor tube (542).
  2. The ammonia oxidation reactor (1000) according to claim 1, wherein said heat recycling unit (100) further comprises a water-cooled wall tube group (4); said water-cooled wall tube group (4) is circumferentially disposed inside the furnace chamber (300) closely adjacent to said shell (200); and said water-cooled wall tube group (4) is disposed around the outer circumference of said coil assembly (1).
  3. The ammonia oxidation reactor (1000) according to claim 1, wherein said coil assembly (1) comprises a plurality of fixing assemblies, one said fixing assembly (12) being disposed on each of said coils (11); said fixing assembly (12) comprising a plurality of tie members (121); each of the plurality of tie members (121) being disposed radially circumferentially in the plane of said coils (11) and wrapped around the exterior of said coils (11) to tie down said coils (11).
  4. The ammonia oxidation reactor (1000) according to claim 3, wherein said fixing assembly (12) comprises an position adjustment assembly (122), said position adjustment assembly (122) comprising: a plurality of first position adjustment assemblies; the plurality of first position adjustment assemblies are radially disposed in the plane of said coil (11); said first position adjustment assembly (1221) comprises a plurality of first locating members (12211) radially disposed in the same orientation; said first locating members (12211) are disposed in the gap between said first coil ring (111) and said second coil ring (112); said first locating members (12211) comprise two first locating blocks (122111) disposed back-to-back; two said first locating blocks (122111) are semi-enclosed to said first coil ring (111) and said second coil ring (112) separately; and a plurality of second position adjustment assemblies; the plurality of second position adjustment assemblies being radially disposed in the plane of said coil assembly (1); said second position adjustment assembly (1222) comprises a plurality of second locating members (12221) radially disposed in the same orientation; said second locating members (12221) being disposed in the gap between said first coil ring (111) and said second coil ring (112); said second locating member (12221) comprises two backwardly disposed second locating blocks (122211); said second locating blocks (122211) being semi-enclosed to said first coil ring (111) and said second coil ring (112); wherein in the horizontal plane of said coil (11) said first position adjustment assembly (1221) and said second position adjustment assembly (1222) are located on both sides of said tie member (121) separately; said first locating member (12211) and said second locating member (12221) are both disposed apart within the gap between said first coil ring (111) and said second coil ring (112), and said first locating member (12211) and said second locating member (12221) are disposed alternately within the gap formed by said first coil ring (111) and said second coil ring (112).
  5. The ammonia oxidation reactor (1000) according to any one of claims 1-4, wherein said coil assembly (1) comprises a plurality of airflow dispersing members (13), each said coil (11) is disposed with one said airflow dispersing member (13) above each said coil (11); said airflow dispersing member (13) corresponding to said "S" shaped structure in the axial direction of said coil assembly (1), said airflow dispersing member (13) shields said "S" shaped structure.
  6. The ammonia oxidation reactor (1000) according to claim 5, wherein said inlet header (2) is equipped with at least two throttle hole joints; each of two said throttle hole joints connects two said coil assemblies (1) separately; said water-cooled wall tube group (4) comprises; a plurality of water-cooled wall tubes (41); the plurality of water-cooled wall tubes (41) disposed side by side in an equal-pitch spiral coil (11) in an axial direction along said furnace chamber (300); each said water-cooled wall tube (41) is provided with a second inlet guide tube (411) and a second outlet guide tube (412) at each end; outlet centralise tube (42), said second outlet guide tube (412) on each of said water-cooled wall tubes (41) connects to said outlet centralise tube (42) separately; and inlet centralise tube (43), said second inlet guide tube (411) on each of said water-cooled wall tubes (41) connects to said inlet centralise tube (43) separately; the highest point of the plurality of water-cooled wall tubes (41) axially upwardly of said furnace chamber (300) is in the same plane.
  7. The ammonia oxidation reactor (1000) according to claim 2, wherein said heat recycling unit (100) comprises a guard cylinder (45); said guard cylinder (45) is disposed on an outer circumferential edge of said coil assembly (1) and said guard cylinder (45) is disposed between said coil assembly (1) and said water-cooled wall tube group (4).
  8. The ammonia oxidation reactor (1000) according to claim 5, wherein said combustion unit (500) further comprises a support assembly (51) for supporting and fixing said platinum mesh layer (501); said support assembly (51) comprises a support member, said support member being disposed below said platinum mesh layer (501) for supporting said platinum mesh layer (501).
  9. The ammonia oxidation reactor (1000) according to claim 8, wherein said support assembly (51) further comprises an elastic compression member, said elastic compression member comprises a gasket (513), an inverted T-shaped support ring (517), an elastic snap ring (516) and a cylinder section (514); wherein a gasket (513) is provided at the top and bottom of said platinum mesh layer (501); wherein said inverted T-shaped support ring (517) is located on the exterior of said hollow circular cylinder section (514); wherein an elastic snap ring (516) is disposed on top of said inverted T-shaped support ring (517); wherein the central axes of said inverted T-shaped support ring (517), said elastic snap ring (516) and hollow circular of said cylinder section (514) are overlapping; wherein a press strip (401) is disposed in said top cover (400), said press strip (401) is connected with said elastic snap ring (516); said inverted T-shaped support ring (517) comprises a support circle (515) and a support ring (517); wherein said support circle (515) is fixedly disposed on the exterior hollow circular of said cylinder section (514); said support ring (517) is fixedly disposed above said support circle (515); and said resilient snap ring is disposed above said support ring (517); said support circle (515) is welded and fixed on the outside of said cylinder section (514); the diameter of said support ring (517) is smaller than the diameter of said support circle (515), said support ring (517) is vertically welded and fixed to the middle of said support circle (515); said resilient snap ring is snapped to said support ring (517), said resilient snap ring has a gap between said resilient snap ring and said cylinder section (514), and said resilient snap ring has a diameter larger than the diameter of said support circle (515); said cylinder section (514) is a high temperature resistant alloy; a platinum mesh compression ring (511) is disposed between said gasket (513) and said cylinder section (514).
  10. The ammonia oxidation reactor (1000) according to claim 9, wherein said support assembly (51) at least comprises a base (512), said base (512) being disposed below the outer edge of said platinum mesh layer (501); said support assembly (51) further comprises a grid support frame (502), said grid support frame (502) is disposed below said platinum mesh layer (501); said combustion unit (500) further comprises a gas distributor (52); wherein said gas distributor (52) is disposed inside said furnace chamber (300); said combustion unit (500) further comprises a deflector cone (53); wherein said deflector cone (53) is disposed on said top cover (400) and is located in said chamber, and wherein said gas distributor (52) is disposed in said deflector cone (53) for evenly distributing a mixture of ammonia gas and air to said platinum mesh layer (501).
  11. The ammonia oxidation reactor (1000) according to claim 1, wherein said top cover (400) is equipped with at least one observation window (55) for observing the combustion situation in said furnace chamber (300); said top cover (400) is equipped with a protective air duct; for passing protective gas into said furnace chamber (300) to prevent high temperatures in the dead zone.
  12. A method for producing nitric acid, wherein an ammonia oxidation reactor as claimed in any one of claims 1-11 is utilised for the production of nitric acid.
  13. The method according to claim 12, wherein the method comprises the following steps; igniting the ammonia gas entering the furnace chamber (300) on the platinum mesh layer (501) using an ignition assembly (54) and oxidising the ammonia gas, to obtain a gaseous hot gas stream containing nitrogen oxides; in the process using the gravitational force of the top cover (400) itself to press down the end of the resilient ring away from the cylinder section to form an elastic deformation according to the contact between the pressure strip (401) inside said top cover (400) and the resilient snap ring, to achieve sealing and pressurising at the same time; the hot gas after the reaction flow passes through the second space of at least two coil assemblies (1, 11) in the furnace chamber (300) in a downward sequence, exchanging heat between the hot airflow and the medium in the coil assembly (1), with the guard cylinder makes the hot airflow maximally through the layers of the coil from top to bottom sequentially, and utilize airflow dispersing member (13) to shield the "S"-shaped structure of the middle layers of the coil preventing the hot airflow from the "S"-shaped structure downward transmission to form airflow short circuit; at the same time, use the water-cooled wall tube group (41) to reduce the wall temperature of the shell.
  14. The method according to claim 12, wherein hot gas stream after said reaction has a temperature of 800-1000°C, an outlet temperature of 350-450°C after heat exchange with said coil assembly (1); said furnace chamber (300) inlet gas is an ammonia-air mixture comprising ammonia and air; said ammonia-air mixture is at a temperature of 200-400°C, and wherein the molar volume ratio of ammonia is 8-12% based on said ammonia-air mixture.

Description

TECHNICAL FIELD The application relates to the technical field of nitric acid producing equipment, and in particular relates to an ammonia oxidation reactor and method for producing nitric acid. BACKGROUND Ammonia oxidation reactor is the equipment that ammonia and oxygen produce nitrogen oxides via catalytic reaction. According to the different production pressures, the produce of nitric acid in ammonia oxidation reactors can be classified as atmospheric pressure, medium pressure, high pressure and double pressurisation. The production of nitric acid basically involves: the first step of oxidising gaseous ammonia with air over a suitable catalyst to obtain a gaseous product containing oxides of nitrogen; and the second step of contacting the gaseous product with water in order to absorb the above mentioned oxides and obtain HNO3. The first step of ammonia oxidation is usually carried out under pressure in a suitable vessel (further known as a burner or combustion reactor). The catalyst is typically a platinum wire mesh which is supported by baskets within the reactor or, if necessary, contains under the mesh a high temperature resistant packing support or a high temperature resistant catalyst for N2O reduction. In operation, the ammonia-air mixture enters the reactor from the top entrance, passes through the gas distributor, and is evenly distributed in the platinum network to generate a mixture of nitric oxide and water vapour, and release a large amount of heat. At the same time, in order to reduce the impact of high temperature on the equipment chamber and equipment flange, the equipment is covered with a layer of water-cooled walls in the inside wall; the existing distributor distribution is not uniform, resulting in bias flow leading to inadequate burning reaction, and likely to cause the platinum mesh and platinum mesh under the temperature of the uneven radial distribution of the affected nitrogen monoxide production yield. In addition, in order to achieve the efficiency of the heat in the ammonia oxidation reactor, a heat recovery device is set up in the ammonia oxidation reactor, and a water-cooled wall module is set up in order to prevent damage to the equipment from excessively high temperatures; wherein the coiled tube module for the heat recovery device consists of a multi-layer coiled tubes that are connected in the direction of head to tail and are arranged in a upright direction, and each layer of the coiled tubes is a seamless tube coiled at an equal spacing and each layer of the coiled tubes is coiled in the same way. According to the installation position of each layer of coiler in the ammonia oxidation reactor, the temperature absorption is also different, the heat absorption of heat is also different, at the same time, with the use of ammonia oxidation reactor age increasing, each layer of the level of coiler can not maintain the original winding state resulting in the phenomenon of uneven heat transfer and the reduction of the heat transfer efficiency. In summary, the existing ammonia oxidation reactor for the producing of nitric acid presents high ammonia consumption, high platinum catalyst consumption, high energy consumption, low heat recycling rate, and short service life. Some relevant prior art documents are CN 111 892 025 A, CN 102 424 370 B, CN 213 505 991 U. SUMMARY The present application is intended to address, at least in part, one of the technical problems in the related technology. The essential features of the invention are laid out in independent device claim 1 and method claim 12. Further, preferred embodiments are described in dependent claims 2-11 and 13-14. In some embodiments, said heat recycling unit further comprises a water-cooled wall tube group; said water-cooled wall tube group is circumferentially disposed inside the furnace interior close to said shell; and said water-cooled wall tube group is disposed at an external circumferential periphery of said coil assembly. In some embodiments, said coil assembly comprises a plurality of fixing assemblies, each said coil being provided with one said fixing assembly; said fixing assemblies comprising a plurality of tie-downs; the a plurality of said tie-downs each being provided radially circumferentially in the plane of said coil and wrapped around the exterior of said coil to tie down said coil. In some embodiments, said fixing assembly comprises an position adjustment assembly, said position adjustment assembly comprising: a plurality of first position adjustment assemblies; a plurality of said first position adjustment assemblies are each arranged radially in the plane of said coil; said first position adjustment assemblies comprise a plurality of first locating members arranged radially along the same orientation; said first locating members are located in the space between said first coil ring and said second coil ring; said first locating members comprise two first locating blocks arranged backwardly; two the