METHOD FOR THE CATALYTIC OXIDATION OF AMMONIA GAS

Abstract

A process for catalytic oxidation of ammonia gas by way of an oxygen-containing gas in a presence of a noble metal-containing catalyst may be employed to give nitrogen monoxide. A temperature of an ammonia/air mixed gas may be optimized in respect of nitrogen monoxide selectivity of the reaction before contact with the catalyst. Examination of catalytic NH.sub.3 oxidation according to 4NH.sub.3+5O.sub.2.fwdarw.4NO+6H.sub.2O revealed that an optimum mode of operation of an NH.sub.3 burner in an HNO.sub.3 plant is not to be achieved by maintenance of a constant gauze temperature of the catalyst gauze by automatic setting of the NH.sub.3: air ratio. Rather, there is an optimum temperature for each process condition that should be set not by changing the NH.sub.3: air ratio but instead by altering the temperature of the NH.sub.3/air mixed gas before contact with the catalyst gauzes.

Claims

1.-26. (canceled)

27. A process for catalytic oxidation of ammonia gas by way of an oxygen-containing gas in a presence of a catalyst to give nitrogen monoxide in an oxidation reactor, the process comprising regulating a reaction temperature at the catalyst to an optimum value with respect to nitrogen monoxide selectivity of a reaction, wherein the regulating is effected by way of measures upstream of the oxidation reactor.

28. The process of claim 27 wherein the oxygen-containing gas is air, the process comprising indirectly heating or cooling the air and/or the ammonia gas/air mixed gas before contact with the catalyst.

29. The process of claim 28 comprising indirectly heating the air and/or the ammonia gas/air mixed gas by way of steam or other heat transfer.

30. The process of claim 28 wherein the catalytic oxidation occurs in a plant comprising a process air compressor with an intermediate cooler and a regulated process air-side bypass around the intermediate cooler for setting an exit temperature of air exiting from the process air compressor.

31. The process of claim 27 wherein the oxygen-containing gas is air, the process comprising directly heating or cooling the air and/or the ammonia gas/air mixed gas before contact with the catalyst.

32. The process of claim 31 wherein the catalytic oxidation occurs in a plant comprising a process air compressor, the process comprising mixing a process air stream with a hot medium and/or a cold medium upstream or downstream of the process air compressor.

33. The process of claim 32 wherein the cold medium comprises at least one of demineralized water, liquid nitrogen, or cold water.

34. The process of claim 32 comprising mixing the hot medium or the cold medium with a total air stream or only with a primary air.

35. The process of claim 32 comprising heating by mixing in steam upstream of the process air compressor.

36. The process of claim 32 comprising heating or cooling the ammonia gas/air mixed gas by mixing in steam downstream of the process air compressor.

37. The process of claim 31 comprising heating the air and/or the ammonia gas/air mixed gas before contact with the catalyst via a fuel gas for increasing a burner temperature, wherein the fuel gas is introduced into an air stream in a region of a conduit upstream of an addition of the ammonia gas with combustion of the fuel gas.

38. The process of claim 31 comprising introducing a first fuel gas or a first medium that influences the reaction temperature upstream of the addition of the ammonia gas, with combustion of the fuel gas occurring at the catalyst in an ammonia burner.

39. The process of claim 38 comprising introducing a second fuel gas or a second medium that influences the reaction temperature downstream of the addition of the ammonia gas.

40. The process of claim 27 wherein the oxygen-containing gas is air, the process comprising indirectly heating or cooling the air and/or the ammonia gas/air mixed gas before contact with the catalyst, the process comprising at least one of: indirectly heating or cooling the air by way of a first indirect heat transfer before adding the ammonia gas; or indirectly heating or cooling the ammonia gas/air mixed gas by way of a second heat transfer after adding the ammonia.

41. The process of claim 27 wherein the catalytic oxidation occurs in a plant comprising a process air compressor where a change in a temperature of combustion air occurs via changing a setting parameter of the process air compressor.

42. The process of claim 27 comprising determining a value of a temperature of a catalyst gauze as a function of a modeling parameter using a regulating circuit to set an amount of heating or cooling medium fed in and/or to adjust a setting of a process air compressor.

43. The process of claim 42 comprising using a cascade regulation, with an output of a temperature regulator for the temperature of the catalyst gauze providing the value of the temperature for a flow regulator for the heating or cooling medium.

44. The process of claim 42 configuring a model for operation of a plant with respect to variations in amounts of the heating or cooling medium and/or changes in settings of the process air compressor using plant data and theoretical approaches, with a feed-forward regulation with feedback trim being used.

45. An apparatus for carrying out a process for catalytic oxidation of ammonia gas by way of an oxygen-containing gas in a presence of a catalyst to give nitrogen monoxide, wherein the apparatus comprises means for setting a temperature of the ammonia gas/air mixed gas before contact with the catalyst.

46. The apparatus of claim 45 wherein the oxygen-containing catalyst is air, the apparatus comprising a heating device and/or a cooling device for the air and/or the ammonia gas/air mixed gas that is disposed upstream of the catalyst.

47. The apparatus of claim 46 wherein the heating device comprises a heater installed in a primary air conduit for indirect heating of process air.

48. The apparatus of claim 45 comprising a process air compressor with an intermediate cooler, with a regulated process air-side bypass around the intermediate cooler for setting an exit temperature of air exiting from the process air compressor.

49. The apparatus of claim 45 comprising means for heating or cooling the ammonia gas/air mixed gas by mixing in steam upstream and/or downstream of a process air compressor.

50. The apparatus of claim 45 comprising means for introducing fuel gas to increase a burner temperature and heat air and/or the ammonia gas/air mixed gas before contact with the catalyst.

51. The apparatus of claim 45 comprising a regulating circuit for setting an amount of heating and/or cooling medium fed into a heating or cooling device and/or to adjust a setting a process air compressor.

52. The apparatus of claim 51 wherein the regulating circuit comprises a cascade regulation, with a temperature regulator for measuring a temperature of a catalyst gauze, wherein the temperature regulator is in active communication with a flow regulator for the heating and/or cooling medium.

Description

[0054] The present invention will be illustrated below with the aid of a working example with reference to the accompanying drawing. The drawing shows:

[0055] FIG. 1: a schematically simplified depiction of an illustrative apparatus according to the invention.

[0056] A working example of the present invention will be described in more detail below with reference to FIG. 1. The depiction schematically shows, in greatly simplified form, the elements essential to the present invention of a plant for the catalytic oxidation of ammonia gas. The plant comprises an ammonia burner 10, a conduit 11 for introduction of ammonia into the conduit system and a compressor 12 to which process air is fed via a conduit 13, so as to compress the process air to a prescribed pressure by means of the compressor 12. The compressed process air flows via a conduit 14 which goes out from the compressor 12 and into which a fuel gas 21, for example natural gas, is introduced via the conduit 15 and goes firstly to an indirect heat exchanger 16 in which a first regulation of the temperature of the process gas mixture is effected, in the working example before the addition of ammonia via the conduit 11 to the process gas mixture composed of air and fuel gas. Combustion can be effected by means of the fuel gas 21 fed in at 15, or media which allow the temperature of the process gas mixture to be influenced are fed in at 15.

[0057] After the addition of ammonia gas via the conduit 11, the process gas mixture flows via the conduit 17 through a further indirect heat exchanger 18 in which a second regulation of the temperature of the process gas mixture can be effected. The process gas mixture is subsequently fed via the conduit 19 to the ammonia burner 10, with, however, introduction of a further fuel gas 22, for example hydrogen, being able to be provided via the conduit 20 in order to assist the oxidation of the ammonia/air mixture at the catalyst. As an alternative, media which make it possible to influence the temperature of the process gas mixture can also be fed in via the conduit 20.

[0058] The process of the present invention thus makes it possible to set the reaction temperature of the process gas mixture at the catalyst in the ammonia burner to intended optimized values at a number of points, firstly by changing the air temperature at the compressor 12. A second possible way of influencing the temperature is the addition of fuel gas or other suitable media via the conduit 15. A third possible way of influencing the temperature is the use of an indirect heat exchanger 16 upstream of the addition of ammonia. A fourth possible way of influencing the temperature is the use of a further indirect heat exchanger 18 downstream of the addition of ammonia. A fifth possible way of influencing the temperature is the addition of a fuel gas or suitable media via the conduit 20 downstream of the second indirect heat exchanger 18 and upstream of the ammonia burner 10.

LIST OF REFERENCE NUMERALS

[0059] 10 Ammonia burner [0060] 11 Conduit for the addition of ammonia [0061] 12 Compressor for process air [0062] 13 Conduit for the addition of air [0063] 14 Conduit for process gas mixture [0064] 15 Conduit for the addition of a fuel gas [0065] 16 First indirect heat exchanger [0066] 17 Conduit for process gas mixture [0067] 18 Second indirect heat exchanger [0068] 19 Conduit for process gas mixture [0069] 20 Conduit for the addition of fuel gas [0070] 21 Fuel gas [0071] 22 Further fuel gas