Gas diffusion system and method for introducing a gas stream in an apparatus, in particular a passivating gas stream in a urea plant

49:

• The urea plant decomposer of claim 48, wherein the diffuser assembly defines a plurality of gas outlet openings arranged about the axis.

50:

• The urea plant decomposer of claim 49, wherein at least two of the plurality of gas outlet openings are at different distances from the axis.

51:

• The urea plant decomposer of claim 49, wherein the gas outlet openings define slots elongated longitudinally in a first direction.

52:

• The urea plant decomposer of claim 48, wherein the diffuser assembly includes a central diffuser located over the outlet of the gas feed conduit, said central diffuser is aligned with the outlet along the axis and defines a plurality of radial gas outlet openings uniformly spaced about the axis.

53:

• The urea plant decomposer of claim 52, wherein the central diffuser is positioned crosswise to the axis to obstruct the outlet from above and stop the passage of the passivating gas stream exiting from the outlet along the axis.

54:

• The urea plant decomposer of claim 52, wherein the central diffuser includes a dome-shaped hood having a peripheral edge spaced axially apart from the outlet and radially outwards with respect to the outlet.

55:

• The urea plant decomposer of claim 48, wherein the diffuser assembly includes a central diffuser and a peripheral shield, which are spaced axially apart along the axis and offset radially with respect to each other.

56:

• The urea plant decomposer of claim 55, wherein the shield includes an annular member positioned about the axis and defining a plurality of through peripheral openings, angularly spaced apart from one another and uniformly distributed around the axis.

57:

• The urea plant decomposer of claim 56, wherein the annular member has a radially inner peripheral edge and a radially outer peripheral edge which define a plurality of peripheral slots spaced angularly apart and defining the peripheral openings.

58:

• The urea plant decomposer of claim 56, wherein the annular member tapers upwards from the radially outer peripheral edge to the radially inner peripheral edge.

59:

• The urea plant decomposer of claim 52, wherein the central diffuser is associated with a distributor connected to the gas feed conduit to receive the passivating gas stream from the outlet of the gas feed conduit, said distributor being shaped to distribute at least part of the oncoming passivating gas stream radially to the central diffuser.

60:

• The urea plant decomposer of claim 59, wherein the distributor is an axial distributor extending along or parallel to the axis, said axial distributor receives the passivating gas stream from the gas feed conduit along the axis.

61:

• The urea plant decomposer of claim 60, wherein the axial distributor includes a tubular member extending along the axis and defining a plurality of longitudinal slits formed through a lateral wall of the tubular member and parallel to one another and to the axis.

62:

• The urea plant decomposer of claim 61, wherein the slits are angularly spaced and uniformly distributed around the axis and elongated parallel to the axis.

63:

• The urea plant decomposer of claim 59, wherein the central diffuser surrounds the distributor along the axis.

64:

• The urea plant decomposer of claim 59, wherein the central diffuser includes a hollow body defining an inner seat bounded by a wall surrounding the distributor, said distributor being housed in the inner seat.

65:

• The urea plant decomposer of claim 64, wherein the central diffuser defines a plurality of radial gas outlet openings formed through the wall and defined by respective vertically elongated slots.

66:

• The urea plant decomposer of claim 64, wherein the central diffuser defines:
• a first set of slots located on a top dome-shaped portion of the hollow body above a horizontal centreline plane of the hollow body and uniformly spaced about the axis, and
• a second set of slots located on a bottom dome-shaped portion of the hollow body below the horizontal centreline plane of the hollow body and uniformly spaced about the axis.

67:

• The urea plant decomposer of claim 48, wherein the diffuser assembly includes a radial diffuser extending radially with respect to the axis.

68:

• The urea plant decomposer of claim 67, wherein the radial diffuser includes a plurality of arms uniformly spaced about the axis and which project radially from a distributor and which each define a plurality of downward-facing bottom gas outlet openings defined by respective slots spaced axially apart along said arm and located on a bottom portion of said arm.

69:

• The urea plant decomposer of claim 68, wherein the slots on each arm are elongated crosswise to the arm.

70:

• The urea plant decomposer of claim 67, wherein the radial diffuser is associated with a radial distributor extending along the axis and which receives the passivating gas stream from the outlet of the gas feed conduit and radially distributes the passivating gas stream to the radial diffuser.

71:

• The urea plant decomposer of claim 70, wherein the radial distributor is located at the outlet of the gas feed conduit and defines:
• an axial inlet aligned along the axis and in communication with the outlet, and
• a plurality of radial outlets angularly spaced apart from one another and uniformly distributed about the axis.

72:

• The urea plant decomposer of claim 48, wherein the diffuser assembly includes an annular central diffuser ring-shaped about the axis and which defines a plurality of downward-facing bottom gas outlet openings uniformly distributed about the axis.

73:

• The urea plant decomposer of claim 72, wherein the downward-facing bottom gas outlet openings are slots radially elongated with respect to the axis.

74:

• The urea plant decomposer of claim 72, wherein the annular central diffuser is connected to a radial distributor.

75:

• The urea plant decomposer of claim 74, wherein the annular central diffuser includes a hollow toroidal body which defines a plurality of inlets spaced angularly apart, facing the axis and connected to respective arms of a radial diffuser.

76:

• The urea plant decomposer of claim 48, wherein the fitting projects perpendicularly from the base pipe.

77:

• The urea plant decomposer of claim 76, wherein the gas feed conduit is substantially T-shaped.

78:

• The urea plant decomposer of claim 48, wherein the base pipe includes at least two portions of at least one of:
• different cross sections to one another and eccentric with respect to one another.

79:

• The urea plant decomposer of claim 48, wherein the diffuser assembly defines at least one drain hole formed in one or more bottom end portions of the diffuser assembly to drain off any liquid penetrating the diffuser assembly.

80:

• The urea plant decomposer of claim 48, wherein the diffuser assembly includes at least one support which axially supports and angularly locks the diffuser assembly, said support including a bracket which defines a seat which receives a bottom end portion of the diffuser assembly resting axially on the bracket, inside the seat, the diffuser assembly having at least one fastener having two downward-facing lateral shoulders which cooperate with respective lateral edges of the seat.

81:

• The urea plant decomposer of claim 80, wherein the seat defines at least one drain hole formed through the bracket at the bottom of the seat to drain off any liquid collecting inside the seat.

82:

• The urea plant decomposer of claim 48, wherein the base pipe is perpendicular to the substantially cylindrical lateral wall and the axis.

83:

• The urea plant decomposer of claim 48, wherein the outlet is perpendicular to the axis.

84:

• The urea plant decomposer of claim 48, wherein said diffuser assembly is shaped to divert the passivating gas stream uniformly about the axis.

86:

• The method of claim 85, which includes distributing the passivating gas stream about the axis via a plurality of gas outlet openings uniformly spaced about the axis.

87:

• The method of claim 86, wherein the gas outlet openings are located at different distances from the axis.

88:

• The method of claim 86, wherein the gas outlet openings are slots elongated longitudinally in a first direction.

89:

• The method of claim 85, which includes stopping the passage of the passivating gas stream exiting from the outlet along the axis.

90:

• The method of claim 85, which includes distributing the passivating gas stream into a plurality of peripheral openings angularly spaced apart from one another and uniformly distributed around the axis.

91:

• The method of claim 85, which includes diffusing the gas stream via a plurality of arms uniformly spaced about the axis and each arm defines a plurality of downward-facing bottom gas outlet openings defined by a plurality of slots spaced axially apart along said arm and located on a bottom portion of said arm.

92:

• The method of claim 91, wherein the slots on each arm are elongated crosswise to the arm.

93:

• The method of claim 85, which includes radially distributing the passivating gas stream from the outlet via a plurality of radial outlets angularly spaced apart from one another and uniformly distributed around the axis.

94:

• The method of claim 85, which includes diffusing the gas stream via an annular central diffuser ring-shaped about the axis and defining a plurality of downward-facing bottom gas outlet openings uniformly spaced about the axis.

95:

• The method of claim 94, wherein the gas outlet openings are slots radially elongated with respect to the axis.

96:

• The method of claim 85, which includes draining off any liquid penetrating the diffuser assembly via at least one drain hole formed in at least one bottom end portion of the diffuser assembly.

97:

• The method of claim 85, wherein the passivating gas stream contains oxygen.

98:

• The method of claim 85, wherein the base pipe is perpendicular to the substantially cylindrical lateral wall and the axis.

99:

• The method of claim 85, wherein the outlet is perpendicular to the axis.

100:

• The method of claim 85, which includes diverting the passivating gas stream uniformly about the axis.