USE OF DUPLEX STAINLESS STEEL IN AN AMMONIA-STRIPPING OF UREA PLANTS

摘要

In an ammonia stripping or self-stripping plant for the synthesis of urea, it is disclosed that a shell-and-tube stripper has a bundle of tubes made of a duplex stainless steel 29Cr-6.5Ni-2Mo—N according to UNS S32906 or 27Cr-7.6Ni-1 Mo-2.3W—N according to UNS S32808. A revamping of urea plants is also disclosed, including the revamping of ammonia stripping plants, self-stripping plants and conventional total recycle plants, wherein said duplex stainless steel is used for the tubes of the stripper.

主权项

1. A shell-and-tube stripper, for use in an ammonia stripping plant or self-stripping plant for the synthesis of urea, said stripper comprising a shell and a bundle of tubes, and being arranged to provide the stripping of a carbamate solution fed to said tubes by means of heat and optionally by means of ammonia as a stripping medium, said stripper being characterized in that the tubes are made of a duplex stainless steel which is one of the following:
A) the Safurex® steel 29Cr-6.5Ni-2Mo—N, which is also designated by ASME Code 2295-3 and by UNS 532906,
or: B) the DP28W™ steel 27Cr-7.6Ni-1Mo-2.3W—N, which is also designated by ASME Code Case 2496-1 and by UNS 532808.