CPC C07C 273/04 (2013.01) [B01D 1/065 (2013.01); B01D 3/346 (2013.01); B01J 19/0013 (2013.01); B01J 19/02 (2013.01); C07C 273/16 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/26 (2013.01); C22C 38/42 (2013.01); C22C 38/44 (2013.01); C22C 38/48 (2013.01); B01J 2219/00081 (2013.01); B01J 2219/0286 (2013.01); B22F 7/064 (2013.01); B22F 2301/35 (2013.01); C21D 2211/005 (2013.01)] | 7 Claims |
1. A process for producing urea in a urea plant comprising a high pressure synthesis section comprising a reactor, wherein the process comprises reacting an NH3 feed and a CO2 feed under urea formation conditions in said reactor to form a urea synthesis solution comprising urea, water, carbamate and ammonia, wherein the process further comprises contacting a carbamate-containing liquid stream with an equipment part of said high pressure synthesis section that is made of a ferritic steel alloy comprising in wt. %:
C max. 0.005
Si 0.1 to 0.4
Mn max. 0.4
P max. 0.020
S max. 0.020
Cu max. 0.25
Ni max. 0.50
Cr 20.0 to 35.0
Mo 0.75 to 1.50
N 0.0050 to 0.0125
Nb 0.060 to 0.375
balance Fe, max. 0.50 wt. % total added processability elements, and impurities, and wherein the amount of Nb in wt. % meets the following equation 12*(wt. % N)<Nb<30*(wt. % N).
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7. A method of exposing ferritic stainless steel in a ammonium carbamate environment, said method comprising exposing the steel to a fluid comprising ammonium carbamate, the ferritic steel comprising in weight % (wt %):
C max. 0.005,
Si 0.1 to 0.4
Mn max. 0.4
P max. 0.020
S max. 0.020
Cu max. 0.25
Ni max. 0.50
Cr 20.0 to 35.0
Mo 0.75 to 1.50
N 0.0050 to 0.0125
Nb 0.060 to 0.375
balance Fe, max. 0.50 wt. % total added processability elements, and impurities, and wherein the amount of Nb in wt. % meets the following equation 12*(wt. % N)<Nb<30*(wt. % N).
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