US 11,746,084 B2
Ferritic steel parts in urea plants
Kirk Anguah Ofei, Eindhoven (NL); and Alexander Aleida Antonius Scheerder, Roosteren (NL)
Assigned to STAMICARBON B.V., Sittard (NL)
Appl. No. 17/624,716
Filed by STAMICARBON B.V., Sittard (NL)
PCT Filed Jul. 3, 2020, PCT No. PCT/NL2020/050438
§ 371(c)(1), (2) Date Jan. 4, 2022,
PCT Pub. No. WO2021/006729, PCT Pub. Date Jan. 14, 2021.
Claims priority of application No. 19184798 (EP), filed on Jul. 5, 2019.
Prior Publication US 2022/0251032 A1, Aug. 11, 2022
Int. Cl. C07C 273/04 (2006.01); C07C 273/16 (2006.01); B01D 1/06 (2006.01); B01D 3/34 (2006.01); B01J 19/00 (2006.01); B01J 19/02 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/04 (2006.01); C22C 38/42 (2006.01); C22C 38/44 (2006.01); C22C 38/48 (2006.01); C22C 38/26 (2006.01); B22F 7/06 (2006.01)
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
OG exemplary drawing
 
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).
 
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).