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Abstract

There is provided a urea synthesis method having excellent reliability and productivity with the amount of oxygen used as a corrosion-resistant agent minimized without using special duplex stainless steel. In a urea synthesis apparatus having a synthesis tower, a stripper, and a condenser, general-purpose austenitic-ferritic duplex stainless steel with Cr content: 21 to 26 wt %, Ni content: 4.5 to 7.5 wt %, Mo content: 2.5 to 3.5 wt %, N content: 0.08 to 0.30 wt %, C content: 0.03 wt % or less, Si content: 1.0 wt % or less, Mn content: 2.0 wt % or less, P content: 0.04 wt % or less, and S content: 0.03 wt % is used as a urea synthesis apparatus material in at least some of parts where the urea synthesis apparatus comes into contact with a fluid having corrosiveness, and oxygen feed concentration with respect to carbon dioxide is 100 to 2,000 ppm.

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