US EPA

7596583 

Meetings & Symposia 

Improve safety level urea plant shiraz petrochemical company by lowering passivation air 

Van Der Werf, J; Eijkenboom, J; Scheerder, A; Foolad, AR 

2006 

Vancouver, BC 

51st AIChE Safety in Ammonia Plants and Related Facilities Symposium 

47 

83-91 

English 

Shiraz Petrochemical Company (SPC) operates a Stamicarbon CO2 stripping urea plant since 1983 with a design plant capacity of 1500 mtpd near Shiraz in I.A. Iran. Early 2003 SPC installed the first Safurex® stripper in the world after experience was gained with Safurex® high efficiency trays in the urea reactor. As the high pressure carbamate condenser (HPCC) was made of BC.05 (X1CrNiMoN25-22-2) stainless steel, SPC offered the first opportunity to reduce the oxygen content in the CO2 from normally 0.6 vol.-% to 03 vol.-%. Stamicarbon and SPC agreed to perform a low oxygen test to prove this. The only reason to add oxygen is to passivate the stainless steels in the HP synthesis section in contact with the process medium. Having a Safurex® HP Stripper and a BC.05 HPCC less oxygen is needed for passivation. Lowering the oxygen level in a urea plant leads to an improvement of the safety level. The ultimate goal is to operate urea plant oxygen free, which is intrinsically safe. A pre-requisite is that all equipment in the high pressure synthesis section must be constructed in Safurex®. Lowering the oxygen level also leads to numerous other benefits such as lower energy consumption and lower investment figures. The low oxygen test at SPC is a milestone to realize an oxygen free and thus intrinsically safe urea plant. This paper presents the results of the low oxygen test at SPC both front process as well as from corrosion point of view. The low oxygen test demonstrated no increase in corrosion in the HP synthesis section. Process benefits were evident; increased reactor conversion, lower steam consumption in HP Stripper and lower ammonia emission. There are no limitations for the SPC plant to run the plant at 0.3 vol.-% oxygen. Based on this result, Stamicarbon specifies an oxygen content of 0.3 vol.-% in the CO2 feedstock in a Stamicarbon stripping plant when following pre-requisites are met: HP Stripper in Safurex® material quality (BE.06) HPCC/HP Pool Condenser in X1CrNMoN25-22-2 (BC.05) material quality. 

Chemical plants; Energy utilization; Oxygen; Passivation; Synthesis (chemical); High efficiency trays; Material quality; Reactor conversion; Shiraz Petrochemical Company (CO); Chemical industry