Control corrosion factors in ammonia and urea plants

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n the hydrocarbon processing industry (HPI), the manufacture of ammonia and urea holds a prominent role. These petrochemicals have sustained the growth of agricultural production with new technologies and processes. This industry uses many different feedstocks such as coal,liquid petroleum, natural gas, and refinery residues. These feeds are processed under extreme pressure and temperatures in a highly corrosive environment. Despite these processing challenges, large-scale fertilizer plants are built worldwide to meet the growing fertilizer demand. A major factor contributing to this achievement is the industry’s success in combating corrosion. Adopting modern corrosion-abatement techniques and applying new generation / improved materials of construction have effectively mitigated process corrosion factors. Better materials of construction. Over the past two decades, the ammonia and urea industry have witnessed spectacular metallurgical developments for process equipment. For example,stainless steels, modified with special materials, can improve hightemperature creep rupture resistance. Using duplex stainless steels and modern corrosion abatement techniques are other methods that improve plant-operating performance. Urea or carbamide – a source of nitrogen – is the major fertilizer material and is produced from ammonia (NH3) and carbon dioxide (CO2). Current global production is approximately 100 million tpy. Urea manufacture consumes nearly 90% of all ammonia produced.Ammonia is produced by the synthesis of elemental hydrogen and nitrogen; it is an energyintensiveprocess. The most cost-effective ammonia synthesis reaction uses fossil fuels. Thus,ammonia synthesis uses feedstocks such as coal, naphtha, fuel oil, natural gas, etc. Suchprocessing routes involve severe operating environments that are highly corrosive. Specialmaterials are needed to fabricate process equipment and pipelines.