Problem No. 52: High nickel content in high pressure urea synthesis

The detection of active corrosion in a urea plant is difficult. Local corrosion can hardly be detected unless leak detection systems or conductivity measurements in steam/condensate systems are used. Overall corrosion however can be detected in the warehouse by checking for discoloration (reddish colour) of the product or via analyses of the urea final product.

In many plants, product analyses are used to verify the condition of the plant. An element that is often analysed is nickel because it is a reliable parameter to verify local active corrosion in a urea plant. Nickel is present in the stainless steel that protects the pressure vessels and as an alloying component in the HP piping. Since there is ongoing corrosion in the synthesis section, there is always some nickel present in the final product.