Assessment of the Corrosivity of Crude Fractions from Varying Feedstock

Abstract Crude corrosivity is becoming a critical issue because of frequent variation of feedstock based on spot market opportunities and high sulfur and naphthenic acid content of low cost crudes. The choice of remediation methods (blending, inhibition, upgrading, and/or process changes) depends on accurate prediction of the corrosivity of these crudes. This paper presents the results of autoclave and flow loop runs conducted to assess the corrosivity of Middle East, Shengli, and Bachequero-13 crudes fractions on several materials used in refinery construction. Autoclave tests were conducted in vacuum heater feed line (VHFL) and Asphalt’s fractions from each crude and in atmospheric gas oil (AGO) and heavy vacuum gas oil (HVGO) from the Bachequero-13. Flow loop tests were conducted only on the VHFL’s of each crude. As expected, the test results showed a major increase in corrosion rate with increasing temperature. Corrosion rates were generally less than 10 mpy for all materials at up to 300 C. At 400 C, corrosion rates on the low Cr steels (0 to 5 Cr) were generally around 100 mpy. For the Middle East and Shengli oils, the asphalt’s were more corrosive than the VHFL cuts. Only slight differences were found in the corrosivity of these two oils. By comparison, the Bachequero-13 fractions were generally more corrosive than those from the Shengli or the Middle Eastern crudes. At 200 ft/s (67 m/s), the corrosion rates of the carbon steel specimens were high in the Middle Eastern fraction compared to the Bachequero-13 and Shengli fractions.