The objective of this research is to evaluate the fate of cyanide from generation during catalytic cracking to wastewater discharge at a
petroleum refinery. The mechanism of hydrogen cyanide (HCN) generation during catalytic cracking is hypothesized. The extent and mechanism of cyanide-induced corrosion is evaluated from a mass balance of free cyanide, complexed cyanide, iron, and thiocyanate in hydrocarbon, sour water, and wastewater streams. Analytical methodologies are developed to identify and correct cyanide interferences in sour water for this mass balance. The results of the mass balance suggest that highly corrosive free cyanide is widely distributed throughout the main column overhead system, lean oil separator, debutanizer, potentially other downstream process units, and the wastewater treatment plant. The control of this "spread" of cyanide is evaluated during a bench-scale ammonium polysulfide treatability study of sour water from upstream units. An unique and highly sensitive analytical method is developed to measure total cyanide to levels a factor of 100 times lower than the standard USEPA method. This unique method is used to determine that the ambient concentration of total cyanide in seawater receiving wastewater discharge...
Keywords: Hydrocarbon, Sour water, Wastewater, Seawater, Total cyanide, Weak acid dissociable cyanide, Complexed cyanide, Thiocyanate, Iron, Ammonium polysulfide, Mass balance, and NPDES.