New Alternatives: High Temperature Naphthenic Acid Corrosion Inhibition
High Temperature Corrosion Inhibition (HTCI) offers a cost-effective alternative to metallurgical upgrades, allowing refiners to consider the use of lower cost high acid crudes. The most common HTCI products are based on phosphate esters, but these chemistries have significant limitations and add foulants in the system. Dorf Ketal has invented a new Organo Phosphorous-Sulfur chemistry that solves the problems caused by phosphate esters, offering refiners a safer and more reliable option for processing opportunity crudes containing high TAN.
Unlike phosphate esters, Organo Phosphorous-Sulfur chemistry is temperature stable and protects against corrosion by forming a protective film on the metal surface with minimal interaction with the iron sulfide layer. There is no oxygen in the molecule; our chemistry does not release phosphoric acid or form scale. It is effective at lower phosphorous levels, reducing risk of catalyst contamination. Passivation is stronger and easier to establish. In all direct comparisons, we have proven lower corrosions rates. The difference in performance versus phosphate esters increases as the level of acid in the crude increases.
It’s the corrosion control mechanism that makes all the difference. The mechanism behind Phosphate esters corrosion control requires tight control of chemical reactions at the metal surface. The reactive sulfur in the process stream reacts with the metal to form iron sulfide. The phosphate ester breaks down with temperature, releasing phosphoric acid to react with the iron sulfide to form iron phosphate, the corrosion protecting scale.
A number of things can go wrong in this complex process. The temperature instability of the chemical has to be such that it breaks down at the temperature needed to release phosphoric acid. The program performs poorly at low temperatures. Iron phosphate scale breaks off in high velocity areas and becomes a foulant. If the crude slate suddenly changes and there is not enough reactive sulfur to sustain the production of iron sulfide, the phosphoric acid has minimum ability to react with the base metal. Naphthenic acid competes with the phosphoric acid to react with the iron sulfide. If the acid content in the crude increases, it can react directly with the iron sulfide and increase corrosion.
The mechanism of Organo Phosphorous Sulfur is much simpler and easier to control. The chemistry is far more forgiving, will not foul the system, and is available only from Dorf Ketal. Contact us to learn more about performance advantages for your system.