Desalter corrosion risk: Which chloride salt impurity in crude petroleum most prolifically generates HCl during heating/distillation, causing overhead corrosion if not removed?

Introduction:
Chloride salts carried with crude (as brine) hydrolyse during heating, forming HCl that can attack overhead systems in the crude/vacuum distillation units. Understanding which salts are most problematic informs desalter performance targets.

Given Data / Assumptions:

• Common brine salts: NaCl, MgCl2, CaCl2, KCl.
• Distillation preheat and furnace conditions promote hydrolysis.

Concept / Approach:
MgCl2 hydrolyses more readily than NaCl at typical preheat temperatures, liberating HCl earlier and in larger amounts, which raises corrosion and ammonium chloride salt fouling risks in overhead systems. Therefore, magnesium chloride is the most prolific HCl source if not adequately removed by desalting/washing.

Step-by-Step Solution:

Verification / Alternative check:
Corrosion control guidelines highlight MgCl2 as the key driver of HCl formation prior to top tower neutralisation.

Why Other Options Are Wrong:

• Sodium / Potassium: Chlorides hydrolyse less under the same conditions.
• Calcium: Hydrolyses, but typically less prolific than magnesium under crude preheat ranges.
• Iron: Not a chloride brine constituent for this context.

Common Pitfalls:
Assuming all chlorides behave identically; hydrolysis kinetics differ significantly.

Final Answer:
Magnesium