- Method ASTM D4929/ATM-058
- Repeatability variable, see method
- Reproducibility variable, see method
- Blending linear
- Additive Correction No
These test methods cover the determination of organic chloride (above 1 μg/g organically-bound chlorine) in crude oils, using either distillation and sodium biphenyl reduction, distillation and microcoulometry, or distillation and X-ray (ATM-058).
Organic chlorides are not known to be naturally present in crude oil. They are picked up from cleaning and handling of the oil from pipelines, shore tanks, vessels, etc.
Chlorides can be very harmful to many systems in the refining process. The presence of chlorides, moisture, and oxygen will cause steel to rust at an accelerated rate which can damage parts such as towers, boilers, etc. The second leading cause for concern with chlorides is in the hydrogenation process that is used to scrub sulfur from refined product. When chlorides are exposed to heat and hydrogen they can form hydrochloric acid. Once this acid is formed inside the unit it can collect and erode many parts through the rest of the process increasing the chances of catastrophic failure.
Total chlorides are important as well but they will not come over in the distillation tower to affect the rest of the refining process. However they still contain corrosive properties that can be harmful to storage tanks, pipelines, and vessels.
The test method is performed by first distilling the product to be analyzed to a temp of 400°F. The overheads are then washed 3 times with caustic and 3 times with water. Once this is complete the overheads are ready to be analyzed using one of the three technologies above
depending upon the method.