Refinery propane failing the copper strip test 2

[duncan8943]

We have had problems with our propane failing the copper strip corrosion test. We recently started more frequent testing of our propane. We have also recently switched KOH manufacturers. We don't routinely test upstream of the KOH treater, but anytime that we have--the results turned out good. Downstream of the KOH treater can be all over the map. Another thing that we noticed is very little water formation in the KOH treater. The new KOH does have ~50 PPM sulfates, where our old KOH didn't list any on the COA. Has anyone had any similar experience?

 

[Jack2010]

At the refinery where I work corrosion testing after the KOH bed is not a problem as long as you have adequate amine/caustic treating upstream. But it is possible to determine what impurity is causing the test to fail. H2S impurities will cause the copper strip to yield multi-colored green-pink-lavender copper strips around 5 ppm and dark grey-black strips at levels >10 ppm. Elemental sulfur will cause the copper strips to turn grey-black at levels >10 ppm. COS, CO2, and O2 will not color the strip at levels <100 ppm. However, hydrolysis or oxidation of COS will yeild H2S and elemental sulfur thus causing the test to fail. It is common practice to dry the propane through calcium chloride beds before reaching a KOH bed to produce a relatively dry stream.

 

[dcasto]

GPA Research Report
RR-190
An Examination of Interfering Factors in the
ASTM D-1838 Copper Strip Test

is available from gpaglobal.org

it has a matrix of what different contaminates cause what kind of strips.

You can have dry propane going into the beds, but you still need to add water to th KOH beds otherwise, the beads coat up and there is no active KOH area.