← Solutions · Sulphur
The naphtha fails the doctor test.
- What you see
- A positive doctor test (ASTM D4952) for mercaptans, usually with total sulphur above the limit and a colour reading off specification.
- Where it comes from
- Mercaptan sulphur in the stream, sometimes made worse by storage.
- What APCO does
- Doctor-test treatment to convert the mercaptans, then desulphurisation by chemical reaction if total sulphur is still over the line. Both dosed at the terminal; before and after reports from an independent laboratory.
The proof on file
Naphtha, shore tank parcel
0.117 % → 55 ppm total sulphur, by weight
| Test | Method | Before | After |
|---|---|---|---|
| Total sulphur | ASTM D4294 | 1,170 ppm wt | 55 ppm wt |
| Mercaptan sulphur | ASTM D3227 | 0.080 % wt | doctor test negative % wt |
| Colour | ASTM D156 | +22 Saybolt | on specification Saybolt |
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