A Texas refinery suspected higher than normal H2S in their flare gas. Yet the H2S sampling system showed emissions were within spec. But why was the low level calibration showing no H2S? The stainless steel heat trace tubing was properly set at 200C. Could the stainless steel tubing in the heat trace line be adsorbing the H2S? Or is something else going on?
Tests at ambient temperature comparing SilcoNert® 2000 coated heat trace tubing vs. uncoated stainless steel tubing showed significant adsorption of the H2S into the uncoated stainless steel, but did not account for all the loss.
A little research on the web found papers by Biela1 and Reese2 that supported the refinery's suspicion. The hot stainless steel in the heat trace tubing was causing decomposition of the H2S.
The papers demonstrated how H2S will decompose on hot stainless steel.
•Mechanism presented by Reese. –Oxidation to SO2 above 100°C in contact with Stainless steel –Assisted by the metal oxides which can be cleaved of oxygen
•Biela demonstrated complete loss of H2S, 100ppb, at temperatures above 100°C
•Biela demonstrated when inert coating applied over stainless steel, H2S loss is eliminated. Testing conducted from 50°C to 225°C
1 Biela, B.; et. al. “The Do’s and Don’ts in the Analysis of Sulfur for Polyolefin Producers”; Gulf Coast Conference, Galveston, TX, Paper 081 (2003)
2 Reese, G.; Mason, A.; Cuthbert, D.,”A Novel Solution for the Analysis of Speciated Sulfurs and Nitriles in Various Hydrocarbon Streams”; Gulf Coast Conference, Galveston, TX, Paper 36 (2014)
Comparative testing exemplifies the extent of H2S adsorption and decomposition on stainless steel.
Prevent adsorption and surface reactivity of stainless steel by using inert coatings. Assure maximum stability and minimize loss of H2S and sulfur in refinery flare monitoring.
After coating the flare sampling pathway, the sulfur response and recovery improved by orders of magnitude, assuring compliance for the refinery.
Coat the entire sampling pathway.
 |
- Probes
- Fittings
- Heat trace tubing
- Regulators
- Filters
|
Want to know where to purchase SilcoNert® 2000 coated flare and stack sampling components?
