Scavenger Optimization

The SCAVOP project was aimed at improving the removal of hydrogen sulfide (H2S) from the produced flu-ids in offshore oil and gas. The first objective was to develop technical recommendations for reducing the consumption of MEA-triazine (HET), which is injected in gas streams for removing H2S. This is important as HET is used in large excess of the stoichiometric requirement, representing a high cost for the operator, as well as a relevant contributor to the environmental impact factor since unreacted HET often ends up in the water discharge. Another objective of the SCAVOP was to prove/disprove if a fouling issue observed in pe-troleum refineries is linked to the use of formaldehyde releasers for the removal of H2S from multiphase streams in oil and gas production.
Regarding the first objective, experimental kinetics data of the aqueous phase reactions of HET and HS-, the prevailing and reacting form of H2S at the pH of interest, were measured using in situ Raman spectroscopy and NMR. The experimental observations were used to formulate a kinetic model for the reactions. Moreo-ver, a pilot unit was designed and realized for studying the absorption of a gas in a dispersed liquid flowing co-currently, thus resembling the offshore oil and gas process configuration. Different injection systems were tested, including a quill and spray atomizers. Based on the experimental observations, a physicochem-ical model, considering both the rate of absorption of H2S and the reaction kinetics in the aqueous phase, was developed. The model indicates that switching from quills to spray atomizers in offshore oil and gas in-stallations has the potential of reducing HET consumption of up to 50%. Increasing process temperatures is also beneficial, with the largest gains up to 140C.
Regarding multiphase scavenging, the results indicate a link between the use of formaldehyde releasers and the fouling observed in the receiving refinery. The mechanism of this phenomenon was elucidated.