Thermal dissociation of sulfur species: Analyzing variations in corrosivity of different condensate feedstock

Abstract

Traditionally, total sulfur content of a crude or condensate feedstock introduced to atmospheric distillation units in a refinery has been used as a measure to predict the high temperature corrosivity of these feeds. Such predictions were also utilized to decide on selection of materials of construction for refinery facilities processing condensate, and many chronic problems, sometimes leading to failure of materials have been reported. In reality, in addition to the total sulfur content, it is important to conduct a profiling of the distribution of the various types of sulfur components in the condensate or crude oil. A pilot plant, mimicking the thermal conditions in a condensate preheat train, was utilized to generate trends of H2S generation under various process conditions. The experimental variables included temperature, pressure, condensate feed rates, and sweep gas flow rates. Yields of H2S generation for the different conditions have been trended for the parametric studies. Such trends were compared for two different condensate feedstock, as a fundamental step towards understanding why different condensate feedstock exhibit significantly different pattern of H2S generation, and hence different corrosivity under similar high temperature processing conditions. Chromatograms of all sulfur containing species, as well as key types of sulfur-containing species have been presented to demonstrate why the H2S yield patterns can vary among different condensates.