FACTORS AFFECTING VAPOR PHASE H_2S CONCENTRATIONS IN ASPHALT AND MITIGATION VIA SCAVENGERS

摘要

Vapor phase hydrogen sulfide (H_2S) concentrations in heavy oils such as asphalt and residuum can vary significantly based upon source and handling conditions. This work will examine and document the conditions that influence the phenomena of H_2S generation, and generate quantitative data on the H_2S removal performance of the oil soluble fully dispersible transition metal chemistry based H_2S scavenger product line. The primary concern in removing H_2S is the personnel exposure risk presented by the toxicity of H_2S. Industry-representative samples of asphalt taken from refineries in the continental US were heated to various temperatures at varying vessel liquid levels. The H_2S concentrations in the vapor space of the samples were compared to examine the impact of temperature and vessel liquid level on partitioning of H_2S, cracking of the other sulfur-bearing species, and the performance of transition metal-based H_2S scavengers. The testing confirmed that vapor phase H_2S concentrations are dependent upon the liquid level of the vessel and the temperature at which the heavy oil is stored, due to increased vapor/liquid partitioning and increased cracking of other sulfur-bearing species. The transition metal-based H_2S scavenger was not negatively impacted by increasing oil temperature; the higher temperatures improved the scavenger performance, presumably due to improved mixing and contact efficiency.