ReaxFF molecular dynamics study on hydrogen generation from heavy oil in-situ combustion gasification

Abstract

Hydrogen is considered a key fuel in energy transition. In-situ combustion gasification (ISCG) of heavy oil is viewed as a promising new technology for blue hydrogen production, making the study of its mechanisms of crucial importance. The hydrogen production process through ISCG of heavy oil was investigated using reactive force field (ReaxFF) molecular dynamics simulation. The results indicate that hydrogen yield increases with temperature but decreases with higher oil saturation and oxygen-to-oil ratios. The detailed pathways of hydrogen production and consumption were revealed. The study reveals that hydrogen is primarily generated through the reaction of hydrogen radicals with water, contributing to 87.71% of the total hydrogen production reactions. The consumption of hydrogen is primarily due to its reaction with O radicals and OH radicals, accounting for 92.50% of the total consumption. Additionally, sulfur transfer in ISCG was analyzed and concluded; sulfur in heavy oil initially forms carbonyl sulfide (COS), which then converts into hydroxyl thiohydroxy (HOS) and hydrosulfide ion (HS) under the influence of water and oxygen, and subsequently transforms into H₂S and SO₂.