Study on the mass transfer characteristics of hydrogen in heavy oil by a modified dynamic pressure step method

Abstract

The dissolved hydrogen, rather than gaseous hydrogen, plays a crucial role in the hydrogenation process. A thorough understanding of hydrogen dissolution is essential for optimizing the hydrogenation process. In this paper, the dynamic pressure step method was modified to reduce the temperature difference between the hydrogen and solution, from which the hydrogen solubility and volumetric liquid-side mass transfer coefficient (k_La) of the vacuum residue were obtained. It was discovered that temperature was the most critical factor in hydrogen dissolution, simultaneously enhancing both the hydrogen solubility and k_La. Pressure played a significant role in promoting hydrogen solubility, but had a relatively small impact on k_La. Stirring speed, although it enhanced k_La, did not affect hydrogen solubility. By normalizing the dissolution parameter, the results showed that the gas-liquid mass transfer rate decreased continuously during hydrogen dissolution and that the S_D-t_D curves after normalization were almost the same in all experimental conditions.