Evaporation, break-up, and pyrolysis of multi-component Arabian Light crude oil droplets at various temperatures

Abstract

Crude oil sprays are often used in direct combustion applications and refinery catalytic cracking units. Droplet evaporation, break-up, and pyrolysis are important aspects prior to gas-phase chemical reactions. This paper reports an experimental suspended droplet study of Arabian Light (AL) crude oil to assess the effect of ambiance temperature on dynamic events. Experiments were conducted at three different temperatures of 620 K, 710 K, and 840 K, to examine different regimes (devolatilization, transition stage, and complete pyrolysis) for several repetitions. Break-up events involved during the evaporation were successfully identified and classified into break-up modes depending on their break-up intensity (). Additionally, the effect of the temperature on the break-up events was assessed, showing that the number of break-up events increases exponentially with temperature. Finally, the density distribution of each break-up mode, as well as their final probability distribution were assessed. Intermediate and high-intensity break-ups (2-mode and 3-mode) break-ups were favored at lower temperatures, as well as micro-explosion (4-mode), in comparison with pyrolysis regime. However, break-up frequency increased exponentially with temperature. Additionally, based on the individual break-up modes density distributions characteristic times were identified successfully for pyrolysis regime, were the gasification dynamics changed. The global droplet behavior was examined by following the time evolution of the normalized droplet diameter. Two successive stages were identified at all temperature conditions: the swelling and the regression stage. In the devolatilization and the transition regimes, evaporation was controlled purely by the diffusive processes, whereas in the pyrolysis stage, the pure diffusion stage was not observed. Instead, a second swelling was registered, where an amorphous carbonaceous structure was formed. This was attributed to the pyrolysis of the heavy hydrocarbons in the droplet.