High-density hydrocarbons such as heavy oil may be upgraded through hydrocracking by mixing the oil with hydrogen in the presence of a catalyst under high pressure and temperature in a hydrocracking reactor. The effectiveness of hydrocracking depends in part on the ability of hydrogen to interact with hydrocarbons. In order to crack long molecular chains of heavy oils, hydrogen needs to reach as many hydrocarbon molecules as possible. Effective admixture of hydrogen in the mass of hydrocarbon is therefore desirable.
Various arrangements have been devised to inject hydrogen into hydrocarbons upstream of or within a reactor. U.S. Pat. No. 3,152,981 discloses a process of forming a mixture of hydrogen and hydrocarbons wherein a distillate feed is introduced into the reactor through a line. The inventor has determined that this process has limited effectiveness, since the distillate feed is not broken down into minute particles. This limits the surface area available for contacting and hydrogen-hydrocarbon interaction. Furthermore, in the absence of bulk liquid disintegration, heat transfer to the hydrocarbons is minimal and light-weight fractions in the hydrocarbon spray remain in a liquid phase and absorb hydrogen unnecessarily, thereby reducing the hydrogen available to be absorbed by heavier fractions.
U.S. Pat. No. 4,995,961 describes injection of hydrogen into a stream of oil through spargers designed to mix the two fluids within the reactor. However, the inventor has determined that the relatively large size of hydrogen bubbles limits both hydrogen dispersion and contact area between the fluids.
The present invention provides methods and apparatus for upgrading hydrocarbons that avoid some disadvantages of current hydrocracking systems.