Using a \"heavy\" element as if it were light: the distributor in the slurry-bed residue hydrogenation reactor for refining processes

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The slurry bed residue hydrogenation reactor features four hydrogen injection stages, including two pipeline mixings and two distributors. For the piping systems, there is saturated dissolved hydrogen injected through bottom mixing feed, and back-purging hydrogen from the defoamer pipeline located above the product overflow pipe at the top of the reactor; these serve to provide the force necessary for uniform distribution of the initial reactants, ensure even initial distribution, cool the back-purging branches, and prevent blockages. The hydrogen injection in the distributor type involves primary hydrogen and secondary hydrogen (the terms \"primary\" and \"secondary\" are not appropriate); the flow rate of secondary hydrogen accounts for 1/4. Bubbles of different sizes are generated through ring-nozzle distribution. This distributor is installed at half the height of the reactor head, thereby facilitating mixing at the bottom of the reactor to prevent deposition, providing the initial pressure and temperature for hydrogenolysis, carrying out the initial sulfidation of the catalyst precursor, and simultaneously redistributing the mixed feed in the radial direction to help it enter the reaction zone more quickly ； The main hydrogen flow accounts for 3/4 of the total; it is distributed across the entire cross-section of the reactor using dendritic inclined nozzles. This setup provides the temperature necessary for the cracking of heavy oils into lighter compounds, as well as the activation energy required for hydrolysis and hydrogenation reactions. It also creates an inward radial flow with downward direction at high central flow rates, along with backmixing, thereby facilitating heat and mass transfer between radical reactions and carbocation reactions in the catalyst slurry environment. High flow rates and high liquid holdup enable efficient reactions in a three-phase slurry \"bed\" of gas, liquid, and solid within the reactor. The conversion between large and small bubbles helps to lift the reaction products, control the reaction order, and suppress the formation of primary/secondary coke precursors. Due to the inlet location, the primary and secondary hydrogen distributors exhibit an inherent defect: the CFD-predicted hydrogen distribution in the header and tail pipes is uneven. Coupled with factors such as radial density differences of the slurry within the reactor, variations in bubble sizes, and leaks caused by damaged seals at the junctions between annular pipes and main/branch pipes, this leads to phenomena such as uneven radial hydrogen distribution, inconsistent degrees of reaction intensity, hot spots resulting from differing rates of heat transfer, coking on internal components and reactor walls, runaway temperature increases, and radial temperature gradients.