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The slurry phase in the slurry-bed residue hydrogenation unit is formed in a very thorough and ingenious manner. The mixing feed tank features a height-to-diameter ratio of 10:1, just like that of the reactor, and is equipped with an axial long-shaft agitator. Hydrogen is used to create a pressure seal at the top (1.0 MPa); meanwhile, fresh feed along with hydrogen-poor recycled oil enables the dissolution of hydrogen at 340°C to form a saturated liquid. The molybdenum octoate catalyst precursor enters from the gas phase at the top of the buffer tank； Fresh feed enters through the upper opening of the buffer tank and descends along the inner downcomer to the conical section, where it mixes thoroughly with the 300°C bottom-reduction circulating oil, the reprocessed oil, and the minimum pump return flow that enter sequentially from the middle of the buffer tank – through mechanical mixing, backmixing, and the downward flow pattern within the conical section. This process leads to dispersion, homogenization, and saturation of hydrogen, resulting in a stable \"first\" slurry phase with an appropriate viscosity. In this slurry phase, in addition to the hydrogen dissolution reaction, there is also slight decomposition of molybdenum octoate at 340°C (which decomposes at 330°C), as well as hydrodesulfurization reactions with the trace amounts of H2S carried by the bottom-reduction circulating oil, along with initial cracking reactions of asphaltenes at 340°C. The mixed feed buffer tank is equipped with external heating and features a cone-bottomed six-way six-plunger slurry valve. The mixed feed at the bottom is pumped in through feed pumps, and pipeline surging is used to create a homogeneous slurry phase that enters the bottom of the reactor, thereby serving as the precursor to the slurry phase within the slurry bed reactor. This approach effectively prevents fresh feed from entering the bottom head of the reactor and undergoing pyrolysis and coking due to exposure to high-temperature hydrogen gas.