Different functions of the slurry bed tubular distributor
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Slurry-bed residue hydrogenation uses riser-type upward reactors. Currently, these reactors are designed in series; the basic design options include models with a capacity of 600,000 tons per year per unit (dimensions: 4400*44000 mm), 1 million tons per year per unit (dimensions: 5500*55000 mm), and 1.2 million tons per year per unit (dimensions: 5800*58000 mm). The latest designs feature three stages of hydrogen supply – primary hydrogen, secondary hydrogen, and delayed hydrogen – in a ratio of 6:2:1. The secondary hydrogen (ring distributor) serves primarily to facilitate the pyrolysis of residue oil subjected to high-temperature hydrogen quenching; it provides the initial heat required for saturated reactions involving C-S, C-C, and C-O bonds. It also acts as a fully sulfided catalyst, and it creates high-speed turbulent flow at the bottom of the reactor, thereby stirring and lifting the feed material inside the reactor to ensure that the initial temperature reaches 370°C + 20°C, which is the temperature necessary for the cracking of asphaltenes. The primary hydrogen source (spider-type distributor) is located at the tangent point below the reactor; it enables the reactor to achieve the highest hydrogen retention rate as well as initial and slip velocities. It serves as the starting point of the reaction zone, where the heat of reaction causes the temperature to rise to 420°C in seconds, resulting in a slurry of gas, liquid, and solid phases that are separated from one another. This process facilitates the light-end conversion of 65–70% of the residue oil. Three streams of hydrogen (from ring distributors) are injected from the middle of the reactor at 320°C; their role is to compensate for the decrease in the hydrogen retention capacity due to hydrogen consumption, to increase the hydrogen partial pressure, to dilute the reactants, and to reduce the rates of secondary cracking and coking ； The bed layer is cooled by sensible heat cooling, while naphtha and diesel are cooled by the latent heat absorbed during vaporization into bubbles. The synergy and coupling among the three hydrogen streams, along with controlled injection ratios and temperature management, enable a reduction in the reactor outlet temperature by 2–3°C. This creates conditions for increasing the liquid holdup and the initial reaction temperature in the lower part of the reactor, thereby improving the efficiency of the reaction zone and enhancing the reactor’s ability to handle lower-quality raw materials.
In the slurry-bed residue hydrogenation reactor, the three types of hydrogen distributors have distinct roles and work together: – **Secondary hydrogen (ring distributor)**: High-temperature hydrogen is injected at the bottom of the reactor; its main function is to rapidly heat the residue so that it reaches the cracking temperature (above approximately 370°C), while also ensuring that the catalyst is fully activated. It also creates intense mixing at the bottom, which helps to distribute the feed material evenly. - **Primary hydrogen (spider distributor): Located at the bottom of the reactor, it supplies a large amount of hydrogen, allowing the temperature to rise to around 420°C in an instant. This creates a slurry with a mixture of gas, liquid, and solid phases, enabling the majority of the conversion of residue oil into lighter fractions (about 65–70%). - **Delayed hydrogen (ring distributor): Hydrogen at a slightly lower temperature is injected from the middle of the reactor to replenish the hydrogen consumed in the reaction, maintain system pressure, reduce excessive cracking and coking, and also help control the bed temperature through its cooling effect. By coordinating the ratios and temperatures of the three types of hydrogen, the outlet temperature of the reactor can be reduced slightly, thereby improving overall operational stability and enabling operation with lower-quality feedstocks. .