How to reduce slurry bed catalyst loss?

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The key to slurry-bed hydrogenation lies in the reactor, and the key to the reactor is the stability of the slurry layer. The main parameters for determining whether the slurry layer is stable include DCS parameters such as \"viscosity, gas holdup, solid holdup, reactor ΔT, density, bottom loss THFI, and Mo concentration\", as well as data from analytical tests. Process management professionals should regularly analyze, compare, and summarize this information. To facilitate understanding of the invisible catalyst bed present in the slurry layer of a slurry bed reactor, it should be noted that the flow pattern within the reactor is not a simple plug flow; rather, it is an idealized flow with high degree of mixing, as described by the dual-vessel model. There is indeed a slurry layer within the reactor that provides a site for gas, liquid, and solid reactions. Therefore, whether the temperature is uniform along the axial and radial directions in the reactor is a key parameter for assessing the homogeneity of the slurry layer and the even distribution of the catalyst. Fluctuations in the nuclear density reflect changes in the size of bubbles, while the average density is more representative for process analysis. What is the relationship between slurry stability and Cat consumption? Firstly, the formation of the reactor slurry layer at the start of operation of the unit must proceed through a gradual process; during this time, Mo, THF, coke powder, gums, and the mixed feed materials form within the reactor and gradually stabilize, reaching a relative equilibrium. As a result, the amount of Mo discharged from the bottom of the vacuum distillation tower is controlled by the amount of fresh material added. A certain gas holdup determines the reaction residence time as well as the relative linear velocity of the gas with respect to the liquid/solid phase (greater than 7), which represents the carrying capacity. Changes in viscosity and relative linear velocity affect the level of Mo carried from the reactor to the higher fractionation stages, thereby influencing the stability factor of the slurry layer. Therefore, the direct cause of Cat consumption lies in the stability of the reactor. In a simple analysis, if, in an ideal scenario, only Ni, V, and Fe are removed from the reactor while Mo remains unchanged, then there would be no consumption of Mo. Obviously, this is not possible; therefore, to remove THFI, it is inevitable that Mo is also consumed simultaneously. As such, the amount of oil sludge discharged, along with the Mo concentration in it and the level of THFI, become particularly important. In short, a stable slurry layer in the reaction is of utmost importance; it is required that 6% (of the fresh feed) be steadily removed from the bottom, and the content of raw metal as well as the severity of the reaction conditions can be reduced to an appropriate level ； ②Ensure that the circulating oil in the bottom reduction system is free of diesel components, and minimize the presence of light paraffin oil fractions in it ； ③Stabilize the reaction process conditions, using only fine adjustments to the reaction temperature to control the degree of reaction as the main method of adjustment ； ④Control the amount of freshener added to compensate for losses based on the average value of the reduced bottom Mo over a certain period of time ； ⑤Design system reserve and consumption model modules to enable dynamic and early-warning management through configuration.