Handling \"heavy\" loads as easily as in the slurry bed reactors of refining technology
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The slurry-bed residue hydrogenation reactor should be strictly classified as a \"tubular reactor\"; its \"high gas flow rate and high liquid backmixing\" determine its characteristics of a large height-to-diameter ratio and limited nominal scale for single reactors； Its “reaction kinetics of large and small bubbles” determine the intensity and balance between radical cracking reactions and cationic hydrogenation reactions in the bubbling zone and foaming zone ； Its “gas-liquid-solid three-phase reaction” determines the instability of the slurry state within the reactor, the hydrogenolysis tendency during the initial reaction, as well as the high gas retention and lightening rate at the end of the reaction. I. Slurry-bed residue hydrogenation ensures a circulation of catalyst, continuous phase, and unconverted oil: the fresh feed ratio is 1:1.2. The apparent space velocity determines the nominal processing capacity of a single reactor, while the manufacturing complexity of the reactor dictates its size. A fresh feed rate of 1 million tons per year (with a total feed volume of 2–2.2 million tons) represents the optimal choice for slurry-bed residue hydrogenation reactors. II. The ease of conversion of the feed oil in slurry-bed residue hydrogenation units, as well as parameters such as the cracking index, affect the efficiency of the reactor. In the same reactor, as the amount of asphaltenes in the feed increases and the structure of these asphaltenic islands deteriorates, the processing capacity declines and the degree of lightening decreases under the same reaction conditions. III. The saturated dissolved hydrogen in the feed to the reactor, the large-bubble hydrogen from the main and auxiliary distributors, along with the pyrolysis reaction gases and the gaseified light components, contribute to a high gas flow rate within the reactor. As this flow rises, it lifts the slurry; simultaneously, this results in higher flow rates in the center of the reactor compared to the edges, thereby facilitating enhanced mixing, better heat transfer, and a nearly isothermal reaction environment. IV. During the slurry reaction process, the large and small hydrogen bubbles gradually become smaller as some of them dissolve due to the consumption of chemical hydrogen; large bubbles turn into small bubbles, and small bubbles transform into dissolved nanoscale particles at the interface ； Some of the bubbles collide with each other and grow larger, resulting in an increased flow rate; these bubbles continue to expand, further intensifying the backmixing. The intensity of this backmixing is much greater than that produced by external circulation pumps, and this is the typical characteristic that distinguishes slurry bed reaction technology from bubbling bed technology, as well as the fundamental reason for its high efficiency. V. The initial reaction in the slurry bed is crucial; it represents a competition between radical reactions and hydrogenation reactions. Once the radical reactions become stronger than the hydrogenation reactions, the slurry at the bottom of the reactor condenses to form a second liquid phase, which leads to deposition, effects on hydrogen distribution, flow imbalances, elevated temperatures, and the shift of hot spots. Therefore, it is essential to ensure favorable initial conditions such as high catalyst dispersion, high degree of asphaltenes breakdown, high hydrogen pressure, and a high starting temperature. VI. The presence of a foaming zone in the upper part of the reactor is an indicator of whether the reactor is being utilized fully. The upper foaming zone is relative; generally, areas with a density greater than 250 are considered bubbling zones ； If the density is below 250 and the temperature rise at the upper part suddenly increases by more than 4°C, it is considered that secondary cracking, hydrogenation exothermic reaction, and foaming may occur; the preventive measure is to increase the feed to the reactor or the amount of hydrogen (depending on the changes in the high-pressure liquid level). VII. The characteristics of tubular reactors include high efficiency, strong adaptability, and high uniformity ； The scale is determined by the number of reactors ； The operation of a single reactor allows for flexible adjustment of disposal ； Modular arrangement of several furnaces and several reverse units.
The slurry bed residue hydrogenation reactor is a highly efficient tubular reactor, whose main characteristics include high gas flow rates and liquid backmixing, as well as the instability of gas-liquid-solid three-phase reactions. Its design optimizes processing capacity and weight reduction, to meet the conversion requirements of different crude oils. The reactor features efficient bubble dynamics control to ensure uniform and efficient reaction. By precisely controlling the feed and hydrogen, the reaction process in the reactor can be effectively managed to avoid side reactions and hot spot issues. .
Please explain how to effectively manage the reaction process in the reactor, for example, how to make adjustments in advance when the asphaltenes in the feed oil increase? How to intervene and adjust when the sulfur content in raw materials decreases? What is the reason for the emergence of hot spots at the bottom and their flow migration? Please give your advice!
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Effective management of the reaction process in a reactor requires timely adjustments based on the characteristics of the feed oil and the operating conditions of the reactor: 1. When the asphaltenes in the feed oil increase, since asphaltenes are difficult to convert, the reaction conditions can be optimized by increasing the hydrogen supply, raising the reaction temperature, or adjusting the catalyst. At the same time, it may be necessary to increase the circulation ratio to ensure a more complete reaction and prevent carbon buildup at the bottom. 2. When the sulfur content of the raw material decreases: A lower sulfur content means that it is possible to reduce the hydrogenation pressure or temperature, thereby reducing energy consumption and extending the catalyst’s service life. At the same time, it is also necessary to adjust the hydrogen sulfide treatment facilities to ensure system safety. 3. Reasons for the formation of hot spots and their migratory movement at the bottom: This is usually due to insufficient conversion of the reactants in certain reaction areas or catalyst deactivation, which leads to intensified local reactions and the creation of hot spots. The presence of hot spots causes the temperature in that area to rise, affecting the overall uniformity of the reaction and potentially leading to catalyst coking or equipment damage. Countermeasures include improving the mixing effect at the bottom, increasing the flow rate of the cooling medium, or replacing the catalyst in a timely manner to ensure uniformity of the reactions within the reactor. All the above adjustments must be carried out in conjunction with actual production conditions and online monitoring data to ensure the efficient and stable operation of the reactor. .
It explains the prevalence of hydrogenation, but does not provide a specific analysis of the characteristics of hydroprocessing of sludge oil in slurry reactors. Due to the use of monatomic catalysts in such reactors and the dual-bubble dynamics mechanism, the goal is to lighten the sludge oil rather than remove heteroatoms; as a result, the adjustment and control of related parameters differ significantly from those in fixed-bed (trickle bed, liquid phase) or fluidized-bed reactors (where the catalyst matrix and mass transfer mechanisms are different from those in slurry reactors). In some cases, the causal relationships are even reversed, such as regarding the reaction products of HDS, HDN, HDA, and n-normalization, as well as the material balance of these products.