Optimizing the entire process operation—solving the problem of frequent catalyst replacement in residue hydrogenation and catalytic cracking

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Core summary: The XX refining unit processes Russian crude oil; the irregular blending of contaminated oil and frequent changes in production operations lead to variations in the yield of residue. The dry vacuum distillation tower is often switched between light and heavy fraction separation modes, resulting in fluctuations in the properties of the residue and causing the catalysts in the two downstream units to become deactivated frequently, thus requiring replacement. Based on on-site operations, this article addresses the issue of catalyst replacement by ensuring stable raw material supply, optimizing procedures, and strengthening coordination from the source, thereby enabling the long-term operation of the facility. I. Analysis of the pain points in plant operation and their root causes: The XX refining plant processes Russian crude oil on a continuous basis. The properties of this crude oil are stable, and there is no mixing of different types of crude oil. However, dirty oil is occasionally blended into the feedstock during production. Additionally, frequent changes in the yield of residue due to adjustments in production scheduling, as well as frequent switching between light and heavy distillation modes in the vacuum tower, result in significant fluctuations in the yield and properties of the residue. This directly leads to frequent deactivation of the catalysts used in residue catalytic cracking and residue hydrogenation units, requiring frequent replacements. Such situations not only increase costs related to catalysts but also severely impact the stable operation of the plant over extended periods of time. The current production challenges are particularly severe: the contaminated oil components used in blending are complex, with uneven impurity levels. Unregulated and concentrated blending processes disrupt the balance of the residue oil components, causing heavy metals such as nickel, vanadium, and iron, as well as carbon residue levels, to exceed acceptable limits abruptly ； Furthermore, the dry vacuum distillation column repeatedly switches between heavy stripping and light stripping in a short period of time to control the residue yield, which further exacerbates the degradation of the feedstock. When low-quality raw materials reach the downstream stage, heavy metals quickly block the pores of the catalyst and damage its internal structure; at the same time, they exacerbate coking during reactions, covering the active centers of the catalyst. As a result of these two effects, the catalyst’s activity drops rapidly, forcing premature replacement, which creates a vicious cycle of \"raw material fluctuations → catalyst deactivation → frequent catalyst replacement\". II. Source optimization: Strict control of the blending of contaminated oil to stabilize the operation of the vacuum distillation tower. To break out of this dilemma, it is necessary to start by implementing controls at the source, within the atmospheric and vacuum distillation units. Taking advantage of the stable properties of Russian crude oil, efforts should be focused on regulating the process of blending contaminated oil, ensuring that blending is carried out in a quantified, steady, and gradual manner; large-scale, unplanned blending should be avoided to prevent sudden changes in the properties of the raw material. At the same time, frequent changes in the residue yield are avoided; the operating parameters of the solid dry vacuum distillation tower are stabilized. The outlet temperature, vacuum level, and mid-stage reflux flow rate of the vacuum furnace are strictly controlled, with no significant adjustments permitted. The frequency of switching between different operating modes is tightly regulated, and repeated switching over short periods is strictly prohibited. All efforts are made to maintain a stable residue yield and properties, so as to supply qualified and consistent raw materials to downstream units. III. Downstream optimization: Operation control of the residue catalytic cracking unit. To address the heavy metal contamination caused by the blending of contaminated oil, a two-component passivation agent consisting of nickel and vanadium passivators is added continuously and in sufficient quantities throughout the process, ensuring thorough mixing of this agent with the feedstock and thereby effectively reducing the toxic effect of metals on the catalysts. Strictly control the reaction and regeneration temperatures to prevent overheating, which could lead to the hydrothermal deactivation and thermal degradation of the catalyst; maintain an appropriate catalyst-to-oil ratio to reduce coke accumulation ； Rather than the previous approach of replacing the agent in large quantities all at once, a small amount of the new agent is added continuously to maintain stable activity of the balancing agent and prevent sharp fluctuations in its activity, thereby reducing the need for passive replacement during operation. IV. Downstream optimization: Precise operation and maintenance of the residue hydrogenation unit. Key parameters such as feed rate, hydrogen-to-oil ratio, and system pressure are maintained stable; operational adjustments are made in small steps with gradual transitions, and bed temperature rises are strictly controlled to prevent localized overheating and coking. Strengthen the filtration during raw material pretreatment, optimize the proportioning of the protective agents, effectively remove impurities and coke powder from the raw materials, and reduce blockages in the pores of the main catalyst ； During routine inspections, close attention is paid to the pressure drop and temperature rise in the bed; any abnormalities are promptly adjusted to intervene early and prevent rapid deactivation of the catalyst. V. Full-process coordination: Breaking the vicious cycle in operation. Make full use of the raw material buffer tanks to thoroughly homogenize the residue oil after mixing in contaminated oil, thereby stabilizing fluctuations in the properties of the raw materials ； Before blending contaminated oil in the atmospheric and vacuum distillation units or adjusting the draw level of the vacuum tower, it is necessary to inform the downstream units in advance so that coordinated adjustments can be made. Abandon the misconception of blindly pursuing extraction rates, and take ensuring the stable operation of the equipment and reducing catalyst consumption as the core management objectives, while implementing practical responsibilities at each job position. VI. Summary of Optimization Achievements: By focusing on on-site operations and ensuring precise control over each step of the process, raw materials are stabilized at the source, operating conditions are optimized at intermediate stages, and seamless coordination is maintained throughout the entire process. This approach not only significantly reduces the frequency of catalyst replacement as well as production energy consumption and chemical costs, but also ensures the continuous and stable operation of the entire installation, thereby truly achieving stable production, improved quality, cost reduction, and increased efficiency.