The diesel and gasoline hydrogenation units are used to produce aviation fuel; it is essential to keep these key operating points in mind

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The diesel hydrogenation unit in the refining department enables a rapid switch from -35# light diesel to aviation fuel without any intermediate products, reducing the total time required to within 4 hours, thus acting as an \"accelerator\" for increasing the production of aviation fuel. From the perspective of industrial production practices, producing aviation fuel in diesel hydrogenation units is by no means a simple process of switching over; every step involved affects both product quality and production efficiency. Drawing on practical experience in using diesel hydrogenation units to process aviation fuel, we have identified the key operational points to help you accurately manage the entire production process of aviation fuel. I. Preliminary preparations: Accurate assessment to lay a solid foundation for the production shift. To produce aviation fuel using a diesel hydrogenation unit, it is necessary to address two key challenges: enabling the unit to handle multiple tasks simultaneously and minimizing losses of intermediate materials; proper preliminary preparations are essential for success. 1. Process feasibility study: Comprehensive feasibility tests must be conducted prior to production to compare the specifications of aviation fuel and -35# light diesel. Analysis shows that, aside from a slightly lower viscosity value, all other parameters of the aviation kerosene meet the quality requirements for -35# diesel, providing theoretical support for the conversion to this product using \"zero-transition material\". At the same time, it is necessary to test key indicators such as the corrosion of the copper sheets and silver sheets used as raw materials, to ensure that the products meet the core quality standards for aviation fuel. 2. Process and equipment modification: Add a jet fuel fraction feed line to the plant before the crude diesel enters it ； After the metering station for refined diesel exiting the unit, a new pipeline for refined jet fuel has been added. Following the modification, the newly installed pipeline must be acid-cleaned and purged with nitrogen to prevent impurities from contaminating the product. In addition, it is necessary to coordinate the atmospheric and vacuum distillation units in advance to ensure an adequate supply of raw materials for jet fuel production, thereby preparing the necessary resources for the shift in production. II. Production control: Precise operations and management of key parameters. After the order to switch production is given, coordinated efforts among multiple departments along with precise control are essential for achieving a rapid switch in production. 1. Pre-adjustment: Reserving operational margin. Before changing the production process, pre-adjustments must be made based on the actual operating conditions of the equipment, in order to leave sufficient room for rapid adjustments of parameters later on. The operational stability of the plant can be maintained by reducing the load on the reaction furnace, lowering the feed temperature to the hydrogen sulfide removal stripping tower, and raising the liquid level in the reflux tank at the top of the distillation tower to its maximum allowable level, thereby preventing process fluctuations during the shift to another product. 2. On-site control: Every second counts. Once the equipment receives a notice to change production, the operators on the internal and external control posts must work closely together, facing the challenges of both speed and precision. Internal operations: Keep a close eye on the DCS screens, and precisely control key parameters such as the feed temperature of the fractionation tower, the top temperature of the tower, and the temperature at which side streams are extracted, to ensure that the process parameters meet the requirements for jet fuel production promptly. Outdoor operations: Verify the process on-site, provide real-time feedback on the equipment’s operating status, and simultaneously carry out tasks such as the replacement of the light diesel system and adjustments to the parameters for jet fuel production. At the same time, the quality inspection center must activate an \"express track\" to issue an analysis report within 1 hour of sample collection, confirming that the quality of aviation fuel meets the standards ； The scheduling department promptly coordinated with the storage and transportation department to transfer the qualified products to the jet fuel storage tanks. III. Quality Control: Paying attention to details to eliminate potential quality issues. The quality of aviation fuel has a direct impact on safety in use; therefore, it is necessary to pay close attention to the following key aspects during the production process: 1. Control of raw material and product specifications. For raw materials, strict control is required over the dry point of the aviation fuel distillate – this value should be set at +230°C – in order to reduce the amount of heavy fractions and thus prevent problems related to insufficient product freezing points from arising at the source. The boiling range of the raw material should be controlled between 185–255°C, to prevent excessive heavy fractions from affecting the performance of the product. Products: Pay close attention to monitoring freezing point, sulfur content, and corrosion indicators. The freezing point of aviation fuel must be maintained between -47°C and -51°C ； The sulfur content must be carefully controlled: it should be reduced to meet the acceptable standards, but over-desulfurization must be avoided. An appropriate amount of sulfides should be retained to ensure the corrosion resistance of jet fuel. The copper strip and silver strip corrosion tests must also meet the Grade 1 acceptance criteria. 2. Additives and product formulation: No additional corrosion inhibitors are required for jet fuel production; natural sulfides are sufficient to meet corrosion resistance requirements ； Additives such as antioxidants can be blended by the Oil Storage and Transportation Department in the tank farm, thereby avoiding operational risks and increased costs associated with adding additives within the equipment. IV. Problem Resolution: Tailored Measures to Overcome Production Challenges. During the production of aviation kerosene in diesel hydrogenation units, issues such as insufficient freezing point and high energy consumption due to excess product can arise, requiring specific improvement measures to be implemented. 1. Freezing point not meeting standards: Adjust the distillation range of the raw materials. If the freezing point of the jet fuel produced initially is between -41°C and -44°C, factors such as moisture content in the raw materials need to be examined, and the issue is ultimately resolved by adjusting the dry point of the raw materials. Strictly control the dry point of the raw materials at +230°C to reduce the proportion of heavy fractions, thereby ensuring that the freezing point of the aviation fuel meets the required standards. 2. Product excess and high energy consumption: Optimize process parameters to reduce the reaction depth; lower the reactor inlet temperature from 310°C to 295°C to cut gas consumption, with hydrogen consumption dropping from 1016 Nm³/h to 800 Nm³/h. At the same time, maintain the trace amount of sulfides required for jet fuel to ensure corrosion resistance. Optimize stripping operations: increase the operating pressure of the stripping tower to 0.14 MPa and adopt full reflux operation to reduce the loss of jet fuel components and improve product yield. V. Safety and Coordination: Multi-party collaboration to ensure smooth production. Converting a diesel hydrogenation unit to produce aviation fuel involves multiple departments such as production, scheduling, quality control, and storage and transportation, thus enhanced coordination is necessary. 1. The scheduling department must coordinate the supply of raw materials and the process of filling products into containers, as well as plan the operating schedule of the facilities in advance ； 2. The production facility must be prepared for system replacement and the availability of backup equipment; before switching to another product, all subsystems and backup devices should be inspected. During replacement, the feedstock buffer tank circulation line should be slightly opened to prevent production accidents ； 3. Real-time communication mechanisms should be established for each position, enabling efficient coordination between operators and supervisors, as well as between the production units and the quality inspection department, to ensure that issues are addressed promptly. The production of aviation kerosene in the diesel hydrotreating unit is a comprehensive manifestation of process modification, precise control, quality management, and coordinated operations. From preliminary preparations to post-production, from parameter adjustment to problem resolution, every step must be carried out with rigor and meticulousness. 4-hour rapid production switchover relies on “precise operations and efficient coordination”. In the future, diesel hydrogenation units can further adopt this model to fully utilize their potential, thereby providing stronger support for companies to increase the production of aviation fuel and enhance their profitability.