HYDROCARBON PUBLISHING COMPANY
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A member of the Hydrocarbon Analytics Group
Publication date:2Q 2018
Hydrocracking (HC) is utilized in refineries to upgrade a variety of feeds that range from coker naphtha to various heavy gas oils and residual fractions into lighter molecules. The hydrocracking process has emerged as the primary diesel producer in many refinery configurations, and as environmental regulations on transportation fuels continue to tighten, the hydrocracker will be one of the tools available to refiners to meet new product specifications. Unlike FCCU processes, hydrocrackers can effectively yield ultra-low sulfur diesel (ULSD) streams whereas middle-distillate range FCC products (i.e. light cycle oil, LCO) will regularly require additional treating to meet product blending specifications.
Hydrocracking units can also offer improved flexibility to shift production modes between gasoline and diesel (or called gas oil) products based on process selection, operating conditions, and catalysts used. The severity (e.g., temperature, H2 partial pressure, LHSV, process configuration, catalyst type, etc.) of the unit is set based upon the composition and properties of the feedstock processed and the desired conversion level and/or product distribution. Certain feeds (e.g., paraffinic) may be difficult to crack and thus require a higher operating temperature, while others (e.g., aromatic feeds) may have a high tendency for coke formation and, thus, require special catalyst formulations. Hydrocracker operators have been looking to increase the profitability of the unit by processing heavier feedstreams, including heavy vacuum gas oil (HVGO), FCC LCO, coker gas oil, visbroken gas oil, deasphalted oil, and resid feeds, while minimizing the hydrogen consumption and boosting overall energy efficiency. Residual feeds present the problems of increased H2 consumption, lower product yields and quality, and reduction in cycle length. Technology developers have been searching for methods to allow for hydrocracking units to continue normal operation while processing these difficult-to-handle feeds. These optimized parameters include higher liquid-gas distribution and reactor volume efficiency. Along with optimized process parameters, catalyst companies are also developing novel formulations that aim to increase process performance while dealing with these challenging feeds. These novel catalysts may be paired with state-of-the-art reactor internals to maximize performance.
Typical yields for a full conversion hydrocracker using a flexible catalyst to swing between maximum diesel and naphtha modes are: 0.2-0.4 wt% dry gas, 6.0-13.0 vol% LPG, 28.0-48.0 vol% naphtha, and 54.0-85.0 vol% diesel and jet fuel combined. If the unit is designed to make maximum naphtha, the total naphtha yield could be as high as 115.0 vol%. Light naphtha from a hydrocracker often can be blended directly into gasoline pool. The heavy naphtha is typically sent to reforming unit for octane boost. The reformer generates hydrogen but a hydrogen plant is likely required to supplement the hydrogen requirement of the hydrocracker. The diesel and jet fuel require no further processing, as these often exceed the cetane and smoke point requirements, respectively.
Process designers and catalyst manufacturers are feverishly developing cost-effective and energy-efficient hydrocracking technology and revamp options to satisfy the refining industry around the world. Hydrocracking technology licensers are looking at new ways to remove heavy polynuclear aromatics (HPNAs) from the unit as the buildup of HPNAs can lead to increased catalyst deactivation and fouling. Multiple-phase hydroprocessing units have also been developed to minimize hydrogen consumption while also reducing unit severity. Finally, the utilization of hydrocracking technologies to upgrade resid and/or renewable feeds to produce additional supplies of high-quality liquid products has been covered extensively through commercial projects and R&D work over the past several years.
Additionally, the hydrocracking section features the latest trends and technology offerings, including:
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Keywords: hydrogen, hydrocracking, middle distillates, diesel, ULSD, heavy oil, tight oil, ebullated-bed, slurry-bed, fixed-bed, single-stage, two-stage, two-stage with recycle, jet fuel, kerosene, gasoil, gas oil, coker gas oil, coker naphtha, DAO, VGO, HVGO, LCO, mild hydrocracking, resid hydrocracking, renewable hydrocracking, renewable jet fuel, renewable diesel, biodiesel, dewaxing, cold flow properties, cloud point, pour point, cetane, platinum, palladium, NiMo, CoMo, NiW, heavy polynuclear aromatics, HPNAs, Fischer-Tropsch, F-T