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HYDROCRACKING AND SOLVENT DEASPHALTING
Publication date:2Q 2014
Hydrocracking and Solvent Extraction and Deasphalting
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 that have higher average volatility and improved economic value. Hydrocracking works to improve the quality of the initial feedstock by removing N and S and increasing the hydrogen-to-carbon ratio. With the ongoing EU debt crisis and developing economies in China and India undergoing slower than expected growth, refiners have been forced to adjust operations to meet a number of emerging goals: increasing diesel production, processing heavy and highly contaminated crudes, and meeting stringent environmental emissions limitations and product specifications. 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 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 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) and resid feeds, while minimizing hydrogen consumption and shifting production away from gasoline and towards diesel-range fuels. 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.
Given the increased output from domestic shale plays such as the Bakken, Eagle Ford, and Permian basin US refiners will look to process more of these unconventional crudes. However, the light nature of these crudes will require refiners to invest in infrastructure upgrades including debottlenecking CDUs, gas plants, and naphtha units to increase the processing of these oils, particularly refiners along the Gulf Coast that are geared towards upgrading heavier crudes. If these upgrades are not undertaken, tight oil production could outpace the over 9MM b/d of refining capacity currently in operation on the Gulf Coast within two years. Also, the light nature of these tight crudes result in greater amounts of gasoline being produced while limiting the yields of middle distillates. Given the fact that diesel demand growth continues to outpace that of gasoline, US refiners will need to look at options to ensure that upgrading higher volumes of tight oil will still result in sufficient amounts of middle distillates being produced so as not to create a refined product supply demand imbalance within the US. These options include blending tight oil with heavier crudes (e.g., Canadian oilsands) to produce a so called "dumbbell" crude that can be processed within a hydrocracker to yield adequate middle distillates supply.
With changing market dynamics and fuel consumption patterns that heavily favor the production/use of diesel over gasoline, 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. Also, refiners will begin to rely more heavily on hydroprocessing units to produce high-quality, high-value products. Finally, the utilization of hydrocracking technologies to upgrade resid and/or renewable feeds to produce additional supplies of high-quality diesel 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:
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
Solvent Extraction and Deasphalting
Solvent extraction and deasphalting processes—or solvent deasphalting (SDA) as it is commonly known—use hydrocarbons such as propane, butanes, pentanes, or a mixture of these to extract light, paraffinic components from heavy residue streams. Regardless of the level of impurities in the feedstock, these processes effectively produce deasphalted (DAO) or demetallized oil (terms that are used interchangeably). DAO product quality and yield are dependent upon the solvent that is selected for the process; i.e., the quality (metals, sulfur, nitrogen and Conradson carbon levels) of the products—which can be used as lubricating oil base stock or cracker feedstock—decreases with increasing yield and with the use of heavier solvents. The heavy, highly-aromatic asphalt raffinate (pitch) can be used in a number of ways (e.g., coker feed, gasification feed, road bitumen, etc.); recovering value from the heavy byproducts will be a crucial factor in the economic advantage of deasphalting units.
Solvent deasphalting (SDA) technology can be flexibly applied in a number of areas in the refinery and in midstream heavy oil upgrading applications. Two primary features of this technology include the relatively low energy intensity and the lack of an economy of scale (i.e., refiners are not constrained by the need to install large SDA units and can economically deploy this technology in both small- and large-capacity projects). As a result, solvent deasphalting can allow refiners to improve bottoms processing capacity without negatively impacting the energy efficiency of the plant by adding a small or large capacity SDA unit. Furthermore, many integration opportunities exist to reduce the carbon footprint of the processing scheme. The size and placement of the unit will depend largely on the current refinery configuration, feed processed, and the desired product slate of the plant.
The demand for residual oil for regions around the globe is on the decline. A general shift to lighter distillate projects has also been observed, resulting in diminished demand for fuel oil and bunker fuels. In response to declining fuel oil demand, refiners will seek alternative market outlets for products derived from the residual cut of the crude barrel. Aside from fuel oil, specialty asphalts (e.g., road oils, roofing materials) and lubricant products are the most relevant to solvent deasphalting processes.
The worldwide demand for light distillate products is continuously rising as demand for residual fuel oil is diminishing. The refining industry has responded with an increase in bottoms conversion capacity—including solvent deasphalting—to transform heavier barrels of crude into lighter products. As bottoms conversion capacity increases, the supply of transportation fuels will inevitably increase while fuel oil production is limited. In conjunction with this trend, refiners will be left searching for attractive novel uses and industrial markets for the remaining residual components products from bottoms processing technology including asphalts, pitch, petroleum coke, and smaller quantities of residual fuel oil.
Overall, the worldwide reduction in fuel oil demand, coupled with the increase in demand for higher-value refined products has led refiners around the world to alter plant configurations and add bottoms upgrading capacity to shift the refinery product slate and make the supply of distillate products more closely match demand trends. The potential to install SDA equipment exists where refineries are exploring to increase their product yield with limited capital; furthermore, novel process configurations and plant strategies may result in continued interest in solvent deasphalting technology.
Additionally, the hydrocracking section features the latest trends and technology offerings, including:
Keywords: solvent deasphalting, deasphalting, propane deasphalting, deasphalting, deasphalter, deasphalted oil, DAO, asphalt, heavy oil, bottom of the barrel, integrated, asphaltene, pour point, upgrader
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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 solvent deasphalting, deasphalting, propane deasphalting, deasphalting, deasphalter, deasphalted oil, DAO, asphalt, heavy oil, bottom of the barrel, integrated, asphaltene, pour point, upgrader