Future Roles of FCC and Hydroprocessing Units in Modern Refineries


Hydroprocessing—i.e., hydrotreating and hydrocracking—is the "must-have" process in any refinery converting a variety of fossil and renewable feeds into transportation fuels and heating oil. Hydrotreating is primarily used to remove heteroatoms and metals, while hydrocracking significantly reduces the molecular weight and, in some cases, the aromatic content of the feed. Increasingly stringent regulations for fuel (e.g., 10- to15-ppm-sulfur diesel and gasoline); the processing of more low-quality, high-sulfur crudes resulting in more coker naphtha being sent to hydrotreaters; tightening refinery site emissions standards (e.g., SOX and NOX reduction); and rising gasoline and diesel consumption are all factors that translate into higher demand for hydrotreating. In response, refiners are looking to expand hydrotreating capacity throughout the world.

Looking ahead, the Paris-based International Energy Agency (IEA) forecasts global hydrotreating capacity to rise by 8.1MM b/d through 2012. Middle Eastern and Asian refiners will add over 1MM b/d of resid desulfurization (RDS) capacity over the next five years. This Report discusses the various drivers for hydroprocessing, the development of  new technologies in response to those drivers, and how refiners can benefit from the new technologies.

Ultra-clean gasoline and diesel production

With the supply of light sweet crudes dwindling, the current trend in hydroprocessing is the treatment of heavy sour feeds that contain compounds such as sulfur, nitrogen, aromatics, iron, and other undesirable components. These compounds pose significant problems with catalyst poisoning; however, developments are keeping pace with increased demand. In light of growing demand for ultra-low-sulfur diesel (ULSD), LCO hydrotreating is receiving much attention. Feeds such as these are typically high in heavy metals, which require additional unit modifications. Although it takes a back seat to ULSD projects, hydrotreating around the FCCU is another important focus. Half of all FCCUs incorporate pretreaters to meet their gasoline sulfur requirements, and improvements to these make up the majority of ULSG-oriented revamps. This Report devotes a complete section to evaluating options to improve hydrotreater profitability, and offers recommendations as to which option represents the best return on investment.

Five of the most common approaches to upgrading hydrotreaters for clean-fuels production (in order of increasing capital cost) are (1) upgrading feedstock and integrating processes, (2) implementing a higher-activity catalyst, (3) replacing reactor internals for increased efficiency, (4) adding reactor capacity, and (5) increasing H2 partial pressure by installing an amine scrubber or a PSA. Refiners also have the option to implement advanced process control (APC) and simulations to optimize operation. Processes that are currently being marketed include the use of multiple reactors in series, dual catalyst systems, interbed quenching, and catalytic distillation. On the R&D side, the use of countercurrent processing, gas and liquid phase reactors in series, and the use of sorbents or liquid extraction for nitrogen removal are all disclosed.

Commercial catalyst developments have been accelerating. The latest catalysts are presented, including FCC pretreat catalysts that eliminate the need for gasoline post-treating, catalysts for hydrotreating heavier feeds like LCO and coker oils, and catalysts with multiple functions, like optimized hydrodesulfurization with minimized hydrogen consumption. Also included are discussions of new work focused on unsupported transitional metal sulfides; the addition of metals such as iron, tungsten, niobium, boron, and phosphorus to catalyst compositions; and the use of unsupported nanoparticles. Lastly, commercially-available process design and hardware have become more specialized. In particular, there is a focus on process schemes that effectively reduce hydrogen consumption; e.g., two-phase system.

Processing heavy crudes and residual oils

Interest in residue hydroprocessing has been heightened by several factors. One is that environmental legislation continues to limit sulfur and aromatic compounds in motor fuels. Also, since the worldwide supply of light crudes is diminishing, future demand will be met through the use of heavy oils. This scenario will lead to greater amounts of atmospheric resids (AR) and vacuum resids (VR). The term residue hydroprocessing denotes process schemes for converting feeds with high levels of asphaltenes, metals, and heteroatoms to cleaner, lower-boiling-point materials while simultaneously trying to minimize the production of coke and gases.

Issues that must be addressed with regards to residue hydroprocessing are the problems posed by asphaltenes. Asphaltenes are thought to be responsible for sludge formation and its harmful effects, and they can also cause catalyst deactivation. Therefore, the conversion of these molecules is critical to achieving deep desulfurization and demetallization from resid feeds. This Report identifies significant developments in the resid hydrotreating process and in catalyst areas.

Process developments using fixed-, moving- or ebullated-bed reactors are included in the discussion. Also, methods to reduce coking, improve conversion, and achieve greater operational flexibility are addressed. Supported NiMo or CoMo catalysts are commonly used in hydrotreating applications. Developments in pore structure, comparisons between supported and dispersed catalysts, the utility of hydrogen donor solvents, and new promoters such as phosphorus, boron, tin, and halogens are laid out for the refiner's convenience.

Hydrotreating of fats and oils to produce a "green" or renewable diesel

This report identifies and analyzes many renewable feed projects undertaken by refiners and vendors to incorporate biofeeds into refinery hydrotreaters. We also incorporate other works not widely known in the industry and include a comparison of all technologies. Some of the known endeavors include: 

  • BP's work on extracting oils from plants and combining them with refinery streams that are being hydroprocessed, as well as the hydrogenation of animal fats to produce a diesel blending component;
  • CANMET Energy Technology Centre's hydrogenation process that converts a variety of vegetable and animal products into a high-cetane diesel-range product;
  • Neste Oil's second-generation process for producing a renewable diesel fuel;

  • Nippon Oil's process for hydrogenating palm oil;
  • Petrobras's process that introduces a renewable feed source into conventional diesel production;
  • UOP's work with Eni SpA on a green diesel process.

Besides concerns over specific handling and storage logistics, problems such as quality of hydrotreated vegetable oils in terms of high paraffin content, low filter plugging points, and low density are major concerns. There are recommendations on how and where to incorporate the biofeeds into existing hydrotreating units based on economic considerations.

Increasing productivity and improving energy efficiency

A topic currently of great interest in today's economic climate is improving the productivity and energy efficiency of hydrotreaters. With the current global economic situation and the uncertainty in the long-term market for crudes, there is a need for processes that not only improve productivity, but also increase the energy efficiency of the unit, leading to a savings in both capital and operating costs. Technologies that prevent catalyst deactivation and the use of advanced process control software are currently being marketed.

Several steps can be taken to improve energy efficiency and effectively meet rising hydrogen demand. The use of more energy efficient boilers and heat exchangers can be employed. Better insulation around the entire unit can also help to keep energy costs low. Also, the implementation of a business management strategy, such as Six Sigma, can help remove the causes of defects and errors and improve productivity across the entire refinery. Lastly, the use of new separation techniques, such as membrane separation, that are not as energy intensive as traditional separation techniques, may also gain market presence.

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