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HYDROTREATING AND GAS PROCESSING
Publication date:3Q 2016
Hydrotreating and Gas Processing
Hydrotreating is a proHcess that has become synonymous with removing impurities from petroleum feedstocks. By mixing hydrogen and feedstocks under controlled conditions in the presence of a catalyst, contaminants in the form of sulfur-, nitrogen-, and oxygen-containing compounds, as well as metals, can be removed. When the catalyst is designed to remove a specific class of compounds, that fact is reflected in the name of the process, e.g., hydrodesulfurization (HDS), hydrodemetallization (HDM), hydrodenitrogenation (HDN), and hydrodearomatization (HDA)/hydrogenation (HYD). Hydrotreating is suitable for removing contaminants from product streams or feedstreams. For the feedstocks intended for other refinery processes—catalytic cracking, hydrocracking, catalytic reforming—hydrotreating serves two purposes: (1) it improves the quality of the products of those processes (especially quality specifications mandated by law, e.g., benzene reduction in motor gasoline), and (2) it protects the sensitive (and costly) catalysts from contamination. Hydrotreating is not without drawbacks: the capital investment is significant; operating costs (catalysts and hydrogen) can be high; and product quality may be adversely affected by the potential saturation of aromatics and olefins.
As oil becomes more difficult to access and process, the supply of energy may struggle to keep pace with demand. Along with demand growth, tighter environmental regulations for on-road fuels and an increased focus on reducing CO2 emissions from industrial sources will force refiners to alter operations, and these alterations could be a challenge as capital and operating budgets continue to decline. Hydrotreaters will help refiners cope with this changing market, as these units offer the ability to upgrade unconventional (resid and renewable) feeds to produce more diesel while helping meet stricter environmental regulations.
New, more stringent standards with regard to sulfur content within transportation fuels has been a major driver for hydrotreating technology over the past year. As more countries continue to adopt Euro V standards, which calls for 10 ppm sulfur within diesel, refiners seek to improve the production of ultra-low sulfur diesel (ULSD). Companies and licensers continue to research on and release highly active HDS catalysts that allow for high HDS conversion while limiting the weighted average bed temperature (WABT) of their reactors. Furthermore, the ongoing shale boom and natural gas supply in the US have led to cheaper hydrogen production for refineries, which has opened the door for increased diesel production by increasing the volume swell of a particular unit. New offerings allow for saturation of aromatics in feeds like LCO in order to decrease diesel density and therefore increase the potential gains of incoming crude. Improvement to diesel quality has also been addressed through hydrodewaxing (HDW), which can improve the cloud point and pour point for better cold flow properties. Numerous companies have released technologies which aim to efficiently and effectively dewax a diesel stream through the use of selective catalysts.
Another challenge for refiners comes from the Tier III gasoline standard, in the US which calls for 10 ppm sulfur in gasoline, which is a third of the previous standard. This change greatly impacts the production of FCC gasoline, as it accounts for the around a third of the gasoline blending pool, and is the main contributor of sulfur in the final gasoline product. Different refiners and licensers offer technologies and recommendations when deciding between FCC pretreatment and FCC posttreatment. Both options can reduce sulfur levels to meet the new standards, but at a cost. Pretreatment requires reactors to operate at higher severities, which can decrease catalyst cycles by as much as 40%. Companies are releasing and carrying out research into highly active FCC pretreat catalysts that can produce low-sulfur FCC feeds while maintaining desired cycle lengths. Meanwhile, posttreatment of FCC naphtha can lead to olefin saturation and significant octane loss as a result. New offerings and current research aim to find ways to increase HDS activity while decreasing olefin saturation by making the HDS process more selective.
Additionally, the hydrotreating section features the latest trends and technology offerings, including:
New KF 880 STARS catalyst from Albemarle for the production of ULSD;
Rising crude prices due to increasing global demand coupled with new environmental regulations have made it crucial to extract the maximum amount of valuable materials from each barrel. Refineries are following this recent trend with one effort being focused on increasing profits by converting refinery offgases (ROGs) into useable fuel. However, extracting higher amounts of useable products from gaseous streams is gaining popularity in the industry because isolating important compounds has become economically more attractive. This is because of the higher demand for liquefied petroleum gas (LPG) in some countries, the increased need for propylene and ethylene in the petrochemical industry for the manufacture of important derivatives as well as the greater emphasis put on product upgrading using hydrogen.
Various technologies are being implemented to improve profitability by removing valuable C3 and C4 components so that they are not lost to a fuel stream or flare. Also, the growing demand for ethylene, propylene, and their derivatives has made it advantageous for refiners to implement olefin separation and recovery processes in addition to on-purpose production technologies. Absorption fractionation schemes seem to be the most popular due to the potential for heat integration of the rectified-absorber and the primary process unit. On the other hand, cryogenic processes may be favored over absorption separations when ethylene and ethane recovery is desired.
Hydrogen can be obtained as a byproduct from naphtha catalytic reformers, purchased from third-party sources, or produced in on-purpose H2 facilities. To meet hydrogen demand increases, refiners can supplement on-purpose production with hydrogen recovery techniques. Currently, PSA technologies dominate the field of hydrogen recovery from refinery offgas. Membrane separation and cryogenic distillation are other options that offer their own advantages. Alternatively, hybrid methods can be used to overcome limitations of the individual technologies.
Additionally, the gas processing section features the latest trends and technology offerings, including:
An updated look at the market conditions for refinery offgas recovery including the supply and demand of olefins and their derivatives and the future of the global hydrogen generation market including the reliance of refiners on third-party supplies;
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Keywords: hydrogen, hydrotreating, middle distillates, diesel, ULSD, heavy oil, tight oil, 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, resid hydrotreating, renewable hydrotreating, renewable jet fuel, renewable diesel, biodiesel, dewaxing, cold flow properties, cloud point, pour point, cetane, Tier III, gasoline, FCC pretreatment, FCC posttreatment, hydrocracker pretreatment, HDS, hydrodesulfurization, hydrodemetallization, HDM, hydrodenitrogenation, HDN, hydrodearomatization, HDA, hydrogenation, HYD, gas plant, gas processing, LPG, liquefied petroleum gas, propylene, hydrogen, olefins, propane, butane, refinery offgas, ROG, refinery fuel gas, cryogenic separation, membrane, saturated gas, unsaturated gas, extractive distillation, absorption, PSA, pressure swing adsorption, FCC gas plant, hybrid separation