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HYDROTREATING, AND PRODUCT TREATING AND BLENDING
Publication date:3Q 2013
Hydrotreating, and Product Treating and Blending
Hydrotreating is a process that has become synonymous with removing impurities from petroleum feedstocks. By mixing hydrogen and the feedstock 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.
Hydrotreating technology is not new, and many of the well-established hydrotreating technologies, no longer patent-protected, are off-the-shelf systems that are provided by engineering firms. Nevertheless, novel flow schemes have been developed to enhance reactions while newly-designed reactor internals (e.g., trays and quench systems) squeeze out more activity from a given catalyst. The application of interstage separation and interstage strippers allows refiners to reduce the recycle ratio of hydrotreating processes, effectively expanding capacity and debottlenecking product fractionation equipment. New catalysts with higher activity allow the refiner to optimize product quality, throughput, and catalyst lifetime, while dealing with problems such as pressure drop build-up and excessive hydrogen consumption. Further, a focus on the composition and formulation of the catalyst support material and the impact of various promoters located in either active phase or in the carrier has emerged in both commercial and R&D work. Auxiliary equipment to optimize catalysts loadings and restore catalyst activity are provided. Furthermore, efforts to tailor catalyst loadings to achieve stringent product specifications in single reactor with multiple beds or in a series of catalyst reactor are noted. Integrated processing schemes with an aim towards improving process efficiency are also common.
Hydrotreating technologies for processing resid and renewable feeds are relayed in pilot-scale studies and R&D work. Resid hydrotreating allows for the conversion of heavy residual refinery streams while providing simultaneous HDM, HDN, HDS, Conradson Carbon removal, and asphaltenes conversion. Renewable feed hydrotreating is largely oriented towards technology developments that will allow refiners to upgrade highly-oxygenated, biologically derived feeds to high-quality transportation fuels. A number of established oil majors have turned their attention to the production of bio-derived diesel streams for use as "drop-in" fuel while other innovations are oriented towards producing bio-based crudes to be fed or co-fed into refinery conversion units. A focus on the development of novel processing schemes and catalyst technologies is clear, though much work is needed to determine the logistical feasibility of potentially attractive renewable feeds prior to wide scale commercial implementation of the technology. Additionally, the hydrotreating section features the latest trends and technology offerings, including:
Product Treating and Blending
Regulatory specifications for the acceptable levels of various compounds (e.g., sulfur, benzene, aromatics, etc.) in transportation fuels have been put in place in many regions around the world. The product treating and blending topics focus on strategies to remove contaminants (mainly sulfur and benzene) from refined product without the use of hydrogen. Polishing applications to meet stringent sulfur specifications have emerged commercially with a significant amount of R&D work investigating novel and alternative approaches to product treating. The popular non-hydrogen desulfurization methods covered in R&D include adsorption, oxidation, ionic liquid, and membrane. Besides sulfur removal, gasoline benzene reduction is also a critical treatment requirement as benzene is known to be a carcinogen, therefore its level needs to be reduced in the final gasoline pool.
Even though hydrotreating remains the most popular method for sulfur treatment worldwide, non-hydrogen treating still remains a viable option. Some of the drawbacks of hydrotreating include large carbon footprint, high hydrogen consumption, and expensive operation. Current non-hydrogen commercial technologies exist to remove refractory sulfur as a final polishing step before the fuels are delivered to the market rather than a substitute to hydrotreating. Overall, alternative treatment methods that consume less energy and hydrogen have become of great interest to the refining industry in terms of both current/future commercial applications and the ever-growing research and development activity in this field.
Many refiners operate old, outdated blending systems in their refinery plants. As refinery processes become more complicated and new blendstocks are integrated into the product pool, a robust and efficient blending control system will be required at each plant. Optimization of blending systems will result in significant economic gains as regulatory specifications on fuel contaminants and quality standards become more stringent. Additionally, the integration of bio-based blendstocks (i.e., ethanol and biodiesel) into the final product pool has led to additional challenges to be dealt with in the refinery blending plant. There is a greater propensity for refiners to blend C4 into the gasoline pool, especially in the US with cheap shale gas driving the price of C4 down. Inline blending is becoming more popular over batch blending as benefits of inline blending include reduced blend time, reduced storage capacity, decreased manpower, and decreased quality giveaway. As a result, the role of analyzers have grown from just simply checking fuel specifications to a more current dynamic role where process analyzers are responsible for more parameters (meeting aromatic and sulfur content) along with possessing flexibility to adjust to changing market conditions. Additionally, the product treating and blending section features the latest trends and technology offerings, including:
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hydrotreating, HT, hydroprocessing, hydrodesulfurization (HDS), hydrodemetallization (HDM), hydrodenitrogenation (HDN), hydrodearomatization (HDA), hydrogenation (HYD), hydrogen, gasoline, diesel, LCO, ULSD, ULSG, ultra-low sulfur, dieselization, fuel specifications, clean fuels, CO2, bunker fuel, renewable fuels, drop-in fuels, renewable diesel, biodiesel, renewable jet fuel, bio jet fuel, advanced process control, opportunity crudes, energy efficiency, resid hydrotreating, Conradson Carbon, asphaltenes, renewable hydrotreating, heavy oil hydrotreating, high-pressure hydrotreating, moderate-pressure hydrotreating, low-pressure hydrotreating, catalytic dewaxing, coprocessing, desulfurization, sulfur oxidation, ODS, membrane desulfurization, ionic liquid desulfurization, sulfur extraction, gasoline treating, jet fuel treating, kerosene treating, diesel treating, oxidation of thiols, sulfur removal, benzene removal, benzene alkylation, contaminants removal, gasoline blending, gasoline pool, blending process control, fuel (gasoline, diesel, jet fuel) additive/components