Hydrocracking Technologies – Processing a variety of feedstocks

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OPEC’s 1.8 million b/d production cut for six months effective from 1 January 2017, extended to March 2018, has narrowed the discounts for heavy high sulphur crudes partly because of the construction of sophisticated refinery capacity around the globe, and partly because OPEC’s supply cut has disproportionately impacted heavy and middleweight grades. Meanwhile, the market is swimming in light sweet crudes, to the point where some grades, such as Agbami and Akbo from Nigeria, are struggling to find a buyer at all. As a result, less sophisticated European refineries designed to process mostly light oil – considered to be undesirable and projected to face potential closure – are benefiting from cheaper crude sources. On the other hand, complex refineries in the US and many new heavy oiloriented plants in Asia and the Middle East, which count on wide heavy oil discounts, are at a disadvantage, at least for the time being.

Both conventional hydrocracking technologies and those designed for treating residual streams will be impacted by the increased processing of opportunity crudes or price-advantaged crudes. These crudes could be heavy oil, medium sour or light sweet grades, depending on supply and demand in the market. Therefore it is imperative for refineries with hydrocracking units to be flexible to take advantage of lower priced oil as it becomes available in a volatile market.

A major problem for refiners looking to process tight oil in the hydrocracker is the relative lack of gasoil material provided by this feed, potentially leading to existing hydrocracking capacity being under-utilised. In order to prevent this under-utilisation, refiners may look to add additional streams (for instance, cracked stocks) to the hydrocracker feed to ensure that capacity utilisation is maintained. Additionally, the lighter nature of these tight crudes leads to more light ends coming from the hydrocracker at the same conversion level while also negatively impacting the cold flow properties of middle distillate products and lowering the octane value of naphtha produced from the unit.

For resid hydrocracking, a general increase in capacity is expected as larger quantities of residual streams are processed. The impact on more conventional hydrocracking units, however, is somewhat more complicated as the quality of intermediate streams can vary greatly based on the crude source from which it is derived and the processing that has been applied. In general, the quality of heavy gasoil streams coming from resid fractions of opportunity crudes is expected to contain high levels of sulphur and aromatic hydrocarbons. Nitrogen also is present and, depending on the particular stream, metals and asphaltenes can be other components that need removal.

The heavy refinery streams are typically derived in some way from either atmospheric residue (AR) or vacuum residue (VR) from the refinery distillation column; so, in the case of resids from opportunity crudes, one can expect all of these streams to contain high levels of sulphur and aromatic hydrocarbons. There are commercial process designs and catalysts specifically developed to handle these components.

Source: PTQ Q1 2018

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