Mild hydrocracking (MHC) process has been part of the key conversion technology for many years to increase middle distillates yields and improve downstream conversion and product quality in Fluid Catalytic Cracking (FCC) units. In order to obtain a deep hydrodesulfurization a continued hydrotreating and hydrocracking catalyst development has been crucial to meet the specification in both gasoline and ultra-low sulfur diesel (ULSD). Furthermore, the recent implementation of the new International Maritime Organization (IMO 2020) regulation has pushed refineries to operate at a more severe conditions in order to produce a bunker fuel with less than 0.5 wt% sulfur while balancing the refinery yields of middle distillate and feed to FCC. Due to the more complex refinery targets, complicated oil market and reduced refinery margin worldwide, refineries are looking for investments in either expansions (grassroots), revamping of units and considering new novel catalyst solutions for their current processes. In order to overcome refineries challenges, Topsoe has been continuously investing in improving hydrocracking technology and catalyst solutions. Typically, a conventional MHC, operating at a design pressure of 50-100 bar and space velocity of 0.5-1.2 h-1 normally provides a true conversion in the range of 5 to 30 %. However, high operating temperatures are normally required to achieve the conversion target, resulting in overtreating of the heavy products and very poor density for the middle distillate fractions. Topsoe R&D has developed two MHC technologies, available to minimize capital and operating cost compared to a conventional MHC unit: Stage Partial Conversion (SPC) and Mild Hydrocracking Integrated Post treatment (MHC-IPT). The combination of research on catalyst fundamentals and industrial experience allows the design of the most optimal process and catalyst solution customized to the needs of the refinery. The present article offers an overview of industrial and research experience within the field of mild hydrocracking, and possible solutions to to optimize the operation. Moreover, an example of a recent MHC revamp conducted by key European refinery player, Compañia Espanola de Petroleos S.A (CEPSA) and its new conversion capabilities with Haldor Topsoe catalyst are presented in the article.

Mild hydrocracking units: operation & monitoring

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