PTQ Q4 2022 Issue

A Matthew Stephens, Senior Manager of Economic Engineering, Imubit, matthew.stephens@imubit.com: From a process optimisation perspective, we see other ways to optimise the yields of a hydrocracker aside from simply increasing conversion/severity in response to heavy feeds. In a VGO hydrocracker, profitability can be boosted at a fixed UCO yield by manipulating conversion between first and second stages. We have seen significant value in this approach without increasing conversion, and thereby a higher UCO flow can be maintained, keeping overall energy, fouling, and corrosion concerns at a lower level. Doing this, of course, requires a very accurate process model that can dynamically adjust to the varying feed quality and catalyst condition of the unit as well as market prices. A Marcello Ferrara, Chairman, ITW Technologies, mfer- rara@itwtechnologies.com: It is quite common for UCO heat exchangers to foul, given the highly waxy nature of the feed. Despite the operating solutions that can be found and developed on a case-by- case basis when trying to adjust a physical parameter, it should be noted that fouling deposition is not a physical matter and, by evidence, it will continue forming despite operating/equipment adjustments. Antifoulants can sometimes be used to mitigate this prob- lem, but they do not eliminate fouling deposition, and opera- tors frequently struggle to run until the next turnaround in a ‘run-to-death’ mode which involves losses. ITW Online Cleaning technology can solubilise UCO fouling using a tailor-made and proprietary chemical. The chemical is spe- cifically designed to dissolve and stabilise UCO fouling. An entire system can be cleaned in 24 hours on a feed-out/ feed-in basis. After Online Cleaning, the unit can immedi- ately resume production without the need for equipment opening and waste generation. A Dipankar Mitra, Senior Consultant, KBC (A Yokogawa Company), Dipankar.Mitra@kbc.global: In the current market that rewards efficient operations, many refiners are looking closely at furnace performance. In many cases, a detailed economic analysis based on yield gain and energy cost within emission limits is the appropriate, cost-effective approach to pursue. Typically, modern hydro- cracker units have proper heat integration with high furnace efficiencies and effective recovery of high-level heat. Therefore, increased conversion will likely result in less duty and emissions than upgrading lower-value heavy materials to distillates. While the increase in furnace outlet temperature directly affects fuel consumption and emis- sions, its effects extend much further. As cracking levels increase, hydrogen requirements and fractionation duties also increase. Even so, increasing conversion can be benefi- cial unless carbon costs are exceptionally high or upgrade margins are exceptionally low. To determine an appropri- ate conversion level, a comprehensive analysis should be completed. A key aspect of the hydrocracking process involves converting crude oil into valuable components, such as fuels, lubricants, and chemicals. In order to increase the

The latest high efficiency and low DP trays and the replacement of tray sections with packings usually help refiners increase throughput, but small gains in energy can also be achieved via such modifications. Q Increasing hydrocracker reactor heater temperature is a typical strategy when upgrading heavy feedstocks but should be balanced against higher energy costs and emissions considerations. Further complicating matters is fouling and corrosion of hydrocracker unit heat exchang- ers by unconverted oils (UCOs). What trends do you see in resolving increased fouling from UCOs? A Chad Perrott, Business Advisor, Albemarle Corporation, chad.perrott@albemarle.com: UCO heat exchanger fouling is common in conversion hydrocracking units with an insufficient purge. This leads to a build-up of heavy polynuclear aromatics (HPNAs). The HPNAs are most often associated with coronene and ovalene, which have a red/orange colour. These HPNAs are increasingly hard to convert when recycled through the hydrocracker because their ring count will typically increase. Historically, the only way to manage them was with increased purging of HPNAs to prevent additional con- densation reactions or the addition of adsorbents. Currently, bulk metal catalysts (BMC) such as the propri- etary Nebula or the proprietary Celestia are advanced for- mulations with up to 200% higher hydrodearomatisation (HDA) activity and hydrodesulphurisation (HDS) activity capable of saturating HPNA precursors like coronene and ovalene. Saturating these multi-ring aromatics can minimise fouling in hydrocracker UCO streams, leading to reduced UCO purge rates. In addition, overall reactor HDS and HDN activity will also increase because of the loaded BMC. Higher HDN activity results in lower reactor WABTs for equal nitrogen (N) slip to the hydrocracking catalyst. Lower hydrocracker pre-treat WABTs increase the cycle time spent in the kinetic aromatic saturation mode, thus avoiding the thermodynamically controlled regime where dehydrogenation is present and more HPNAs are produced. Therefore, the trend towards increased use of BMCs in hydrocrackers can increase profit- ability through less UCO purge and reliability through fewer fouling events. A Roberto Tomotaki, Becht, Heat Exchanger Advisor, Becht, rtomotaki@becht.com: For existing exchangers, the most immediate performance improvement is to clean them with the most effective cleaning methods. Advancements in cleaning technologies such as Ultrasonics and Thermal cleaning have allowed the return of the exchanger’s performance to near clean design conditions. Exchanger fouling can be reduced by redesigning the bundles with new technology. Becht’s Bundle Technology Upgrade (BTU) programme can help identify the bundle technology best suited for the service. Recent advance- ments in thin film antifouling exchanger coatings have led to reports of significant fouling reduction.

PTQ Q4 2022