0 1 2 3 4 6 5 7
2nd Stage hydrocracker MD yield with benchmark UCO feed (P total : 2300 psig; Recycle gas rate: 5000 scf/bbl, Recycle cutpoint: 700˚F)
ICR 250 ICR 252
6.7 wt% increase in MD yield with ICR 252
3 0 Time since start-up after catalyst changeout (months) 4 5 2 1
6
Figure 3 Post-turnaround optimisation of MD yield
PPC (Vol%)
Key drivers of MD yield gains from previous cycle
Figure 2 Second-stage MD yield from pilot plant testing
Unit optimisation, 26%
This effort focused on maximising MD production through optimisation of the first-stage versus second-stage sever- ity via fine-tuned, reactor temperature profile adjustments. Additionally, MD product recovery was maximised through optimisation of the fractionation section operation. Newly installed, redesigned fractionator stripping section trays further enhanced cut-point control, minimising prod- uct overlap and maximising MD yield and recovery (see Figure 3 ). Importantly, these improvements were achieved while the unit continued to operate above design through- put and process variable feed quality. In particular, the unit successfully managed nitrogen levels that exceeded origi- nal design limits – an important consideration for maintain- ing catalyst performance. The optimisation programme delivered an incremental MD yield increase of approximately 6 wt% relative to ini- tial start-up performance. This resulted in sustained MD yields exceeding 90 LV%, positioning the unit among the top-performing hydrocrackers globally in terms of distillate selectivity. MD yield progression following catalyst chan- geout and fractionation upgrades, illustrating staged post- start-up optimisation, is shown in Figure 3. Conclusion Relative contributions of catalyst upgrades and operational improvements to middle distillate yield gains versus the previous cycle are shown in Figure 4 .
Upgraded 2nd stage catalyst, 47%
Upgraded 1st stage catalyst, 27%
Unit optimisation Upgraded 1st stage catalyst Upgraded 2nd stage catalyst
Figure 4 Drivers of middle distillate yield improvement
Sustained MD yields with an improvement of 6 wt% were successfully achieved in a large-scale two-stage hydrocracker through the integration of next-generation catalyst technology, fractionation enhancements, and systematic process optimisation. The case highlights how modern hydrocracking units processing heavy feeds can deliver industry-leading distillate yields by aligning catalyst innovation with operational excellence and ongoing techni- cal support.
Chevron Lummus Global Suresh Kumar Nellore and Raman Jhutti Contact: contact.clg@lummustech.com
Strategies to enhance the profitability of unit operations
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PTQ Q3 2026
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