What are the different operating modes of a hydrocracker?

Hydrocracker operating modes: Mild hydrocracking - lower severity, 30-50% conversion, produces some unconverted oil for FCC feed. Full conversion - 95-100% conversion per pass, no unconverted oil. Once-through - single pass, no recycle of unconverted material. Recycle operation - unconverted oil recycled to extinction. Product slate flexibility: Naphtha mode - maximize gasoline production (higher temperature). Middle distillate mode - maximize jet/diesel (moderate temperature). Flexibility achieved by adjusting temperature, catalyst activity, and recycle ratio. Two-stage designs: first stage for hydrotreating and partial conversion, second stage for finishing conversion. Single-stage designs are simpler but less flexible. Mode selection based on product value, crude slate, and seasonal demand.