Process Technology Quick Reference Cards

Hydrocracking

Chapter from the Process Technology Quick Reference Cards.

HYDROCRACKING

Process Objective

Convert heavy gas oil (VGO) to lighter, high-quality products (diesel, jet, naphtha, lube base oil) using hydrogen at high pressure.

Key Operating Variables

Variable	Typical Range	Effect / Notes
WABT	650-800°F	Higher T → more conversion but lower selectivity (overcracking)
Pressure	1,000-2,500 psig	Higher P → better selectivity, longer catalyst life, more H2
LHSV	0.5-2.0 hr⁻¹	Lower LHSV → higher conversion
H2/Oil Ratio	3,000-10,000 SCF/BBL	Adequate H2 prevents coking and maintains activity
Feed Nitrogen	200-2,000 ppm	Primary conversion inhibitor — more N requires higher WABT

Process Configurations

Single-stage once-through: 40-70% conversion, UCO to FCC or lube
Single-stage recycle: 90-99% conversion, max middle distillate
Two-stage: 1st stage HDT/mild HCK, 2nd stage HCK — highest flexibility
Mild hydrocracking: 20-40% conversion at lower P — FCC feed quality improvement

Products & Yields

Naphtha: 10-30% (excellent reformer feed, very low sulfur)
Jet/Kerosene: 15-30% (high smoke point, low freeze point)
Diesel: 30-50% (very high cetane 55-65, ultra-low sulfur)
UCO (unconverted oil): 0-40% (lube base stock or recycle)

Common Troubleshooting

Low conversion: check WABT, feed N, catalyst age/activity
Poor selectivity: WABT too high (overcracking) — reduce temperature
High H2 consumption: check for leaks, verify H2 purity
Catalyst deactivation (fast): check feed metals, nitrogen, verify activation
High ΔP: catalyst fines, scale, coking — may need skim and fill

Source: Process_Tech_Quick_Reference_Cards_v1.xlsx · sheet “Hydrocracking”

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