Compare delayed coking and fluid coking processes.

Both convert vacuum residue to lighter products and coke. Delayed coking: batch operation in drums, feed enters at 480-500C, remains in drum 16-24 hours as coking proceeds, coke cut from drum with water jets. Produces: naphtha, gas oil, and 20-30% coke. Coke can be fuel grade or anode grade (low metals/sulfur). Fluid coking: continuous fluidized bed operation at 510-540C, shorter residence time. Coke particles circulate between reactor and burner (heats incoming coke). Higher liquid yield than delayed coking (5-10% more). Flexicoking adds gasifier to convert coke to fuel gas. Selection: delayed coking more common (lower capital, simpler), fluid coking for high conversion requirements or when coke has low value.