Application: Manufacture incremental gas and distillate products and simultaneously reduce fuel oil viscosity and pour point. Also, reduce the amount of cutter stock required to dilute the resid to meet the fuel oil specifications. Foster Wheeler/UOP offer both “coil” and “soaker” type visbreaking processes. The following information pertains to the “coil” process.
Products: Gas, naphtha, gas oil, visbroken resid (tar).
Description: In a “coil” type operation, charge is fed to the visbreaker heater (1) where it is heated to a high temperature, causing partial vaporization and mild cracking. The heater outlet stream is quenched with gas oil or fractionator bottoms to stop the cracking reaction. The vapor-liquid mixture enters the fractionator (2) to be separated into gas, naphtha, gas oil and visbroken resid (tar). The tar may also be vacuum flashed for recovery of visbroken vacuum gas oil.
Operating conditions: Typical ranges are:
Heater outlet temperature, ºF 850 – 910
Quenched temperature, ºF 710 – 800
An increase in heater outlet temperature will result in an increase in overall severity, further viscosity reduction and an increase in conversion.
Feed, source Light Arabian Light Arabian
Type Atm. Resid Vac. Resid
Gravity, ºAPI 15.9 7.1
Sulfur, wt% 3.0 4.0
Concarbon, wt% 8.5 20.3
Viscosity, CKS @130ºF 150 30,000
CKS @ 210ºF 25 900
Gas 3.1 2.4
Naphtha (C5 – 330 ºF) 7.9 6.0
Gas oil 14.5 15.5
Visbroken resid 74.5 (600ºF+) 76.1 (662ºF+)
Licensor: Foster Wheeler USA Corp./UOP.