In recycled solids processes, shale oil undergoes secondary cracking/c
oking reactions on the surface of the recycle solids used as the heat
carrier. Heavy oil recycle uses these secondary reactions to advantage
to convert the heavy oil fraction produced during primary pyrolysis r
eactions to lighter, more desirable products, thereby reducing the ove
rall severity of hydrotreating which would otherwise be required to up
grade this fraction to a refinery grade feedstock. A four-lump kinetic
model has been developed to describe the rate of production of the li
ghter condensable oil, as well as the coke and non-condensable gases w
hich are also formed. This kinetic model can be used to predict yields
from the cracking/coking of heavy oil in any type of reactor.