The secondexamplereferstoanoilrefineryDDUwhere
retuning thebasicregulatoryloopswasalsooneofthefirststeps
of anadvancedcontrolproject.ItssimplifiedP&IDisshownin
Fig. 10.
The feed(dieselplusmake-uphydrogen)flowsthrougha
furnace, andisvaporizedandheatedtotherequiredelevated
temperature beforeenteringthefixed-bedcatalystreactorwhere
the hydro-desulfurizationreactiontakesplace.Thereaction
product consistsofahydratedhydrocarbonmixtureandhydro-
gen sulfide.Aftercoolingdown,thereactionproductenters
a stripperwherethehydrogensulfideisstrippedoutandleaves
the stripperoverheadtogetherwithlighthydrocarbons(methane
ybutane). Thebottomsproductisthedesulfurizeddiesel.The
overhead productflowstoanaminecontactorwherethe