Abstract
The effect of non-catalytic hydrogenation on the demetallization and desulfurization of Boscan crude, was studied in a batch reactor. The process scheme consisted in a thermal hydrotreatment followed by solvent deasphalting with pentane.
The metal content of the said crude is 1, 250ppm vanadium and 117ppm nickel. Sulphur concentration is 5.6% and the density is 10.3°API.
The deasphalted oil yield, after hydrotreating, was 74.3%(w/w) (81%(v/v)) on the crude. This product (24.5°API) contained only 40ppm vanadium and 3.5% sulphur, being a high quality feed for further desulfurization processes. When hydrotreating was not employed the liquid product yield was 72.8%(w/w) its vanadium content being 263ppm.
The increased demetallization in the deasphalted oil fraction after the hydrotreatment (HDV equal to 97.6% vs. 84.7% without hydrotreatment) is believed to be produced by dehydrogenation of the heavy metal containing molecules in the "resins" fraction, which favours their precipitation when solvent deasphalting the hydrotreated product.
Higher hydrogen partial pressures avoid coke formation and tend to increase considerably the liquid yield.
Mass transfer resistance due to hydrogen transport was estimated as 11% of the total, depending on the operating conditions. Enhanced turbulence decreases coke deposition, probably due to lower temperatures at the reactor walls.
Non-catalytic hydrotreatment eliminates only the sulphur fraction "easy to remove", % HDS of DAO Leing 37% for Boscan crude.
