Vacuum Tower Arrangement

[qazx]

What are the differences in vacuum tower arrangement for medium and heavy crude with the same No. of products (LVGO, MVGO, LLC, HLC, Slops and Vacuum Residue)?I mean No. of Beds, No. of refluxes and their location, location of side draws with respect to packing beds and No. of packing beds between two side draws.

 

[25362]

Just some comments: contrary to common judgement, switching to a heavier crude doesn't always improve vacuum ! On the contrary: at equal mass flow rates, the heavier the crude, the longer its residence times at high temperatures, everywhere from the topping heater onwards.

Greater residence times induce more thermal cracking and increased gas and vapor loads to the vacuum-producing equipment.

The general approach to cope with these effects would be to add a bit of "velocity" steam to the heater tubes with a parallel reduction in temperatures.

One should remember, however, that if the properties (densities, in particular) of the oil and the steam are very different, they may segregate and create an annular flow r[é]gime with steam flowing as a (central) core. When in these flow conditions, increasing steam injection would do very little to increase the oil velocity or diminish its thermal degradation.

Good luck.