Vacuum tower pressure, reduction

Gas engine drives (valve loss reduction), 469-471 Gas sampling, 519 Gas test meter, 343 Gas-oil recovery improvement (vacuum towers), 297-298, 300 Gasoline production (FCCU product fractionation), 202-203 Gasoline vapor pressure (sampling techniques), 518 Gasoline/octane production loss, 209... 

The reduction of resid in a vacuum tower is a function of the flash-zone temperature and pressure. A rise in this pressure increases production of resid at the expense of the more valuable gas-oil product. 

Lower distillation temperatures can be obtained by the use of steam. In this case the steam does not usually condense in the tower, and the plates contain only the high boiling organic material. The steam acts as an inert carrier that is easily condensed and does not have to pass through the vacuum pump. In some cases the temperature gradient in the distillation column may be so great that the steam will condense in the upper portions, and it should be withdrawn. If too much water collects on a plate, it may seriously interfere with the fractionation if the water runs down the tower, it will vaporize on the lower plates and this steam recycle in the tower can overload the unit and seriously interfere with the fractionation. Theoretically it is possible to fractionate a material with a very low vapor pressure by the use of steam distillation, but the steam consumption increases as the vapor pressure on the component decreases. Reduction of the total pressure reduces the steam consumption, but if the vapor pressure of the com-... 

---