1 reply to this topic

[Cristoph]

Hi everyone,

We have a naphtha/diesel/Gasoil distillation unit, and distillation expert give us the entire simulation in ASPEN Plus. The distillation tower seams to work; I know that we need from 3 to 10% of overflash that according our heavy naphtha 91% is just fine.

Nevertheless, the transfer line, from heater to column have also 91% of vaporization, and our company design manual says that we must to take care of vaporization (not up to 60%) to avoid heater coking. Now, some other process engineers are proposing to put a control valve in the transfer line to help the expansion and vaporization in that point, which I haven’t seen before in other facilities.

Besides that I just have the VDU transfer line criteria to design with critical velocity, even though I haven design one. The actual path of this line has horizontal and vertical stretches instead the shortest ride with different diameters.

That’s why I ask you:

1. It is possible to have more than 60% of vaporization outside the heater, taking care the film temperature of the heavy naphtha?
2. To put a control valve in the transfer line is correct?
3. What design criteria I should follow to design transfer line in this kind of facilities?

The plant is new, the heavy naphtha comes from gas that goes to a Cryogenic Plant.

Thanks in advance for your help.

Attached Files

•  PFD.pdf   782.51KB   513 downloads

[PingPong]

What are the units of measurement for P , T , W and Q ?

 

There is a big recycle of heavy bottoms liquid, stream <16> , over the heater, so I don't see how it is possible that there would be 91 w% or LV% vaporization in the heater.