3 replies to this topic

[tummalap.chowdary]

hai,

This is T.P.Chowdary, Chemical Engineer from india.

i am working as a process engineer,

i want to design a distillation column (packed one) ,

now problem is how to get F factor,

For this i calculated Flow parameter, then From graph(Flow parameter vs Cg) i taken Cg Value,

now how i can proceed for F factor calculation,

looking for your valuable reply,

[Chesps]

Why do you want to calculate F factor?

In case your datasheet asks for it, you will have to calculate column diameter as per procedure mentioned in link below, Cg and F factor both are capacity related factors.

F= V * sqrt[ (rho-gas) ], where V is superfacial gas velocity in column.

But if you are talking about F or Fp in y-axis parameter (ordinate) expression it is Packing factor can be found in books or vendor's literature based on type of packing you selected for your calculations.

Refer link below
http://www.cheresour...umn-design?pg=2

[tummalap.chowdary]

Thanks for reply,

I intended to calculate F factor is due to relating with HETP (Vendors data),

but you are telling that F and Fp are same, according to me both are different things,

if you see F facotor units are SQRT(pa),
where as for Fp units are (1/M)
From GPDC graph Y axisis is Cs*(Fp)^0.5*v^0.05,

where Cs = V * Sqrt(rho gas/(rho liq - rho gas))

is there any correction required in above statements,

is there any body have HETP data according to packing for Different components since it varying according to Compounds,

waiting for your reply,

T.P. Chowdary

[Chesps]

It is not very clear to me what you want to ask.

But let me tell you, if you are talikg about F factor and not Fp in the GPDC graph y axis parameter then equation for

F factor is F=Vs * (gas density)^0.5

Though HETP depends on the components involved in distillation no body will be in a position to tell you what is HETP you should use.
Unless he has all the information about the separation you are doing.

If you want the guidelines about HETP selection (assuming you are sizing Randomly packed column)

1. Go through last section of "Distillation Design" by Henry Z Kister, or

2. Metal Tower Packing (IMTP) broucher of Koch-Glitsch : There is method for calculation of HETP for their proprietary packings

3. Similarly the same method extended for other random packing types is available in "Encyclopedia Of Chemical Processing" CRC Press page no. 729 I don't know reliability of this reference.

4. You will find good amount of HETP thumb rules in Ludwig's book "App. Process Design for Petroleum & Chemical Plants" Volume 2