×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Pressure drop through an adsorber
3

Pressure drop through an adsorber

Pressure drop through an adsorber

(OP)
We are designing a very simple process air dryer using a desiccant in a packed column.  I need to estimate the pressure drop of the airflow though the column.  Can anyone point me to the resources to help?

RE: Pressure drop through an adsorber

Consider these values:

Minimum: DP/L = 0.01 PSI/FT

Delta P
------- = Aμ V + Bρ V2
  L

Where Δ -P/L is pressure drop/bed depth, psi/ft
μ is fluid viscosity, centipoise
V is superficial fluid velocity, ft/min
ρ is fluid density, lbm/ft3
A & B are dimensional constants

A & B constants:
(for several Particle Mesh Ranges)

               psi-min/centipoise-ft2   psi-min2/lbm
4 –8 mesh bead       0.0560              0.0000889
1/8" extrudate       0.0722              0.000124
8-12 mesh bead       0.152               0.000136
1/16" extrudate      0.238               0.000210

 

RE: Pressure drop through an adsorber

what do V and V2 stand for?

RE: Pressure drop through an adsorber

(OP)
Thank you.  Two questions:

1. Does "V2" mean V*V?
2. What is the source of this relation?

Thanks again.

RE: Pressure drop through an adsorber


Should be as: V, and V^2, respectively.
The velocity is a single number for given vessel diameter.

RE: Pressure drop through an adsorber

(OP)
EmmanuelTop:

Thanks again, but could you tell me where you got the equation?

RE: Pressure drop through an adsorber


My adsorption technical service training.
You can believe to these figures, they have been verified in the field, many times.

RE: Pressure drop through an adsorber

Take into account the aging of desiccant. The equations I have given apply for fresh beds. Depending on the regeneration principle (pressure-swing or temperature-swing), you will see different rates of pressure drop increments over time - with those encountered in TSA units being much higher as compared to PSA units (most of air dryers). For thermally regenerated desiccants, it's a common thing to see 2 times higher pressure drop when the adsorbent is close to the end of active life.

Depending on service (dew point requirements) you have to choose between Silica Gel, Activated Alumina, or Mol Sieve. If you are in warmer region, select Alumina charge and you'll get the best results. Mol Sieves have higher regeneration requirements but also have lower dew points - it all depends what you need.

Best regards,

 

RE: Pressure drop through an adsorber

you can find the equation in Campbell reference book as well.

RE: Pressure drop through an adsorber

(OP)
What is this reference (Campbell)?

RE: Pressure drop through an adsorber

Google 'ergun equation'.  Your dessicant supplier will be able to give you the pressure drop coefficients for your dessicant.

RE: Pressure drop through an adsorber

Gas Conditioning & Processing - Campbell
or you can refer to GPSA - chapter 20 - dehydration.

If you know the supplier of dessicant that you are going to buy, suggest to get the curve of pressure drop/length vs gas flux across packed bed from them, it will be more accurate.

RE: Pressure drop through an adsorber

Check Unit Operations in Chemical Engineering by McCabe and Smith for packed bed pressure drops. As far as I remember, the Ergun equation is a function of v and v3 (v is superficial velocity)

RE: Pressure drop through an adsorber

skuntz,
Page 17 in the presentation showed you a curve that i mean to you : pressure drop per lenght of bed vs superficial velocity.

Thanks, Laliyo.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources