7 replies to this topic

[miguel29chem]

Hello,

 

I'm trying to desing the pre-purification system to remove moisture and CO₂ in air after compression for a cryogenic distillation process; the actual inlet air volume flow incoming to the process will be 100.000 m³/h, at 36 °C and atmospheric pressure, with 0,037% moisture.

 

I've been reading and I think the most suitable option would be a TSA “2+1” system, with 16 hours adsorption time and 8 hours regeneration, using 13X zeolite (adsorption at 36 C and desorption at 200 C).  My problem is that I can't calculate the vessel size; I'm using a flow velocity of 0,2 m/s though the bed, and this gives a huge diameter (2,9 m!!), is this velocity accurate?  The other problem is that using a bulk density of 0,64 g/ml, I find a required bed volume of 450 m³!!  and using the 2,9 m diameter, a required height of 70 m for the vessel.

 

Can anyone help me jaja?

[Bodhisatya]

The inlet air generally comes compressed at 5-6 bar(a),  why are you saying it's at atmospheric pressure.

 

We use inlet velocity of 0.19 m/s , so your assumption is correct.

 

Bodhisatya.

[miguel29chem]

Dear Bodhisatya,

 

Sorry, I wasn't clear.  The air enters the plant at 36 ºC and 1 bar; but the air enters the TSA system at 6.9 bar.  According to our simulation, the conditions of entry would be:

 

T = 25°C

P = 689 kPa

N = 3817 kgmole/h

[Bodhisatya]

This sounds ok...Please share your work, will like to dig in and will let you know (if it's not breaching protocols).

 

Bodhisatya.

[miguel29chem]

 

I'm uploading my calculation excel file so you can see it.

Attached Files

•  sim.xlsx   175.95KB   14 downloads

[miguel29chem]

Where it says "Skeletal density" it's actually "Bulk density", sorry, my mistake.

[Art Montemayor]

Miguel:

 

If you really want worthwhile engineering help on your adsorption problem, you have to submit YOUR basic data and detailed calculations - not some computer printout results.  Looking at your spread sheet, that is all that you show us.

 

Without a detailed explanation and calculations, our members can't decide if your results are valid, correctly done, or bad math, bad logic, or bad calculations.  If you have really done the detailed calculations, then submit them with the details of your logical steps.  But if you actually only resorted to using a simulation program to do your design for you, then your problem may be that you haven't inputted the correct data or that your program isn't suited to what you want it to do.  No one can attest to the accuracy or validity of the simulation design you obtain except the people who sold the simulation package - and even they won't guarantee the correct results.

[miguel29chem]

 

 

 

 

Dear Art Montemayor,

 

Sorry for the delay. I was out of the office last week.

 

What I've uploaded here is all I have (regarding the purification process). There is a simulation of the cryogenic distillation process, but it does not include the adsorption system (because the simulator can not simulate it). The data I have uploaded (molar flows) are those the simulator indicates must be supplied to the distillation system to provide the desired oxygen production at the outlet. That's all we have right now.

 

In any case, what happens in the distillation process does not alter what happens in the upstream adsorption system. The mass balance indicates that the data I have uploaded before are those that enter the adsorption. The rest of the data such as flow velocity and bulk density were given by 13X suppliers; I want to know if I'm using right this data, for example maybe I have to use another density value.

 

Thanks.

Miguel.