Switching Table for Dehydration Unit

[pine05]

Hi, my name is pine and I'm currently have assignment to create switching table for Dehydration using Mol Sieve.

Our client would like to have the unit able to operate in both 2x100% (1 operate, 1 regen, 1 standby) and 3x50% mode (2 operate at 50%, 1 regen)

My questions are :

1. Lets say that the Adsorption time is 12 hrs, and total Regeneration time is also 12 hrs. If vessel A and B during 0-12 hrs is in adsorption mode, while C is in regen mode, what will happen for the next 12-24 hrs ? As both A and B require to be regenerated, thus only vessel C will be running in Adsorption mode. Is this correct ?

2. What will the design of each dryer be ? is it to be designed to handle 100% or 50% flow ?

Thanks

 

[ash9144]

You already answered your own question. If A and B are running they are at 50% capacity. So when C is done regenerating it can go on line with one of the other beds while the other regenerates (ie B stays adsorption and C starts adsorption both at 50% while A starts regen).

 

[pine05]

Thanks for the explanation

But what will happen if at 12hrs both A & B needs to be regenerated?

 

[ash9144]

Then you have ran A & B at 100% for 12 hours instead of 50% as you state in your design. So you haven't designed for that scenario and would therefore need a 4th bed.

 

[pine05]

i see now, so when I run the A&B bed for 50% that means the adsorption time which is previously 12 hours (for 100%) will be longer for 50% (say 24 hours, double the time)

is it correct ?

thanks anyway

 

[ash9144]

Yes that is correct.