5 replies to this topic

[sargon 1979]

Hi all;

I have a problem with dehydration unit (Molecular sieve beds, two in adsorption, one in regeneration with 16 hrs adsorption cycle), your help is highly appreciated;

The problem is:

Dehydration unit is designed to handle (172935 Nm3/hr) at inlet temperature of (27ْC) and pressure (84 barg), the inlet temperature is achieved by means of Propane evaporator now, chiller unit is stopped due to mechanical damage (No standby is available).

upstream of chiller there is an air cooler but the minimum obtained outlet temperature is only 35ْC (35ْC to 50ْC normally). the inlet water content is increased (650 ppmv to 1200 ppmv), i suggested to bypass a slip stream of the inlet gas (60000Nm3/hr) and dehydrate a quantity of (113000 Nm3/hr) so that the water load on the unit remains constant.

I'm not sure about my solution because I'm sure that the capacity of the unit differs with temperature.

 

Thank you very much

[Bobby Strain]

You posted this in the student forum. But the query doesn't seem to be of an academic nature.

 

Bobby

[Pilesar]

You don't say what your downstream unit is, but bypassing is a sure way to get water downstream. Depending on how long your refrig is down, you may be better off short cycling your dryers if you can reduce your regeneration time. If UOP provides your sieve, their engineers will advise.

[Napo]

Sargon,

 

I am accord with Pilesar, you can reprogram the cycles (service-regeneration), I was worked in a Gas Plant the original cycles were 12 hours, after upgrade the cycles were changed to 8 hours.

 

Napo.

[Mahdi1980]

Sargon,

Please answer these questions:

 

1- What is your gas stream? Is it propane or another gas?.

2- what is the phase of your stream, gas or liquid?

3- For which process do you want it?

4- Who is the vendor of the dehydration package and zeolites?

5- Are you sure about the performance and life of your zeolites. Have you ever tested their activities?

6- Do you mean that the inlet temperature of the stream can be achieved to 35 C by aiming the air cooler?

7- how do you regenerate your beds?

 

Clarifying the above items may help us to make a good comment.

 

Regards

[sargon 1979]

The unit is used in our gas plant, the d/s process is cryogenic in order to recover LPG, cryogenic process temperature is (-56℃) and the pressure is 40 barg, turbo expander, demethanizer, deethanizer and depropanizer are the main equipment in lpg recovery section but, we stopped the cryogenic section and we send the gas to export line immediatly after it is dehydrated. Thank you...