2 replies to this topic

[TestTest_UK]

All,

We have zeolite beds at our facility to dry (ie remove water) hydrocarbons (in this case butene).

There is one duty bed and one stand-by bed.

Regeneration if the bed is done in 4 steps:

1. empty duty bed to stand-by bed

2. depressurise emptied bed to flare

3. flush depressurised bed with ambient nitrogen (4 barg)

4. regenerate bed by flushing with hot nitrogen (4 barg)

Bed is flushed top to bottom.

During step 3, we notice temperatures gradually drop over time down to -70°C => there it flatlines shortly to then increase again (range of temp transmitters < -100 °C)

Originally bed was designed for only - 40°C => we're investigating whether we have a mechanical problem and if so how to solve it.

I think that low temperatures are linked with the low partial pressure of the evaporated butene in the nitrogen.

It is not clear to me what mechanisms really drives the temp to stop at around - 70°C and then increase again and what the handles are to counteract the temp drop (or what prevents it from dropping further)?

Any thoughts on this situation?

[Pilesar]

Are you saying step 3 and 4 are performed with the vessel pressure controlled to 4 barg? How low is the pressure during step 2?

What are the materials of construction of the vessel and piping? What is the normal operating pressure before step 1?

Just because the vapor temperature is cold does not mean the vessel metal is as cold.

Ways to keep temperature up:

1)  Allow more time in step 1 to drain all the liquid.

2)  Add nitrogen at a faster rate in step 3. 

[breizh]

Hi,

What says the operating manual?

This should be well described. You should have malfunction scenarios and remedies.

Both beds are concerned or only one?

BTW did you contact the manufacturer of this technology? I guess a lot of these equipment are sold worldwide and they should have enough return of experience.

 

My 2 cents.

Breizh