2 replies to this topic

[y2serious]

Hi,

This is my first post in the forum. 

 

We have a vacuum distillation column to separate glycol and water. The pressure is maintained by an ejector to remove the non condensables from the condenser of the column. The vent from the ejector goes into another condenser. the condensate from both the condensers (ejector and the column) goes to a hot-well by gravity and a percentage of the condensate is pumped as reflux back into the column.

 

During a modification, the bottom section of the column (stripping section) was replaced with packing. Valve trays were retained in the top section. The condenser was replaced with a new condenser with changes in CS tubes to SS. 

 

Fluctuations in the column pressure were observed initially for a short period of time. Gradually the pressure remained on a higher side permanently. (50% increase in pressure). 

 

During the next shutdown, Condensate wash of condensers, reboilers, ejectors was done without any improved results. Recently, the pressure remains on a higher side (for 3-8 hrs) and comes back to normal (for 2-14 hrs.). There is no cyclic pattern observed in their time intervals. No other changes in feed, reflux, reboiler steam, steam pressure is present before the pressure starts increasing or decreasing.   

 

The pressure rise takes approx. 15-20 mins. During the same time top and bottom temperatures rise and the column mid temperatures drop. Due to the mid temperature drop the re-boiler steam is increased. The hotwell level drops at the same time as pressure rise and becomes normal after it reaches the high pressure. Similar kind of reverse pattern while pressure drops. 

 

During the low pressure operation, it operates steadily at a constant pressure. During the high pressure operation, it fluctuates + or - 10 mm Hg. 

 

The main challenge is the unpredictability in the column pressure. It remains high for 3 hrs in one case, for 6 hrs. in one case, for a whole day also in some. And this fluctuations happen- every day. 

 

What type of column or condenser or ejector malfunction can explain this patterns? Can there be such a kind of intermittent air leakage?

Edited by y2serious, 29 July 2015 - 03:31 AM.

[Bobby Strain]

You haven't relayed much information. A picture is worth a thousand words. And you can give us details on size, operating pressure etc.

 

Bobby

[breizh]

Hi ,

 

It may be possible that Ice builds up !

 

Consider Bobby's advice and provide more info .

 

Breizh

Edited by breizh, 29 July 2015 - 08:09 PM.