Steam trap drop in flow from reboiler fouling?
Steam trap drop in flow from reboiler fouling?
(OP)
Wanted to test my theory with the engineers here. I have a distillation column with a thermosyphon reboiler at the bottom. We have 250# steam going through the tubes of the reboiler and product on the shell. Recently, we think we may have fouled the product side in a matter of hours. As soon as this happened, the steam valve went wide open and the steam flow dropped off. On the discharge of the reboiler for the 250# condensate, there is a ball float steam trap.
What I think may have happened is the fouling is causing the steam to not transfer heat and condense, so that the level in the trap isnt rising as much with condensate. Therefore the float valve isn't opening as much as it did before, and we are possibly steam locking the system.
Does this make sense or have I missed something?
What I think may have happened is the fouling is causing the steam to not transfer heat and condense, so that the level in the trap isnt rising as much with condensate. Therefore the float valve isn't opening as much as it did before, and we are possibly steam locking the system.
Does this make sense or have I missed something?
-Mike





RE: Steam trap drop in flow from reboiler fouling?
Good luck,
Latexman
RE: Steam trap drop in flow from reboiler fouling?
-Mike
RE: Steam trap drop in flow from reboiler fouling?
Good luck,
Latexman
RE: Steam trap drop in flow from reboiler fouling?
Regards
StoneCold
RE: Steam trap drop in flow from reboiler fouling?
RE: Steam trap drop in flow from reboiler fouling?
-Mike
RE: Steam trap drop in flow from reboiler fouling?
Another thought. Rather than having an issue on the product (shell) side, you could have a problem on the steam side. If your reboiler has experienced flooding phenomena on the steam side during its operation, corrosion issues could have arisen thus jeopardizing the heat exchange performance.
RE: Steam trap drop in flow from reboiler fouling?
Good luck,
Latexman
RE: Steam trap drop in flow from reboiler fouling?
It's a once thru reboiler design. Weird thing we tried was raising the level of the column bottoms, which dropped the steam flow off. Then we lowered the level in the column bottoms and the steam picked up. It actually keeps picking up very slowly.
It's very counterintuitive
-Mike
RE: Steam trap drop in flow from reboiler fouling?
For thermosyphon reboilers (aka natural circulation calandrias) with steam on the shell and process in the tubes (vertical), liquid levels in the column are generally maintained at a point corresponding to the location of the top tubesheet of the calandria. Greater capacity can be obtained by lowering the liquid level, at least to a certain point. Beyond this point, the top portion of the calandria is starved for liquid so that heat transfer results primarily by heating the vapor. The vapor normally contains sufficient liquid so that the vapor is not superheated. However, poor heat transfer results because the heat transfer occurs in the vapor phase rather than as a result of boiling. The increase in capacity obtained at lower liquid levels is modest. The decrease in heat transfer at levels below the optimum point is dramatic and rapid. Lower liquid levels may require additional surge capacity in the column. Liquid circulation rates are reduced at lower liquid levels with increased fouling and higher maintenance costs the typical result, especially if the top portion of the calandria is not
adequately wetted.
The optimum liquid level depends upon the system. The optimum can be predicted with confidence, but the final point must be established by observation because it is not always
possible to accurately predict pressure drop in two-phase systems, the effects of product composition, and the piping arrangement for the system. For most systems, the optimum point
results when the column liquid level corresponds approximately with the mid-point between the two tubesheets of the calandria.
Looks like you are seeing this phenomenon in your equipment too.
Good luck,
Latexman
RE: Steam trap drop in flow from reboiler fouling?
Maybe that is what is happening. We'll keep adjusting until we get it right or just boil it out and start over.
Thanks for the replies!
-Mike
RE: Steam trap drop in flow from reboiler fouling?
I believe the book "A working guide to process equipment" by N. And E. Lieberman discusses this kind of problem in chapter 11 "Steam and condensate systems".
"We don't believe things because they are true, things are true because we believe them."
RE: Steam trap drop in flow from reboiler fouling?
-Mike