6 replies to this topic

[curious_cat]

We have a badly fouled condenser with cooling water on the shell side (no clue why the designer chose to condense on tube side!). Since the tube sheets are fixed it is hard to do a conventional hydrojet cleaning since I cannot pull out the tube bundle. 

 

Do people have any other ideas? A chemical cleanup with sulfamic acid didn't help much. 

 

The exchanger is pretty small; ~20 m^2 in area and straight Mild Steel tubes. 

[Art Montemayor]

Curious:

 

Depending on where you are located and your operating and maintenance budget, I would speculate you have two options:

1. scrap the unit and go to a properly designed one.  Whoever decided to condense on the tube side obviously was engineering-challanged;
2. remove the shell and the tubes.  All you can really salvage are the tubesheets and the two bonnets - assuming this is a BEM.  Hopefully, the tubes are rolled, and not welded.

I've done this one before, when I was managing a plant that was on the brink of bankruptcy and I had to try to save it from going under in production.  I salvaged the heat exchanger and saved the plant.  My problem was that well water was being used and it had considerable dissolved solids that subsequently precipitated in the shell side of the BEM.

[srfish]

A book called " A Working Guide to Shell-and-Tube Heat Exchangers" by Stanley Yokel has a section on cleaning methods. He discusses chemical cleaning of exchangers in cooling-water service. There is a grouping of four different types of fouled material.

[curious_cat]

My problem was that well water was being used and it had considerable dissolved solids that subsequently precipitated in the shell side of the BEM.

 

Deja vu! Some time back in the history of this HEX it used to run on well water too. Sigh.

 

Thanks for the tips though!

[curious_cat]

As a follow up: The rather ineffective sulfamic cleanup was followed up by a 10% HCl wash for 4 hours. After all, no harm in trying if the HEX is otherwise destined for the scrapyard anyways. 

 

That seems to have worked quite well. Condensate rate has been  boosted by 40% already. Still far away from the designed flows but some progress. 

Edited by curious_cat, 08 August 2013 - 08:04 AM.

[Art Montemayor]

Curious:

 

I'm glad you have made a break-through the carbonate solids build-up in the shell side of your BEM unit.  Acid is capable of removing the solid mass - albeit, very slowly.

 

My experience in doing an acid wash is:  Be VERY, VERY careful in pumping in acid solution into the shell side.  You are generating CO2 gas as you dissolve the mass of carbonate solid inside and the pressure can build up quickly if your outlet is partially plugged up with solid particles that break out from the main mass.  The result can be a massive gas eruption out of the shell side outlet and if you are not careful and have everyone strictly dressed in proper acid-proof clothing and shields, you could have a serious acid-related incident.

 

Don't push or try to accelerate the break-up of the carbonate mass inside.  Let it take its time and dissolve and breakup slowly so the pump doesn't build up any back pressure.  Use only HARD piping on the exchanger outlet, leading to a dedicated sump or vessel where you capture the acid solution for recyle and separation of the dissolved gas.  Don't forget: you are creating a 2-phase flow - or worse, a 3-phase flow.

 

Good Luck.

[curious_cat]

Curious:

 

I'm glad you have made a break-through the carbonate solids build-up in the shell side of your BEM unit.  Acid is capable of removing the solid mass - albeit, very slowly.

 

My experience in doing an acid wash is:  Be VERY, VERY careful in pumping in acid solution into the shell side.  You are generating CO2 gas as you dissolve the mass of carbonate solid inside and the pressure can build up quickly if your outlet is partially plugged up with solid particles that break out from the main mass.  The result can be a massive gas eruption out of the shell side outlet and if you are not careful and have everyone strictly dressed in proper acid-proof clothing and shields, you could have a serious acid-related incident.

 

 

Thanks for that tip. I hadn't anticipated that hazard, no (though all personnel did have the usual safety protection). I'm forewarned. 

 

I never anticipated such a rapid evolution was possible.