The cleaning of spiral wound heat exchanger in Rectisol unit

[hazel]

Does anyone have the experiences of cleaning spiral wound heat exchanger? Especially the exchangers are operated in Rectisol Unit.

The feed gas is 65% H2, 33% CO2, 0.5% H2S and contained traces of soot and heavy metal. This feed gas entered the shell side of the exchanger and a part of the soot and heavy metal deposited among the outside of tubes. The exchanger’s performance worsen gradually after fouling is increasingly.

The tube material is stainless. I have cleaned it with soda solution and NH2SO3H solution, but the result is bad. We can not see any improvement after cleaning, although the cleaning solution was dirty.

I would like to know if there are other methods to clean the shell side of the exchanger.
I am appreciative if you can give me any advices

 

[europipe]

We had the same problem with an exchanger.
I should say; clean more.
The plant wanted to increase the interval between shutdown from a half year to 2 years.
They could throw away the exchanger.

 

[StoneCold]

Hazel
Is it an all welded unit or does it have a removable side?

What about soda or sandblasting it?

If it is carbon buildup maybe you could do a controlled burn out of the material, but you better get help from someone with experience doing that.

Regards
SToneCold

 

[hazel]

Thank you for help.

In fact, it is an all welded unit. There are only two nozzels,12 inches and 14 inches, for the shell side and could not remove the tube at all.
Could sandblasting be applied in such case?

I have no idea about to burn out the deposits. Is it easy and safe to contol during the burning process? could it damge the tubes during the process?

Dear SToneCold, Could you give me more information, please?

Thanks

Best Regards,

Hazel

 

[hazel]

I have tried injecting steam into the drain located on inlet of chemical cleaning and hoped it caused water hammer which can loosen the deposites. But it did not
work, even the drain was damaged by the vibraton.

 

[sshep]

Burning works good for coke, the residue left behind in vaporizers, and inside the tubes of fired heaters. It can be done using an electrical heater and an air compressor, but I wouldn't give up on chemical cleaning yet. You said the chemical cleaning seemed to be working from visual observation of the dirty solution. Perhaps a different cleaning solution, higher circulation rate, longer circulation, or more temperature is needed.

Did you circulate the solution or just soak? Were you able to get a sample and make a laboratory test (weigh, add solution, heat, let disolve for 24hours, decant, dry, weigh again)?

A typical bundle has all sorts of dead area and the solution takes the easiest path tending towards the center, heavily fouled areas get less flow so more overall flow rate can help. I am gathering that when you said spiral wound you mean a spiral baffel layout. Hopefully this can work to your advantage (less dead area).

What is the material of construction of the exchanger?

best wishes,
sshep

 

[chief]

There are many proprietary tube cleaning chemicals on the market, normally used for boiler de-scaling and heat exchanger cleaning. One I have had good results with is Drew Ameroid's SAF-ACID. Force circulate with a pump and use a little heat for optimum effect. The addition of a cupful of salt increases the activity as does the use of a little aeration.
Use the usul safety procedures when handling chemicals.

Offshore Engineering&Design

 

[hazel]

Thanks all of you.

The shell of exchanger was made of A537.
We had chemical cleaning in folloing procedure,
1.Isolated the exchanger and drain out the residuals.
2.Clean the exchanger with water.
3.Operated the soda circulation in 60?, and the solution pH value was control at 12. This step continuously operated 14 hours.
4.After draining and cleaning the exchanger with water, start the NH2SO3H solution which runned about 4 hours.

Next time, we will raise temperature before the circulated pump cavitated. We also want to put some plastic balls in the circulation. Does anyone have such experience of the ball circulating in shell side of exchanger?

 

[unclesyd]

You might checkout this process Aimm Technologies.

http://aimmtechnologies.com/experience.html

Here is information on Pyrolysis of organic materials. This will eliminate the organics but will leave the metallic oxides.

http://www.pcpconline.com/

It will be extremely hard to remove the carbonaceous products with chemical cleaning but you should be able to remove the oxides.
Here is Oakite products which I've used for over fifty years.

http://oakitestore.com/

What is physical size of you exchanger?

 

[hazel]

The tall of exchanger is about 10 meters and diameter is 2.4 meters.

How about the ultrasonic transducer? Could it be apllied in this case?

 

[unclesyd]

I've personally not used this process but have talked with people who have and who were quite satisfied with the results.
I personally would give Aimm Technologies a call at the home office.

Please let us know the response?