Removing turbulators from heat exchanger tubes after overheated solvent formed coke residue inside

[Stefan2211]

Facing a new challenge: We have vertical heat exchangers with 1" tubes (SS316)using turbulators. Overheating of our solvent causes coke deposits inside the tubes which we normally can remove by hydro jetting (heat exchangers without turbulators). However, the turbulators stuck inside the tubes and can not be removed mechanically by pulling or trying to knock with hammer. Chemical cleaning (caustic soda, hydrochloic acid etc. does not work either. We now are pulling the bundle to be able to submerge it in any suitable chemical bath or apply other mech. ways to remove turbulators. Any advise on:
1. chemicals that can soften the coke?
2. Mech way like shock cooling with liquid N2 or vibration? Shock cooling might cause unallowable stress in tube sheet as many tubes are totally blocked, others have only loose partice inside and fluid still can pass through tubes.

Pics attached.
Thanks for any advise

 

[EdStainless]

I know of an application with parallel HX and switch each month and then clean the one out of service. They can go about a year on one but buy then the unit is scrap. If they clean monthly they last 10 years.
Do you have room to go parallel?

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P.E. Metallurgy, consulting work welcomed

 

[Stefan2211]

Yes Ed, but plants are designed for normal operation and not for in-house created problems. Our heat exchangers are already in parallel operation and there is no space anymore. We will buy spare bundles now as the existing ones are probably not suitable anymore for long term operayion.

 

[0707]

From the photo I saw your exchangers are condemned. Meanwhile you can plug the damaged tubes and try to "live" with that situation until you purchase new exchangers. You need to make a root cause analyses, why this happenned. Is this an usual situation? Or something went wrong that the operators of the process doesn´t want to reveal? Ed gave you a good input "an application with parallel HX and switch each month and then clean the one out of service" you will stay with two trains, one spare of the other.With study and imagination you will discover more space. In house problems would be avoided following operating windows and procedures, the root cause analise shall be done.

good luck

luis

 

[Stefan2211]

Hi Luis,

It all started with operational issues. Hx was heated but process fluid stopped so the solvent degraded and formed coke. Cleaning was not possible since the turbulator had to be removed which was the major issue and took 3 weeks. So we will no longer use turbulators as the design capacity is still enough. Right now both hx are running well but we will need to replace the bundles.