2 replies to this topic

[ashrafnew2001]

hello every one im ashraf alnajjar a chemical Engineer im working at a power station right now and now im responsible for cleaning a heat exchanger (shell and tube type) this heat exchanger made of carbon steel shell and copper tubes during first cleaning process the engineers used NAOH to clean the tubes and accidently one of the tubes leaked and the NAOH Deposited on the shell side, my quastion is how can i remove the NAOH from the inside of the shell which chemical formula can i use???

note :
i can not use acid because i dont want to damge the copper tube.
2- im thinking to use a hot water 70 degree centgrate and keep recycling the water in the exchanger till the NAOH is removed will it work???

[kkala]

Welcome ashraf, an opinion to your query can be as follows.
1. Probably a lot of aqueous NaOH has escaped into the shell. Drain the shell into a portable pot, to avoid excessive aqueous NaOH in the shell when you start cleaning. Draining is normally possible for any exchanger.
2. Leaking tube is assumed already repaired or plugged, when you start cleaning.
3. No need to use hot water for cleaning NaOH off (unless you intend to remove other impurities at the same time), you can use cold water instead. You can recycle the water and purge some percentage of the flow (to be replaced with fresh water). In this way NaOH remaining in the shell will be gradually removed as effluent.
4. If there is much NaOH enclosed in the shell, it may be (over)heated at the beginning, when diluted with water. Especially if NaOH content in the solution is high (e,g. 30 - 50% w/w). This may be improbable, but conditions are not known to me. Cannot you disassemble the exchanger, drain the shell well, then wash it with water through a hose? You can also apply mechanical cleaning on the shell and outside of tubes in this case.
5. You could use an agent (probably weak acid) with corrosion inhibitor, as recommended by specialized suppliers But it may not be worth while for one application on one exchanger. Water could do the task, creating more effluent.

[ashrafnew2001]

kkala thank you very much for your replay
1- i already repaired the damge tube.
2-disassembling the heat exchanger is not an option to me at this moment so i made is my last choise.
3- i have now at my desposal a water tank with a circulation system tomorrrow i will recyle water with 50 degree and i will see what will happend.
again thank you for your usefull information.