Shell and tube exchanger in slurry application

[mhabash76]

We have a horizontal shell and tube exchanger with slurry being through tube side. We used to face frequent fouling and precipitation issues in the tubes that drops heat transfer efficiency and requires chemical and/or mechanical cleaning. What is the best engineering practice for such applications? does it help to put the exchanger in vertical or inclined position? Appreciate all thoughts.

 

[Latexman]

Please characterize the slurry. That way someone who is familiar with that particular slurry or that general type of slurry can add to the post.

Good luck,
Latexman

 

[mhabash76]

The slurry is composed of undissolved calcium oxide and some silicate particles in HBr aqueous solution. This solution is circulated from the reactor through the cooler to remove the heat of reaction while solid liquid reaction is taking place.

 

[gr2vessels]

Several things have to be checked before a meaningfull advice can be given;- note that the fouling rate can be reduced by some increase in velocity, if possible. Also, does the slurry allow additional dilution? Perhaps simply adding more 'water' to slurry, you increase the flow rate, the tube velocity, decrease the fouling rate. Obviously, you need to check the heat transfer rate for the modified inlet conditions, etc.
Try to investigate the possibility of adding turbulators in your tubing, that will decrease significantly the fouling rate.
My two cents, come back if you have more details available for your process.
Cheers,
gr2vessels

 

[Latexman]

Batch process? If so, do you rinse the HX between batches?

Good luck,
Latexman

 

[Montemayor]

You have the wrong type of heat exchanger in this application.

The proper and correct type of unit for this type of application is a spiral plate exchanger. This has been demonstrated empirically in the field for many years. In fact, to be specific, I can definitely recommend Alfa Laval as the key fabricator of choice for this type of unit.

You will find that you can easily eliminate or greatly reduce your downtime in cleaning out solid plugs and obstructions within the unit by using a spiral unit. A spiral will cost more than an equivalent TEMA shell & tube, but in any application it requires less heat transfer area than the Shell & tube because of the excellent film coefficient obtianed with spiral flow. Spirals are also more compact and have a smaller footprint. They have gained a reputation for handling slurries for the last 60 years.