Heat exchanger fouling, chemical additive? 1

[willhammett]

Hi all, we have a heat exchanger, shell and tube double pass, no baffles, in which we can only shut it down every 4 months to hydroblast the tube sheet. The differential pressures rise to elevated pressures higher than we like to see after about a month. We want to use a chemical solvant but our problem is that it needs to be able to get into our foodgrade process stream. We have anthracite sand and garnate multimedia filters downstream. What is a good chemcial to use? And supplier in the southeast US?
We have brought in a supplier from chemtreat but he has been less than professional so we would rather not purchase from him.
PS- the heat exchanger regularly handles flows around 600 gpm of a substance at 65 brix and heats it from 140F(live steam injection upstream) to 185F

 

[chief]

Have you considered reverse flowing to flush out the deposits. If done on a regular basis, this will eliminate a costly chemical clean shut down.

Offshore Engineering&Design

 

[willhammett]

We have it piped to be able to, but it seems to not be really effective, velocities in the HX are relatively low (pump is located downstream and at a decreased elevation also). I also would like to do a chemical clean while in service if possible. Something to add to my product stream, but I know having it either be foodgrade or nonsoluble to be picked up in the multimedia filters is a lot to ask.

 

[unclesyd]

I don't know of Chemical, other than incidentl contact, that can be directly injected in Food Grade processing system. If you know the fouling mechanism there are a few things you might add without affecting the end product.

As you require hydroblasting to remove the soil I would assume
that it is insoluble.

One thing we have used on soluble materials is an internal spray
system in the head. Depending on your soil this may be a
possibility. We use this approach in heat exchangers used in the production of acid anhydrides where we use the acids as part of the cleaning process. Durin outages for catalyst changing we inject a caustic solution through the internal nozzles to clean any residual anhydries.

On another system we had a problem with a direct steam injection
system where there was a concentration effect which polymerized the product to a sticky mess that coated everything downstream. We solved this problem by using a Steam Injection Mixer from Komax. This mixer essentially eliminated our problems.

There are a number of automatic mechanical heat exchanger cleaning system on the market. Some use sponge balls while the some others use brushes. I haven't used them but have see several favorable reports on their effectiveness.

http://www.komax.com/index.html

http://www.cqm-tech.com/documentation/2_ATCS_Product_Descript

ion.pdf

 

[willhammett]

Thanks for the tips unclesyd, we use a polymer upstream that does not act well with direct steam injection (tetra alkyl ammonium chloride). However, we do have phosphoric acid available to use that we could react off using lime sucrate to form calcium phosphate. Thanks for the tip.
If that doesn't seem effective ill look into the linked products.

 

[unclesyd]

Appreciate the feedback, sounds like you have a workable plan
that has a good possibility of resolving your problem.

You might also look at injecting the steam in two stages using injectors with intense mixing, You could use one to heat the stream prior to injection of the chemical. Again the object is to minimize the concentration effect, chemical and thermal.

You also might want to look at a Turbulator for the tubes in your heat exchanger. I know these work quite well with solid particles. Unknown is how they would work in your system.

http://www.alcotwin.com/turbulators.html

 

[SimonKim]

Have you ever considered to apply ultrasonic scale preventer to remove and prevent fouling in Heat Exchanger? In most industrial fields, lots of trial for fouling removal has been focused to chemical methods and some of trials had good results. However these are still some probelms in cost, shut down for cleaning and environmental matters. Ultrasonic method is a physical method and a very effective way to prevent and remove fouling in heat transfer unit.

http://www.morkoamerica.com