Reducing Plate Heat Exchanger Fouling 2

[chino101]

Hello all,

I’m a intern engineer at a new combined cycle power plant. I’ve been recently assigned the task of evaluating the performance an installed plate and frame heat exchanger. One of the biggest problems with this plate heat exchanger is that it has the tendency to foul up relatively fast on the cold fluid side since we are using brackish water. The hot side is clean closed cooling water so there is no problem there. But what can be done to minimize the fowling of the cold fluid side? I have gotten the suggesting that increasing the flow rate on the cooling side would be able to minimize the fouling, do you guys have any other ideas or experiences with plate heat exchangers that you’re able to share with me?

Thanks in advance.

 

[pmover]

without knowing actual process conditions (i.e. duty, temperatures, flows, fluid, pressure), i gather that the hot fluid temperature is high enough to cause the fouling.

A requirement for plate frame exchangers is that they require clean fluids, or they will easily foul or plug the small flow passages within the exchanger. it is my understanding that plate-frame exchangers do not "operate reliably" under high temperature differences as the gaskets will fail (NOTE: my understanding and limited experience. A heat-xfer specialist would know better.)

plate-frames exchangers are desirable for the small plot space they take up, when compared to shell and tube exchangers.

increasing the flow rate will not likely solve the problem, depending upon hot fluid temperatures. recommend contacting the vendor. it would be beneficial to know the film temperatures, something the mfg should be able to provide and that value will provide you a good indicator for fouling for each cold fluid flowrate run done by the mfg.

1) is it possible to use a clean source (i.e. mineral free) of water instead of the brackish water. i'm thinking to take a clean source of water, pass it through the plate-frame exchanger and then use the water as make-up water somewhere within the system (will need to know make-up rates, etc). somewhat of preheating make-up water before usage in power system.

2) clean the brackish water before entering the exchanger (could be costly, depending upon capacity needed).

3) is there another source of clean fluid that can be used as the cold fluid? this is really what is needed.
good luck
-pmover

 

[25362]

As in a previous message I suggest to intercalate another closed circuit using tempered water (TW) which would be soft or demineralized to cool the warmer stream. This TW would itself could be cooled by circulating cooling water or in an air cooler.

This means revising the present system concerning heat transfer, and the expense of installing the new TW system.

 

[vpl]

chino101

If you can get your hands on EPRI TR-107397, Appendix F tells you how to evaluate the performance of a plate heat exchanger. It's basic heat transfer. Otherwise, get your college heat transfer book and check back in. I can help walk you through the evaluation. Unfortunately, increasing the flow is not likely to be the best solution. Do you have any leeway in any of your other parameters? Patricia Lougheed

Please see FAQ731-376 for tips on how to make the best use of the Eng-Tips Forums.

 

[chino101]

Thanks everyone for all your help and insight.

VPL, I was able to find the EPRI report TR-107397, and it has everything that I was looking for, thank you!

 

[Mechy]

I think increasing the water flow rate can at least decrease the fouling. Lower water temperature at the interface will decrease the "baking" effect.

It is not the best solution and I agree that a clean water source is what is required here.