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Heat Exchanger Financial Evaluation


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#1 Maankhalil99

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Posted 02 May 2021 - 03:23 AM

Hello, 

 

I am having a case at my industry where we are trying to evaluate a series of crude heat exchanger in such a way that we want to set a plan to clean heat exchangers not based on the fouling factor. 

 

This is due to the consumption of FG that will be increased once the exchanger duty start to reduce. 

 

   

 

For example, for Exchanger B in the attached diagram, once its duty starts to reduce, more FG has to be consumed in order to sustain the heater outlet T. I want to look to it in a way that we start the cleaning of the exchanger once the extra FG consumed OPEX is equal to the cleaning cost (assuming $20K). 

 

I am not sure if this is a practice in the industry. Otherwise, please let me know about better approaches.

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Edited by Maankhalil99, 02 May 2021 - 03:24 AM.


#2 StealthProg

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Posted 02 May 2021 - 04:33 AM

What you should do is calculate the cost of not cleaning the heat exchanger. Cleaning it is a relativey quick activity whereas running for an extended period with low furnace preheat (due to fouling) could be very costly. You should take all costs into account not just the one you mention. (Although re-reading your post that maybe what your saying?). If so then this is normal practice.

Edited by StealthProg, 02 May 2021 - 04:36 AM.


#3 Maankhalil99

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Posted 02 May 2021 - 06:38 AM

What you should do is calculate the cost of not cleaning the heat exchanger. Cleaning it is a relativey quick activity whereas running for an extended period with low furnace preheat (due to fouling) could be very costly. You should take all costs into account not just the one you mention. (Although re-reading your post that maybe what your saying?). If so then this is normal practice.

 

Thanks for stepping by and replying!

 

What I meant by the cost is two scenarios and deciding on which one is the best: 

 

1. The cost of not cleaning the exchanger unless its Fouling Factor is hitting the max limit. This will be directly related to Excess Fuel consumption in the heater. 

 

2. The cost of cleaning the exchangers periodically in such a way where my Fuel Consumption cost will never be higher than the cost of frequent cleaning.  

 

is that what you are referring to as "all costs"?

 

I hope it is clear. 


Edited by Maankhalil99, 02 May 2021 - 06:39 AM.


#4 StealthProg

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Posted 02 May 2021 - 02:35 PM

Ok, for a preheat train i would not do anything based on fouling factor as it does not neccesarily relate to economics. (One exchanger fouling up may or may not have significat impact on preheat).

Clearly if the cost of cleaning is not recovered by improved preheat its simply not worth doing. So yes i suspect we agree in that to maximise benefit, ideally you would clean the exchanger (assuming you know which exchanger is actually causing the drop in preheat) at the optimum time. The optimum time is not neccesarily at the first point you are able to recover the cost.

Edited by StealthProg, 02 May 2021 - 02:36 PM.


#5 breizh

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Posted 09 May 2021 - 02:26 AM

Hi,

To understand , do you have a way to by pass the HXs for cleaning without stopping the train ? 

If not you have to consider the cost of a shut down for cleaning HXs .

Breizh 






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