Steam Generation from Tower Condenser

[sshep]

South Africa is in an energy crisis. I want to generate 4barg steam from some tower condensers that are currently using fin-fans. The equipment will go on a structure between the tower and the finfan bay. Process side will drain to the existing reflux drum.

Can anyone give me some advice the exchanger design? I would like to get recommendations on the exchanger type and layout- horizontal orientation would be best, but any proven design will be useful.

best wishes,
sshep

 

[gr2vessels]

Perhaps a kettle type of reboiler per TEMA, or you hang a vertical reboiler on the side of your column, or use a stab-in U-tube if you have a handy manway available;- many ways to skin a cat (except my cat!)
Cheers,
gr2vessels

 

[HeinrichK]

Depends a bit on the plot layout off-course, but as gr2vessel says, you will probably end up with a BKU / NKN type condenser.

I don't know what you are condensing, but have a think about the control scheme. You might want to keep your aircoolers if outlet temperature is to be controlled.

 

[Homayun]

Maybe a silly question, but where would you use 4 barg steam for?? there aren't many places where you might be able to use it...have you done a proper research as to whether you really can use 4 barg steam??

As to exchanger type, I would go for a kettle design with water in the shell side...you might control the level in shell to control the condensing duty.

 

[sshep]

Thanks for your advice. I have several examples of generating steam using a thermosyphon type arrangement in a vertical exchanger, but nothing with a kettle. Does anyone actually know of a kettle style installation?

My calculations show that I will need about 250sqm of heat transfer area using a condensing temperature on the process side of 175C. We will be keeping the fin-fan and just put an excahner upstream and in series. We have plenty of 4 barg users as another part of the process boils C5's and C6's.

Thanks again,
sshep

 

[CJKruger]

sshep, kettle type steam generators are used a lot. Till recently I had few problems with them.

Currently we are struggling with one that intermittently carries over slugs of water.

I think the key is to design it correctly so you have enough disengaging space and the appropriate internals.

 

[Chance17]

Why not consider a heat pump ??
see attached

 

[HeinrichK]

@Yitbos: because it is an existing situation. It appears something you could consider for a new project, although I've never seen it outside my fridge

@SShep: Regarding a vertical thermosyphon, i refer back to my previous post: have a look at the required control scheme. I don't see how to get it working. I suppose you have see them working as a reboiler underneath a column, not as a condenser.
I can assure you that there are a lot of plants with a kettle type 'waste heat boiler'. Chosing a kettle type instead of a thermosyphon makes the control scheme easier as well.

 

[katmar]

This is a bit off-topic, and you may have it covered already, but I know that at one stage the South African definition of a boiler was "a device which generates vapours from a source other than steam". You may need to register your exchangers as boilers rather than as pressure vessels. It's not a big deal, but you need to get specific exemptions from the requirements for standby water pumps, multiple level gauges etc.

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