8 replies to this topic

[rosneft]

Hi, 

 

I was wondering if anyone can provide me with some guidance and good sources of information regarding heat exchanger design for natural gas preheating.

 

sources: Books, Blogs, articles or just replys would be highly appreciated.

 

I am looking at heating 7400 kg/h natural gas from 3C to 22C. Inlet pressure is about 950 PSI and the pressure drop should not be more than 12 PSI. 

 

Any industrial guidance would be highly appreciated.

 

Thanks

[srfish]

Several books are:

    Process Heat Transfer by Serth

    Heat Exchanger Design Handbook

    A Working Guide to Process Equipment by N. Lieberman & Elizabeth Lieberman

 

It would also help if you would tell us what the heating medium is.

[ankur2061]

Rosneft,

 

The kind of application you mention would be best served by a water bath heater. Normally you only specify the process parameters for a water bath heater and leave the thermal / mechanical design to specialized manufacturers / vendors. Refer the attachment.

 

Regards,

Ankur

 

 

Attached Files

•  spt-indirect-heating-brochure.pdf   1.63MB   2886 downloads

[rosneft]

Several books are:

    Process Heat Transfer by Serth

    Heat Exchanger Design Handbook

    A Working Guide to Process Equipment by N. Lieberman & Elizabeth Lieberman

 

It would also help if you would tell us what the heating medium is.

SRFish,

 

Thank you for the sources. One of the tasks is to decide on the heating medium. I am contemplating low pressure steam Thermosiphon HE with a finned immersion heater. 

It's an open question for an innovative design idea.

 

Rosneft,

 

The kind of application you mention would be best served by a water bath heater. Normally you only specify the process parameters for a water bath heater and leave the thermal / mechanical design to specialized manufacturers / vendors. Refer the attachment.

 

Regards,

Ankur

 

Ankur,

 

Thank you for the post and attachment. I am actually interested in the thermal design, type of HE, suitable mediums, size, heat load, safety and reliability...

I do have the rudimentary HE knowledge from university but other than that I'm a novice in HEs, as it is probably clear 
Guidance is always appreciated. 

Edited by rosneft, 09 September 2016 - 05:12 AM.

[srfish]

A thermosyphon is out because nothing is being vaporized. In the case of a finned immersion heater, what are you immersing in? In the case of low pressure steam as a heating medium, I suggest using a BEU type of heat exchanger.

[rosneft]

A thermosyphon is out because nothing is being vaporized. In the case of a finned immersion heater, what are you immersing in? In the case of low pressure steam as a heating medium, I suggest using a BEU type of heat exchanger.

Srfish,

Thank you for the reply.

Sorry, the thermosyphon 'idea' is not really part of this HE design. I got overly excited. I was thinking about a secondary immersion vacuum vaporizer providing the low pressure steam which would then be used as the medium to heat the gas (eg. in the tube BEU side). But that's not part of the initial design. The steam would cool as it comes in contact with the flow tubes (in the case of BEU) and condensing returning to the vaporizer in liquid using gravity, removing pumping.

But the preliminary simple design is just the HE as innovatively as possible (with commercial application). Hence the idea of placing fins on the exchanger tube side to maximize heat transfer and make the system more compact. 

I was wondering if this would be a viable design?
Any constraints that you can think of based on experience? (I assume maintanance dificulty, fouling...)

Or shall I stick to a smooth tube side design?

Thank you in advance.   
 

[srfish]

Since the gas is only being heated 20 C., I wouldn't use any kind of the more expensive extended surface,

[IGC]

Where is the site?  Even just the country would help!

 

Depending on the composition of the natural gas, I get a required duty of around approx. 110 kW to raise the temperature from +3degC to +22degC.

 

If your foot print is a cause for concern, then a direct contact immersion heater could work.  This is similar to a BEU style shell and tube, with the gas on the shell side and your tube side being U-shaped cartridge heaters, fixed in a tube sheet. Baffles are installed on the bundle as well.  You would have no issue with your 12 psi pressure drop.  Shellside design pressure would make the pipe schedule quite thick, but manageable.  

 

You can model this in HTRI if you want by fixing the tubeside heat transfer coefficient very high with a single tube pass.

 

After than you could look at an indirect water bath type trim heater.  You have a tube bundle inside a water bath, and you heat up the water bath using a heating medium, be it steam via sparging or a gas burner into a combustion chamber.  With the size of the unit you are looking at, I'd estimate the steam heat exchanger to be cheaper, assuming you have the steam readily available already.

 

Direct contact with the steam is probably not necessary considering the amount of heating you are doing.  It would be a tiny heat exchanger considering the LMTD you would be facing, and controlling it would be a pain!

[DB Shah]

If in a hot country where cooling water return temperature is high (~43C), you can heat it up against CW return, saving energy. Hex might be about 20M2