Line Heater Sizing 1

[pipechem]

Ref Thread:

I am newbie in sizing Line Heater. I went through this thread798-204110 thread which is closed now. I hope there are many of you who size the line heaters using Excel spread sheet or other software’s on a regular basis. Any help is greatly appreciated. If anyone has sized it using Promax software, please let me know.

I have the following information:

Gas Flow rate: 6MMSCFD
Oil Flow rate: 120 bbl/d
Preheat Coil Inlet & Outlet Temp.: 60 & 156 deg F
Reheat Coil Inlet & Outlet Temp.: 56 & 80 deg F
Bath Temp.: 185 Deg F
Operating Temp. Preheat: 2500 Psig
Operating Temp. Reheat: 250 Psig
Bath Composition: 50/50 TEG/Water

I appreciate any kind of help...

 

[maddocks]

Can you get us some more details on oil and gas properties? Just simulate on Promax - this one would take no time at all.

 

[pipechem]

Thank you Maddocks

Here are Oil & Gas Properties:

Oil:
Specific Gravity = 0.8
Molecular Weight = 170lb/lbmol

Gas:
Components Mol%
Methane = 85
Ethane = 8
Propane = 5
i-Butane = 1
n-Butane =1

I don't know how to incorporate Preheat and Reheat coils together in a single heat exchanger along with Fire Tube.

This is how I have been trying in Promax:

-I put a mixer to mix Gas & Oil and connected the Outlet to the Tube side inlet of first Heat Exchanger
-I connected the Outlet of tube side to a J-T Valve (to reduce pressure)
-Then I connected the Outlet of Shell side (TEG/WATER) to the Inlet of second Heat Exchanger and Outlet of J-T Valve to the Inlet of Tube side.
-So I get my Heat Duty required for both Heat Exchangers.

But I don't know how to decide on No. of PASSES, Required Coil Length, Area Required for both Coils, etc. because I have on them on two separate Heat Exchangers.

Also, how do I size Fire Tube? Please advise me....

Thank you in advance.

 

[maddocks]

Oh man, you're really getting into the details on this one. Your best bet is to do a multi-block simulation and not worry about the shellside of the heater. If you really need to get into coil sizing, you should contact a fabrication contractor or a consulting group. This is a little complex and tends to be a fair amount of trial and error. For firetube sizing, I usually start with a flux of 10,000 btu/hr ft2 and then adjust slightly to examine my L/D. You can do the preheat coil as 1 block like you described followed with the reheat block and then just add the duties together for your total heater duty. Add a fairly good margin like 15-20% to account for some heat losses, calculation issues, and changing conditions. Installing too small a line heater will be embarrassing.

 

[pipechem]

Thanks Maddocks.

I do the same way how you suggested. Now my concern is Coil sizing. I really need to know this as Line Heater sizing is going to be part of my job. I need to survive!!!

Thanks again.

 

[dcasto]

here's the answer from the teachers :

the duty is 1.25 MMBTU/hr

The preheat requires 110 ft^2 or 10 17.5 ft passes of 2" sch 80.

The post requires 13 ft^2 or 1 pass of 17.5 ft of 3" sch 80 pipe.

The fire tube is a single 16" U tube of 17' by 2.

 

[pipechem]

Thank you very very much DCASTO.

How did you do this? Did you use any software or spread sheet calculations?

I am using Promax software and I can get the duty but I can't get the Preheat and Reheat coil length, area, passes and size. Also the firetube length. Can you please please let me know?

Thank you in advance....

 

[dcasto]

Hanover, now named Exterran has a program called Quicksize. The program was mostly based from the charts and data in Smith Equipment's handbook. Hanover had bough out Smith.

Here is the screen page from a Winsim where I solved the heater flas. I just typed in the proceedure for the water bath heater

 

[pipechem]

Thank you very much DCASTO for sharing this information. I really appreciate it. Since we have Promax to this do, I have to try with Promax only.