Gas Turbine / Hot Oil Waste Heat Recovery

[KenA]

I am looking at a conceptual design for a plant which includes GE Frame 9 Gas Turbine generators with waste heat recovery to a hot oil system. The system is very large and I'm interested to hear from anyone with experience of similarly large units or for names of vendors who could offer this type of hot oil system. I don't see why it can't be done but have yet to see a similar unit on a similar scale.

To give you an idea of the design:
(1) It is proposed to heat the oil using waste heat recovery from the exhaust gases from GE Frame 9 gas turbines.
(2) The total heat load on the hot oil system is around 250 MW and would be divided into 2 units with one spare.
(3) It is proposed to use hot oil around 300 C at a flow rate of 2770000 kg/h.
(4) The hot oil will be used to transfer heat to process fluids in conventional shell & tube type heat exchangers.

 

[MJCronin]

kenA...

A lot of chemical process plants use gas turbines with matched, attached HRSGs to generate steam. Steam has a lot of advantages as a heat distribution media

The advantage with the use of steam, of course, is that it does not have to be pumped....it goes where it must "for free". Furthermore it is significant that the design, maintenance and operation of HRSGs is well known and understood

Steam is distributed throughout the plant and can heat various hot oil systems at the point of "use" as required.

Yes...yes, I know that you must purchase and operate all ancilliary raw water, condensate etc systems..

But I suggest that you stay away from any "unique" hot oil heat recovery designs.

My opinion only...

MJC

 

[MisterDonut]

NenA,

This is not unheard of. Gas turbine waste heat recovery can be applied to hot oil, Dowtherm, etc.
Possible vendor:

http://www.deltak.com

 

[pmover]

there are gas processing plants utilizing hot oil (Dowtherm) in waste heat applications (i.e. from gas turbines) for other processes.

perhaps dowtherm can provide you a reference list (check online too).

good luck!
-pmover

 

[JLSeagull]

I am aware of an international offshore project that included several waste heat recovery units on GE LM2500 turbine driven compressors. The waste heat recovery units were furnished by Tulsa Heaters. The heating medium was a grade of Dowtherm.

When designing or selecting the heater, consider issues related to the potential hot oil tube rupture, potential for a Dowtherm fire ignited in the exhaust, what to do in the event of a tube rupture or fire, how to detect the fire such as an elevated stack temperature or visual effluent display, etc. Consider arranging the tubes in a manner that would prevent the hot oil from pouring directly into the turbine exhaust.

Determine whether or not you need supplemental firing. Determine whether or not you need to be able to fire the duct burner without the turbine exhaust for combustion air during dryout, etc.

Write a very good specification. Make the vendors agree. Establish a large engineering coordination budget. Very large. Make GE and the heater vendor sit in the same room until the issues above are resolved to everybody's satisfaction. Include a large engineering coordination budget. Very large. (Yes, I know that I am repeating myself - and I am showing lots of restraint.)

 

[MJCronin]

To all....

Ummmm...large.... very large.....Hmmmmmm..

My suggestion of the serious consideration of a steam distribution system is based on this massive heat load that must be distributed to several locations.

Distance is a factor also

I believe that a massive and redundant pumping system for a large system is a major cost consideration

Will this be one of the most massive, largest pumped hot oil system in the world ...???(you have a huge gas turbine here) If so, IMHO consider the SYSTEMS, OPERATIONS AND LAYOUT ADVANTAGES that a steam system offers.

Tell us more about the number of heat users and the maximum distances from the GT to the users..

My opinion only

-MJC

 

[rmw]

I had a client who fell out of love with steam (one reason being the latent heat loss) and built his subsequent systems with hot oil. This was a wood fired application. I was (and am) an old steam guy but I had to grudgingly admit that he was right and his hot oil system worked just fine.

And, MJC, steam has to be pumped too, or the water that becomes the steam does, that is, so it isn't like steam doesn't have some pumping costs. In the example above, his oil pumps were a lot more trouble free than the BFP's in his earlier steam plants (which I made lots of billable hours messing with and fixing for him).

Back to KenA. One thing you have to consider is the approach temperatues especially in light of the exhaust temerature of the typical gas turbine and make sure that your system is designed so that the proper velocities are maintained in the heat exchanger tubing, especially in the zones that are nearest the exhaust inlet. Those who know how to design hot oil systems know how to make this work right; be sure to consult with someone who knows.

rmw

 

[KenA]

Thanks folks for all the advice/help. All valuable.

MJCronin - I happen to agree with you with respect to steam HRSGs but the conceptual design has been prepared "by others" for a client and we are simply commenting upon it.

MisterDonut - thanks - I've dealt with Deltak in the recent past and would work with them again.

JLSeagull - I hear what you're saying! Past experience with GE turbine and A.N.Other HRSG leads me to believe that you can never overestimate the engineering coordination hours. Thanks also for the other advice. The GE LM2500 is much smaller but I guess that it shows that this type of thing has been done in the past. Just the small question of whether anyone would like to do it on the back of a Frame 9.

KenA