Gas Turbine Heat Recovery 2

[Nico76]

Hi,

I was hoping someone in this forum would be able to give me some help on a Heat Recovery question.

I am looking at the conversion from flue gas (from gas turbine) to superheated steam through a heat exchanger (Heat recovery). From what I read, with all the variables involved, it is not an easy task to determine/calculate the conversion. At present I only have the exhaust heat and the flow rate of the flue gas. Is there an approximate rule of thumb to determine how much energy in superheated steam is produced by the heat exchanger as function of these two variables?

 

[davefitz]

Thre is a large developed industry specifically addressing the design and supply of HRSG's heat recovery steam generators.

If the entire complex HRSG is to be desinged ( economizers, steam generating banks, superheaters ), then the use of computer programs like GTMax is used.

For simple heat exchanger, such as a single superheater at inlet temperature of Ti,s, and gas turbine exhasut temp of Ti,g, one can estimate the size of teh superheater bank and its efffectivenss using compact heat exchangere theory, sometimes called the e-NTU method.

Assume the gas W*Cp,g is greater than the W*CP,s of the steam ( W= lb/hr, Cp= btu/lb/F). Then assume a competitive design where the counterflow effectiveness is about e=0.85 .

e= (To,s-Ti,s) / ( Ti,g-Ti,s) = 0.85. Knowing Ti,s and Ti,g, you can easily comput the outlet steam temperature, To,s .

The surface area required would be caclulated using e-NTU theory, knowing the overall heat transfer coeficient.

 

[chicopee]

We have a nearby power plant in Ludlow,MA that has several gas turbines for power generation. Exhaust gases are routed to a watertube boiler producing saturated steam which in turn goes thru a saturated steam turbine for further power generation.

 

[Nico76]

Thanks for the response so far.

Because of the phase of the project we are in, we cannot contact any of the companies involved in bidding process for the GTG's and STG's. Also most of these companies are not very willing to provide this level of detail until the order has been placed.

Basically we are generating our own electricity and are using the waste heat of the GTG's for process heating and to drive a steam turbine(s). I need to make a rough evaluation in terms of electricity and steam production versus gas consumption.

 

[rmw]

If you can't find it here, you probably don't need to know it.

http://www.hrsgdesign.com

rmw