Waste heat recovery from turbine exhaust - multiple turbines
Waste heat recovery from turbine exhaust - multiple turbines
(OP)
A client wants to recover heat from the exhaust of two turbines to heat oil. The units drive compressors and will be normally running at a high load rate, although there are chances that only 1 turbine be running.
Normally I've seen one WHRU per turbine, but there is a suggestion to use a single WHRU for both turbines. I would like to hear your thoughts about this idea. I see that there could be some savings but reduced maintainability and maybe control complications.
Any idea will be appreciated.
Normally I've seen one WHRU per turbine, but there is a suggestion to use a single WHRU for both turbines. I would like to hear your thoughts about this idea. I see that there could be some savings but reduced maintainability and maybe control complications.
Any idea will be appreciated.





RE: Waste heat recovery from turbine exhaust - multiple turbines
i would not recommend a configuration as you mentioned. i would think that any savings would be offset by the additional instrumentation, equipment, and additional maintenance needed to a dual turbine WHRU.
I'd request for some references for such configurations if this is being discussed.
hope this helps. good luck!
-pmover
RE: Waste heat recovery from turbine exhaust - multiple turbines
Two things about Pmover's recommendation against your proposed configuration. Not knowing about what the oil is that you are trying to heat, if you make the WHRU large enough to serve two turbines, it might do just fine with both turbines at rated loads, but might not be the full 50% with only one turbine pushing exhaust through it.
Second is that your turbine model probably has already had WHRU's added to them, so there are standard sizes and configuratinos out there, albeit more rare for oil than making steam. The 2 on 1 WHRU unit for your service would tend to be more of a one-off type of thing where you won't get any savings from the economies of scale of picking something 'off the shelf.'
rmw
RE: Waste heat recovery from turbine exhaust - multiple turbines
Standardized HRSGs exist for many gas turbines.
Although there have been single HRSGs serving two gas turbines, they are all unique designs and, as I understand, difficult to control. A company called DELTAK has produced some
Usually, the best choice is to take waste heat, make steam and then use it for a variety of purposes....including heating of oil.
Do you already have a steam system at you plant ?
What is the MWe size, make and model of your gas turbines ?
RE: Waste heat recovery from turbine exhaust - multiple turbines
RE: Waste heat recovery from turbine exhaust - multiple turbines
rmw
RE: Waste heat recovery from turbine exhaust - multiple turbines
RE: Waste heat recovery from turbine exhaust - multiple turbines
rmw
RE: Waste heat recovery from turbine exhaust - multiple turbines
RE: Waste heat recovery from turbine exhaust - multiple turbines
It is known that for most STG's, at least 8% MCR steam flow is needed to prevent L-1 blade instability ( aerodynamic flutter) , so to maintain continuous spinning reserve of the STG and fast restart of the main CTG, at least 8% MCR steam flow must be maintained. In regions with large wind farms, the need for a fast restart ( < 15 min) of the main gas turibne is important.
RE: Waste heat recovery from turbine exhaust - multiple turbines
Taurus 70s have been used in both cogeneration and combined cycle service in many installations.
This document gives you a rough idea of the steam generation potential. A detailed heat/mass balance for the plant should be developed by a professional.
ht
RE: Waste heat recovery from turbine exhaust - multiple turbines
rmw
RE: Waste heat recovery from turbine exhaust - multiple turbines
Asuming that each GT doesnot have its own vent stack, then will there be a problem purging the non-shared section of duct when starting the second GT with one GT already running?
Also what happens when starting the second GT and it doesnot light allowing air and fuel from the second GT to combine with the exhaust gases from the first GT?
Regards
athomas236
RE: Waste heat recovery from turbine exhaust - multiple turbines
Different configurations are possible- one possIble config is to use an aeroderivative CTG for the overnight duty unit , with its own HRSG and stack. Generally aeroderivative units have a final gas temp on the order of 900F , which may allow supply of a once-thru, dry fired capable , ferritic tubed HRSG (as opposed to the inconel units from canada). For overnight spinning reserve ops of the STG, only 8-10% MCR steam flow is needed at the LP STG stages- The HRSG might only produce IP steam at (825 F) , and the HP STG may use reverse flow steam ( thru the "ventilation valve") to cool the HP stages of the STG during spinning reserve ops- much like those unitS that load thru the intercept valve.