Anti-icing system for gas turbine inlet is necessary?
YGYang
I am operating 150MW gas turbines, a part of combined Cycle power plant.
During the winter
We extract some hot air from the last stage of the compressor and
supply it into the Air inlet to prevent 'inlet icing'.
And it always causes slight of efficiecy decrease and the output down.
(I hate it.)
'Icing Alarm' is on by the turbien management system at the condition
of Inlet Air Temp from -7C(19F) to 7C(45F) and the relative humidity
more than 70%. and when the alarm is on, we have the Anti-icing System
working.
I think that the Icing Alarm condition mentioned above scopes too wide
and we operate Anti-icing system unnecessarily sometimes.
When I look some other Gas turbines under same weather condition, they
run well without cosidering Anti-icing System.
I beg your wistom and experiences about this problem.
--------------------------------------------------------------
1. Why does Inlet Icing in the gas turbine prevented?
( Does the icing damage the compressor blade? )
-------------------------------------------------------------
2. What is reasonable Temp and humidity range to run the Anti-icing
system.
-------------------------------------------------------------
3. Is there any other way I don't use the Anti-icing System?
-------------------------------------------------------------
4. What do you think the differeces between my gas turbine and those
which don't use Anti icing System?
--------------------------------------------------------------
Pease give whatever it is .
Thanks your concerns!
* Sent from RemarQ http://www.remarq.com The Internet's Discussion Network *
The fastest and easiest way to search and participate in Usenet - Free!
Chad Lueders
the inlet air above 0 C. If you were using the hotter compressed air
to do this I don't see why the efficiencey would be any less than if it
was a hot day outside. I guess I mean that if it is -5 degrees and you
are heating your inlet air to a certain temperature say 20 degrees,
then you should have the same efficiencey as you would on a 20 degree
day. I'm I wrong, is there more to this than I see. It may be
possible that you heating your inlet air too much, and that is causing
the decrease in performance. What is the temperature of the inlet air
if you are heating it? If it is quite a bit higher than freezing, it
maybe that you could cut down on the amount of reheat. Anyone else
with more experience have any thoughts?
Chad Lueders
STRAZ
I have run a number of dofferent gas turbines in teh North-eastern US at
extremely cold inlet temperatures and none of them was equipped with an
anti-icing system. There are two instances that I know of where ice damage
occurred. The first was due to a leaking water wash valve which let water
pass into the inlet when the temperature was about -10 Deg C. The water, of
course, froze and the resulting ice was ingested into the compressor causing
moderate damage to the inlet guide vanes and the first stage compressor
blades.
The second incident was due to warm, moist air from the plant (gas turbines
are located inside) being pulled into inlet through an improperly sealed
inlet housing. The moist air first condensed and the water froze with the
same damage done as in the previous incident.
Both turbines were then fitted with windows to observe the inside of the air
inlet for signs of moisture or leaking valves.
We have the same 'anti-ice" alarms, but they are not connected to compressor
bleed air for control purposes - just indication of an icing condition.
I suggest you install the viewing windows and monitor for moisture formation
and then narrow the range of the anti-icing system accordingly. (Or disable
the anti-ice system altogether.
STRAZ
YGYang <sod...@ichum.com> wrote in message
news:071bb362...@usw-ex0101-005.remarq.com...
Adrian Greenwood
anti-icing system on many occasions. ABB manufacture an ice monitoring
system which looks at the IGV's and detects ice build up on them. This
system initiates an alarm so that an operator can go to the GT and visually
inspect the IGV's (viewing window installed). A decision is then made to use
anti-icing or not. Usually the first thing we saw was a frost build up,
which spreads across the blade. When the frost covered the blade the
anti-icing was used. This system greatly reduces the use of anti-icing but
does not get rid of its use all together.
I have heard of the system that you have and suggest you contact your OEM
before thinking of changing to another system.
The drop in efficiency is due to the hot air that is bled from the
compressor discharge which is not available for the combustor and power
turbine i.e. drop in mass flow.
Hope this helps
Adrian.
YGYang wrote in message <071bb362...@usw-ex0101-005.remarq.com>...
Steve Hunter
that if you have a trash screen or other element inside the gas turbine
inlet duct then localized icing may occur there which would not be detected
by inspecting the IGV's. If it was serious enough, a small "chunk" of ice
could break off and cause damage to the compressor blading.
If your climate has a large variation in humidity at low temperatures (i.e.
northern Canada), an alternative system uses humidity and temperature to
determine if icing is possible and only turns on the anti-icing if needed.
In your case, I would suggest that icing is not possible at +7 deg C and
70% humidity - perhaps you could investigate a variable humidity input
(i.e. turn icing on if -7 deg C and 70% RH at the low end and +7 deg C, 95%
RH at the high end and a linear interpolation between). This system is in
operation on some GE gas turbine (mostly Frame 6B's).
I don't think that the +7 deg C limit is necessarily too high - you have to
take into account the fact that air in the inlet system is operating below
atmospheric pressure (and therefore any water vapour freezes at greater
than 0 deg C) and the velocity of the air flowing past obstructions can
have a local effect.
An alternative (and more efficient) method of anti-icing for CCGT & Cogen
plants which I have seen in operation on a Siemens V64.3A in Germany is to
install a heating coil in the gas turbine inlet and pass warm condensate
(typically 25-35 deg C) through the coil as needed to raise the temperature
of the air entering the gas turbine inlet. A limitation of this system is
that, unless you have auxiliary boilers, you must use a conventional system
to protect the gas turbine during cold weather startup as the CCGT plant
will typically startup after the gas turbine.
I believe there are a number of inlet filter manufacturers who offer 3rd
party aftermarket anti-icing systems - perhaps you could try these
companies of your gas turbine manufacturer doesn't give you any help?
Hope this helps
Steve Hunter
sabri...@gmail.com
Thank you Steve for your valuable feedback.
Could you please share with us your experience if the anit-icing is provided with air pulse cleaning to clean the pre-filter in case of ice formation (frost accumulation).
I mean is anti-icing system is enough without air pulsing system?
I agree with you that anti-icing should be start under precised control system with ambient air set point +4 C. GE provides anti-icing with two ways , first is hot air from turbine the second is electrical coil or another heating medium.
Scott Baumann
Have you resolved your icing issues as of yet? If this persists, we have developed a solution which utilizes exhaust gas heat in order to eliminate both tradtional ammonia vaporization systems (electric elements / hot gas recirc fans) as well as providing unlimited heated CT inlet air for both anti-icing and performance heating. Thank you
Scott