Hi...
which one is correct:
Gas turbines can either turnes the generator or send hot exhaust gases to heat recovery
or
Gas turbines either can turnes the generator or send hot exhaust gases to heat recovery

The first one.

"Can" needs to be positioned to go with both ideas.

It's like this: Can (either x or y)

Not this:

Either can x or y

The latter is slightly ambiguous.

(If you're interested, these are called correlative conjunctions.