Which device in a gas power plant is used to recover heat from the exhaust gases of the turbine?

Option 2 : Regenerator 

Gas power plant:

A gas-fired power plant or natural gas power plant is a thermal power station which burns natural gas such as methane to generate electricity.

Components of a gas power plant:

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The main parts of a gas power plant are:

1.) Compressor: 

• The compressor used in the plant is generally of rotatory type.
• The air at atmospheric pressure is drawn by the compressor via the filter which removes the dust from the air. 
• The rotatory blades of the compressor push the air between stationary blades to raise its pressure. Thus air at high pressure is available at the output of the compressor.

2.) Regenerator:

• A regenerator is a device which recovers heat from the exhaust gases of the turbine. 
• The exhaust is passed through the regenerator before wasting to the atmosphere. 
• The compressed air from the compressor passes through the tubes on its way to the combustion chamber. In this way, compressed air is heated by the hot exhaust gases.

3.) Combustion chamber:

• The air at high pressure from the compressor is led to the combustion chamber via the regenerator. 
• In the combustion chamber, heat is added to the air by burning oil. 
• The oil is injected through the burner into the chamber at high pressure to ensure atomization of oil and its thorough mixing with air. 
• The result is that the chamber attains a very high temperature (about 3000 F). The combustion gases are suitably cooled to 1300F to 1500F and then delivered to the gas turbine.

4.) Governor:

• The governor is used to control engines or turbines driving alternators, dc generators, pumps, or compressors. 
• It automatically maintains the rotary speed of an engine or other prime mover within reasonably close limits regardless of the load.