Co-Generation Systems Exam Practice

FDNY G91 Supervision of Natural Gas Co-Generation Systems Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• Which of the following best describes a co-generation system?
• A system that produces only electricity from natural gas
• A system that produces only thermal energy
• A system that simultaneously produces electricity and useful heat
• A system that stores natural gas for later use

Rationale: Co-generation, also called CHP (Combined Heat and

Power), generates both electricity and thermal energy from a single fuel source to increase efficiency.

• What is the primary advantage of co-generation systems over

separate heat and power production? 1 / 4

• Lower initial capital costs
• Higher overall energy efficiency
• Lower maintenance requirements
• Easier regulatory compliance

Rationale: Co-generation captures and uses waste heat, achieving

efficiencies up to 80% versus 45-50% in separate production.

• Which fuel is most commonly used in co-generation systems?
• Diesel
• Coal
• Natural gas
• Biomass

Rationale: Natural gas is widely used due to its clean-burning

properties, availability, and compatibility with gas turbines and reciprocating engines.

• What is the typical operating efficiency of a natural gas co-generation

system?

A. 30-40%

B. 40-50%

C. 50-60%

D. 70-85%

Rationale: By using both electricity and heat output, co-generation

systems can reach total efficiencies of 70-85%. 2 / 4

• Which component is essential for heat recovery in a co-generation

system?

• Transformer
• Compressor
• Heat Recovery Steam Generator (HRSG)
• Gas regulator

Rationale: HRSG captures exhaust heat from the turbine or engine to

produce steam or hot water for heating or industrial processes.

• Which of the following is a safety concern specific to natural gas co-

generation systems?

• Overheating of coolant
• High voltage shock
• Gas leaks and combustion hazards
• Noise pollution

Rationale: Natural gas leaks can lead to fires or explosions;

monitoring and safety systems are critical.

• What is the role of a governor in a co-generation gas engine?
• Controls fuel temperature
• Monitors emissions
• Regulates engine speed under load changes
• Controls cooling water flow

Rationale: The governor maintains stable engine speed to ensure

consistent power output. 3 / 4

• In co-generation systems, what is “backpressure operation”?
• Operating with low fuel pressure
• Steam is extracted at a higher pressure than condenser pressure
• Exhaust gases flow backward into the engine
• Water flows opposite to heat direction

Rationale: Backpressure steam turbines extract steam at higher

pressures for process use, increasing thermal efficiency.

• Which device prevents overpressure in co-generation steam lines?
• Check valve
• Flow meter
• Safety relief valve
• Regulator

Rationale: Safety relief valves release steam when pressure exceeds

design limits to prevent equipment failure.

• Which of the following emissions is primarily monitored in

natural gas co-generation plants?

• Mercury
• Nitrogen oxides (NOx)
• Sulfur dioxide
• Lead

Rationale: Natural gas combustion produces low levels of NOx;

monitoring ensures compliance with environmental regulations.

• / 4