Which of these is an output of a ‘Furnace’?

Question

Examoogle · Accepted Answer

Flue gases

Explanation: A furnace in a thermal power plant is a combustion chamber where fuel is burnt to produce heat energy. The gaseous byproduct resulting from this combustion process, which consists of combustion products and excess air, is collectively termed as flue gases.

Working Principle: The furnace operates by injecting fuel and air (primary and secondary) into the combustion zone. The chemical reaction releases high-temperature heat, converting chemical energy into thermal energy. The residual gaseous mixture, known as flue gases, is then directed towards the superheater and air preheater before being exhausted through the chimney.

Key Formulas: $C + O_2 \rightarrow CO_2 + Heat$; $Q = \dot{m} C_p \Delta T$

Key Points: Flue gases carry a significant amount of heat energy, which is recovered in the boiler's economizer and air preheater.; Efficient combustion requires an optimal air-fuel ratio to minimize incomplete combustion products like $CO$.; Flue gases are cleaned by Electrostatic Precipitators (ESP) before exiting the stack.

Advantages: High energy conversion efficiency; Continuous heat supply for steam generation

Disadvantages: Generates harmful emissions requiring treatment; High thermal stress on furnace walls

Applications: Thermal Power Plants; Industrial Heating Processes; Metallurgical Furnaces

Additional Info: Air is an input, not an output, of the furnace.. Water vapor is a component of the flue gases resulting from hydrogen combustion, but 'Flue gases' is the collective technical term for the exhaust output.. Option D is incorrect because Air is an input parameter.

Answer: B is correct — Flue gases are the gaseous byproduct of the combustion process occurring within a furnace.

Exam Tip: Always distinguish between system inputs (Fuel, Air) and system outputs (Ash, Flue gases, Steam) in power cycle analysis.

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