Correct Answer - Option 2 : Draught to be produced
Explanation:
The height of the chimney in a steam plant is governed by Draught to be produced.
Draught
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It is a small pressure difference causing the flow of flue gas and air through the boilers.
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It is necessary for efficient combustion and to release the gases at sufficient height to avoid local pollution.
Calculation of chimney height
In a steam power plant chimney height is calculated by,
\(h=H(\rho_a-\rho_f)=353[\frac{1}{T_a}-(\frac{m+1}{m})\frac{1}{T_f}]\)mm of H2O
where h = draught in mm of water, H = chimney height in metre, Ta = temperature of outside air in Kelvin, Tf = flue gas temperature in kelvin, m = mass of air supplied per kg of fuel in kg.
If Hf is the height of the hot gas column in metre
\(H_f=[(\frac{m}{m+1})\frac{T_f}{T_a})-1]\) metre
