Understanding Methane's Higher Heating Value (HHV)
The Higher Heating Value (HHV) represents the total amount of heat released when a fuel is burned completely, assuming the water produced is condensed back into liquid. We need to find the HHV of methane ($\text{CH}_4$) in terms of grams of carbon (gC) per megajoule (MJ) of energy released.
Calculation Steps
- Identify Given Information:
- Combustion of 1 mol of $\text{CH}_4$ releases 890 kJ of energy.
- Combustion of 1 mol of $\text{CH}_4$ produces 1 mol of $\text{CO}_2$.
- 1 mol of $\text{CO}_2$ contains 12 g of carbon (C).
- Relate Energy to Carbon Content:
The combustion of 1 mol of $\text{CH}_4$ releases 890 kJ and corresponds to 12 g of carbon.
- Convert Energy Units:
Convert the energy from kilojoules (kJ) to megajoules (MJ), knowing that 1 MJ = 1000 kJ.
Energy = $890 \text{ kJ} \times \frac{1 \text{ MJ}}{1000 \text{ kJ}} = 0.890 \text{ MJ}$
- Calculate HHV in gC/MJ:
Divide the mass of carbon associated with the combustion by the energy released in MJ.
HHV = $\frac{\text{Mass of Carbon}}{\text{Energy Released}} = \frac{12 \text{ gC}}{0.890 \text{ MJ}}$
HHV $\approx 13.483 \text{ gC/MJ}$
- Round the Result:
Rounding the result to one decimal place gives 13.5 gC/MJ.
Final HHV Value
The higher heating value (HHV) of methane is approximately 13.5 gC/MJ.
Important Questions from Energy and Environment - Teaching
- Which of the following fuels has the highest HHV carbon intensity ?
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- In terms of the calorific value, identify the correct sequence :
- At a given location the wind speeds are predominantly in the range $6$ to $6.4 \text{ m/s}$. This location’s wind power class will be termed as :
