Previous Year Question
In the context of proposals to the use of Hydrogen-enriched CNG (H-CNG) as fuel for buses in public transport, consider the following statements:
The main advantage of the use of H-CNG is the elimination of carbon monoxide emissions.
H-CNG as fuel reduces carbon dioxide and hydrocarbon emissions.
Hydrogen up to one-fifth by volume can be blended with CNG as fuel for buses.
H-CNG makes the fuel less expensive than CNG.
Which of the statements given above is/are correct?
1 only
2 and 3 only
4 only
1, 2, 3 and 4
Correct Answer: B
Detailed Solution
H-CNG is a mixture of hydrogen and Compressed Natural Gas. Methane is the principal component of CNG.
Hydrogen has a high flame speed and a wide flammability range. Mixing it with CNG can make fuel combustion more complete and rapid.
Statement 1 is incorrect: H-CNG can reduce carbon monoxide emissions, but it does not eliminate them completely.
Carbon monoxide is produced mainly due to the incomplete combustion of fuel. The addition of hydrogen improves combustion and, therefore, reduces its emission.
The use of an H-CNG mixture containing about 18% hydrogen has shown a significant reduction in carbon monoxide emissions, but the emissions do not become zero.
Statement 2 is correct: Hydrogen does not contain carbon. Therefore, replacing a portion of CNG with hydrogen reduces the overall carbon intensity of the fuel.
Better and more complete combustion can reduce emissions of carbon dioxide and unburnt hydrocarbons.
Statement 3 is correct: H-CNG can be prepared by blending approximately 18% hydrogen by volume with CNG. This quantity is within the limit of one-fifth by volume, that is, 20%.
The proportion of hydrogen in the mixture is determined by considering engine design, safety, combustion characteristics and emission standards.
Statement 4 is incorrect: The production, storage and transportation of hydrogen and its blending with CNG require additional infrastructure and energy.
Therefore, it is not correct that H-CNG is necessarily less expensive than CNG. Its cost depends on the source and production method of hydrogen.
An advantage of H-CNG is the possibility of using a comparatively cleaner fuel mixture with limited modifications to existing CNG engines and distribution infrastructure.