What is ultimate analysis and what does it reveal about fuel?

• A. Carbon, hydrogen, sulfur, nitrogen, and oxygen.
• B. Only carbon and hydrogen.
• C. Moisture, ash, volatile matter.
• D. Carbon, hydrogen, and nitrogen only.

Answer: (A)

Ultimate analysis measures what the fuel is made of in terms of its elemental content on a mass basis. It tells you how much carbon, hydrogen, sulfur, nitrogen, and oxygen are present in the fuel. This five-element picture is what you need to predict how the fuel will burn: carbon and hydrogen largely determine the energy you can get since they are the main fuel-forming elements; sulfur indicates potential sulfur oxide emissions; nitrogen indicates potential NOx formation; and the amount of oxygen already in the fuel affects how much extra air is needed for complete combustion. Oxygen is often determined by difference or directly measured because some fuels contain oxygen as part of their structure, and this influences flame temperature and air requirements.

The other descriptions don’t fit because one omits key elements (carbon and hydrogen alone ignore sulfur, nitrogen, and oxygen), or mixes in moisture, ash, and volatile matter (those come from proximate analysis, not ultimate). So the complete ultimate analysis focuses on carbon, hydrogen, sulfur, nitrogen, and oxygen.