Why is the procedure for the determination of the volatile matter content in the proximate analysis different for biomass and coals?

Proximate analysis is a commonly used technique to determine the composition of a solid fuel like coal or biomass. It gives the percentages of moisture, volatile matter, fixed carbon, and ash content in the fuel. Knowing the composition of a fuel is important for predicting its combustion behavior, efficiency, and emissions.

Volatile matter refers to the substance that is released from a solid fuel when heated, excluding moisture. These are the gaseous components of the fuel, including hydrocarbons, sulfur, and nitrogen compounds, which contribute to combustion and can affect the fuel efficiency and emissions.

Biomass is an organic material derived from plants and animals, generally used as a renewable energy source. It consists of carbohydrates, lignin, lipids, proteins, and various minerals. Coals, on the other hand, are fossilized plants formed over millions of years under high pressure and temperature. They are primarily composed of carbon, along with hydrogen, sulfur, oxygen, and nitrogen.

Biomass and coals have different characteristics that impact their volatile matter content and behavior during combustion. Biomass typically has a higher volatile matter content, lower carbon content, and higher oxygen content than coal. Additionally, the structure and composition of biomass and coal compounds are different, leading to different release patterns for volatile matter during heating.

The procedure for determining volatile matter content in proximate analysis involves heating the sample in a furnace under specific conditions (temperature, time, and atmosphere) and measuring the weight loss. Given the differences in characteristics between biomass and coal, the methods for determining volatile matter content in both materials need to vary. For biomass, the main differences in the procedure include: 1. Lower heating temperature: Biomass is generally heated at a temperature of around 950 °C, while coal is heated at a temperature of around 850 °C. Lower temperatures are used for biomass because the higher oxygen content makes it susceptible to oxidative reactions at higher temperatures, leading to inaccuracies in volatile matter determination. 2. Different heating time: Biomass typically requires a longer heating time (about 7 minutes) compared to coal (around 3 minutes) due to the slower release of volatile matter from its complex and varied compounds. 3. Use of a nitrogen atmosphere: A nitrogen atmosphere is used during the heating process for biomass to reduce the possibility of oxidative reactions and errors in measurement. The differences in the procedures for volatile matter determination in proximate analysis for biomass and coal exist because of their unique characteristics and composition. Adapting these procedures ensures accurate measurement and helps predict the combustion behavior, efficiency, and emissions of both types of fuel.