With the growing global demand for more efficient and sustainable energy sources, determination of the heat of combustion of substances is expected to continue to play a critical role in the development of new fuels and the optimization of existing fuels.
The heat of combustion (also referred to as the calorific value, fuel value, or energy value) is the amount of energy released as heat when a material undergoes complete combustion in a pure oxygen environment at constant volume. In this article, we will explore the concept of heat of combustion testing and its significance in various industries
What is Heat of Combustion Testing?
Heat of combustion testing is carried out using an isoperibol oxygen bomb calorimeter, which consists of a high-pressure rated vessel ("bomb") that is immersed in a water bath inside of a calorimeter (Figure 1). Prior to immersing the vessel into the water bath, a measured amount of solid or liquid sample that is being tested is transferred into a sample cup which in turn is placed inside of the bomb. Afterwards, the bomb is pressurized with a measured quantity of pure oxygen, and then the entire vessel is sealed and immersed in the water bath inside of the calorimeter. After the temperature of the water bath stabilizes, a fuse wire is used to ignite the sample, causing it to combust in the oxygen. The heat generated by the combustion reaction inside the bomb is transferred to the water in the surrounding bath, and the resulting temperature rise is measured. This temperature rise is then used to calculate the heat of combustion of the sample.
Why is Heat of Combustion Testing Important?
Various industries use heat of combustion testing for different objectives and applications. Some examples include:
Fuel Development & Optimization:
Heat of combustion testing is used considerably in the development of new fuels and in optimization of existing fuels. Scientists and engineers can use this method to determine the energy value as well as quantify the amount of waste heat that is generated during combustion of different substances, such as metal fuels, biofuels, and renewable fuels. These data are then used to optimize fuel composition and production processes, as well as minimize emissions, to create fuels that are more cost-effective, efficient, and environmentally friendly.
Reaction Analysis:
Determination of material energy content is essential for research and development of new chemistries, as it allows researchers to assess the heats of formation of raw materials prior to a synthesizing into the final product to understand the total energy consumption/generation of the reaction. Before scaling up a reaction, it is important to fully understand the reactivity and energetic potential of the materials involved. This way the reaction can be optimized to achieve high yields and avoid any unwanted reactions, some of which can be extremely violent.
Aerosol Classification:
In conjunction with ignition distance and enclosed space ignition tests using methods outlined in the United Nations Chemical Classification Manual, the results of heat of combustion tests can be used to characterize an aerosol product as non-flammable, flammable, or extremely flammable (see Figure 2). The classification of aerosols is essential in determining proper packaging and shipping groups for transportation purposes to avoid any accidents.
Conclusion
Heat of combustion testing is a vital method for evaluating the energy value of a material and is critical in a wide variety of applications. An accurate and precise analytical measurement of a material’s energy content is crucial in
research, development, optimization, and safety.
References:
- ASTM D240. (2017). Standard Test Method for Heat of Combustion of Liquid Hydrocarbon Fuels by Bomb Calorimeter. Philadelphia, PA: American Society for Testing and Materials.
- United Nations. (2019). Recommendations of the Transport of Dangerous Goods: Manual of Tests and Criteria. New York: United Nations.