FAI Spring 2023 Process Safety News.ai

Heat of Combustion Testing Patrick Wojcik, Manager, Flammability Testing and Consulting Services, Fauske & Associates Introduction 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.

Figure 1: Heat of Combustion Apparatus

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? Heat of combustion testing provides valuable information about the energy content of a substance which is critical for a wide range of applications, including fuel development, reaction analysis, and classification of aerosol products (see the following page for details). Heat of combustion testing can also be used to determine the number of calories per gram of food and it is also currently one of the chemical property requirements for the development of commercial and military turbine fuels (ASTM D240).

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