Combustion
Combustion is a chemical reaction between a fuel and an oxidizing agent, typically producing heat and light. It is characterized by the rapid release of energy in the form of heat and often accompanied by the production of flames. This exothermic reaction is essential for many industrial processes and is a key component of various energy production methods.
6 Key excerpts on "Combustion"
eBook - ePub- Warren C. Strahle, William A. Sirignano, William A. Sirignano(Authors)
- 2020(Publication Date)
- Routledge(Publisher)
...1 INTRODUCTION AND REVIEW 1.1. GENERAL INTRODUCTION The generation of heat on earth has come largely from a process called Combustion, and this will continue well into the next century. The process involves a chemical transformation between a substance or substances called fuels and other chemicals called oxidizers. No alteration of the nuclei of the entering substances is involved, but bonds involving the electrons of the molecules and atoms take place. This bonding causes heat to be liberated, or, in some cases, heat is required to form the bonds. The case of heat liberation is the most interesting, since it is this heat energy that can be usefully exploited. In addition to fuel and oxidizer, often an ignition source is needed. For example, one of the earliest forms of Combustion, the forest fire, uses wood as the fuel, the air as the oxidizer and the ignition source can be a spark (lightning). 1 Combustion has a wide variety of uses. It is used for power generation or creation of thrust in engines of all types. Combustion is used as a heat source for chemical processing, general heating and drying operations. It is useful in waste incineration, melting operations and welding. Combustion is involved in explosions for both useful and hostile purposes. The use of Combustion has harmful effects, however. Pollutants and greenhouse gases are produced as well as waste heat and unwanted explosion and fires. The science and engineering of Combustion is the subject of this book. Combustion is a complex subject to master, requiring knowledge of many sub-disclipines of physics, chemistry and physical chemistry. Examples are fluid mechanics, quantum mechanics, statistical mechanics, kinetic theory, chemical kinetics, electromagnetic radiation, and heat and mass transfer...
eBook - ePub- James G. Speight(Author)
- 2010(Publication Date)
- Gulf Professional Publishing(Publisher)
...Chapter 10. Combustion of Hydrocarbons Contents 1. Introduction 355 2. Combustion chemistry 358 3. Slow Combustion 362 4. Rapid Combustion 364 5. Complete and incomplete Combustion 366 6. Spontaneous Combustion 367 7. Process parameters 369 7.1. Air–fuelratio 373 7.2. Equivalence ratio 374 8. Combustion of hydrocarbon fuels 375 8.1. Combustion of gaseous hydrocarbon fuels 376 8.2. Combustion of liquid hydrocarbon fuels 379 8.3. Combustion of non-hydrocarbon fuels 380 8.3.1. Fuel oil 380 8.3.2. Coal 385 8.4. Formation of particulate matter 389 8.5. Char and coke 391 8.6. Soot 391 References 393 1. Introduction Combustion (burning) is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species (Glassman, 1996). The release of heat can result in the production of light, usually in the form of a flame. Fuels of interest often include organic compounds (especially hydrocarbons) in the gas, liquid, or solid phase. For the most part, Combustion involves a mixture of hot gases and is the result of a chemical reaction, primarily between oxygen and a hydrocarbon (or a hydrocarbon fuel). In addition to other products, the Combustion reaction produces carbon dioxide (CO 2), steam (H 2 O), light, and heat. Combustion is the burning of any substance, in gaseous, liquid, or solid form. In its broad definition, Combustion includes fast exothermic chemical reactions, generally in the gas phase but not excluding the reaction of solid carbon with a gaseous oxidant. Flames represent Combustion reactions thatcan propagate through space at subsonic velocity and are accompanied by the emission of light. The flame is the result of complex interactions ofchemical and physical processes whose quantitative description must draw on a wide range of disciplines, such as chemistry, thermodynamics, fluid dynamics, and molecular physics...
eBook - ePubIndustrial and Process Furnaces
Principles, Design and Operation
- Barrie Jenkins, Peter Mullinger(Authors)
- 2013(Publication Date)
- Butterworth-Heinemann(Publisher)
...The fuel can be a gas (e.g. hydrogen, natural gas), a liquid (e.g. oil, alcohol, sulphur), or a solid (e.g. coal, wood, peat). The rate at which these Combustion reactions occur can vary from a very slow decay to an instantaneous explosion. Both the chemical kinetics and physical diffusion processes involved control this rate. The objective of the Combustion engineer and plant operator is to obtain a steady heat release at the rate required to suit the process objectives. 2.1 Simple Combustion Chemistry Most industrial fuels are hydrocarbons, so called because their primary elemental constituents are carbon and hydrogen. These are oxidized to release heat during Combustion. The chemistry of this oxidation process involves very complex chain reactions. However, for most engineering design purposes we can reasonably simplify the chemistry to four basic reactions. The following equations define the Simple Chemically Reacting System (SCRS). 2.1.1 The Complete Oxidation of Carbon Providing there is sufficient oxygen present in the mixture, the above reaction describes the overall result of the oxidation of carbon. However this reaction rarely occurs in practical Combustion systems but is the result of a chain of reactions involving carbon monoxide as an intermediate product, as discussed later in this section. 2.1.2 The Complete Oxidation of Hydrogen The difference in the physical states of the water produced as a result of the oxidation of hydrogen is the reason for the complexity of the net and gross calorific values for hydrocarbon fuels. The gross heat release is that which is released when the hydrogen is oxidized and the water condensed, whilst the net calorific value is the heat which is released while the water remains as steam...
eBook - ePub- V. Babu(Author)
- 2019(Publication Date)
- CRC Press(Publisher)
...CHAPTER 13 Combustion THERMODYNAMICS In our discussion of power producing cycles such as Rankine, Brayton and so on, it was assumed that a certain amount of heat was supplied to the cycle. The details of how this heat was generated was immaterial. It is well known that this heat is generated by the Combustion of a fuel (solid, liquid or gas) usually with atmospheric air. In this chapter, the thermodynamic aspects of this Combustion process are studied in detail. 13.1 Combustion stoichiometry Combustion is an oxidation reaction that is accompanied by heat release (exothermic). For instance, H 2 + 1 2 O 2 → H 2 O is a Combustion reaction in which 1 kmol of H 2 combines with 1/2 kmol of O 2 to form 1 kmol of water vapor. The required oxygen may be provided as a pure oxygen stream or, as is commonly done, from atmospheric air. In the thermodynamic context, it will be assumed that Combustion takes place. The question of whether Combustion can take place is the subject matter of Combustion texts. For the present purpose, it will be assumed that the air supplied is dry (unless otherwise stated) and comprises 21 percent O 2 and 79 percent N 2. Therefore, every kmol of O 2 that is supplied is accompanied by 0.79÷0.21 = 3.76 kmoles of N 2. Thus, if air instead of pure O 2 is supplied in the above reaction, we have H 2 + 1 2 (O 2 + 3.76 N 2) → H 2 O + 1.88 N 2 It is assumed throughout in this chapter that N 2 is inert and does not participate in the chemical reaction. In reality, this is not true; as the temperature of the products increases, N 2 oxidizes to form oxides, which are of course, pollutants owing to their harmful effects on the environment and humans. Consider the complete Combustion of liquid n-octane (C 8 H 18) with air. Here, complete Combustion of a hydrocarbon fuel with air implies that the Combustion products are fully oxidized, i.e., CO 2 and H 2 O are the only products and there is no excess oxygen in the products...
- John J. Lentini(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
...C HAPTER 2 The chemistry and physics of Combustion I’m sorry. If you don’t know H 2 O, you will not be rendering opinion testimony in my courtroom. —Hon. J. Michael Ryan Washington, DC Courts LEARNING OBJECTIVES After reviewing this chapter, the reader should be able to: Demonstrate knowledge of fire chemistry and physics beyond the high school level as required by NFPA 1033 including: • Knowing the definitions of atoms, molecules, elements, compounds and mixtures • Knowing how to set up and balance a simple Combustion equation • Understanding the states of matter, and the behavior of solids, liquids, and gases when exposed to fire • Appreciating the relationship between fire and energy • Understanding the concepts of energy, power, and flux, and knowing the units used in the measurement of each of these properties 2.1 BASIC CHEMISTRY Fire is defined as a rapid oxidation process with the evolution of light and heat in varying intensities. To understand fire, it is first necessary to understand the nature of fuels and the processes that allow fuels to burn. Without a basic knowledge of chemical principles, the fire investigator will be at a loss to understand the artifacts left behind. All matter is composed of atoms. Atoms, with rare exceptions (called rare gases), are bonded together in molecules or crystals containing two or more atoms. Those atoms can be all the same, in which case the substance is called an element. If the atoms are not all the same, the substance is called a compound. Pure elements or pure compounds are relatively rare, except in a laboratory. Most elements and compounds are found in mixtures. A mixture contains more than one type of substance, but the components of a mixture are not chemically bound to each other. Air, for example, is a mixture of gases. The closest thing to a pure element that a fire investigator is likely to find is the copper used to manufacture electrical conductors or pipes for water or gas...
eBook - ePub- David Chadderton(Author)
- 2002(Publication Date)
- Routledge(Publisher)
...4 Combustion of a fuel INTRODUCTION Analysis of the Combustion of a fuel requires a knowledge of its chemical constituents and the excess air that is to be supplied. Sufficient information is provided to allow the analysis of a wide variety of fuels without recourse to further references. The chemicals in fuels, and their symbols, are listed. The equations of Combustion in air are given for each chemical element and compound. The lists are not intended to be exhaustive, but they do cover a very large number of normal cases. The user may add further fuels once their chemical compositions are known. The products of Combustion are given for each fuel. The stoichiometric and actual air supply is calculated. The flue gas analysis for the fuel is converted from units of mass into percentages by volume to allow comparison with on-site measurements during commissioning and maintenance. The flue gas composition from site measurements can be entered. The program then calculates the amount of excess air that was supplied. The gross and net calorific values of the fuel are assessed. The quantity of data that is to be entered is small, and all calculations and output data are generated automatically. The program acts as an on-screen tuition package...
