Flammability limits of mixtures of several combustible gases in catalytically supported thermal combustion systems
Creators: name: Chen, Junjie
Publisher: name: figshare
Year: 2022
Subjects: subject: 90403 Chemical Engineering Design
subject: FOS: Chemical engineering
subject: 90499 Chemical Engineering not elsewhere classified
subject: 90402 Catalytic Process Engineering
subject: 91501 Computational Fluid Dynamics
subject: FOS: Other engineering and technologies
subject: 91502 Computational Heat Transfer
subject: 91505 Heat and Mass Transfer Operations

description: Reactions of oxygen with hydrogen, with carbon monoxide, and with hydrocarbons are most important from the standpoint of theory and, at the same time, are of great practical value. Hydrogen combustion proceeds by complicated branched-chain reactions involving the interaction of hydrogen and oxygen atoms with oxygen and hydrogen molecules, respectively, to produce hydroxyl radicals. The final reaction product is water, formed by the combination of hydroxyl with hydrogen molecules. Reactions that terminate the chain, such as recombination of atoms and fragments of molecules, and the adsorption of active particles on solid surfaces, also play an important part in the mechanism of hydrogen combustion. The knowledge of rate constants for these processes derived empirically makes possible a quantitative description of all combustion characteristics, such as explosion limits, delay of ignition, and burning velocity. Combustion of carbon monoxide is mainly restricted to mixtures containing hydrogen or hydrogen compounds. In this case the reaction mechanism differs from that of hydrogen combustion chiefly in that it involves a step of fast interaction between hydroxyl and carbon monoxide. Pure mixtures of carbon monoxide and oxygen (or air) can be ignited only with sparks of high energy or under high pressures and temperatures. The chemical mechanism of their combustion is not yet clear, probably because oxidation of carbon monoxide, a reaction that is part of the combustion of practically all natural fuels, usually occurs in the presence of hydrogen or hydrogen compounds. The mechanisms of combustion of hydrocarbons and of other organic compounds are known in general outline only. Many elementary steps of hydrocarbon combustion involving oxygen and hydrogen atoms, hydroxyl, and organic radicals are similar to those for hydrogen; however, the overall mechanism of hydrocarbon combustion is complicated by the diversity of molecules and radicals involved. Moreover, with oxidation, thermal decomposition, a breakdown of complex organic compounds without oxidation, also takes place. Two types of hydrocarbon combustion have been defined: slow combustion at temperatures below 500 degrees Celsius, including cool flames observed at certain pressures, and combustion at higher temperatures, accompanied by hot flames. Ignition in two stages is characteristic of higher hydrocarbons, in which a cool-flame stage yielding readily oxidizable products precedes that of the hot flame. Contributor: Junjie Chen, ORCID: 0000-0001-5055-4309, E-mail address: komcjj@gmail.com, Department of Energy and Power Engineering, School of Mechanical and Power Engineering, Henan Polytechnic University, 2000 Century Avenue, Jiaozuo, Henan, 454000, P.R. China