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A fundamental understanding of the acid gas (H2S and CO2) chemistry is key to efficiently implement the desulphurisation process and even the production of clean fuels such as hydrogen or syngas. In this work, we developed a new kinetic model for the pyrolysis and oxidation of hydrogen sulphide by merging two previously reported models with the goal of covering a wider range of conditions and including the effect of carbon dioxide. The resulting model, which consists of 75 species and 514 reactions, was used to conduct rate of production and sensitivity analysis in plug flow reactor simulations, and the results were used to determine the most prominent reactions in which hydrogen sulphide, molecular hydrogen, and sulphur monoxide are involved. The resulting list of important reactions was screened and the kinetics of three of them, i.e., SO2 + S2 → S2O + SO, S2O + S2 → S3 + SO, and SO + SH → S2 + OH, was found to warrant further investigation. With the goal of improving the accurancy of our new kinetic model, we carried out a robust quantum chemistry and Rice–Ramsperger–Kassel–Marcus master equation study to obtain, for the first time, the forward and reverse rate constants for those three reactions at temperatures and pressures of interest for combustion and atmospheric chemistry. This work is the first step of a kinetic study that is aimed at improving the understanding of the chemistry of the pyrolysis and oxidation of H2S, highlighting the importance of sulphur–sulphur interactions and providing a fundamental basis for future kinetic models of H2S not only in the field of combustion, but also in atmospheric chemistry. [ABSTRACT FROM AUTHOR]

Light naphtha (LN) is gaining interest in internal combustion (IC) engine applications due to its low refining cost and higher heating values compared to commercial gasoline. To properly describe the chemical and physical behavior of the LN fuel under IC engine conditions, a systematic procedure to develop unified physical and chemical surrogates is described. The reduced component models to describe the chemical characteristics of LN are combined with the effective thermal conductivity/effective diffusivity (ETC/ED) model to represent the accurate evaporation behavior. Three surrogate fuels consisting of three to five components are presented and their performance in heating and evaporation of a single LN droplet is compared against the conventional primary reference fuel (PRF65) surrogate which is based on chemical aspects only. Unlike the previous approaches, the new surrogates also target matching the hydrogen-to-carbon ratio and research octane number in order to accurately describe the chemical behavior of the fuel. Subsequently, the performance of the surrogates in describing spray characteristics is tested by computational simulations compared with experimental measurements. The simulations were carried out using CONVERGE CFD package. The ETC/ED model was implemented into CONVERGE using user-defined functions. The predicted spray penetration length for the developed surrogates shows good agreement with the experimental data. At engine-like conditions, the ETC/ED model predicts higher vapor mass than the infinite thermal conductivity/infinite diffusivity model, hence showing the expected trend by incorporating the realistic droplet heating process. [ABSTRACT FROM AUTHOR]

Modeling the combustion behavior of real fuels is a challenging task: Significant analytical efforts are required to characterize the fuel composition, and comprehensive kinetic models are necessary to reproduce the behavior of the different fuel components. Both these aspects become increasingly critical for fuels having a high molecular weight, wherein both the characterization of the single components and the kinetics involved in their oxidation become extremely complex. Indeed, kinetic models for large hydrocarbons can include thousands of species and tens of thousands of reactions. For these reasons, only a limited number of representative components are generally included in the simulations and these large kinetic mechanisms are reduced to simulate the behavior of real fuels in practical conditions. We propose a novel approach to the simulation of the combustion of high molecular weight fuels, wherein the fuel surrogate is defined in terms of pseudospecies including the functional groups contained in the actual fuel. These pseudocomponents, representing linear, branched, aromatic, saturated, and unsaturated structures, can undergo the typical reactions responsible for the low-temperature ignition of hydrocarbon as well as the interactions occurring in fuel blends. The basics of this concept will be presented, through application to linear and branched alkanes, and the potential of this approach is assessed by means of comparisons with experimental data and detailed kinetic simulations. The potential of this methodology for reducing computational expense in computational fluid dynamics simulations is also highlighted. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 257-276, 2012 [ABSTRACT FROM AUTHOR]