33931 - Chemistry of Combustion Processes M

Learning outcomes

The course provides knowledge of the thermodynamic and kinetic aspects of the chemical reactions that take place in internal combustion machines and energy production devices.

Course contents

The course offers an in-depth study of the fundamental concepts of thermodynamics and chemical kinetics, with respect to the chemistry knowledge acquired in the three-year degree, in order to understand the reaction patterns related to the combustion mechanisms of the main fuels used in internal combustion engines, mechanisms which are then examined and discussed in detail. The formation mechanisms of the main pollutants and the methods used today to minimize their release into the environment are also illustrated, taking into account the fuel used and the conditions in which combustion takes place. Finally, we will move on to a discussion of the chemistry of the atmosphere in order to understand the effect of pollutants on the environment.

1. Review of basic chemistry. Review of the electronic configurations of the main elements of the Periodic Table and their properties. Review of the main characteristics of the different types of chemical bonds. Absorption spectra of atoms and molecules.

2. Chemical thermodynamics. Review of thermochemistry: standard enthalpies of reaction, formation and combustion. Review of the second law of thermodynamics and Gibbs free energy. Chemical equilibrium from a thermodynamic point of view; expressions of the equilibrium constant for ideal and non-ideal systems. Heterogeneous reactions. Review of the effect of temperature and pressure on the chemical equilibrium in the gas phase. E.m.f. of a battery and derivation of the Nernst equation by thermodynamics.

3. Chemical kinetics. Recall on the fundamentals of chemical kinetics. Simple and complex reaction mechanisms. Molecularity of simple reactions and reaction order; the case of monomolecular reactions. Kinetics of some types of complex reactions: parallel, convergent, consecutive reactions. The approximation of the steady state. Reversible reactions. Kinetics of chain and branched chain reactions. The partial equilibrium hypothesis. Effect of temperature on the reaction rate: the theory of molecular collisions and the Arrhenius equation; the activated complex and the steric factor. Other expressions k(T). General properties of catalysts; homogeneous catalysis and heterogeneous catalysis. Heterogeneous catalysis (gas-solid): adsorption kinetics with (or without) dissociation of the reactant molecules.

4. Combustion. Generalities on combustion reactions: fuels and oxidizers; the self-ignition phenomenon. References to upper and lower calorific value and to the adiabatic flame temperature. Branched chain reactions and explosive conditions. Explosion limits and combustion mechanisms of hydrogen, carbon monoxide, methane, hydrocarbons, etc. The formation of nitrogen oxides in combustion: the thermal and the prompt mechanism. The effect of the presence of nitrogen in fuels. Notes on the formation of oxides and other sulfur compounds. The particulate matter: its structure and danger; outline of formation mechanisms.

5. Effects of combustion on the environment. The structure of the atmosphere. The dry adiabatic gradient in the troposphere and the trend of pressure and density with altitude. The stability and conditions of thermal inversion. Ground-level pollution: photochemical smog. The formation of ozone, hydrogen peroxide, PAN and nitric acid. Acid rains and their effects on the environment. Catalytic systems for the reduction of pollutants: TWC 'catalytic mufflers' and NSR catalytic systems; SCR devices in diesel engines. Particulate filters and their regeneration. Gas sensors: the 'lambda probe'. Systems for the reduction of particulate matter in diesel engine exhaust gases. The greenhouse effect and planetary warming: carbon dioxide and the other gases responsible for the greenhouse effect. Characteristics of fuels, with particular reference to those from renewable sources: energy and biomass fuels. Methanol and ethanol, biodiesel, hydrogen: advantages, disadvantages and prospects. Production methods, methods of use and issues related to hydrogen storage.

6. Chemistry of the stratosphere: the ozone layer. Absorption of UV radiation by oxygen and ozone. Mechanisms of formation and disappearance of the latter in the stratosphere and related thermal effects. Catalytic processes in ozone destruction: the effect of CFCs and other pollutants. The seasonal formation of the ozone hole over Antarctica.

 

A video-presentation of the teaching is available through the Links to further information, at the bottom of the page.

 

Readings/Bibliography

Recommended texts (for consultation):

I. Glassman – Combustion, Academic Press, III Ed., 1996.

S.R. Turns – An introduction to combustion, Mc Graw Hill, II Ed., 2000

C. Baird, M. Cann – Environmental Chemistry, W.H. Freeman & Co., 3rd Ed., 2004

R.A. Michelin, A. Munari – Fondamenti di Chimica, III Ed., CEDAM, 2016

Teaching methods

The course is based on lectures, supported by the projection of PowerPoint presentations.

Guided exercises will be carried out on the various topics of the program, similar in type and difficulty to those proposed during the exam.

Assessment methods

The verification of learning includes an oral exam on the topics covered in the classroom.

Teaching tools

The lectures in the classroom will be supported by the presentation of PowerPoint slides which can be downloaded in PDF format (Virtual) before the start of each lesson.

Links to further information

https://youtu.be/m6jHLLaLmJY

Office hours

See the website of Michelina Soccio