Part 1 chap 1 4 English version

Pagina 1

CHAPTER 1 - Stoichiometry: theory of relative quantities of reactants and products in chemical reac tions - Atomic weight (mass): relative mass of an atom weighted on a scale which assigns a value of 12 to the mass of the 12C isotope of carbon. The molecular weight of a chemical species is the sum of the atomic weights of all its atoms. - Mole: the amount of a chemical species having a mass expressed in grams equal to its molecular weight. One mole of any chemical species contains a constant number, 6.022x1023 (Avogadro number), of molecules. - Fuel: any chemical substances that, under appropriate conditions, can react with an oxidant (comburent), usually O2, releasing a large amount of energy. - Combustion: reaction with oxygen of all combustible species in a fuel. Complete combustion is achieved when carbon is totally converted into carbon anhydride (CO2), hydrogen into water, sulfur into sulfurous anhydride (SO2 ) and nitrogen into molec ular nitrogen. Incomplete combustion occurs when unconverted fuel or CO are present in products - Theoretical oxygen: stoichiometric amount of oxygen required to achieve complete fuel combustion - Stoichiometric air to fuel ratio: stoichiometric air mass to fuel mass ratio - Air to fuel ratio: effective air mass to fuel mass ratio (other quantities are: air-fuel equivalence ratio lambda=a/a st= effective air/ theoretical air; fuel-air equivalenc e ratio phi=1/lambda. If lambda >1 we have lean combustion mixtures, which may allow compl ete combustion) Starting from elemental composition of the fuel provided as weight percentages of hydrogen (H), carbon (C), sulfur (S) and oxygen (O) the stoichiometric air to fuel ratio can be obtained as follows: Mass balances of reacting system are an application of the mass conservation law.…