Combustion reactions of coal

KSSN PRAKASH

1. COMBUSTION REACTIONS OF COAL K.S.S.N.PRAKASH Sapid : 500058663

2. COMBUSTION REACTION A Combustion reaction is a major class of chemical reactions, commonly referred to as "burning". Combustion usually occurs when a hydrocarbon reacts with oxygen to produce carbon dioxide and water. hydrocarbon + oxygen → carbon dioxide + water Combustion is an exothermic reaction, so it releases heat, but sometimes the reaction proceeds so slowly that a temperature change is not noticeable.

3. Combustion reaction include the presence of oxygen as a reactant and carbon dioxide, water and heat as products. The source of oxygen in the fuel combustion is air. By volume there is 21% of oxygen present in air and by weight it is 23.2%. Although there is 79%(by volume) of nitrogen in air but it plays no role in combustion.

4. CHEMISTRY OF COMBUSTION All fuels contain combustible elements. The main combustible elements in coal are Carbon , Hydrogen and small amount of Sulphur. Petroleum's , gases and the volatile portions of coal contain hydrocarbons and some carbon monoxide. When these combustible elements combine chemically with oxygen present in air supplied for combustion, energy is liberated with in the boilers, cylinder of i.c. engine and the combustion chambers of gas turbines. To calculate the amount of air required for complete combustion of a fuel, its chemical analysis, atomic and molecular weights of its constituents must be known.

5. CHEMICAL REACTION BETWEEN O2 AND COMBUSTIBLE ELEMENTS OF COAL The chemical equation for the process of burning of carbon to carbon monoxide is 2C + O2 = 2CO Substituting the molecular weights of the substances in this equation, (2*12) + 32 = 2*28 1 + 4/3 = 7/3 1 kg of C needs 4/3 kg of O2 and produces 7/3 kg of CO2 The chemical reaction in case of burning of carbon to carbon dioxide is C + O2 = CO2 12 + 32 = 44 1 + 8/3 = 11/3 1kg of carbon needs 8/3 kg of O2 and produces 11/3 kg of CO2 The burning of Sulphur to Sulphur dioxide is represented by S + O2 = SO2 1 + 1 = 2 1kg of Sulphur requires 1kg of O2 and produces 2kg of SO2

6. The process of burning of Hydrogen to water or steam is represented by the equation, 2H2 + O2 = 2H2O 4 + 32 = 36 1 + 8 = 9 1kg of H2 requires 8 kg of O2 and produces 9kg of H2O The process of burning of Carbon monoxide to Carbon dioxide is represented by the equation, 2CO + O2 = 2CO2 56 + 32 = 88 1 + 4/7 = 11/7 1kg of CO needs 4/7 kg of O2 and produces 11/7 kg of CO2 The process of complete combustion of methane gas is represented by the following chemical equation, CH4 + 2O2 = CO2 + 2H20 16 + 64 = 44 + 36 1 + 4 = 11/4 + 9/4 1kg of CH4 requires 4kg of O2 and produces 11/4 kg of CO2 and 9/4 kg of H2O

7. References: Power plant engineering by Black and Veatch ( G. Scott Stallard and Todd S. Jonas) Power plant engineering by PC. Sharma 7 th Edition Anne Marie Helmenstine, Ph.D. ( Updated July 03, 2017) (https://www.thoughtco.com/combustion-reactions-604030)