Current Affairs 8th Class

Category : 8th Class

        Combustion

Combustion, process of rapid oxidation or burning of a substance with simultaneous evolution of heat and, usually, light. In the case of common fuels, the process is one of chemical combination with atmospheric oxygen to produce as the principal products carbon dioxide, carbon monoxide, and water, together with products such as sulphur dioxide that may be generated by the minor constituents of the fuel. The term combustion, however, also embraces oxidation in the broad chemical sense, and the oxidizing agent may be nitric acid, certain perchlorates, or even chlorine or fluorine.

             Energy Release

Most combustion processes release energy, or heat, for the production of power, for use in industrial processes, and for domestic heating and lighting. Combustion is also a means of producing a desired oxidized product, as in the burning of sulphur to produce sulphur dioxide and ultimately sulphuric acid. In addition, it is a method for disposing of wastes.

The energy released by combustion causes a rise of temperature of the products of combustion. The temperature attained depends on the rate of release and dissipation of the energy and the quantity of combustion products.

            Fuel

Fuel, substance that reacts chemically with another to produce heat, or that produces heat by nuclear processes. The term fuel is generally limited to those substances that burn readily in air or oxygen, emitting large quantities of heat. Fuels are used for heating, for the production of steam for heating and power purposes, for powering internal-combustion engines, and for a direct source of power in jet and rocket propulsion.

           Solid Fuels

The common solid fuels, in order of heat potential, are coal, coke, wood, sugarcane bagasse, and peat. Combustion of these causes decomposition of the fuel and evolution of the volatile matter as a gas that may burn with a sooty flame. The solid carbonaceous residue burns at a rate determined by the diffusion of oxygen to the surface.

            Liquid and Gaseous Fuels

Common liquid fuels are fuel oils, gasoline, and naphthas derived from petroleum, and, to a lesser extent, coal tar, alcohol, and benzol obtained from coke manufacture.

Gaseous fuels such as natural gas, refinery gas, and manufactured gases such as producer gas are usually mixed with air before combustion to supply a maximum amount of oxygen to the fuel.