Combustion, gaseous fuels atomizers

Spent Acid or Burning. Burners for spent acid or hydrogen sulfide are generally similar to those used for elemental sulfur. There are, however, a few critical differences. Special types of nozzles are required both for H2S, a gaseous fuel, and for the corrosive and viscous spent acids. In a few cases, spent acids maybe so viscous that only a spinning cup can satisfactorily atomize them. Because combustion of H2S is highly exothermic, carehil design is necessary to avoid excessive temperatures. 

Combustion. The primary reaction carried out in the gas turbine combustion chamber is oxidation of a fuel to release its heat content at constant pressure. Atomized fuel mixed with enough air to form a close-to-stoichiometric mixture is continuously fed into a primary zone. There its heat of formation is released at flame temperatures deterruined by the pressure. The heat content of the fuel is therefore a primary measure of the attainable efficiency of the overall system in terms of fuel consumed per unit of work output. Table 6 fists the net heat content of a number of typical gas turbine fuels. Net rather than gross heat content is a more significant measure because heat of vaporization of the water formed in combustion cannot be recovered in aircraft exhaust. The most desirable gas turbine fuels for use in aircraft, after hydrogen, are hydrocarbons. Fuels that are liquid at normal atmospheric pressure and temperature are the most practical and widely used aircraft fuels kerosene, with a distillation range from 150 to 300 °C, is the best compromise to combine maximum mass —heat content with other desirable properties. For ground turbines, a wide variety of gaseous and heavy fuels are acceptable. 

If a fuel is in the liquid state, such as fuel oil, most of it must be vaporized to the gaseous state before combustion occurs. This vaporization can be accomplished by supplying heat from an outside source, but usually the liquid fuel is first atomized and then the finely divided fuel particles are sprayed into a hot combustion chamber to accomplish the gasification. 

To be detected by AAS, the analyte must be presented to the optical beam of the instrument as free atoms. The process of converting analyte ions/molecules, dissolved in a suitable solvent, to gaseous atoms is accomplished by the nebuliser flame assembly. The nebuhser (from the Latin nebula meaning cloud) creates an aerosol (a fine mist) of the hquid sample which is mixed with an oxidant gas and a fuel gas (to support the flame combustion). The mixture is ignited above the burner assembly. The liquid droplets are desolvated, the resulting microcrystals are melted and vaporised and finally the gaseous products are thermally dissociated to produce free atoms. The combustion speed of most flames is such that the conversion from liquid droplet to free atoms must be accomplished within a few milhseconds. 

GasoUne is a mixture of hydrocarbons (primarily alkanes) that contain 5 to 12 carbon atoms per molecule. Diesel fuel is a similar mixture, except the molecules contain 12 to 16 carbon atoms. The hot CO2 and water vapor generated during combustion in an internal combustion engine have a much greater volume than the air and fuel mixture. It is this sudden increase in gaseous volume and pressure that pushes the pistons and delivers power to the crankshaft. 

Matter in a state where atoms collide but are not in a fixed arrangement and assume the shape or their container is in the gaseous state (Meyer, 2005). Gases are the simplest state of matter and are therefore the easiest fuel to discuss. However, gases are elemental to the understanding of how combustion occurs in all states of matter and will be discussed first. Fuels can typically only enter the combustion reaction when they are in a gaseous state liquids and solids must turn into a gas before combustion is possible. 

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