Gaseous emissions, control combustion

A widely used system for the control of organic gaseous emissions is oxidation of the combustible components to water and carbon dioxide. 

A process is described [224] in which an exothermic reaction takes place in a semi-batch reactor at elevated temperatures and under pressure. The solid and liquid raw materials are both toxic and flammable. Spontaneous ignition is possible when the reaction mass is exposed to air. Therefore, the system must be totally enclosed and confined in order to contain safely any emissions arising from the loss of reactor control, and to prevent secondary combustion reactions upon discharge of the materials to the atmosphere. Further, procedures and equipment are necessary for the safe collection and disposal of solid, liquid, and gaseous emission products. 

Afterburning is the most common term used to describe the combustion process employed to control gaseous emissions. The term afterburner is appropriate only to describe a thermal oxidizer used to control gases coming from a process where combustion was not complete. Incinerators are used to combust solid, liquid, and gaseous materials when used in this handbook, the term incinerator will refer to combustion of waste streams. Other terms used to describe combustion equipment include oxidizer, reactor, chemical reactor, combustor, etc. 

The fluidized bed reactor is a relatively new approach to the design of high heat release combustors. The primary functions of the air-fluidized inert bed material are to promote dispersion of incoming solid fuel particles, heat them rapidly to ignition temperature, and to promote sufficient residence time for their complete combustion within the reactor. Secondary functions include the uniform heating of excess air, the generation of favorable conditions for residue removal, and the ability to reduce gaseous emissions by control of temperature or by use as a gas-solids reactor simultaneously with thermal conversion. 

B.G. Jenkins, The effect of the fuel Selection on Kiln Operation and Emissions". In Combustion and Gaseous Control III", Inst, of Energy, 19, ISBN 090 259 7558. 

Early days of pollution control aimed principally at smoke abatement, that is, particulate emission control. For installations using solid fuels, it was often necessary to change to more expensive gaseous or liquid fuels, which later were less expensive. As better designs evolved to reduce particulates, users benefited because more complete combustion was achieved. 

It is more efficient, and usually essential if emission controls are to be met, to remove the SO2 formed from the gaseous products of combustion. 

New units can be ordered having dry, low NO burners that can reduce NO emissions below 25 ppm on gaseous fuels in many cases, without back-end flue-gas cleanup or front-end controls, such as steam or water injection which can reduce efficiency. Similar in concept to low NO burners used in boilers, dry low NO gas turbine burners aim to reduce peak combustion temperatures through staged combustion and/or improved fuel—air mixing. 

Applicability/Limitations Most t qjes of solid, liquid, and gaseous organic waste or a mixture of these wastes can be treated with this technology. Explosive wastes and wastes with high inorganic salt content and/or heavy metals require special evaluation. This operation can create high particulate emissions which require post-combustion control. 

Tn the past considerable attention has been directed towards the well publicized formation, analysis, and control of gaseous air pollutant emissions such as NO., CO, unbumed HC, and SO, . In contrast relatively little effort has been devoted to the study of nongaseous emissions, especially particulate emissions from internal combustion engines. This is partly caused by the fact that, on a weight basis, the amoimt of relatively large particulate matter formed in and emitted from automobiles... 

Understanding the processes that control atmospheric aerosol concentrations and representing these processes in chemical transport models rests in large part on the accuracy of emissions inventories of aerosols and gaseous precursors. The most widely applied approach to developing such inventories is characterization of emissions per unit of activity (called emission factors ) combined with characterization of the intensity and geographic distribution of these activities. This approach is well developed for some gas-phase species. Emission of SO2 from fossil fuel combustion provides an example. Most sulfur in... 

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