Gaseous emissions organic compounds

Emission abatement methods covered are suitable for the emission control of volatile organic compounds (VOCs). The VOCs include organic compounds existing in the gaseous phase in air at 293.15 K. However, or ganic compounds, which are not regarded as VOCs, can be treated by the methods covered in this section. 

The removal of one or more components from a gas mixture by absorption is probably the most important and familiar operation in the control of gaseous pollutant emissions. Though most often used for the control of inorganic gases, absorption can also be used for recovery of organic compounds. Absorption in-... 

The technologies used in the control of gaseous organic compound emissions include destruction methods such as thermal and catalytic incineration and biological gas treatment and recovery methods such as adsorption, absorption, condensation, and membrane separation. The most common control methods are incineration, adsorption, and condensation, as they deal with a wide variety of emissions of organic compounds. The most common types of control equipment are thermal and fixed-bed catalytic incinerators with recuperative heat recovery, fixed-bed adsorbers, and surface condensers. The control efficiencies normally range between 90% and 99%. 

Metallic salts (or metallic compounds) after dissolution in appropriate solvents when introduced into a flame (for instance acetylene burning in oxygen at 3200°C), turns into its vapours that essentially contain mostly the atoms of the metal. Quite a few such gaseous metal atoms are usually raised to a particular high energy level that enables them to allow the emission of radiation characteristics features of the metal for example-the characteristic flame colourations of metals frequently encountered in simple organic compounds such as Na-yellow, Ca-brick-red Ba-apple-green. This forms the fundamental basis of initially called Flame Photometry, but more recently known as Flame Emission Spectroscopy (FES). 

Gaseous emissions from biomass or soil are determined directly in the field or in the laboratory on canister grab samples, and volatile organic compounds are analyzed using canister grab or cartridge samples by GC... 

Particulate carbon in the atmosphere exists predominantly in three forms elemental carbon (soot) with attached hydrocarbons organic compounds and carbonates. Carbonaceous urban fine particles are composed mainly of elemental and organic carbon. These particles can be emitted into the air directly in the particulate state or condense rapidly after Introduction into the atmosphere from an emission source (primary aerosol). Alternatively, they can be formed in the atmosphere by chemical reactions involving gaseous pollutant precursors (secondary aerosol). The rates of formation of secondary carbonaceous aerosol and the details of the formation mechanisms are not well understood. However, an even more fundamental controversy exists regarding... 

Flue-gas from boilers fired with liquid or solid fuels contains fly-ash and gaseous contaminants such as CO, NOx, SO2, or volatile organic compounds (VOCs). Emission regulations require their removal, which is achieved by a sequence of after-treatment processes. The after-treatment usually comprises a filter to remove solid particulates operated at approximately 150 °C, a wet scrubber for the removal of SO2 with an alkaline solution operated at approximately 50 °C, and finally a selective catalytic reduction (SCR) unit, which converts NOx to N2 with the help of NH3 at approximately 370 °C (Fig. 15.1) [4]. During this process, the flue gas is cooled down and then heated up again, which requires additional heat transfer equipment, with its inherent energy losses. 

The main pollutants in gaseous emissions concern volatile organic compounds (VOCs), greenhouse gases, NOx and SOx. We will only discuss the emissions which can potentially be treated by zeolites. 

Two different technologies seem to be the most promising alternatives to reduce gaseous PAH emissions catalytic PAH destruction [6, 7] and PAH adsorption on carbonaceous materials [8, 9]. Historically, carbonaceous materials have been used for the removal of vapor phase organic compounds from about 100 ppmv to 10,000 ppmv concentrations in industrial waste gas streams [10]. Recently, it has been shown that dioxins, furans and PAH, at ppbv or lower coneentrations, can be effectively removed from waste incinerator combustion gases by using carbon injection or carbon bed technology [11]. 

In many industrial areas, emissions of gaseous oxides of sulfur (SOx), especially sulfur dioxide (S02), also rival natural sulfur gas emissions from volcanoes, wetlands, and oceans. SOx are produced from the oxidation of sulfur in fuels, especially coals and residual oils, and are responsible in large part for acid rain (Section 4.6.3). In fuels, sulfur typically occurs either in organic compounds (organic S) or as pyrite (FeS2). SOx also are formed from the refining of the ores of the many metals that occur in the form of metal sulfides [e.g., copper (Cu), lead (Pb), and nickel (Ni)]. 

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