Emission Measurement Technology

Flue gas treatment (FGT) is more effective in reducing NO, emissions than are combustion controls, although at higher cost. FGT is also useful where combustion controls are not applicable. Pollution prevention measures, such as using a high-pressure process in nitric acid plants, is more cost-effective in controlling NO, emissions. FGT technologies have been primarily developed and are most widely used in Japan. The techniques can be classified as selective catalytic reduction, selective noncatalytic reduction, and adsorption. 

Emission measurements are required for many purposes. They can be used as the basis for emission and air quality studies, as well as for process control and specific technologies to reduce emissions. The reliability of the measured values is constantly improving with developments in monitoring techniques. 

The technology for controlling emissions from heavy-duty vehicles has, until recently, focussed on in-cylinder measures such as direct injection (DI) and high-pressure injection (HPI, >150 MPa). However, at current and future emission levels SCR has become the NOx emission-control technology of choice, whilst DPFs will effectively become mandatory at the Euro VI level (Table 4). 

Emission coefficients are estimates of emissions per unit of activity level. These coefficients are generally estimated using actual measurements of emissions and information about activity levels from a subset of representative sources. The emission measurements used as an input to these coefficients are subject to considerable uncertainty, being based on measurements at ten sources or, at most, at a few hundred sources. Usually, no direct estimates of associated variability or uncertainty, are available. Depending upon the level of detail in the model being used to make the emission estimates, emission coefficients may be assumed constant over time or across regions, or new combustion and other technologies may be assumed to be available. 

Within the scope of a research project [3], the prEN and ISO/DIS draft type test standards, especially the methods for determination of the efficiency and the measuring of the emissions, were compared with a continuous burning appliance by the Center of Appropriate Technology, Langenbruck. The efficiencies evaluated by both methods vary only marginal at all tested bum rates. The differences are within the accuracy range of the said test methods. The same is true for emission measuring methods. The measurements show that the test method with direct determination (calorimeter room) and the indirect determination (flue gas) of the efficiency can be considered as equivalent (Fig. I) The same can be concluded for the measurements of emissions in the flue gas and the dilution tunnel (Fig. 2). Provided that the test procedures are identical for both standards, equivalent results for efficiencies and emissions are obtained. 

The third example of field emission from Si-based nanowires is from the aligned SiC nanowires. The field emission measurements [68] were carried out in a vacuum chamber at a pressure of 5 x 10 Torr at room temperature. An oriented SiC nanowire array, which was used as the cathode, was stuck to a stainless steel substrate by silver paste with the bottom end of the nanowires facing upward. A copper plate with a diameter of 1 cm, mounted on a precision linear feedthrough, was used as the anode. Field emission current densities of 10 pA cm were observed at applied fields of 0.7-1.5 V pm and current densities of 10 mA cm were realized at applied fields as low as 2.5-3.5 V pm , as shown in Figure 10.35. These results represent one of the lowest fields ever reported for any field-emitting materials at technologically useful current densities. We attributed this emission... 

When experimental data are sought, the EPA regulates testing methods. A list of approved methods and their descriptions is available at the Technology Transfer Network Emission Measurement Center (http //www.epa.gov/ttn/emc/tmethods.html). 

With respect to environmental chemistry, controls over the emission of organic compounds will undoubtedly be strengthened in the future. For example, municipal incinerators without provisions for the effective measurement of all hazardous organic compounds will soon be strictly forbidden everywhere. It seems likely that a large fraction of the moneys previously spent for defense purposes will be redirected toward improvements in continuous measurement technology. Sensors will be required to compete in this respect with such fast separation methods as capillary electrophoresis or flash chromatography, which permit the separation of most compounds within only a few minutes. 

The US EPA has an Emission Measurement Center EPS [24.4]. From the EPS it is possible to obtain supporting software for test method technology. 

M. R. Guerin and J. L. Epler, Determining emissions measurements needs for an emerging industry—advanced fossil fuels utilization. Presented at the First Conference on Determining Fugitive Emissions Measurements Needs, Hartford, Connecticut, May 17-19, 1976, EPA Technology Series, EPA-600/2-76-246. 

ERA, Technology Transfer Network, Emissions Measurement Center, Method 15 determination of hydrogen sulfide, carbonyl sulfide and carbon disulfide emissions from stationary sources, 2011. . 

PTR-MS has also been used to investigate the emissions from intensive pig production in Denmark [150-152], which is an obvious and often cited cause of foul air in populated rural areas. The highest emissions detected by PTR-MS were found to be associated with hydrogen sulfide and acetic acid. Also in Denmark, PTR-MS was used to quantify and study the temporal variation of gas emissions from a model pig house (scale 1 12.5 of a commercial pig house) under varying ventilation rates [153]. The aim of such model studies is to aid in the development of emission abatement technology. In order to do that, it is first necessary to identify the different factors that can affect the emission of VOCs. Concentrations of two inorganic volatiles (NH3 and H2S) and fourteen VOCs were measured coming from a slurry pit and at the outlet of the model pig house. The fourteen VOCs and their protonated mJz values were methanethiol miz 49), acetone (miz 59), trimethylamine miz 60), acetic acid (m/z 61), dimethyl sulfide m z 63), C4-carbonyls (e.g. 2-butanone) miz... 

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