Stack-plume observations

Much can be learnt from the direct observation of atmospheric dispersion phenomena. Many observations are of the dispersion of a plume of visible tracer (e.g. smoke or water vapour) from a chimney or stack , such that it is quite the convention to describe dispersion in this context. Accordingly, stack-plume observation is used here to help identify the main processes of atmospheric dispersion pertinent to the distribution and delivery of CWAs. In the following, these processes are described under four headings ... 

Many researchers have studied plume rise over the years. The most common plume rise formulas are those developed by Gary A. Briggs, which have been extensively validated with stack plume observations (USEPA, 2005). A formula for buoyancy-dominated plumes is shown in Equation 9.1. Plume rise formulas can be used on plumes with temperatures greater than the ambient air temperature. The Briggs plume rise formula is as follows ... 

Ultraviolet absorption by sulfur dioxide may also be usefully applied in the field for direct plume observations. In a novel technique developed for the observation of the colorless discharge of sulfur dioxide and water vapor from a natural gas cleaning plant vent stack, the use of silica optics and a special UV sensitive film allowed the clear photographic observation of plume behavior from the ultraviolet absorption of the sulfur dioxide component [30]. 

Recently, the application of short term bio-assays to a variety of emission and ambient particulate samples has demonstrated that other compounds than PAH, most likely PAH-derivatives, can be responsable for a major part of the observed biological activity of the extracts. These results have forced us to widen our interest to the field of particulate polycyclic organic matter (POM), which besides hetero-atomic PAH (polycyclic aromatic compounds, PAC, containing nitrogen or sulfur) may also contain oxidized, nitrated, or sulfonated derivatives of PAH, formed in exhausts, emission stacks, plumes or during transport through the atmosphere. 

When a boiler is fired for the first time (or started again after repairs or inspection), vapor and water may be observed as a white plume in stack discharge or as condensate on the boiler fire sides and services. Generally, this condition is temporary and it will disappear after the unit reaches operating temperature. This condensation should not be confused with the stack plume that occurs when the boiler is operating during extremely cold weather. 

Plume rise observations based on single-stack operation were regressed into the above expression and empirically fitted to the following expression, which incorporates atmospheric stability classes into the coefficients ... 

Marathon has not observed a visible plume with use of NH3 injection. The majority of the injected NH3 is either reacted or absorbed on the catalyst fines. Stack test data measured <3 ppm NH3 slip with 90 ppm NH3 injection at the inlet. 

The emphasis in the present work is on leachates derived from fly ash disposal, but it must not be forgotten that fine ash particles may escape from power plants. The transport and dispersion of particulate emissions from tall stacks has been actively researched over the last 20-30 years. A review by Carras (1995) records that plumes have been observed to remain as coherent units up to distances of at least 1800 km and thus deposit pollution far from source. However, maximum particulate surface loadings are likely to be found adjacent to old power plants with limited fine-particle fly ash entrapment. Evans et al. (1980) estimated that in a period of 23 years the cumulative stack ash load at a distance of 1.7 km from an 83 MW... 

By observation, we found that the average height of the emissions plume from the main stack of En-Menatof was about 25 m for an average wind speed of 4.25 m/s, so the actual maximum height used for calculations of concentrations on ground is that deducted from the Bosanquet formula (H = 124.33 m). 

In general a very light plume or no plume at all is observed from the stack of an S03/air sulphonation plant. 

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