| Abstract: |
This thesis aims to study the dispersion of air pollutants from a stack into atmosphere.The primary purpose of this study is to predict the plume behavior for gases emitting from the stack. In turn. the recommended minimum downwind distance, height and width for the residential areas around an industrial stack. The obtained results are represented graphically in line, and contour charts. The present mathematical models are namely K-8 model and Large Eddy Simulation Model. The present models are used for a variety of physical processes, and pollutants and applied on single stack and multi stacks The present models can be applied at different locations and times (for Large Eddy Simulation only) in all flat or simple terrain (Rural and Urban). It will be useful in feasibility and planning studies of the new factories, especially in the new Egyptian cities.From these results, a number of conclusions can be summarized:1- The present investigation may be considered as a detailed parametric study for single/multiple stack(s) cases. To our knowledge there is a clear shortage in the literature of such parametric studies. Most of the publications cover specified (special) cases with fixed operating and atmospheric conditions.2- The present study considers greatly the plume/plume interference. It needs many contributions to cover all its aspects.3- Numerical techniques that were used in the present study proved to be very effective and efficient in studying the behavior of a single/multiple plume(s) emitting from a single/multiple stack(s).4- K-Ii model that was used in the present investigation is capable of correctly predicting the non dimensional maximum distance (XmllxlH) traveled by the plume. However, it fails to correctly predict the maximum height (ZmaxlH) reached by the plume.5- Due to its nature (Two-dimensional), K-Ii model results are restricted to the cases of a point source. This situation doesn’t represent completely the actual (real) stack case. Thus, the results of K- 8 model should be taken with caution especially for the maximum plume height.6- The diffusion model was developed and added to the traditional K- & model which can be a good practicing (training) to understand and development of the more complex models (e.g. Large eddy simulation, Reynolds stress models, etc-----).7- Large eddy simulation gives the details (real-time views) of the development of the plume during its course.8- The non dimensional maximum plume distance (XmaxlH) increases with the increase of the wind speed until it reaches a certain value then the plume will dissipates at a shorter distance this is obtained from the two mathematical models.9- For a certain wind speed the non dimensional maximum plume distance (Xmax/H) increases with increasing each oCthe gas exit speed and the stack diameter.I ().. The non dimensional maximum plume height (ZmaxlH) decreases with the increase of the wind speed.11- The non dimensional maximum plume heighl (ZmaxlH) increases with the increase of the gas exit speed.12- The non dimensional maximum plume width (Y max/H) increases with the increase of the wind speed until reached a certain value then the plume will dissipate at a shorter distance. This conclusion based on large eddy sinlUlation.13- Changing the stack height has a small effect on each of the non dimensional maximum plume distance (Xmax/H) and the non dimensional maximum plume width (Y max/H) but it has an observed effect on the non dimensional maximum plume height (ZmaxlH), which decrease with the increase of stack height.14- Temperature of exhaust gases exit from the stack relative to ambient temperature (T gaIT’ ambient) decreases with the distance downwind the stack until reaches the ambient temperature.15- For large eddy simulation the time that plume needs to dissipate decreases with increase in wind speed.16- The non dimensional maximum plume distance (Xmax/H) decreases with increase in ambient temperature.17- Non dimensional Concentration of exhaust-gases constituents (CO, CO2, S02, NOx) exiting from the stack (C/Crnax) is decreases (decays) with the distance downwind the stack.t 8- The distance traveled by the solid particles (from 1 to 100 micron) decreases as the particle size increases19- The light particle (from 1 to -9 micro) may travel to distances that exceed 24 Km downwind the emitting stack, which may stay in the atmosphere for ever (i.e. suspended particles).20- Comparing the results with the published experimental and numerical methods of Khan and Abbasi explained that the large eddy simulation is the nearest from them and give accepted results. While K- e model results can’t be accepted as it is far from the published data.5.2 Future WorkBased on the previous discussions in chapter 4 and the conclusions listed above, thefollowing points may be suggested for future work:( I) Experimental measurements to validate the results of the present study. (2) Studying plume - building interactions.(3) Investigation chemical reactions for the exhaust gas components with the atmosphere.(4) Considering the implementation of more sophisticated environmental conditions (rain, snow, .... ).
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