Plume Dispersion: A New Flare Combustion and Plume Rise Model
Date
2012-12-14
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Abstract
Air pollution from industrial sources is a continuing concern, especially near residential areas, where public health can be affected. Dispersion of plumes released from stacks depends on wind speed, plume emission rate, stack height, and other meteorological and stack variables. Plume rise is an important aspect of plume dispersion because it increases the apparent release height, which leads to lower ground-level concentrations. Plume rise models are therefore important components of air dispersion models. Plume rise linked with flare combustion has received only minimal attention in the scientific literature to date, despite its importance.
This thesis develops a numerical model of plume rise with flare combustion based on material, heat, mass, and momentum balances. The basis of the model was proposed by Scire et al. (2000)as Plume Rise Model Enhancements (PRIME) for plume rise and building downwash. Later on, De Visscher (2009) extended the PRIME model to account for flare combustion by keeping track of the amount of oxygen mixed into the plume. The current study is an extension of the work of
De Visscher (2009) to account for the rate of reaction. The proposed model considers the
reaction kinetics to produce more realistic and accurate results. Moreover, emissivity, which plays an important role in the heat conservation equations but which was only parameterized in the original model, is calculated explicitly to increase the accuracy of the model. In the first step, a set of heat, material, and momentum conservation equations are proposed
related to the wind speed and the stack parameters. The basic model is obtained by solving these equations simultaneously assuming instantaneous combustion. Then the kinetics of combustion to CO and CO2 were considered as a model extension. The emissivity calculation was also enhanced to obtain more accurate results in the improved model. Finally, the air dispersion model CALPUFF was run according to the proposed flare model and a simpler and less realistic
flare model by Beychok (2005) to compare results of the models. This new flare method is simple enough to be embedded into the air dispersion modeling software (such as CALPUFF). Currently, regulatory models use variants of Beychok’s (2005) approach, but these are not realistic. More sophisticated models exist (e.g. based on CFD), but these are too complex to be used in combination with air dispersion models. Thus, this study
offers a simple and reliable flare model to be used in air dispersion models.
Description
Keywords
Environmental Sciences, Engineering--Chemical, Engineering--Environmental
Citation
Rahnama, K. (2012). Plume Dispersion: A New Flare Combustion and Plume Rise Model (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/27371