Numerical Simulation of Dispersion of Emissions from Tema Oil Renery in Ghana

Abstract

The petrochemical industry is a major contributor of industrial air pollutants

which are known to have dire consequences on human health and

the environment, neccesitating research into their dispersion and transport.

The objective of the study, therefore, is to simulate the dispersion and transport

of pollutants emitted during the processing of crude oil by the Tema

Oil Renery in the Greater Accra region of Ghana using the California

Pu (CALPUFF) modeling system. This thesis couples the Weather Research

and forecasting Model (WRF) with the non-steady state California

Pu(CALPUFF) modelling system to simulate the dispersion and transport

of emissions from the renery in a coastal urban/industrial area in

Ghana. The mass balance approah was employed to estimate the renery

emission rates which were used as input for the dispersion model. Emission

rates of ve species were estimated - SO2, NO2, PM2:5, CO2 and VOCs.

The transport and dispersion of SO2, NO2 and PM2:5 were modelled over

the period between 2008 - 2013 and their impact on 38 identied receptors

investigated. Simulation results showed that the radius of impact of the

emissions is approximately 10 km. As a result of the prevailing predominant

south-westerly winds in the study area, concentrations of emissions at

receptors located upwind of the emission source were found to be higher as

the winds carried the pollutant clouds in their direction. Conversely, south

and south-western receptors, relative to the renery, on the other hand,

were minimally impacted. Concentrations of SO2 and NO2 at 2 out of the

38 receptors exceeded the regulatory limit of the World Health Organisation

and Ghana's Environmental Protection Agency. It can be concluded,

therefore, that SO2 and NO2 emissions from the renery do not pose any

danger to the larger population and the general environment nearby. PM2:5

levels at 36 receptors however exceeded the WHO guideline value leading

to the conclusion that the renery operations could pose some dangers

to the environment regarding PM2:5. The dispersion model results were

compared with measurements at the same location in order to validate

the model. Similarly, observations from two meteorological stations were

compared with results from the meteorological model. The performance

evaluation, with the aid of statistical measures revealed that the models'

performance were acceptable.