MODELLING H2S DISPERSION FROM MENENGAI GEOTHERMAL POWERPLANT


Nyairo Beatrice
Geothermal Development Company
P.O Box 100746-00101, Nairobi-Kenya
bnyairo@gdc.co.ke


ABSTRACT

The release of hydrogen sulphide gas is an important environmental issue during the operation of geothermal power plant. This gas negatively affects the air quality hence detrimental effects to biodiversity. The Hydrogen sulphide gas in geothermal areas constitutes a serious problem to the environment, the human health, and the geothermal equipment. In the atmosphere, hydrogen sulphide is a pollutant and toxic. When dissolved in water, it is corrosive to metal-based materials such as iron, steel, and brass. For these reasons, hydrogen sulphide must be reduced to extremely low levels as a mitigation measure to reduce the adverse effects. In this study, a dispersion modeling of H2S emission was used to determine the concentrations of the pollutant in the surrounding. The technique is carried out using atmospheric dispersion modeling system (AERMOD) which is a steady-state Gaussian model to predict ground level concentrations in the vicinity of the power plant. To achieve this goal, hourly meteorological data were captured and input to the Aermet processor. Since H2S concentration is heavily influenced by weather conditions, statistical analysis is used to determine a correlation with the weather parameters and the quantitative effects of precipitation on H2S concentration. The analysis provided a base for predicting H2S concentration for different weather conditions and thereby the likelihood of conditions that may exceed the regulatory requirement for H2S concentration and the possible effect of increased emissions. The prepared background and predictive model when combined show that although operations at Menengai Geothermal Project emit H2S gas, the concentrations are below the WHO set guidelines of 150ug/m3 and therefore have a less impact on air quality. The findings are beneficial as part of regulations for air quality standards to reduce global warming and environmental degradation, the introduction.

Key words: Geothermal, Environment, Hydrogen sulphide


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