(Digital Presentation) Offshore Gas Turbines

Abstract

Offshore gas turbines are the main power drivers for offshore production facilities; they are used for gas lifting, pumping, power generation and compression due to their high power to weight ratio and size. It is therefore imperative to minimize their downtime to prevent production losses. The need to examine the how deposits formed on the blade surface limits the life and performance of the engine cannot be overemphasized.In this study the Rolls Royce RB211, an aero derivative engine commonly used offshore was selected and its performance data obtained from PYTHIA engine simulation and diagnostic software. These values were used to calculate the rate of mass deposition of potassium sulphate (K2SO4), a potential corrosive salt.In order to determine rate of mass deposition, contaminant levels for a clean gas and good filter were obtained from General Electric’s fuel specification while a higher contaminant level was assumed.It was found that at high temperature corrosive salt tend to deposits on the blade surface when concentration of contaminants was calculated for both low and high impurity levels. It was also observed that the rate of mass deposition was high at the first stage of the turbine section where high gas temperature and pressure is usually experienced and drops as hot gas travel along the turbine and leaves as exhaust gas at very low temperature and pressure.In order to minimize the risk of damage to turbine hot section components like nozzle guide vanes and blades, fuel purity specifications and an appropriate inlet air filtration system must be used. This keeps contaminants in the combusted gas below allowable contaminant levels as recommended by original equipment manufacturers.