APPLICATION OF MICROBIAL METABOLISM STOICHIOMETRY IN MODELLING BIO-FOULING ASSESSMENT IN GAS TURBINE LIQUID FUELS

摘要

High reliability, availability and emission compliance are few of the quality requirements and demands in the gas turbine industry. Gas turbine engines are characterized by competitive performance and efficiencies, but often limited by operational and component inefficiencies, one of which is brought about by compromised fuels. These fuels carry unwanted materials such as rust, dust, contaminated air or water droplets harboring microorganisms, of which hydrocarbon-degrading bacteria are of primary concern. The microorganisms exert one or more degradatory effects, particularly, the disappearance of certain hydrocarbon fractions and changes to physical and chemical properties of the fuels. These often result in the accumulation of sludge and initiation of other bioprocesses, such as corrosion with huge cost implications. Previous studies have identified the microorganisms associated with fouling and factors promoting their growth. However, their effects in gas turbine fuels and fuel systems have not necessarily been quantified. Thus, a thorough understanding of the mechanism of bio-fouling in gas turbines is necessary, especially with recent focus on alternative fuels and blends. This work presents an application of fundamental concepts of thermodynamics and bio-energetics in demonstrating and evaluating bio-fouling in gas turbine fuels. Here, the microbial cell is considered as a black box, in which microorganisms utilize hydrocarbon substrates for energy, biosynthesis and cell maintenance. Preliminary analysis on surrogate jet fuel and two other model fuels (BX-F and BX-M) indicate a 15%, 21% and 23% degradation loss of the bio-available fractions respectively and thermodynamically, the biofuel range of fuels resulted in more cell yield than the conventional fuel. This model is considered of prime importance in engineering design decision and analysis of microbial fuel degradation.