Tuning Your Fuel-Gas Delivery System

Saudi Aramco has focused more attention in recent years on fuel-gas conditioning for land-based industrial and aeroderivative combustion gas turbines (CGTs). Hydrocarbon dew points and entrained solids are two important fuel quality issues that frequently trouble CGT operators, partly because they cannot be guaranteed by the fuel suppliers and they are rarely monitored by the operators. This paper addresses these issues and offers some practical advice to optimize the design and operation of fuel gas delivery systems. Saudi Aramco has been testing an automated on-line dew point monitor capable of detecting both hydrocarbon and aqueous dew points in natural gas. Dew point monitoring, conducted at three locations on the fuel gas grid, revealed wide variations in the hydrocarbon and aqueous dew points due to a variety of conditions. Gas production and pipeline operations accounted for the most dramatic variations in dew points, but exposure of pipelines to the weather can also be important. Measurement of pipeline solids for the purpose of sizing and placement of particle filters have also been explored. Pipeline scraping, gas velocities, length of pipeline span, pipeline junctions, and control valves are all considerations for solid control strategies. The optimized design and operation of a CGT fuel system is highly dependent on dew point control and efficient removal of entrained pipeline solids. Practical experience in monitoring hydrocarbon and aqueous dew points, pipeline solids control, and optimizing fuel conditioning equipment are considered.