Troubleshooting of Repetitive Liquid Fuel Nozzles Clogging Due to Liquid Fuel Coking in Dual Fuel Gas Turbine

Abstract Gas turbines are one of the most widely used technology for both power generation and mechanical drive applications. Their availability is a critical requirement for any plant uninterrupted operations. The subject case study details the root cause analysis done on repetitive clogging of liquid fuel nozzles due to liquid fuel coking on a dual fuel heavy duty gas turbine, that had an impact on the overall plant operation. The site is configured with two Frame 5/1PA single shaft Gas Turbine with standard combustion system, driving generator for power production. The two Gas Turbine Generators (GTGs) are completely identical and running on same liquid fuel and gas fuel. These gas turbines can only be started with liquid fuel and then change over to gas fuel as required. On one of the GTGs the issue of liquid fuel nozzles clogging due to liquid fuel coking happened twice in a span of six months. Few of the indications are Increase in exhaust temperature spreads and "failed to lite" during startup. Comparatively the other similar unit faced no such issue during its operations. Liquid fuel coking occurs if there is stagnant liquid fuel at high temperature over time at the Nozzles. For a duel fuel gas turbine, while it is running on gas fuel, constant air purge is provided in order to remove any residual liquid from the liquid fuel nozzles so it will not coke while running on gas fuel.