Evaluation of Methanol and Light Fuel Oil Blends Firing at a 50 MW Gas Turbine

Emissions reduction requirements lead to modification of the firing system to control NOx emission reduction, and/or the post combustion treatment of the flue gas to remove NOx, SO2 & particulates. It has also leads to installation of new renewable energy production systems. All of these measures are very expensive both in installation and operation costs, while utilities are looking for low cost options with a minimum impact on unit performance and reliability. Firing of methanol and its blends with other liquid fuels, in comparison with other renewable sources, is one of the main alternatives for meeting this target. Methanol is a clean burning fuel that is made from non-petroleum energy sources such as natural gas, coal, biomass and carbon dioxide. Using CO2 for methanol production leads to reducing of greenhouse gas emissions so that methanol can actually be called as enviro fuel. The blending of methanol with light fuel oil is one of the quickest and cheapest means for both replacing costly petroleum energy consumed in the existing power generation fleet and reducing emissions that lead to air pollution such as nitric oxides, carbon monoxide, air toxics and PM. Hence, methanol is a good candidate as an alternative fuel for power generation, since it is liquid and has several physical and combustion properties similar to fuel oil. For this reason, this study is aimed to evaluate gas turbine performance and emissions characteristics for different blends of methanol and light fuel oil. The results obtained from simulation of different light fuel blends were compared to those of actual burning. In this study we experimented with methanol fractions (from 0 to 100 % by heat) at different GT loads and found that the methanol and light fuel oil blends enabled us to significantly reduce NOx emissions with increasing of the methanol fraction. SO2 emissions were also reduced according to the methanol heat fraction. The final blend ratio optimization should be based upon environmental requirements and fuel price. CO emissions are slightly higher than the required level. Based on performed tests, the main reason for CO formation is high excess air, especially at partial loads and as a result of low combustion temperature (this conclusion is right for any fuel and its blends). In order to reduce CO emissions, proper air /fuel control is necessary (IGV, IBH etc). This conclusion is very important for conceptual design of gas turbines in general and particularly for GT conversion to methanol firing. Firing of methanol and its blends had no impact on GT performance and provides safe operation. The computer simulations provide support for these experimental findings and conclusions. The results of the performed tests analysis indicate that methanol firing is a potentially promising low cost technology for emissions’ reduction and may be implemented in existing and new gas turbines.