GE 7FA Gas Turbines equipped with Dry Low NOx (DLN) combustion systems are often deployed in 100% pipeline natural gas applications. Although natural gas is available, some industrial and petrochemical sites prefer to look for ways to utilize process gases produced on-site to reduce plant operating costs. Some of these facilities produce hydrogen-containing process gases (sometimes known as off-gas) as a by-product of the main plant chemical processes. Some users desire to reduce natural gas consumption by blending some percentage of the process off-gas with their main natural gas supply.
In response to a request from the Dow Chemical Company, GE developed a fuel blending system allowing a hydrogen / natural gas fuel blend to be burned in a 7FA Gas Turbine with the DLN2.6 combustion system. Until its development, the fuel specification for this combustion system did not allow for hydrogen to be included in the fuel composition. The first fuel blending systems are now operating at the Dow Plaquemine facility.
The Dow Chemical Company approached GE about the possibility of operating a set of gas turbines at one of their petrochemical plants on a blend of process gas and natural gas. The first step in this process was a series of feasibility tests in GE's combustion test facility in Greenville, SC, to determine the capability and limitations of the current DLN2.6 combustion system to burn a fuel blend of natural gas and hydrogen. These tests were performed at full pressure, temperature and flow, simulating field conditions.
Parameters monitored during the tests included NOx and CO emissions, as well as combustion dynamics. These tests demonstrated that the DLN2.6 combustion system is capable of operating with up to 5% H2 blended with natural gas.
Based on these feasibility tests, the engineering team designed an off-base system, capable of blending the process gas with the natural gas. It is composed of instruments for measuring fuel flow and gas composition as well as valves for controlling flow.
You can read the rest of this article in the Jan/Feb edition of the magazine.