Many experts believe burning hydrogen with natural gas can reduce carbon emissions without negatively impacting operational efficiency and performance. Hydrogen co-firing in a gas turbine ought to lower the carbon footprint of existing thermal power generation or co-generation plants by injecting hydrogen into the existing natural gas grid. At the moment, however, the scientific data on the co-combustion of hydrogen and natural gas in gas turbines in an industrial environment is sparse.
To fill in the knowledge gaps, a team of researchers co-fired hydrogen and conventional natural gas in an ENGIE-owned Siemens SGT-600 (Alstom legacy GT10B) 24 MW industrial gas turbine in Antwerp. Their results were revealed in the paper, “Demonstration of Natural Gas and Hydrogen Cocombustion in an Industrial Gas Turbine,” published in the April 2023 Journal of Engineering for Gas Turbines and Power.
“We carried out the experiment within the framework of climate change with the objective of decarbonizing gas turbines,” said Nicolas Jouret, a graduate student in applied mechanics and energy conversion at the Katholieke Universiteit Leuven in Belgium. “We started by carrying out a technological review of the possibilities of burning hydrogen, using information received from gas turbine manufacturers.”
Jouret worked with Hannes Laget and Luc Gooren of ENGIE Laborelec Brussels and Peter Griebel, Fabian Hampp, and Oliver Lammel of the Institute for Combustion Technology at the German Aerospace Center (DLR) in Stuttgart.
A two-step process
The research program carried some real risk. One of the biggest unknowns in designing the experiment was the risk of flashback, which can cause very serious damage to the burners. Other challenges were avoiding higher nitrogen oxides (NOx) emissions due to increase of local flame temperatures, supply and homogeneous mixing of hydrogen with natural gas, and other safety aspects regarding hydrogen fuel blends.
To limit the risks in this industrial gas turbine testing, a dual-step approach was taken.
ENGIE teamed up with the German Aerospace Center (DLR) to perform single-burner combustion tests in the high-pressure combustor rig at the DLR’s Institute of Combustion Technology in Stuttgart. The research team tested for the onset of flashback and other combustor characteristics with respect to burner wall temperatures, emissions, and combustion dynamics for base load and part load conditions, both for pure natural gas and various natural gas and hydrogen blends. For mixtures with less than 30 percent hydrogen by volume, only minor effects on flame position and flame shape and NOx emission were identified.
“No flashback was observed in the laboratory, even for very high hydrogen concentrations,” Jouret said. “The gas turbine tests were successful in the range we wanted to investigate and the turbine operated very stably.”
These test results were encouraging enough to move on to the second step, the exploration of hydrogen limits using a second-generation Siemens SGT-600 industrial gas turbine in Antwerp. To inject hydrogen into the industrial gas turbine, a hydrogen supply line was developed and installed next to the gas turbine. All tests were performed on the existing gas turbine hardware without any modification.
Operational tests at base and part load with hydrogen variation up to 25 percent by volume were monitored for gas composition, emissions, combustion dynamics, and operational parameters to evaluate the impact of hydrogen on turbine performance. Tests showed that the co-firing of up to 10 percent by volume hydrogen could be achieved with no adverse effects on the performance of the turbine.
The research program also found no observable flashback in the investigated parameter range, up to 50 percent hydrogen by volume; only minor influences on the flame position or heat release zone; and NOx emissions were only slightly affected. However, carbon monoxide emissions strongly decreased, especially for higher hydrogen concentrations.
The testing showed that hydrogen co-combustion with natural gas can be achieved safely.
“Today, gas grid operators are having ongoing discussions about adding up to 20 percent volume hydrogen in the natural gas grid,” Jouret said. “We have proven that the ENGIE unit is hydrogen-ready without any modifications to the gas turbine hardware and that the unit can be operated safely with these hydrogen contents, reducing its carbon footprint.”
Moving forward
This work has provided a detailed database to assess the hydrogen tolerance of existing gas turbines operating in the field. To the researchers’ knowledge, this is the first time that burning H2/NG blends up to 25 percent by volume has been demonstrated in a full gas turbine power plant operation without hardware changes to the lean pre-mixed combustor.
“The co-combustion of hydrogen with natural gas is of interest to many sectors that require a combustion process in their industrial process,” Jouret said. “Perhaps our most impressive result is that we showed existing burners can burn a greater quantity of hydrogen than what was initially thought, while respecting environmental standards. Up to 30 percent by volume should not be a problem, which is an important step in the transition to a less carbon-intensive world.”
Mark Crawford is a technology writer in Corrales, N.M.
