Hydrogen

Siemens Energy is on a mission: to provide the capability to burn 100% hydrogen across its full range of gas turbine offerings, by 2030, according to a commitment made in January 2019 (along with other members of EUTurbines, an association representing European turbine manufacturers).

The charts below show current hydrogen capabilities (vol-%) of Siemens gas turbines and some hydrogen milestones for the SGT-600, SGT-700 and SGT-800 (which employ similar DLE (premix) burner designs). They were presented at a Siemens hydrogen press briefing on 15 July, by Finspa°ng-based Jenny Larfeldt, senior gas turbine expert at Siemens Energy (and also adjunct professor at Chalmers University).

An important next step is scheduled for August 2020, at Finspa°ng, where an SGT-800 “sector test” is planned. An SGT-800 will be operated with five out of its 30 burners running on 75 vol-% hydrogen, with 40 ppm NOx at full load conditions.

Among the issues to be addressed when considering hydrogen as a fuel for gas turbines are: its flammability over a much wider range of fuel-to-air ratios than natural gas, requiring adaptation of ventilation and gas detection systems as well as fuel systems; lower ignition energy; and lower density than natural gas, although, fortunately, the Wobbe Index remains in what is normally considered the natural gas range, 37-49 MJ/Nm3, meaning that resizing of auxiliary systems, piping and valves, etc, can be avoided.

But for a gas turbine combustion system designer perhaps the key property of hydrogen is that it “burns fast”, said Prof Larfeldt, with a flame speed about 10 times higher than natural gas. This means that as the proportion of hydrogen in the fuel increases the combustion moves closer to the fuel mixture injector and the flame becomes more intense and compact. Measures, including adjustments to air and fuel distribution, are needed to avoid “flash-back” (backwards propagation of the flame, which can be sucked back into the burner causing damage).

The change in flame distribution also changes the heat load distribution in the combustor.

“This is something we need to design for in our turbines”, with the change in heat load distribution necessitating adaptation of combustor cooling schemes – a development activity greatly facilitated by the use of additive manufacturing techniques.

“Already ten years ago we were starting to map the capability of our standard industrial gas turbine burner to see what the response was when we started to introduce hydrogen”, noted Dr Larfeldt.

In 2012 a single burner in an SGT-700 (which has 18 burners) was successfully fed with 40 vol-% hydrogen and “encouraged by the good results”, single-burner SGT-700 testing was successfully carried out in 2014 up to 60 vol-% hydrogen, both test runs being conducted at Finspa°ng.

In 2017, in response to a customer request, full engine tests were carried out on an SGT-800 operating with 30 and 50 vol-% hydrogen (again at Finspa°ng), while at the same establishing what would be needed to maintain NOx emissions guarantees of 15 ppm and 25 ppm, respectively, employing the standard burners of that time.

In 2019, a single-burner SGT-800 test campaign was undertaken at the Siemens high pressure combustion test centre in Berlin, using burner technology developed with the help of additive manufacturing, which dramatically speeds up prototyping.

Operation at 100 vol-% hydrogen with 50 ppm NOx was demonstrated and the Flash-Back Out safety system was also successfully tested.

At the Berlin centre it is possible to achieve conditions (temperatures, pressures, air flows. etc) representative of those encountered across all the different Siemens gas turbine frames, said Dr Larfeldt, “and this is where we first successfully tested 100% hydrogen and also saw that at the same time we were able to maintain fairly low NOx emissions.” As long as the flash back can be controlled, low NOx is an inherent advantage of DLE (premix) burners because the flame temperature is controlled by the fuel/air mixing.

Meanwhile, back at Finspa°ng, hydrogen testing was progressing on the SGT-600 (which has 18 burners), in support of a cogeneration modernisation project being carried out by Brazilian company Braskem at its Sao Paulo petrochemical complex. For this project, Siemens is supplying two SGT-600 gas turbines to run on 60%-hydrogen residue gas, with commercial operation scheduled for 2021. In 2018, “bid ready” SGT-600 full load testing was carried out for the Braskem project at 60 vol-% hydrogen, while maintaining no more than 25 ppm NOx. Then, in 2019, the pre-delivery test for the two Braskem gas turbines verified “we could run on 60% hydrogen and guarantee 25 ppm NO ” and “also showed we had reliable operation with an ‘off-design’ level of 80 vol-% hydrogen.”

The two Braskem units will also employ the Flash-Back Out system, which produces a 5 second water spay if flash-back is detected, and aims to keep the gas turbine in continuous operation (a critical consideration in many industrial processes). Flash-back detection is well established in the Siemens fleet and has been used on all dual fuel gas turbines.

Assuming the August 75 vol-% test is successful, future plans for the SGT-800 envisage testing at higher hydrogen levels at Finspa°ng in 2022, followed by collaborative testing with a power plant owner/operator having access to H2.

The transport logistics of getting sufficient hydrogen to Finspa°ng are proving challenging, with an SGT-800 running on 100 vol-% hydrogen – which is the vision – needing some 4.5 t per hour, but a delivery of only 1.4 t being currently available on site for each test, amounting to just 20 minutes operation. So ”we are looking for active collaboration with people with hydrogen”, said Jenny Larfeldt.

In the case of the SGT-400 (eight DLE can combustors with radial swirl), an EU funded research project, HYFLEXPOWER, is anticipating running a machine located at a Smurfit Kappa CHP plant in France on up to 100% hydrogen by 2023 (see below).

A significant new hydrogen related development at Finspa°ng is the establishment of the Zero Emission Hydrogen Turbine Center, with funding from the Swedish Energy Agency and the EU, due to enter operation in 2021. The new test facility aims to be zero emissions and will include an electrolyser powered from turbine test runs and PV panels to produce hydrogen for use as turbine fuel.

“We are also very eager to collaborate with customers”’, said Dr Larfeldt. One example is a project being implemented with Go¨teborg Energi, which wants all district heating in Gothenburg to be produced from renewable sources by 2025.

As part of this effort a dual fuel burner, able to operate on liquid and gaseous green fuels (including hydrogen), is targeted for demonstration in one of the three SGT-800 turbines at the Rya CHP plant in 2024, once again making maximum use of additive manufacturing to accelerate prototyping.

The Rya project also has the potential to demonstrate how fossil free fuels, such as green hydrogen, can be used to provide grid ancillary services with very low emissions.

HYFLEXPOWER looks to a 100% hydrogen fuelled SGT-400 by 2023

An upgraded SGT-400 gas turbine running on 100% hydrogen by 2023 is a key objective of the recently launched HYFLEXPOWER project, funded by the European Commission under Horizon 2020, and being implemented by a consortium of Engie, Siemens, Centrax, Arttic, German Aerospace Center (DLR) and four European universities.

The consortium describes the project as “the world’s very first industrial-scale power-to-X-to-power demonstrator.” The aim is to demonstrate that hydrogen produced from renewable power can be stored and used to fuel a combined heat and power plant.

An existing 12 MWe CHP plant (operated by Engie) at Smurfit Kappa’s paper recycling facility in Saillat-sur-Vienne, France, is being modified for the project.

Engie will build the hydrogen production and storage facility, including the natural gas/hydrogen mixing station upstream
of the turbine. Siemens will supply the electrolyser and the gas turbine upgrade, while Centrax will modify the gas turbine package for hydrogen operation and install the upgraded turbine.

DLR together with University College London, University of Duisburg-Essen and Lund University will support the hydrogen turbine technology development, National Technical University of Athens will perform economic and environmental assessments and Arttic will support project management and communication.

The project’s total budget is around €15.2 million, with €10.5 million coming from the EU. The four-year project was officially launched on 1 May 2020, with contract finalisation and start of engineering development.