Turbine technology|


biodiesels, hydrotreated vegetable oil, fatty acid methyl esters (FAME), and Fischer-Tropsch diesel. Most of these fuels are already certified for use in gas turbines, eg, Siemens Energy’s SGT-800 can already run on 100% HVO.


(Cracked) ammonia


emissions and the need for more safety measures to eliminate the risk of ammonia exposure.


Ammonia can be easily liquefied and has a higher energy density than hydrogen, making it practical for storage and transport. However, ammonia combustion in gas turbines isn’t well advanced due to challenges such as high NOx


Cracked ammonia offers a promising path to overcoming certain ammonia combustion challenges by using hydrogen as a reactivity promoter. Siemens Energy’s SGT-800 can already co-fire using cracked ammonia, and fully cracked ammonia will likely emerge as the long-term preferred option for ammonia electrification. While site-specific techno- economic factors vary, countries like Germany may import hydrogen as ammonia, and major EU shipping terminals may be potential sites for centralised ammonia cracking and transport via a hydrogen pipeline network.


Methanol


Methanol is primarily a chemical industry feedstock, and it’s being increasingly sought out as sustainable bio-methanol or e-methanol from green/blue hydrogen and sustainable CO2


. It offers a much higher energy density than hydrogen. The CO2


can be derived from


direct air capture as well as diverse biomass and waste sources. It will become increasingly available to sectors like shipping, and is compatible with the existing infrastructure for storage and transport. With its considerable potential for direct gas turbine use, methanol applications range from base load power to backup for data centres and island grids.


Ethanol


Bioethanol is the most common biofuel. It’s produced from sugarcane or corn, but these first-generation sources aren’t considered


Renewable energy from grid


Green energy to grid


12 MWe @full load


Electrolyser Power-to-H2 Water Green H2 Compressor Storage


-to-power, as demonstrated by the HYFLEXPOWER project (source Siemens Energy)


Heat recovery


20 MWth @full load


SGT-400 (up to 100% H2 ) Natural gas


sustainable due to competition with food production. Second-generation bioethanol that’s made from waste biomass or biomass produced on land not suitable for food production avoids this issue. Ethanol demand is policy-driven for vehicle fuel blends, but with increasing electrification of transportation, its use in gas turbines may grow. However, e-methanol is simpler to synthesise and so it’s more likely to be used for gas turbine applications.


Dimethyl ether


Dimethyl ether (DME) is a clean, non-toxic synthetic gas that’s used as an aerosol propellant and in the chemical industry. It has the potential for gas turbine combustion due to its high cetane numbers and complete burn, which reduce emissions like NOx


and SOx .


However, its use in turbines may require fuel system modifications, and there are concerns about supply availability and safety due to gasification upon leakage. As methanol is often an intermediate compound in DME synthesis, it is usually more beneficial to use methanol directly and avoid the additional processing steps which only add additional costs and energy losses. Methanol is also much easier to handle, transport, and store. DME may,


Simplified schematic of exhaust gas recirculation (DCC = direct contact cooler) (source Siemens Energy)


Ambient air O2


: 21% vol. Max. 40% EGR Fuel


Mixed oxidant O2


> 14% vol.


Exhaust gas (40°C)


DCC


Exhaust gas (100°C–180°C)


HRSG


however, be a fuel of choice for locations where it is available in sufficient quantities and where its conversion to electricity makes sense.


Integrating carbon capture The integration of carbon capture with gas turbine power plants can be achieved via pre-combustion capture, oxyfuel firing, or post combustion capture (absorption and adsorption).


The relatively low CO2 concentrations in gas


turbine exhausts present a challenge for post combustion capture that may be addressed by exhaust gas recirculation and/or development of novel technologies.


As with the other decarbonisation pathways, techno-economic factors (eg, the plant efficiency penalty due to steam consumption in amine based post combustion capture (PCC)) will determine how widely carbon capture is adopted.


Siemens Energy is supporting the


development of carbon capture for gas turbines today by focusing on integration of the carbon capture plant with the gas turbine power plant and carbon dioxide compression. Mature amine solutions are currently ready for deployment and incentivisation schemes implemented by governments around the world are generating accelerated interest in the deployment of gas turbines with carbon capture.


Many companies are looking at the development of advanced carbon capture technologies, with improved amine processes, alternative solvents and solid sorbents seen as promising future technology steps.


Potential pathways


Exhaust gas (450°C–600°C)


CO2


: 3–5% vol. w/o EGR or > 8% vol. w. EGR


Decarbonisation strategies vary regionally, and the most economic and beneficial solutions are influenced by location, fuel prices, and infrastructure development. Diverse technical solutions and continued R&D, partnerships, and full supply-chain consideration are crucial for successful decarbonisation, with green hydrogen, ammonia, methanol, biofuels and carbon capture as potential pathways.


18 | September 2024| www.modernpowersystems.com


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