Periodic Reporting for period 3 - KEROGREEN (Production of Sustainable aircraft grade Kerosene from water and air powered by Renewable Electricity, through the splitting of CO2, syngas formation and Fischer-Tropsch synthesis)
Berichtszeitraum: 2020-10-01 bis 2022-09-30
The objective of KEROGREEN is to produce CO2 neutral jet-grade fuel, the kerosene being synthesised from air and water, powered by renewable electricity. KEROGREEN meets UN ICAO CORSIA emission reduction targets and the EU Flightpath 2050 environmental objectives, as this fuel contains no sulphur, produces no soot and emits less NOx. At a generic level, coupling the renewable power sector to the fuel and chemical sector, Power-to-X, creates long-term, large-scale energy storage capacity needed to balance the grid and to strengthen EU energy security.
The KEROGREEN approach is uniquely based on plasma-driven dissociation of air-captured CO2, oxygen separation by high temperature oxygen conducting membranes and advanced Fischer-Tropsch (FT) synthesis to yield kerosene. Synergy between plasma-activated species and novel perovskite electrodes of the oxygen separator is shown to raise CO productivity, a valuable intermediate product. High heat transfer FT technology results in process intensification, producing long chain hydrocarbons at extended catalyst life time. Hydrocracking (HC) upgrades the FT wax to sustainable aviation fuel (SAF) compatible with current aircraft technology.
KEROGREEN has delivered an integrated container-sized system able to produce up to 0.1 l/hr kerosene. Such container is envisioned to be close coupled to a remotely sited renewable electricity plant, like an off-shore wind turbine. Surplus electricity is used to drive the chemical synthesis of liquid fuel which is transported inshore, stored and distributed to users by conventional pipeline or shipping means, with no need to stretch vulnerable and costly electricity cables across the sea.
Individual elements of the process chain are of dissimilar technology at widely varying Technology Readiness Level (TRL). The project objective is TRL4 - Technology validated in lab. To date, all elements have reached TRL3 - Experimental proof of concept. All but one have reached TRL 4 or beyond, including the CO2-splitting plasma reactor, the CO purifier, the sorption-enhanced water-gas-shift (SE-WGS) reactor, the FT synthesis reactor and the HC kerosene optimiser. Upscaling the lab-scale oxygen separator to system level has turned out to be a challenge and has been deferred to post-KEROGREEN activity, the mitigation scenario duly implemented.
The KEROGREEN approach is uniquely based on plasma-driven dissociation of air-captured CO2, oxygen separation by high temperature oxygen conducting membranes and advanced Fischer-Tropsch (FT) synthesis to yield kerosene. Synergy between plasma-activated species and novel perovskite electrodes of the oxygen separator is shown to raise CO productivity, a valuable intermediate product. High heat transfer FT technology results in process intensification, producing long chain hydrocarbons at extended catalyst life time. Hydrocracking (HC) upgrades the FT wax to sustainable aviation fuel (SAF) compatible with current aircraft technology.
KEROGREEN has delivered an integrated container-sized system able to produce up to 0.1 l/hr kerosene. Such container is envisioned to be close coupled to a remotely sited renewable electricity plant, like an off-shore wind turbine. Surplus electricity is used to drive the chemical synthesis of liquid fuel which is transported inshore, stored and distributed to users by conventional pipeline or shipping means, with no need to stretch vulnerable and costly electricity cables across the sea.
Individual elements of the process chain are of dissimilar technology at widely varying Technology Readiness Level (TRL). The project objective is TRL4 - Technology validated in lab. To date, all elements have reached TRL3 - Experimental proof of concept. All but one have reached TRL 4 or beyond, including the CO2-splitting plasma reactor, the CO purifier, the sorption-enhanced water-gas-shift (SE-WGS) reactor, the FT synthesis reactor and the HC kerosene optimiser. Upscaling the lab-scale oxygen separator to system level has turned out to be a challenge and has been deferred to post-KEROGREEN activity, the mitigation scenario duly implemented.
Design and manufacture of a 6 kW/915 MHz plasmolysis unit has been completed. Commissioning tests defined the window of operation to achieve the KEROGREEN objective, including CO2 input flowrate 20 - 70 Nl/min at 100-300 mbar operating pressure, CO output flowrate tunable to 10 Nl/min, energy efficiency up to 0.12 kg CO/kWh.
Development of O2 gas separation is based on ceramic Solid Oxide Electrolyte Cells (SOEC) equipped with perovskite electrodes. High temperature SOECs that operate under CO2 plasma exposure do not exist. A range of novel perovskite materials were investigated relying on Density Functional Theory and (electro-) catalytic test. Underlying research on powder crystallite size and composition and on coating technologies provided information on cell manufacture. A benchtop plasma-SOEC reactor (0.1kW 13.5MHz) was developed exposing a 2 cm2 button cell to the afterglow of a CO2 plasma. Results show “TRL3 proof of concept” of the coupled CO2 plasma SOEC approach resulting in high Faradaic efficiency (>90%), 91% of oxygen removal and an 138% increase in CO yield. No cell degradation was observed after long-duration tests (>100hrs).
Integration of individual cells into a stack of cells has been contracted out to industry. Procurement consists of two Lab scale stacks differing in the customer specified plasma electrode material and one Full scale stack consisting of several stacks of cells with total active area of approx. 5600 cm2 meeting requirements on 5 Nl/min oxygen removal.
Tests of the Lab scale oxygen separator connected to the plasma CO2, CO, O2 gas stream showed significant CO to CO2 back reaction, required oxygen rich conditions as in fuel cell operation and required hydrogen feed to the oxygen electrode to avoid oxidation. Furthermore, the presence of CO2 deactivated the stack in a short period of time.
The CO purification module, working on the principle of Pressure Swing Adsorption, has been manufactured and tested reaching a CO yield of 78 % at 98 % purity, exceeding the TRL4 project target.
The SE-WGS removes CO2 from the WGS reaction in order to produce a high concentration syngas. It consists of six chambers working in concert to switch between adsorption, reaction and desorption, producing a continuous flow of syngas.
The FT reactor is based on micro-channel evaporation cooling technology which allows fast response to variable gas input, precise temperature control for optimum catalysis and high conversion reaching two orders of magnitude volumetric process intensification.
The HC unit is integrated with the FT reactor to maximise kerosene yield by recirculating the FT waxes into the HC reactor providing tailored product separation. The synthesis processing scheme has been supported and optimised by modelling.
Project results have been presented to the general public and to targeted audiences from science, industry and EU policy makers amounting to over 130 dissemination activities including production of promotional material, a project website, press and journal articles, scientific publications and participation in around 70 events. Two KEROGREEN international workshops, one winter school and a final public event were organised, well attended by stakeholders. An exploitation and business plan has been developed exploring and identifying routes to commercialisation of KEROGREEN technology.
Development of O2 gas separation is based on ceramic Solid Oxide Electrolyte Cells (SOEC) equipped with perovskite electrodes. High temperature SOECs that operate under CO2 plasma exposure do not exist. A range of novel perovskite materials were investigated relying on Density Functional Theory and (electro-) catalytic test. Underlying research on powder crystallite size and composition and on coating technologies provided information on cell manufacture. A benchtop plasma-SOEC reactor (0.1kW 13.5MHz) was developed exposing a 2 cm2 button cell to the afterglow of a CO2 plasma. Results show “TRL3 proof of concept” of the coupled CO2 plasma SOEC approach resulting in high Faradaic efficiency (>90%), 91% of oxygen removal and an 138% increase in CO yield. No cell degradation was observed after long-duration tests (>100hrs).
Integration of individual cells into a stack of cells has been contracted out to industry. Procurement consists of two Lab scale stacks differing in the customer specified plasma electrode material and one Full scale stack consisting of several stacks of cells with total active area of approx. 5600 cm2 meeting requirements on 5 Nl/min oxygen removal.
Tests of the Lab scale oxygen separator connected to the plasma CO2, CO, O2 gas stream showed significant CO to CO2 back reaction, required oxygen rich conditions as in fuel cell operation and required hydrogen feed to the oxygen electrode to avoid oxidation. Furthermore, the presence of CO2 deactivated the stack in a short period of time.
The CO purification module, working on the principle of Pressure Swing Adsorption, has been manufactured and tested reaching a CO yield of 78 % at 98 % purity, exceeding the TRL4 project target.
The SE-WGS removes CO2 from the WGS reaction in order to produce a high concentration syngas. It consists of six chambers working in concert to switch between adsorption, reaction and desorption, producing a continuous flow of syngas.
The FT reactor is based on micro-channel evaporation cooling technology which allows fast response to variable gas input, precise temperature control for optimum catalysis and high conversion reaching two orders of magnitude volumetric process intensification.
The HC unit is integrated with the FT reactor to maximise kerosene yield by recirculating the FT waxes into the HC reactor providing tailored product separation. The synthesis processing scheme has been supported and optimised by modelling.
Project results have been presented to the general public and to targeted audiences from science, industry and EU policy makers amounting to over 130 dissemination activities including production of promotional material, a project website, press and journal articles, scientific publications and participation in around 70 events. Two KEROGREEN international workshops, one winter school and a final public event were organised, well attended by stakeholders. An exploitation and business plan has been developed exploring and identifying routes to commercialisation of KEROGREEN technology.
Individual units have been integrated in the container-sized KEROGREEN system, fully instrumented with control and data acquisition. The test results of the Oxygen separator necessitated decoupling this element from the process chain and replacing the input of the FT/HC unit by an external source of syngas. Commissioning and operation of the integrated kerosene synthesis unit resulted in a production of 0.11 l/h liquid product reaching the TRL4/5 project objective.
Life Cycle Impact Assessment including Environmental, Economic and Social Sustainability assessment together with an Acceptability matrix of KEROGREEN and competing technologies show favourable results for off-shore wind at 90% availability. Chemical pathway analysis shows that thermal and material integration between the individual units is key to maximising energy and carbon efficiency. Recirculation of unreacted CO2 and product gases is expected to reach over 90% conversion of air captured CO2 to liquid fuels in a fully integrated KEROGREEN process.
Current analysis indicates that the KEROGREEN approach has significant market impact provided KEROGREEN energy and conversion efficiency go up whilst being accompanied by CO2 emission regulation and taxation to reach price equity with fossil-based jet fuel.
Life Cycle Impact Assessment including Environmental, Economic and Social Sustainability assessment together with an Acceptability matrix of KEROGREEN and competing technologies show favourable results for off-shore wind at 90% availability. Chemical pathway analysis shows that thermal and material integration between the individual units is key to maximising energy and carbon efficiency. Recirculation of unreacted CO2 and product gases is expected to reach over 90% conversion of air captured CO2 to liquid fuels in a fully integrated KEROGREEN process.
Current analysis indicates that the KEROGREEN approach has significant market impact provided KEROGREEN energy and conversion efficiency go up whilst being accompanied by CO2 emission regulation and taxation to reach price equity with fossil-based jet fuel.