Overview
Decentralized hydrogen production at refuelling stations has great potential to accelerate market introduction of hydrogen-powered vehicles. Based on the outcome of the previous NEMESIS project under FP6 the overall objective of the proposed NEMESIS 2+ project is the development of a small-scale hydrogen generation prototype capable of producing 50 standard cubic metres of hydrogen per hour from diesel and biodiesel at refuelling stations. Reduction of hydrogen production costs and an increase of reliability and efficiency of the hydrogen generation system will be the major objectives.
Special emphasis will be placed on liquid desulphurisation prior to the catalytic conversion step. Based on the promising results from the NEMESIS project, a desulphurisation module based on liquid adsorption for continuous operation will be built and tested with fossil diesel, biodiesel and biodiesel blends. Thereby severe problems relating to catalyst deactivation can be avoided or at least minimized. This will be supplemented by the development of sulphur-tolerant reforming and water gas shift catalysts and the development of catalyst regeneration strategies. The liquid desulphurisation module will be connected to a reformer module based on a modified steam reforming technology owned by HyGear. By a subsequent water gas shift stage and a pressure swing adsorption unit a hydrogen purity of 5.0 (99.999 %) is achieved. In order to be able to run on liquid fuels as well as on off-gas from the hydrogen purification unit, a dedicated dual fuel burner will be developed within NEMESIS2+. Once the prototype modules (desulphurisation module, multi-fuel catalyst, reformer module) are integrated into the prototype unit the system will be tested for at least 1000 hours. Work will be completed by a techno-economic evaluation of the prototype hydrogen generation system (Cost analysis, Study on integration into refuelling stations).
Funding
Results
Final Report Summary - NEMESIS2+ (New Method for Superior Integrated Hydrogen Generation System 2+)
Executive Summary:On-site hydrogen production at refuelling stations from liquid fuels offers a number of advantages like high energy density and infrastructure already being available. Besides, it is economically advantageous in areas where hydrogen cannot be cost-effectively...
Executive Summary:
On-site hydrogen production at refuelling stations from liquid fuels offers a number of advantages like high energy density and infrastructure already being available. Besides, it is economically advantageous in areas where hydrogen cannot be cost-effectively supplied by a central production plant.
Within the 3-year project NEMESIS2+ (New Method for Superior Integrated Hydrogen Generation System) a small-scale hydrogen generator capable of producing 50 m3·h-¹ hydrogen (purity: 5.0) from biodiesel and diesel has been developed.
With the envisaged process concept, a theoretical system efficiency (based on the lower heating value of hydrogen related to the lower heating value of liquid fuel) of 70 % can be achieved. Hydrogen production costs < 5 €/kg were targeted.
Apart from integrating such a system into existing refuelling stations, the NEMESIS2+ hydrogen generator is potentially applicable to industrial applications, in particular to the steel and glass industry.
Project Context and Objectives:
Currently, large-scale methane steam reforming is the prevailing technology for hydrogen production. In the long-term perspective it is expected that hydrogen produced from electrolysis of water using surplus wind energy will become increasingly important. In the meantime, with the EU Renewable Energy Directive requiring member states to obtain 10 per cent of the fuel used for transport from renewable sources by the year 2020, on-site hydrogen production at refueling stations from liquid biofuels offers a promising way forward. Such technology has not yet been developed to a commercially available product fulfilling market requirements in terms of cost and efficiency.
Decentralized hydrogen production at refueling stations is economically advantageous in areas where the logistic costs for hydrogen are high. Generating hydrogen from already available feedstock at the fueling sites offers a low cost production potential. Apart from integrating such a hydrogen generation system into existing refueling stations, the NEMESIS2+ concept is potentially applicable for annealing applications, in particular the steel industry and the production of high quality flat glass.
Within the previous NEMESIS project under FP6 the technical feasibility of producing 5 Nm3 H2 per hour from diesel with a proof-of-principle prototype system has been shown. In order to make the next step towards a commercialisation of such an on-site hydrogen generation system it was scaled up from 5 to 50 Nm3/h using a modified tubular reforming technology owned by HyGear. A “one-reformer”-concept (without pre-reforming) is applied aiming at a high degree of system compactness and reduced investment costs.
NEMESIS2+ focuses on liquid fuels only. Using liquid fuels in combination with steam reforming technology at elevated pressures (12 bar) results in a significantly reduced system size and lower hydrogen production costs. The reformer section is followed by an integrated water gas shift stage, thus increasing the overall hydrogen efficiency. The system is equipped with a dual-fuel burner which can be operated on off-gas from the hydrogen conditioning module as well as on liquid fuels. Proper heat integration of the overall system is achieved by applying pinch analysis.
One of the main challenges of hydrogen production from liquid fuels is catalyst deactivation due to sulphur poisoning and coking. Therefore extensive experimental work has been carried out in order to find optimum operating conditions in terms of pressure, temperature and steam-to-carbon ratio.
Special emphasis was put on the development of an innovative concept for liquid desulphurization (based on liquid phase adsorption) prior to the catalytic conversion step. Besides, the sulphur tolerance as well as the resistance towards coking of the fuel processing catalysts was improved and regeneration strategies of the spent catalysts have been investigated in detail.
Experimental work and hardware development are supplemented by system modeling with Aspen Plus which provides a proper tool for analysis of various process configurations and operating regimes. In order to proof long-term stability of the NEMESIS2+ hydrogen generation system a long-term test for more than 1000 hours has been performed using different liquid fuels including diesel and biodiesel.
Project Results:
- Successful development of a pre-commercial 50 Nm3/h hydrogen generation system based on liquid fuels (diesel and biodiesel)
- H2 purity: 5.0, measured system efficiency (based on LHV): 48 %. Obviously, the measured H2 efficiency is significantly lower than the theoretical achievable H2 efficiency (68 %) of the NEMESIS2+ system. The discrepancy is mainly caused by:
• High steam-to-carbon ratio (necessary in order to prevent coke formation)
• Addition of air (“oxygen assisted reforming”) in order to prevent coke formation
• Low PSA-efficiency (not optimized for high pressures)
• Insufficient heat integration (no separate heat exchanger for burner air foreseen)
• Heat transfer limitations of the prototype system
• Uneven temperature distribution in the reformer tubes
- Techno-economic analysis of the NEMESIS2+ system reveals hydrogen production costs of 5.8 € per kg H2 for feedstock biodiesel
- Stable long-term operation (> 1000 hours) of prototype unit has been shown
- Successful development of an innovative diesel desulphurization concept based on liquid fuel adsorption
- Successful development of improved reforming and water gas shift catalyst formulations
- Potential impact and use: The NEMESIS2+ system can be integrated into existing refuelling stations and is applicable to industrial applications (steel and glass industry).
Potential Impact:
NEMESIS2+ is the first project to show successful steam reforming of biodiesel and diesel on a pre-commercial level. The results have been published on conferences, in the popular press and in peer-reviewed journals:
Article in the international Innovation Magazin (including an interview with the project coordinator):
http://www.nemesisproject.eu/fileadmin/Dateien/PDF/International_Innovation_Energy_Report.pdf
Press release “Gren Car Congress”:
http://www.greencarcongress.com/2015/09/20150902-nemesis.html
Conferences:
13th Panhellenic Symposium in Catalysis, 05/2013, Athens, Greece
IV Iberian Symposium on Hydrogen, Fuel Cells and Advanced Batteries, 06/2013, Estoril, Portugal
8th Mediterranean Combustion Symposium, Izmir, Turkey
4th European PEFC & H2 Forum, 07/2013, Lucerne, Switzerland
Fuel Cells 2014 Science & Technology, 04/2014, Amsterdam, The Netherlands
5th European PEFC & H2 Forum, 06/2015, Lucerne, Switzerland
List of Websites:
www.nemesis-project.eu
Contact details: Stefan Martin, German Aerospace Center – DLR e.V, Pfaffenwaldring 38-40, 70569 Stuttgart, Germany, Tel: +49 711 6862 682, E-mail: stefan.martin@dlr.de